Uncontrolled mitosis causes cell division due to various factors external and internal to the cell. Uncontrolled mitosis causes tumors and cancer in the body. The process of tumor formation is called oncogenesis. Causes of uncontrolled mitosis or cancer are mentioned.
- Cell cycle control system: Abnormalities in the cell cycle control system lead to uncontrolled growth of cells and tumor or cancer.
(i) Dysregulation of cyclin-CDK complex in cells leads to uncontrolled mitosis and cancer.
(ii) p53 protein arrests the cell cycle when the cell’s DNA is damaged. If the p53 protein is defective for any reason, cell cycle control is lost. As a result, cancer occurs. This is probably one of the reasons for the high rate of cancer in humans.
(iii) Some growth factors act for cell division. Cancer cells themselves produce growth factors. Due to this, cell division accelerates and cancer occurs.
(iv) Two types of proteins that regulate the cell cycle are kinase proteins and cyclin proteins. Cancer occurs when protein kinases and cyclin proteins fail to control the cell cycle.
- Proto-Oncogene: Genes that create positive cell cycle regulators in the body are called proto-oncogenes. Proto-oncogenes become oncogenes due to mutations. Oncogenes cause cell cycle disruption and cancer. CDK is a proto-oncogene.
- Papilloma virus: Different types of papilloma virus help to cause cancer. Papillomaviruses contain B6 and B7 genes. This gene displaces two proteins that regulate cell division. It destroys the normal cell division ability. The result is the formation of tumors that can later turn into cancer.
- Tumor suppressor genes: Tumor suppressor genes are negative cell cycle regulatory genes. It prevents the uncontrolled growth of cells. Stops the formation of tumors and cancer in the body.
- Carcinogenic agents: All substances or agents that cause cancer in the body are called carcinogenic agents. Carcinogenic agents like UV rays, cigarette tar, X-rays etc. These substances cause mutations or changes in genes. Mutagenic genes cause cancer.
- Metastasis: The spread of cancer cells to different parts of the body is called metastasis. Malignant tumor cells that cause cancer spread through the blood and lymph to different parts of the body and form new tumors. Cancer formation is accelerated due to metastasis.
- Cell Death: Cell death occurs in two ways. Necrosis and apoptosis. Cell death due to lack of nutrients or toxic substances is called necrosis. Apoptosis is the process of death of unnecessary cells or organs in the body. Apoptosis is the destruction or death of tissue between human fingers. Apoptosis causes red blood cells, white blood cells and platelets to die after a certain period of time.
- Cancer: The meaning of the word Cancer is crab. Cancer cells look like crab legs when they spread around. Dysregulation of cyclin-cdk in cancer cells. Cancer cells make their own growth factors or do not need growth factors for cell division. Hence the possibility of cancer increases.
- Mitotic index: The ratio of the total number of cells present in a tissue to the number of cells undergoing mitosis is called the mitotic index (MI). Cancer cells have a higher mitotic index than normal cells.