What is the main action of chemotherapy drugs on cells in the M phase?

Chemotherapy drugs are designed to target rapidly dividing cells, particularly those in specific phases of the cell cycle. During the M phase, which is the mitotic phase of the cell cycle, cells undergo division. The main action of chemotherapy drugs at this stage is to prevent cell division. By interfering with the processes that allow a cell to divide, these drugs can halt the proliferation of cancer cells.

Preventing cell division is critical in the context of cancer treatment because it stops the growth and spread of tumors. Many chemotherapy agents disrupt the formation of the mitotic spindle, which is essential for the separation of chromosomes, or inhibit other key processes involved in mitosis. This targeted action is fundamental in cancer therapy, as it specifically disrupts the growth of neoplastic cells, which tend to divide more rapidly than normal cells.

In contrast, promoting cell division, enhancing DNA replication, or increasing cell growth would not align with the therapeutic goals of chemotherapy, which aim to control and reduce cancer cell growth rather than facilitate it.