Analysis of Lymphocyte Specific Protein‐1 (LSP‐1) expression in normal primary rat hepatocytes and liver following partial hepatectomy

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Hepatocellular carcinoma (HCC), the most frequently diagnosed form of liver cancer, is associated with high mortality rates. A recent finding of our laboratory shows that a portion of the gene for lymphocyte‐specific protein 1 (LSP1), an intracellular F‐actin binding protein expressed in neutrophils, macrophages and endothelial cells, is deleted or amplified in a majority of HCCs evaluated. The deletions of LSP‐1 correlated with large tumor size indicating that LSP‐1 may play an inhibitory role in hepatocyte growth. Based on these findings, we hypothesize that LSP‐1 expression is a critical regulator of cellular growth underlying HCC development. However, the expression of LSP‐1 in hepatocytes and normal liver remains to be elucidated. Utilizing immunoblotting and Reverse Transcriptase PCR (RT‐PCR), we examined the total protein and mRNA expression of LSP‐1 in primary rat hepatocytes in vitro and in rat liver tissue after partial hepatectomy. In the rat, LSP‐1 has three known splicing variants; therefore we will examine the expression of the isoforms of LSP‐1 using RT‐PCR with isoform specific LSP‐1 primers. Results from both immunoblotting and RT‐PCR experiments indicate that primary rat hepatocytes and tissue from partial hepatectomized livers express LSP‐1 and that the expression correlates inversely with the rate of growth. Future studies aim to address the function of LSP‐1 in normal and diseased liver states and whether LSP‐1 plays a critical role in hepatocyte growth. Research supported by grant 5T32HL094295‐02.