Cancer cells differ from normal cells in terms of their rapid cell division and their ability to spread (metastasis). Many proteins regulate the cell cycle, either positively (oncogenes) or negatively (tumor suppressors). In cancer, one or more of these proteins is altered in some way, making its activity abnormal. Radiation and many cancer drugs target genes and proteins involved in the cell cycle.
learning outcomes
You should be able to:
Compare and contrast cancer cells and normal cells.
Explain how regulation of the cell cycle can become disrupted in cancer cells.
Justify the rationale for targeting events in the cell cycle as a means of treating cancer.
Compare cells and genes in normal tissue, malignant tumors, and benign tumors.
Normal cells: have control over cell division; stay in tissue and do not migrate. Malignant tumor cells: lose control over cell division; migrate to other places in the body. Benign tumor cells: lose control over cell division and then at some point stop dividing; do not migrate to other parts of the body.
How are oncogene proteins and tumor suppressor proteins involved in cell cycle control in normal and cancer cells?
In normal cells, oncogene products are not active or are made in low amounts, while in cancer cells oncogene products are made in larger amounts or mutated forms, and these act to stimulate the cell cycle. In normal cells, tumor suppressor gene products are made and are active at blocking the cell cycle. In cancer cells, tumor suppressor gene products are either mutated to be nonfunctional or are not made, and in either case are not active in blocking cell division, so cells divide and form tumors.
Cancer-
Cancer cells are not synchronous in the cell cycle. At a given point in time, some are in G1, some in S, and so on. So targeting all the phases might be better than targeting just one.
We have now looked at the cell cycle and at cell division by binary fission, mitosis, and meiosis. We have described the normal cell cycle and how its regulation is disrupted in cancer. We have seen how meiosis produces haploid cells in sexual life cycles. In the coming chapters we will examine heredity, genes, and DNA.