Metformin inhibits cell proliferation and ACTH secretion in AtT20 cells via regulating the MAPK pathway

We investigated the impact of metformin on ACTH secretion and tumorigenesis in pituitary corticotroph tumors. The mouse pituitary tumor AtT20 cell line was treated with varying concentrations of metformin. Cell viability was assessed using the CCK-8 assay, ACTH secretion was measured using an ELISA kit, changes in the cell cycle were analyzed using flow cytometry, and the expression of related proteins was evaluated using western blotting. RNA sequencing was performed on metformin-treated cells. Additionally, an in vivo BALB/c nude xenograft tumor model was established in nude mice, and immunohistochemical staining was conducted for further verification. Following metformin treatment, cell proliferation was inhibited, ACTH secretion decreased, and G1/S phase arrest occurred. Analysis of differentially expressed genes revealed cancer-related pathways, including the MAPK pathway. Western blotting confirmed a decrease in phosphorylated ERK1/2 and phosphorylated JNK. Combining metformin with the ERK1/2 inhibitor Ulixertinib resulted in a stronger inhibitory effect on cell proliferation and POMC (Precursors of ACTH) expression. In vivo studies confirmed that metformin inhibited tumor growth and reduced ACTH secretion. In conclusion, metformin inhibits tumor progression and ACTH secretion, potentially through suppression of the MAPK pathway in AtT20 cell lines. These findings suggest metformin as a potential drug for the treatment of Cushing's disease.