Orlistat combined with everolimus suppresses pancreatic neuroendocrine tumor progression via inhibiting PI3K/AKT/mTOR signaling mediated by SLFN5.

Pancreatic neuroendocrine tumors (PanNETs) are characterized by limited therapeutic options and frequent resistance to monotherapies such as everolimus. Targeting metabolic pathways alongside mTOR signaling may improve treatment efficacy. This study aimed to investigate the synergistic antitumor effects of orlistat, a fatty acid synthase inhibitor, combined with everolimus in PanNETs and to elucidate the underlying molecular mechanisms. In vitro assays, including CCK-8, colony formation, EdU incorporation, and western blotting, were performed on PanNET cell lines. In vivo efficacy and safety were evaluated using subcutaneous xenograft mouse models. Transcriptomic profiling and functional studies of SLFN5 were conducted to uncover its regulatory role in PI3K/AKT/mTOR signaling and drug response. Orlistat and everolimus exhibited a significant synergistic inhibitory effect on PanNET cell proliferation. The combination markedly suppressed tumor growth in vivo without evident toxicity. RNA sequencing revealed distinct transcriptomic changes and highlighted SLFN5 as a key downregulated gene in PanNETs. Functional assays demonstrated that SLFN5 overexpression inhibited tumor growth and enhanced drug sensitivity by negatively regulating the PI3K/AKT/mTOR pathway. Conversely, SLFN5 knockdown impaired the antitumor efficacy of the drug combination. In conclusion, the combination of orlistat and everolimus represents a promising therapeutic strategy for PanNETs, with SLFN5 serving as a critical mediator and potential biomarker for treatment efficacy.