Cell culture and transfection

The mouse pituitary adenoma cell line AtT-20 used in this study was purchased from American Type Culture Collection (ATCC, Manassas, VA, USA; CCL-89™). The cells were seeded in F-12K medium (Gibco, Waltham, MA, USA) supplemented with 10% fetal bovine serum (FBS; Gibco) and maintained at 37 °C in humidified air with 5% CO₂.

For transfection experiments, the AtT-20 cells were cultured in growth medium without antibiotics to 80% confluence and then transfected using a transfection reagent (Lipofectamine 3000, Thermo Fisher Scientific, Waltham, MA, USA) according to the manufacturer’s instructions. The miR-30d mimic (cat. no. miR10000245-1-5), the negative control (NC) of the miR-30d mimic (NC miR-30d mimic; cat. no. miR01201-1-5), miR-30d inhibitor (cat. no. miR20000245-1-5), and inhibitor NC (cat. no. miR2N0000001-1-5) were purchased from Guangzhou RiboBio Co. (Guangzhou, China). After incubation for 6 h, the medium was removed and replaced with normal culture medium for 24 h.