MEDINET Co., Ltd.

The success of immune checkpoint blockade has unequivocally demonstrated that anti-tumor immunity plays a pivotal role in cancer therapy. Because endogenous tumor-specific T-cell responsiveness is essential for the success of checkpoint blockade, combination therapy with cancer vaccination may facilitate tumor rejection. To select the best vaccine strategy to combine with checkpoint blockade, we compared dendritic cell-based vaccines (DC-V) with peptide vaccines for induction of anti-tumor immunity that could overcome tumor-induced immunosuppression. Using B16 melanoma and B16-specific TCR-transgenic T-cells (pmel-1), we found that DC-V efficiently primed and expanded pmel-1 cells with an active effector and central memory phenotype that were not exhausted. Vaccine-primed cells were metabolically distinct from naïve cells. DC-V-primed pmel-1 cells contained the population that shifted metabolic pathways away from glycolysis to mitochondrial oxidative phosphorylation. They displayed better effector function and proliferated more than those induced by peptide vaccination. DC-V inhibited tumor growth in prophylactic and therapeutic settings. Only DC-V but not peptide vaccine showed augmented anti-tumor activity when combined with anti-PD-1 therapy. Thus, DC-V combined with PD-1 checkpoint blockade mediates optimal anti-cancer activity in this model.

Dendritic cell (DC)-based vaccines prepared using various antigen loading methods have been studied for cancer immunotherapy. The in vivo provocation of immunity by the direct injection of DCs without using tumor-specific antigens into tumors after apoptosis-inducing chemotherapy is more applicable. We previously reported that zoledronate-pulsed DCs (Zol-DCs) may induce tumor-antigen-specific CD8+ T cells by activating Vγ9γδT cells. In this report, we studied the feasibility, safety, and efficacy of a comprehensive immunotherapy involving the combined intratumoral injection of Zol-DC, gemcitabine (GEM) and αβT cells in locally advanced pancreatic carcinoma. Seven of 15 patients showed a stable disease (SD) and most of the patients showed long-term clinical responses. The FACT-BRM score was significantly higher in the patients with SD. Additionally the CD8+/Treg ratio significantly increased in SD patients after treatment. The median over-all survival and progression-free-survival of 15 patients were 12.0 months and 5.5 months, respectively. Patients with a pretreatment neutrophil/lymphocyte ratio (NLR) lower than 5.0 showed significantly longer survival. Even in an analysis limited to the patients with an NLR lower than 5.0, the patients whose CD8+/Treg ratio increased more than twofold tended to survive longer. In conclusion, the comprehensive immunotherapy using Zol-DCs, systemic αβT cells, and GEM may synergistically show a therapeutic effect on locally advanced pancreatic carcinoma. By using appropriate and precise biomarkers, such as NLR and CD8+/Treg ratio, the present comprehensive immunotherapy could be more beneficial for patients with pancreatic carcinoma.

We investigated the effect of gemcitabine (GEM), a key drug for pancreatic cancer treatment, on the expression of cell surface MICA/B in pancreatic cancer cells and resulting cytotoxicity of γδ T cells. We assessed the effect of GEM on the upregulation of cell surface MICA/B expression by flow cytometry, utilizing six pancreatic cancer cell lines. MICA and CD16 expressions from resected pancreatic cancer patient specimens, which received neoadjuvant chemotherapy (NAC) with GEM, were analyzed by immunohistochemistry. GEM could increase MICA/B expression on cell surface in pancreatic cancer cell lines (in 2 of 6 cell lines). This effect was most effectively at concentration not affecting cell growth of GEM (0.001 μM), because MICA/B negative population was appeared at concentration at cytostatic and cytotoxic effect to cell growth (0.1 and 10 μM). The cytotoxic activity of γδ T cells against PANC-1 was detected and functions through interactions between NKG2D and MICA/B. However, the enhancement of NKG2D-dependent cytotoxicity with increased MICA/B expression, by GEM treatment, was not observed. In addition, soluble MIC molecules were released from pancreatic cancer cell lines in culture supernatant with GEM treatment. Immunohistochemical staining demonstrated that MICA expression in tumor cells and CD16 positive cells surrounding tumors were significantly higher in the NAC group compared to that of the control group. There was a significant correlation between NAC and MICA expression, as well as NAC and CD16 positive cell expression. The present results indicate that low-dose GEM-induced MICA/B expression enhances innate immune function rather than cytotoxicity in pancreatic cancer. In addition, our result suggests that the inhibition of cleavage and release of MIC molecules from the tumor surface could potentially improve NKG2D-dependent cytotoxicity.