GDF2 and hepatocellular carcinoma: A biomarker study of GT90001 monotherapy in patients with advanced HCC suggested that the following markers were associated with treatment efficacy: high tumor expression of c-met, high serum levels of bone morphogenetic protein-9 (a high affinity ALK-1 ligand), lower serum TGF-β, and low vascular endothelial growth factor receptor-3 [18].