NTRK1 and neoplasm: Cytotoxic chemotherapy works mainly by interfering with cell division (mitosis) and can be classified as: (1) alkylating agents, which stop tumor growth by crosslinking guanine nucleobases in DNA double-helix strands; (2) antimicrotubule agents, which block cell division by preventing microtubule function; (3) topoisomerase inhibitors, which block growth signals associated with receptor tyrosine kinases; (4) cytotoxic antibiotics, which interrupt cell division; and (5) antimetabolites, which impede DNA and RNA synthesis.