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.