Causes of Cancer (Journal of Molecular Oncology & Research)
Cancer is a disease caused by genetic changes leading to uncontrolled cell growth and tumor formation. The basic cause of sporadic (non-familial) cancers is DNA damage and genomic instability. A minority of cancers are due to inherited genetic mutations. Most cancers are related to environmental, lifestyle, or behavioral exposures. Cancer is generally not contagious in humans, though it can be caused by oncoviruses and cancer bacteria. The term "environmental", as used by cancer researchers, refers to everything outside the body that interacts with humans. The environment is not limited to the biophysical environment (e.g. exposure to factors such as air pollution or sunlight), but also includes lifestyle and behavioral factors.
Over one third of cancer deaths worldwide (and about 75–80% in the United States) are potentially avoidable by reducing exposure to known factors. Common environmental factors that contribute to cancer death include exposure to different chemical and physical agents (tobacco use accounts for 25–30% of cancer deaths), environmental pollutants, diet and obesity (30–35%), infections (15–20%), and radiation (both ionizing and non-ionizing, up to 10%). These factors act, at least partly, by altering the function of genes within cells. Typically many such genetic changes are required before cancer develops. Aging has been repeatedly and consistently regarded as an important aspect to consider when evaluating the risk factors for the development of particular cancers. Many molecular and cellular changes involved in the development of cancer accumulate during the aging process and eventually manifest as cancer.
Although there are over 50 identifiable hereditary forms of cancer, less than 0.3% of the population are carriers of a cancer-related genetic mutation and these make up less than 3–10% of all cancer cases. The vast majority of cancers are non-hereditary ("sporadic cancers"). Hereditary cancers are primarily caused by an inherited genetic defect. A cancer syndrome or family cancer syndrome is a genetic disorder in which inherited genetic mutations in one or more genes predisposes the affected individuals to the development of cancers and may also cause the early onset of these cancers. Although cancer syndromes exhibit an increased risk of cancer, the risk varies. For some of these diseases, cancer is not the primary feature and is a rare consequence. Many of the cancer syndrome cases are caused by mutations in tumor suppressor genes that regulate cell growth. Other common mutations alter the function of DNA repair genes, oncogenes and genes involved in the production of blood vessels. Certain inherited mutations in the genes BRCA1 and BRCA2 with a more than 75% risk of breast cancer and ovarian cancer. Some of the inherited genetic disorders that can cause colorectal cancer include familial adenomatous polyposis and hereditary non-polyposis colon cancer; however, these represent less than 5% of colon cancer cases. In many cases, genetic testing can be used to identify mutated genes or chromosomes that are passed through generations. Gene mutations are classified as germline or somatic depending on the cell type where they appear (germline cells include the egg and the sperm and somatic cells are those forming the body). The germline mutations are carried through generations and increase the risk of cancer. Cancer syndromes
BRCA1 & BRCA2
Familial adenomatous polyposis
Hereditary breast and ovarian cancer
Hereditary non-polyposis colon cancer
Nevoid basal cell carcinoma syndrome
Von Hippel-Lindau disease
Thanks & Regards,
Managing Editor Journal of Molecular Oncology Research