Disulfiram combined with chemoimmunotherapy potentiates pancreatic cancer treatment efficacy through the activation of cGAS-STING signaling pathway via suppressing PARP1 expression

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related mortality globally with limited effective treatment options. Although the combination of immunotherapy and chemotherapy has been attempted in clinical trials to treat PDAC, the results are not promising. Therefore, in this study, we explored the application of a novel combination strategy with disulfiram (DSF) to enhance the treatment efficacy of PDAC as well as its underlying molecular mechanism. We compared the antitumor effects between single agents and the combination therapy by using mouse allograft tumor model and found DSF combined with chemoimmunotherapy significantly suppressed the growth of subcutaneous PDAC allograft tumor in mice and prolonged the survival of mice. To further investigate the alterations in the immune microenvironment of tumors from different treatment groups, we employed flow cytometry and RNA-seq analysis to examine the composition of tumor-infiltrating immune cells as well as the expression level of a variety of cytokines. Our results revealed that the proportion of CD8 T cells was notably elevated and that multiple cytokines were upregulated in the combination therapy group. Furthermore, qRT-PCR results indicated that DSF could upregulate the mRNA levels of IFNα and IFNβ, which could be reversed by STING pathway inhibitor. Mechanistically, we found that DSF activated STING signaling pathway through Poly (ADP-ribose) polymerases (PARP1) inhibition. Taken together, our findings highlight the potential clinical application of this novel combination strategy using DSF and chemoimmunotherapy in the treatment of patients with PDAC.

PARP1; PD1 inhibitor; Pancreatic ductal adenocarcinoma; cGAS-STING signaling pathway; chemotherapy; disulfiram; immunotherapy.