Genetic and epigenetic silencing of SCARA5 may contribute to human hepatocellular carcinoma by activating FAK signaling
Jian Huang, … , Hua-Sheng Xiao, Ze-Guang Han
Jian Huang, … , Hua-Sheng Xiao, Ze-Guang Han
Published December 14, 2009
Citation Information: J Clin Invest. 2010;120(1):223-241. https://doi.org/10.1172/JCI38012.
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Research Article Oncology

Genetic and epigenetic silencing of SCARA5 may contribute to human hepatocellular carcinoma by activating FAK signaling

Abstract

The epigenetic silencing of tumor suppressor genes is a crucial event during carcinogenesis and metastasis. Here, in a human genome-wide survey, we identified scavenger receptor class A, member 5 (SCARA5) as a candidate tumor suppressor gene located on chromosome 8p. We found that SCARA5 expression was frequently downregulated as a result of promoter hypermethylation and allelic imbalance and was associated with vascular invasion in human hepatocellular carcinoma (HCC). Furthermore, SCARA5 knockdown via RNAi markedly enhanced HCC cell growth in vitro, colony formation in soft agar, and invasiveness, tumorigenicity, and lung metastasis in vivo. By contrast, SCARA5 overexpression suppressed these malignant behaviors. Interestingly, SCARA5 was found to physically associate with focal adhesion kinase (FAK) and inhibit the tyrosine phosphorylation cascade of the FAK-Src-Cas signaling pathway. Conversely, silencing SCARA5 stimulated the signaling pathway via increased phosphorylation of certain tyrosine residues of FAK, Src, and p130Cas; it was also associated with activation of MMP9, a tumor metastasis–associated enzyme. Taken together, these data suggest that the plasma membrane protein SCARA5 can contribute to HCC tumorigenesis and metastasis via activation of the FAK signaling pathway.

Authors

Jian Huang, Da-Li Zheng, Feng-Song Qin, Na Cheng, Hui Chen, Bing-Bing Wan, Yu-Ping Wang, Hua-Sheng Xiao, Ze-Guang Han

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Figure 8

SCARA5 physically associates with FAK and modulates the tyrosine phosphorylation of FAK, Src, and p130Cas.

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SCARA5 physically associates with FAK and modulates the tyrosine phospho...
(A) Colocalization of both SCARA5 (red) and FAK (green) in PLC/PRF/5 cells by immunofluorescence. The bottom right panel is enlarged from the boxed region of the bottom left image. Original magnification, ×1,000 (top row and bottom left panel); ×5,000 (bottom right panel). (B and C) Co-IP assays were performed in MHCC-LM3 cells transiently transfected with a pcDNA3.1 vector containing myc-tagged SCARA5. The cells transfected with empty vector were used as a control. Endogenous FAK was immunoprecipitated with the anti-myc antibody (B), while the myc-tagged SCARA5 was reciprocally immunoprecipitated using the anti-FAK antibody (C). Native mouse IgG was used as the negative control, and 5% of the total MHCC-LM3 cell lysate was used for input. (D) Overexpression of SCARA5 inhibits the tyrosine phosphorylation of FAK (Tyr-397), Src (Tyr-416), and p130Cas (Tyr-165) in MHCC-LM3 cells. SCARA5 knockdown by shRNA promotes phosphorylation in YY-8103 cells. The total levels of these proteins were assessed by immunoblotting with the corresponding antibodies. β-actin was used as a loading control. Quantification of FAK, Src, and p130Cas phosphorylation levels, as indicated by the numbers above the corresponding panels, was performed by normalizing the total FAK, Src, and p130Cas concentrations to the β-actin loading control. The activity of 2 MMPs, MMP-2 and MMP-9, was determined by the gelatin-based zymography assay. SCARA5 overexpression inhibits the activity of MMP-9 but not MMP-2 in MHCC-LM3 cells. SCARA5 knockdown by shRNA promotes the activity of MMP-9 in YY-8103 cells.