Melanoma is the most lethal skin cancer and when detected at an advanced stage in which cells have spread throughout the body (known as metastasis), success of currently available therapies is limited. The brain is a common site of metastasis for multiple cancer types and is associated with poor survival. Melanoma brain metastases (MBMs) occur in ~60% of metastatic melanoma patients and up to 90% at autopsy, illustrating melanoma’s striking ability to access and colonize the brain. Recent genomic sequencing studies revealed an enrichment of mutations in SWI/SNF chromatin remodeling subunits, particularly ARID2, in MBMs. However, it remains unclear how these mutations play a role in metastasis.

Chromatin regulators are emerging as promising candidates for cancer therapy because of their broad roles in orchestrating genome function, as well as their frequent alterations in cancer. We found that in ARID2-deficient melanoma tumors, cancer cells are more successfully able to metastasize to distal organs in animal models. We hypothesize that genetic loss of ARID2 may also confer an advantage for melanoma metastasis to survive in the brain environment. Here, we will carefully investigate the role of ARID2 in metastasis using brain-tropic human melanoma cells in animal models through a series of experiments that recapitulate various aspects of the metastatic process to the brain and other organs. We will investigate the genes and pathways that allow these cells to do so, which will provide insight into the poorly understood mechanisms of melanoma metastasis. Finally, our study will help improve our understanding of brain metastasis with potential impact for the treatment of melanoma patients.

Cancer treatment was revolutionized when scientists discovered how to activate a patients’ own immune system to fight tumors. Unfortunately, some patients have tumors that are seemingly invisible to the immune system.

We have been investigating the autophagy pathway, a process in which material within or outside the cell is engulfed and degraded. We found that inactivating the autophagy pathway in the cells that surround a melanoma results in a more active anti-tumor immune response and reduced melanoma growth. Inactivating autophagy in tumor-supporting cells combines with immune checkpoint inhibitors to further reduce melanoma growth.

Autophagy that eliminates cytoplasmic material is important for the viability of immune cells. We hypothesize that previous studies investigating the efficacy of autophagy inhibition for cancer treatment revealed limited effects in part because inhibiting autophagy in the patient reduced the viability of the immune cells that kill tumors.

In contrast, autophagy that degrades phagocytosed material is not required for the health of the immune cells. But autophagy that eliminates phagocyted material does suppresses the inflammatory response.

We propose to test whether eliminating only autophagy-mediated phagocytosis in immune cells, while retaining cytoplasmic autophagy in the immune cells, will result in cytokine secretion and a robust and enduring anti-tumor immune response. We will test whether this heightened immune response occurs even in tumors that would otherwise be missed by the immune system. We will further test whether eliminating autophagy-mediated phagocytosis in immune cells can cooperate with established immune checkpoint inhibition to dramatically reduce melanoma progression and metastasis.

With the goal of translating our findings to benefit cancer patients, we will test whether autophagy inhibitors have potential as cancer therapy using melanoma organoids developed from primary human melanomas. We will also test whether immune cells that lack autophagy-mediated phagocytosis can be co-introduced with melanoma cells to induce an antitumor response that impedes melanoma growth and metastasis.

Our goal is to develop new strategies to treat melanoma patients. In addition to small molecule inhibitors, we anticipate isolating stem cells from a melanoma patient’s blood, engineering the cells to eliminate autophagy-mediated phagocytosis, induce the stem cells to become macrophages, and then re-introducing the engineered cells into patients. We will also pursue a strategy of introducing a macrophage-targeted CRISPR complex that specifically engineers a patient’s macrophages to lose the ability to use autophagy for phagocytosed material. These strategies have the potential to shift tumors from “cold” to “hot,” thereby making them more responsive to immune checkpoint inhibition.

While immunotherapy has revolutionized the management of advanced melanoma, many patients still do not benefit from this treatment strategy. Indeed, currently available immunotherapies are benefiting approximately 50% of stage IV melanoma patients while almost 50% of responding patients will develop disease recurrence within one year. Therefore, there is a continued need to improve our therapeutic arsenal for better managing advanced melanoma patients. We have identified a genetic profile in a significant percentage of human melanomas previously shown to be refractory to anti-PD-1 immunotherapy and we have elucidated the underlying mechanisms driving immune suppression in these melanomas. Using a melanoma model, we have determined that this genetic profile supports an immunosuppressed state and contributes to immunotherapy resistance. Based on these findings, we propose that those melanomas with this genetic profile will exhibit improved responses to immunotherapy when this immunosuppressed state is inhibited using available pharmacologic agents. To test this hypothesis, we will utilize a larger melanoma patient database to validate the importance of this genetic profile in immunotherapy resistance and examine whether this genetic profile associates with an immunosuppressed state. Further studies will be performed in melanoma models to determine if melanomas with this identified genetic profile may respond more favorably to immunotherapy if the associated immunosuppressed state can be pharmacologically reversed. Additional work utilizing human melanoma tissues will also be executed to verify that this genetic profile can predict for enhanced sensitivity to inhibiting select signaling pathways driving this immunosuppressed state. Together, this work will provide the critical foundation for executing future clinical trials that test combinatorial immunotherapy regimens tailored for melanoma patients with select genetic profiles. Ultimately, this approach is expected to broaden the melanoma population capable of benefitting from available immunotherapies.