Abstract 4226: TNFRSF14 is a cell surface marker of MITF expression in melanoma

Abstract

Abstract Background: Transcriptional ‘cell states’ (defined as the genes expressed in a cell in any given point in time) can determine response to targeted and immune-based therapies in late-stage melanoma treatment. MITF and AXL are common markers of drug-sensitive and drug-resistant ‘cell states’, respectively; and extensive heterogeneity of both cell populations have been observed in melanoma cell lines and tumors. Understanding the mechanisms controlling these ‘cell-states’ may lead to therapeutic strategies to overcome resistance and improve patient survival. Problem: To date, certain experiments assessing cell population heterogeneity dynamics in melanoma (such as live cell sorting applications) has been limited by the lack of surface markers defining the MITF ‘cell-state’. Furthermore, existing antibodies against MITF commonly detect multiple expressed isoforms which can limit the accuracy of downstream experimental assays, such as in-cell western blot detection. Methods and Results: To find a suitable cell surface marker defining the MITF ‘cell state’, we used the PARIS GenePattern module with data from the Cancer Cell Encyclopedia. TNFRSF14, our highest ranked gene, was highly correlated to MITF transcript expression in melanoma cell lines. We confirmed this at the protein level through western blot detection and flow cytometry. Using flow cytometry, we could accurately follow ‘cell-state’ population dynamics of AXL and MITF following shRNA knockdown of MITF and during acquired drug resistance in culture. Outcomes: We have identified TNFRSF14 as a robust cell surface marker of MITF in melanoma. Our TNFRSF14 and AXL live cell flow protocol will be useful for those exploring ‘cell-state’ population dynamics and heterogeneity in melanoma and could contribute to new mechanistic insights of drug resistance. Citation Format: Ken Dutton-Regester, Nicholas K. Hayward. TNFRSF14 is a cell surface marker of MITF expression in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4226.