Abstract 1047: The multikinase inhibitor K252a suppresses hepatocellular carcinoma tumor growth in a mouse xenograft model
Authors: Abe Mitsuhiko , Koga Hironori , Yoshida Takafumi , Masuda Hiroshi , Sakata Masahiro , Ikezono Yu , Nakamura Toru , Taniguchi Eitaro , Kawaguchi Takumi , Yano Hirohisa , Torimura Takuji , Sata Michio 
Published: May 2015

There are several ongoing clinical trials of molecular-targeted therapy for hepatocellular carcinoma (HCC), but no clearly effective therapy has yet emerged. Under such conditions, we have been focusing on potentially powerful anticancer effects of the novel multikinase inhibitor K252a, since it targets unique kinases, including PKC, CaMKII, c-Met, TrkB, MLCK, and phosphorylase kinase. Indeed, the former five targets are expressed in HCC tissues and involved in cellular proliferation, invasion, and metastasis (Yoshiji et al., Cancer Res 1999, etc.). The broad spectrum of the targets may block escape pathways in HCC cells, that are resistant to conventional anticancer drugs and even sorafenib. The AIM of this study was to assess whether K252a suppressed cellular proliferation and altered malignant phenotypes such as epithelial-mesenchymal transition (EMT) both in vitro and in vivo. Materials and Methods: The human HCC cell lines HAK-1A, HAK-1B (Yano et al., Hepatology 1993), KYN-2 (Yano et al., Pathol Int 1988), and Huh7 were used in this study. Effects of K252a on the proliferation and the cell cycle were assessed by a commercialized kit (Promega) and flow cytometry, respectively. Protein expression and localization was analyzed by Western blot and immunocytochemistry, respectively. Cellular mRNA level was evaluated by real-time PCR using TaqMan probes. HAK-1B-based xenograft model in nude mice was used to evaluate in-vivo efficacy of K252a. Results: K252a suppressed proliferation and clearly caused G2 cell-cycle arrest in all the cell lines studied. Additionally, the agent induced both polygonal transformation in cell shape and increase in cell size in several HCC cell lines having endogenous mesenchymal features. In Western blot analysis and immunocytochemistry, the expression levels of E2A, an EMT-regulating transcriptional factor, were universally decreased in the cells treated with K252a, in concert with increased expression levels of E-cadherin in some cell lines. In real-time PCR analyses, the decrease in E2A mRNA levels and the increase in E-cadherin mRNA levels were ubiquitously found. Of note, xenografted tumor tissues obtained from mice treated with K252a exhibited significant increase in E-cadherin protein expression, in comparison with those from control mice. Conclusions: Our findings suggest that K252a has robust antitumor effects on HCC through, at least in part, reversing EMT and inducing G2 cell-cycle arrest. This kind of multikinase inhibitor may help us establish the proof-of-concept for closing escape routes in drug-resistant HCC cells.

Citation Format: Mitsuhiko Abe, Hironori Koga, Takafumi Yoshida, Hiroshi Masuda, Masahiro Sakata, Yu Ikezono, Toru Nakamura, Eitaro Taniguchi, Takumi Kawaguchi, Hirohisa Yano, Takuji Torimura, Michio Sata. The multikinase inhibitor K252a suppresses hepatocellular carcinoma tumor growth in a mouse xenograft model. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1047. doi:10.1158/1538-7445.AM2014-1047