The hepatocyte growth factor/Met pathway in development, tumorigenesis, and B-cell differentiation

Activation of the Urokinase Plasminogen Activator/Urokinase Plasminogen Activator Receptor System in Periodontitis: A Case-Control Study

INTRODUCTION

The plasminogen activating (PA) system has a multitude of functions such as wound healing, proteolytic activity, collagen degradation and cell growth, and the role of the urokinase plasminogen activator/urokinase plasminogen activator receptor (uPA/uPAR) system has been studied in many disease states. The aim of this study was to investigate salivary concentrations of uPA, uPAR and uPA activity in patients with periodontitis to identify biomarkers and novel pathogenic relationships.

METHODS

Saliva samples were obtained from 169 participants, comprising patients with periodontitis (n = 103) and periodontally healthy volunteers (n = 66) and analysed for uPA and uPAR with a multiplex protein assay using proximity extension analysis in a subset of samples, followed by validation with ELISA. The protease activity of salivary uPA was quantified using a fluorometric assay.

RESULTS

Patients with periodontitis had a 4.0-fold higher (p < 0.001) salivary uPA and a 2.5-fold higher (p < 0.001) salivary uPAR concentration in comparison to periodontally healthy participants. The salivary uPA activity (median [IQR]) from patients with periodontitis (123.21 [188.29] U/mL) was 1.6-fold higher (p < 0.01) than the salivary uPA activity from periodontally healthy participants (76.83 [98.09] U/mL). Levels of uPA and uPAR were strongly correlated with periodontal indices, whereas only weak correlations were found with BMI and age.

CONCLUSION

Activation of uPA/uPAR likely plays a role in the pathogenesis of periodontal diseases. uPA/uPAR may have potential utility as candidate salivary biomarkers in periodontal pathogenesis.

Hydrogen sulfide suppresses H2O2-induced proliferation and migration of HepG2 cells through Wnt/β-catenin signaling pathway

Both H₂S and H₂O₂ affect many cellular events, such as cell differentiation, cell proliferation and cell death. However, there is some controversy about the roles of H₂S and H₂O_2, since the detailed mechanisms they are involved remain unclear. In this study, low concentration of H₂O₂ (40 μM) increased the viability of hepatocellular carcinoma cells HepG2, while both H₂S and high concentration of H₂O₂ decreased the cell viability in a dose-dependent manner. Wound healing assay indicated that 40 μM H₂O₂ promoted migration of HepG2 cells, which was suppressed by exogenous H₂S. Further analysis revealed that administration of exogenous H₂S and H₂O₂ changed the redox status of Wnt3a in HepG2 cells. Altered expression of proteins including Cyclin D1, TCF-4, and MMP7, which are downstream of the Wnt3a/β-catenin signaling pathway, were found after treatment with exogenous H₂S and H₂O₂. Compared with H₂S, low concentration of H₂O₂ showed opposite effects on these protein expression levels in HepG2 cells. These results suggest that H₂S suppressed H₂O₂-induced proliferation and migration of HepG2 through regulating Wnt3a/β-catenin signaling pathway.

Responses to the Tepotinib in Gastric Cancers with MET Amplification or MET Exon 14 Skipping Mutations and High Expression of Both PD-L1 and CD44

Both MET exon 14 skipping mutation (METex14SM) and high copy-number variation (CNV) lead to enhanced carcinogenesis; additionally, programmed-death ligand 1 (PD-L1) is often upregulated in cancers. In this study, we characterized the expression of MET (including METex14SM), PD-L1, and CD44 in human gastric cancer (GC) cells as well as the differential susceptibility of these cells to tepotinib. Tepotinib treatments inhibited the growth of five GC cells in a dose-dependent manner with a concomitant induction of cell death. Tepotinib treatments also significantly reduced the expression of phospho-MET, total MET, c-Myc, VEGFR2, and Snail protein in SNU620, MKN45, and Hs746T cells. Notably, tepotinib significantly reduced the expression of CD44 and PD-L1 in METex14SM Hs746T cells. By contrast, tepotinib was only slightly active against SNU638 and KATO III cells. Migration was reduced to a greater extent in the tepotinib-treated group than in the control group. Tepotinib may have therapeutic effects on c-MET-amplified GC, a high expression of both PD-L1 and CD44, and METex14SM. Clinical studies are needed to confirm these therapeutic effects.

Insight into the molecular pathogenesis of odontogenic lesions

BACKGROUND

Odontogenic tumors, derived from epithelial, ectomesenchymal, and/or mesenchymal elements of the tooth-forming apparatus, constitute a heterogeneous group of lesions, including hamartomas, benign and malignant neoplasms with metastatic capabilities.

HIGHLIGHT

This review provides a comprehensive overviewof the pathogenesis of odontogenic tumors and explains the associated molecular events in the context of hallmarks of cancer established by Hanahan D and Weinberg RA. Diagrammatic representations depicted in the article would facilitate easier understanding.

CONCLUSION

A better understanding of the pathogenesis of the lesions may assist in determining patient's prognosis and devising better targeted therapeutic treatment, thus, reducing the morbidity and mortalityof patients.

Multiple primary cancers (renal papillary, lymphoma and teratoma) and hepatic cysts in association with a pathogenic germline mutation in the MET gene

Activating germline mutations of the MET gene are associated with hereditary papillary renal cancer. This a very rare autosomal dominant condition, which is usually considered not to display a phenotype of multiple types of malignancy. However, this report describes the case of a man who has been affected with testicular teratoma, diffuse large B-cell lymphoma and multiple hepatic cysts, as well as multiple papillary renal cancers. There is good supporting evidence for roles of over-expression/activity of the HGF/MET ligand-receptor in development of these tumours, raising the possibility of other increased cancer risks associated with activating germline MET gene mutations.

Biology of Tumor Associated Macrophages in Diffuse Large B Cell Lymphoma

The tumor associated microenvironment is known to play a vital role during the development and progression of different malignant tumors. As a part of tumor microenvironment, tumor associated macrophages (TAMs) are crucial for the genesis, proliferation, metastasis, and survival of tumor cells. Recently, more and more studies showed that TAMs were related with poor clinical status and survival in patients with diffuse large B cell lymphoma (DLBCL). Considering the complex roles which TAMs play in the tumor microenvironment of DLBCL, the aim of this study was to review the biological mechanisms between TAMs and DLBCL cells, including extracellular matrix remodeling and angiogenesis promotion, tumor promotion, immune suppression, and phagocytosis inhibition. This review will help us to further understand the comprehensive impact of TAMs on DLBCL and explore possible prognostic markers and therapeutic targets.

Ellagitannin-rich cloudberry inhibits hepatocyte growth factor induced cell migration and phosphatidylinositol 3-kinase/AKT activation in colon carcinoma cells and tumors in Min mice

Berries have been found to inhibit colon carcinogenesis in animal models, and thus represent a potential source of compounds for prevention and treatment of colorectal cancer. The mechanistic basis for their effects is not well understood. We used human colon carcinoma cells and Min mice to investigate the effects of ellagitannin-rich cloudberry (Rubus chamaemorus) extract on cancer cell migration and underlying cell signaling. Intrinsic and hepatocyte growth factor (HGF) -induced cell motility in human HT29 and HCA7 colon carcinoma cells was assessed carrying out cell scattering and scratch wound healing assays using time-lapse microscopy. Activation of Met, AKT, and ERK in cell lines and tumors of cloudberry-fed Min mice were determined using immunoprecipitation, Western blot and immunohistochemical analyses. Cloudberry extract significantly inhibited particularly HGF-induced cancer cell migration in both cell lines. Cloudberry extract inhibited the Met receptor tyrosine phosphorylation by HGF and strongly suppressed HGF-induced AKT and ERK activation in both HT29 and HCA7 cells. Consistently, cloudberry feeding (10% w/w freeze-dried berries in diet for 10 weeks) reduced the level of active AKT and prevented phosphoMet localization at the edges in tumors of Min mice. These results indicate that cloudberry reduces tumor growth and cancer cell motility by inhibiting Met signaling and consequent activation of phosphatidylinositol 3-kinase/AKT in vitro and in tumors in vivo. As the Met receptor is recognized to be a major target in cancer treatment, our results suggest that dietary phytochemicals may have therapeutic value in reducing cancer progression and metastasis.

Genome-wide association study for host response to bovine leukemia virus in Holstein cows

The mechanisms of leukemogenesis induced by bovine leukemia virus (BLV) and the processes underlying the phenomenon of differential host response to BLV infection still remain poorly understood. The aim of the study was to screen the entire cattle genome to identify markers and candidate genes that might be involved in host response to bovine leukemia virus infection. A genome-wide association study was performed using Holstein cows naturally infected by BLV. A data set included 43 cows (BLV positive) and 30 cows (BLV negative) genotyped for 54,609 SNP markers (Illumina Bovine SNP50 BeadChip). The BLV status of cows was determined by serum ELISA, nested-PCR and hematological counts. Linear Regression Analysis with a False Discovery Rate and kinship matrix (computed on the autosomal SNPs) was calculated to find out which SNP markers significantly differentiate BLV-positive and BLV-negative cows. Nine markers reached genome-wide significance. The most significant SNPs were located on chromosomes 23 (rs41583098), 3 (rs109405425, rs110785500) and 8 (rs43564499) in close vicinity of a patatin-like phospholipase domain containing 1 (PNPLA1); adaptor-related protein complex 4, beta 1 subunit (AP4B1); tripartite motif-containing 45 (TRIM45) and cell division cycle associated 2 (CDCA2) genes, respectively. Furthermore, a list of 41 candidate genes was composed based on their proximity to significant markers (within a distance of ca. 1 Mb) and functional involvement in processes potentially underlying BLV-induced pathogenesis. In conclusion, it was demonstrated that host response to BLV infection involves nine sub-regions of the cattle genome (represented by 9 SNP markers), containing many genes which, based on the literature, could be involved to enzootic bovine leukemia progression. New group of promising candidate genes associated with the host response to BLV infection were identified and could therefore be a target for future studies. The functions of candidate genes surrounding significant SNP markers imply that there is no single regulatory process that is solely targeted by BLV infection, but rather the network of interrelated pathways is deregulated, leading to the disruption of the control of B-cell proliferation and programmed cell death.

MET: a new promising biomarker in non-small-cell lung carcinoma

Non-small-cell lung cancer (NSCLC) leads cancer-related deaths worldwide. Mutations in the kinase domain of the EGFR gene provide sensitivity to tyrosine kinase inhibitors (TKI) drugs. TKI show initial response rates over 75% in mutant EGFR-NSCLC patients, although most of these patients acquire resistance to EGFR inhibitors after therapy. EGFR-TKI resistance mechanisms include amplification in MET and its ligand, and also MET mutations. MET signaling dysregulation has been involved in tumor cell growth, survival, migration and invasion, angiogenesis and activation of several pathways, therefore representing an attractive target for anticancer drug development. In this review, we will discuss MET-related mechanisms of EGFR-TKI resistance in NSCLC, as well as the main drugs targeted to inhibit MET pathway.

Coordinated messenger RNA/microRNA changes in fibroblasts of patients with major depression

BACKGROUND

Peripheral biomarkers for major psychiatric disorders have been an elusive target for the last half a century. Dermal fibroblasts are a simple, relevant, and much underutilized model for studying molecular processes of patients with affective disorders, as they share considerable similarity of signal transduction with neuronal tissue.

METHODS

Cultured dermal fibroblast samples from patients with major depressive disorder (MDD) and matched control subjects (n = 16 pairs, 32 samples) were assayed for genome-wide messenger RNA (mRNA) expression using microarrays. In addition, a simultaneous quantitative polymerase chain reaction-based assessment of >1000 microRNA (miRNA) species was performed. Finally, to test the relationship between the mRNA-miRNA expression changes, the two datasets were correlated with each other.

RESULTS

Our data revealed that MDD fibroblasts, when compared with matched control subjects, showed a strong mRNA gene expression pattern change in multiple molecular pathways, including cell-to-cell communication, innate/adaptive immunity, and cell proliferation. Furthermore, the same patient fibroblasts showed altered expression of a distinct panel of 38 miRNAs, which putatively targeted many of the differentially expressed mRNAs. The miRNA-mRNA expression changes appeared to be functionally connected, as the majority of the miRNA and mRNA changes were in the opposite direction.

CONCLUSIONS

Our data suggest that combined miRNA-mRNA assessments are informative about the disease process and that analyses of dermal fibroblasts might lead to the discovery of promising peripheral biomarkers of MDD that could be potentially used to aid the diagnosis and allow mechanistic testing of disturbed molecular pathways.

Chronic lymphocytic leukemia nurse-like cells express hepatocyte growth factor receptor (c-MET) and indoleamine 2,3-dioxygenase and display features of immunosuppressive type 2 skewed macrophages

Hepatocyte growth factor, produced by stromal and follicular dendritic cells, and present at high concentrations in the sera of patients with chronic lymphocytic leukemia, prolongs the survival of leukemic B cells by interacting with their receptor, c-MET. It is, however, unknown whether hepatocyte growth factor influences microenvironmental cells, such as nurse-like cells, which deliver survival signals to the leukemic clone. We evaluated the expression of c-MET on nurse-like cells and monocytes from patients with chronic lymphocytic leukemia and searched for phenotypic/functional features supposed to be influenced by the hepatocyte growth factor/c-MET interaction. c-MET is expressed at high levels on nurse-like cells and at significantly higher levels than normal on monocytes from patients. Moreover, the hepatocyte growth factor/c-MET interaction activates STAT3(TYR705) phosphorylation in nurse-like cells. Indoleamine 2,3-dioxygenase, an enzyme modulating T-cell proliferation and induced on normal monocytes after hepatocyte growth factor treatment, was detected together with interleukin-10 on nurse-like cells, and on freshly-prepared patients' monocytes. Immunohistochemical/immunostaining analyses demonstrated the presence of c-MET(+) and indoleamine 2,3-dioxygenase(+) cells in lymph node biopsies, co-expressed with CD68 and vimentin. Furthermore nurse-like cells and chronic lymphocytic monocytes significantly inhibited T-cell proliferation, prevented by anti-transforming growth factor beta and interleukin-10 antibodies and indoleamine 2,3-dioxygenase inhibitors, and supported CD4(+)CD25(high+)/FOXP3(+) T regulatory cell expansion. We suggest that nurse-like cells display features of immunosuppressive type 2 macrophages: higher hepatocyte growth factor levels, produced by leukemic or other microenvironmental surrounding cells, may cooperate to induce M2 polarization. Hepatocyte growth factor may thus have a dual pathophysiological role: directly through enhancement of survival of the leukemic clone and indirectly by favoring T-cell immunosuppression.

Cytokines as regulators of proliferation and survival of healthy and malignant peripheral B cells

Adaptive immunity depends on the production and maintenance of a pool of mature peripheral lymphocytes throughout life. The signals regulating the survival of mature splenic B cells have become a major focus in recent studies of B cell immunology. Lasting B cell persistence in the periphery is dependent on survival signals that are transduced by cell surface receptors. Cytokines have been shown to play a critical role in maintaining lymphocyte homeostasis. This review focuses on the role of cytokines and their receptors in the regulation of peripheral B cell survival, with an emphasis on those that have received relatively less attention in the literature.

α-Syntrophin is required for the hepatocyte growth factor-induced migration of cultured myoblasts

Syntrophins are adaptor proteins that link intracellular signaling molecules to the dystrophin based scaffold. In this study, we investigated the function of syntrophins in cell migration, one of the early steps in myogenic differentiation and in regeneration of adult muscle. Hepatocyte growth factor (HGF) stimulates migration and lamellipodia formation in cultured C2 myoblasts. In the migrating cells, syntrophin concentrated in the rear-lateral region of the cell, opposite of the lamellipodia, instead of being diffusely present throughout the cytoplasm of non-migrating cells. When the expression of α-syntrophin, the major syntrophin isoform of skeletal muscle, was reduced by transfection with the α-syntrophin-specific siRNA, HGF stimulation of lamellipodia formation was prevented. Likewise, migration of myoblasts from α-syntrophin knockout mice could not be stimulated by HGF. However, HGF-induced migration was restored in myoblasts isolated from a transgenic mouse expressing α-syntrophin only in muscle cells. Treatment of C2 myoblasts with inhibitors of PI3-kinase not only reduced the rate of cell migration, but also impaired the accumulation of syntrophins in the rear-lateral region of the migrating cells. Phosphorylation of Akt was reduced in the α-syntrophin siRNA-treated C2 cells. These results suggest that α-syntrophin is required for HGF-induced migration of myoblasts and for proper PI3-kinase/Akt signaling.

Coexpression of activated c-Met and death receptor 5 predicts better survival in colorectal carcinoma

Dysregulated overexpression of hepatocyte growth factor and its receptor, c-Met, has been reported in various cancers, but its role in colorectal carcinoma (CRC) has not been elucidated. Therefore, we investigated the role of phosphorylated Met (p-Met) in Middle Eastern CRC patient samples and cell lines. The p-Met was overexpressed in 80.8% of CRCs and strongly associated with the expression of p-AKT, DR5, and Ki-67 by immunohistochemistry. Coexpression of p-Met and DR5 was seen in 53.1% of CRC cases and was associated with a less aggressive phenotype, characterized by a histological subtype of adenocarcinomas, well-differentiated tumors, and was an independent prognostic marker for better overall survival. PHA665752, a selective p-Met inhibitor, induced apoptosis in CRC cells via inactivation of c-Met and AKT. PHA665752 treatment also caused increased expression of DR5 via generation of reactive oxygen species, and combination treatment with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and PHA665752 induced significant apoptosis. In vivo, cotreatment of a CRC xenograft with PHA665752 and TRAIL significantly reduced tumor volume and weight. These data demonstrate a significant correlation between p-Met and DR5 in patients with CRC. Furthermore, inhibition of p-Met signaling by PHA665752 in combination with TRAIL significantly inhibited cell growth and induced apoptosis in CRC cell lines, suggesting that this may have significant clinical implications as a therapeutic target in the treatment of CRC.

Embryonal carcinoma cell induction of miRNA and mRNA changes in co-cultured prostate stromal fibromuscular cells

The prostate stromal mesenchyme controls organ-specific development. In cancer, the stromal compartment shows altered gene expression compared to non-cancer. The lineage relationship between cancer-associated stromal cells and normal tissue stromal cells is not known. Nor is the cause underlying the expression difference. Previously, the embryonal carcinoma (EC) cell line, NCCIT, was used by us to study the stromal induction property. In the current study, stromal cells from non-cancer (NP) and cancer (CP) were isolated from tissue specimens and co-cultured with NCCIT cells in a trans-well format to preclude heterotypic cell contact. After 3 days, the stromal cells were analyzed by gene arrays for microRNA (miRNA) and mRNA expression. In co-culture, NCCIT cells were found to alter the miRNA and mRNA expression of NP stromal cells to one like that of CP stromal cells. In contrast, NCCIT had no significant effect on the gene expression of CP stromal cells. We conclude that the gene expression changes in stromal cells can be induced by diffusible factors synthesized by EC cells, and suggest that cancer-associated stromal cells represent a more primitive or less differentiated stromal cell type.

Inhibition of c-MET is a potential therapeutic strategy for treatment of diffuse large B-cell lymphoma

Hepatocyte growth factor/c-MET has emerged as a potential therapeutic target for several cancers; however, its role in diffuse large B-cell lymphoma (DLBCL) has not been fully elucidated. In this study, we first investigated the role of c-Met in a large series of DLBCL tissues in a tissue microarray format. We then followed this with in vitro studies on DLBCL cell lines using either pharmacological inhibitors of c-Met or siRNA knockdown strategy. c-Met was found to be overexpressed in 73.2% of patients (186/254) and was significantly associated with overexpression of p-AKT (P=0.0274), p-GSK3 (P=0.0047) and Ki-67 (P=0.0012). Interestingly, c-Met overexpression was significantly more common in the germinal center subtype of DLBCL, as compared with activated B cell subtype (P=0.0002). Overexpression of c-Met in DLBCL was significantly associated with better survival (P=0.0028) and remained significant in multivariate analysis with international prognostic index, thereby confirming c-Met as independent prognostic marker for better outcome in DLBCL. In vitro pharmacological c-Met inhibition and siRNA targeted against c-Met triggered caspase-dependent apoptosis. These findings provide evidence that c-Met is an independent prognostic marker for better outcome in Middle Eastern DLBCL. This data also enlightens the fact that c-Met through AKT kinase has a critical role in carcinogenesis of DLBCL, and strongly suggest that targeting c-Met may have therapeutic value in treatment of DLBCL.

Inhibition of fatty acid synthase suppresses c-Met receptor kinase and induces apoptosis in diffuse large B-cell lymphoma

Fatty acid synthase (FASN), the enzyme responsible for de novo synthesis of fatty acids, has emerged as a potential therapeutic target for several cancers; however, its role in diffuse large B-cell lymphoma (DLBCL) has not been fully elucidated. In this study, we investigated the role of FASN in a large series of DLBCL tissues in a tissue microarray (TMA) format followed by in vitro studies using DLBCL cell lines. FASN was found to be expressed in 62.6% DLBCL samples and was seen in highly proliferative tumors, manifested by high Ki67 (P < 0.0001). Significant association was found between tumors expressing high FASN and c-Met tyrosine kinase (P < 0.0002), as well as p-AKT (P = 0.0309). In vitro, pharmacological FASN inhibition and small interference RNA (siRNA) targeted against FASN triggered caspase-dependent apoptosis and suppressed expression of c-Met kinase in DLBCL cell lines, which further highlighted the molecular link between FASN and c-Met kinase. Finally, simultaneous targeting of FASN and c-Met with specific chemical inhibitors induced a synergistically stimulated apoptotic response in DLBCL cell lines. These findings provide evidence that FASN, via c-Met tyrosine kinase, plays a critical role in the carcinogenesis of DLBCL and strongly suggest that targeting FASN may have therapeutic value in treatment of DLBCL.

Inhibition of the met receptor tyrosine kinase signaling enhances the chemosensitivity of glioma cell lines to CDDP through activation of p38 MAPK pathway

The Met receptor tyrosine kinase is known to be overexpressed in many solid tumors and plays a crucial role in tumor invasive growth and metastasis. In this study, we showed that hepatocyte growth factor-induced Met activation as well as Met-dependent downstream signaling of AKT and p44/42 mitogen-activated protein kinase (MAPK) could be efficiently blocked by TAT-coupled carboxyl-terminal tail peptide of Met receptor (TCTP), and inactivation of Met signaling significantly enhanced the sensitivity of T98G and U251 glioma cells to cis-diaminedichloroplatinum (CDDP, cisplatin). However, neither phosphoinositide 3-kinase/AKT inhibitor LY294002 nor p44/42 MAPK inhibitor PD98059 alone or combined could imitate the effect of TCTP on chemosensitivity enhancement of T98G cells to CDDP, indicating that Met-dependent inactivation of AKT and p44/42 MAPK signaling was not the main cause for the increased chemosensitivity to CDDP. Further studies revealed that TCTP significantly activated p38 MAPK in T98G and U251 cell lines. Activation of p38 MAPK by sorbitol pretreatment resembled the sensitization effects, whereas inhibition of p38 MAPK activation by its inhibitor SB202190 counteracted the sensitization effects induced by TCTP. Therefore, p38 MAPK activation was one of the major causes for the increased chemosensitivity to CDDP induced by Met inactivation. Taken together, the study indicated that Met receptor played an important role in regulating cell response to chemotherapy and suggested that inhibition of Met signaling could be used in combination with other chemotherapeutic regimens in treatment of tumor patients.

Knockdown of SMYD3 by RNA interference down-regulates c-Met expression and inhibits cells migration and invasion induced by HGF

We previously reported that over-expression of SMYD3, a histone H3-K4 specific di- and tri-methyltransferase, plays a key role in cell viability, adhesion, migration and invasion. In this study, we investigated the mechanisms underlying these phenomena and found that knocking down SMYD3 expression in tumor cells significantly reduced the biological function of HGF and inhibited carcinoma cells migration and invasion. Due to the fact that the proto-oncogene c-Met encodes the high-affinity receptor for HGF, and the HGF-c-Met signaling plays a critical role in the tumor genesis, we further identified the partial correlation between SMYD3 and c-Met. The results showed that high expression of c-Met accompanied with over-expression of SMYD3. Silencing SMYD3 expression in tumor cells by specific shRNAs down-regulated c-Met gene transcription, while over-expressing SMYD3 induced c-Met transcription. Moreover, we demonstrated here that two SMYD3 binding sites within the c-Met core promoter region were significant in the transactivation of c-Met. The present findings provide significant insights into the epigenetic regulatory mechanisms of oncogene c-Met expression, and develop the strategies that may inhibit the progression of cancer migration and invasion.

Frzb, a secreted Wnt antagonist, decreases growth and invasiveness of fibrosarcoma cells associated with inhibition of Met signaling

Soft tissue sarcomas (STS) have a strong propensity for aggressive growth and metastasis. We showed that the secreted Wnt antagonist Frzb exhibited potent antitumor activity against prostate cancer, an epithelial type of malignancy. In this study, we further showed the antitumor efficacy of Frzb in STS, a mesenchymal group of cancer. Frzb transfection of HT1080 (fibrosarcoma) and SW872 (liposarcoma) cell lines and their conditioned media resulted in a significant reduction in cellular invasion, motility, and colony formation in soft agar compared with vector control-transfected cells. In a xenograft mouse model, Frzb dramatically suppressed tumor growth of HT1080 cells in nude mice. In a tail-vein injection metastatic model, Frzb-transfected HT1080 cells formed fewer and smaller lung nodules than vector control cells. In addition, we identified new mechanisms for Frzb antitumor activities. Frzb reduced c-Met expression and inhibited Met-mediated signaling, associated with up-regulation of epithelial markers (i.e., keratins 8 and 18) and down-regulation of mesenchymal markers (i.e., vimentin, N-cadherin, fibronectin, Slug, and Twist). Similar to Frzb, silencing of c-Met by short hairpin RNA or using a dominant-negative LRP5 receptor also suppressed Met signaling, leading to reduced cellular motility, invasion, and in vivo tumor growth. Given recent studies indicating an important role of c-Met in sarcoma development and progression, our data showed that Frzb expression was significantly inversely correlated with Met expression in both STS cell lines and tissues. These results suggested the usefulness of Frzb in modulating Met signaling as a new treatment strategy for STS.

Clinical correlations and prognostic relevance of HGF, VEGF AND FGF expression in Brazilian patients with non-Hodgkin lymphoma

The aims of this study were to correlate HGF, VEGF and FGF serum levels and microvessel density (MVD) with cell origin, biological behavior, tumor load and prognosis in NHL. Eighty-seven consecutive previously untreated NHL patients had serum samples collected; 37 (42%) of them also had serum follow-up samples; the control group was composed of 10 healthy blood donors. Cytokine serum levels were determined by ELISA, and MVD was measured by CD34 staining in paraffin blocks. HGF mean serum level was significantly higher in both early and advanced NHL stages when compared with the control group. HGF was also significantly higher in aggressive and indolent NHL when compared with the control group. Also, mean serum level of HGF in aggressive NHL was significantly higher than in indolent NHL. Regarding International Prognostic Index (IPI), HGF mean serum level at diagnosis was significantly higher for patients with IPI >2 when compared to IPI <or=2. Sequential analyses of HGF, VEGF and FGF serum levels in NHL showed that serum HGF and VEGF levels decreased significantly after 6 months of treatment completion. Our findings suggest that HGF serum level is associated with tumor load and aggressiveness, and response to treatment results in a decrease in HGF serum levels in NHL patients.

Hepatocyte growth factor receptor c-MET is associated with FAS and when activated enhances drug-induced apoptosis in pediatric B acute lymphoblastic leukemia with TEL-AML1 translocation

Expression of c-MET, the HGF (hepatocyte growth factor) tyrosine kinase receptor, was investigated in pediatric B-acute lymphoblastic leukemia (ALL) patients. c-MET was found to be expressed in normal B cells and in B-ALL patients with the t(12;21) TEL-AML1 translocation, but it is not expressed in the most part of B-ALL without the t(12;21). We also found that c-MET, related to proliferation and protection from apoptosis, is associated with the pro-apoptotic protein FAS in TEL-AML1 B-ALL cells and in normal B lymphocytes. The possible role of this protein complex in drug-induced apoptosis was thus investigated in REH TEL-AML1 B-ALL cell line. REH cells prestimulated with HGF and treated with doxorubicin had shown a higher apoptotic rate than non-HGF-prestimulated ones (p = 0.03). REH cells stimulated with IL-3 and treated with doxorubicin did not undergo apoptosis more than nonstimulated cells, demonstrating that increased proliferation in itself is not directly related to the higher apoptotic sensitivity observed with HGF stimulation. These results indicate that c-MET activation enhances specifically FAS-mediated apoptosis in TEL-AML1 ALL cells and, considering that the c-MET/FAS complex is present only in normal B lymphocytes and in TEL-AML1 leukemias, this implies that it may have an important contribution in cellular homeostasis and in high sensitivity of TEL-AML1 ALL to chemotherapeutic regimens.

Semaphorin signaling in vascular and tumor biology

The neuropilins were originally characterized as cell membrane receptors that bind axon guidance factors belonging to the class-3 semaphorin subfamily. To transduce semaphorin signals, they form complexes with members of the plexin receptor family in which neuropilins serve as the ligand binding components and the plexins as the signal transducing components. The neuropilins were subsequently found to double as receptors for specific heparin binding splice forms of vascular endothelial growth factor (VEGF), and to be expressed on endothelial cells. This finding suggested that semaphorins may function as modulators of angiogenesis. It was recently found that several types of semaphorins such as semaphorin-3F function as inhibitors of angiogenesis while others, most notably semaphorin-4D, function as angiogenic factors. Furthermore, semaphorins such as semaphorin-3F and semaphorin-3B have been characterized as tumor suppressors and have been found to exert direct effects upon tumor cells. In this chapter we cover recent developments in this rapidly developing field of research.

Up-regulation of MET Expression by α-Melanocyte-stimulating Hormone and MITF Allows Hepatocyte Growth Factor to Protect Melanocytes and Melanoma Cells from Apoptosis

The MET proto-oncogene encodes for the hepatocyte growth factor (HGF) receptor, a plasma membrane tyrosine kinase that is involved in melanocyte growth and melanoma development. In mouse melanoma cells, Met expression is increased by alphaMSH via the activation of the cAMP pathway. However, the mechanism by which cAMP regulates MET and the biological consequences of this increase were not known. In the present report, we show that alphaMSH regulates MET expression in both human melanocytes and mouse melanoma cells through a transcriptional mechanism that requires MITF. Furthermore, the adenovirus driven expression of MITF is sufficient to increase MET in melanoma cells. Functional analysis of the MET promoter allows us to identify an E-box motif conserved in both human and mouse promoter that mediates the effect of MITF. Interestingly, up-regulation of MET expression by cAMP leads to an exacerbated HGF signaling and allows HGF to protect melanocytes and melanoma cells from apoptosis. Thus, physiological stimuli or pathological events that would induce MITF expression may lead to increased MET expression thereby favoring melanoma survival. These observations strengthen the roles of MITF and MET in melanoma development.

Effect of hepatocyte growth factor on long term hematopoiesis of human progenitor cells in transgenic-sever combined immunodeficiency mice

Hepatocyte growth factor (HGF), which was originally isolated as a liver generating factor, enhances hematopoiesis. To study the effect of HGF on hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs), we generated severe combined immunodeficiency (SCID) mice producing human (h) HGF and/or stem cell factor (SCF) by transferring the relevant genes to fertilized eggs, and then transplanted hematopoietic progenitors from human cord blood into the transgenic (Tg) SCID mice. Six months after transplantation, a significantly larger number of human cells were found in the Tg SCID mice than in non-Tg controls. Characteristically, the recipient SCID mice producing h HGF (HGF-SCID) had a significantly increased number of h CD41+ cells, whereas the SCF-SCID recipients had more CD11b+ cells. Significantly large numbers of CD34+ progenitors were found in the SCID mice transferred with both h HGF and h SCF genes (HGF/SCF-SCID) when compared with HGF-SCID or SCF-SCID mice. These results imply that HGF supports the differentiation of progenitors in megakaryocyte lineage, whereas SCF supports that in myeloid lineage. The results also imply that HGF acts on HSCs/HPCs as a synergistic proliferative factor combined with SCF. We have demonstrated the advantage of the human cytokine-producing animal in the maintenance of human HSCs.

Activation of Wnt signaling in the intestinal mucosa of Apc +/min mice does not cause overexpression of the receptor tyrosine kinase Met

The receptor tyrosine kinase MET is overexpressed in human colorectal adenomas and carcinomas, suggesting an instrumental role for MET signaling in the onset and progression of colorectal cancer. To corroborate this role, animal models are needed. To study the expression of Met in the normal and neoplastic mouse intestine, we generated an Armenian hamster monoclonal antibody against mouse Met. By using this antibody in immunohistochemical studies, we observed strong Met expression in fetal mouse intestinal epithelial cells. In contrast, in the intestines of adult mice, Met expression was very low whereas the protein was undetectable on the neoplastic epithelium of intestinal adenomas in Apc+/min mice. By immunoblotting, we were also unable to detect Met in intestinal adenomas, whereas Met mRNA levels in microdissected adenomas were very low. The absence of detectable Met protein expression in adenomas of Apc+/min mice contrasts sharply with the vast overexpression of the protein in adenomas of humans with familial adenomatous polyposis or sporadic colorectal carcinomas. Our results imply that deregulation of Wnt signaling in mouse--unlike in human--intestinal epithelium does not result in Met overexpression. Our findings thus reveal important interspecies differences in the regulation of Met expression during intestinal tumorigenesis.

Effects of adenoviral-mediated gene transduction of NK4 on proliferation, movement, and invasion of human colonic LS174T cancer cells in vitro

AIM: To investigate the inhibitory effects of a recombinant adenovirus vector that expresses NK4, a truncated form of human hepatocyte growth factor (HGF), on human colonic adenocarcinoma cells in vitro to establish a basis for future NK4 gene cancer therapy.

METHODS: Cells from the LS174T human colonic adenocarcinoma cell line were infected with recombinant adenovirus rvAdCMV/NK4 and the effects of the manipulation on tumor cell proliferation, scatter, migration, and basement membrane invasion were assessed. Cells infected with a recombinant adenovirus vector (Ad-LacZ) expressing β-galactosidase served as the controls.

RESULTS: We found that rvAdCMV/NK4 expression attenuated HGF-induced tumor cell scatter, migration, and basement membrane invasion (P < 0.05), but did not inhibit tumor cell proliferation.

CONCLUSION: HGF-induced LS174T tumor cell scatter, migration, and invasion can be antagonized by the recombinant NK4-expressing adenovirus.

Microarray analysis of BeWo and JEG3 trophoblast cell lines: identification of differentially expressed transcripts

Trophoblast cell lines are important research tools used as a surrogate for primary trophoblast cells in the study of placental function. Because the cellular origins of transformed trophoblasts are likely to be diverse, it would be of value to understand the unique and shared phenotypes of the cells on a global scale. We have compared two widely used cell lines, BeWo and JEG3, by microarray analysis in order to identify differentially expressed genes. Results indicated that approximately 2700 genes were differentially expressed between the cell lines, with principal differences observed in the biological processes of response to stress, cell adhesion, signal transduction, and protein and nucleobase metabolisms. These data suggest that BeWo and JEG3 cell lines, and perhaps other trophoblast cell lines, are sufficiently dissimilar from each other such that they will be differentially suited for specific experimental paradigms.

Molecular pathology of odontogenic tumors

Odontogenic tumors are lesions derived from the elements of the tooth-forming apparatus and are found exclusively within the jawbones. This review represents a contemporary outline of our current understanding of the molecular and genetic alterations associated with the development and progression of odontogenic tumors, including oncogenes, tumor-suppressor genes, oncoviruses, growth factors, telomerase, cell cycle regulators, apoptosis-related factors, regulators of tooth development, hard tissue-related proteins, cell adhesion molecules, matrix-degrading proteinases, angiogenic factors, and osteolytic cytokines. It is hoped that better understanding of related molecular mechanisms will help to predict the course of odontogenic tumors and lead to the development of new therapeutic concepts for their management.

Functional analysis of HGF/MET signaling and aberrant HGF-activator expression in diffuse large B-cell lymphoma

Inappropriate activation of MET, the receptor tyrosine kinase for hepatocyte growth factor (HGF), has been implicated in tumorigenesis. Although we have previously shown that HGF/MET signaling controls survival and proliferation of multiple myeloma (MM), its role in the pathogenesis of other B-cell malignancies has remained largely unexplored. Here, we have examined a panel of 110 B-cell malignancies for MET expression, which, apart from MM (48%), was found to be largely confined to diffuse large B-cell lymphomas (DLBCLs) (30%). No amplification of the MET gene was found; however, mutational analysis revealed 2 germ-line missense mutations: R1166Q in the tyrosine kinase domain in 1 patient, and R988C in the juxtamembrane domain in 4 patients. The R988C mutation has recently been shown to enhance tumorigenesis. In MET-positive DLBCL cells, HGF induces MEK-dependent activation of ERK and PI3K-dependent phosphorylation of PKB, GSK3, and FOXO3a. Furthermore, HGF induces PI3K-dependent α4β1 integrin-mediated adhesion to VCAM-1 and fibronectin. Within the tumor microenvironment of DLBCL, HGF is provided by macrophages, whereas DLBCL cells themselves produce the serine protease HGF activator (HGFA), which autocatalyzes HGF activation. Taken together, these data indicate that HGF/MET signaling, and secretion of HGFA by DLBCL cells, contributes to lymphomagenesis in DLBCL. (Blood. 2006;107:760-768)

A recombinant single-chain IL-7/HGFbeta hybrid cytokine induces juxtacrine interactions of the IL-7 and HGF (c-Met) receptors and stimulates the proliferation of CFU-S12, CLPs, and pre-pro-B cells

A novel recombinant interleukin-7/hepatocyte growth factor beta-chain (IL-7/HGFbeta) hybrid cytokine was constructed as a single chain (sc) composed of IL-7 and HGFbeta connected by a flexible linker. Unlike recombinant (r) IL-7, which stimulated pro-B cells and pre-B cells only, scIL-7/HGFbeta stimulated the proliferation of pre-pro-B cells, common lymphoid progenitors (CLPs), and colony-forming unit (CFU)-S12 in cultures of IL-7-/- mouse BM cells. When injected in vivo, 3- to 4-fold more splenic B-lineage cells appeared in recipients of bone marrow (BM) cells from the scIL-7/HGFbeta-stimulated cultures than from rIL-7-stimulated cultures. Moreover, on a per-cell basis, scIL-7/HGFbeta culture-generated cells produced 16- to 20-fold more BM and splenic B-lineage cells than did normal BM cells. Antibody blocking, receptor phosphorylation, and confocal microscopy demonstrated that scIL-7/HGFbeta signals though both the IL-7 and HGF (c-Met) receptors, which form IL-7R/c-Met complexes on the surface of CLPs and pre-pro-B cells. In addition, the IL-7Ralpha chain, gammac chain, and c-Met were coisolated from purified CLPs and pre-pro-B cells on scIL-7/HGFbeta affinity gels, indicating that they are major components of the IL-7/HGFbeta receptor. Hence, the present results demonstrate that the IL-7/HGFbeta hybrid cytokine efficiently and selectively stimulates the most primitive B-lineage precursors in BM by inducing juxtacrine interactions between the IL-7 and c-Met receptors.

Follicular dendritic cells catalyze hepatocyte growth factor (HGF) activation in the germinal center microenvironment by secreting the serine protease HGF activator

Ag-specific B cell differentiation, the process that gives rise to plasma cells and memory B cells, involves the formation of germinal centers (GC). Within the GC microenvironment, multiple steps of B cell proliferation, selection, and maturation take place, which are controlled by the BCR in concert with cytokines and contact-dependent signals from follicular dendritic cells (FDCs) and T cells. Signaling by the multifunctional cytokine hepatocyte growth factor (HGF) and its receptor MET has been shown to induce integrin-mediated adhesion of B cells to VCAM-1, which is expressed by FDCs. In the present study we have examined the expression of regulatory components of the HGF/MET pathway, including HGF activator (HGFA), within the secondary lymphoid organ microenvironment. We show that MET is expressed by both centroblasts and plasma cells, and that HGFA is expressed by plasma cells. Because we have shown that HGF is a potent growth and survival factor for malignant plasma cells, HGF may also serve as a survival factor for normal plasma cells. Furthermore, we demonstrate that FDCs are the major source for HGF and its activator within the GC microenvironment. Both HGF and HGFA are expressed by FDCs in the GC dark zone (CD21high/CD23low), but not in the light zone (CD21high/CD23high). These findings suggest that HGF and HGFA provided by dark zone FDCs help to regulate the proliferation, survival, and/or adhesion of MET-positive centroblasts.

C/EBPbeta contributes to hepatocyte growth factor-induced replication of rodent hepatocytes

BACKGROUND/AIMS

Hepatocyte replication can be induced in vivo by hepatocyte growth factor (HGF), which might be used for gene therapy or to promote liver regeneration. However, the biochemical steps critical for this process are not clear. C/EBPbeta and C/EBPalpha are liver-enriched transcription factors that induce and inhibit hepatocyte replication, respectively. Because of their role in hepatocyte replication, this study examined the effect of HGF upon C/EBP proteins in vivo.

METHODS

Rats were treated with HGF, and the effect upon C/EBPs was evaluated in liver extracts. Normal or C/EBPbeta-deficient mice were treated with HGF, and the effect upon hepatocyte replication was determined.

RESULTS

HGF had no effect in rat liver upon C/EBPalpha or C/EBPbeta mRNA, nuclear protein, or nuclear DNA binding activity. However, HGF increased phosphorylated p90-RSK and ERK to 18- and 3-fold normal, respectively. These kinases phosphorylate C/EBPbeta and increase its transcriptional activity. The percentage of hepatocytes that replicated in C/EBPbeta-deficient mice after HGF administration was only 1.1%, which was lower than the value of 6.6% for hepatocytes from HGF-treated normal mice (P=0.005).

CONCLUSIONS

C/EBPbeta contributes to the induction of hepatocyte replication in response to HGF in rodents, which is likely due to post-translational modifications.

The SPRY domain-containing SOCS box protein 1 (SSB-1) interacts with MET and enhances the hepatocyte growth factor-induced Erk-Elk-1-serum response element pathway

The suppressor of cytokine signaling (SOCS) protein family includes a SPRY (repeats in splA and RyR) domain-containing SOCS box protein (SSB) subfamily, which consists of four members, SSB-1, SSB-2, SSB-3, and SSB-4. These proteins contain a central SPRY domain and a C-terminal SOCS box. Although some of the SOCS protein subfamilies function as adaptors for a large family of ubiquitin-protein isopeptide ligases to regulate certain signaling pathways, the function of the SSB subfamily remains to be determined. In our previous studies, we have found that two SPRY domain-containing proteins, RanBP9 and RanBP10, interact with MET through the SPRY domain. In the present study, we explored the function of SSB proteins in the regulation of the hepatocyte growth factor (HGF)-MET signaling. Our results showed that all four SSB proteins also interacted with the MET. The MET interaction with SSB-1 was further investigated. We demonstrated that SSB-1 bound to MET tyrosine kinase domain through its SPRY domain. MET interacted with SSB-1 in both the absence and the presence of HGF, but HGF treatment resulted in the recruitment of more SSB-1 by MET. We showed that overexpression of SSB-1 but not other SSB proteins enhanced the HGF-induced serum response element (SRE)-luciferase activity. Overexpression of SSB-1 exhibited no effect on the basal level or epidermal growth factor-induced SRE-luciferase activity. SSB-1 also enhanced HGF-induced Erk phosphorylation. Suppression of SSB-1 by the RNA interference method down-regulated HGF-induced SRE-luciferase activity and decreased Elk-1 activation. These results suggest that SSB-1 may play an important role in enhancing the HGF-induced Erk-Elk-1-SRE pathway. Furthermore, we demonstrated that in response to HGF stimulation, the SSB-1 protein became phosphorylated at tyrosine residue 31. The phosphorylated SSB-1 protein bound to p120Ras-GTPase-activating protein (GAP) but did not promote the degradation of p120RasGAP, indicating that enhanced HGF-MET signaling by overexpression of SSB-1 was not dependent on p120RasGAP degradation.

Involvement of stromal proteoglycans in tumour progression

Glycosaminoglycans (GAGs) and proteoglycans (PGs) belong to a class of extracellular macromolecules necessary for the growth of any multicellular structures, including tumours. Transformed cells induce stromal reaction either per se or by activation of the mesenchymal cells. Tumour stroma contains several chondroitin sulphate and heparan sulphate proteoglycans. These proteoglycans and their glycosaminoglycan chains modify cell behaviour by interacting with different molecules such as growth factors, cytokines, chemokines, proteinases and their inhibitors. This review describes the main proteoglycans of tumour stoma and discusses their implication in the regulation of the activity of extracellular proteins and peptides.

Multiple myeloma cells catalyze hepatocyte growth factor (HGF) activation by secreting the serine protease HGF-activator

Multiple myeloma (MM) is a common hematologic neoplasm consisting of malignant plasma cells, which expand in the bone marrow. A potential key signal in the evolution of MM is hepatocyte growth factor (HGF), which acts as a potent paracrine and/or autocrine growth factor and survival factor for MM cells. Proteolytic conversion of HGF into its active form is a critical limiting step in HGF/MET signaling. Here, we show that malignant MM plasma cells convert HGF into its active form and secrete HGF-activator (HGFA), a serine protease specific for HGF activation. By using serine protease inhibitors and neutralizing antibodies, we demonstrate that HGFA produced by the MM cells is responsible for their ability to catalyze HGF activation. We, therefore, suggest that autocatalyzation of HGF conversion by MM cells is an important step in HGF/MET-induced myeloma growth and survival, which may have implications for the management of this incurable form of cancer. (Blood. 2004;104:2172-2175)

The fibroblast: sentinel cell and local immune modulator in tumor tissue

Development and progression of epithelial malignancies are frequently accompanied by complex phenotypic alterations of resident tissue fibroblasts. Some of these changes, such as myofibroblastic differentiation and an oncofetal extracellular matrix (ECM) expression profile, are also implicated in inflammation and tissue repair. Studies over the past decade revealed the relevance of reciprocal interactions between tumor cells and tumor-associated host fibroblasts (TAF) in the malignant process. In many tumors, a considerable fraction of the inflammatory infiltrate is located within the fibroblast- and ECM-rich stromal compartment. However, while fibroblasts are known as "sentinel cells" in various nonneoplastic diseases, where they often regulate the composition and function of recruited leucocytes, they are hardly considered active participants in the inflammatory host response in tumors. This article focuses on the functional impact of TAF on immune cells. The complex network of immune-modulating effects transduced by TAF and TAF-derived factors is highlighted, and recent reports that support the hypothesis that TAF are involved in the inflammatory response and immune suppression in tumors are reviewed. The role of TAF-dependent ECM remodeling and TAF-derived peptide growth factors, cytokines, and chemokines in the immune modulation is stressed and the idea of TAF as an important therapeutic target is emphasized.

Grappling with metastatic risk: bringing molecular imaging of Met expression toward clinical use

The availability of a test to assess the likelihood that a given tumor will invade or metastasize would be a useful development in clinical oncology. We propose that multimodality imaging of tumor expression of Met could serve as a prototype for metastatic risk stratification (MRS). Met, a receptor protein tyrosine kinase, is expressed by most solid tumors, and aberrant expression of Met is associated with poor clinical prognosis. We summarize the current status and predict the future direction of research in four areas of molecular imaging and cancer therapy that exploit Met.

Tissue expression, protease specificity, and Kunitz domain functions of hepatocyte growth factor activator inhibitor-1B (HAI-1B), a new splice variant of HAI-1

Hepatocyte growth factor activator inhibitor-1 (HAI-1) is an integral membrane protein expressed on epithelial cells and contains two extracellular Kunitz domains (N-terminal KD1 and C-terminal KD2) known to inhibit trypsin-like serine proteases. In tumorigenesis and tissue regeneration, HAI-1 regulates the hepatocyte growth factor (HGF)/c-Met pathway by inhibiting the activity of HGF activator (HGFA) and matriptase, two serine proteases that convert pro-HGF into its biologically active form. By screening a placental cDNA library, we discovered a new splice variant of HAI-1 designated HAI-1B that contains an extra 16 amino acids adjacent to the C terminus of KD1. To investigate possible consequences on Kunitz domain function, a soluble form of HAI-1B (sHAI-1B) comprising the entire extracellular domain was produced. First, we found that sHAI-1B displayed remarkable enzyme specificity by potently inhibiting only HGFA (IC50 = 30.5 nm), matriptase (IC50 = 16.5 nm), and trypsin (IC50 = 2.4 nm) among 16 serine proteases examined, including plasminogen activators (urokinase- and tissue-type plasminogen activators), coagulation enzymes thrombin, factors VIIa, Xa, XIa, and XIIa, and activated protein C. Relatively weak inhibition was found for plasmin (IC50 = 399 nm) and plasma kallikrein (IC50 = 686 nm). Second, the functions of the KD1 and KD2 domains in sHAI-1B were investigated using P1 residue-directed mutagenesis to show that inhibition of HGFA, matriptase, trypsin, and plasmin was due to KD1 and not KD2. Furthermore, analysis by reverse transcription-PCR demonstrated that HAI-1B and HAI-1 were co-expressed in normal tissues and various epithelial-derived cancer cell lines. Both isoforms were up-regulated in eight examined ovarian carcinoma specimens, three of which had higher levels of HAI-1B RNA than of HAI-1 RNA. Therefore, previously demonstrated roles of HAI-1 in various physiological and pathological processes likely involve both HAI-1B and HAI-1.

The onecut transcription factor hepatocyte nuclear factor-6 controls B lymphopoiesis in fetal liver

Mouse genetic models have helped to identify transcription factors that are expressed by hemopoietic cells and control their differentiation into lymphoid cells. However, little is known on transcription factors that are involved in this process, but are expressed in nonhemopoietic cells of the microenvironment. We show in this study that inactivation of the gene coding for hepatocyte nuclear factor-6 (HNF-6) in mice led to B lymphopenia in the bone marrow and spleen. This phenotype disappeared shortly after birth when fetal B lymphopoiesis is no longer active, pointing to a defect in fetal liver. Indeed, the number of B cells was decreased in this organ as well. An analysis of B cell developmental markers in fetal liver cells showed that B lymphopoiesis was impaired just beyond the pre-pro B cell stage. Hemopoietic cells from hnf6(-/-) fetal liver could reconstitute the lymphoid system when injected into scid mice. Because parenchymal cells, but not hemopoietic cells, expressed hnf6 in normal liver, we concluded that HNF-6 controls B lymphopoiesis in fetal liver and that HNF-6 exerts this control indirectly by acting in parenchymal cells. The involvement, in the B cell defect of hnf6(-/-) fetuses, of genes known to exert such an indirect control was ruled out by expression analysis, including microarrays, and by in vivo rescue experiments. This work identifies HNF-6 as the first noncell-intrinsic transcription factor known to control B lymphopoiesis specifically in fetal liver.

Beyond Herceptin and Gleevec

Identification of the key role of protein kinases as potential oncoproteins has led to the emergence of a new era of target-directed therapies. Among a variety of novel therapeutic strategies two have shown the most promise and led to a variety of therapeutic agents in clinical development. One approach utilises humanised monoclonal antibodies generated against the extracellular domain of transmembrane protein kinases. The second approach is the generation of small molecule ATP analogues targeting the kinase domain itself. The approval of agents such as Herceptin for the treatment of advanced breast cancer and Gleevec for chronic myelogenous leukemia and gastrointestinal stromal tumours are the first examples of gene-based cancer drugs and represent the first example of a novel strategy in anti-cancer therapy.

Inhibition of hypoxia/reoxygenation-induced oxidative stress in HGF-stimulated antiapoptotic signaling: role of PI3-K and Akt kinase upon rac1

Rac1-regulated reactive oxygen species (ROS) production has been implicated in apoptosis. In contrast, pleiotropic protein kinase Akt protects against apoptosis. However, the pro- and antiapoptotic mechanisms of rac1 and Akt, respectively, and the intersection between these mechanisms are incompletely understood. In a model of oxidative stress and apoptosis induced by hypoxia/reoxygenation (H/R) in primary hepatocytes, activation of the PI3-K Akt axis by the prosurvival hepatocyte growth factor (HGF) inhibited H/R-stimulated rac1 activation and intracellular ROS production, and suppressed apoptosis. Suppression of PI3-K or Akt activity abrogated the inhibitory effect of HGF on rac1 activity and rac1-regulated oxidative stress. Furthermore, constitutive activation of Akt or PI3-K in the absence of HGF was sufficient to phosphorylate rac1, inhibit rac1 activation, and suppress rac1-regulated ROS production. These findings demonstrate that growth factor-stimulated activation of PI3-K-Akt is necessary and sufficient to suppress intracellular oxidative stress and apoptosis by inhibiting activation of pro-apoptotic, prooxidative rac1 GTPase.