Liver damage and fibrosis are precursors of hepatocellular carcinoma (HCC). In HCC patients, sorafenib—a multikinase inhibitor drug—has been reported to exert anti-fibrotic activity. However, incomplete inhibition of RAF activity by sorafenib may also induce paradoxical activation of the mitogen-activated protein kinase (MAPK) pathway in malignant cells. The consequence of this effect in non-malignant disease (hepatic fibrosis) remains unknown. This study aimed to examine the effects of sorafenib on activated hepatic stellate cells (HSCs), and develop effective therapeutic approaches to treat liver fibrosis and prevent cancer development.Methods: We first examined the effects of sorafenib in combination with MEK inhibitors on fibrosis pathogenesis in vitro and in vivo. To improve the bioavailability and absorption by activated HSCs, we developed CXCR4-targeted nanoparticles (NPs) to co-deliver sorafenib and a MEK inhibitor to mice with liver damage.Results: We found that sorafenib induced MAPK activation in HSCs, and promoted their myofibroblast differentiation. Combining sorafenib with a MEK inhibitor suppressed both paradoxical MAPK activation and HSC activation in vitro, and alleviated liver fibrosis in a CCl4-induced murine model of liver damage. Furthermore, treatment with sorafenib/MEK inhibitor-loaded CXCR4-targeted NPs significantly suppressed hepatic fibrosis progression and further prevented fibrosis-associated HCC development and liver metastasis.Conclusions: Our results show that combined delivery of sorafenib and a MEK inhibitor via CXCR4-targeted NPs can prevent activation of ERK in activated HSCs and has anti-fibrotic effects in the CCl4-induced murine model. Targeting HSCs represents a promising strategy to prevent the development and progression of fibrosis-associated HCC.

No abstract

The progression of liver fibrosis, an intrinsic response to chronic liver injury, is associated with hepatic hypoxia, angiogenesis, abnormal inflammation, and significant matrix deposition, leading to the development of cirrhosis and hepatocellular carcinoma (HCC). Due to the complex pathogenesis of liver fibrosis, antifibrotic drug development has faced the challenge of efficiently and specifically targeting multiple pathogenic mechanisms. Therefore, CXCR4-targeted nanoparticles (NPs) were formulated to deliver siRNAs against vascular endothelial growth factor (VEGF) into fibrotic livers to block angiogenesis during the progression of liver fibrosis. AMD3100, a CXCR4 antagonist that was incorporated into the NPs, served dual functions: it acted as a targeting moiety and suppressed the progression of fibrosis by inhibiting the proliferation and activation of hepatic stellate cells (HSCs). We demonstrated that CXCR4-targeted NPs could deliver VEGF siRNAs to fibrotic livers, decrease VEGF expression, suppress angiogenesis and normalize the distorted vessels in the fibrotic livers in the carbon tetrachloride (CCl4) induced mouse model. Moreover, blocking SDF-1α/CXCR4 by CXCR4-targeted NPs in combination with VEGF siRNA significantly prevented the progression of liver fibrosis in CCl4-treated mice. In conclusion, the multifunctional CXCR4-targeted NPs delivering VEGF siRNAs provide an effective antifibrotic therapeutic strategy.

Sorafenib is the only systemic therapy approved for advanced hepatocellular carcinoma (HCC). Sorafenib's efficacy has been attributed in part to inhibition of cancer cell proliferation due to B- and CRAF targeting in HCC cells. However, cell autonomous mechanisms promote evasion from sorafenib treatment, leading to moderate survival benefit. Herein, we demonstrated that the effects of sorafenib on HCC cell viability were initially independent of RAF kinase inhibition and were mediated in part by p38MAPK inhibition. Moreover, sorafenib treatment led to RAF heterodimerization (BRAF/CRAF) and subsequent ERK activation and thus converted HCC cell dependence for survival signaling to the RAF/ERK pathway. Inhibition of ERK pathway by the MEK inhibitor AZD6244 significantly enhanced the therapeutic efficacy of sorafenib efficacy on HCC in vitro and in vivo. Furthermore, we developed HCC-targeted nanoparticles (NPs) to efficiently co-deliver both sorafenib and AZD6244 into HCC, downregulate RAF/ERK pathway, suppress angiogenesis and enhance anti-cancer effect in the orthotopic HCC model. In conclusion, sorafenib treatment leads to rapid MAPK activation due to BRAF heterodimerization as a cell-autonomous mechanism of treatment resistance. Co-delivery of sorafenib and MEK inhibitor AZD6244 using HCC targeted NPs downregulates the compensatory activated RAF/ERK pathway and overcomes resistance to sorafenib in HCC. Citation Format: Yunching Chen, Ya-Chi Liu, Ts-Ting Lin, Rakesh Ramjiawan, Dan Duda. Nanoparticles targeting RAF/ERK-driven cell-autonomous resistance to sorafenib for effective treatment of hepatocellular carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1315.