Enhancing cancer immunotherapy by combining Notch 1 and death receptor activation (46.38)

Abstract

Abstract Notch signaling plays diverse roles in lymphocyte differentiation and tumor angiogenesis. Our recent findings implicate the role of Notch 1 pathway in promoting antitumor immune effector functions. We explored the effects of Notch 1 stimulation on T cell immunity and its potential pharmacological activation using Delta-like Notch 1 ligand DLL1 cluster in combination with the proteasome inhibitor bortezomib, which could stabilize Notch 1 activation. Bortezomib was found to selectively sensitize solid tumor cells to apoptosis by upregulating death receptors on tumor cells and amplifying caspase-8 activation in the death-inducing signaling complex. This resulted in reduced pulmonary nodules of injected tumor cells in mice. Additionally, in an in vivo tumor setting, no adverse effects of bortezomib were observed on the antigen-specific T cell proliferative or cytolytic functions. But no long-term survival benefits could be obtained, possibly due to the immunosuppressive effects of the tumor. In our more recent studies, we observed that DLL1-specific immune Notch activation could enhance antitumor T cell immunity by overcoming tumor-associated immunosuppression in D459 and Lewis lung carcinoma models. The results offer a novel combinatorial approach to abrogate the immunosuppressive circuitries operating in the tumor microenvironment with a potential to reduce tumor burden and strengthen tumor-specific immune responses.