Cancer is the rapid, unregulated and pathological growth (proliferation) of
abnormal cells. Even when cancers occur in the same part of the body, they can be very
different diseases. When tumors become malignant, their threat depends on their ability
to modify surrounding cells to form new blood vessels (angiogenesis) and other
supporting cells. The typical American diet that leads to obesity can make people more
susceptible to cancer. The human papilloma virus, hepatitis B and T cell leukemia virus
type 1 can cause cancer of the cervix, liver and leukocytes (leukemia). Tyrosine kinases
regulate many cellular processes which can contribute to cancer development and
progression. KRAS is the oncoprotein that is most commonly activated in human
cancer. RAS is one of the most commonly mutated genes in human cancers. Oncogenes
code for oncoproteins, which are upregulated in cancer. Another important oncogene is
PI3K, which codes for the enzyme PI3K (phosphoinositide 3-kinase). The enzyme
PTEN (phosphatase and tensin homolog) catalyzes the opposite reaction, so it is a tumor
suppressor and the gene coding for it is downregulated in cancer. Human epidermal
growth factor (hEGF, or HER), vascular endothelial growth factor, or VEGF, and the
PI3K/AKT/mTOR (mammalian target of rapamycin) survival pathway are all important
therapeutic target in many cancers. Cancer stem cells could be good targets for new
drugs that will prevent the recurrence and metastasis of tumors. Also, induced
pluripotent stem cells could be used to screen drugs to see if they will be effective in
treating each individual patient.
Keywords: Cancer, human papilloma virus, tyrosine kinase, RAS, PI3K, VEGF,
HER, mTOR.
