High-dose vitamin C augments LPS/IFN-γ-induced M1 macrophage polarization through JAK2-STAT1 activation and promotes anti-PD-1 efficacy in pancreatic cancer

Abstract High-dose vitamin C (HDVC) exhibits antitumor and immunomodulatory properties and may enhance the efficacy of immune checkpoint inhibitors (ICIs); however, its ability to reprogram the immunosuppressive tumor microenvironment (TME) in pancreatic cancer, particularly through modulating tumor-associated macrophage (TAM) polarization, remains unclear. In this study, the antitumor activity of HDVC was evaluated in a subcutaneous KPC mouse model, while in vitro models utilizing lipopolysaccharide (LPS) + IFN-γ-stimulated mouse and human macrophages were employed to investigate polarization. Mechanisms were probed by RNA sequencing, western blotting, flow cytometry, pharmacological inhibition, and siRNA-mediated JAK2 knockdown. Macrophage involvement was confirmed in vivo via clodronate liposome-mediated depletion, and the combinatory effect of HDVC with anti-PD-1 therapy was assessed. The results showed that HDVC significantly inhibited pancreatic tumor growth and prolonged survival in vivo. Mechanistically, HDVC enhanced LPS + IFN-γ-induced M1 macrophage polarization, at least in part through activation of the JAK2-STAT1 signaling pathway, without markedly increasing M2-associated features. The antitumor efficacy of HDVC was markedly attenuated upon macrophage depletion, supporting the involvement of macrophage-dependent immune modulation. Furthermore, HDVC enhanced the efficacy of anti-PD-1 therapy, accompanied by increased M1-like macrophages and CD8⁺ T-cell infiltration in the TME. These findings identify HDVC as a potential immunomodulator that remodels the immunosuppressive TME of pancreatic cancer through macrophage-centered immune remodeling, providing a rationale for further investigating HDVC-based combination strategies with ICIs in pancreatic cancer.