on
Cancer
“In God we trust. All others must have data.” - Bernard Fisher.
I am amongst the fortunate ones who have had the opportunity to have a deep insight into the grim world of cancer and serve those afflicted by it through my nature of work as a Medical Physicist. Cancer has been one of the most talked about epidemics in the last decade or so but in pragmatic terms the stigma and myths associated with it are astounding due to the lack of knowledge, information and guidance about it. In a developing country like India where exists a large socio-economic barrier extending across sections of society, it becomes imperative that we indulge in the practice of self-awareness and those related to us because early diagnosis (recognizing the disease) is the most effective cure as well.
UNDERSTANDING CANCER
Cancer is the name given to the collection of cells that no longer follow the natural process of cell division, growth and death and hence become uncontrolled. In all types of cancer, some of the body’s cells begin to divide without stopping and spread into surrounding tissues. Cancer can start almost anywhere in the human body, which is made up of trillions of cells. Normally, human cells grow and divide to form new cells as the body needs them. When cells grow old or become damaged, they die, and new cells take their place. When cancer develops, however, this orderly procedure breaks down. As cells become more and more abnormal, old or damaged cells survive when they should die, and new cells form when they are not needed. These extra cells can divide without stopping and may form growths called tumors.
The birth and development of cancer in the human body is divided broadly into three steps:
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Initiation: We now know the formation of cancer takes first place at the cellular level which comprises of our cells. Cells are made up of genetic material called the DNA (deoxyribose-nucleic acid). Any kind of a mutation in the DNA which can have many potential initiators like environment exposures, tobacco, lifestyle choices, obesity, alcohol, genetics cause mutations in the makeup of the DNA which codes for the proteins in the body. As we grow these “errors” grow as well and hence initiate the formation of abnormal growth and function of new cells in the body.
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Promotion: Once the function has been initiated due to the stacking of overtime errors in the body, things are never the same again. The two main genes in the body that participate further in the play are the Proto-oncogenes and Tumor suppressor genes.
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Proto-oncogenes: These genes under normal circumstances work for the birth, growth and the proliferation of new cells in the body. However, due to the errors get altered and are then turned into oncogenes which are tumor promoter genes and lead to uncontrolled cell division without any cell regulation. In scientific terms, most often these genes are autosomal dominant, meaning that only one copy of the gene needs to be mutated to elevate cancer risk which means the risk for proto-oncogenes turning into oncogenes is higher (and sadly easier!).Examples of oncogenes are: RAS, MYC, HER2, etc
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Tumor suppressor genes: Tumor suppressor genes are also involved in controlling cell growth and division. Cells with certain alterations in tumor suppressor genes may divide in an uncontrolled manner. Most often (but not always) autosomal recessive, a mutation in both copies in our chromosomes (they exist as pair in the DNA of the cell) must occur before it increases the risk of developing cancer. Examples of tumor suppressor genes are: BRCA1, BRCA2, etc.
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Angiogenesis: At some point, after months or even years as a harmless cluster of cells, tumors may suddenly begin to generate blood vessels—apparently because they develop the ability to synthesize certain growth factors that stimulate the formation of vessels. Angiogenesis is an important step that a tumor undergoes in its transition to life-threatening malignancy (cancer). When tumor cells reach this transition, they call on proteins that stimulate capillary growth and develop the ability themselves to synthesize proteins with this capacity. One of these proteins is known as vascular endothelial growth factor (VEGF). VEGF induces endothelial cells (the building blocks of capillaries) to penetrate a tumor nodule and begin the process of capillary development. As the endothelial cells divide, they in turn secrete growth factors that stimulate the growth or motility of tumor cells. Thus, endothelial cells and tumor cells mutually stimulate each other. Cancer cells also produce another type of protein that inhibits the growth of blood vessels. Hence via angiogenesis the cancer cells feed off from the oxygen supply of the normal cells and migrate to other areas of the body causing metastasis.
References
- Eric J. Hall, Amato J. Ghiaccia, Radiobiology for the Radiologist, Philedelphia, USA:LIPPINCOTT WILLIAMS & WILKINS,2012
- American National Cancer Institute,NCI, 2021,Available[https://www.cancer.gov/] (Accessed:Feb 16,2021).