Jenkins, James William

Background Cancers persist despite expression of immunogenic neoantigens and ongoing antitumor immune responses. While some occult tumors likely are cleared by effective antitumor immune responses, the targeted antigens are not easily identifiable as those tumors spontaneously disappear. Methods We used mouse models with a defined antigenic protein mimicking tumor-specific neoantigens to address the nature of these spontaneous anti-tumor immune responses. Results BALB/c (H-2d ) mice challenged with BALB/c breast tumors expressing the rat-erbB2 oncoprotein succumb to their tumors despite ongoing immune responses targeting tumor-specific model antigens. Meanwhile, congenic BALB.B (H-2b ) and H-2d/H-2b F1 hybrid mice spontaneously eliminate genetically matched tumors in a major histocompatibility complex (MHC)-II dependent manner. Adoptive transfer and immune cell depletion strategies revealed CD4+ T cells and CD20+ B cells are crucial mediators of the protective response in H-2b mice. Furthermore, passive transfer of immune serum from mice rejecting their tumors confers resistance in tumor antigen-tolerant animals with an inversely proportional relationship between tumor outgrowth and the amount of rat-erbB2 specific antibody present in tumor-bearing mice. Introduction of the rat-erb2 ectodomain into other H-2b tumor models also promotes their spontaneous tumor rejection. Notably, the tumor microenvironments differ in rat-erbB2+ tumor-bearing BALB.B and BALB/c mice at the time of fate decision in the models reflecting the differences between effective and ineffective tumor immune responses. Conclusions We find that the effective antitumor immunity targeting neoantigens in these breast cancer models is determined by MHC-II-restricted presentation of optimal cancer-associated antigens. These responses are dependent on CD4+ T cells, B cells, and antigen-specific antibodies.

Background Ovarian cancer (OC), a highly lethal cancer in women, has a 48% 5-year overall survival rate. Prior studies link the presence of IL-17 and Th17 T cells in the tumor microenvironment to improved survival in OC patients. To determine if Th17-inducing vaccines are therapeutically effective in OC, we created a murine model of Th17-inducing dendritic cell (DC) (Th17-DC) vaccination generated by stimulating IL-15 while blocking p38 MAPK in bone marrow-derived DCs, followed by antigen pulsing. Methods ID8 tumor cells were injected intraperitoneally into mice. Mice were treated with Th17-DC or conventional DC (cDC) vaccine alone or with immune checkpoint blockade (ICB). Systemic immunity, tumor associated immunity, tumor size and survival were examined using a variety of experimental strategies. Results Th17-DC vaccines increased Th17 T cells in the tumor microenvironment, reshaped the myeloid microenvironment, and improved mouse survival compared with cDC vaccines. ICB had limited efficacy in OC, but Th17-inducing DC vaccination sensitized it to anti-PD-1 ICB, resulting in durable progression-free survival by overcoming IL-10-mediated resistance. Th17-DC vaccine efficacy, alone or with ICB, was mediated by CD4 T cells, but not CD8 T cells. Conclusions These findings emphasize using biologically relevant immune modifiers, like Th17-DC vaccines, in OC treatment to reshape the tumor microenvironment and enhance clinical responses to ICB therapy.