Mechanisms underlying combination therapy mobilizing NK cells

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Checkpoint therapy is remarkably effective against many malignancies that were previously devoid of effective treatment options. Nevertheless, even for the types of cancer where it is effective, many patients do not respond, or their cancers recur. The therapy is ineffective in many other types of cancer. Evidence has accumulated that ineffective checkpoint therapy is often due to either the dearth of neoantigens in a given type or example of cancer, or acquired resistance to therapy, which is frequently due to loss of MHC I antigen presentation or neoantigen expression. Therapeutics that mobilize NK cells may dramatically complement T cell mediated anti- tumor mechanisms, because NK cells do not depend on neoantigens, and are especially effective against MHC- deficient tumors, which arise during checkpoint therapy. Preliminary data show that innate agonists, such as a STING agonist, dramatically synergize with an IL-2 superkine called H9-MSA, leading to NK-dependent indefinite long term tumor free survival in mice with established MHC I-deficient tumors, including the cold B16-B2m-/- model and the MC-38-B2m-/- model, which were otherwise refractory to each therapy alone. Strikingly, this therapy combination was also effective in “curing” mice of MHC I+ B16 tumors, mediated by CD8 T cells, and primary methylcholanthrene (MCA)-induced sarcomas, a highly stringent autochthonous model of cancer that was also refractory to checkpoint therapy, where both T cells and NK cells mediated antitumor effects. In the latter model, the addition of checkpoint therapy led to long term remissions in ~half the animals. In clinical trials, STING agonists alone have been disappointing in cancer patients, but our new evidence of great synergy of STING agonists and IL-2 superkine suggests that the combination may have great potential for applications in human cancer therapy. We will interrogate the mechanisms of synergistic efficacy of this combination, including whether STING agonist, via IFN, protects NK cells from fratricide induced by the superkine, or cooperatively prevents NK desensitization. We will further address the impact of checkpoint therapy on top of or preceding this therapy combination, including understanding how T cells and NK cells cooperate. We will model the acquired resistance of tumors to checkpoint therapy via selection of MHC-loss variants expression in a tumor transfer model. Finally, we will employ the MCA sarcoma model undergoing therapy to test the roles of T cells in selecting MHC I deficient or other NK sensitive variants, and of NK cells in potentially selecting T cell sensitive variants. The culmination of these studies will provide a strong basis for understanding and applying this form of combination therapy in human patients with cancer.