Abstract 920: Melanoma differentiation associated gene-9/syndecan binding protein (mda-9/sdcbp): A positive regulator of hepatocellular carcinoma
Authors: Manna Debashri , Reghupaty Saranya Chidambaranathan , Mendoza Rachel Gredler , Camarena Maria Del , Subler Mark A. , Koblinski Jennifer , Martin Rebecca , Dozmorov Mikhail G. , Das Swadesh K. , Windle Jolene J. , Fisher Paul B. , Sarkar Devanand 
Published: June 2022

Abstract
Background: Hepatocellular carcinoma (HCC) is a major clinical challenge because of increasing rates of incidence and mortality, and high resistance to standard radio- and chemotherapy. Identification of novel molecules regulating HCC facilitates development of targeted therapies having a lasting impact on HCC patient survival. The oncogene MDA-9/SDCBP promotes tumorigenesis and metastasis in many cancers. In The Cancer Genome Atlas (TCGA), 8% of HCC patients show amplification of MDA-9 gene. However, the role of MDA-9 in regulating HCC has not been well-studied.
Objective: To unravel the function of MDA-9 in HCC using a transgenic mouse model with hepatocyte-specific overexpression of MDA-9 (Alb/MDA-9).
Study design: Alb/MDA-9 mice were generated in B6/CBA background by using the mouse albumin promoter/enhancer element to drive human MDA-9 expression. N-nitrosodiethylamine (DEN)/phenobarbital (PB) was used for induction of HCC. Tumor immune profile was analyzed by Opal multiplex staining and flow cytometry. RNA-sequencing (RNA-seq) was performed to analyze MDA-9-mediated gene regulation.
Results: At 18 months of age, none of the WT mice developed liver tumor, while one male and one female Alb/MDA-9 mice (n = 11) developed one isolated tumor each, suggesting that MDA-9 may not be a strong driver oncogene, rather it might promote HCC progression once tumor is initiated. Indeed, at 32 weeks after induction of HCC using DEN/PB, tumor burden in the livers of Alb/MDA-9 mice was significantly higher compared to WT. These tumors showed loss of hepatic architecture and hepatocyte ballooning, features of HCC. Increased staining for the proliferation marker PCNA, HCC markers AFP and cytokeratin, and angiogenesis marker CD31 in tumor sections, and significantly increased levels of serum liver enzymes, AST and ALT, were observed in Alb/MDA-9 mice vs WT. Macrophage-mediated inflammation plays a central role in HCC. Compared to WT, Alb/MDA-9 tumors showed marked infiltration of CD11b+ myeloid cells, FoxP3+ T regulatory cells and F4/80+ macrophages. RNA-seq in naïve WT and Alb/MDA-9 hepatocytes identified activation of signaling pathways associated with invasion, angiogenesis and inflammation.
Conclusions: MDA-9 overexpression in hepatocytes promotes HCC by stimulating inflammation, angiogenesis and immune modulation. Studies are ongoing to obtain in-depth understanding of the molecular mechanisms by which MDA-9 exerts these pleiotropic effects. This study was supported by NIH/NCI Grant 1R01CA244993-01 (DS and PBF).
Citation Format: Debashri Manna, Saranya Chidambaranathan Reghupaty, Rachel Gredler Mendoza, Maria Del Camarena, Mark A. Subler, Jennifer Koblinski, Rebecca Martin, Mikhail G. Dozmorov, Swadesh K. Das, Jolene J. Windle, Paul B. Fisher, Devanand Sarkar. Melanoma differentiation associated gene-9/syndecan binding protein (mda-9/sdcbp): A positive regulator of hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 920.