Etoposide acts by –
**Core Concept**
Etoposide is a chemotherapeutic agent that works by inhibiting the enzyme topoisomerase II, which is involved in DNA replication and repair. This inhibition leads to DNA damage and ultimately cell death, particularly in rapidly dividing cancer cells.
**Why the Correct Answer is Right**
Etoposide binds to the topoisomerase II-DNA complex, preventing the enzyme from religating the DNA strands after they have been temporarily broken. This results in DNA strand breaks and subsequent activation of apoptosis (programmed cell death). The enzyme topoisomerase II is essential for the unwinding of DNA during replication and transcription, making it a critical target for etoposide.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the mechanism of action of etoposide.
**Option B:** Etoposide does not act by inhibiting DNA polymerase, which is involved in DNA replication and repair.
**Option C:** Etoposide's mechanism of action is not related to the inhibition of microtubule dynamics, which is relevant to agents like taxanes.
**Clinical Pearl / High-Yield Fact**
Etoposide is often used in combination with other chemotherapeutic agents, such as cisplatin and vincristine, to treat a range of cancers, including testicular cancer, lung cancer, and lymphomas. It is also used in the treatment of certain leukemias.
**Correct Answer:** C. Inhibiting topoisomerase II.