Yoshihiko Kishima

Hepatoma-derived Growth Factor Stimulates Cell Growth after Translocation to the Nucleus by Nuclear Localization Signals

Hepatoma-derived growth factor (HDGF) is the original member of the HDGF family of proteins, which contains a well-conserved N-terminal amino acid sequence (homologous to the amino terminus of HDGF; hath) and nuclear localization signals (NLSs) in gene-specific regions other than the hath region. In addition to a bipartite NLS in a gene-specific region, an NLS-like sequence is also found in the hath region. In cells expressing green fluorescence protein (GFP)-HDGF, green fluorescence was observed in the nucleus, whereas it was detected in the cytoplasm of cells expressing GFP-HDGF with both NLSs mutated or deleted. GFP-hath protein (GFP-HATH) was distributed mainly in the nucleus, although some was present in the cytoplasm, whereas GFP-HDGF with a deleted hath region (HDGFnonHATH) was found only in the nucleus. Exogenously supplied GFP-HDGF was internalized and translocated to the nucleus. GFP-HATH was internalized, whereas GFP-HDGFnonHATH was not. Overexpression of HDGF stimulated DNA synthesis and cellular proliferation, although HDGF with both NLSs deleted did not. Overexpression of HDGFnonHATH caused a significant stimulation of DNA synthesis, whereas that of hath protein did not. HDGF containing the NLS sequence of p53 instead of the bipartite NLS did not stimulate DNA synthesis, and truncated forms without the C- or N-terminal side of NLS2 did not. These findings suggest that the gene-specific region, at least the bipartite NLS sequence and the N- and C-terminal neighboring portions, is essential for the mitogenic activity of HDGF after nuclear translocation.

Hepatoma‐derived growth factor is highly expressed in developing liver and promotes fetal hepatocyte proliferation

Hepatoma‐derived growth factor (HDGF) is a heparin‐binding protein, which has been purified from the conditioned media of HuH‐7 hepatoma cells. Recent studies have suggested the involvement of HDGF in development of the kidney and cardiovascular systems. In the present study, we investigated the possibility that HDGF was also involved in liver development. Northern blot and immunostaining revealed unique expression patterns of HDGF in liver development. HDGF expression was strongly detected in the fetal liver of the midgestation stage and was markedly decreased near birth. Its expression was mainly detected in stromal cells, including immature hepatocytes. Expression in hepatocytes decreased with differentiation. Administration of recombinant HDGF enhanced the growth of primary cultured fetal hepatocytes significantly, although the effect was small. The effect of exogenous HDGF on the proliferation of neonatal hepatocytes was also small and significant only at one point, despite the lower expression of endogenous HDGF, suggesting that the differences exist between fetal and neonatal hepatocytes. However, adenoviral introduction of HDGF antisense cDNA into the fetal hepatocytes significantly suppressed their proliferation, and the inhibitory effect of HDGF antisense virus was reversed by exogenous HDGF. In conclusion, HDGF helps regulate the hepatocyte proliferation in liver development. (HEPATOLOGY2002;36:1519–1527).

Expression of hepatoma-derived growth factor in hepatocarcinogenesis

Background and Aim:  The present study investigated the expression of hepatoma‐derived growth factor (HDGF) in human hepatocellular carcinoma (HCC) and in the liver during hepatocarcinogenesis in two rodent models.

Participation of hepatoma-derived growth factor in the regulation of fetal hepatocyte proliferation

The identification and characterization of hepatic stem cell compartments is the key to resolving clinical disorders and diseases in the liver. Hepatoblasts (or early fetal hepatocytes) fulfill several criteria of hepatic stem cells during liver development. Unlike mature hepatocytes, immature fetal hepatocytes can proliferate autonomously in the absence of any growth factors in vitro. However, the regulation of fetal hepatocyte proliferation remains unclear. Recently, we identified a novel factor, hepatoma-derived growth factor (HDGF), from the human hepatoma-derived cell line HuH-7, which autonomously proliferate in serum-free defined medium. Here, we focus on the functional roles of HDGF, and review several molecules involved in the growth regulation of hepatocytes in the immature stage.

Antibodies against hepatoma-derived growth factor and mucosal repair in ulcerative colitis

Ulcerative colitis is a chronic inflammatory disease of colonic mucosa in which the pathogenesis of any immunological disorders would likely be related. Various circulating autoantibodies have been reported in patients with ulcerative colitis, although their possible roles in this disease process have not yet been clarified. Autoantibody against hepatoma-derived growth factor (HDGF) was detected at high frequency in the serum of patients with ulcerative colitis, especially in patients with total colitis and left-sided colitis. In pursuit of the possible role of anti-HDGF autoantibody in the pathogenesis, we investigated HDGF expression in the intestinal mucosa by Western blotting and immunohis-tochemistry and the effects of recombinant proteins and antirecombinant HDGF antibody on the proliferation of the colonic epithelial cell-derived cell line, HT-29. HDGF was expressed in the nucleus of the colonic epithelial cells dominantly in the bottom of the crypts. Recombinant HDGF stimulated the proliferation of HT-29 cells significantly, although its effects were small, about 20% greater than the control at 100ng/ml. On the other hand, the polyclonal IgG antibody against recombinant HDGF generated by rabbits suppressed their proliferation almost completely at 250 μg/ml. These findings suggest that HDGF plays an important role in epithelial cell renewal of intestinal crypts as a growth and survival factor, and that autoantibody against HDGF may delay mucosal healing and repair by inhibiting the stimulatory effects of HDGF on epithelial cell proliferation, resulting in a chronic process of colonic mucosal injury.

Hepatoma-Derived Growth Factor: Involvement in Liver Development and Regeneration

Hepatoma-derived growth factor (HDGF) is the first member of a new gene family that contains the HATH (homologous to the amino-terminus of HDGF) region in the N-terminal region and nuclear localization signals in the remaining parts of the sequence and traffic to the nucleus. HDGF was purified from the conditioned medium of HuH-7 hepatoma cells by DNA synthesis stimulating activity for Swiss 3T3 cells. HDGF stimulates the proliferation of endothelial cells, vascular smooth muscle cells, some hepatoma cells, and fibroblasts. HDGF is ubiquitously expressed in normal tissues, predominantly in testis, kidney, liver, heart, and brain. Recent studies have indicated that HDGF may play important roles in fetal organ development and tissue repair, such as renal glomerular formation and vascular smooth muscle cell proliferation during vascular development and neointima formation. HDGF was highly expressed in fetal liver and mainly in fetal hepatocytes with little expression in hematopoietic cells. HDGF expression in fetal hepatocytes decreased in accordance with the differentiation to mature hepatocytes. HDGF expression was significantly induced in regenerating liver after partial hepatectomy and drug-induced liver damage in adult liver. We assume that HDGF is significantly involved in liver development and regeneration.