LAUSR

BACKGROUND Inosine monophosphate dehydrogenase (IMPDH) is the key enzyme in the biosynthesis of purine nucleotides. IMPDH1 and IMPDH2 are the two isoforms of IMPDH and they share 84% amino acid similarity and virtually indistinguishable catalytic activity. Although high expression of IMPDH2 has been reported in various cancers, the roles of IMPDH1 in hepatocellular carcinoma (HCC) are largely unknown. METHODS The expression and the clinical relevance of IMPDH1 in 154 HCC patients were detected by immunohistochemistry analysis. The stable IMPDH1 knockdown HuH7 cells were established by lentiviral RNAi approach. The single cell proliferation was detected by colony-forming unit assay. The tumor initiation and growth ability were measured by using xenograft tumor model in immunodeficient mice. The effect of IMPDH1 on cellular signaling pathways was analyzed by genome-wide transcriptomic profiling. RESULTS The expression of IMPDH1 is upregulated in tumor tissue compared with adjacent liver tissue, and higher expression of IMPDH1 is associated with better patient cumulative survival. In experimental models, loss of IMPDH1 in HCC cells inhibits the ability of single cell colony formation in vitro, and reduces the efficiency of tumor initiation and growth in immunodeficient mice. Consistently, loss of IMPDH1 results in distinct alterations of signaling pathways revealed by genome-wide transcriptomic profiling. CONCLUSION IMPDH1 sustains HCC growth and progression.