NR4A1 and neoplasm: Traditional chemotherapeutic agents (e.g., alkylating agents, antimetabolites) exert direct cytotoxic effects; however, many contemporary small-molecule drugs-such as kinase inhibitors and hormone receptor modulators-act through targeted inhibition of oncogenic signaling, and immunotherapies (e.g., checkpoint inhibitors) function by enhancing endogenous anti tumor immunity rather than directly damaging tumor cells, as cytotoxic agents do.