Hy 13521

Transfection was performed using Lipofectamine 3000 (Thermo Fisher Scientific, Waltham, MA, USA) according to the manufacturer’s instructions. Cells were transfected with miR-1208 mimics, miR-mimic-control, circCREBBP siRNAs, TGFβ2 siRNAs, or si-NC (RiboBio, Guangzhou, China) at 50 nM, whereas miR-1208 inhibitor or inhibitor control (RiboBio) was used at a concentration of 100 nM. The overexpression vector pLC5-circCREBBP was constructed using amplified DNA fragments, including the sequence of full-length human circCREBBP_007 cDNA (713 bp, NM_004380) obtained from Geneseed (Guangzhou, China). Human pGenesil-1-si-h-circCREBBP based on valid siRNA-circCREBBP sequences was purchased from HanBio (Shanghai, China). The specific sequences are listed in Supplementary Table 3. Specific inhibitors of ALK5 (SB-505124, HY-13521, 1 μM) and ALK1 (K02288, HY-12278, 0.5 µM) were purchased from MedChemExpress (Monmouth Junction, NJ, USA).

The GH3, AtT20, MMQ, and RC-4BC cell lines were purchased from the American Type Culture Collection (ATCC, Manassas, VA, USA). GH3, AtT20, and MMQ cell line Twere cultured in Ham's F-12 K medium (L450KJ, BasalMedia) supplemented with 2.5% FBS (S615JY, BasalMedia), 15% horse serum (26,050,088, ThermoFisher), and 1% penicillin/streptomycin (C100C5, NCM biotech. RC-4BC cells were cultured in DMEM (L130KJ, BasalMedia) with 10% FBS, 5 ng/ml recombinant rat EGF (ab290070, Abcam), and 1% penicillin/streptomycin. The following inhibitor and recombinant protein were used: recombinant INHBA (C687, Novoprotein), SB-505124 (HY-13521, MedChemExpress), A 83–01 (HY-10432, MedChemExpress), and recombinant human Follistatin (10685-H08H, Sino Biological).