PI3K/mTOR inhibition attenuates cigarette smoke-induced senescence and SASP in oral fibroblasts: implications for tumor microenvironment remodeling

BACKGROUND: Cigarette smoke exposure is a major risk factor for oral cancer, partly due to its ability to induce early molecular alterations in the oral mucosa. Cellular senescence and the senescence-associated secretory phenotype (SASP) contribute to chronic inflammation and microenvironmental remodeling, favoring carcinogenesis. The PI3K/AKT/mTOR pathway has been implicated in sustaining SASP and senescence, suggesting that its inhibition may represent a promising preventive strategy. METHODS: Primary human oral fibroblasts (hOF) and a 3D oral mucosa model were exposed to cigarette smoke extract (CSE) 2% for 72 h, with or without pre-treatment with the dual pan-class I PI3K/mTOR inhibitor PKI402 (10⁻⁷-10⁻⁹ M). Senescence markers (p21, p16, lamin B1) were quantified by RT-qPCR; SASP cytokines (IL-6, IL-8) by ELISA; DNA damage by γH2AX immunofluorescence; and senescence-associated β-galactosidase (SA-β-gal) activity by flow cytometry. RESULTS: CSE exposure induced a senescent phenotype characterized by increased p21 and p16, decreased lamin B1, elevated IL-6 and IL-8 secretion, accumulation of γH2AX foci, and enhanced SA-β-gal activity. PKI402 significantly attenuated these changes in a dose-dependent manner, with the highest concentrations showing statistically significant reductions across all endpoints. CONCLUSION: Pharmacological inhibition of PI3K/mTOR mitigates cigarette smoke-induced senescence and SASP in oral fibroblasts, reducing DNA damage and inflammatory signaling. These findings highlight PI3K/mTOR pathway as a potential target for senomorphic interventions aimed at preventing pro-tumorigenic microenvironment remodeling in oral carcinogenesis.