Polyphyllin I Orchestrates Autophagy to Reprogram the Tumour Immune Microenvironment and Abrogate Cisplatin Resistance in Non-Small Cell Lung Cancer.

OBJECTIVE

This study aims to elucidate the molecular mechanisms by which Polyphyllin I (PPI), a potent steroidal saponin, attenuates non-small cell lung cancer (NSCLC) progression via mechanistic reprogramming of an autophagy-dependent immunogenic response.

METHODS

Integrated in vitro (A549, H460) and in vivo (LLC xenograft) models were deployed to evaluate PPI's efficacy on autophagic flux and the tumour immune microenvironment. The regulatory role of autophagy in macrophage-mediated antigen presentation was scrutinised via ATG3-mediated genetic silencing or overexpression in tumour-macrophage co-culture systems. Concurrently, the capacity of PPI to sensitise NSCLC cells to cisplatin (DDP) and counteract chemoresistance was evaluated.

RESULTS

PPI activated the AMPK/p53/mTOR signalling axis, robustly inducing core autophagic markers (LC3-II and Beclin-1) in a dose-dependent manner. Mechanistically, PPI-induced autophagic flux served as a prerequisite for antitumoural M1 macrophage polarisation, characterised by significant upregulation of iNOS and MHC-II in co-cultured THP-1 cells. Genetic knockdown of ATG3 effectively abrogated these immunostimulatory profiles, whereas ATG3 overexpression potentiated PPI-driven antigen presentation. Furthermore, PPI administration markedly delayed the onset of DDP resistance sustained by functional autophagic flux. In vivo, PPI significantly suppressed tumour burden, accompanied by enhanced CD8+ T-cell infiltration and elevated cytotoxic effector levels (IFN-γ and Granzyme B).

CONCLUSION

Our findings establish PPI as a dual autophagic-immune modulator that re-engineers the immunosuppressive microenvironment. By coupling intracellular autophagic stress with macrophage-mediated antigen presentation, PPI reinstates antitumour immunity and abrogates chemoresistance, offering a compelling therapeutic framework for managing recalcitrant NSCLC.