Significant advances in melanoma research have resulted in new therapies that have remarkably improved the management and overall survival of melanoma. However, many patients still succumb to the disease and more than half of all melanoma deaths are due to brain metastases. As a means to overcome this challenge, we developed a novel mouse model that allows postnatal delivery of genes of interest to melanocytes. Using genomic and proteomic data from human melanoma samples, we tested several gene combinations for their ability to induce metastatic melanoma in vivo. Hyperactivation of the PI3K/AKT pathway in the context of mutant BRAF and CDKN2A loss resulted in the development of spontaneous melanoma with full penetrance and a mean survival of only 6 weeks. The majority of these mice also developed multiple metastases to the lungs and brain. This model mimics the human disease genetically, histologically, and by sites of metastasis. Importantly, this model system provides a powerful platform to further study the mechanisms of melanoma metastasis. Elucidation of this network will allow the identification of key pathway nodes that represent potential therapeutic targets to disrupt this process. We used next generation sequencing and proteomics analysis of non-metastatic and metastatic tumor samples to identify downstream targets of AKT1 implicated in melanoma brain metastasis. Our data showed that tumors expressing activated AKT1 displayed elevated levels of focal adhesion (FA) factors and phosphorylated focal adhesion kinase (P-FAK). In addition, mutant AKT1 expression increased invasion and this was reduced by pharmacological inhibition of either AKT or FAK. Moreover, loss of PTEN, which also results in increased FAK activity, cooperated with activated AKT1 to further enhance brain metastasis in vivo. Despite these promising preliminary findings, a critical gap still remains in understanding whether and how FAK promotes melanoma brain metastasis, and whether the AKT1-FAK-PTEN axis can be exploited as a therapeutic target in this disease. Our long-term goal is to use this knowledge to develop novel melanoma therapies and improve patient outcomes. Pursuant to this goal, we have generated a diverse collection of state-of-the-art research tools and assembled a talented team of scientists and clinicians with a track record of productive collaboration to carry out and critically evaluate the results of the proposed aims. Using these unique resources, we propose to test the following hypotheses: 1) AKT1→ FAK signaling is essential for the development of melanoma brain metastases; 2) Combined inhibition of BRAFV600E, MEK, and FAK is superior to standard of care targeted therapy and; 3) Loss of PTEN expression results in sustained FAK phosphorylation, which enhances the development of melanoma brain metastases. Successful completion of the aims in this proposal will significantly impact the field by laying the groundwork for translation into clinical trials, leading to new and better treatments for patients with brain metastases and those who are at high risk of developing brain metastases.

Recently approved therapies have shown unprecedented promise in advanced stages of melanoma but clinical management of brain metastases remains challenging. This project strives to understand the mechanisms by which melanomas metastasize to the brain such that more effective therapies can be developed to improve the outcomes for these patients.