Types of Chemotherapy

Besides being classified as cell cycle specific or non-specific agents, cytotoxic drugs are also classified based on their biochemical structure and mechanism of action.

Alkylating agents (AA) are highly reactive, cytotoxic, cell cycle non-specific compounds that inhibit cell replication by bonding to DNA, RNA and proteins in all phases of the cell cycle.

Platinum based compounds work in a similar way by bonding with purine bases on the DNA molecule; blocking DNA repair mechanisms, causing DNA damage, and inducing apoptosis.

Antimetabolites are biochemical imposters that compete with the physiologic molecules necessary for normal cell function and replication. They often act by damaging DNA, corrupting RNA or impeding key enzymatic reactions.

Antitumor antibiotics interfere with DNA synthesis by: 1) intercalating between DNA base pairs, 2) inhibition of topoisomerase enzymes, 3) production of oxygen free radicals, 4) causing protein:DNA crosslinks.

Plant alkaloids

• Topoisomerase I inhibitors cause single DNA strand breaks
• Epipodophyllotoxins poison topoisomerase II resulting in DNA strand breaks
• Taxanes cause abnormal mitosis through centrosomal impairment and suppression of spindle microtubule dynamics.
• Vinca alkaloids cause disassembly of microtubules, blocking mitotic progression

Hormones and antagonists are used to treat hormone-sensitive tumors, like estrogen sensitive breast cancer tumors. Hormone-sensitive tumors may be hormone-dependent, hormone responsive, or both. A hormone-dependent tumor regresses on removal of the hormonal stimulus. Hormone-responsive tumors regress when pharmacologic amounts of hormones are administered.

Biological Cancer Therapies include: Immunotherapy, Oncolytic Viral Therapy, Monoclonal Antibodies and Cytokines