TSU-68 ameliorates hepatocellular carcinoma growth by inhibiting microenvironmental platelet-derived growth factor signaling.

Background: TSU-68 is a multikinase inhibitor that targets platelet-derived growth factor receptors (PDGFRs). In the present study, we evaluated the effect of TSU-68 on the tumor-microenvironment interaction in hepatocellular carcinoma (HCC). Materials and Methods: HCC and fibroblast cell lines (HuH7, Hep3B, HuH1 and WI-38) were used to evaluate their interactions. Cancer characteristics were evaluated by spheroid formation and tumorigenicity in immunodeficient mice. Time-lapse image analysis was performed to monitor cell motility. Results: Although PDGFA was abundantly expressed, PDGFR-alpha was predominantly located in the cytoplasm and was not functional in HuH7 cells. Co-culture experiments demonstrated that HCC cells induced phosphorylation of PDGFR-alpha in WI-38 fibroblasts and that stimulated fibroblasts, in turn, boosted the spheroid formation capacity of HCC cells. TSU-68 inhibited phosphorylation of PDGFR-alpha in WI-38 cells and suppressed the growth of subcutaneously co-injected HuH7/WI-38 tumor xenografts. Conclusion: TSU-68 inhibits stromal PDGF signaling activated by cancer cells and suppresses HCC growth.