Melanoma account for over 10,000 deaths annually in the United States alone and current therapies for advanced-stage melanoma do not provide durable clinical benefit. Therefore, improved molecular understanding of melanoma is essential for developing effective therapies. According to The Cancer Genome Atlas (TCGA) melanoma data over 45% melanoma lack tumor suppressor p16. However, there is no specific personalized treatment option available for p16-deficient melanoma. Therefore, we performed an innovative large-scale druggable genome RNAi screen and identified Cell division cycle 7 (CDC7) kinase as a candidate that is necessary for the survival of p16-deficient melanoma. shRNA-induced knockdown of CDC7 inhibited p16-deficient melanoma tumors and metastases in vivo. Our central hypothesis is that p16-deficient melanoma depends upon CDC7 for their survival and CDC7 inhibition will be of therapeutic value for treating p16-deficient melanoma. The overall objective is to determine the effect of genetic and pharmacological inhibition of CDC7 on melanoma tumor growth and metastasis and understand why CDC7 is necessary for p16-deficient melanoma. Specifically, in Aim 1, we will determine the effect of genetic and pharmacological inhibition of CDC7 on melanoma tumor growth and metastasis. To this end, will determine the role of CDC7 in tumor growth and metastasis in the context of p16-deficiency. Additionally, using XL413, a small molecule inhibitor of CDC7, alone or in combination with BRAFV600E inhibitor vemurafenib (for melanoma co-harboring both BRAFV600E mutation and p16-deficiency), we will determine if pharmacological inhibition of CDC7 alone or in combination with BRAFV600E inhibitors can be employed to effectively treat p16-deficient melanoma in vivo. The experimental approach will utilize mouse models of melanoma tumor growth and metastasis and will utilize established and melanoma patient-derived short-term melanoma cultures available from Yale SPORE in Skin Cancer.
In Aim 2, we will determine why CDC7 is necessary for the survival of p16-deficient melanoma. Using transcriptome-wide gene expression profiling and Tandem Affinity Purification and mass spectrometry- based proteomics approaches, we find that the p16-deficient melanoma cells show activation of Unfolded Protein Response (UPR) pathway and that CDC7 maintains the activity of UPR pathway potentially via transcription factor HOXA1 to promote melanoma tumor growth and metastasis. Therefore, we will determine how CDC7 regulates UPR pathway via HOXA1 in p16-deficient melanoma cells. Additionally, we will test whether CDC7-loss induced tumor growth and metastasis inhibition of p16-deficient melanoma cells can be rescued by restoring HOXA1 expression and the UPR pathway activity. Collectively, we expect to uncover a novel CDC7-driven druggable genetic vulnerability pathway that can be targeted for effective personalized therapy of p16-deficient melanoma, including for highly aggressive metastatic melanoma.
SIGNIFICANCE Melanoma account for over 85% of skin cancer-related deaths and due to the lack of effective therapies only 15% advanced-stage melanoma patients survive beyond 5 years. Using a functional genomics approach of druggable genome RNAi screen, we identified CDC7 kinase as a candidate that is necessary for the survival of p16-deficient melanoma. The results of our proposed experiments will significantly improve our understanding of p16-deficient melanoma and validate the utility of pharmacological targeting of CDC7 kinase for treating p16-deficient melanoma, including highly aggressive metastatic melanoma.