What enzyme is inhibited by etoposide –
**Core Concept**
Etoposide is a chemotherapeutic agent that belongs to the class of topoisomerase inhibitors. It works by interfering with the enzyme topoisomerase II, which is essential for DNA replication and cell division. Inhibiting this enzyme leads to DNA damage and ultimately causes cell death.
**Why the Correct Answer is Right**
Etoposide specifically inhibits the activity of topoisomerase II by stabilizing the cleavage complex, which is formed when the enzyme binds to DNA and creates a temporary break. This prevents the enzyme from religating the DNA strands, leading to DNA fragmentation and cell death. The inhibition of topoisomerase II by etoposide results in the accumulation of DNA damage, which triggers apoptosis in cancer cells.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because etoposide does not inhibit topoisomerase I, which is another enzyme involved in DNA replication and repair.
**Option B:** This option is incorrect because etoposide does not inhibit DNA polymerase, which is an enzyme involved in DNA replication and repair.
**Option C:** This option is incorrect because etoposide does not inhibit DNA ligase, which is an enzyme involved in DNA repair and replication.
**Clinical Pearl / High-Yield Fact**
Topoisomerase II inhibitors like etoposide are often used in combination with other chemotherapeutic agents to treat various types of cancer, including leukemia, lymphoma, and solid tumors. It's essential to note that etoposide can cause myelosuppression, which is a decrease in the production of blood cells, making it a critical side effect to monitor in patients receiving this medication.
**Correct Answer:** D. Topoisomerase II.