FASN at the crossroads of tumor metabolism, immune evasion, and therapy resistance: Mechanistic insights and therapeutic opportunities.

Fatty acid synthase (FASN), the key enzyme driving de novo lipogenesis, has emerged as a central metabolic hub in cancer, linking aberrant lipid synthesis to tumor progression, immune escape, and therapy resistance. This review provides a comprehensive overview of the regulatory landscape and oncogenic functions of FASN, highlighting its modulation at transcriptional, post-transcriptional, and post-translational levels. We discuss how FASN-driven lipid remodeling supports tumor proliferation, disrupts antigen presentation, alters immune cell metabolism, and suppresses ferroptosis, thereby enabling resistance to chemotherapy, radiotherapy, targeted therapy, and immune checkpoint inhibitors. Emerging therapeutic strategies-including direct FASN inhibition, targeting upstream regulators, and rational metabolic-immune-ferroptosis combinatorial regimens-are explored in the context of precision oncology. Given the metabolic plasticity of cancer cells and the heterogeneous response of the tumor immune microenvironment, future advances will rely on dynamic biomarker-guided therapy and spatiotemporal profiling of FASN activity. Together, these insights position FASN not merely as a metabolic enzyme but as a versatile therapeutic axis at the intersection of cancer metabolism, immunity, and resistance.