ACVR1B and hepatocellular carcinoma: To test which TGF-β superfamily receptor was involved in GDF1-induced HCC tumour lineage plasticity, PLC-8024 cells stably transfected with or without GDF1 were transduced with lentivirus-mediated shRNAs specifically targeting different ALKs (ALK4/5/7), respectively (Fig. 4a).