BAMLET (Bovine α-lactalbumin made lethal to tumor cells) inhibits autophagy flux and induces apoptosis via down-regulation of protein kinase CK1α and attenuation of the AKT/ p-ss-catenin (S552) pathway in RAS-mutated human colorectal HCT 116 cells

Objective(s): Oncogenic RAS mutations occur in nearly 50% of colorectal cancer cases and are usually dependent on the autophagy mechanism to maintain tumorigenesis. We have recently demonstrated that CK1 alpha controls autophagy machinery possibly through the AKT/p-13-catenin (S552) signaling in colorectal cancer cells harboring RAS mutation. It has been found that a lipid -protein complex comprising oleic acid binds to human alpha-lactalbumin, known as HAMLET (human alpha-lactalbumin made lethal to tumor cells), targets a broad range of kinases including CK1 alpha. Therefore, this study was designed to investigate the effects of BAMLET (bovine alpha-lactalbumin made lethal to tumor cells, the bovine counterpart of HAMLET) on CK1 alpha expression, AKT/Phospho-13-catenin (S552) pathway, and autophagy flux in RAS-mutated human colorectal HCT 116 cells.Materials and Methods: For this purpose, HCT116 cells were treated with BAMLET and casein kinase 1 inhibitor (D4476), and quantitative real-time polymerase chain reaction (RT-qPCR) and western blot analysis were used to measure the proteins and genes of the AKT/Phospho-13-catenin (S552) pathway and autophagy. Apoptosis was measured by flow-cytometry.Results: We found that BAMLET significantly reduced cell viability and decreased the expression of CK1 alpha. Additionally, BAMLET inhibited autophagy flux and enhanced the ability of CK1 alpha inhibitor D4476 to impair autophagy flux, which was accompanied by an increase in the apoptosis percentage. We also observed that BAMLET empowered D4476 to down-regulate the AKT/Phospho-13-catenin (S552) axis.Conclusion: BAMLET hampers autophagy flux and leads to apoptosis induction, possibly, by reducing the expression of CK1 alpha and attenuation of the AKT/Phospho-13-catenin (S552) axis.