Downregulation of hepatoma-derived growth factor activates the Bad-mediated apoptotic pathway in human cancer cells

Hepatocyte-Specific Triggering of Hepatic Stellate Cell Profibrotic Activation by Apoptotic Bodies: The Role of Hepatoma-Derived Growth Factor, HIV, and Ethanol

Liver disease is one of the leading comorbidities in HIV infection. The risk of liver fibrosis development is potentiated by alcohol abuse. In our previous studies, we reported that hepatocytes exposed to HIV and acetaldehyde undergo significant apoptosis, and the engulfment of apoptotic bodies (ABs) by hepatic stellate cells (HSC) potentiates their pro-fibrotic activation. However, in addition to hepatocytes, under the same conditions, ABs can be generated from liver-infiltrating immune cells. The goal of this study is to explore whether lymphocyte-derived ABs trigger HSC profibrotic activation as strongly as hepatocyte-derived ABs. ABs were generated from Huh7.5-CYP2E1 (RLW) cells and Jurkat cells treated with HIV+acetaldehyde and co-culture with HSC to induce their pro-fibrotic activation. ABs cargo was analyzed by proteomics. ABs generated from RLW, but not from Jurkat cells activated fibrogenic genes in HSC. This was driven by the expression of hepatocyte-specific proteins in ABs cargo. One of these proteins is Hepatocyte-Derived Growth Factor, for which suppression attenuates pro-fibrotic activation of HSC. In mice humanized with only immune cells but not human hepatocytes, infected with HIV and fed ethanol, liver fibrosis was not observed. We conclude that HIV+ABs of hepatocyte origin promote HSC activation, which potentially may lead to liver fibrosis progression.

MiR-129-5p exerts Wnt signaling-dependent tumor-suppressive functions in hepatocellular carcinoma by directly targeting hepatoma-derived growth factor HDGF

BACKGROUND

In hepatocellular carcinoma (HCC), histone deacetylases (HDACs) are frequently overexpressed. This results in chromatin compaction and silencing of tumor-relevant genes and microRNAs. Modulation of microRNA expression is a potential treatment option for HCC. Therefore, we aimed to characterize the epigenetically regulated miR-129-5p regarding its functional effects and target genes to understand its relevance for HCC tumorigenesis.

METHODS

Global miRNA expression of HCC cell lines (HLE, HLF, Huh7, HepG2, Hep3B) and normal liver cell lines (THLE-2, THLE-3) was analyzed after HDAC inhibition by miRNA sequencing. An in vivo xenograft mouse model and in vitro assays were used to investigate tumor-relevant functional effects following miR-129-5p transfection of HCC cells. To validate hepatoma-derived growth factor (HDGF) as a direct target gene of miR-129-5p, luciferase reporter assays were performed. Survival data and HDGF expression were analyzed in public HCC datasets. After siRNA-mediated knockdown of HDGF, its cancer-related functions were examined.

RESULTS

HDAC inhibition induced the expression of miR-129-5p. Transfection of miR-129-5p increased the apoptosis of HCC cells, decreased proliferation, migration and ERK signaling in vitro and inhibited tumor growth in vivo. Direct binding of miR-129-5p to the 3'UTR of HDGF via a noncanonical binding site was validated by luciferase reporter assays. HDGF knockdown reduced cell viability and migration and increased apoptosis in Wnt-inactive HCC cells. These in vitro results were in line with the analysis of public HCC datasets showing that HDGF overexpression correlated with a worse survival prognosis, primarily in Wnt-inactive HCCs.

CONCLUSIONS

This study provides detailed insights into the regulatory network of the tumor-suppressive, epigenetically regulated miR-129-5p in HCC. Our results reveal for the first time that the therapeutic application of mir-129-5p may have significant implications for the personalized treatment of patients with Wnt-inactive, advanced HCC by directly regulating HDGF. Therefore, miR-129-5p is a promising candidate for a microRNA replacement therapy to prevent HCC progression and tumor metastasis.

Electrochemical biosensors based on peptide-kinase interactions at the kinase docking site

Kinases are important cancer biomarkers and are conventionally detected based on their catalytic activity. Kinases regulate cellular activities by phosphorylation of motif-specific multiple substrate proteins, resulting in a lack of selectivity of activity-based kinase biosensors. We present an alternative approach of sensing kinases based on the interactions of their allosteric docking sites with a specific partner protein. The new approach was demonstrated for the ERK2 kinase and its substrate ELK-1. A peptide derived from ELK-1 was bound to a gold electrode and ERK2 sensing was performed by electrochemical impedance spectroscopy. We performed a detailed analysis of the interaction between the ELK-1 peptide and the kinase on gold surfaces. Atomic force microscopy, variable angle spectroscopic ellipsometry, X-ray Photoelectron Spectroscopy, and polarization modulation IR reflection-absorption spectroscopy analysis of the gold surface revealed the adsorbed layer of the ERK2 on the peptide monolayer. The sensors showed a high level of target selectivity for ERK2 compared to the p38γ kinase and BSA. ERK2 was detected in its cellular concentration range, 0.5-2.0 μM, and the limit of detection was calculated to be 0.35 μM. Using the flexibility of peptide design, our method is generic for developing sensitive and substrate-specific biosensors and other disease-related enzymes based on their interactions.

Blocking Hepatoma-Derived Growth Factor Attenuates Vasospasm and Neuron Cell Apoptosis in Rats Subjected to Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is an important subcategory of stroke due to its unacceptably high mortality rate as well as the severe complications it causes, such as cerebral vasospasm, neurological deficits, and cardiopulmonary abnormality. Hepatoma-derived growth factor (HDGF) is a growth factor related to normal development and is involved in liver development and regeneration. This study explored the relationship between SAH and HDGF. Sixty rats were divided into five groups (n = 12/group): (A) control group; (B) rHDGF ab only group [normal animals treated with 50 µM recombinant HDGF antibodies (rHDGF ab)]; (C) SAH group; (D) SAH + pre-rHDGF ab group (SAH animals pre-treated with 50 µM rHDGF ab into the subarachnoid space within 24 h before SAH); and (E) SAH + post-rHDGF ab group (SAH animals post-treated with 50 µM rHDGF ab into the subarachnoid space within 24 h after SAH). At 48 h after SAH, serum and cerebrospinal fluid (CSF) samples were collected to measure the levels of pro-inflammatory factors by ELISA, and rat cortex tissues were used to measure protein levels by western blot analysis. Immunofluorescence staining for Iba-1, GFAP, TUNEL, and NeuN was detected proliferation of microglia and astrocyte and apoptosis of neuron cells. Neurological outcome was assessed by ambulation and placing/stepping reflex responses. Morphology assay showed that pre-treatment and post-treatment with rHDGF ab attenuated vasospasm after SAH. SAH up-regulated the levels of TNF-α, IL-1β, and IL-6 in both the CSF and serum samples, and both pre- and post-treatment with rHDGF ab inhibited the up-regulation of these pro-inflammatory factors, except for the serum IL-6 levels. Western blot analysis demonstrated that SAH up-regulated pro-BDNF and NFκB protein levels, and both pre- and post-treatment with rHDGF ab significantly reduced the up-regulation. The result from immunofluorescence staining showed that SAH induced proliferation of microglia and astrocyte and apoptosis of neuron cells. Both pre- and post-treatment with rHDGF ab significantly attenuated proliferation of microglia and astrocyte and inhibited apoptosis of neuron cells. Furthermore, treatment with rHDGF ab significantly improved neurological outcome. Blocking HDGF attenuates neuron cell apoptosis and vasospasm through inhibiting inflammation in brain tissue at early phase after SAH.

Impact of Hepatoma-Derived Growth Factor Blockade on Resiniferatoxin-Induced Neuropathy

Resiniferatoxin is an ultrapotent capsaicin analog that mediates nociceptive processing; treatment with resiniferatoxin can cause an inflammatory response and, ultimately, neuropathic pain. Hepatoma-derived growth factor, a growth factor related to normal development, is associated with neurotransmitters surrounding neurons and glial cells. Therefore, the study aims to investigate how blocking hepatoma-derived growth factor affects the inflammatory response in neuropathic pain. Serum hepatoma-derived growth factor protein expression was measured via ELISA. Resiniferatoxin was administrated intraperitoneally to induce neuropathic pain in 36 male Sprague-Dawley rats which were divided into three groups (resiniferatoxin+recombinant hepatoma-derived growth factor antibody group, resiniferatoxin group, and control group) (n = 12/group). The mechanical threshold response was tested with calibration forceps. Cell apoptosis was measured by TUNEL assay. Immunofluorescence staining was performed to detect apoptosis of neuron cells and proliferation of astrocytes in the spinal cord dorsal horn. RT-PCR technique and western blot were used to measure detect inflammatory factors and protein expressions. Serum hepatoma-derived growth factor protein expression was higher in the patients with sciatica compared to controls. In resiniferatoxin-group rats, protein expression of hepatoma-derived growth factor was higher than controls. Blocking hepatoma-derived growth factor improved the mechanical threshold response in rats. In dorsal root ganglion, blocking hepatoma-derived growth factor inhibited inflammatory cytokines. In the spinal cord dorsal horn, blocking hepatoma-derived growth factor inhibited proliferation of astrocyte, apoptosis of neuron cells, and attenuated expressions of pain-associated proteins. The experiment showed that blocking hepatoma-derived growth factor can prevent neuropathic pain and may be a useful alternative to conventional analgesics.

Hepatoma-Derived Growth Factor Secreted from Mesenchymal Stem Cells Reduces Myocardial Ischemia-Reperfusion Injury

Objectives

The present study aimed to explore the major factors that account for the beneficial effects of mesenchymal stem cells (MSCs).

Methods

Using isobaric tags for relative and absolute quantitation method, hepatoma-derived growth factor (HDGF) was identified as an important factor secreted by MSCs, but not by cardiac fibroblasts (CFs). The protective effects of conditioned medium (CdM) from MSCs or CFs were tested by using either H9C2 cells that were exposed by hypoxia-reoxygenation (H/R) insult or an in vivo mouse model of myocardial ischemia-reperfusion.

Results

Compared to CF-CdM, MSC-CdM conferred protection against reperfusion injury. CdM obtained from MSCs that were treated with HDGF-targeted shRNA failed to offer any protection in vitro. In addition, administration of recombinant HDGF alone recapitulated the beneficial effects of MSC-CdM, which was associated with increased protein kinase C epsilon (PKCε) phosphorylation, enhanced mitochondria aldehyde dehydrogenase family 2 activity, and decreased 4-hydroxy-2-nonenal accumulation. A significant decrease in infarct size and ameliorated cardiac dysfunction was achieved by administration of HDGF in wild-type mice, which was absent in PKCε dominant negative mice, indicating the essential roles of PKCε in HDGF-mediated protection.

Conclusions

HDGF secreted from MSCs plays a key role in the protection against reperfusion injury through PKCε activation.

The evaluation of hepatoma-derived growth factor in determining of prognosis and estimating of invasive probability of tumoral cells, recurrent, and metastasis of lymphatic glands in breast carcinoma

Introduction:

Recently, hepatoma-derived growth factor (HDGF) has been considered as a significantly important factor in determining the prognosis and estimating the probability of tumor cell invasions, recurrence, and lymph node metastasis in different cancers, including breast malignancies.

Materials and Methods:

Immunohistochemistry (IHC) study for HDGF was performed on paraffin-embedded blocks of patients with breast carcinoma in Modarres hospital, Tehran, Iran, since 1387–1390 (74 cases); three separate pathologists read the slides after complete IHC staining. Thereafter, necessary information was recorded from patient files, and eventually, findings were analyzed by SPSS program.

Results:

Expression of nuclear HDGF has significant statistical correlation with tumor grade according to Nottingham grading scheme; this correlation is also seen with nuclear pleomorphism of tumor cells and mitotic count. No correlation between age and tumor size with expression of HDGF is found. Lymph node metastasis is in inverse ratio to nuclear HDGF staining.

Conclusion:

Nuclear expression of HDGF in tumor cells is increased concordantly to tumor grade, which implies us to the role of this marker in determining the prognosis and choosing the most suitable treatment plan.

Two new isoforms of the human hepatoma-derived growth factor interact with components of the cytoskeleton

Hepatoma-derived growth factor (HDGF) is involved in diverse, apparently unrelated processes, such as cell proliferation, apoptosis, DNA-repair, transcriptional control, ribosome biogenesis and cell migration. Most of the interactions of HDGF with diverse molecules has been assigned to the hath region of HDGF. In this study we describe two previously unknown HDGF isoforms, HDGF-B and HDGF-C, generated via alternative splicing with structurally unrelated N-terminal regions of their hath region, which is clearly different from the well described isoform, HDGF-A. In silico modeling revealed striking differences near the PHWP motif, an essential part of the binding site for glycosaminoglycans and DNA/RNA. This observation prompted the hypothesis that these isoforms would have distinct interaction patterns with correspondingly diverse roles on cellular processes. Indeed, we discovered specific associations of HDGF-B and HDGF-C with cytoskeleton elements, such as tubulin and dynein, suggesting previously unknown functions of HDGF in retrograde transport, site directed localization and/or cytoskeleton organization. In contrast, the main isoform HDGF-A does not interact directly with the cytoskeleton, but via RNA with messenger ribonucleoprotein (mRNP) complexes. In summary, the discovery of HDGF splice variants with their discrete binding activities and subcellular distributions opened new avenues for understanding its biological function and importance.

Hepatoma-derived growth factor: A survival-related protein in prostate oncogenesis and a potential target for vitamin K2

Hepatoma-derived growth factor (HDGF) is a heparin-binding growth factor, which has previously been shown to be expressed in a variety of cancers. HDGF overexpression has also previously been correlated with a poor prognosis in several cancers. The significance of HDGF in prostate cancer, however, has not been investigated. Here, we show that HDGF is overexpressed in both androgen-sensitive LNCaP cells and androgen-insensitive DU145, 22RV1, and PC-3 cells. Forced overexpression enhanced cell viability of RWPE-1 cells, whereas HDGF knockdown reduced cell proliferation in human prostate cancer cells. We also show that HDGF may serve as a survival-related protein as ectopic overexpression of HDGF in RWPE cells up-regulated the expression of antiapoptosis proteins cyclin E and BCL-2, whereas simultaneously down-regulating proapoptotic protein BAX. Western blot analysis also showed that HDGF overexpression modulated the activity of phospho-AKT as well as NF-kB, and these results correlated with in vitro migration and invasion assays. We next assessed the therapeutic potential of HDGF inhibition with a HDGF monoclonal antibody and vitamin k₂, showing reduced cell proliferation as well as inhibition of NF-kB expression in HDGF overexpressed RWPE cells treated with a HDGF monoclonal antibody and vitamin K₂. Collectively, our results suggest that HDGF is a relevant protein in prostate oncogenesis and may serve as a potential therapeutic target in prostate cancer.

Genetic variations in apoptosis pathway and the risk of ovarian cancer

BACKGROUND

Apoptosis is a highly conserved form of cell death and aberrant regulation of apoptotic cell death mechanisms leads to variety of major human diseases, especially tumor formation. Genetic variations in apoptosis genes may increase susceptibility to ovarian cancer.

RESULTS

In individual SNP analysis, 12 SNPs in 5 apoptosis pathway genes were significantly associated with ovarian cancer risk after adjustment for multiple comparisons at q-value <0.05. The most significant SNP was rs11152377 in the Bcl-2 gene. The homozygous variant TT genotype was associated with a significantly decreased risk of ovarian cancer (odds ratio [OR] =0.53; 95% confidence interval [CI], 0.37-0.77, P<0.001). Cumulative effect analysis showed joint effects of increased risk of ovarian cancer with increasing number of unfavorable genotypes in patients. Classification and regression tree (CART) analysis further revealed high-order gene-gene interactions and categorized the study subjects into low-, medium-, and high-risk groups. Compared with the low-risk group, medium-risk group and high-risk group conferred 1.76-fold (95% CI: 1.06-2.90) and 3.64-fold (95% CI: 2.37-5.59) increased risk of ovarian cancer (P for trend <0.001)Materials and Methods: In a case-control study of 417 ovarian cancer patients and 417 matched controls, we evaluated the associations of 587 single nucleotide polymorphisms (SNPs) from 65 genes of the apoptosis pathway with the risk of ovarian cancer.

CONCLUSIONS

Our results suggest that genetic variations in apoptosis pathway genes modulate the risk of ovarian cancer individually and jointly.

HDGF: a novel jack-of-all-trades in cancer

HDGF is an important regulator of a broad range of cancer cell activities and plays important roles in cancer cell transformation, apoptosis, angiogenesis and metastasis. Such a divergent influence of HDGF on cancer cell activities derives from its multiple inter- and sub-cellular localizations where it interacts with a range of different binding partners. Interestingly, high levels of HDGF could be detected in patients' serum of some cancers. This review is focused on the role of HDGF in tumorigenesis and metastasis, and provides insight for application in clinical cancer therapy as well as its clinical implications as a prognostic marker in cancer progression.

Integrating proteomics with electrochemistry for identifying kinase biomarkers

We present an integrated approach for highly sensitive identification and validation of substrate-specific kinases as cancer biomarkers. Our approach combines phosphoproteomics for high throughput cancer-related biomarker discovery from patient tissues and an impedimetric kinase activity biosensor for sensitive validation. Using non-small-cell lung cancer (NSCLC) as a proof-of-concept study, label-free quantitative phosphoproteomic analysis of a pair of cancerous and its adjacent normal tissues revealed 198 phosphoproteins that are over-phosphorylated in NSCLC. Among the differentially regulated phosphorylation sites, the most significant alteration was in residue S165 in the Hepatoma Derived Growth Factor (HDGF) protein. Hence, HDGF was selected as a model system for the electrochemical studies. Further motif-based analysis of this altered phosphorylation site revealed that extracellular-signal-regulated kinase 1/2 (ERK1/2) are most likely to be the corresponding kinases. For validation of the kinase-substrate pair, densely packed peptide monolayers corresponding to the HDGF phosphorylation site were coupled to a gold electrode. Phosphorylation of the monolayer by ERK2 and dephosphorylation by alkaline phosphatase (AP) were detected by electrochemical impedance spectroscopy (EIS) and surface roughness analysis. Compared to other methods for quantification of kinase concentration, this label-free electrochemical assay offers the advantages of ultra-sensitivity as well as higher specificity for the detection of cancer-related kinase-substrate pair. With implementation of multiple kinase-substrate biomarker pairs, we expect this integrated approach to become a high throughput platform for discovery and validation of phosphorylation-mediated biomarkers.

Hepatoma-Derived Growth Factor: Its Possible Involvement in the Progression of Hepatocellular Carcinoma

The development of hepatocellular carcinoma (HCC) is an important complication of viral infection induced by hepatitis virus C, and our major research theme is to identify a new growth factor related to the progression of HCC. HDGF (hepatoma-derived growth factor) is a novel growth factor that belongs to a new gene family. HDGF was initially purified from the conditioned medium of a hepatoma cell line. HDGF promotes cellular proliferation as a DNA binding nuclear factor and a secreted protein acting via a receptor-mediated pathway. HDGF is a unique multi-functional protein that can function as a growth factor, angiogenic factor and anti-apoptotic factor and it participates in the development and progression of various malignant diseases. The expression level of HDGF may be an independent prognostic factor for predicting the disease-free and overall survival in patients with various malignancies, including HCC. Furthermore, the overexpression of HDGF promotes the proliferation of HCC cells, while a reduction in the HDGF expression inhibits the proliferation of HCC cells. This article provides an overview of the characteristics of HDGF and describes the potential role of HDGF as a growth-promoting factor for HCC.

Downregulation of the expression of HDGF attenuates malignant biological behaviors of hilar cholangiocarcinoma cells

Hepatoma-derived growth factor (HDGF) has been reported to be a potential predictive and prognostic marker for several types of cancer and important in malignant biological behaviors. However, its role in human hilar cholangiocarcinoma remains to be elucidated. Our previous study demonstrated that high expression levels of HDGF in hilar cholangiocarcinoma tissues correlates with tumor progression and patient outcome. The present study aimed to elucidate the detailed functions of the HDGF protein. This was performed by downregulating the protein expression of HDGF in the FRH0201 hilar cholangiocarcinoma cell line by RNA interference (RNAi) in vitro, and revealed that downregulation of the HDGF protein significantly inhibited the malignant biological behavior of the FRH0201 cells. In addition, further investigation revealed that downregulation of the protein expression of HDGF significantly decreased the secretion of vascular endothelial growth factor, which may be the mechanism partially responsible for the inhibition of malignant biological behaviors. These findings demonstrated that HDGF is important in promoting malignant biological behaviors, including proliferation, migration and invasion of hilar cholangiocarcinoma FRH0201 cells. Inhibition of the expression of HDGF downregulated the malignant biological behaviors, suggesting that downregulation of the protein expression of HDGF by RNAi may be a novel therapeutic approach to inhibit the progression of hilar cholangiocarcinoma.

Brain derived neurotrophic factor contributes to the cardiogenic potential of adult resident progenitor cells in failing murine heart

Aims

Resident cardiac progenitor cells show homing properties when injected into the injured but not to the healthy myocardium. The molecular background behind this difference in behavior needs to be studied to elucidate how adult progenitor cells can restore cardiac function of the damaged myocardium. Since the brain derived neurotrophic factor (BDNF) moderates cardioprotection in injured hearts, we focused on delineating its regulatory role in the damaged myocardium.

Methods and Results

Comparative gene expression profiling of freshly isolated undifferentiated Sca-1 progenitor cells derived either from heart failure transgenic αMHC-CyclinT1/Gαq overexpressing mice or wildtype littermates revealed transcriptional variations. Bdnf expression was up regulated 5-fold during heart failure which was verified by qRT-PCR and confirmed at protein level. The migratory capacity of Sca-1 cells from transgenic hearts was improved by 15% in the presence of 25ng/ml BDNF. Furthermore, BDNF-mediated effects on Sca-1 cells were studied via pulsed Stable Isotope Labeling of Amino acids in Cell Culture (pSILAC) proteomics approach. After BDNF treatment significant differences between newly synthesized proteins in Sca-1 cells from control and transgenic hearts were observed for CDK1, SRRT, HDGF, and MAP2K3 which are known to regulate cell cycle, survival and differentiation. Moreover BDNF repressed the proliferation of Sca-1 cells from transgenic hearts.

Conclusion

Comparative profiling of resident Sca-1 cells revealed elevated BDNF levels in the failing heart. Exogenous BDNF (i) stimulated migration, which might improve the homing ability of Sca-1 cells derived from the failing heart and (ii) repressed the cell cycle progression suggesting its potency to ameliorate heart failure.

Proteomic Changes Induced by Podophyllotoxin in Human Cervical Carcinoma HeLa Cells

Podophyllotoxin, a kind of lignan extracted from the Podophyllum plant, has been shown to inhibit the growth of various carcinoma cells. However, the molecular mechanism remains unclear. In this study, the inhibition of cell growth and changes in protein expression induced by podophyllotoxin were investigated in human cervical carcinoma HeLa cells. Our results demonstrate that Podophyllotoxin inhibits HeLa cell growth and induces apoptosis. By using proteomic techniques, seven proteins were found to be significantly regulated by podophyllotoxin compared to the untreated control; among them, four were down-regulated and three were up-regulated. All of the seven proteins were identified with peptide mass fingerprinting using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) after in-gel trypsin digestion. Five of these proteins are involved in protein metabolism, and the other two play roles in cell communication and signaling transduction pathways. It is suggested that the effect of podophyllotoxin on the growth of tumor cells is significantly related to the metabolism-associated proteins.

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.

Identifying new therapeutic targets via modulation of protein corona formation by engineered nanoparticles

BACKGROUND

We introduce a promising methodology to identify new therapeutic targets in cancer. Proteins bind to nanoparticles to form a protein corona. We modulate this corona by using surface-engineered nanoparticles, and identify protein composition to provide insight into disease development.

METHODS/PRINCIPAL FINDINGS

Using a family of structurally homologous nanoparticles we have investigated the changes in the protein corona around surface-functionalized gold nanoparticles (AuNPs) from normal and malignant ovarian cell lysates. Proteomics analysis using mass spectrometry identified hepatoma-derived growth factor (HDGF) that is found exclusively on positively charged AuNPs ((+)AuNPs) after incubation with the lysates. We confirmed expression of HDGF in various ovarian cancer cells and validated binding selectivity to (+)AuNPs by Western blot analysis. Silencing of HDGF by siRNA resulted s inhibition in proliferation of ovarian cancer cells.

CONCLUSION

We investigated the modulation of protein corona around surface-functionalized gold nanoparticles as a promising approach to identify new therapeutic targets. The potential of our method for identifying therapeutic targets was demonstrated through silencing of HDGF by siRNA, which inhibited proliferation of ovarian cancer cells. This integrated proteomics, bioinformatics, and nanotechnology strategy demonstrates that protein corona identification can be used to discover novel therapeutic targets in cancer.

Quantitative phosphoproteomics of transforming growth factor-β signaling in colon cancer cells

The transforming growth factor-β (TGF-β) signaling pathway progresses through a series of protein phosphorylation regulated steps. Smad4 is a key mediator of the classical TGF-β signaling pathway; however, reports suggest that TGF-β can activate other cellular pathways independent of Smad4. By investigating the TGF-β-regulated phosphoproteome, we aimed to uncover new functions controlled by TGF-β. We applied titanium dioxide to enrich phosphopeptides from stable isotope labeling with amino acids in cell culture (SILAC)-labeled SW480 cells stably expressing Smad4 and profiled them by mass spectrometry. TGF-β stimulation for 30 min resulted in the induction of 17 phosphopeptides and the repression of 8 from a total of 149 unique phosphopeptides. Proteins previously not known to be phosphorylated by TGF-β including programmed cell death protein 4, nuclear ubiquitous casein and cyclin-dependent kinases substrate, hepatoma-derived growth factor and cell division kinases amongst others were induced following TGF-β stimulation, while the phosphorylation of TRAF2 and NCK-interacting protein kinase are examples of proteins whose phosphorylation status was repressed. This phosphoproteomic screen has identified new TGF-β-modulated phosphorylation responses in colon carcinoma cells.

Tumorigenesis and prognostic role of hepatoma-derived growth factor in human gliomas

Hepatoma-derived growth factor (HDGF) is a neurotrophic factor found in mouse spinal cord and hippocampal neurons. In various malignant tumors, the role of HDGF in tumor progression and its use as a diagnostic biomarker or therapeutic target have been extensively explored. However, the prognostic function and mitogenic role of HDGF in gliomagenesis are yet to be verified. In this study, we found a significant incidence of HDGF prevalence between the different pathological types and stages of glioma in 105 patients. We also found a prognostic significance in 41 glioblastoma multiforme (GBM) patients, with prevalence of nuclear HDGF predicting short survival of patients with GBM after surgery. To delineate the mitogenic role of HDGF in gliomagenesis, an adenoviral-expressed HDGF small interfering RNA (Ad-HDGF siRNA) was used to knock down expression of nuclear HDGF. After knocking down nuclear HDGF expression in human GBM cells, cell growth and cell invasion and induction on apoptosis by caspase-3 activation were significantly inhibited. We conclude that HDGF is a mitogenic growth factor in glioma progression and can be a useful prognostic marker for GBM and therapeutic target for clinical management of glioma in the 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.

CD44v6 coordinates tumor matrix-triggered motility and apoptosis resistance

Tumor progression requires a crosstalk with the tumor surrounding, where the tumor matrix plays an essential role. We recently reported that only the matrix delivered by a CD44v6-competent (ASML(wt)), but not that of a CD44v6-deficient (ASML-CD44v(kd)) rat pancreatic adenocarcinoma line supports metastasis formation. We here describe that this matrix provides an important feedback toward the tumor cell and that CD44v6 accounts for orchestrating signals received from the matrix. ASML(wt) cells contain more hyaluronan synthase-3 and secrete higher amounts of >50 kDa HA than ASML-CD44v(kd) cells, which secrete more hyaluronidase. Only the ASML(wt)-matrix supports migration and apoptosis resistance, which both can be initiated via CD44v6, c-Met, and α6β4 ligand binding and proceed via FAK, PI3K/Akt, and MAPK activation, respectively. However, c-Met- and α6β4-initiated signaling are strongly augmented by the association with CD44v6 as only very weak effects are observed in CD44v6-deficient cells. The same CD44v6-dependent convergence of motility- and apoptosis resistance-related signals also accounts for human tumor lines. Thus, CD44v6 promotes motility and apoptosis resistance via its involvement in assembling a matrix that, in turn, triggers activation of signaling cascades, which proceeds, independent of the initiating receptor-ligand interaction, in a concerted action via CD44v6.

Increased expression of hepatoma-derived growth factor correlates with poor prognosis in human nasopharyngeal carcinoma

AIMS

To examine the correlation between hepatoma-derived growth factor (HDGF) expression and clinicopathological data in nasopharyngeal carcinoma (NPC), including patient survival.

METHODS AND RESULTS

Using real-time polymerase chain reaction (PCR) and Western blot, mRNA and protein expression of HDGF was detected in normal nasopharyngeal tissues, NPC tissues and cell lines. HDGF levels were determined further by an immunohistochemical analysis in a retrospective series consisting of 160 primary NPC tissues and 71 non-cancerous nasopharynx tissues. Overexpressed mRNA and HDGF protein was present in NPC. By immunohistochemical analysis, we found that 53.8% (86 of 160) and 19.4% (32 of 160) of NPC biopsy specimens showed higher HDGF expression of the nucleus and cytoplasm, respectively. Statistical analysis showed that the higher expression of nuclear HDGF was associated significantly with T stage (P=0.005) and clinical stage (P=0.038), but there was no association with lymph node (P=0.059) or distant metastasis (P=0.563). Patients with increased HDGF expression levels had poorer overall survival rates than those with low expression of HDGF levels (P=0.006). Multivariate analysis revealed that high expression of nuclear HDGF was an independent prognostic indicator of patient survival.

CONCLUSIONS

Increased nuclear expression of HDGF is a potential unfavourable prognostic factor for patients with NPC.

Secretion of hepatoma-derived growth factor is regulated by N-terminal processing

Hepatoma-derived growth factor (HDGF) was first purified as a growth factor secreted by hepatoma cells. It promotes angiogenesis and has been related to tumorigenesis. To date, little is known about the molecular mechanisms of HDGF functions and especially its routes or regulation of secretion. Here we show that secretion of HDGF requires the N-terminal 10 amino acids and that this peptide can mediate secretion of other proteins, such as enhanced green fluorescent protein, if fused to their N-terminus. Our results further demonstrate that cysteine residues at positions 12 and 108 are linked via an intramolecular disulfide bridge. Surprisingly, phosphorylation of serine 165 in the C-terminal part of HDGF plays a critical role in the secretion process. If this serine is replaced by alanine, the N-terminus is truncated, the intramolecular disulfide bridge is not formed and the protein is not secreted. In summary, these observations provide a model of how phosphorylation, a disulfide bridge and proteolytic cleavage are involved in HDGF secretion.

Significance of HDGF expression in hepatocellular carcinoma tissue and HepG2 cells

AIM: To investigate the expression of hepatoma-derived growth factor (HDGF) in hepatocellular carcinoma (HCC) tissue and HepG2 cells and to analyze its significance.

METHODS: Ten HCC tissue samples and matched noncancerous tissue samples were collected. The mRNA expression of HDGF in these HCC samples, noncancerous tissue samples and HepG2 cells was detected by real-time RT-PCR. The protein expression of HDGF in 137 HCC tissue samples and 49 normal liver tissue samples was examined by immunohistochemistry. The relationship between HDGF expression and clinicopathological parameters in HCC was then analyzed.

RESULTS: The expression levels of HDGF mRNA were 21.11 and 11.39 times higher in HCC tissue and HepG2 cells than in noncancerous tissue, respectively. The positive rate of HDGF expression in HCC tissue was significantly higher than that in normal liver tissue (77.4% vs 51.5%, P = 0.011). High expression of HDGF protein was positively correlated with T classification, N classification and clinical stage (all P < 0.05) in HCC patients. Univariate Cox analysis showed that HDGF expression, N classification and clinical stage had significant correlation with survival prognosis of HCC patients (P = 0.028, 0.041 and 0.000; HR = 1.557, 1.526 and 2.316, respectively). Multivariate analysis showed that HDGF expression might be an independent prognostic indicator (P = 0.000, HR = 0.358) for the development and progression of HCC. Patients with higher HDGF expression showed a significantly shorter overall survival time than those with low HDGF expression.

CONCLUSION: HDGF is highly expressed in HCC tissue and HepG2 cells. High HDGF expression is an independent prognostic factor in HCC patients. High HDGF expression is associated with poor overall survival in patients with HCC.

shRNA targeting HDGF suppressed cell growth and invasion of squamous cell lung cancer

Hepatoma-derived growth factor (HDGF), a nuclear protein with both mitogenic and angiogenic activity, has been reported to be mainly involved in tumorigenesis and the progression of non-small cell lung cancer. In this study, the HDGF expression was knocked down by specific-shRNA with lentivirus expression vector targeting HDGF in lung squamous cell carcinoma 520 cells. HDGF knocked down by shRNA suppressed the cell proliferation significantly both in vitro and in vivo as indicated by MTT, plate clone and transplanted tumor model assays. In addition, the knocked-down expression of HDGF also inhibited cell migration and invasion as shown in transwell and Boyden experiments. We concluded that HDGF acts as an oncogene participating in the pathogenesis of squamous cell lung cancer, and HDGF may be a key therapeutic target for non-small cell lung cancer.

Apoptosis of human colorectal carcinoma cells is induced by blocking hepatoma-derived growth factor

Hepatoma-derived growth factor (HDGF) is a novel multifunctional growth factor that elicits pleiotropic effects on biological processes such as lung remodeling and renal development. Recent studies demonstrated that HDGF is related to tumor proliferation, invasion, angiogenesis, and apoptosis. However, the molecular mechanism of HDGF's involvement in apoptosis remains to be clarified. In this study, we first analyze the role of HDGF in colorectal carcinoma (CRC) progression by immunohistochemistry. Then we used small interference RNA (HDGF-siRNA) to block HDGF and assessed its effect on inducing apoptosis of CRC loVo cells. Apoptosis was detected using flow cytometry (FCM), DNA ladder analysis, and Hoechst 33258 staining. In addition, the expression levels of some apoptosis-related proteins were examined by western blot. The result showed that HDGF expression gradually increased in the colorectal carcinogenesis process. Further studies demonstrated that knock-down of HDGF can down-regulate the survivin, activate the mitochondrial pathway, and induce apoptosis in loVo cells. These findings suggest that HDGF is involved in colorectal carcinogenesis process. Further blocking HDGF exhibits potent pro-apoptotic properties in colon cancer cells. Thus, HDGF might be a potential therapeutic target for human colorectal cancer. These findings may have major implications in the treatment of colorectal cancer.

Hepatoma-derived growth factor and its role in keloid pathogenesis

Hepatoma-derived growth factor (HDGF) is a novel mitogenic growth factor that has been implicated in many different carcinomas. Its role in keloid biology has not yet been investigated. The present study is aimed at examining the role of HDGF in keloid pathogenesis. Immunohistochemical staining and Western blot analyses were used to examine in vivo localization and expression of HDGF in keloid and normal skin tissue. This was followed by the detection of HDGF expression in fibroblasts cultured in vitro and fibroblasts exposed to serum. To investigate the effect of epithelial–mesenchymal interactions, a two-chamber system was employed in which keratinocytes on membrane inserts were co-cultured with the fibroblasts. HDGF expression levels in all cell extracts and conditioned media were assayed through Western blot analysis. In another set of experiments, the effect of exogenous recombinant HDGF on keloid fibroblasts (KF) and normal fibroblasts (NF) was examined. Cell proliferation was assessed by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and by quantifying proliferating cell nuclear antigen (PCNA) expression. Downstream targets of HDGF were identified by detecting their expression through Western blot analysis. Our results indicate that there was an increase in HDGF expression in the dermis of keloid compared with normal skin tissue. The application of serum and epithelial–mesenchymal interactions did not seem to have any effect on intracellular HDGF expression levels. However, co-culturing keloid keratinocytes with KFs resulted in increased HDGF secretion when compared with monoculture or normal controls. Furthermore, treatment with exogenous recombinant HDGF was found to increase the proliferation of KFs, activate the extracellular signal-regulated kinase (ERK) pathway and up-regulate the secretion of vascular endothelial growth factor (VEGF).