Liposomes and Cancer Therapy

Sara Branson
3/8/07
FYS
Liposomes: Packaging the Future of Cancer Treatments
Accounting for nearly one quarter of all deaths in the United States, cancer is a looming threat to people across the world. However, thanks to continued research in the development of more effective cancer fighting treatments, the death rates of cancer victims have significantly decreased from 1950, to present. Fighting cancer relies on three main technologies: chemotherapy, surgery, and radiation. Chemotherapy works via the transfer of cytotoxic drugs to specific locations in the body. The transfer must occur without interaction with healthy cells as the drugs circulate in the bloodstream. In addition, the drug must avoid destruction by the immune system, which recruits phagocytes such as macrophages to destroy foreign substances in the bloods stream. Nanotech biomimetics offers a wide range of utilities to overcome these complications by taking ideas from nature and incorporating them into technology. Liposomes are natural packaging devices flowing through the bloodstream that have been harnessed as drug dispensers for cancer treatments. Its design as well as functional capabilities allow it to deliver cancer treatments to target areas without harming healthy cells and without triggering the immune system.
Liposomes were discovered in 1961, by Alec Bangham at Cambridge University and were first used as drug delivery systems 30 years later (Tianshun). The structure of the liposome enables it to increase the potency while at the same time reducing the toxicity of the drugs it carries. Liposomes exhibit self organization that is triggered when certain phospholipids are exposed to an aqueous environment and utilize the hydrophobic effect to form a spherical lipid bilayer with the hydrophilic phospholipid heads facing out. The aqueous solution that is trapped inside the bilayer provides a carrying space for drugs that is sequestered from the aqueous outer environment. The formed vesicle may range in size from 50 to 200 nm in diameter and may be encased by one layer of phospholipids such as in a unilamellar liposome, or may have several layers that resemble an onion in a multilamellar liposome (Lian).
Although the synthesis of liposomes appears simplistic, serious complications are yet to be resolved with the development of a low cost method of mass production. The success of liposomes as a cheap medical device depends upon the formation of liposomes with adequate drug entrapment capability, appropriate size, relative stability, and drug release capability. Scientists use sources of energy such as sound and heat to agitate phospholipids in an aqueous solution into vesicle form, but they are unable to control the size and structure of the final product. The use of energy stimulated vesicle formation risks denaturing the drugs that are in the aqueous solution that will be enclosed inside the liposome. One of the main complications with liposome use in the human body is that one of the first steps in vesicle formation is to dissolve the lipids in a volatile organic solvent such as methanol. These solvents are often toxic and can affect the inner cargo, destabilize the lipid membrane, or remain as Organic Volatile Impurities (OVI’s) in the lipid membrane where they will later intoxicate healthy cells in the body (Mozafari).
In the medical world, drug companies utilize liposomes as an effective means of drug delivery. Water soluble drugs, including cancer drugs, are inserted in the aqueous compartment inside the phospholipid outer membrane. The liposomes are then introduced into the bloodstream, and the hydrophobicity of the outer bilayer keeps the drugs separated from the blood until the liposomes reach the targeted cells. This process is especially adept for cancer treatments because the phospholipid bilayer keeps toxic drugs from affecting healthy cells and can be modified to “target” cells like macrophages and tumor cells.
In order for drugs to be transferred into a cell, the liposome must interact with the target cell. Interaction occurs through several methods. The liposome may simply bump into the target cell, forming a weak bond with the cell membrane that allows drugs to diffuse directly into the cytoplasm of the cell. Other cells engulf the liposomes with the cell membrane through endocytosis. Once inside, the liposome fuses with a lysosome that contains phospholipases that degrade the liposome and release the drugs. Ligands called opsins are often appended to liposomes and instigate endocytosis by directing the liposome to the target cell. In addition, alteration of the pH inside the water compartment of the liposome creates a charge on the dissolved drug. Once the liposome is engulfed, the liposome will fuse with the organelle encasement and release the drug particles into the cytoplasm (Gregoriadis).
Cancer therapy utilizes specific characteristics of tumor cells in the transfer of cytotoxic drugs from the liposome to the target cells. Healthy blood vessels have an endothelial wall with tightly packed endothelial cells that prevent large molecules in the blood from leaking out of the vessel. The epithelial walls of vessels in tumor sites exhibit EPR, or enhanced permeability and Retention. Due to gaps in the epithelial wall, liposomes that are 400 nm or less can leak into the tumors. Tumors and cancerous lesions are therefore prime targets for liposome drug administration.
The main targets of cancer fighting drugs are TAMS, or tumor associated macrophages. Macrophages are cells in the immune system that originate from white blood cells called monocytes. They function in the immune system as phagocytes, meaning they engulf dangerous and potentially harmful material inside the cell such as pathogens. Instead of aiding in immunity like normal macrophages, TAMS produce chemokines and cytokines that promote tumor growth and metastasis. Scientists hypothesized that they could use liposomes to transfer a cytotoxic drug to the TAMS, which would in turn stop the progression of the tumor.
Consequently, the cytotoxic drug of choice was bisphosphonate clodronate, or Clodrolip. Encapsulated into unilamellar liposomes, this drug is commonly used for its ability to destroy TAMS and therefore cease the production of chemokines and cytokines. Tests performed on mice showed that the liposome administered Clodrolip inhibited tumor growth in 75% to 92% of the cases. Reduction of growth rate of tumor was significant up to nine days after treatment. Clodrolip is one example of an effective drug transferred by liposomes that has can inhibit hard tumor growth and metastasis.
Another liposome-packaged cancer treatment is NOAC. It is cheaply synthesized in lyophilized, or freeze dried liposome form and has high proprietary support for research. The lyophilized package is mass produced in highly purified form in four steps, using the cheap ribonucleotide uradine (“Liposomes: general properties). Through liposome delivery, NOAC has been shown to inhibit growth in breast, prostate, and lung tumors as well as fight leukemia. Research on freshly biopsized cancer cells in ovarian and mammary carcinomas showed NOAC to by highly cytotoxic to the tumor cells. It also showed success in inhibiting growth in melanoma and tumors that exhibited resistance to multiple drugs. Scientists tested NOAC on freshly biopsized human tumors at concentrations from 10 to 100 micromolar. At these concentrations mammary, lung, and ovarian carcinomas as well as non-Hodgkin lymphomas were highly inhibited (Schwendener). Liposomes play an active role in the administration of NOAC, as well as other notable cancer fighting drugs on the market such as Doxorubicin (Doxil) and Daunorubicin (Daunoxome).
Finally, scientists optimize the performance of liposomes through the addition of anti-tumor antibodies to the outer membrane of the liposome, creating what are known as immunoliposomes. Immunoliposomes target the tumor cells and make drug transfer more efficient. In addition, immunoliposomes can be sterically stabilized, meaning they are less likely to be filtered out of the bloodstream by the immune system and are able to circulate for a longer time. This is accomplished through the attachment of hydrophilic polymers or glycolipids to the liposome membrane. The modified liposomes act like targets that fit into receptors on target cells (“Liposomes: general properties”). The added target fragments do not increase the effect of the drug, but allow the drug to reach the target cells faster and circulate longer.
A special case study was performed by scientists on the effects of attaching single chain antibody fragments to liposomes containing cancer fighting drugs. They linked the antibody fragments to liposomes and radioactively labeled them so they could monitor their locations through fluorescence. A control group containing unmodified liposomes and the experimental group of modified liposomes were introduced into the bloodstream of tumor stricken rats at the same time. Two hours after injection, scientists found that the modified liposomes accumulated in tumors in concentrations two to three times that of the unmodified liposomes. However, after an extended period of time, the concentrations evened out. This proved that attaching “target” fragments to liposomes expedited the treatment by targeting the tumor cells. As expected, the drugs inhibited tumor growth in the rats. Overall, the experiment proved the efficiency of drug delivery with target lipsomes versus that of unmodified liposomes.
Liposomes are cheap, effective means of drug transportation in the medical field. They are the key to cancer therapy and the delivery of cytotoxic drugs that would otherwise ravage healthy cells. The intricate packaging system, harnessed from the ideas of nanotech biomimetics, is now the hopeful future of cancer research. Liposomes are simply a nano-scale machine harnessed within the human body to manipulate the placement of drugs that may one day defeat the onslaught of cancer.

ADDL Paper

Ashley Edwards

FYS Molecular Machines

ADDLs

Amyloid beta-derived diffusible ligands, ADDLs, bind in groups to neurons in the brain and are thought to cause Alzheimer’s disease. If ADDLs could be stopped from binding to the neurons, then the progression of Alzheimer’s disease could possibly be slowed down or even stopped completely. Acumen, a pharmaceuticals company, has already begun research to try and determine just how ADDLs can be stopped from making damaging clusters in the brain. Since aptamers can be selected to bind to certain things, if they could be selected to bind to the neurons and proteins that ADDLs bind to, then they would be very effective at helping stop the spread of Alzheimer’s in the brain.

Merck, a company that has already entered into a contract with Archemix, the leading company in aptamer research, has promised 48 million dollars for research into ADDLs and will give another 48 million dollars if a vaccine is developed. Merck and Acumen, the leading company in ADDL research, have entered into a contract where Merck will have exclusive rights to Acumen’s ADDL technology. Acumen is working on an assembly blocker and a binding inhibitor to stop the ADDL from initiating Alzheimer’s disease. The assembly blocker would work to stop the production of the oligomers, so that the ADDL would never be able to form. As this is a protein-protein interaction, it would be very difficult to target, but aptamers again look like a promising choice as a target molecule. The binding inhibitors would prohibit the ADDLs from binding to the neurons. This would work by either having a molecule bind to the ADDL where it would bind to the neuron, or having a molecule bind to the neuron. Again, aptamers might prove useful as a target molecule for either of these options. Acumen has not discussed using aptamers in either of their projects, but that does not mean that it isn’t a viable option. Acumen has discussed their selection process for molecules that might potentially bind to the ADDLs, but they have not yet released what molecules they are using in the selection process. Similar to SELEX, their selection process consists of placing a large quantity of small molecules into solutions with different ADDLs to determine whether or not they bind. They also test them in vitro to make sure the molecules would not be potentially toxic. Acumen would also then test whether or not those ADDLs would bind to the neurons or not, to make sure that the molecule was binding in the correct place. They have not yet released their plans for the selection of molecules to bind to the receptor sites on the neurons.

Both Acumen and Merck seem to be at the forefront of medical technology, and if successful, could make Alzheimer’s disease obsolete in a few years. Merck has seen some hardships in the past few years, with a withdrawal of Vioxx, an arthritis painkiller, and multiple lawsuits that claimed Merck did not properly warn the public about the risk of heart attack as a side effect of Vioxx. As a result, their stock went down starting around October of 2003, and has never fully recovered, although it is well on its way to surpassing where it was before the crash. Both Acumen and Merck would be excellent companies to invest in because a cure for Alzheimer’s disease would have profound effects on society and would generate a lot of revenue. Merck seems to be very involved in other risky, high-tech, medicine research that could pay off big in the next ten years or so. Archemix, the aptamer research company, has also entered into a contract with Merck. The main focus of their agreement is research into targeting cancerous cells using aptamers and if this is successful, then obviously both Merck and Archemix will begin making millions. All three of these companies would be great investments, because although risky, they have enormous pay-offs if successful. These new technologies will most likely provide the basis by which almost all diseases will be treated within the next ten to twenty years, and getting aboard now would be wise. Before investing, however, it is always smart to look at what exactly the companies are working on.

ADDLs are sticky, insoluble proteins that can clump together in messy groups in the brain and cause large build-ups of sticky fibers that attach themselves to neurons. Amyloid beta is a peptide made up of amino acids that forms after sequential cleavage of the amyloid precursor protein (APP) by the β- and γ-secretases. APP is a transmembrane glycoprotein, which means it is made up of a protein and a carbohydrate. The amyloid beta protein can then go through proteolytic processing, which would cause the digestion of proteins by enzymes. The exact proteolytic processes that cause ADDL to form are most likely the mutation of Ab peptides that have 40 peptides into ones with 42 peptides. This mutated form can then bind to neurons and cause Alzheimer’s and occasionally the death of the neuron. By attaching to the neuron, the ADDLs disrupt the normal signaling and cause the memory problems and dementia in Alzheimer’s disease.

The tau protein, which is a microtubule-associated protein normally found in the brain, has also been thought of as a cause of Alzheimer’s. Like ADDLs, it is found in high concentrations in the brain of patients with Alzheimer’s because it occasionally goes through hyperphosphorylation that causes large groups of tangled tau proteins and damages neurons. However, Jan Naslund, Ph.D., from Rockefeller University in New York, has done research on the brain tissue of many patients and she argues that ADDLs are most likely involved in the very early onsets of Alzheimer’s disease and might be the cause of the hyperphosphorylation of the tau proteins. The tau protein tangles then bind to the neurons, much like the clumps of ADDLs do, and further disrupt the signaling and therefore speed up the process of memory damage.

ADDLs are thought to interfere with long-term potentiation as an effect of binding to the neurons. Long-term potentiation is involved in spatial memory and is essential to learning. The ADDLs are also most likely to affect the hippocampus, and therefore affect the spatial navigation. Because the ADDLs affect these two things, researchers believe that they are the cause of synaptic memory formation loss and eventually lead to the dementia in Alzheimer’s patients. High concentrations of ADDLs have also been tied to the destruction of nerve cells that never regenerate, causing the slow deterioration. Below is a figure depicting the amyloid beta clumps that interfere with the neuron activity. If the clump grows large enough, it can cause the death of the nerve cells. The oligomers are also shown causing damage to a neuron, and those oligomers would most likely eventually turn into a clump of amyloid beta which would further damage the neurons. A clump of tau proteins is also shown in this diagram.

In order to stop the amyloid beta from forming ADDL, many solutions have been proposed. β- or γ-secretase inhibitors would stop the cleavage of APP and therefore would stop the production of amyloid beta and its mutations. Acumen is also working on inhibiting the production of oligomers so that the amyloid beta clumps would never form. Aptamers could possibly be selected to bind to whatever it is that ADDLs bind to, but at this point it is unclear if there is a specific site they bind to on the neurons, or if large clumps just happen to form sporadically. An immune attack on the ADDLs has been discussed, and since aptamers are also used as escorts, they could carry ADDL destroyers and could be selected to bind to the ADDL fibers.

ADDLs are almost universally agreed upon by scientists to play some role in the development of Alzheimer’s disease. Although there is dispute about whether the tau protein plays a larger role than the ADDLs, hopefully the scientists at Northwestern University and in Acumen are correct about ADDLs triggering the tau proteins. With the research of Acumen and the support of Merck, Alzheimer’s might become a thing of the past, and if you join now, you might be able to reap the economic benefits.

Works Cited

"Acumen Pharmeceuticals." 2006. 6 Mar. 2007 .

"ADDL Research Provides Vaccine Hope." About.Com. 29 Sept. 2006. 7 Mar. 2007 .

"Amyloid Beta." Wikipedia. 8 Feb. 2007. 5 Mar. 2007 .

"Amyloid Beta-Peptide Levels Associated with Early Dementia." 21 Mar. 2000. Doctor's Guide Publishing Limited. 5 Mar. 2007 .

"Amyloid Beta: a Stealth Protein That Destroys Thoughts and Memories in Alzheimer’s Disease." 2007. The J. David Gladstone Institutes. 5 Mar. 2007 .

Klein, William L. "Molecular Basis of Alzheimer's Disease; Apoptosis; Signal Transduction in Brain Development and Plasticity." 5 Oct. 2006. Northwestern University. 5 Mar. 2007 .

Smith, Aaron. "Jury: Merck Negligent." CNN Money. 22 Aug. 2005. 24 Mar. 2007 .

"Toxic Protein That Interferes with Brain Signals May Trigger Onset of Alzheimer's Disease." Science Daily. 28 May 1998. 5 Mar. 2007 .

RAG Proteins

Kyle Cubin
3-26-07
Paper #2
Final Draft

The RAG Proteins: Ensuring Antibody Diversity

The ability of human immune cells to identify infected cells as harmful is critical to the immune system. Each different kind of pathogen, or infected cell, has its own unique signature that defines it as a danger to the human body and if it goes unrecognized by the lymphocytes it can kill the body. Because of the relative inability of the immune system to generally recognize harm and kill it efficiently, there must be an individual mechanism for identifying the specific threat and eliminating it effectively. It is the job of the antigen receptors on specific lymphocytes to recognize the antigen, or the distinguishing surface protein of pathogens, the only problem is the need for a specific antigen receptor for each antigen. The antigen receptor of the lymphocyte is guaranteed to be able to recognize nearly all antigens because of a process that occurs during DNA replication called V(D)J recombination. This process would not be possible without the RAG, Recombination Activating Genes, proteins that make sure the proper parts of the DNA are replicated. The RAG proteins are the essential machines of V(D)J recombination and make the human immune system as effective as it is.
The antigen receptor of immune cells is the critical part of the immune system that allows it to recognize nearly all threats that enter the body. Once a pathogen enters the body, it should hopefully be recognized by a lymphocyte so it can be destroyed before proliferation. The issue with this is that there is a specific lymphocyte that has the antigen receptor for the unique antigen and an immune response will ensue only if it comes into contact with that specific lymphocyte. Fortunately the immune system has an efficient way of presenting potential pathogens to all lymphocytes so the pathogen can be recognized. However, if the lymphocytes didn't undergo the process of V(D)J recombination during the cells DNA replication the diversity of the antigen receptors would not be great enough to recognize all viable threats.
The antigen receptors of lymphocytes consist of heavy and light chains with both constant and variable regions. These regions are encoded for in the DNA by three different genes; the heavy gene, plus the light chains kappa and lambda. The heavy chain gene has segments that fall into three categories, V, D, and J, while the light chain only uses V and J. In the light chain there are 200 possible kappa gene segments and 124 lambda gene segments; one of these light chains will pair with a heavy change variation. The heavy chain variation comes from there being 51 different possible V gene segments, 25 possible D segments, and 6 possible J segments. There are then nine constant regions that bind with the variable complex composed of one of each V, D, and J segments. All of the different gene segments that could be used to produce the antigen receptor create a diversity of almost 2.5 × 107 possible combinations. The mechanisms involved in making sure V(D)J recombination occurs properly by ensuring that only one of each gene segment is presented includes the RAG proteins.
The most important components of V(D)J recombination are the Recombination Signal Sequences (RSS) and the Recombination Activating Genes (RAG). The RSS appear in the ends of the DNA segments that encode for the various regions of the antigen receptor. These regions of the DNA are recognized by the RAG proteins that then cut the DNA at these points forming a double-stranded break. This double-stranded break is repaired through normal processes, and the cut ends come together to form the DNA that will code for the variable region in the antigen receptor. In the heavy chain, the DJ segments combine and then the complex combines with a V segment, while in light chains the V segment just combines with a J segment.
The RAG proteins, which are RAG-1 and RAG-2, are the mechanisms of V(D)J recombinase that are specific to lymphocyte development. Every species that undergoes V(D)J recombination has the RAG proteins. The RAG proteins function in the development of antigen receptors as follows. First they recognize and align the Recombination Signal Sequences, and it is RAG-1 job specifically to do so. The RAG complex then makes two double-stranded breaks at the 5’ ends of the RSS. The free 3’ group will then create a hairpin structure out of the DNA by attaching itself to the phosphodiester bond on the other strand. It is the job of the RAG complex to hold this new DNA structure together. RAG-1 and RAG-2 then create a single stranded break in the hairpin structure allowing the final result of the recombination of the V, D, and J segments of DNA.
The way RAG proteins work is directly related to their structure. It is known that RAG-1 is responsible for recognizing and binding to the RSS, and it is able to “recruit” the site to bind to using the nonamer-binding-domain (NBD) the RAG protein has. The nonamer is the anchor point for the anchor point for the binding of RAG and RSS complexes. After the RAG protein is anchored to the RSS, the second step of “stabilization” occurs in the presence of RAG-2 which makes the heptamer of the now combined complex available for adding an additional stabilizing site for the interaction. This machine can be compared to a portable saw because it goes right to where it needs to be to perform its function and then cuts through the strands of the DNA. The RAG proteins could also be compared to a vice because after they split the DNA they hold the newly freed end in place until it reconnects with the DNA at a different location, which the proteins lead the end of the DNA to where it is supposed to be like a shepherd.
The RAG proteins have been proven to be essential to a healthy immune system because of the detrimental effects of having a lack of them. Severe Combined Immune Deficiency (SCID) has been proven to be an effect of a lack of RAG proteins. SCID is characterized by the absence of mature B and T lymphocytes necessary for the immune system to function. Mutations in the RAG-1/RAG-2 proteins also result in a condition known as Omenn Syndrome. This is an autosomal recessive form of SCID that has the same effect of being unable to fight infections because of no functioning white blood cells being able to do the job.
In the end it is apparent that the RAG proteins are crucial to the well being of any human. Without the RAG proteins regulating the V(D)J recombination process the immune system would not have mature, diverse lymphocytes available to fight off infection. Without the “portable saw” and “vice-grip” of the RAG proteins the resulting effect would be devastating diseases such as SCID and Omenn Syndrome which significantly lower a person’s quality of life. Without the RAG proteins, human life would not be possible.



Works Cited
“Antigen Receptor Diversity”. http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/AgReceptorDiversity.html#V(D)J_Joining. 9 March 2006.

Posey, Jennifer E, Vicky L Brandt, David B Roth. “Paradigm switching in the germinal center”. Nature Immunology. 2004. 476-477.

Swanson, Patrick C. “Fine Structure and Activity of Discrete RAG-HMG Complexes on V(D)J Recombination Signals”. Molecular Cell Biology. March 2002. 1340-1351.

“RAG-1 and RAG-2”.
http://www.bio.davidson.edu/Courses/Immunology/Students/Spring2003/Beaghan/mfip.html. Davidson College. 2003.

Cancer and Immunotoxins

Mike Epstein

Professor Jed Macosko

Of Molecules and Machines

March 27, 2007

Cancer and Immunotoxins

Cancer is a lethal disease that kills indiscriminately. In addition to claiming hundreds of thousands of American lives each year, cancer also kills millions of impoverished people annually. In 2002 cancer took the lives of 6.7 million people globally. The disease’s future impact on humanity looks even grimmer. It is estimated that in the year 2020, cancer will claim 10.1 million lives. [1]

The developing world contributes greatly to this death toll, considering that eighty-five percent of the global population lives in developing countries. Compared to developed countries, developing countries are greatly lacking in the vital resources needed to treat cancer. Radiotherapy is a common treatment for cancerous tumors; however, developing countries contain only one third of the world’s radiotherapy facilities. Fifteen African states and several Asian states lack even one radiotherapy machine. Ethiopia has one machine for its sixty million citizens while developed states average one machine for every 250,000 people. [2]

It is evident that the world needs a new solution for treating cancer. However in finding a solution, it is important that one understands how cancer works and why it is so deadly.

The term cancer actually refers to over one hundred separate diseases. These diseases are caused by a variety of factors. For instance, certain viruses have been linked to an onset of cancer. These viruses include the human-papillomavirus, which causes genital warts, and the Epstein-Barr virus, which causes mononucleosis. Diseases like AIDS that affect the immune system also can lead to various cancers. [3]

Certain substances called carcinogens increase the risk of getting cancer. Carcinogens like arsenic, asbestos and nickel can cause lung cancer. Tobacco is a common carcinogen which when used results in the development of various cancers, depending upon how it is ingested. Alcohol has been linked to oral cancer, and certain foods have been found to result in cancer. [4]

Furthermore, chromosomal abnormalities can contribute to cancer. Chromosomes are located within the nucleus of a cell, and carry the cell’s genetic information. When chromosomes are defective, either because they contain missing, defective or even rearranged genes, a natural predisposition to develop a cancerous tumor is increased. [5]

Cancer can develop in the healthiest of people because of various genetic mutations they may carry. One such example occurs when there is a genetic mutation in an oncogene. Oncogenes affect the way cells uses energy and multiply. A defective oncogene can contribute to the uncontrolled growth of a tumor. For instance, when the Ras gene (an oncogene) is defective it often produces proteins that cause cells to divide at an accelerated rate. [6]

Finally, mutations in tumor suppressor genes have been found to result in an onset of cancer. Tumor suppressors are supposed to prevent tumors from forming. However, when mutated these suppressors allow cells with abnormal DNA to survive and multiply. [7]

Looking at cancer’s long list of known causes, it is easy to see how one in two men and one in three women will develop cancer in their lifetimes. [8] The development of cancer starts with a basic malignant cell. Malignant cells are dangerous because they divide at a pace that is much more rapid than the pace of normal cells. These cells divide rapidly because they carry damaged genes. As the cells keep dividing, they cluster together to form a malignant tumor. [9]

Tumors cause great destruction to the body. First, they put pressure on nearby tissues and organs. The tumors can invade these organs directly through a process called direct extension, and they often damage and even disable organs. Furthermore, malignant tumors make invaded organs and tissues more susceptible to infection. Finally, tumors can destroy nearby tissues by releasing harmful substances. [10]

Tumors can thrive throughout the body. They can spread from their origin through a process called metastasis. Metastasis occurs when a tumor releases millions of malignant cells into the nearby bloodstream. Fortunately, most of these cells are killed by the immune system, or from the trauma of traveling through the walls’ of blood vessels. However, surviving malignant cells can bind to the lining of these walls. As more and more cells bind to a new location elsewhere in the body, a new tumor develops. [11]

It is clear that malignant tumors are the main threat that cancer presents to the body. In treating cancer, it is essential that these tumors be eradicated. Fortunately, drugs called immunotoxins are created for this very purpose. The job of an immunotoxin is to seek and destroy malignant tumors. One can think of an immunotoxin as a “nanoscale scalpel,” because of its ability to specifically target and kill dangerous tumors. [12]

Immunotoxins are chimeric by nature. They are composed of an antibody, which seeks out cancerous tumors, and a toxin, which kills the tumors. These two components are cloned together through recombinant DNA techniques. [13]

The antibody is an essential part of an immunotoxin. Malignant cells have a different class of proteins that are involved in cell-to-cell interaction and adhesion. Certain antibodies have the ability to bind to these proteins. The antibodies that can bind to malignant cells are determined, and cloned to a toxin of choice. [14]

Toxins alone are merely health hazards. A toxin targets indiscriminately, killing normal and malignant cells alike, causing the body great damage internally. However, when attached to the right antibody, toxins become biological tools that have the potential to destroy whole tumors. Essentially, they are “suicide nanorobots.” After binding to a cancerous cell, immunotoxins will enter and destroy it. A toxin unleashed inside a cell jumps from one molecule to the next, killing it with ease. After destroying the cell, the immunotoxin simply self-destructs. [15]

Immunotoxins are a promising treatment for cancer patients. In December, 2006, the National Cancer Institute revealed that the immunotoxin BL22 caused complete remission of hairy-cell leukemia after just three doses in half of the patients tested in a clinical trail. The BL22 immunotoxin is composed of the PE38 toxin and an antibody that binds to the receptor CD22, which is found on hairy-cell leukemia cells. The PE38 toxin is derived from a toxin produced by bacteria. It has the ability to kill human cells by blocking their ability to make new proteins. [16]

While the BL22 immunotoxin help sufferers of hairy-cell leukemia achieve remission, it does not yet have the ability to help patients with solid tumors. Leukemia causes a person to have a poor immune system; therefore patients cannot create an immune response to the PE38 toxin, and it can target cancerous cells before being struck down by the immune system. However, in patients with solid tumors who also have stronger immune systems, the PE38 is destroyed before it can make its way to these tumors. [17]

Currently researchers are cleverly working around this problem. After testing in mice which antibodies specifically reacted to the toxin, researchers have already identified sites on the PE38 that stimulate a response from the immune system. The researchers are now working on creating a strand of the PE38 toxin that lacks the amino acids that provoke a reaction from these antibodies. In creating the new and improved PE38, researchers will be able to make an immunotoxin with the potential to destroy solid tumors. [18]

Cancer ends life in a painful, torturous manner; it is difficult to understand how it can start through a single malignant cell. Nevertheless, it does and in doing so kills millions of people around the world every year. Cancer is expected to attack fifteen million people in the single year of 2020. The developing world faces nine million of these new cases, and will lack the ability to treat a majority of those afflicted. [19] Radiotherapy is costly and expensive, and often times ineffective in killing off malignant tumors; the world needs to rely on a better cancer treatment. As displayed by the BL22, immunotoxins have the potential to be the wonder drug that the world so badly needs in eradicating cancer. Immunotoxins can bring an end to malignant tumors, to cancer, and to painful deaths that millions worldwide have no alternative but to suffer through.

[1]: "Statistics for 2006." ACS. 2007. ACS. 2 Mar. 2007 .

[2]: "Developing World Faces Cancer Crisis." BBC. 26 June 2003. 3 Mar. 2007 .

[3-7]: Gordon, Jerry. "How Cancer Works." Howstuffworks. 4 Mar. 2007 .

[8]: "Statistics for 2006." ACS. 2007. ACS. 2 Mar. 2007 .

[9-11]: Gordon, Jerry. "How Cancer Works." Howstuffworks. 4 Mar. 2007 .

[12-15]: Goodsell, David S. Bionanotechnology: Lessons From Nature. Hoboken: Wiley-Liss, 2004. 240-241.

[16-18]: Pastan, I, and R Hassan. "NCI Researchers Develop Modified Immunotoxin for Cancer Therapy in Mouse Study." NCI. 12 Apr. 2006. 5 Mar. 2007 .

[19]: "Cancer Menace on the Rise." BBC. 31 Aug. 2001. 3 Mar. 2007 .

Ricin and Immunotoxins

There are very few substances in this world that have both the ability to give life, as well as take it away. Since, September 11, 2001, the world as we once knew it has changed forever. Terrorist attacks using biological weapons/substances are a growing concern. One likely candidate for use in these kinds of attacks is a protein called ricin. Ricin is a toxin that can be extracted from the castor bean plant (Ricinus Communis) and can be found in the oil left behind from smashing the beans and leaves of the plant ( Layton). As an extremely effective toxin, ricin’s main function when released into the human body is to enter cells and prohibit the ribosomes from producing proteins (Layton). Nicknamed RIP, or Ribosome Inactivating Protein, ricin kills off all the ribosomes in the cytoplasm and terminates any chance of future protein synthesis (CDC). Proteins perform just about every function in a cell and a human’s health quickly deteriorates as their manufacturers are intoxicated and killed one by one.

New discoveries and innovative ideas in science and medicine are leading scientists to believe that ricin’s function can be used to kill specifically targeted cancer cells. Obviously, this toxin has the ability to kill humans, but in the near future it may ironically be a molecular machine used to breathe life into cancer patients, having the largest impact on developing countries.

Everyone is susceptible to cancer. In the United States, cancer accounts for one in every four deaths (ACS). Second only to heart disease, cancer kills more people in the United States over any other cause. In 2007, it is estimated that 564,830 people in America will die from cancer, which is about 1,500 people every day (ACS). As world population is increasing exponentially, these statistics illuminate a deadly disease that will continue to plague a larger world population in the future.

Not surprisingly, cancer affects people all over the world. Cancer took the lives of 6.7 million people worldwide in 2002 and this number is estimated to jump to 10.3 million deaths by the year 2020 (ACS). As Americans, we are fortunate to have access to such advanced healthcare. However, in many developing countries, the term healthcare is virtually non-existent. The main problem with healthcare in most developing nations is the lack of doctors and medicines able to adequately diagnose and treat people with this disease. Death rates from cancer in developing countries are much higher for these reasons.

Cancers of the liver, stomach, and cervix are the biggest threat to developing countries, second only to tobacco, which is the leading cause of cancer in the world (ACS). About 85% of the world’s population lives in developing countries and it is estimated that by the year 2010 these countries will consume 71% of the world’s tobacco (ACS). Clearly, cancer will continue to devastate millions of people in these developing nations as they will increasingly put themselves at risk of getting cancer through such high use of tobacco.

In the future, treatment of cancer in developing countries needs to be a global focus in science and medicine. New drugs, more accessible doctors, faster diagnosis, and better technology will be essential to help cut down on the number of deaths related to cancer.

Given the number of deaths related to cancer worldwide, it is obvious that the world needs a more effective and inexpensive way to treat this disease. Actually, the term cancer includes over one hundred separate diseases that are characterized by an abnormal and unregulated growth of cells in the body (Gordon). The cells that are affected by cancer are called malignant cells, which means that they divide at a more rapid pace than normal human cells do (Gordon). As these cells divide more rapidly than the natural rate due to damaged genetics, they begin to form a malignant tumor, which in turn destroys the tissue and organs that are close by (Gordon). In some instances, tumors release millions of malignant cells into the bloodstream which travel to other parts of the body where they form new tumors that further destroy other organs in other parts of the body (Gordon).

Fortunately, new advances in medical science have lead to the development of immunotoxins which are geared to find and eliminate malignant tumors caused by cancer. One of the toxins that researchers are considering using is Ricin.

Ricin may prove useful in cancer treatment because it is one of the most potent cell-killing toxins in existence. In fact, Ricin is so potent that a dose given to a human that is the size of the head of a pin would prove to be deadly (CDC). However, while Ricin is the toxin that is needed stop ribosomes in cells from producing proteins which are essential to cell life, the immunotoxin will not be effective unless it is combined with an antibody that will specifically seek out the unwanted cancer cells (Cornell). The immunotoxin carrying the Ricin must target only the cancerous cells and bind to specific cites on the surface of the cancer cell. Furthermore, the immunotoxin must then be internalized in the cell so that it may reach the cells cytoplasm were it has access to all the cell’s molecules for total destruction (Fitzgerald). Up to 108 ricin molecules can potentially bind to any given cell. Just one of these molecules that reaches the cytoplasm can destroy 1,500 ribosomes per minute and rapidly stops protein synthesis, effectively killing the cancerous cell (Cornell).

Even more interesting is the fact that researchers and scientists have the ability to clone this immunotoxin and make modifications to its genetic structure (Fitzgerald). Put brilliantly by Fitzgerald:

“By deleting the DNA that codes for the toxin binding region and replacing it with various complementary DNA encoding other cell-binding proteins, it has been possible to make chimeric toxins that kill cells on the basis of the newly acquired binding activity. The ability to make these chimeras may be useful in designing future toxin-based anticancer therapies.”

Scientists have found that immunotoxins perform their task very well in in vitro scenarios, like bone marrow transplants for instance by successfully killing T lymphocytes which help the receiver accept the donor’s bone marrow (Cornell). Researchers have yet to have similar success in in vivo applications, such as treatment of solid tumors (Cornell). Problems when attempting this type of treatment through the use of ricin immunotoxins occur because the immunotoxin can not successfully access the entire tumor mass for destruction (Cornell). The most common problem that is observed when treating patients with the ricin immunotoxin is called “vascular leak syndrome”, where fluids leak from blood vessels and cause several unwanted side effects (Cornell).

While finding a cure for cancer is highly unlikely, the future of cancer treatment lies in these immunotoxins. As more work is done on immunotoxins to improve their effectiveness and reduce side effects, they have the most potential for long term constant treatment. Immunotoxins would have the most impact on developing countries as they will likely be administered through pills or injections. Mass screening could also be offered free of charge through organizations to these developing countries in an effort to catch cancer early, which greatly reduces the risk of fatality (Cavalli). People would no longer have to travel to a hospital or pay for radiation and other expensive chemotherapies. Instead, once diagnosed, perhaps patients would be able to take a pill in their own village or home that would regulate and kill their cancer. With time, the pills would also be cheaper and easier to distribute in comparison to today’s leading cancer treatments (Cavalli). The development of effective immunotoxins can change the cancer-world as we know it.

Antibodies Elizabeth Newman

Elizabeth Newman

FYS Final Paper 2

Dr. Macosko

27 March 2006

Antibodies and the Detection of Viruses

In 2006, 4.3 million people were diagnosed with the human immunodeficiency virus (HIV). Also in 2006, 2.3 million children were living with HIV. Most cases of AIDS go undiagnosed, especially in underdeveloped countries stricken by poverty and lack of education. In the United States, individuals are often too embarrassed and too afraid to be tested for the HIV virus. Recently, researchers and scientists have developed an oral test that is both cheap and can be taken in the privacy of your home. This test is called Orasure. Orasure works by detecting the HIV antibodies present in the saliva of an infected person. An antibody, or immunoglobin, is a protein that binds to a specific antigen that must be eliminated by the immune system. Therefore, diagnostic test can be created to detect antibodies that are specific to certain diseases and viruses due to the structure of antibodies that allows for specificity. Antibodies play a vital role in immune responses by activating the Complement System. The Complement System is a series of thirty proenzymes that trigger immune responses through the complement cascade. The Complement System is activated when an antibody binds to a specific antigen. Due to the structure of antibodies, antibodies have the unique ability to distinguish between many different antigens. Because of the antibodies’ specificity, antibodies are used in medicine in order to detect specific diseases, such as HIV.

The structure of antibodies allows for their specificity and the diagnosis of viruses. Antibodies are composed of four polypeptides: two heavy chains and two light chains. These two chains form a “y” shape. The amino acid sequence located at the tips of the antibody is the region that distinguishes one antibody from another and gives the antibody its specificity. The tip of the antibody is called the variable region. The antibody will only bind to an antigen with the corresponding amino acid sequence. There are 110-130 amino acids that make different combinations at the variable region of the antibody. Also, there are constant regions on the antibody. The constant regions are responsible for the biologic functions of the antibodies. The unique combinations of amino acids at the variable region are used in the classification of antibodies.

This diagram shows the y-shape structure of the antibody and the variable region of the antibody.

The heavy chains and the light chains have different functions. The light chains of the antibodies are divided into two domains. The domains consist of about 110 amino acids. The two domains are called the N-terminal and the C-terminal. The N-terminal is highly variable and is called the V_L region (very light). On the contrary, the C-terminal remains constant and is called the C_L region (constant light). The heavy chains are larger than the light chains, but their structures are very similar. The heavy chains have a N-terminal that is composed of 110 amino acids that vary in sequence from one another. The N-terminal is called the V_H region (variable heavy). There is also a C_H region that remains constant (constant heavy). Therefore, these chains allow for the variability of antibodies that is essential for antigen binding.

Antibodies are divided into five classes according the combinations of amino acids at the variable region. The variable region is divided into two different subunits: the hypervariable region and the framework region. The hypervariable region binds to the surface of the antigen and consists of many different amino acids. The framework regions form beta sheet structures that act as structural supports when the hypervariable region binds to an antigen.

The functional fragments of antibodies each play a different role during the process of binding to an antigen. The Fab fragment of the antibody contains the antigen binding sites. The Fab fragment is located on the heavy chain and is created through papain synthesis. The Fc fragment is the constant region that is created through papain digestion and consists of a dimmer of the heavy chain. The Fc fragment controls the effecter functions of the antibody. The F(ab’)₂ fragment binds to the antigen, but is not involved in effecter functions. It is created through pepsin digestion and consists of the light chain. The F(ab’)₂ is dimeric due to the interchain disulfide bridge that binds two hydrogen atoms. The F(ab)’ fragment is a monomer that forms through the reduction of the disulfide bonds that bridge the hydrogen atoms of the F(ab’)_2. The Fd fragment is created through the reduction of the Fab fragment. Thus, each fragment is essential in the specificity of the antibody because each fragment plays a vital role in the binding of the antibody to the specific antigen.

This diagram shows the Fc and Fab regions of the antibody and the disulfide bridge that holds the antibody in its “y” shaped structure. Also, the light and heavy chains are shown.

There are five classes of antibodies: IgM (pentamer), IgG (monomer), IgA (dimmer), IgE (monomer), and IgD (monomer). IgM antibodies are produced directly after the recognition of the antigen. Eventually, the concentration of IgM in the blood will decrease as the immune response continues. IgM has a total of five or six Fc sites for antigen binding. IgG can be found in blood and in tissue fluids. IgG proteins pass through the placenta and allow for passive immunity in a fetus. IgG is less effective in the complement system because it is a monomer and has less Fc sites open for binding to the antigen. IgA antibodies are localized antibodies found in tears, saliva, and breast milk. IgA provides immunity for an infant. IgA consists of a J chain and a secretary component. IgE cause the release of chemicals that cause allergic reactions.

Furthermore, when an antibody binds to an antigen, several different mechanisms may occur. When viral neutralization occurs, the antibody blocks the virus’s ability to affect the host cell. Opsoniztion occurs when an antibody coats the surface of a bacterial cell surface which increases phagocytosis. Therefore, the specificity of the antibodies allows the antibodies to serve many unique functions.

As said before, antibodies have become very important in the diagnosis of many diseases. For instance, HIV diagnostic tests recognize the HIV antibodies in a person’s blood. Recently, a HIV test, called Orasure, was developed to be used at home, giving people privacy and comfort. Orasure collects HIV antibodies from the saliva. Through the antibodies in the saliva, Orasure can determine the presence of the HIV antibodies. In order to use this test, an individual simply swipes the side of his or her cheek and the test is completed in the matter of seconds. Because of this test, many people who were once afraid to be tested for HIV, will take the test. Furthermore, since these tests are easy to take and give definite results, they could be administered easily in underdeveloped countries. Thus, antibodies and the technology reliant on antibodies are very important in the world of medicine.

Overall, the structure of antibodies allows for specificity and allows for the antibody to differentiate between different antigens. The many different fragments of the antibodies perform specific functions, but work together in order to trigger an immune response. Antibodies are very important in current research to detect certain diseases such as HIV. If researchers learn more about the specificity of antibodies, more tests can be made to diagnosis a large range of different diseases. Furthermore, recent technological advances allow scientists to create diagnostic tests that are more convenient for the patient, such as Oraure. Orasure will ensure the privacy of a patient and be very helping in underdeveloped countries. Orasure is especially important because if more people are comfortable taking the test, the spreading of the HIV virus will greatly decrease. Thus, a disease that causes about 84,000 deaths each year can be better controlled. Overall, without the specificity of antibodies, the HIV virus could not be detected, and the virus would spread at a faster rate and those infected with the virus would never be treated.

I didn't get to hear the coconut guy

I didn't get to hear the coconut guy speak but it sounds like it was a pretty informative and interesting talk.

I thought that the speaker was particularly interesting because not only is he helping the envioronment, he is also helping those whose way of life had been destroyed. I thought it was very neat that he would be helping the people in poor tribes to rebuild an economy. Fruthermore, it is interesting that something as simple as the cocanut can lead to so many new possibilites.

Coconuts

I found the guest speaker about coconuts very interesting. The many ways that he and his company are using coconuts to help the poor sounds very intriguing. It seems as though hes wondered upon a miracle fruit to help these poor countries.

Question:

Has anyone heard anything about a nanomachine that could possibly be used in the future to help save our quickly deteriorating environment? It seems like if there was one that fell in this category it would have potential to be a huge success in the future as many start-up companys these days are gearing there companies to be more environmentally friendly in one way or another.

Coconuts

I thought the fact that every part of the coconut could be used to turn a profit was really incredible. If countries in need could get a hold of the necessary technology, coconuts have the ability to set a very strong foundation to build on. I'm surprised this has only been brought to the forefront now, considering Americans have been using coconuts for awhile. I think there is a real chance for great growth in the regions that can grow coconuts plentifully.

Coconuts

I really enjoyed the talk on the various uses of coconuts; I had always believed that coconut oil was really bad for you, so it was really interesting to hear that it was only hype put out by the vegetable oil makers. I think it's a great idea to try and use such an available resource to help villages around the world gain a better quality of life. The idea of using the husk to make building material sounds really viable, and if the coconut oil could be used to fuel cars and electricity, it would really make a big difference in the lives of those in the countries on the equator. All of his ideas to use coconuts sounded like they would be fairly simple to implement in these countries, and would help these villagers tremendously.

I thought that I was really neat that undergrads here at wake were able to compete with graduate students from some of the best schools in the country. Also, I think it is great that molecular machines can help people in third world countries who do not have access to hospitals and doctors.

Community Care Center

I enjoyed the trip to the community care center. I was very impressed by the size of the building and all of the care that they are able to provide without charging any money. I think that what they are doing is great. There are so many people who cannot afford the health care they need, and it's amazing that there are people willing to volunteer their time and make donations so that the care center can keep providing services to those who really need them.

Free clinic thoughts

I was very impressed with our visit to the free health clinic. The building was amazing to me and was totally different than what I imagined a free clinic to be like. I found the tour to be very interesting and insightful in learning how organizations offering free services such as these find the money to stay afloat.

Free clinic Visit

I thought the free clinic was impressive. With expenditures of 4 million dollars and above anually, I can imagine it is difficult to acquire sufficient funding each year. I also thought the screening process for the patients was interesting. They only receive patients at a certain point below the poverty line. The speaker said that wealthier people actually had their maid stand in line for them so they could receive free care. I think the clinic should be allowed to impose a fine for such actions considering the financial difficulty of offering free medical service.

community care center

I was very impressed with the community care center. I am amazed that such a large and advanced office can run purely on grants and donations. The building seemed to exactly mirror my perception of a normal medical office. The idea of having a free clinic seems like a good one, and I expect volunteering there would be a good way to give back to the community.