Beyond Pigment Synthesis: Investigating Dopachrome Tautomerase (DCT) Localization and Interactions with Cell Cycle Proteins

Abstract

Melanoma is a highly lethal skin cancer with limited therapeutic options once it metastasizes, largely due to acquired resistance to immunotherapy and targeted treatments. Dopachrome tautomerase (DCT), formerly recognized for its enzymatic contribution to pigment synthesis, is now emerging as a biomarker and molecular driver associated with poor prognosis, stress resistance, and therapy failure in melanoma. Although pigment production is not strictly required for melanocyte survival, evidence reveals that DCT’s retained and upregulated expression in melanoma supports tumor resilience and adaptation under therapeutic stress. This study addresses how DCT contributes to melanoma cell proliferation and cell cycle regulation through non-canonical mechanisms. Using immunofluorescence assays, cell cycle synchronization, RNAi-mediated knockdown, proximity labeling, and lentiviral transduction, we examine DCT’s spatial dynamics and molecular interactions. DCT localization to the nuclear envelope is dependent on cell cycle stage, and proximity labeling assays reveal DCT’s selective interaction with Cyclin-dependent kinase 2 (CDK2), a cell cycle kinase crucial for melanoma survival, specifically in melanoma cell lines. Functional studies indicate that knockdown of DCT causes G1/S cell cycle blockade and suppresses clonal expansion and tumor growth, both in culture and animal models. Furthermore, proximity ligation confirms endogenous nuclear co-localization of DCT and CDK2, implicating DCT’s nuclear interactions in cell cycle control. Key findings show that DCT, beyond its classical role in melanogenesis, localizes to the nucleus in melanoma cells, particularly in the contexts where CDK2 is also nuclear. Although DCT and CDK2 co-localize in the nucleus, and this may support melanoma cell proliferation and cell cycle regulation, we do not directly demonstrate effects on therapy resistance in this study. Future research should focus on elucidating the functional relationship between DCT nuclear localization, CDK2 activation, and cell cycle control to determine whether DCT-mediated pathways contribute to stress responses or resistance phenotypes in advanced melanoma.A three-year embargo was granted for this item.Academic Major: Molecular Genetic