The aberrant processes driving hepatocellular carcinoma (HCC) are not fully understood. Lysophosphatidic acid receptors (LPAR) are commonly overexpressed in HCC, but their contributions to malignant development are not well established. In this report, we show that aberrant expression of LPAR6 sustains tumorigenesis and growth of HCC. Overexpression of LPAR6 in HCC specimens associated with poor survival in a cohort of 128 patients with HCC. We took a genetic approach to elucidate how LPAR6 sustains the HCC tumorigenic process, including through an expression profiling analysis to identify genes under the control of LPAR6. RNAi-mediated attenuation of LPAR6 impaired HCC tumorigenicity in tumor xenograft assays. Expression profiling and mechanistic analyses identified Pim-3 as a pathophysiologically relevant LPAR6 target gene. In nonmalignant cells where LPAR6 overexpression was sufficient to drive malignant character, Pim-3 was upregulated at the level of transcription initiation through a STAT3-dependent mechanism. A further analysis of HCC clinical specimens validated the connection between overexpression of LPAR6 and Pim-3, high proliferation rates, and poorer survival outcomes. Together, our findings establish LPAR6 as an important theranostic target in HCC tumorigenesis. Cancer Res; 75(3); 532-43. Ó2014 AACR.

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<p>Expression of LPAR1-5 mRNA levels in peritumoral and HCC cell lines (S1); Cell cycle analysis of LPAR6-knocked-down cells versus controls (S2); Absence of apoptosis in stably LPAR6-knocked-down cells (S3); LPAR6 knockdown impairs HCC migration and actin organization but not cells adhesion (S4); Ectopic expression of LPAR6 in human hepatocarcinoma cell line HLE (S5); LPAR6 knockdown affects the gene expression profile in HCC cells (S6); The PIM3 inhibitor, SGI-1776 decreases tumor growth in vivo and in vitro (S7).</p>

<p>Grouped genes according to their functions (analysis for comparative cellular processes) using the publicly available software ToppCluster multiple gene analyzer.</p>