Which antitumor antibiotic is known to be cell cycle specific?

Bleomycin is the antitumor antibiotic known for its cell cycle specificity, particularly its action during the G2 phase of the cell cycle. This phase is when the cell prepares for mitosis, and bleomycin works effectively by causing breaks in DNA and preventing the cells from successfully dividing.

This action is critical in cancer treatment, as it targets and interrupts the replication of rapidly dividing cancer cells, which are highly dependent on this phase for their proliferation. By being specific to the G2 phase, bleomycin can selectively affect tumor cells while minimizing effects on cells that are not actively dividing, contributing to a more favorable side effect profile compared to some other chemotherapy agents.

In contrast, other antitumor antibiotics have broader activity across various phases of the cell cycle. Doxorubicin and Actinomycin D, for example, act on dividing cells but do not have the same level of specificity for a particular phase, while Mitomycin C has a different mechanism of action and does not warrant the same classification. This specificity of bleomycin is what differentiates it in the context of cell cycle specific therapies.