Purpose: The establishment of a preclinical model of the abscopal effect on hepatocellular carcinoma (HCC) and evaluation of whether the hypofractionated radiation therapy (RT) multitumor Hepa1-6 mouse HCC model could be used to suppress nonradiated tumor mass was performed in this study.
Methods and materials: Hepa1-6 mouse liver cancer cell lines were used to form tumors. Immunogenicity was analyzed using ELISpot and immune cell labeled antibody. Interferon (IFN) β expression was confirmed through polymerase chain reaction.
Results: After investigation, the intratumoral transcription of type Ⅰ IFN increased by 2-fold. The antitumor immune response to Hepa 1-6 cells induced by radiation was increased. Moreover, the influx of activated CD8+ T cells was increased in nonirradiated tumors. The number of dendritic cells and activation status were evaluated by flow cytometry on the second day after irradiation. Flow cytometry revealed a significantly increased dendritic cell population expressing the CD11c molecule in tumor-draining lymph nodes. Furthermore, because irradiation leads to adaptation of immune resistance of tumor cells against RT, we sought to elucidate a potent tool to overcome the resistance and confirm the ability of PD-L1 antibody to survive late RT resistance.
Conclusions: The immunologic mechanism of the abscopal effect was revealed and the application of PD-L1 inhibitor successfully performed as a breakthrough in late RT resistance in the Hepa1-6 tumor model.
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