Glucose and Cell Context-Dependent Impact of BMI-1 Inhibitor PTC-209 on AKT Pathway in Endometrial Cancer Cells

SIMPLE SUMMARY: The insulin/IGF-1/AKT pathway is a key event linking metabolic syndrome with endometrial cancer. It has been found that BMI-1 may also influence the AKT kinase pathway and that increased activity is associated with cancer onset and progression. The aim of our study was to determine the role of BMI-1 in glucose and molecular context-dependent regulation of PHLPP expression and AKT kinase activity in endometrial cancer cells. The studies were conducted using endometrial cancer cells (HEC-1A, Ishikawa). Glucose and insulin impact on the BMI-1 dependent regulation of PHLPP-analyzed cells with the downregulation of BMI-1 expression in hypo-, normo-, and hyperglycemia conditions and stimulation by insulin. Understanding the relationship between hyperglycemia, BMI-1, PTEN, and PHLPP functions, may contribute in the future to the development of therapeutic approaches that will be better adapted to the molecular context and the specificity of endometrial cancers and more effective in cases of metabolic diseases co-existence. ABSTRACT: Purpose: In our study, the glucose and cell context-dependent impact of the BMI-1 inhibitor PTC-209 on the AKT pathway in endometrial cancer cells was determined. Methods: The expression of BMI-1 was inhibited by PTC-209 in endometrial cancer cells HEC-1A and Ishikawa stimulated with insulin and grown in different glucose concentrations. The migration, invasion, viability, and proliferative potential after PTC-209 treatment was assessed using wound-healing, Transwell assay, Matrigel-coated inserts, and MTT tests. Chromatin immunoprecipitation was used to determine the localization of BMI-1 protein at promoter sites of the genes tested. Results: BMI-1 inhibition caused an increase in PHLPP1/2 expression and a decrease in phospho-AKT level in both cell lines. The glucose concentration and insulin stimulation differentially impact the AKT pathway through BMI-1 in cells differing in PTEN statuses. The expression of BMI-1 is dependent on the glucose concentration and insulin stimulation mostly in PTEN positive HEC-1A cells. In high glucose concentrations, BMI-1 affects AKT activity through PHLPPs and in hypoglycemia mostly through PTEN. BMI-1 inhibition impacts on genes involved in SNAIL, SLUG, and CDH1 and reduces endometrial cancer cells’ migratory and invasive potential. Conclusions: Our results indicate that the relationship between BMI-1 and phosphatases involved in AKT regulation depends on the glucose concentration and insulin stimulation.