Combined Immunostimulatory Monoclonal Antibodies Extend Survival in an Aggressive Transgenic Hepatocellular Carcinoma Mouse Model

Abstract

Purpose: Immunostimulatory monoclonal antibodies (ISmAb) that unleash antitumor immune responses are showing efficacy in cancer clinical trials. Anti-B7-H1 (PD-L1) monoclonal antibodies (mAb) block a critical inhibitory pathway in T cells, whereas anti-CD137 and OX40 mAbs provide T-cell costimulation. A combination of these ISmAbs (anti-CD137 þ anti-OX40 þ anti-B7-H1) was tested using a transgenic mouse model of multifocal and rapidly progressing hepatocellular carcinoma, in which c-myc drives transformation and cytosolic ovalbumin (OVA) is expressed in tumor cells as a model antigen.Experimental Design: Flow-cytometry and immunohistochemistry were used to quantify tumorinfiltrating lymphocytes (TIL) elicited by treatment and assess their activation status and cytolytic potential. Tolerance induction and its prevention/reversal by treatment with the combination of ISmAbs were revealed by in vivo killing assays.Results: The triple combination of ISmAbs extended survival of mice bearing hepatocellular carcinomas in a CD8-dependent fashion and synergized with adoptive T-cell therapy using activated OVA-specific TCRtransgenic OT-1 and OT-2 lymphocytes. Mice undergoing therapy showed clear increases in tumor infiltration by activated and blastic CD8 þ and CD4 þ T lymphocytes containing perforin/granzyme B and expressing the ISmAb-targeted receptors on their surface. The triple combination of ISmAbs did not result in enhanced OVA-specific cytotoxic T lymphocyte (CTL) activity but other antigens expressed by cell lines derived from such hepatocellular carcinomas were recognized by endogenous TILs. Adoptively transferred OVA-specific OT-1 lymphocytes into tumor-bearing mice were rendered tolerant, unless given the triple mAb therapy. Conclusion: Extension of survival and dense T-cell infiltrates emphasize the translational potential of combinational immunotherapy strategies for hepatocellular carcinoma.

Combination of 4-1BB Agonist and PD-1 Antagonist Promotes Antitumor Effector/Memory CD8 T Cells in a Poorly Immunogenic Tumor Model

“…Modulation of stimulatory signals by 4-1BB, OX40, or GITR pathway is still in the early stages of clinical evaluation (30). In preclinical studies, combinations of immunomodulators as well as in combination with chemotherapy, targeted agents, vaccination or irradiation, have been evaluated in various models (15)(16)(17)(18)(31)(32)(33). Here, we show that the combination of anti-4-1BB with anti-PD-1 synergistically inhibited the growth of B16F10 melanoma and MC38 colon carcinoma in syngeneic C57BL/6 mice, and that the combination was reasonably well tolerated, supporting the clinical development of an anti-4-1BB/anti-PD-1 combination immunotherapy.…”

Focusing and sustaining the antitumor CTL effector killer response by agonist anti-CD137 mAb

“…Indeed, we have recently reported synergy against spontaneous liver cancer expressing transgenic OVA of a combination of anti-OVA OT-1 + OT-2 T cells in conjunction with a combination of immunostimulatory mAb (33).…”

Nivolumab and Urelumab Enhance Antitumor Activity of Human T Lymphocytes Engrafted in Rag2−/−IL2Rγnull Immunodeficient Mice

“…There are inherent problems due to major differences in the interplay of artificially inoculated tumor cells and a mouse immune system, which shows major divergences with its human counterpart (40). Oncogene-transgenic mice developing spontaneous tumors might be more predictable for immunotherapies but still rely on a murine immune system and are conceivably less antigenic than those malignancies that have undergone conventional carcinogenesis, with many mutations resulting in neoantigens (41)(42)(43). In addition, most immunostimulatory antibodies developed for clinical use do not recognize mouse receptors precluding their preclinical evaluation in these cancer models.…”