Abstract LB452: Effects of AKT1, 2, and 3 knock-out by CRISPR-Cas9 in CD133+human melanoma stem cells treated with MEK and AKT inhibitors
Authors: Simbulan-Rosenthal Cynthia M. , Islam Nusrat , Alobaidi Ryyan , Moreno Alejandro , Patil Veerupaxagouda , Alzharani Amal , Sykora Peter , Rosenthal Dean S. 
Published: April 2024

Abstract
Melanoma-initiating stem cells are involved in tumorigenesis, invasion, and drug resistance in malignant melanoma, and are characterized by increased expression of the stem cell marker CD133. We previously showed that CD133 knockout (KO) by CRISPR-Cas9 enhanced MEK inhibitor trametinib (T) -induced apoptosis in patient-derived BAKP melanoma cells by reducing anti-apoptotic p-AKT and p-BAD and increasing pro-apoptotic BAX. Dox-induced CD133 expression, in contrast, diminished apoptosis in T-treated cells, and exhibited elevated p-AKT, p-BAD, and decreased activation of BAX and caspases-3 and -9. This is the first time that CD133 is shown to activate a survival pathway wherein (1) CD133 increases AKT phosphorylation and activation, which induces (2) BAD phosphorylation and inactivation, and (3) reduces caspases-3 and -9 activity leading to apoptosis suppression, increased cell survival and drug resistance in melanoma. We investigated the effects of MEK inhibition with T in combination with the pan-AKT inhibitor capivasertib (AZD5363; C) in BAKP melanoma cells, with or without Dox-induced CD133 expression. Kinetic XTT cell viability and Annexin-Sytox Blue apoptosis assays revealed significantly reduced survival of BAKP cells exposed to a combination of T+C, compared to T alone. To determine the relative contribution of each of the three AKT genes to increased drug resistance of CD133-inducible melanoma stem cells, AKT 1, 2, and/or 3 were knocked out using sgRNAs specific to each of the three AKTs in a CRISPR-Cas9 lentiviral vector, followed by puromycin selection. Gene knockout was confirmed by immunoblot analysis using antibodies specific to each of the three AKTs, as well as by DNA sequence analysis. BAKP control or AKT KO cells were then exposed to T or T+C, and subjected to apoptosis assays, as well as immunoblot analysis with antibodies to apoptosis markers. Single KO of AKT 2 or 3, but not AKT 1, sensitized BAKP cells exposed to T alone, partially obviating the requirement for C to inhibit AKT. Triple KO of AKT 1, 2, and 3 rendered cells even more sensitive to T alone. Targeting nodes of the AKT and MAPK survival pathways with trametinib and AZD5363 highlights the potential for combination therapies for melanoma stem cells increasing the arsenal of more effective treatments for patients with high-risk melanoma. Targeting AKT 1, 2, and/or 3 might be effective in eliminating recalcitrant CD133-positive stem-like cells that may be responsible for tumor recurrence.
Citation Format: Cynthia M. Simbulan-Rosenthal, Nusrat Islam, Ryyan Alobaidi, Alejandro Moreno, Veerupaxagouda Patil, Amal Alzharani, Peter Sykora, Dean S. Rosenthal. Effects of AKT1, 2, and 3 knock-out by CRISPR-Cas9 in CD133+human melanoma stem cells treated with MEK and AKT inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB452.