Abstract 5526: Inhibition of MEK and AKT synergistically induces melanoma stem cell apoptosis and blocks NRAS-mutant xenograft growth

Abstract Melanoma-initiating cells (MIC) are involved in tumorigenesis, drug resistance and metastasis, and are characterized by upregulated stem cell markers, including CD133. Our previous studies showed that CD133 siRNA increases apoptosis in response to the MEK inhibitor trametinib. The current study employs CRISPR-Cas9 CD133-KO or Dox-induced expression of CD133 to investigate the anti-apoptotic mechanism of CD133 in patient-derived BAKP melanoma cells, harboring an NRASQ61K driver mutation. CD133-KO cells downregulated pro-survival markers p-AKT and p-BAD, and upregulated pro-apoptotic BAX. On the flip side, Dox-induced CD133 increased expression of p-AKT and p-BAD, and decreased activation of BAX and caspase-3. Hence, an alternate survival pathway may be activated in MICs, wherein CD133 induces AKT phosphorylation and activation, which phosphorylates and inactivates BAD, decreasing BAX activation, and reducing caspases-3 activity and caspase-mediated PARP cleavage, ultimately resulting in apoptosis inhibition and chemoresistance in melanoma. However, trametinib in combination with the pan-AKT inhibitor, capivasertib, can synergistically reduce cell survival even in trametinib-resistant CD133-expressing MICs in vitro, as determined by XTT, annexin-FITC, and colony forming assays. Similarly, in vivo mouse xenograft studies using Dox-inducible BAKP cells revealed increased rates of tumor growth after induction of CD133 expression in trametinib-treated +Dox mice, an effect that was most effectively suppressed by the combination treatment. Therefore, targeting nodes of the AKT and MAPK survival pathways with trametinib and capivasertib underscores the potential for combination therapies for difficult-to-treat NRAS-mutant melanoma stem cells, paving the path towards improved treatment strategies for patients with high-risk melanoma. Citation Format: Nusrat Islam, Ryyan Alobaidi, Toni M. Olkey, Yogameenakshi Haribabu, Mathew Shamo, Peter Sykora, Cynthia M. Simbulan-Rosenthal, Dean S. Rosenthal. Inhibition of MEK and AKT synergistically induces melanoma stem cell apoptosis and blocks NRAS-mutant xenograft growth [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 5526.