Cepharanthine triggers immunogenic cell death in solid tumors by suppressing protein kinase C zeta-mediated poly(ADP-ribose) polymerase 1 expression and synergizes with immunotherapy.

Immunogenic cell death (ICD) represents a promising strategy to suppress tumor growth and potentiate immunotherapy efficacy, driving the demand for novel and clinically translatable ICD inducers. Here, we investigated the potential of cepharanthine (CEP) for inducing ICD in multiple representative solid tumors. The ICD-inducing potential of a series of natural alkaloids was screened by flow cytometry. CEP's activity and mechanism were characterized using flow cytometry, western blot, immunofluorescence, ATP quantification, cell thermal shift assay (CETSA), surface plasmon resonance (SPR), bulk and single-cell RNA sequencing.

The translational potential of CEP, either as monotherapy or in combination with other immunotherapies, was evaluated in both syngeneic mouse tumor models and patient-derived organoid systems. Toxicity in mice was assessed through hematological and biochemical parameters. CEP effectively induced ICD in multiple representative solid tumor models (breast cancer, colorectal cancer, esophageal cancer, liver cancer, lung cancer) by promoting damage-associated molecular patterns (DAMPs) release, enhancing phagocytosis by antigen-presenting cells, and activating T cell-mediated immunity. Mechanistically, CEP directly bound to protein kinase C zeta (PKCζ), leading to the inhibition of NF-κB signaling via suppressing p65 nuclear translocation, and downregulation of poly ADP-ribose polymerase 1 (PARP1) transcription.

PARP1 downregulation triggers intracellular reactive oxygen species (ROS) accumulation, subsequently inducing DNA damage and endoplasmic reticulum (ER) stress.

Furthermore, CEP synergized with PD-1 blockade and OX40 agonism, thereby enhancing antitumor efficacy in vivo. CEP is a potent and preclinically well-tolerated ICD inducer that acts by targeting the PKCζ/NF-κB/PARP1 axis. Its synergy with immune checkpoint inhibitors and co-stimulatory agonists underscores its translational potential for combination cancer immunotherapy.