Lymphocyte Specific Protein‐1 suppresses TCPOBOP induced hepatocellular proliferation

Abstract

Lymphocyte specific protein‐1 (LSP‐1), an f‐actin binding protein expressed in hematopoietic cells as well as hepatocytes, is the gene with the most copy number variations detected in human HCC. Our previous work has demonstrated that LSP‐1 suppresses hepatocellular proliferation following partial hepatectomy as well as in primary hepatocyte cultures. LSP‐1 acts as a scaffold for the Ras/MEK/ERK MAP kinase pathway and along with kinase suppressor of Ras (KSR) inhibits ERK phosphorylation and thus its activation preventing downstream signaling to induce cellular proliferation and migration. To determine if LSP‐1 functions to attenuate hepatocellular growth in models which induce proliferation without loss of tissue or liver injury, we aimed to explore if LSP‐1 can modulate TCPOBOP induced hepatocellular proliferation and hepatomegaly. TCPOBOP (1,4‐Bis [2‐(3,5‐Dichloropyridyloxy)] benzene), a constitutive androstane receptor (CAR) agonist, has been shown to induce hepatocellular hyperplasia through a CAR dependent mechanism. Since LSP‐1 has been shown to suppress hepatocyte proliferation during liver regeneration following partial hepatectomy and in culture, we hypothesized that LSP‐1 will attenuate TCPOBOP driven hepatocellular proliferation. In this study, we administered TCPOBOP to both a global LSP1 knockout mouse model as well as a hepatocyte specific LSP‐1 transgenic (TG) mouse model. Livers were harvested at various time point after TCPOBOP gavage and proliferation was measured using Ki67 and PCNA immunohistochemistry as well as liver to body weight ratios. Increased LSP‐1 expression in the transgenic livers caused decreased Ki67 staining on day 2 after TCPOBOP administration as well as no measurable change in liver to body weight ratios as compared to baseline. However, by day 5, the TG liver to body weight ratios increased above those of the WT but the percentage of Ki67 positive hepatocytes was decreased in the TG as compared to the wild type controls. Loss of LSP‐1 expression led to a statistically significant difference in the liver to body weight ratios between the KO and WT mice on day 2 after TCPOBOP administration as well as increased hepatocellular proliferation on both days 2 and 5 after gavage in the KO livers. CAR target genes and downstream signaling pathways that are modulated by LSP‐1 expression will be analyzed.ConclusionLSP‐1 attenuates TCPOBOP induced hepatocellular proliferation and loss of expression leads to increased hyperplasia supporting the role of LSP‐1 as a growth suppressor.Support or Funding InformationSupported by the Department of Defense grant CA160119, the University of Pittsburgh Menten Endowment, and the Cleveland Foundation Morningstar Fund.