Abstract 3038: IDH1 facilitates melanoma cell survival under metabolic stress
Authors: Zarei Mehrdad , Vaziri-Gohar Ali , Hue Jonathan , Hajihassani Omid , Katayama Erryk , Graor Hallie , Winter Jordan , Rothermel Luke 
Published: June 2022

Abstract
Introduction: Novel immunotherapies and targeted therapies have generated remarkable responses for patients with melanoma relative to historic treatments, but these responses are only seen in about 50% of patients. This suggests that treatment resistance is an ongoing challenge for a significant number of patients with melanoma, leaving an urgent need for improved therapeutic strategies. In our previous studies, we demonstrated that oxidative stress has an important role in drug resistance, and that wild type isocitrate dehydrogenase 1 (IDH1) is a major source of cytosolic NADPH that maintains redox homeostasis of cells under hypoxic and metabolic stress. This critical enzyme has not been thoroughly evaluated in melanoma. Herein, we explored the expression and function of IDH1 in human melanoma and the role of IDH1 in regulating melanoma metabolism.
Methods: We evaluated IDH1 expression in primary and metastatic melanoma using The Cancer Genome Atlas (TCGA). We performed IDH1 knockdown by siRNA oligos, and evaluated cell viability by Trypan blue and PicoGreen assays under normal and nutrient-deprived conditions. Cellular reactive oxygen species (ROS) levels were determined by the DCFDA method. Metastatic activity of these cells was measured by transwell migration assays. In order to determine the impact of IDH1 in cellular metabolism, metabolomics profiling was performed by using LC-MS. These experiments were performed in A375 and SK-Mel 28 cell lines.
Results: Analysis of TCGA data from melanoma samples showed IDH1 is highly overexpressed in primary and metastatic melanoma, and higher levels are associated with decreased progression-free survival in patients. Further, we validated that IDH1 is overexpressed in tumors by comparing normal skin tissue versus tumor samples by IHC and protein expression arrays. Silencing IDH1 impaired cell proliferation and migration (vs. control) in a nutrient-deprived microenvironment, but this effect was not seen in nutrient abundance. Metabolomics revealed that inhibiting IDH1 significantly decreased NADPH, α-ketoglutarate (αKG), and GSH levels with a corresponding increase in ROS levels and an impairment of mitochondrial function. In addition, silencing IDH1 sensitized melanoma cells to temozolomide (TMZ), a DNA-alkylating agent, as indicated by a decrease in relative cell survival compared with controls.
Conclusion: IDH1 plays a critical role in tumorigenesis and chemoresistance in melanoma. Our data show that IDH1 inhibition sensitizes melanoma cells to TMZ therapy. Our study suggests that IDH1 is a potential target in melanoma as a monotherapy or in combination with existing chemotherapies.
Citation Format: Mehrdad Zarei, Ali Vaziri-Gohar, Jonathan Hue, Omid Hajihassani, Erryk Katayama, Hallie Graor, Jordan Winter, Luke Rothermel. IDH1 facilitates melanoma cell survival under metabolic stress [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3038.