| In the present study, we investigated the structure, expression, function and biological significance of liver-specific gene LFIRE-l/HFREP-1 and its mouse orthologous gene MFREP-1 during hepatocarcinogenesis/liver regeneration model. Next, we also probed the molecular mechanism of the effect of natural short-chain fatty acid glyceride-tributyrin on gastric cancer.(1) Our lab has previously cloned the liver-specific sequence-LFIRE-1 by DD-PCR. Now we found LFIRE-1 and a function-unknown gene-HFREP-1 are two alternative splicing forms of the same gene-LFIRE-l/HFREP-1. LFIRE-l/HFREP-1 maps to human chromosome 8p22 and is composed by 8 exons. LFIRE-l/HFREP-1 gene encodes a 312-a.a secretory protein. LFIRE-l/HFREP-1 expresses selectively in normal human liver tissue, and is down-regulated in 58.3% of human hepatocellular carcinoma specimens by Northern blot and RT-PCR assay. Immunohistochemical assessment also confirmed the down-regulated expressionpattern. Antisense oligonucleotides treatment was applied to reduce the endogenous expression of LFIRE-l/HFREP-1 in HepG2 cells, resulting in accelerated cell growth; while restoration of LFIRE-l/HFREP-1 in BEL-7402 and BEL-7404 HCC cells can inhibit the growth and tumorigenicity of liver cancer cells. Comparing allelic status at LFIRE-1 locus with expression of LFIRE-1 mRNA, we found 12 out of 17 tumors with LOH showed down-regulated expression among 26 HCC specimens. In contrast, only 1 tumor expressed less LFIRE-1 in the other 9 tumors without LOH. PCR-SSCP analysis and sequencing revealed somatic mutations in 3 out of 45 cases of hepatocellular carcinoma; two of them lost the remaining allele. The results above demonstrated the liver-specific gene LFIRE-l/HFREP-1 was frequently down-regulated in hepatocellular carcinoma and may have the growth inhibitory activity against liver cancer cells.(2) We first cloned the mouse ortholog gene-MFREP-1 toLFIRE-l/HFREP-1. The gene encodes a 314-a.a. protein, which shares 80.4% homologue to LFIRE-l/HFREP-1. MFREP-1 is also a liver-specific gene, and expression level was up-regulated in 70% partial hepatectomy model and maintained at high level during the late-phase of liver regeneration. It indicated that MFREP-1 plays an important role in liver regeneration and may be involved in cell growth regulation.(3) We investigated the effects of natural neutral short-chain fatty acid glyceride-tributyrin on cells growth, DNA synthesis and apoptosis of the gastric cancer cell SGC-7901. These data demonstrated that tributyrin can efficientlyinhibit gastric cancer cell growth by inhibiting DNA synthesis and inducing apoptosis. The tributyrin-induced apoptosis is associated with down-regulation of Bcl-2 expression and up-regulation of Bax expression. Thus, tributyrin may be a potential chemopreventive and chemotherapeutic agent against human gastric cancer.
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