Vasodilator‐stimulated phosphoprotein promotes activation of hepatic stellate cells by regulating Rab11‐dependent plasma membrane targeting of transforming growth factor beta receptors

• DOI: 10.1002/hep.27251
• Publication Date: 2014-06-10T14:24:24Z
• Authors: Kangsheng Tu; Jiachu Li; Vikas K. Verma; Chunsheng Liu; Daniel D. Billadeau; Georg Lamprecht; Xiaoyu Xiang; Luyang Guo; Renumathy Dhanase...; Lewis R. Roberts; Vijay H. Shah; Ningling Kang
• Keywords: 0301 basic medicine; Cell Membrane; Microfilament Proteins; Receptor, Transforming Growth Factor-beta Type II; Protein Serine-Threonine Kinases; Phosphoproteins; 3. Good health; Gene Expression Regulation, Neoplastic; Mice; 03 medical and health sciences; Liver Neoplasms, Experimental; Cell Movement; Gene Knockdown Techniques; Paracrine Communication; Hepatic Stellate Cells; Animals; Humans; Colorectal Neoplasms; Myofibroblasts; Cell Adhesion Molecules; HT29 Cells; Receptors, Transforming Growth Factor beta; Cell Proliferation

Liver microenvironment is a critical determinant for development and progression of liver metastasis. Under transforming growth factor beta (TGF‐β) stimulation, hepatic stellate cells (HSCs), which are liver‐specific pericytes, transdifferentiate into tumor‐associated myofibroblasts that promote tumor implantation (TI) and growth in the liver. However, the regulation of this HSC activation process remains poorly understood. In this study, we tested whether vasodilator‐stimulated phosphoprotein (VASP) of HSCs regulated the TGF‐β‐mediated HSC activation process and tumor growth. In both an experimental liver metastasis mouse model and cancer patients, colorectal cancer cells reaching liver sinusoids induced up‐regulation of VASP and alpha‐smooth muscle actin (α‐SMA) in adjacent HSCs. VASP knockdown in HSCs inhibited TGF‐β‐mediated myofibroblastic activation of HSCs, TI, and growth in mice. Mechanistically, VASP formed protein complexes with TGF‐β receptor II (TβRII) and Rab11, a Ras‐like small GTPase and key regulator of recycling endosomes. VASP knockdown impaired Rab11 activity and Rab11‐dependent targeting of TβRII to the plasma membrane, thereby desensitizing HSCs to TGF‐β1 stimulation. Conclusions: Our study demonstrates a requirement of VASP for TGF‐β‐mediated HSC activation in the tumor microenvironment by regulating Rab11‐dependent recycling of TβRII to the plasma membrane. VASP and its effector, Rab11, in the tumor microenvironment thus present therapeutic targets for reducing TI and metastatic growth in the liver. (Hepatology 2015;61:361–374)