Abstract 272: Loss of Rab25 and associated mechanisms in cancerous transformation of melanocytes

Abstract Background: Rab25 is a member of RAS protein superfamily of small GTPases that belong to RAB11 subfamily located on 1q22 of chromosome. It is generally expressed by epithelial cells and its expression level varies by tissue types. From our previous research, Rab25 has been shown to be a significant player in moderating transformation of human mammary epithelial cells, as its loss promotes cellular transformation particularly in presence of RAS mutation. Rab25 is an ambiguous protein in cancer research as its role is cancer type dependent and remains unknown in melanoma. There is deep deletion of Rab25 in a section of melanomas (only∼3% profiled) in databases like the Cancer Genome Atlas and Cbioportal. Additionally, Rab25 shares a common consensus motif with the binding site of mutant H-RAS, Q61L. NRAS is mutated in 80% of RAS activated melanomas. Therefore, we are investigating the role of Rab25 loss in the development of NRAS mutant melanoma. Objectives: To study the status of Rab25 and its role in the transformation of melanocytes, we screened for Rab25 expression and protein level in different melanoma cell lines. We further did immunohistochemistry to examine the Rab25 expression in biopsy-proven melanoma sections. To uncover the function of Rab25, we overexpressed Rab25 in NRAS mutant melanoma cell lines and knocked down Rab25 in non-tumorigenic immortalized melanocytes. Further, we will use liposomal encapsulation technique to deliver a six-peptide sequence intracellularly to target NRAS. Results: There was significant loss of Rab25 in mRNA and protein level in melanoma cell lines. Rab25 is found in normal skin tissues but was significantly lost in melanoma sections and associated with reduced survival. NRAS mutant human melanoma cells transduced with Rab25 showed reduced proliferation, migration tendency, and loss of anchorage-independence growth as compared to control cell lines. Additionally, knockdown of Rab25 in non-cancerous immortalized human melanocytes showed resulted in enhanced proliferative behavior and gain of anchorage-independent growth in soft agar colony formation assay. Conclusion: These observations suggest that Rab25 loss results in gain of migratory potential, anchorage-independent growth, and enhanced proliferation potential which are requisite events in melanoma-genesis. Further studies on associated functional proteins of Rab GTPase family will be conducted to strengthen this data. Citation Format: Samikshya Kandel, Krishna Rao. Loss of Rab25 and associated mechanisms in cancerous transformation of melanocytes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 272.