A Novel ULK1 Pathway as a New Therapeutic Target in Melanoma

Project Summary/Abstract Melanoma is a highly fatal malignancy for which immunotherapy approaches designed to overcome tumor immune escape mechanisms have been rising as a promising therapeutic strategy. While immune checkpoint blockade (ICB) has transformed cancer therapy in advanced melanoma with already FDA approval for 3 different checkpoint inhibitors, the majority of patients are resistant to therapy initially (primary) or respond but then relapse with resistant disease (acquired). Additional immune-based strategies in combination or as an alternative are critically needed. Thus, efforts to identify mechanisms of resistance to checkpoint inhibitors and approaches to overcome primary and acquired resistance are warranted. Surprisingly, type II interferon (IFN) signaling pathways and expression of IFN-stimulated genes (ISGs) in melanoma tumors have been shown to correlate with either response or resistance to ICB treatment in melanoma in a context-dependent manner. While IFN pathway genes are required for effector function of tumor-reactive T cells and response to ICB in melanoma, IFN is also known to induce expression of immunosuppressive genes and chronic IFN signaling promotes acquired resistance to ICB. This dual role of IFN signaling supports the need to identify means to regulate its effects in order to promote cytotoxic T lymphocyte (CTL) activity without promoting immunosuppression. We have recently discovered that ULK1 (Unc-51-like kinase 1) controls activation of unique IFN signaling events and transcription of specific IFN-induced genes involved in the control of immune responses. Importantly, our preliminary studies show that pharmacologic and genetic targeting of ULK1 in melanoma cells represses IFN-induced expression of immunosuppressive genes and ULK1 expression correlates with poor overall survival in melanoma patients. The goal of this project is to determine if targeting ULK1 suppress IFN-dependent immunosuppressive effects, while promoting IFN-mediated CTL activity against melanoma. Aim 1 will define the specific role of ULK1 on cytotoxic T lymphocyte activity against melanoma. It includes generation of specific knockout melanoma cells using the CRISPR/Cas9 gene editing, and evaluation of its effects on tumor T-cell mediated killing in vitro and in vivo. Aim 2 will define the role of ULK1 in ICB-mediated immune responses in melanoma. The effects on melanoma tumor growth of ULK1 small-molecule inhibitor alone and in combination with immune checkpoint inhibitors will be examined in vivo. Additionally, the expression of ULK1 will be correlated to clinical responses in melanoma patients receiving ICB therapy. The results of this project will advance our understanding on how specific IFN signaling events affect the success of immune responses against melanoma. Moreover, the work proposed in this application is of high clinical-translational relevance because it will provide the basis for novel targeted approaches involving combination of specific regulators of IFN signaling with immune checkpoint inhibitors for the treatment of melanoma.