Which of the following agents are considered cell cycle nonspecific?

Cell cycle nonspecific agents are those that exert their effects on cancer cells regardless of the phase of the cell cycle. Alkylating agents and antitumor antibiotics belong to this category.

Alkylating agents work by damaging DNA, which can lead to cell death. They can affect cells that are in various stages of the cell cycle, including resting (G0) and cycling cells. This broad range of activity makes them effective against tumors that may not be actively dividing at the time of treatment.

Antitumor antibiotics also act in a way that is not restricted to a specific cell cycle phase. They interfere with DNA and RNA synthesis, thereby inducing apoptosis and stopping cell division. This means that they can target cells effectively, even when they are not in the active phases of the cell cycle.

In contrast, other classes of agents are specific to certain stages of the cell cycle. For example, plant alkaloids primarily target the M phase (mitosis), and antimetabolites target the S phase (DNA synthesis). Hormones usually work on specific molecular targets and are not considered cell cycle nonspecific either.

Thus, the pairing of alkylating agents and antitumor antibiotics accurately reflects the nature of cell cycle nonspecific agents.