Hepatocyte growth factor/scatter factor blocks the mitochondrial pathway of apoptosis signaling in breast cancer cells

Potential mechanisms underlying the effect of hepatocyte growth factor on liver injury in short bowel syndrome model rats

PURPOSE

The purpose of this study was to investigate the autophagy associated with apoptosis in hepatic damage in the short bowel syndrome rat model.

METHODS

SD rats underwent jugular vein catheterization for continuous total parenteral nutrition (TPN) and 90% small bowel resection. Animals were divided into two groups: TPN plus SBS (Control group) or TPN plus SBS plus intravenous administration of HGF (HGF group). On day 7, the rats were harvested, and hepatocellular injury was evaluated.

RESULTS

In an SBS rat model, hepatic steatosis and lobular inflammation were histologically suppressed in the HGF group (p < 0.01). The expression of tumor necrosis factor-α in the HGF group tend to be higher than that in the control group (p = 0.13). The gene expression of transforming Growth Factor-β in the HGF group was suppressed compared to the control group (p < 0.01). HGF treatment may have an antiapoptotic effect via the intrinsic pathway by caspase 9. Protein expressions of Rubicon (p = 0.03) and p62 (p < 0.01) in the HGF group were found to have increased compared to those in the control group.

CONCLUSION

The inhibitory effect of HGF on hepatic steatosis remains unclear, and further studies focusing on the mechanisms of fat accumulation are needed.

Inhibition of c-MET increases the antitumour activity of PARP inhibitors in gastric cancer models

Gastric cancer is the fifth most common malignancy and the third leading cause of cancer‐related death worldwide. Activation of c‐MET increases tumour cell survival through the initiation of the DNA damage repair pathway. PARP is an essential key in the DNA damage repair pathway. The primary role of PARP is to detect and initiate an immediate cellular response to single‐strand DNA breaks. Tumours suppressor genes such as BRCA1/2 are closely associated with the DNA repair pathway. In BRCA1/2 mutations or deficiency status, cells are more likely to develop additional genetic alterations and chromosomal instability and can lead to cancer. In this study, we investigate the role of c‐MET and PARP inhibition in a gastric cancer model. We exploited functional in vitro and in vivo experiments to assess the antitumour potential of co‐inhibition of c‐MET (SU11274) and PARP (NU1025). This leads to a reduction of gastric cancer cells viability, especially after knockdown of BRCA1/2 through apoptosis and induction of γ‐Η2ΑΧ. Moreover, in AGS xenograft models, the combinatorial treatment of NU1025 plus SU11274 reduced tumour growth and triggers apoptosis. Collectively, our data may represent a new therapeutic approach for GC thought co‐inhibition of c‐MET and PARP, especially for patients with BRCA1/2 deficiency tumours.

Doxorubicin and CD‑CUR inclusion complex co‑loaded in thermosensitive hydrogel PLGA‑PEG‑PLGA localized administration for osteosarcoma

Combination therapy is a promising and prevalent strategy for osteosarcoma treatment. Curcumin (CUR), as a chemosensitizer, improves the antitumor effect of first‑line chemotherapy drugs. However, due to its poor solubility and instability in physiological conditions, the bioavailability of CUR is limited. In order to improve the physicochemical properties of natural CUR, β‑cyclodextrin was adopted to generate a β‑cyclodextrin curcumin (CD‑CUR) inclusion complex. A thermosensitive hydrogel, poly(D,L‑lactide‑co‑glycolide)-poly(ethylene‑glycol)‑poly(D,L‑lactide‑co‑glycolide), was selected and synthesized to co‑deliver doxorubicin (DOX) and CD‑CUR to tumor sites. The dual‑drug delivery system (gel+DOX+CD‑CUR) was prepared by mixing drugs with hydrogels and had a perfect sol‑gel phase transition temperature (18.3˚C for 20% concentration). Both DOX and CUR were released from hydrogels in a sustained manner in PBS (pH 7.4) medium. The combination therapy based on DOX+CD‑CUR exhibited higher antitumor activity than monotherapies in vitro. Combined CD‑CUR therapy significantly downregulated Bcl‑2 expression and upregulated caspase‑3 expression, suggesting that DOX combined with CD‑CUR treatment has a higher apoptosis‑inducing efficiency. The antitumor efficiency of the gel+DOX+CD‑CUR strategy was evaluated in K‑7 tumor‑bearing mice, and this localized combination therapy demonstrated a higher antitumor efficiency compared with free DOX+CD‑CUR or single‑drug strategies. There were no significant differences in body weight and histological changes of major organs in each group. Therefore, the present combination treatment based on hydrogel may be a feasible approach to co‑deliver DOX and CD‑CUR to osteosarcoma tumor sites in clinical practice.

The hepatocyte growth factor isoform NK2 activates motogenesis and survival but not proliferation due to lack of Akt activation

Hepatocyte growth factor (HGF) is a pleiotrophic factor involved in cellular proliferation, migration and morphogenesis. HGF is required for normal tissue and organ development during embryogenesis, but in the adult HGF has been demonstrated to drive normal tissue repair and inhibit fibrotic remodeling. HGF has two naturally occurring human isoforms as a result of alternative splicing, NK1 and NK2. While NK1 has been defined as an agonist for HGF receptor, Met, NK2 is defined as a partial Met antagonist. Furthermore, under conditions of fibrotic remodeling, NK2 is still expressed while full length HGF is suppressed. Furthermore, the mechanism by which NK2 partially signals through Met is not completely understood. Here, we investigated the mitogenic, motogenic, and anti-apoptotic activities of NK2 compared with full length HGF in primary human bronchial epithelial cells (BEpC) and bovine pulmonary artery endothelial cells (PAEC). In human BEpC, NK2 partial activated Met, inducing Met phosphorylation at Y1234/1235 in the tyrosine-kinase domain but not at Y1349 site in the multifunctional docking domain. Partial phosphorylation of Met by NK2 resulted in activation of MAPK and STAT3, but not AKT. This correlated with motogenesis and survival in a MAPK-dependent manner, but not cell proliferation. Overexpression of a constitutively active AKT complemented NK2 signaling, allowing NK2 to induce cell proliferation. These data indicate that NK2 and HGF drive motogenic and anti-apoptotic signaling but only HGF drives cell proliferation by activating AKT-pathway signaling. These results have implications for the biological consequences of differential regulation of the two isoforms under pro-fibrotic conditions.

The clinical and functional significance of c-Met in breast cancer: a review

c-Met is a receptor tyrosine kinase that upon binding of its ligand, hepatocyte growth factor (HGF), activates downstream pathways with diverse cellular functions that are important in organ development and cancer progression. Anomalous c-Met signalling has been described in a variety of cancer types, and the receptor is regarded as a novel therapeutic target. In breast cancer there is a need to develop new treatments, particularly for the aggressive subtypes such as triple-negative and basal-like cancer, which currently lack targeted therapy. Over the last two decades, much has been learnt about the functional role of c-Met signalling in different models of breast development and cancer. This work has been complemented by clinical studies, establishing the prognostic significance of c-Met in tissue samples of breast cancer. While the clinical trials of anti-c-Met therapy in advanced breast cancer progress, there is a need to review the existing evidence so that the potential of these treatments can be better appreciated. The aim of this article is to examine the role of HGF/c-Met signalling in in vitro and in vivo models of breast cancer, to describe the mechanisms of aberrant c-Met signalling in human tissues, and to give a brief overview of the anti-c-Met therapies currently being evaluated in breast cancer patients. We will show that the HGF/c-Met pathway is associated with breast cancer progression and suggest that there is a firm basis for continued development of anti-c-Met treatment, particularly for patients with basal-like and triple-negative breast cancer.

Hsp70 promotes chemoresistance by blocking Bax mitochondrial translocation in ovarian cancer cells

Cisplatin can induce apoptosis in ovarian cancer cells through the mitochondrial death pathway, and dysregulation of this pathway contributes to cisplatin resistance in ovarian cancer cells. Here we show that cisplatin induces mitochondrial proteins such as Smac/DIABLO, Cytochrome c, and HrtA2/Omi release to the cytosol and apoptosis in cisplatin-sensitive, but not -resistant ovarian cancer cells. Bax translocation to mitochondria is required for mitochondrial protein release and cisplatin-induced apoptosis in human ovarian cancer cells. Hsp70 is highly expressed in cisplatin-resistant cells. Hsp70 promotes chemoresistance, in part, by blocking Bax translocation to the mitochondria and mitochondrial protein release to cytosol in human ovarian cancer cells.

Coformulation of doxorubicin and curcumin in poly(D,L-lactide-co-glycolide) nanoparticles suppresses the development of multidrug resistance in K562 cells

Doxorubicin (DOX) is a broad-spectrum anthracycline antibiotic used to treat a variety of cancers including leukemia. Chronic myeloid leukemia (CML) blasts like K562 cells are resistant to apoptosis induced by DOX due to several reasons, the primary being the sequestration of drug into cytoplasmic vesicles and induction of multidrug resistance (MDR) gene expression with DOX treatment resulting in intracellular resistance to this drug. Moreover, expression of antiapoptotic protein BCL-2 and the hybrid gene bcr/abl in K562 cells contributes resistance to DOX. Studies have shown that curcumin (CUR) has a pleiotropic therapeutic effect in cancer treatment, as it is an inhibitor of nuclear factor kappa B (NFκB) as well as a potent downregulator of MDR transporters. In this study, we investigated the potential benefit of using DOX and CUR in a single nanoparticle (NP) formulation to inhibit the development of drug resistance for the enhancement of antiproliferative activity of DOX in K562 cells. Results illustrate that the dual (DOX+CUR) drug loaded NPs were effectively delivered into K562 cells. CUR not only facilitates the retention of DOX in nucleus for a longer period of time but also inhibits the gradual expression of MDR1 and BCL-2 at the mRNA level in K562 cells. Moreover, Western blot results confirm that in combination both of the drugs were capable of inducing apoptosis even if in a lower concentration compared to either single drug in both solution or in formulation. Combinational therapy by using DOX and CUR, especially when administered in the NP formulation, has enhanced the cytotoxicity in K562 cells by promoting the apoptotic response. Overall, this combinational strategy has significant promise in the clinical management of intractable diseases, especially leukemia.

Evaluation of cytotoxicity and mechanism of apoptosis of doxorubicin using folate-decorated chitosan nanoparticles for targeted delivery to retinoblastoma

Nanoparticles are the new entities that can greatly limit the various side effects of systemic chemotherapy, and that coupled with a targeting moiety enables site-specific delivery of drugs. Folate receptors are overexpressed in retinoblastoma cells, thus these can specifically uptake the drug-loaded nanoparticles, thereby increasing the cytotoxicity at the tumor site. In our work, doxorubicin-loaded chitosan nanoparticles was prepared and then conjugated to folic acid. The conjugation efficiency was characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy. Thereafter, the efficacy of FA-conjugated DOX-CNPs on retinoblastoma cells (Y-79) was analyzed by MTT assay which demonstrated superior cytotoxic effects as compared to unconjugated DOX-CNPs and native DOX. This may be due to enhanced intracellular uptake of DOX-CNPs-FA (30%) than that of DOX-CNPs (13.24%) and native DOX (5.01%), resulting from the high affinity of FA for folate receptors. Finally, the mechanism of doxorubicin-mediated apoptosis in retinoblastoma cell line (Y-79) was investigated which demonstrated that the mitochondrial pathway is activated and that the FA-conjugated DOX-CNPs are most effective and causes enhanced release of cytochrome c as well as the activation of downstream caspases to assist in apoptosis. Thus, the FA-targeted NPs were proved to possess sustainable, controlled, and targeted delivery of anticancer drugs with DOX as a model drug, which may provide a drug delivery system of precise control and targeting effect for the treatment of retinoblastoma.

Hepatocyte growth factor prevents advanced glycation end products-induced injury and oxidative stress through a PI3K/Akt-dependent pathway in human endothelial cells

AIMS

Advanced glycation end products (AGEs) trigger an oxidative reaction which then accelerates endothelial cell apoptosis; this is a critical event in the process of diabetic vascular complications. We previously demonstrated that hepatocyte growth factor (HGF) protects human endothelial cells against AGE-induced injury. The present study was designed to investigate the possible involvement of MAPK and PI3K/Akt signaling in the action of HGF.

MAIN METHODS

HUVECs were treated with AGEs in the presence or absence of HGF. For detection of apoptosis, the morphological Acridine Orange staining, flow cytometry, and caspase-3 activity assay were used. Generation of reactive oxygen species (ROS) and the change in mitochondrial membrane potential were measured using flow cytometry and fluorescence immune analysis. The activation of MAPK and Akt was assayed by Western blot.

KEY FINDINGS

HGF exerted its prosurvival effect by inhibiting the overproduction of intracellular ROS and the depolarization of mitochondrial membrane, induced by AGEs. HGF-induced survival correlated with Akt activity and was inhibited by the specific PI3K inhibitor. ERK also was activated by HGF and rescued cells from apoptosis, although the cytoprotective effect was less marked than for PI3K/Akt. HGF-mediated survival was independent of JNK and p38MAPK pathways. Furthermore, blocking the PI3K and Akt activities with PI3K inhibitors or transfection of HUVECs with the dominant-negative p85 or Akt effectively abolished the inhibition of the intracellular ROS production and mitochondrial damage.

SIGNIFICANCE

Our studies suggest that HGF, via PI3K/Akt signaling, prevents AGE-induced apoptosis and oxidative stress through the inhibition of mitochondrial damage in HUVECs.

Functional and molecular interactions between the HGF/c-Met pathway and c-Myc in large-cell medulloblastoma

The growth factor hepatocyte growth factor (HGF), also known as scatter factor, and its tyrosine kinase receptor c-Met play important roles in medulloblastoma malignancy. The transcription factor c-Myc is another contributor to the malignancy of these most common pediatric brain tumors. In the present study, we observed strong morphological similarities between medulloblastoma xenografts overexpressing HGF and medulloblastoma xenografts overexpressing c-Myc. We therefore hypothesized a biologically significant link between HGF/c-Met and c-Myc in medulloblastoma malignancy and studied the molecular and functional interactions between them. We found that HGF induces c-Myc mRNA and protein in established and primary medulloblastoma cells. HGF regulated c-Myc levels via transcriptional and post-transcriptional mechanisms as evidenced by HGF induction of c-Myc promoter activity and induction of c-Myc protein levels in the setting of inhibited transcription and translation. We also found that HGF induces cell cycle progression, cell proliferation, apoptosis and increase in cell size in a c-Myc-dependent manner. Activation of MAPK and PI3K, inhibition of GSK-3beta and translocation of beta-catenin to the nucleus as well as Tcf/Lef transcriptional activity were involved in mediating c-Myc induction by HGF. Induction of Cdk2 kinase activity was involved in mediating the cell cycle progression effects, and downregulation of Bcl-XL was involved in mediating the proapoptotic effects of HGF downstream of c-Myc. All molecules that mediated the effects of HGF on c-Myc expression, cell proliferation and apoptosis were expressed in human large-cell medulloblastoma tissues. We therefore established for the first time a functional cooperation between HGF/c-Met and c-Myc in human medulloblastoma and elucidated the molecular mechanisms of this cooperation. The findings provide a potential explanation for the high frequency of c-Myc overexpression in medulloblastoma and suggest a cooperative role for c-Met and c-Myc in large-cell anaplastic medulloblastoma formation.

Mimp, a mitochondrial carrier homologue, inhibits Met-HGF/SF-induced scattering and tumorigenicity by altering Met-HGF/SF signaling pathways

We have recently shown that Mimp, a mitochondrial carrier protein homologue, is induced by Met-hepatocyte growth factor/scatter factor (HGF/SF) signaling and decreases the mitochondrial membrane potential in DA3 mammary adenocarcinoma cells. We show here that induction of Mimp leads to growth arrest in response to HGF/SF by arresting cells at the S phase of the cell cycle. Induction of Mimp or its transient expression does not lead to apoptosis. Mimp also attenuates HGF/SF-induced cellular scattering in vitro and tumor growth in vivo. The exogenous induction of Mimp at levels similar to its endogenous induction by HGF/SF increases the level of the Met protein and its phosphorylation by HGF/SF but reduces the levels of Shc and prevents the HGF/SF-induced tyrosine phosphorylation of Grb2 and Shc. In contrast, the level of phosphatidylinositol 3-kinase (PI3K) increases following Mimp induction and the level of phosphorylated PI3K in response to HGF/SF is unaffected by the exogenous induction of Mimp. Moreover, exogenous Mimp prevents the HGF/SF-induced transcription of the serum response element-luciferase reporter gene. Our results show that Mimp expression reduces Met-HGF/SF-induced proliferation and scattering by attenuating and altering the downstream signaling of Met. These data show a new link between a tyrosine kinase growth factor receptor and a mitochondrial carrier homologue that regulates cellular growth, motility, and tumorigenicity.

Multiple pathways regulating the anti-apoptotic protein clusterin in breast cancer

Cancer chemotherapy inhibits tumor growth, in part, by triggering apoptosis, and anti-apoptotic proteins reduce the effectiveness of chemotherapy. Clusterin, a chaperone-like protein that binds to apoptotic and DNA repair proteins, is induced by chemotherapy and promotes tumor cell survival. Histone deacetylase inhibitors (HDIs) such as sodium butyrate and suberoylanilide hydroxamic acid (SAHA) are pharmacological agents that induce differentiation and apoptosis in cancer cells by altering chromatin structure, and we have found that combinations of chemotherapeutic drugs such as doxorubicin and HDIs efficiently induce apoptosis, even though they paradoxically induce high levels of clusterin. The hyper-expressed form of clusterin localizes to mitochondria, inhibits cytochrome c release, and is inhibited by the proteasome. When HDIs are used as single agents, clusterin suppresses cytochrome c release and apoptosis. However, doxorubicin/HDI-induced apoptosis is not inhibited by clusterin, and clusterin-resistant apoptosis corresponds with markers of the extrinsic/receptor-mediated apoptotic pathway. Thus, chemotherapy-HDI combinations are capable of overcoming an innate anti-apoptotic pathway of tumor cells, suggesting that chemotherapy-HDI combinations have potential for treating advanced stage breast cancer.

Effect of hepatocyte growth factor (HGF) on the level of Survivin & XIAP expression in several human cancer cell lines, after treating with DNA damaging agent

Hepatocyte growth factor (HGF) has opposite biological activities in regulating apoptosis, also underlying molecular mechanisms are not clearly defined. We investigated HGF ability to inhibit cell death, which was induced by Doxorubicin, a DNA damaging agent. Also Survivin and XIAP mRNA levels were compared in HGF treated and non-treated cells. Cell proliferation and death were assessed using MTT assay and dye exclusion tests. Quantitative real-time PCR was used to evaluate Survivin and XIAP expression levels after treatment with HGF. ELISA was performed to quantify HGF secretion in the selected cancer cell lines media. HGF appeared to have inhibitory effect on Doxorubicin induced cell death in all of the studied cell lines. It had minimal effect on XAIP and Survivin expression levels in MRC-5, MOLT-4 and AGS cell lines; except for XIAP expression level in AGS cell line, which was increased substantially after treatment. Surprisingly, in KG-1 cell line, XIAP and Survivin expression levels were significantly reduced after HGF treatment. Although several members of IAP gene family are reported to play role in HGF mediated cytoprotective pathway, we showed that XIAP and Survivin do not seem to be involved.

HGF/SF regulates expression of apoptotic genes in MCF-10A human mammary epithelial cells

Hepatocyte growth factor/scatter factor (HGF/SF) induces scattering, morphogenesis, and survival of epithelial cells through activation of the MET tyrosine kinase receptor. HGF/SF and MET are involved in normal development and tumor progression of many tissues and organs, including the mammary gland. In order to find target genes of HGF/SF involved in its survival function, we used an oligonucleotide microarray representing 1,920 genes known to be involved in apoptosis, transcriptional regulation, and signal transduction. MCF-10A human mammary epithelial cells were grown in the absence of serum and treated or not with HGF/SF for 2 h. Total RNA was reverse-transcribed to cDNA in the presence of fluorescent Cy3-dUTP or Cy5-dUTP to generate fluorescently labeled cDNA probes. Microarrays were performed and the ratios of Cy5/Cy3 fluorescence were determined. The expression of three apoptotic genes was modified by HGF/SF, with A20 being upregulated, and DAXX and SMAC being downregulated. These changes of expression were confirmed by real-time quantitative PCR. According to current-knowledge, A20 is antiapoptotic and SMAC is proapoptotic, while a pro- or antiapoptotic function of DAXX is controversial. The fact that HGF/SF upregulates an antiapoptotic gene (A20) and downregulates a proapoptotic gene (SMAC) is in agreement with its survival effect in MCF-10A cells. This study identified novel apoptotic genes regulated by HGF/SF, which can contribute to its survival effect.

Akt Attenuation of the Serine Protease Activity of HtrA2/Omi through Phosphorylation of Serine 212

The serine protease HtrA2/Omi is released from the mitochondria into the cytosol following apoptosis stimuli, leading to the programmed cell death in caspase-dependent and -independent manners. The function of HtrA2/Omi closely relates to its protease activity, which is required for cleavage of its substrate such as the members of the X-linked inhibitor of apoptotic protein family. However, the regulation of HtrA2/Omi by signaling molecule has not been documented. Here we report that serine/threonine kinases Akt1 and Akt2 phosphorylate mitochondria-released HtrA2/Omi on serine 212 in vivo and in vitro, which results in attenuation of its serine protease activity and pro-apoptotic function. Abolishing HtrA2/Omi phosphorylation by Akt through mutation of serine 212 to alanine (HtrA2/Omi-S212A) retains its serine protease activity and induces more apoptosis as compared with wild-type HtrA2/Omi. Conversely, HtrA2/Omi-S212D, a mutant mimicking phosphorylation, lost the protease activity and failed to induce the programmed cell death. Furthermore, the phosphorylated HtrA2/Omi fails to cleave X-linked inhibitor of apoptotic protein without interfering with their complex formation. In addition, Akt inhibits the release of HtrA2/Omi from the mitochondria into the cytoplasm in response to cisplatin treatment. These data reveal for the first time that HtrA2/Omi is directly regulated by Akt and provide a mechanism by which Akt induces cell survival at post-mitochondrial level.

Selective Cytochrome c Displacement by Phosphate and Ca2+ in Brain Mitochondria

In brain mitochondria, phosphate- and Ca(2+)-dependent cytocrome c (cyt c) release reveals pools that interact differently with the inner membrane. Detachment of the phosphate-dependent pool did not influence the pool released by Ca(2+). Cyt c pools were also detected in a system of cyt c reconstituted in cardiolipin (CL) liposomes. Gradual binding of cyt c (1 nmol) to CL/2-[12-(7-nitrobenz- 2-oxa-1,3-diazol-4-yl)amino]dodecanoyl-1-hexadecan oyl-sn-glycero-3-phosphocholine (NBDC(12)-HPC) liposomes (10 nmol) produced NBD fluorescence quenching up to 0.4 nmol of added protein. Additional bound cyt c did not produce quenching, suggesting that cyt c-CL interactions originate distinct cyt c pools. Cyt c was removed from CL/NBDC(12)-HPC liposomes by either phosphate or Ca(2+), but only Ca(2+) produced fluorescence dequenching and leakage of encapsulated 8-aminonaphthalene-1,3,6-trisulfonic acid/p-xylene-bis-pyridinium bromide. In mitochondria, complex IV activity and mitochondrial membrane potential (Deltapsi(m)) were not affected by the release of the phosphate-dependent cyt c pool. Conversely, removal of cyt c by Ca(2+) caused inhibition of complex IV activity and impairment of Deltapsi(m). In a reconstituted system of mitochondria, nuclei and supernatant, cyt c detached from the inner membrane was released outside mitochondria and triggered events leading to DNA fragmentation. These events were prevented by enriching mitochondria with exogenous CL or by sequestering released cyt c with anti-cyt c antibody.

Effect of Akt inhibition on scatter factor-regulated gene expression in DU-145 human prostate cancer cells

The cytokine scatter factor (SF) (hepatocyte growth factor) transduces various biologic actions, including cell motility, invasion, angiogenesis and apoptosis inhibition. The latter is relevant to understanding the role of SF in promoting tumor cell survival in different contexts, for example, detachment from basement membrane, growth in metastatic sites and responses to chemo- and radiotherapy. Previously, we showed that SF protects cells against apoptosis owing to DNA damage, by a mechanism involving phosphoinositol-3-kinase/c-Akt signaling. Here, we used DNA microarray assays to identify c-Akt-regulated genes that might contribute to cell protection. DU-145 human prostate cancer cells were transfected+/-a dominant-negative mutant Akt, treated+/-SF and analysed for gene expression using Affymetrix arrays. These studies identified SF-regulated genes for which induction was c-Akt-dependent vs -independent. Selected microarray findings were confirmed by semiquantitative and quantitative reverse transcription-polymerase chain reaction. We tested the contribution of four SF-inducible/c-Akt-dependent genes (AMPD3, EPHB2, MX1 and WNT4) to protection against adriamycin (a DNA topoisomerase IIalpha inhibitor) using RNA interference. Knockdown of each gene except EPHB2 caused a small but significant reduction in the SF cell protection. The lack of effect of EPHB2 knockdown may be due to the fact that DU-145 cells contain a single-mutant EPHB2 allele. A combination of three small interfering RNAs blocked most of the protection by SF in both DU-145 and T47D cells. These findings identify novel c-Akt-regulated genes, some of which contribute to SF-mediated cytoprotection.

A positive feedback loop between hepatocyte growth factor receptor and beta-catenin sustains colorectal cancer cell invasive growth

Overexpressed or activated hepatocyte growth factor receptor, encoded by the MET proto-oncogene, was found in the majority of colorectal carcinomas (CRCs), whose stepwise progression to malignancy requires transcriptional activation of beta-catenin. We here demonstrate that a functional crosstalk between Met and beta-catenin signaling sustains and increases CRC cell invasive properties. Hepatocyte growth factor (HGF) stimulation prompts beta-catenin tyrosine phosphorylation and dissociation from Met, and upregulates beta-catenin expression via the phosphatidylinositol 3-kinase pathway in conditions that mimic those found by the invading and metastasizing cells. Additionally, a transcriptionally active form of beta-catenin, known to be oncogenic, enhances Met expression. Furthermore, HGF treatment increases the activity of the beta-catenin-regulated T-cell factor transcription factor in cells expressing the wild-type or the oncogenic beta-catenin. In the mirror experiments, either Met or beta-catenin knocking down also reduces their protein level. In biological assays, beta-catenin knocking down abrogates the HGF-induced motile phenotype, whereas active beta-catenin fosters ligand-independent cell scattering. Met and beta-catenin also cooperate in promoting entry into the cell cycle and in protecting cells from apoptosis. In conclusion, Met and beta-catenin pathways are mutually activated in CRC cells. This might generate a self-amplifying positive feedback loop resulting in the upregulation of the invasive growth properties of CRC cells.

Expression and localization of hepatocyte growth factor and its receptor c-Met in inverted papillomas

CONCLUSIONS

The results suggest that elevated c-Met expression in combination with the co-expression of hepatocyte growth factor (HGF) in the epithelial cells of inverted papilloma may proliferate the epithelial cells of inverted papilloma.

OBJECTIVES

HGF and its receptor, c-Met, have been identified in a variety of neoplastic and normal tissue types, implicating these factors in tissue regeneration and tumor progression. We investigated the expression and distribution of HGF and c-Met in normal nasal mucosa and inverted papilloma, to evaluate the possible influence of HGF and c-Met on the development of inverted papilloma.

MATERIALS AND METHODS

Normal inferior turbinate mucosa and inverted papilloma were examined for expression of HGF and c-Met using RT-PCR, immunohistochemistry and Western blot analysis.

RESULTS

Using immunohistochemistry, moderate to high levels of HGF and c-Met protein were localized in epithelial cells in inverted papillomas tested in the present study. In normal turbinate mucosa immunopositive HGF was detected in the submucosal glands where faint staining was found. However, c-Met was noted in the epithelial cells and submucosal glands of normal turbinate mucosa. RT-PCR and Western blot analysis showed that the expression levels of HGF and c-Met were increased in inverted papilloma in comparison with the normal turbinate mucosa.

Hepatocyte growth factor increases mitochondrial mass in glioblastoma cells

Hepatocyte growth factor/scatter factor (HGF) is a multifunctional growth factor that is linked to the initiation and/or progression of numerous malignancies. HGF also alters cancer cell responses to DNA damaging cytotoxic agents. Many cell responses to Met activation require alterations in metabolic activity but how the metabolic machinery responds to Met activation remains poorly defined. Treating human glioblastoma cells with HGF followed by the topoisomerase inhibitor camptothecin was found to increase the activity per cell of the mitochondrial respiratory chain enzyme succinate-tetrazolium reductase (>80% increase, p < 0.05) and the tricarboxylic acid cycle enzyme succinate dehydrogenase (>25% increase, p < 0.05). Treatment with either HGF or camptothecin alone had no effect on enzyme activity. The mitochondrial enzymatic response to HGF was dose- and time-dependent with the maximum increase occurring in cells pre-treated with 30 ng/ml HGF for 48h prior to camptothecin exposure. This enzymatic response was associated with a concurrent increase in mitochondrial mass of comparable magnitude (approximately 56%, p < 0.05) as measured by fluorescent mitochondrial staining and flow cytometry. The mitochondrial mass response to HGF was prevented by the MAP-kinase pathway inhibitor PD98059 and was unaffected by the phosphatidylinositol 3-kinase inhibitors LY294002 and wortmannin. These findings suggest that HGF influences cell responses to chemotherapeutic stress, in part, by altering mitochondrial functions through a MAP-kinase dependent increase in mitochondrial mass.

Akt-mediated cisplatin resistance in ovarian cancer: modulation of p53 action on caspase-dependent mitochondrial death pathway

Akt is a determinant of cisplatin [cis-diammine-dichloroplatinum (CDDP)] resistance in ovarian cancer cells, and this may be related to the regulation of p53. Precisely how Akt facilitates CDDP resistance and interacts with p53 is unclear. Apoptotic stimuli induce second mitochondria-derived activator of caspase (Smac) release from mitochondria into the cytosol, where it attenuates inhibitor of apoptosis protein-mediated caspase inhibition. Whereas Smac release is regulated by p53 via the transactivation of proapoptotic Bcl-2 family members, it is unclear whether p53 also facilitates Smac release via its direct mitochondrial activity. Here we show that CDDP induces mitochondrial p53 accumulation, the mitochondrial release of Smac, cytochrome c, and HTR/Omi, and apoptosis in chemosensitive but not in resistant ovarian cancer cells. Smac release was p53 dependent and was required for CDDP-induced apoptosis. Mitochondrial p53 directly induced Smac release. Akt attenuated mitochondrial p53 accumulation and Smac/cytochrome c/Omi release and conferred resistance. Inhibition of Akt facilitated Smac release and sensitized chemoresistant cells to CDDP in a p53-dependent manner. These results suggest that Akt confers resistance, in part, by modulating the direction action of p53 on the caspase-dependent mitochondrial death pathway. Understanding the precise etiology of chemoresistance may improve treatment for ovarian cancer.

Hepatocyte Growth Factor Modulates H2O2-Induced Mesangial Cell Apoptosis through Induction of Heme Oxygenase-1

Oxidative stress plays an important role in the induction of mesangial cell (MC) injury. In the present study, we evaluated the molecular mechanism involved in hydrogen peroxide (H2O2)-induced MC apoptosis. In addition, we examined the role of heme oxygenase-1 (HO-1) in hepatocyte growth factor (HGF)-modulated, H2O2-induced MC injury. H2O2 promoted (p < 0.001) mouse MC (MMC) apoptosis. This effect of H2O2 was associated with translocation of cytochrome c from the mitochondrial to the cytosolic compartment. In addition, a caspase-9 inhibitor partially attenuated this effect of H2O2. These findings suggest that H2O2-induced MMC apoptosis is mediated through the mitochondrial pathway. HGF not only prevented H2O2-induced MMC apoptosis, but also inhibited H2O2-induced translocation of cytochrome c from the mitochondrial to the cytosolic compartment. HGF also promoted the expression of HO-1 by MMCs; interestingly, hemin inhibited (p < 0.001) H2O2-induced MMC apoptosis. On the other hand, zinc protoporphyrin inhibited the protective influence of HGF on H2O2-induced MMC apoptosis. These findings suggest that H2O2-induced apoptosis occurs through the mitochondrial pathway. HGF provides protection against H2O2-induced MMC apoptosis through induction of HO-1.

Hpr6 (heme-1 domain protein) regulates the susceptibility of cancer cells to chemotherapeutic drugs

Cancer cells have varying levels of susceptibility to chemotherapeutic agents, and the proteins that direct drug susceptibility are promising targets for intervention in cancer. Hpr6 (heme-1 domain protein)/PGRMC1 (progesterone receptor membrane component 1) is overexpressed in tumors, and Hpr6 is the human homolog of a budding yeast damage resistance gene called Dap1p. Cells lacking Dap1p are damage-sensitive, and we have found that inhibition of Hpr6 expression by RNA inhibition (RNAi) increases sensitivity of breast cancer cells to chemotherapeutic drugs. Hpr6 is composed largely of a cytochrome b(5)-related heme-1 domain, and we have found that purified Hpr6 binds to heme, similar to its yeast and rodent homologues. We generated an aspartate 120-to-glycine (D120G) mutant of Hpr6 at a highly conserved site in the heme-1 domain and demonstrated that Hpr6-D120G cannot bind to heme. The Hpr6-D120G mutant was named Hpr6(hbd) for heme binding defective. We prepared an adenovirus encoding Hpr6(hbd) and found that adenovirus Hpr6(hbd) increases susceptibility of breast cancer cells to doxorubicin and camptothecin. Our findings support a model in which Hpr6, similar to its yeast homolog, binds to heme and regulates susceptibility to damaging agents.

SV40-dependent AKT activity drives mesothelial cell transformation after asbestos exposure

Human malignant mesothelioma is an aggressive cancer generally associated with exposure to asbestos, although SV40 virus has been involved as a possible cofactor by a number of studies. Asbestos fibers induce cytotoxicity in human mesothelial cells (HMC), although cell survival activated by key signaling pathways may promote transformation. We and others previously reported that SV40 large T antigen induces autocrine loops in HMC and malignant mesothelioma cells, leading to activation of growth factor receptors. Now we show that SV40 induces cell survival via Akt activation in malignant mesothelioma and HMC cells exposed to asbestos. Consequently, prolonged exposure to asbestos fibers progressively induces transformation of SV40-positive HMC. As a model of SV40/asbestos cocarcinogenesis, we propose that malignant mesothelioma originates from a subpopulation of transformed stem cells and that Akt signaling is a novel therapeutic target to overcome malignant mesothelioma resistance to conventional therapies.

Role of NF-kappaB signaling in hepatocyte growth factor/scatter factor-mediated cell protection

The cytokine scatter factor/hepatocyte growth factor (HGF/SF) protects epithelial, carcinoma, and other cell types against cytotoxicity and apoptosis induced by DNA-damaging agents such as ionizing radiation and adriamycin (ADR, a topoisomerase IIalpha inhibitor). We investigated the role of nuclear factor kappa B (NF-kappaB) signaling in HGF/SF-mediated protection of human prostate cancer (DU-145) and Madin-Darby canine kidney (MDCK) epithelial cells against ADR. HGF/SF caused the rapid nuclear translocation of the p65 (RelA) subunit of NF-kappaB associated with the transient loss of the inhibitory subunit IkappaB-alpha. Exposure to HGF/SF caused the activation of an NF-kappaB luciferase reporter that was blocked or attenuated by the expression of a mutant 'super-repressor' IkappaB-alpha. Electrophoretic mobility shift assay supershift assays revealed that HGF/SF treatment induced the transient binding of various NF-kappaB family proteins (p65, p50, c-Rel, and RelB) with radiolabeled NF-kappaB-binding oligonucleotides. The HGF/SF-mediated protection of DU-145 and MDCK cells against ADR (demonstrated using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays) was abrogated by the IkappaB-alpha super-repressor. The ability of HGF/SF to activate NF-kappaB signaling was dependent on c-Akt --> Pak1 (p21-associated kinase-1) signaling (with Pak1 downstream of c-Akt) and was inhibited by the tumor suppressor PTEN (phosphatase and tensin homolog). Inhibitors of phosphatidylinositol-3'-kinase and Src family kinases significantly inhibited HGF/SF-mediated activation of NF-kappaB, while inhibitors of MEK, protein kinase C, and p70 S6 kinase had a modest effect or no effect on NF-kappaB activity. HGF/SF induced the expression of several known NF-kappaB target genes (cIAP-1 (cellular inhibitor of apoptosis-1), cIAP-2, and TRAF-2 (TNF receptor-associated factor-2)) in an NF-kappaB-dependent manner; HGF/SF blocked the inhibition of expression of these genes by ADR. Experimental manipulation of expression of these genes suggests that they (particularly TRAF-2 and cIAP-2) contribute to the protection against ADR by HGF/SF. These findings suggest that HGF/SF activates NF-kappaB through a c-Akt --> Pak1 signaling pathway that is also dependent on Src, and that NF-kappaB contributes to HGF/SF-mediated protection against ADR.

Microarray analysis of prostate cancer progression to reduced androgen dependence: studies in unique models contrasts early and late molecular events

Three unique variants of the CWR22 human prostate cancer xenograft model (CWR22LD1, LD2, and LD3) with a decrease in dependence on androgens were selected under noncastrate conditions, i.e., by outgrowth after transplantation into male NCR (AT) nu mice without testosterone supplementation. These variants were unable to grow in castrated male mice. For comparison, a second set of variants with even less dependence on androgens (castrate-resistant) were derived following outgrowth from CWR22 (CWR22Rv1 and RC) or CWRLD1 (CWR22RS) after transplantion in castrated male mice. The androgen receptor (AR) gene in the CWR22LD variants was transcriptionally active and was neither mutated nor significantly overexpressed compared to CWR22. Oligonucleotide microarray analysis showed distinctly different profiles of dysregulated gene expression among the CWR22LD variants. Groups of only 26-41 genes were dysregulated greater than threefold with a different proportion of up versus downregulated genes in each variant. Only one of the castrate-resistant variants (CWR22Rv1) had a highly overexpressed AR gene but AR in this variant and the two other castrate-resistant variants, CWR22 RS and RC, was not mutated beyond that seen in CWR22. In contrast to the CWR22LD variants, a total of 342, 295, and 222 genes were dysregulated at least threefold in CWR22Rv1, CWR22RS, and CWR22RC, respectively, differing as well in the proportion of up versus downregulated genes. Many of the genes dysregulated in CWR22LD1, LD2, and LD3 were further dysregulated in CWR22Rv1, RC, or RS. The most downregulated gene was microseminoprotein beta (MSPB). Along with cyclin D1, the most upregulated gene by an order of magnitude compared to other upregulated genes was hepatocyte growth factor (HGF) (scatter factor). These results suggest that the onset in the loss of androgen dependence in CWR22 proceeds through multiple pathways and does not require any direct change in the status of AR. However, upregulation of other survival pathways like that involving HGF in these studies could co-activate AR signaling. The endogenous overexpression of genes regulating sterol biosynthesis also observed in castrate-resistant CWR22 variants delineated a clinically relevant, compensatory mechanism for overcoming androgen deprivation reaffirming a central role for AR signaling in this process.

Ceramide-induced apoptosis: role of catalase and hepatocyte growth factor

The aim of this study was to elucidate cellular mechanisms involved in ceramide-induced apoptosis and its attenuation by hepatocyte growth factor (HGF). Human retinal pigmented epithelial cells (RPE) incubated with C2 ceramide accumulated reactive oxygen species (ROS) in mitochondria and underwent apoptosis in a dose-dependent manner. Ceramide-treated cells showed increased caspase-3 activation and an increase in mitochondrial membrane permeability transition (MPT). Low doses of H2O2 (100 microM) alone induced negligible apoptosis; however, ceramide-induced apoptosis was significantly enhanced by co-incubation with H2O2 (100 microM). Furthermore, ceramide treatment significantly decreased catalase enzymatic activity and protein expression. HGF pretreatment (20 ng/ml) significantly inhibited ceramide-induced apoptosis and reduced the accumulation of ROS, the activation of caspase-3, and the increase in MPT and prevented the reduction in catalase activity and expression. Together, the data suggest that ceramide induces apoptosis in RPE cells by increasing ROS production, MPT, and caspase-3 activation. The ceramide effect is potentiated by H2O2 and associated with a reduction in catalase activity, suggesting that catalase plays a central role in regulating this apoptotic response. The ability of HGF to attenuate these effects demonstrates its effectiveness as an antioxidant growth factor.

Inhibition of JNK by HGF/SF prevents apoptosis induced by TNF-alpha

We investigated whether repression of JNK by hepatocyte growth factor/scatter factor (HGF/SF) in MDCK epithelial cells is linked to its ability to protect cells from apoptosis. To this purpose, cells were treated by TNF-alpha, a well-known inducer of JNK and of cell death, and the effects of HGF/SF were investigated under these conditions. We identified repression of JNK as a signaling target of HGF/SF for protection against TNF-alpha-induced cell death. This effect of HGF/SF occurs via the activation of the PI3K and MEK1 pathways.

Suppression of adriamycin-induced apoptosis by sustained activation of the phosphatidylinositol-3'-OH kinase-Akt pathway

The mechanisms by which growth factors trigger signal transduction pathways leading to protection against apoptosis are of great interest. In this study, we investigated the effect of hepatocyte growth factor (HGF/SF) and epidermal growth factor (EGF) on adriamycin (ADR)-induced apoptosis. Treatment of human epithelial MKN74 cells with ADR, a DNA topoisomerase IIalpha inhibitor, caused apoptosis. However, cells pretreated with HGF/SF, but not those pretreated with EGF, were resistant to this apoptosis. The protective effect of HGF/SF against the ADR-induced apoptosis was abolished in the presence of either LY294002, an inhibitor of phosphatidylinositol-3'-OH kinase (PI3-K) or 1L-6-hydroxymethyl-chiro-inositol 2-(R)-2-O-methyl-3-O-octadecylcarbonate, an inhibitor of Akt, thus implicating the activation of PI3-K-Akt signaling in the antiapoptotic action of HGF/SF. Immunoblotting analysis revealed that HGF/SF stimulated the sustained phosphorylation of Akt for several hours but that EGF stimulated the phosphorylation only transiently. Furthermore, ADR-induced activation of caspase-9, a downstream molecule of Akt, was inhibited for at least 24 h after HGF/SF stimulation, but it was not affected by EGF stimulation. Cell-surface biotin-labeling analysis showed that the HGF/SF receptor remained on the cell surface until at least 30 min after HGF/SF addition but that the EGF receptor level on the cell surface was attenuated at an earlier time after EGF addition. These results indicate that HGF/SF, but not EGF, transmitted protective signals against ADR-induced apoptosis by causing sustained activation of the PI3-K-Akt signaling pathway. Furthermore, the difference in antiapoptotic capacity between HGF/SF and EGF is explained, at least in part, by the delayed down-regulation of the HGF/SF receptor.

Oxidant-induced cell death in retinal pigment epithelium cells mediated through the release of apoptosis-inducing factor

In the present study, the pathways involved in oxidant-induced cell death of a primary cell of the retina, ARPE-19, were investigated and compared with a leukemic cell, U937 cells. Both ARPE-19 and U937 cells exhibited similar viability when exposed to menadione. At lethal doses, both cell lines demonstrated extensive membrane blebbing. However, although U937 cells exhibited caspase-3, -9 PARP cleavage and 200 bp laddering, no such cleavage or laddering was noted in ARPE-19 cells. Furthermore, addition of exogenous cytochrome c and ATP to a cell-free system again resulted in cleavage of caspase-3 and -9 in extracts of U937 but not ARPE cells. Further studies in ARPE-19 cells undergoing menadione-induced cell death demonstrated mitochondrial membrane depolarization, release of cytochrome c, nuclear translocation of apoptosis-inducing factor and subsequent 50 kilo-base pair laddering, and nuclear shrinkage. All of these findings were abrogated by the pretreatment of ARPE-19 cells with hepatocyte growth factor/scatter factor. These findings demonstrate the complex nature of cell death in primary cells of the retina and highlight the role of caspase-independent signals, growth factors and intracellular survival factors in programmed cell death pathways.

Hepatocyte growth factor inhibits anoikis by induction of activator protein 1-dependent cyclooxygenase-2. Implication in head and neck squamous cell carcinoma progression

Anoikis, also called suspension-induced apoptosis, plays an important role in tumor development, progression, and metastasis. Recently we found that hepatocyte growth factor (HGF) inhibited anoikis of human head and neck squamous cell carcinoma (HNSCC) cells by activating the extracellular signal-regulated kinase (ERK)-signaling pathway. However, the anti-apoptotic effectors that were regulated by the ERK-signaling pathway were unknown. Here we report that HGF-mediated inhibition of anoikis was dependent on activator protein-1 activity through the activation of the ERK-signaling pathway. Using a combination of microarray analysis and Northern blot analysis, we found that an anti-apoptotic gene cyclooxygenase-2 (cox-2) was induced by HGF in an activator protein-1-dependent fashion. Inhibition of Cox-2 activity partially abolished HGF-mediated cell survival, and overexpression of Cox-2 in HNSCC cells provided resistance against anoikis. Moreover, HNSCC cells stably expressing Cox-2 had aggressive tumor growth in a nude mouse model compared with control cells. Taken together, our results demonstrate that Cox-2 plays an important role in HGF-mediated anoikis resistance. HGF may stimulate the progression and growth of HNSCC in vivo by induction of Cox-2.

Hepatocyte growth factor inhibits anoikis in head and neck squamous cell carcinoma cells by activation of ERK and Akt signaling independent of NFkappa B

Hepatocyte growth factor (HGF), also known as a scatter factor, regulates a variety of biological activities including cell proliferation, survival, migration, and angiogenesis. Importantly, HGF and its receptor c-Met have been found to be associated with metastasis of human head and neck squamous cell carcinoma (HNSCC). Because anoikis resistance plays an important role in tumor progression and metastasis, here we examined whether HGF suppressed suspension-induced apoptosis (anoikis) in HNSCC cells, and if so, we assessed downstream signaling pathways mediated by HGF. We found that HNSCC cells underwent anoikis upon loss of matrix contact, whereas HGF provided protection against it. HGF-induced anoikis resistance was found to be dependent on both ERK and Akt signaling pathways. The inhibition of either ERK or Akt activation abolished HGF-mediated survival. Furthermore, we found that HGF did not activate NFkappaB transcription in HNSCC cells and that HGF-mediated anoikis resistance was independent of NFkappaB. Taken together, our results suggest that anoikis resistance induced by HGF may also play an important role in the progression and metastasis of HNSCC.