Abstract 1330: The influence of anticancer agents and heat treatment on PD-L1 expression on human and murine pancreatic cancer cell lines

Field: Medicine (Health Sciences)

Abstract Background: Pancreatic ductal adenocarcinoma (PDA) is one of the most lethal malignancies. Currently conducted chemotherapy for PDA didn't get the sufficient clinical results, so we need to get new strategy for PDA therapy immediately. For breaking through this situation, the inhibitors of immune checkpoint PD-1/PD-L1 are hopeful candidates because PD-1/PD-L1 inhibitors relatively got the good results for some advanced malignancies including PDA, but the sole therapy doesn't result in good outcome. In murine model, the combination therapy of PD-L1 inhibitor and gemcitabine has been reported to show a synergistic effect on PDA compared to each sole therapy. But the mechanism of the synergistic effect is not well understood. On the other hand, we have previously demonstrated the efficacy of the combined therapy of regional heat treatment and gemcitabine in advanced PDA patients, but the effect of heat treatment on immune checkpoint is also unknown. Then, for future combination therapy of anticancer agents, immune check point inhibitor and heat treatment, we analyzed the influence of some anticancer agents and heat treatment on the expression of PD-L1 on pancreatic cancer cell lines. Methods: Human pancreatic cancer cell lines MIA PaCA-2, AsPC-1 and murine pancreatic cancer cell line Pan02 were used in this study. These cells were adjusted to 1.0 × 105 / ml and incubated with anticancer agents such as gemcitabine, paclitaxel and 5-fluorouracil at 37°C for 24 - 72 hours. For checking the influence of anticancer agents on the expression of PD-L1, their expression of PD-L1 was examined by flow cytometry and qRT-PCR. Next, before exposing cancer cells to gemcitabine, MIA PaCA-2 and AsPC-1 were incubated at 43°C as heat treatment. After the heat treatment, PD-L1 expression was analyzed using flow cytometry. Results: In AsPC-1 and Pan02, PD-L1 expression was enhanced with all three anticancer agents in concentration dependency by both flow cytometry and qRT-PCR. In MIA PaCA-2, PD-L1 expression was enhanced with all three anticancer agents by flow cytometry analysis, but the result of qRT-PCR could not show the difference. PD-L1 expression on MIA PaCA-2 and AsPC-1 with heat treatment was suppressed compared to only anticancer agent treatment. Conclusion: The stimulation of anticancer agents tends to lead to an enhancement of PD-L1 expression on both human and murine pancreatic cancer cell lines. The synergistic effect of PD-L1 inhibitor and gemcitabine has the possibility to be brought about by PD-L1 up-regulation. On the other hand, heat treatment has the possibility to suppress PD-L1 expression and this mechanism might lead to cancel out the immune tolerance caused by anticancer agent administration with up-regulation of PD-L1. For future, we need to further examine the most effective timing and method of combined therapy of anticancer agent, PD-L1 inhibitor and heat treatment. Citation Format: Toshifumi Doi, Tetsuya Okayama, Takeshi Ishikawa, Kaname Oka, Naoyuki Sakamoto, Tomoyo Yasuda, Yuji Naito, Yoshito Itoh. The influence of anticancer agents and heat treatment on PD-L1 expression on human and murine pancreatic cancer cell lines. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1330. doi:10.1158/1538-7445.AM2015-1330