Cell and Molecular Biology of Cancer Lecture 8 PDF

Cell and Molecular Biology of Cancer 10/11 Virus causes disease by killing the cells Viruses can also insert DNA and proliferate until the cell is off More you got to the edge, they less look like epithelial o Less adhesion Many cells will die when they en...

Cell and Molecular Biology of Cancer 10/11 Virus causes disease by killing the cells Viruses can also insert DNA and proliferate until the cell is off More you got to the edge, they less look like epithelial o Less adhesion Many cells will die when they enter the blood o Viscous site for epithelial cells to be o Often triggers apoptosis How the cells will escape the blood to metastasize in different areas? o 1. Rupture the capillary/arteriole through growth o 2. Reuse the basal lamina breakdown pathway Survival in neighboring tissue is rate limiting step Micrometastases o Not forming thousands of tumors o Chemotherapies are not responsive? Working the night shift = cancer? o In the 80s, it was begun to realized that throughout the 20th century, that cancer rates of many different cancers has begun to increase. There were many explanations § Increase in autism § Vaccine § Throughout the 20th century, there has been more access to healthcare, so we are noticing and recording it at a higher rate. § Modern diet o Researchers thought that working at night increased cancer § During the 20th century, there was the electrophication of America. More people got electricity so the natural rhythems that we have evolved with – going to sleep when its night and getting up during the sun was being disrupted. Hypothesized that part of increase in cancer could be the night shift, as we are disrupting our natural cycles. § Natural sleep was disrupted § Part of increase in cancer could be due to night working and disrupting our natural cycles.  § They turned to doctors and nurses who worked night shifts § Found that there was an increases risk of breast cancer in night shift workers. Studies of different ethnicities of nurses who worked during the night. Found an increase risk of breast cancer in the night shift workers. In this study, they found 40% of an increased risk of breast cancer in the night shift workers. Male night shift workers have a higher risk of prostate cancer o International agency for research of cancer classifies cancer in different groups § Night shifting working has been found in group 2A – probable human carcinogen § Hard to prove but is still probable How does working in the night increase cancer? o The night is when the body repairs itself – messing up those results in higher chance of cancer o Circadian rhythyms § Help guide our body when it should be repearing itself, when it should be activating itself. § Nigh shift workers have disrupted that – hard to adapt their circadian rhythyms § Some of the most important processes that can drive oncogenes are under the control of circadian rhythms § Process controlled by circadian rhythms are DNA excision repair enzymes o Activity increases at night in response to circadian rhythms Immune system function Apoptosis Cell cycle arrest o Circadian Rhythems affected by melatonin § Melatonin is regulated by light. § When night come along, you would have photoreceptor cells in the retina that sense blue light. Exposure to blue light can cause you to have altered melatonin levels. As we get older, we sleep less well which is reflected in melatonin levels. § Lead to the proposition where you can have anti-cancer glasses Blue light blocking classes Can change cancer risks Breast cancer treatment costs vary wildly, study finds. o Doctor had a survivor of breast cancer and wanted to do one final test to make sure the cancer has gone fully into remission. 2  o Patient who recovered triple negative breast cancer refused to do one last breast cancer because of the price o The doctor and many people in healthcare payed attention to the fact that depending on what drugs get prescribed and coverings of insurance affects cost o Doctor studied this and saw that cost could be $46,000 to the patient o Found no correlation between how effective the chemotherapy was to how toxic or less toxic the treatment was with the actual cost. § Found a chemotherapy regime with one of the highest cost ones and patients had the highest toxicity from it. o Difficult for doctors to deal with it. § They have to find out § They would have to be an expert on every insurance plan and what they pay for. § Could lead to huge outcomes for patients. § Have been a push to come up with better databases to allow doctors to better understand these things both that efficacy of the different drugs they’re prescribing as well as the fundamental costs. Viruses and cancer. How have viruses informed our ability to know how cancers happen? § Enter the human body at a certain frequency. Need to explain if they drive cancer or have other effects. § Viruses are cytopathic (killing the cell) Get into the cell Take over the machinery Use the central dogma of the cell to express more of the protein and make more viral particles Eventually the cell will free the viruses and you have the infection cycles. There is a long history of thinking about viruses and cancer. History of viruses and cancer o Peyton reu. § Thought that he could take tumors out of chickens, grind the cells up, filter it away the cells and he could see that he could inject the cell free filtrate which should only have viruses in it. Saw new cancers occurring in the chickens that they were injected into. He did this work because of Louis Pasteur o Louis Pasteur § Showed that there are infectious agents that can get in and grow in different types of media. First time that we understood that there were microorganisms that can drive infectious cycles. Found out that there was infection because a living thing proliferated in there. 3  o Dominated early medicine. o We began thinking that every syndrome must be driven by these agents. § People showing that there was small diseases (small pox, bubonic plage) were driven by bacteria and viruses Categorize these by size o Bacteria has a certain size that would be filtered out – if there is a filter of a certain pore size. § Can filter them through finer things, there would be sizes where only viruses would pass through. o Peyton Rue again § Saw a chicken tumor that acted like an infectious agent § Take that chicken which would have a sarcoma breast muscle, remove the sarcoma, begin homogenizing (fuse) it, begin grounding it up, pass it through different size filters to get to a very fine pore filter, and you can take that filtrate that no longer had any of these original cells, so it wasn’t any of these cells that was constituting a cancer, that was the virus that was getting in, infecting cells into that chicken, and you could see a reoccurrence of the sarcoma. This suggested that there was something in that virus that could cause a cancer. The virus got in, infected the cells and resulted in the reoccurring of that carcinoma. § Peyton Rue potentially had the first oncogene Decades before what we could have discovered that gene § Got the noble prize about 55 years later His work was discredited at first. This is because everyone was looking for infectious agents, Johannes Fibiger studied spirochete worms (associated with lime disease) and saw a correlation between having these worms and stomach cancers. o Published that spirochete worms are the root cause of stomach cancer and many cancers around. People quickly realized he was wrong. He was awarded Nobel prize but realized that there was dietary problems in his rats so spirochete worms were not the cause, so they threw out his work as well as Peyton Rue and other peoples work who wanted to say that infectious agents cause cancers. We studied many environmental factors (carcinogens, radium girls) that lead to higher mutation rates. For 40 or 50 years, the mutagens and mutagen view on cancer dominated. o People thought there were so many agents in the world that are causing cancer. 4  50-60 years later, we became more molecular scientists and understanding the structure of DNA, and we began to revisit the RSV that could cause cancer o Scientists studied and saw that if they took that virus, dumped it on cells in tissue culture, these cells would start to look transformed, they would start rounding up, dividing too much, and get bundles of cells that are dividing too much, crowding on other cells and essentially looking like the first stages of the oncogenic transformation. Scientists also studied: Does the viruses infection? Or RSV needs to always be around to drive cancer? o Profound implications for how it could function. o Source of mutation o Or expresses a protein that makes an oncogene causes cancer. o First time proved there was a cancer causing genes in a virus was through this experiment. § Had an RSV temperature sensitive mutant, where if you were at the non- permissive temperature (don’t have a function of that virus). They took the temperature sensitive RSV viral particles, infected cells at the permissive temperature, those cells became transformed (cells began to look like early cancer cells). o Do you always need that virus around? Does that virus actually have to make something? § Can shift the temperature up to the non-permissive temperature, the virus is no longer productive, and the cells reverted back to their normal morphology, they were rescued back to a non-oncogenic site. § If the temperature was shifted down, the cells would look like they’re proliferating too much, and beginning to press on other cells. § Suggested that there was a real oncogene and genetic material in there that needed to be around and be expressed to cause that ontogenetic mutation. § RSV – the oncogenic virus had to be maintained. There wasn’t a one time mutational event that drove this. § Exciting, because we have for the first time, an oncogene. § First oncogene ever discovered came from this RSV. How can viruses be maintained? How do viruses stay around? o 1. You can have chronic infection pathway § Like hepatitis C o 2. Or incorporation into the host (human genome) § Like HIV How would you show the above? How to detect if the viral DNA is in the chromosome or free-floating genome in the cytoplasm? o Differentiate based on size 5  § One way his is done is though Spin things – increase the force of gravity and the heavier and bigger things sink faster. Little DNA molecules float up higher. o Medium or the large sized DNA molecules can be run on the southern blot (one lane from higher regions and one lane from lower regions) and detect the viral DNA with the probe nucleic acid. § Probe genomic DNA there § If they’re both there at the same region, there is an integration event § Look at the size of the DNA that the virus is in. Cervical Carcinomas o Cancers that viruses are most associated with. o 20 years ago we began to sequence DNA that is present in different cancers and realized that in people who had cervical carcinomas, 99.7% of the time, a virus was found there. This is the famous Human Papilloma Virus (HPV) o Not always the entire virus. It is always very specific fragments of the HPV genome. § It is a portion of the genome that carries a cancer causing oncogene o Most curable cancer out of all human cancers § We need to prevent HPV o Exciting because we can prevent vast majority of cervical cancers by keeping people from getting HPV HPV o Good vaccine target o Can cause throat cancers in males. Cervical cancer o Second leading cancer of women Rick perry o Discovery was made when he was governor of Texas o He went to MD Anderson and saw all patients who had cervical cancer, and was shocked. o Doctors told him that a virus drives the cancer. o Since there is a vaccine against HPV, he required for 6th grade Texas girls to get the vaccine. § There was a pushback on this – no longer mandated o People realized that this was a vaccine against STD and got mad o We can limit cervical carcinomas if we limit Human Papilloma Virus (HPV) o The vaccine was pushed back o Recommended by doctors to give the vaccine to both boys and girls before they become sexually active – before they can get exposed to that potential virus. Viruses and oncogenes o Viruses became good candidates for discovering what oncogenes are. Tumor viruses. Why the size of the genome might be important? o HPV was only 8 thousand base pairs o Human genome is 3 billion base pairs 6  o Viruses are thousands of base pairs o Very first oncogene was discovered in a virus o Most human cancers are not driven by a virus, but studying viruses helped discover the first oncogene and tumor suppressors. § Tumor suppressors have been discovered in a virus that had a oncogene that inhibit a tumor suppressor. § P53 was discovered in a virus that had a protein that bound to an inactivated p53. The virus wasn’t mutating p53, but it had a protein in it that bound and antagonized p53. RSV virus – very first oncogene discovered o Cause tumors in chickens o Scientists realized that it was closely related to another avian virus that didn’t cause tumors o Looked at the genomes, there were just three proteins in the virus and only needed these three proteins to replicate itself EXCEPT RSV had a fourth gene the src/sarcoma gene. § When sequenced it, they found it to be an oncogene and thought this may be the difference between this virus that can cause a tumor and the virus that cannot cause a tumor. Why doesn’t every human being have a cancer? o There are protoncogenes that are unmutated and there is a mutated form of that normal gene that is present in the virus that’s driving this. C-src (cellular src) o Normal unmutated version of src V-src (viral src) o Mutated, oncogenic version of src § Gets stuck in the on state when it is mutated o Lacks a tyrosine that when phosphorylated, it turns off Src o Binds to growth factors receptors o Helps to signal when a growth factor bound to that receptor, you activate src. o When it gets activated: § It turns on and activates, ras, myc, and can lead to the production of the cyclin proteins § Can have a potent oncogene that was present in a virus, and if that virus got into those chicken cells, could tell those cells to function like they always have growth factor even when it’s not there, which will continue to signal like the classic oncogenes. o First oncogene known to humans Chickens o Have lots of transforming viruses Some viruses cause cancer quickly, some take time. o Acute transforming viruses 7  § Happen quickly § Possess oncogenes (fully functional and operating) Already have an oncogene, which they already express and causes too much cell division, maybe this gives that virus a growth advantage because it is in cells that are growing rapidly and therefore, they can make more of themselves more quickly. RSV, Src o Slowly transforming viruses § Take time § Does not posses oncogenes § They have a promotor – incorporate themselves, change the DNA to drive this § Have the unique ability to incorporate into the genome § Retroviruses, some non retroviruses do this. § Viruses that cause cancers - don’t enter into every genome at equal rates – have favorite regions where they enter Prefer to enter into myc DNA It is poor Over replicates itself High rates of viral insertions in regions where there is this gene. § Slowly transferring viruses Begin to enter in the genome over time at certain rates Enter in such a way that the promotors of the virus (viruses really potent promotors, they want to make lots of their proteins to take over the cell and they can make lots more viral particles)– if the promotor inserts in the right way, orientation and location next to a potential oncogene, drive too much production of myc and uncontrolled proliferation. o Takes time for the virus to get in and incorporate itself into the genome. This is a slower cancer o Integration is a rare event that must integrate in the right place with the right orientation o Will likely be only a very few cells that are transfoemed, so it will take longer to grow the tumor mass. § Slowly transferring viruses are known to be Insertional mutagenesis Take a foreign piece of DNA and inserting it into the genome DNA jumping in agents: Transposons DNA jumping in agents: Retrotransposons DNA jumping in agents: Virses DNA jumping in agents: Retroviruses All of the above can insert themselves into chromosomes and cause a mutational event to occur. 8  All of these cause oncogenic transformation through insertional mutagenesis o One of the great promises for cancer treatments: § Can only incorporate new tumor suppressors, new unbroken copies of P53, you can cure cancer. § Need to insert DNA. § Have created a retrovirus with a good copy of P53 in it and one the concerns are discussed in the following: § Gene therapy We have viruses that we can make which will bring in proteins that we want. We know the root cause of human disease is – we just need to fix it Take a virus, modify its genome (have the gene of interest), package that into a virus, since viruses are good at being able to get into cells and be able to insert themselves into the genome. If we can genetically modify individuals to fix mutations present in their genomes. One of the biggest problems at achieving effective gene therapy has been side effects of unintended cancers. One of the first gene therapies o Gene therapy: Kids with x-linked severe combined immunodefienciency – lack activity of the gamma-C protein (helps the immune system function) § Decided to make a retrovirus, put gamma C protein and could free these kids. § Took a MLV retrovirus and genetically engineered it to contain the gamma-C gene that was created First clinical trial – they injected 10 children It was good for a certain period of time 9/10 cells recovered immune system function Then things started to go wrong o 30% started to develop T-cell leukemias o MLV likes to incorporate in a certain part of the genome. There is a hotspot for MLV integration that is within 2 kbs (within 2000 base pairs within the start) of the start of the LMO2 gene which is a superpotent oncogene for T-cell leukemias § Has been seen over and over again as we have tried to do gene therapy. o Often gene therapy is fairly successful but often there are unintended consequences of having oncogenic events that occur. o Gene therapy: Kaposi’s sarcoma – human cancers that are driven by viruses § Used to be a very rare cancer 9  § When HIV become the AIDS epidemic, it went from being super rare to occurring mostly in men of middle eastern and Jewish decent to the fourth most common infection induced cancer worldwide. § Sarcoma that causes black spots in the skin as it progresses. § Everyone thought it was just genetic before AIDS § When all these men had it at the start of the aids epidemic it became clear that it was being driven by an infectious agent and that infectious agent, as the immune systems was being compromised, was beginning to function at higher and higher levels, and getting higher viral infections. § Before AIDS was around, people thought it was a genetic disease. § After AIDS, it became apparent that these sarcomas were often infected with a certain form of the human herpes virus HHV-8 virus. § HHV-8 is a bad virus – not good at infecting If you have a good immune system, it is fairly unlikely that it will lead to a successful infection. Does not spread horizontally with the population (will not infect the person sitting next to me in a class with it). o If given enough time and we are living in close proximity with someone (family situation), it will tend to have a successful infection. o Will spread over time vertically from infected people with prolonged, intimate contact § Verticle infection cycle makes it look like it is a genetically inheritable trait. § Fooled scientists for a long time. People thought it was a inherited mutation that ran in the families of people middle eastern and Jewish descent. In reality, it was a virus that a the immune system became weaker, you had more spread of the virus and it could drive the generation of this. Human immune system o Evolutionarily selected very strong immune system that has been able to tamp down things (viral infection rates), and keep viruses from being one of the major cancer causing agents in human beings. Viruses are still useful sicne they have allowed us to discover oncogenes. 10