I learned so much about cancer at the AACR annual meeting. I attended many lectures by many scientists. These are some of the things I learned about cancer:
1. Some say that cancer is genetic, that the genes you are born with determine if you will one day get cancer. The truth is that the number of cancers inherited from parents is very small, though some of us inherit especially effective genes for preventing or suppressing cancer (the people who smoke forever and never get cancer). Usually cancer results from genes that become abnormal or mutated as we age, often in response to environmental factors like cigarette smoke or exposure to carcinogens in our environment. Usually cancer results from a combination of many genetic mutations, not a single mutation.
2. Cancerous mutations occur over a long period of time. Normally cancerous changes take at least 10-30 years to develop, one scientist said they may take even 30-50 years. Because of this, most cancers occur in older people. This is why cancers that occur before the age of 45, like mine, are suspected to have an inherited genetic component. With the aging of the baby boomers, the number of cancer cases in the US will increase by 30-50% as we approach the year 2020. One in three in the US will one day receive a cancer diagnosis.
3. Normally when a mutation causes cells to become abnormal, the cell has genes that automatically repair the abnormality or the cell is genetically programmed to commit suicide (apoptosis)to prevent the abnormality from being passed on. Tumor suppressor genes we normally have regulate this protection from cancer. In cancer some of these tumor suppressor genes are themselves mutated.
4. Normally cells are programmed to stop reproducing when there are sufficient numbers for the body's needs or when they come into contact with other cells. For instance, if you scrape your skin new cells grow to replace the damaged skin, but once there are enough cells to replace the damaged skin, cells have a mechanism to signal them to stop growing. Cancerous cells have lost the mechanism that signals them to stop growing, therefore they continue to grow into masses, or tumors.
5. Normally cells only grow in their own environment and cells of one organ do not travel to other organs, and if they do, they automatically die when they are in the "wrong place". Cancer cells have learned several methods of travel that allow them to go to other places in the body, and when they reach a new destination, their abnormal growth is unstoppable. The name for this is metastasis. Metastatic tumors are usually genetically different from the primary tumor they originated from. 90% of deaths from cancer are caused by metastasis.
6. If you remember in the news, the Human Genome Project was completed in 2003. It took 13 years, but new technology allowed the identification of the 20,000-25,000 genes in the human DNA and the identification of the 3 billion chemical base pairs that make up human DNA. This identification of the normal human DNA has allowed researchers to identify genes that are abnormal and that can cause cancer. A project is now in place, the Cancer Genome Project, to identify the abnormalities in the genes of cancerous tumors.
7. One gene discovered, P53, creates a protein that regulates cell division and prevents tumor formation, it also signals a cell to repair abnormal DNA. P53 has been nicknamed the "guardian" of normal cell genes. In one inherited genetic syndrome in which P53 is abnormal, cancer is usually diagnosed at a young age and the person is often diagnosed with multiple different kinds of cancer in a lifetime. I've met one woman my age who has been diagnosed with 5 different kinds of cancer in her lifetime, her first cancer diagnosis was breast cancer at age 13. I wonder if she may have had that syndrome. The P53 gene is mutated or damaged in 50-55% of people diagnosed with cancer.
8. Cancer cells are able to continue to grow into tumors and to metastasize because they are able to produce a substance that causes new blood vessels to form (angiogenisis) to supply blood, therefore food and oxygen, to the tumors. Normally this process doesn't occur in humans except prior to birth when the circulatory system is developing, in the lining of the uterus during menstruation, or during repair of injured tissues.
9. One lecture I attended attributed 30% of cancers to cigarette smoking, not just lung cancer, but also cancers of the mouth, throat and bladder. Cigarette smoking is also related to the incidence of colon, kidney and pancreatic cancers.
10. Twenty percent of cancers are related to obesity, especially in post menopausal women. This is associated with the fact that fat cells produce estrogen. Estrogen levels in postmenopausal women are 50 to 100 percent higher among women who are overweight than in women who are of normal weight. It is also thought that a higher production of insulin or insulin-related growth factors may play a part in promoting cancer in those who are overweight. There is more information here: National Cancer Institute Fact Sheet: Obesity and Cancer.
12. Metabolic syndrome is now seen as a cancer risk factor.
13. Poor diet is responsible for 25% of cancer cases. In one study, colon cancer patients on a Western diet had 3 1/2 times higher cancer recurrence after treatment than those on an Asian diet. While not yet identified, it is believed that there are chemical agents in fruits and vegetables that protect against cancer.
14.Some infectious diseases are also associated with a cancer risk; for example HPV and cervical cancer and H. pylori and gastric cancer. Over-exposure to sunlight is related to skin cancer.
Everything I learned helped me to understand that cancer is not a simple disease. Cancer actually comprises a set of 200 different diseases. Each type cancer is different, there is no easy one-size-fits-all solution. Cancer cells have evolved from a combination of many alterations in a normal cell over a long period of time, and cancer cells have found many ways to overcome and survive the body's normal defense mechanisms. Cancer is a vicious enemy.
I know this was a long post, so I will divide up posts. My next post will be about advances made in cancer treatment and what is new on the horizon.
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