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

Hepatoma-Derived Growth Factor: An Overview and Its Role as a Potential Therapeutic Target Molecule for Digestive Malignancies

Hepatoma-derived growth factor (HDGF) was identified in research seeking to find a novel growth factor for hepatoma cells. Subsequently, four HDGF-related proteins were identified, and these proteins are considered to be members of a new gene family. HDGF has a growth-stimulating role, an angiogenesis-inducing role, and a probable anti-apoptotic role. HDGF is ubiquitously expressed in non-cancerous tissues, and participates in organ development and in the healing of damaged tissues. In addition, the high expression of HDGF was reported to be closely associated with unfavorable clinical outcomes in several malignant diseases. Thus, HDGF is considered to contribute to the development and progression of malignant disease. We herein provide a brief overview of the factor and its functions in relation to benign and malignant cells. We also describe its possible role as a target molecule for digestive malignancies.

Hepatoma-derived growth factor participates in Helicobacter Pylori-induced neutrophils recruitment, gastritis and gastric carcinogenesis

Helicobacter pylori (Hp) infection and overexpression of hepatoma-derived growth factor (HDGF) are involved in gastric carcinogenesis. However, the relationship between Hp-induced gastric diseases and HDGF upregulation is not yet completely clear. This study aimed to elucidate the role of HDGF in Hp-induced gastric inflammation and carcinogenesis. HDGF expression in gastric biopsy and serum from patients was analyzed by immunohistochemical and ELISA analysis, respectively. Hp and gastric cells coculture system was employed to delineate the mechanism underlying HDGF overexpression during Hp infection. The gastric pathologies of wild type and HDGF knockout mice after Hp infection were investigated by immunohistochemical, immunoblot, and immunofluorescence analyses. HDGF level was significantly elevated in patients with Hp infection or intestinal metaplasia (IM, a precancerous lesion), and HDGF overexpression was positively correlated with Hp load, IM, and neutrophil infiltration in gastric biopsy. Consistently, patients with Hp infection or IM had significantly higher serum HDGF level. By using coculture assay, Hp infection led to HDGF upregulation and secretion in gastric cells. In mice model, HDGF ablation significantly suppressed the Hp-induced neutrophil infiltration and inflammatory TNF-α/COX-2 signaling, thereby relieving the tissue damage in stomach. This was further supported by that recombinant HDGF (rHDGF) stimulated the differentiation/chemotaxis of cultured neutrophils and oncogenic behaviors of gastric cells. Time series studies showed that Hp infection elicited an inflammatory TNF-α/HDGF/COX-2 cascade in stomach. HDGF secretion by Hp infection promotes the neutrophils infiltration and relays Hp-induced inflammatory signaling. Thus, HDGF may constitute a novel diagnostic marker and therapeutic target for Hp-induced gastritis and carcinogenesis.

Hepatoma-derived growth factor and nucleolin exist in the same ribonucleoprotein complex

BACKGROUND

Hepatoma-derived growth factor (HDGF) is a protein which is highly expressed in a variety of tumours. HDGF has mitogenic, angiogenic, neurotrophic and antiapoptotic activity but the molecular mechanisms by which it exerts these activities are largely unknown nor has its biological function in tumours been elucidated. Mass spectrometry was performed to analyse the HDGFStrep-tag interactome. By Pull-down-experiments using different protein and nucleic acid constructs the interaction of HDGF and nucleolin was investigated further.

RESULTS

A number of HDGFStrep-tag copurifying proteins were identified which interact with RNA or are involved in the cellular DNA repair machinery. The most abundant protein, however, copurifying with HDGF in this approach was nucleolin. Therefore we focus on the characterization of the interaction of HDGF and nucleolin in this study. We show that expression of a cytosolic variant of HDGF causes a redistribution of nucleolin into the cytoplasm. Furthermore, formation of HDGF/nucleolin complexes depends on bcl-2 mRNA. Overexpression of full length bcl-2 mRNA increases the number of HDGF/nucleolin complexes whereas expression of only the bcl-2 coding sequence abolishes interaction completely. Further examination reveals that the coding sequence of bcl-2 mRNA together with either the 5' or 3' UTR is sufficient for formation of HDGF/nucleolin complexes. When bcl-2 coding sequence within the full length cDNA is replaced by a sequence coding for secretory alkaline phosphatase complex formation is not enhanced.

CONCLUSION

The results provide evidence for the existence of HDGF and nucleolin containing nucleoprotein complexes which formation depends on the presence of specific mRNAs. The nature of these RNAs and other components of the complexes should be investigated in future.

Overexpression of hepatoma-derived growth factor in melanocytes does not lead to oncogenic transformation

BACKGROUND

HDGF is a growth factor which is overexpressed in a wide range of tumors. Importantly, expression levels were identified as a prognostic marker in some types of cancer such as melanoma.

METHODS

To investigate the presumed oncogenic/transforming capacity of HDGF, we generated transgenic mice overexpressing HDGF in melanocytes. These mice were bred with mice heterozygous for a defective copy of the Ink4a tumor suppressor gene and were exposed to UV light to increase the risk for tumor development both genetically and physiochemically. Mice were analyzed by immunohistochemistry and Western blotting. Furthermore, primary melanocytes were isolated from different strains created.

RESULTS

Transgenic animals overexpressed HDGF in hair follicle melanocytes. Interestingly, primary melanocytes isolated from transgenic animals were not able to differentiate in vitro whereas cells isolated from wild type and HDGF-deficient animals were. Although, HDGF-/-/Ink4a+/- mice displayed an increased number of epidermoid cysts after exposure to UV light, no melanomas or premelanocytic alterations could be detected in this mouse model.

CONCLUSIONS

The results therefore provide no evidence that HDGF has a transforming capacity in tumor development. Our results in combination with previous findings point to a possible role in cell differentiation and suggest that HDGF promotes tumor progression after secondary upregulation and may represent another protein fitting into the concept of non-oncogene addiction of tumor tissue.

Immunogenicity of SEREX-identified antigens and disease outcome in pancreatic cancer

Despite spontaneous or vaccination-induced immune responses, pancreatic cancer remains one of the most deadly immunotherapy-resistant malignancies. We sought to comprehend the spectrum of pancreatic tumor-associated antigens (pTAAs) and to assess the clinical relevance of their immunogenicity. An autologous SEREX-based screening of a cDNA library constructed from a pancreatic T3N0M0/GIII specimen belonging to a long-term survivor (36 months) revealed 18 immunogenic pTAA. RT-PCR analysis displayed broad distribution of the identified antigens among normal human tissues. PNLIPRP2 and MIA demonstrated the most distinct pancreatic cancer-specific patterns. ELISA-based screening of sera for corresponding autoantibodies revealed that although significantly increased, the immunogenicity of these molecules was not a common feature in pancreatic cancer. QRT-PCR and immunohistochemistry characterized PNLIPRP2 as a robust acinar cell-specific marker whose decreased expression mirrored the disappearance of parenchyma in the diseased organ, but was not related to the presence of PNLIPRP2 autoantibodies. Analyses of MIA-known to be preferentially expressed in malignant cells-surprisingly revealed an inverse correlation between intratumoral gene expression and the emergence of autoantibodies. MIA(high) patients were autoantibody-negative and had shorter median survival when compared with autoantibody-positive MIA(low) patients (12 vs. 34 months). The observed pTAA spectrum comprised molecules associated with acinar, stromal and malignant structures, thus presenting novel targets for tumor cell-specific therapies as well as for approaches based on the bystander effects. Applying the concept of cancer immunoediting to interpret relationships between gene expression, antitumor immune responses, and clinical outcome might better discriminate between past and ongoing immune responses, consequently enabling prognostic stratification of patients and individual adjustment of immunotherapy.

Hepatoma-derived growth factor. Significance of amino acid residues 81-100 in cell surface interaction and proliferative activity

Hepatoma-derived growth factor (HDGF) has proliferative, angiogenic, and neurotrophic activity. It plays a putative role in the development and progression of cancer. When expressed in cells, the mitogenic activity of HDGF depends on its nuclear localization, but it also stimulates proliferation when added to the cell culture medium. A cell surface receptor for HDGF has not been identified so far. We investigated the interaction of various purified recombinant HDGF fusion proteins with the cell surface of NIH 3T3 fibroblasts. We showed that binding of a HDGF-beta-galactosidase fusion protein to the cell surface of NIH 3T3 fibroblasts was saturable, occurred with high affinity (K(D) = 14 nm), and had a proliferative effect. We identified a peptide comprising amino acid residues 81-100 within the amino-terminal part of HDGF that bound to the cell surface of NIH 3T3 cells with saturation and affinity values similar to those of HDGF. When added to primary human fibroblasts, this peptide stimulated proliferation. Substitution of a single amino acid (K96A) within this peptide was sufficient to abolish its binding to the cell surface and its proliferative activity. In contrast, when expressed transiently in NIH 3T3 cells, a HDGF-beta-galactosidase fusion protein in which amino acid residues 81-100 were deleted still had proliferative activity, whereas a fusion protein containing only the 81-100 peptide did not. Our results suggest the existence of a plasma membrane-located HDGF receptor for which signaling depends on amino acid residues 81-100 of HDGF. This region differs from the one that has been recently identified to be essential for mitogenic activity depending on the nuclear localization of HDGF. Thus, HDGF exerts its proliferative activity via two different pathways.

Hepatoma-derived growth factor is involved in lung remodeling by stimulating epithelial growth

Lung epithelial cells have an integral role in the maintenance of lung homeostasis; however, the regulatory mechanism thereof has not been fully clarified. Recently, hepatoma-derived growth factor (HDGF) was reported to be involved in organ development and remodeling through its mitogenic effect. We investigated the biological role of HDGF in lung remodeling. HDGF was more highly expressed in the lungs of idiopathic pulmonary fibrosis, chiefly in the epithelial cells, than in control nonfibrotic lungs. We also confirmed the expression of HDGF protein and mRNA in the lungs of bleomycin-instilled mice, mainly in the bronchial and alveolar epithelial cells, by immunohistochemical analysis and in situ hybridization. We found that recombinant HDGF promoted DNA synthesis in rat alveolar epithelial cells and A549 cells in vitro. Endogenous HDGF overexpressed by gene transfer was translocated into the nucleus and promoted the proliferation of A549 cells. In vivo intratracheal instillation of recombinant HDGF induced the proliferation of bronchial and alveolar epithelial cells without causing marked interstitial inflammation. These findings suggest that HDGF may be involved in lung remodeling after injury by promoting the proliferation of lung epithelial cells, probably in an autocrine manner.