Question

How cell cycle regulation relates to cancer?

Answer 1

Cell cycle is the ordered sequence of events that takes place prior to cell division. It helps the cell to prepare for the cell division leading to the formation of two daughter cells.

Complete answer:
The cell cycle is broadly classified into the interphase and the Mitotic or M phase. The interface comprises about 90% of the total time of the cell cycle and is made of three phases- G1,S and G2. The G1 phase is the phase where the cell increases synthesis of its proteins, increases its organelles and also grows in size.

The G1 phase also comprises a checkpoint which ensures that only those cells that are prepared to divide leaves the G1 phase and enters the S phase. The S phase or Synthesis phase is where DNA replication takes place. The rate of transcription and translation are quite low during this phase. The G2 phase follows S phase, here the protein synthesis increases and the cell prepares itself for mitosis. The G2 phase also consists of a checkpoint which ensures only those cells that are prepared for division enters into the M phase. The M phase is where cell division takes place leading to the formation of two daughter cells that receive equal amounts of genetic material from the parent cell.

Cancer can be described as the condition in which the cell divides continuously without any stop signal. The defects in the cell cycle arise due to incomplete or faulty DNA replication or non formation of proper mitotic apparatus. As we have already discussed that the checkpoints in the cell cycle can sense defects and block the progression through the cell so that apoptosis can take place. In case of cancer checkpoints are absent or nonfunctional and an unregulated cell cycle takes place. The cell cycle rather than going to the apoptotic stage moves to the S phase and divides indefinitely.

Note: Apart from the above-mentioned checkpoints there are two other proteins that regulate cell cycle- cyclins and cyclin dependent kinases. So any mutation in these proteins also has an affect on the cell cycle and can be a cause of cancer.