Abstract 5137: IQGAP1, an ERK1/2 MAPK scaffold, is an oncogenic target in canine melanoma

Abstract

Abstract BACKGROUND: Human cutaneous melanoma is primarily driven by activating mutations in Braf (60%) or Nras (20%). However, human oral melanoma harbors these mutations much less frequently. Similarly, canine oral mucosal melanomas have not been found to have activating Braf or Nras mutations. This makes them an ideal model to study alternative means of ERK1/2 MAPK pathway activation as these tumors are still reliant on MAPK signaling. We have previously studied IQGAP1 as a tumor specific ERK1/2 MAPK scaffold and shown that it is required for cancer progression. METHODS: In this study, we utilized canine oral melanoma cell lines obtained from the University of California-Davis. We examined the expression and localization of IQGAP1, a signaling scaffold that regulates oncogenic ERK1/2 MAPK signaling in human cancer, and validate it as an oncogenic target in the canine melanoma model. Using a CRISPR/Cas9 knockout of IQGAP1, we examined effects on downstream pathway activation. Additionally, we assayed proliferation of these cell lines when treated with a peptide that blocks the interaction between IQGAP1 and ERK1/2. RESULTS: We observed that canine IQGAP1 is expressed and localizes to a similar extent in human and canine melanoma by qPCR, Western blot and immunofluorescence. Deletion of IQGAP1 from two canine oral melanoma cell lines using CRISPR-Cas9 genome editing reduces MAPK pathway activation, similar to effects seen in human BrafV600E cell lines. Additionally, we demonstrated reduced proliferation when these cells are treated with the WW blocking peptide in-vitro. We are currently investigating the expression and localization of IQGAP1 in primary canine oral melanoma compared to normal oral mucosa. CONCLUSION: Building on the above findings to explore alternative MAPK signaling in melanoma using the canine melanoma model may yield novel therapeutic strategies and novel means to target canine and human tumors that are resistant to current Braf and MEK targeted therapies. Citation Format: Ashley Zehnder, Becky Lee, Poornima Neela, Paul Khavari. IQGAP1, an ERK1/2 MAPK scaffold, is an oncogenic target in canine melanoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5137. doi:10.1158/1538-7445.AM2015-5137