What is a folate analog and an antimetabolite commonly used in oncology?

The correct answer is methotrexate, which is a folate analog and an antimetabolite widely used in oncology. Methotrexate works by inhibiting the enzyme dihydrofolate reductase, which plays a crucial role in the synthesis of DNA, RNA, and proteins by blocking the conversion of dihydrofolate to tetrahydrofolate. This action disrupts the cell cycle, particularly affecting rapidly dividing cancer cells that rely heavily on folate for proliferation.

Due to its mechanism, methotrexate is effective in treating various cancers, including leukemia, lymphoma, and certain solid tumors, as well as being used in lower doses for autoimmune diseases like rheumatoid arthritis. Its classification as a folate analog is critical because it mimics natural folate, allowing it to be incorporated in metabolic pathways where folate is normally utilized.

In contrast, the other options listed do not serve as folate analogs. Cytarabine is a cytidine analog that primarily inhibits DNA synthesis and is used for hematologic malignancies. 5-Fluorouracil is a pyrimidine analog that interferes with RNA and DNA synthesis by disrupting the synthesis of thymidine. Gemcitabine is also a nucleos