Cancer Flashcards
Define cancer.
Uncontrolled cell division/growth.
What are some characteristics specific to cancer cells?
- Lost the need for growth factors –> can divide whether or not these factors are present.
- Loss of contact inhibition –> cells continue to grow and divide after they touch other cells (a large mass forms as a result)
- Telomerase is activated –> unlimited number of cell divisions without triggering apoptosis (“immortal cell”)
- Continued division even when DNA is damaged.
What are the genes involved in cancer?
2 broad categories:
- Proto-oncogenes
- Tumor suppressor genes
What are proto-oncogenes?
Proto-oncogenes are genes that trigger cell division when appropriate. Proto-oncogenes code for proteins that stimulate cell division.
Explain the function of the normal and mutated ras (G) protein
The ras protein is associated with the cytoplasmic surface of a membrane receptor and plays a role in cell signaling. When GDP is bound, ras is inactive. When GTP is bound, ras is active.
In mutated ras protein –> GTP is not ever hydrolysed to GDP, thus protein remains active (called hyperactive ras), and results in more cell division
What are tumor suppressor genes?
Tumor suppressor genes code for proteins that send appropriate signals to prevent cell division or lead to cell death (apoptosis)
Explain the function of the normal and mutated p53 gene
The p53 gene codes for p53 protein, which is a transcription factor that can directly bind to DNA in the nucleus. It can activate DNA repair proteins, arrest the cell cycle (at G1 checkpoint), initiate programmed cell death.
The mutated p53 gene codes for a non-functional protein, that can no longer bind to the DNA and hence can no longer carry out its function.
What is a gain-in-function mutation?
A mutation that involves a cell gaining a new function that wasn’t present in the original cell.
What is a loss-in-function mutation?
A mutation wherein the mutation results in the formation of a non-functional protein, therefore leading to a loss of function.
Why is cancer development a multi-step process?
Cells control proliferation at several checkpoints, which all need to be inactivated in order for cancer to be initiated.
Cancer development involves the accumulation of (around 4 to 6) independent mutations in key cell-cycle regulatory genes.
Explain how malignant tumors develop.
- Initially benign tumors that lack the ability to invade or spread to other tissues.
- Through the accumulation of mutations over time, cells in tumor may gain the ability to invade normal tissues and migrate to other parts of the body.
- Can also induce angiogenesis
What is angiogenesis?
Angiogenesis is the formation of new blood vessels. These vessels play a role in supplying nutrients and oxygen to the growing tumor at the new site.
What are the INTERNAL causative factors of cancer?
- Loss of immunity
- Genetic predisposition
- Hormones (presence/absence)
What are the EXTERNAL causative factors of cancer?
What is metastasis?
The process by which cancer cells spread to other parts of the body. (by infiltrating the circulatory system)
