Final answer:
Methotrexate treats acute lymphocytic leukemia by inhibiting folic acid reductase required for DNA synthesis in cancer cells, thereby preventing their division and proliferation. Serious adverse effects include damage to rapidly dividing normal cells, leading to hair loss, digestive issues, and blood cell depletion.
Step-by-step explanation:
Methotrexate works to kill cancer cells in the treatment of acute lymphocytic leukemia (ALL) by inhibiting the enzyme folic acid reductase, which is essential for the conversion of folic acid to tetrahydrofolic acid. This inhibition results in the prevention of DNA synthesis, as tetrahydrofolic acid is needed for one-carbon transfer reactions that are critical in the synthesis of purines and pyrimidines, which are the building blocks of DNA. Without DNA synthesis, cancer cells cannot divide and proliferate, leading to their death.
The most serious adverse effects from high-dose methotrexate include damage to normal dividing cells, such as those in the intestinal lining, hair follicles, and bone marrow, leading to side effects like hair loss, digestive system issues, and depletion of blood cells. The success of methotrexate and combination chemotherapy, where several drugs are used concurrently, like the POMP regimen for ALL, relies on the rapid proliferation of cancer cells compared to normal cell types.