ASAP VI Oncology Practice Test 2025 - Free Oncology Practice Questions and Study Guide

The correct answer highlights that topoisomerase II inhibition primarily affects the M phase of the cell cycle, which is when mitosis occurs. During the M phase, the cell is actively dividing, and topoisomerase II plays a critical role in managing the DNA topology that arises from the replication process. It helps in unwinding the DNA strands to facilitate proper segregation of chromosomes.

When topoisomerase II is inhibited, the necessary processes for DNA replication and chromosome separation during mitosis are disrupted, leading to errors in cell division. This can subsequently trigger cell death or halt the progression of the cell cycle. Understanding that topoisomerase II is primarily active during the M phase clarifies why inhibiting its function has significant implications for cells that are dividing actively, making its inhibition an effective strategy in certain cancer therapies which target rapidly dividing tumor cells.

The other phases, such as G1, S, and G2, involve different cellular activities and processes that do not directly utilize topoisomerase II to the same extent as the M phase does, thereby making them less relevant in the context of topoisomerase II inhibition.