Identification of a fibroblast-derived epithelial morphogen as hepatocyte growth factor

Isotropic actomyosin dynamics promote organization of the apical cell cortex in epithelial cells

Apical membrane organization of nonconfluent epithelial cells is driven by a dynamic network of actin and myosin II filaments.

Although cortical actin plays an important role in cellular mechanics and morphogenesis, there is surprisingly little information on cortex organization at the apical surface of cells. In this paper, we characterize organization and dynamics of microvilli (MV) and a previously unappreciated actomyosin network at the apical surface of Madin–Darby canine kidney cells. In contrast to short and static MV in confluent cells, the apical surfaces of nonconfluent epithelial cells (ECs) form highly dynamic protrusions, which are often oriented along the plane of the membrane. These dynamic MV exhibit complex and spatially correlated reorganization, which is dependent on myosin II activity. Surprisingly, myosin II is organized into an extensive network of filaments spanning the entire apical membrane in nonconfluent ECs. Dynamic MV, myosin filaments, and their associated actin filaments form an interconnected, prestressed network. Interestingly, this network regulates lateral mobility of apical membrane probes such as integrins or epidermal growth factor receptors, suggesting that coordinated actomyosin dynamics contributes to apical cell membrane organization.

Evaluation of hepatocyte growth factor as a local acute phase response marker in the bowel: the clinical impact of a rapid diagnostic test for immediate identification of acute bowel inflammation

BACKGROUND

There are no rapid tests that can distinguish contagious gastroenteritis, which requires isolation at its onset, from exacerbation of chronic inflammatory bowel disease (IBD) or bowel engagement in the course of systemic inflammatory response syndrome (SIRS). Hepatocyte growth factor (HGF) is an acute phase cytokine that is produced at the site of injury. It has high affinity to sulfated glycan, and this binding affinity is lost during chronic inflammation. The fecal pH strongly impacts the prognosis for severe bowel disease. We developed a strip test to evaluate HGF as a local acute phase response marker in the bowel. This test assessed the binding affinity of HGF to sulfated glycans in fecal samples and determined fecal pH as an indicator of illness severity.

METHODS

Fresh feces from patients with diarrhea (n=513) were collected and tested blindly, and information about patient illness course and outcome was collected. Patients were classified based on the focus of inflammation and the cause of the symptoms. Objectively verified diagnoses of infectious gastroenteritis (n=131) and IBD onset/exacerbation and bowel cancer (n=44) were used to estimate the performance of the test strip. ELISA was performed on 101 freeze-thawed feces samples to determine the fecal HGF levels.

RESULTS

The test rapidly distinguished infectious gastroenteritis from non-infectious inflammatory causes of diarrhea (sensitivity, 87.96%; specificity, 90.9%; positive predictive value, 96.6%; negative predictive value, 71.4%; accuracy, 89.1%). Fecal pH (p<0.0001) and mortality within 28days of sampling (p<0.04) was higher in patients with sepsis/SIRS and diarrhea. The concentration of HGF was higher in strip test-positive stool samples (p<0.01).

CONCLUSIONS

HGF is a good local acute phase response marker of acute bowel inflammation. Test-strip determination of the binding affinity of fecal HGF to sulfated glycan was a rapid, equipment-free way to assess patients with diarrhea and to guide the diagnostic and therapeutic approaches on admission.

Mesenchymal stem cell-based NK4 gene therapy in nude mice bearing gastric cancer xenografts

Mesenchymal stem cells (MSCs) have been recognized as promising delivery vehicles for gene therapy of tumors. Gastric cancer is the third leading cause of worldwide cancer mortality, and novel treatment modalities are urgently needed. NK4 is an antagonist of hepatocyte growth factor receptors (Met) which are often aberrantly activated in gastric cancer and thus represent a useful candidate for targeted therapies. This study investigated MSC-delivered NK4 gene therapy in nude mice bearing gastric cancer xenografts. MSCs were transduced with lentiviral vectors carrying NK4 complementary DNA or enhanced green fluorescent protein (GFP). Such transduction did not change the phenotype of MSCs. Gastric cancer xenografts were established in BALB/C nude mice, and the mice were treated with phosphate-buffered saline (PBS), MSCs-GFP, Lenti-NK4, or MSCs-NK4. The tropism of MSCs toward gastric cancer cells was determined by an in vitro migration assay using MKN45 cells, GES-1 cells and human fibroblasts and their presence in tumor xenografts. Tumor growth, tumor cell apoptosis and intratumoral microvessel density of tumor tissue were measured in nude mice bearing gastric cancer xenografts treated with PBS, MSCs-GFP, Lenti-NK4, or MSCs-NK4 via tail vein injection. The results showed that MSCs migrated preferably to gastric cancer cells in vitro. Systemic MSCs-NK4 injection significantly suppressed the growth of gastric cancer xenografts. MSCs-NK4 migrated and accumulated in tumor tissues after systemic injection. The microvessel density of tumor xenografts was decreased, and tumor cellular apoptosis was significantly induced in the mice treated with MSCs-NK4 compared to control mice. These findings demonstrate that MSC-based NK4 gene therapy can obviously inhibit the growth of gastric cancer xenografts, and MSCs are a better vehicle for NK4 gene therapy than lentiviral vectors. Further studies are warranted to explore the efficacy and safety of the MSC-based NK4 gene therapy in animals and cancer patients.

Hepatocyte growth factor: A regulator of inflammation and autoimmunity

Hepatocyte growth factor (HGF) is a pleiotropic cytokine that has been extensively studied over several decades, but was only recently recognized as a key player in mediating protection of many types of inflammatory and autoimmune diseases. HGF was reported to prevent and attenuate disease progression by influencing multiple pathophysiological processes involved in inflammatory and immune response, including cell migration, maturation, cytokine production, antigen presentation, and T cell effector function. In this review, we discuss the actions and mechanisms of HGF in inflammation and immunity and the therapeutic potential of this factor for the treatment of inflammatory and autoimmune diseases.

Hepatocyte Growth Factor Isoforms in Tissue Repair, Cancer, and Fibrotic Remodeling

Hepatocyte growth factor (HGF), also known as scatter factor (SF), is a pleotropic factor required for normal organ development during embryogenesis. In the adult, basal expression of HGF maintains tissue homeostasis and is up-regulated in response to tissue injury. HGF expression is necessary for the proliferation, migration, and survival of epithelial and endothelial cells involved in tissue repair in a variety of organs, including heart, lung, kidney, liver, brain, and skin. The administration of full length HGF, either as a protein or using exogenous expression methodologies, increases tissue repair in animal models of tissue injury and increases angiogenesis. Full length HGF is comprised of an N-terminal hairpin turn, four kringle domains, and a serine protease-like domain. Several naturally occurring alternatively spliced isoforms of HGF were also identified. The NK1 variant contains the N-terminal hairpin and the first kringle domain, and the NK2 variant extends through the second kringle domain. These alternatively spliced forms of HGF activate the same receptor, MET, but they differ from the full length protein in their cellular activities and their biological functions. Here, we review the species-specific expression of the HGF isoforms, their regulation, the signal transduction pathways they activate, and their biological activities.

Spatially restricted Hedgehog signalling regulates HGF-induced branching of the adult prostate

Branching morphogenesis is thought to be governed by epithelial-stromal interactions, but the mechanisms underlying specification of branch location remain largely unknown. Prompted by the striking absence of Hedgehog (Hh) response at the sites of nascent buds in regenerating tubules of the adult prostate, we investigated the role of Hh signaling in adult prostate branching morphogenesis. We find that pathway activity is localized to stromal cells, and that its attenuation by genetic or pharmacologic manipulation leads to increased branching. Decreased pathway activity correlates with increased stromal production of Hepatocyte growth factor (Hgf), and we show that Hgf induces epithelial tubule branching. Regulation of Hgf expression by Hh signaling is indirect, mediated by Hh-induced expression of microRNAs miR-26a and miR-26b, which in turn down-regulate expression of Hgf. Prostate tubule branching thus may be initiated from regions of low Hh pathway activity, with implications for the prostatic hyperplasia commonly observed in late adulthood.

Pharmacokinetics and pharmacodynamics following intravenous administration of recombinant human hepatocyte growth factor in rats with renal injury

BACKGROUND/AIM

Hepatocyte growth factor (HGF) plays a role in the regeneration and protection of the kidney, but little information is available concerning the pharmacokinetics of therapeutic treatment with HGF. In this study, HGF was administered after the onset of renal injury, and pharmacokinetic analysis was performed simultaneously with an efficacious dose.

METHODS

For the study of pharmacodynamics, recombinant human HGF was intravenously administered to rats with glycerol-induced acute kidney injury (AKI). In the pharmacokinetic study, rats subjected to glycerol injection or renal ischemia-reperfusion were used as models of AKI, and rats subjected to 5/6 nephrectomy were used as models of chronic kidney disease (CKD).

RESULTS

After intravenous administration of HGF at doses of 0.5-2.0 mg/kg, the elevation of blood urea nitrogen was suppressed, indicating that HGF had a pharmacodynamic effect. However, no significant difference was seen in the pharmacokinetic parameters such as clearance, distribution volume and half-life between the normal, AKI and CKD groups.

CONCLUSION

The intravenous administration of HGF after the onset of renal dysfunction exerted a pharmacological effect on AKI, and renal injury did not affect the clearance of plasma HGF. This unaffected profile may serve as a base for the safety of HGF during therapeutic administration.

Targeting the epithelial to mesenchymal transition in glioblastoma: the emerging role of MET signaling

Glioblastoma multiforme (GBM) is the most common human primary brain malignancy and has a dismal prognosis. Aggressive treatments using maximal surgical resection, radiotherapy, and temozolomide result in median survival of only 14.6 months in patients with GBM. Numerous clinical approaches using small molecule inhibitors have shown disappointing results because of the genetic heterogeneity of GBM. The epithelial to mesenchymal transition (EMT) is a crucial biological process occurring in the early development stages of many species. However, cancer cells often obtain the ability to invade and metastasize through the EMT, which triggers the scattering of cells. The hepatocyte growth factor (HGF)/MET signaling pathway is indicative of the EMT during both embryogenesis and the invasive growth of tumors, because HGF potently induces mesenchymal transition in epithelial-driven cells. Activation of MET signaling or co-overexpression of HGF and MET frequently represents aggressive growth and poor prognosis of various cancers, including GBM. Thus, efforts to treat cancers by inhibiting MET signaling using neutralizing antibodies or small molecule inhibitors have progressed during the last decade. In this review, we discuss HGF/MET signaling in the development of diseases, including cancers, as well as updates on MET inhibition therapy.

Spatially restricted hyaluronan production by Has2 drives epithelial tubulogenesis in vitro

Generation of branched tubes from an epithelial bud is a fundamental process in development. We hypothesized that induction of hyaluronan synthase (Has) and production of hyaluronan (HA) drives tubulogenesis in response to morphogenetic cytokines. Treatment of J3B1A mammary cells with transforming growth factor-β1 or renal MDCK and mCCD-N21 cells with hepatocyte growth factor induced strong and specific expression of Has2. Immunostaining revealed that HA was preferentially produced at the tips of growing tubules. Inhibition of HA production, either by 4-methylumbelliferone (4-MU) or by Has2 mRNA silencing, abrogated tubule formation. HA production by J3B1A and mCCD-N21 cells was associated with sustained activation of ERK and S6 phosphorylation. However, silencing of either CD44 or RHAMM (receptor for HA-mediated motility), the major HA receptors, by RNA interference, did not alter tubulogenesis, suggesting that this process is not receptor-mediated.

SOMG-833, a novel selective c-MET inhibitor, blocks c-MET-dependent neoplastic effects and exerts antitumor activity

The hepatocyte growth factor/c-MET signaling axis plays an important role in tumor cell proliferation, metastasis, and tumor angiogenesis, and therefore presents as an attractive target for cancer therapy. Notably, most small-molecule c-MET inhibitors currently undergoing clinical trials are multitarget inhibitors with the unwanted inhibition of additional kinases, often accounting for undesirable toxicity. Here, we discovered SOMG-833 [3-(4-methylpiperazin-1-yl)-5-(3-nitrobenzylamino)-7-(trifluoromethyl) quinoline] as a potent and selective small-molecule c-MET inhibitor, with an average IC50 of 0.93 nM against c-MET, over 10,000-fold more potent compared with 19 tyrosine kinases, including c-MET family members and highly homologous kinases. SOMG-833 strongly suppressed c-MET-mediated signaling transduction regardless of mechanistic complexity implicated in c-MET activation, including MET gene amplification, MET gene fusion, and HGF-stimulated c-MET activation. In a panel of 24 human cancer or genetically engineered model cell lines, SOMG-833 potently inhibited c-MET-driven cell proliferation, whereas cancer cells lacking c-MET activation were markedly less sensitive (at least 15-fold) to the treatment. SOMG-833 also suppressed c-MET-mediated migration, invasion, urokinase activity, and invasive growth phenotype. In addition, inhibition of primary human umbilical vascular endothelial cell (HUVEC) proliferation and downregulation of plasma proangiogenic factor interleukin-8 secretion resulted from SOMG-833 treatment, suggesting its significant antiangiogenic properties. Together, these results led to the remarkable antitumor efficacy of SOMG-833 in vivo, as demonstrated in c-MET-dependent NIH-3T3/TPR-MET, U-87MG, and EBC-1 xenograft models. Collectively, our results suggested SOMG-833 as a promising candidate for highly selective c-MET inhibition and a powerful tool to investigate the sole role of MET kinase in cancer.

Activated K-RAS and its effect on morphological appearance

RAS genes are frequently mutated in various human tumours. These mutations cause GTPase RAS to remain locked in constitutively active signals through the downstream cascades leading to proliferation. A series of earlier studies reported on the morphological appearance of cells upon RAS activation. Classically, morphologic changes of fibroblasts have been used to confirm the oncogenic activity of RAS. Recent works found that the active RAS induces benign and malignant morphological changes in organoids, which are an in vitro model system for epithelial tissue. The studies of animal models support the basic oncogenic features of RAS revealed in vitro, while also providing evidence that the effects of RAS activation in vivo are different from those in vitro. The pathological observation of the various human materials indicates that the oncogenic RAS participates in metaplasia, which occurs before proliferation, and that RAS promotes mucin production in various organs. These morphological analyses may shed light on important signalling pathways that merit investigation in vitro.

Genetically encoded sender-receiver system in 3D mammalian cell culture

Engineering spatial patterning in mammalian cells, employing entirely genetically encoded components, requires solving several problems. These include how to code secreted activator or inhibitor molecules and how to send concentration-dependent signals to neighboring cells, to control gene expression. The Madin-Darby Canine Kidney (MDCK) cell line is a potential engineering scaffold as it forms hollow spheres (cysts) in 3D culture and tubulates in response to extracellular hepatocyte growth factor (HGF). We first aimed to graft a synthetic patterning system onto single developing MDCK cysts. We therefore developed a new localized transfection method to engineer distinct sender and receiver regions. A stable reporter line enabled reversible EGFP activation by HGF and modulation by a secreted repressor (a truncated HGF variant, NK4). By expanding the scale to wide fields of cysts, we generated morphogen diffusion gradients, controlling reporter gene expression. Together, these components provide a toolkit for engineering cell-cell communication networks in 3D cell culture.

3D in vitro cell culture models of tube formation

Building the complex architecture of tubular organs is a highly dynamic process that involves cell migration, polarization, shape changes, adhesion to neighboring cells and the extracellular matrix, physicochemical characteristics of the extracellular matrix and reciprocal signaling with the mesenchyme. Understanding these processes in vivo has been challenging as they take place over extended time periods deep within the developing organism. Here, I will discuss 3D in vitro models that have been crucial to understand many of the molecular and cellular mechanisms and key concepts underlying branching morphogenesis in vivo.

Effect of NK4 transduction in bone marrow-derived mesenchymal stem cells on biological characteristics of pancreatic cancer cells

Pancreatic cancer usually has a poor prognosis, and no gene therapy has yet been developed that is effective to treat it. Since a unique characteristic of bone marrow-derived mesenchymal stem cells (MSCs) is that they migrate to tumor tissues, we wanted to determine whether MSCs could serve as a vehicle of gene therapy for targeting pancreatic cancer. First, we successfully extracted MSCs from SD rats. Next, MSCs were efficiently transduced with NK4, an antagonist of hepatocyte growth factor (HGF) which comprising the N-terminal and the subsequent four kringle domains of HGF, by an adenoviral vector. Then, we confirmed that rat MSCs preferentially migrate to pancreatic cancer cells. Last, MSCs expressing NK4 (NK4-MSCs) strongly inhibited proliferation and migration of the pancreatic cancer cell line SW1990 after co-culture. These results indicate that MSCs can serve as a vehicle of gene therapy for targeting pancreatic cancer.

Drug-induced nephrotoxicity: clinical impact and preclinical in vitro models

The kidney is a major target for drug-induced toxicity. Drug-induced nephrotoxicity remains a major problem in the clinical setting, where the use of nephrotoxic drugs is often unavoidable. This leads frequently to acute kidney injury, and current problems are discussed. One strategy to avoid such problems would be the development of drugs with decreased nephrotoxic potential. However, the prediction of nephrotoxicity during preclinical drug development is difficult and nephrotoxicity is typically detected only late. Also, the nephrotoxic potential of newly approved drugs is often underestimated. Regulatory approved or validated in vitro models for the prediction of nephrotoxicity are currently not available. Here, we will review current approaches on the development of such models. This includes a discussion of three-dimensional and microfluidic models and recently developed stem cell based approaches. Most in vitro models have been tested with a limited number of compounds and are of unclear predictivity. However, some studies have tested larger numbers of compounds and the predictivity of the respective in vitro model had been determined. The results showed that high predictivity can be obtained by using primary or stem cell derived human renal cells in combination with appropriate end points.

Enriched protein screening of human bone marrow mesenchymal stromal cell secretions reveals MFAP5 and PENK as novel IL-10 modulators

The secreted proteins from a cell constitute a natural biologic library that can offer significant insight into human health and disease. Discovering new secreted proteins from cells is bounded by the limitations of traditional separation and detection tools to physically fractionate and analyze samples. Here, we present a new method to systematically identify bioactive cell-secreted proteins that circumvent traditional proteomic methods by first enriching for protein candidates by differential gene expression profiling. The bone marrow stromal cell secretome was analyzed using enriched gene expression datasets in combination with potency assay testing. Four proteins expressed by stromal cells with previously unknown anti-inflammatory properties were identified, two of which provided a significant survival benefit to mice challenged with lethal endotoxic shock. Greater than 85% of secreted factors were recaptured that were otherwise undetected by proteomic methods, and remarkable hit rates of 18% in vitro and 9% in vivo were achieved.

Basal localization of MT1-MMP is essential for epithelial cell morphogenesis in 3D collagen matrix

The membrane-anchored collagenase membrane type 1 matrix metalloprotease (MT1-MMP) has been shown to play an essential role during epithelial tubulogenesis in 3D collagen matrices; however, its regulation during tubulogenesis is not understood. Here, we report that degradation of collagen in polarized epithelial cells is post-translationally regulated by changing the localization of MT1-MMP from the apical to the basal surface. MT1-MMP predominantly localizes at the apical surface in inert polarized epithelial cells, whereas treatment with HGF induced basal localization of MT1-MMP followed by collagen degradation. The basal localization of MT1-MMP requires the ectodomains of the enzyme because deletion of the MT-loop region or the hemopexin domain inhibited basal localization of the enzyme. TGFβ is a well-known inhibitor of tubulogenesis and our data indicate that its mechanism of inhibition is, at least in part, due to inhibition of MT1-MMP localization to the basal surface. Interestingly, however, the effect of TGFβ was found to be bi-phasic: at high doses it effectively inhibited basal localization of MT1-MMP, whereas at lower doses tubulogenesis and basal localization of MT1-MMP was promoted. Taken together, these data indicate that basal localization of MT1-MMP is a key factor promoting the degradation of extracellular matrix by polarized epithelial cells, and that this is an essential part of epithelial morphogenesis in 3D collagen.

Polycystin-1 negatively regulates Polycystin-2 expression via the aggresome/autophagosome pathway

Mutations of the PKD1 and PKD2 genes, encoding polycystin-1 (PC1) and polycystin-2 (PC2), respectively, lead to autosomal dominant polycystic kidney disease. Interestingly, up-regulation or down-regulation of PKD1 or PKD2 leads to polycystic kidney disease in animal models, but their interrelations are not completely understood. We show here that full-length PC1 that interacts with PC2 via a C-terminal coiled-coil domain regulates PC2 expression in vivo and in vitro by down-regulating PC2 expression in a dose-dependent manner. Expression of the pathogenic mutant R4227X, which lacks the C-terminal coiled-coil domain, failed to down-regulate PC2 expression, suggesting that PC1-PC2 interaction is necessary for PC2 regulation. The proteasome and autophagy are two pathways that control protein degradation. Proteins that are not degraded by proteasomes precipitate in the cytoplasm and are transported via histone deacetylase 6 (HDAC6) toward the aggresomes. We found that HDAC6 binds to PC2 and that expression of full-length PC1 accelerates the transport of the HDAC6-PC2 complex toward aggresomes, whereas expression of the R4227X mutant fails to do so. Aggresomes are engulfed by autophagosomes, which then fuse with the lysosome for degradation; this process is also known as autophagy. We have now shown that PC1 overexpression leads to increased degradation of PC2 via autophagy. Interestingly, PC1 does not activate autophagy generally. Thus, we have now uncovered a new pathway suggesting that when PC1 is expressed, PC2 that is not bound to PC1 is directed to aggresomes and subsequently degraded via autophagy, a control mechanism that may play a role in autosomal dominant polycystic kidney disease pathogenesis.

Paracrine activation of MET promotes peritoneal carcinomatosis in scirrhous gastric cancer

Scirrhous gastric cancer is associated with abundant stroma and frequently develops into peritoneal carcinomatosis with malignant ascites. Although malignant ascites is among the most deadly diseases worldwide, its molecular pathogenesis is poorly understood. We investigated the role of hepatocyte growth factor (HGF) in the production of peritoneal carcinomatosis with malignant ascites. We examined three scirrhous and three non-scirrhous human gastric cancer cell lines for the production of peritoneal carcinomatosis in vivo and responses to HGF in vitro. Furthermore, clinical scirrhous gastric cancer specimens were examined for HGF production. Among the six cell lines examined, only two scirrhous cell lines (NUGC4 and GCIY) produced peritoneal carcinomatosis with massive ascites after intraperitoneal injection in nude mice. Their proliferation was stimulated by exogenous HGF in vitro. On the other hand, a non-scirrhous cell line, MKN45, with MET amplification generated peritoneal tumors but not ascites. MET tyrosine kinase inhibitors, crizotinib and TAS-115, inhibited HGF-stimulated proliferation of NUGC4 and GCIY as well as constitutive proliferation of MKN45. Furthermore, crizotinib and TAS-115 prolonged the survival of mice bearing established tumors by NUGC4 or MKN45. In clinical specimens, HGF was markedly produced by stromal fibroblasts. Malignant ascitic fluids from patients with peritoneal carcinomatosis contained high levels of HGF. Our results strongly suggest that paracrine HGF-induced activation of MET-mediated signaling pathways plays an important role in the pathogenesis of peritoneal carcinomatosis in scirrhous gastric cancer. Thus, MET signaling pathway may be a potential therapeutic target for peritoneal carcinomatosis of gastric cancer, even without MET amplification.

Concise review: can the intrinsic power of branching morphogenesis be used for engineering epithelial tissues and organs?

Branching morphogenesis is critical to the development of organs such as kidney, lung, mammary gland, prostate, pancreas, and salivary gland. Essentially, an epithelial bud becomes an iterative tip-stalk generator (ITSG) able to form a tree of branching ducts and/or tubules. In different organs, branching morphogenesis is governed by similar sets of genes. Epithelial branching has been recapitulated in vitro (or ex vivo) using three-dimensional cell culture and partial organ culture systems, and several such systems relevant to kidney tissue engineering are discussed here. By adapting systems like these it may be possible to harness the power inherent in the ITSG program to propagate and engineer epithelial tissues and organs. It is also possible to conceive of a universal ITSG capable of propagation that may, by recombination with organ-specific mesenchymal cells, be used for engineering many organ-like tissues similar to the organ from which the mesenchyme cells were derived, or toward which they are differentiated (from stem cells). The three-dimensional (3D) branched epithelial structure could act as a dynamic branching cellular scaffold to establish the architecture for the rest of the tissue. Another strategy-that of recombining propagated organ-specific ITSGs in 3D culture with undifferentiated mesenchymal stem cells-is also worth exploring. If feasible, such engineered tissues may be useful for the ex vivo study of drug toxicity, developmental biology, and physiology in the laboratory. Over the long term, they have potential clinical applications in the general fields of transplantation, regenerative medicine, and bioartificial medical devices to aid in the treatment of chronic kidney disease, diabetes, and other diseases.

Synergistic effects of ultrasound-targeted microbubble destruction and TAT peptide on gene transfection: an experimental study in vitro and in vivo

Cell-permeable peptides (CPPs) and ultrasound-targeted microbubble destruction (UTMD) have tremendous potential for gene delivery. However, their applications are limited due to nonspecificity of CPPs and low transfection efficiency of UTMD. Here, we developed a 'smart' gene delivery system by encapsulating TAT peptide (TATp) and hepatocyte growth factor (HGF) gene within lipid microbubbles, in which TATp was protected from being enzymatically cleaved and HGF gene was protected from degradation. This new strategy had synergistic effects of UTMD and TATp on gene transfection. We investigated the efficacy and safety of HGF gene transfection mediated by the combination of UTMD and TATp in vitro and in vivo. The results from MTT assay and flow cytometry analyses indicated that the combination of UTMD and TATp could enhance HGF gene expression in HUVECs without any significant side effect on cell viability. In rat myocardial infarction models, we demonstrated that the protein and mRNA expressions of HGF in myocardium caused by the combination of UTMD and TATp were the highest. Histopathological findings demonstrated that the combination of UTMD and TATp enhanced myocardial microvasculature and ameliorated myocardial fibrosis. In conclusion, the combination of UTMD and TATp might be a safe and efficient technique for gene delivery.

[A new drug in thoracic oncology: MetMab (onartuzumab)]

Met pathway is activated in many solid cancers. In advanced non-small cell lung cancer (NSCLC), Met amplification is involved in 5 to 20% of acquired resistance to EGFR tyrosine kinase inhibitors (TKI) in tumors with initially sensitive EGFR mutation. MetMab (onartuzumab) is a monoclonal single-arm humanized anti-Met antibody. Its fixation on the Met receptor prevents the binding of the ligand (Hepatocyte Growth factor [HGF]) and the signal transduction. After promising results in preclinical and phase I trials, a randomized phase II trial has been conducted in advanced NSCLC in 2nd or 3rd line treatment. One hundred and twenty-eight patients have been randomized between an association of erlotinib+placebo and erlotinib+MetMab (15mg/kg IV every 3 weeks) until progression or toxicity. Patients with overexpression of Met in immunohistochemistry (IHC) had a progression-free survival (PFS) and an overall survival (OS) two-fold (median 1.5 versus 2.9 months; HR=0.53; P=0.04) and three-fold (median 3.8 versus 12.6 months; HR=0.37; P=0.002) longer, respectively, than patients with negative IHC score. The erlotinib+MetMab association had a worse effect on SSP and OS than the control arm in patients with negative IHC. The toxicity profile of MetMab is very good, and the main adverse effect is the occurrence of peripheral edemas, most of the time of low grade. A randomized phase III is on going to validate these results.

Epithelial morphogenesis of MDCK cells in three-dimensional collagen culture is modulated by interleukin-8

Epithelial morphogenesis is dependent upon a variety of factors, many of which involve complex interactions between cells and their surrounding environments. We analyzed the patterns of differential gene expression associated with Madin-Darby canine kidney (MDCK) renal epithelial cells grown within a collagen gel in three-dimensional (3D) culture compared with those grown atop a collagen gel in two-dimensional (2D) culture. Under these conditions, MDCK cells spontaneously formed either hollow spherical cysts or flat monolayer sheets, respectively. Microarray analysis of gene expression revealed a twofold or greater expression difference in 732 gene sets from MDCK cysts compared with monolayers (false discovery rate or FDR-adjusted P values <0.05). Interleukin-8 (IL-8) was reproducibly found to be among the genes whose expression was most dramatically upregulated, and this behavior was verified through real-time PCR analysis. The level of IL-8 protein expression was significantly increased in 3D MDCK cultures compared with that detected in cells in 2D culture. Hepatocyte growth factor (HGF) induces MDCK cells in 3D culture to form linear tubule-like structures. We found that HGF stimulation caused MDCK cells in 3D culture to decrease the expression of IL-8 at both the mRNA and protein levels. Furthermore, the addition of recombinant IL-8 to HGF-stimulated 3D MDCK cultures was sufficient to partially reverse the tubulogenic effects of HGF, resulting in the formation of cystic structures. These data suggest that IL-8 participates in the formation of cystic structures by MDCK cells in 3D culture and that HGF may stimulate tubulogenesis through the suppression of IL-8.

A novel c-Met inhibitor, MK8033, synergizes with carboplatin plus paclitaxel to inhibit ovarian cancer cell growth

Elevated serum levels of hepatocyte growth factor (HGF) and high tumor expression of c-Met are both indicators of poor overall survival from ovarian cancer (OVCA). In the present study, we evaluated the role of the HGF signaling pathway in OVCA cell line chemoresistance and OVCA patient overall survival as well as the influence of HGF/c-Met signaling inhibition on the sensitivity of OVCA cells to combinational carboplatin plus paclitaxel therapy. The prevalence of the HGF receptor, c-Met, was determined by immunohistochemistry in primary OVCA samples (n=79) and OVCA cell lines (n=41). The influence of the c-Met-specific inhibitor MK8033 on OVCA cell sensitivity to combinations of carboplatin plus paclitaxel was examined in a subset of OVCA cells (n=8) by CellTiter-Blue cell viability assays. Correlation tests were used to identify genes associated with response to MK8033 and carboplatin plus paclitaxel. Identified genes were evaluated for influence on overall survival from OVCA using principal component analysis (PCA) modeling in an independent clinical OVCA dataset (n=218). Immunohistochemistry analysis indicated that 83% of OVCA cells and 92% of primary OVCA expressed the HGF receptor, c-Met. MK8033 exhibited significant anti-proliferative effects against a panel of human OVCA cell lines. Combination index values determined by the Chou-Talalay isobologram equation indicated synergistic activity in combinations of MK8033 and carboplatin plus paclitaxel. Pearson's correlation identified a 47-gene signature to be associated with MK8033-carboplatin plus paclitaxel response. PCA modeling indicated an association of this 47-gene response signature with overall survival from OVCA (P=0.013). These data indicate that HGF/c-Met pathway signaling may influence OVCA chemosensitivity and overall patient survival. Furthermore, HGF/c-Met inhibition by MK8033 represents a promising new therapeutic avenue to increase OVCA sensitivity to carboplatin plus paclitaxel.

The scaffolding protein GRASP/Tamalin directly binds to Dock180 as well as to cytohesins facilitating GTPase crosstalk in epithelial cell migration

Background

The transition of epithelial cells from their normal non-motile state to a motile one requires the coordinated action of a number of small GTPases. We have previously shown that epithelial cell migration is stimulated by the coordinated activation of Arf and Rac GTPases. This crosstalk depends upon the assembly of a multi-protein complex that contains the Arf-activating protein cytohesin 2/ARNO and the Rac activating protein Dock180. Two scaffolding proteins that bind directly to cytohesin 2 organize this complex.

Results

We now have found that Rac activation in response to hepatocyte growth factor (HGF) requires cytohesin 2 and Dock180. GRASP/Tamalin is one of the scaffolds that builds the complex containing cytohesin 2 and Dock180. We determine here that the Ala/Pro rich region of GRASP directly interacts with the SH3 domain of Dock180. By binding to both cytohesin 2/ARNO and Dock180, GRASP bridges the guanine nucleotide exchange factors (GEFs) that activate Arf and Rac, thereby promoting Arf-to-Rac signaling. Furthermore, we find that knockdown of GRASP impairs hepatocyte growth factor (HGF)-stimulated Rac activation and HGF-stimulated epithelial migration.

Conclusions

GRASP binds directly both cytohesin 2 and Dock180 to coordinate their activities, and by doing so promotes crosstalk between Arf and Rac.

Therapeutic potentials occurring during the early differentiation process of mesenchymal stem cells in a rats model with thioacetamide-induced liver fibrosis

BACKGROUNDS/AIMS

Mesenchymal stem cells (MSCs) have the capacity to differentiate into hepatocytes, The purpose of this study is to investigate the MSCs' differentiation process and therapeutic potentials by comparing isolated MSCs with HGF-treated MSCs in rat's model with thiacetamide (TAA)-induced cirrhosis.

METHODS

Male Sprague-Dawley (SD) rats, weighing 100-150 g were used in this study. To induce liver fibrosis, recipient rats were taken with 0.04% thioacetamide (TAA) in the drinking water (400 mg TAA/L) for 8 weeks. The rats underlying liver cirrhosis were divided into 3 groups according to the transplanted materials, compared to normal saline as control (I) and isolated MSCs (II) HGF-treated MSCs.

RESULTS

Severe hepatic fibrosis and hepatocyte destruction were detected in the control group. Less hepatic cirrhosis and collagen formation, more hepatocyte regeneration and glycogen storage were detected in isolated MSCs compared to HGF-treated MSCs group, Distribution of red autofluorescence is mainly localized near the sinusoids in isolated MSCs, scattered away the sinusoids in HGF-treated MSCs group. MSCs transdifferentiated into CK-19 postive Oval cells and then to albulmin-producing hepatocytes, HGF treated MSCs differentiated into hepatocyte without the intermediate oval cells phase. HGF treated MSCs became the CK18-positive, MSCs became CD 90-positive.

CONCLUSIONS

Significant hepatocyte differentiation occurred in not HGF-treated MSCs but isolated MSCs group unexpectedly. These results suggest that the beneficial effect of MSCs on in rat's model with TAA-induced cirrhosis may occur during early differentiation course of MSCs. Mature hepatocyte itself has a little effect on the accelerated differentiation and functional capacity of hepatic lineage cell-line.

In vitro organogenesis in three dimensions: self-organising stem cells

Organ formation during embryogenesis is a complex process that involves various local cell-cell interactions at the molecular and mechanical levels. Despite this complexity, organogenesis can be modelled in vitro. In this article, we focus on two recent examples in which embryonic stem cells can self-organise into three-dimensional structures - the optic cup and the pituitary epithelium; and one case of self-organising adult stem cells - the gut epithelium. We summarise how these approaches have revealed intrinsic programs that drive locally autonomous modes of organogenesis and homeostasis. We also attempt to interpret the results of previous in vivo studies of retinal development in light of the self-organising nature of the retina.

Targeting the HGF-cMET Axis in Hepatocellular Carcinoma

Under normal physiological conditions, the hepatocyte growth factor (HGF) and its receptor, the MET transmembrane tyrosine kinase (cMET), are involved in embryogenesis, morphogenesis, and wound healing. The HGF-cMET axis promotes cell survival, proliferation, migration, and invasion via modulation of epithelial-mesenchymal interactions. Hepatocellular cancer (HCC) is the third most common cause of worldwide cancer-related mortality; advanced disease is associated with a paucity of therapeutic options and a five-year survival rate of only 10%. Dysregulation of the HGF-cMET pathway is implicated in HCC carcinogenesis and progression through activation of multiple signaling pathways; therefore, cMET inhibition is a promising therapeutic strategy for HCC treatment. The authors review HGF-cMET structure and function in normal tissue and in HCC, cMET inhibition in HCC, and future strategies for biomarker identification.

Robust formation and maintenance of continuous stratified cortical neuroepithelium by laminin-containing matrix in mouse ES cell culture

In the mammalian cortex, the dorsal telencephalon exhibits a characteristic stratified structure. We previously reported that three-dimensional (3D) culture of mouse ES cells (mESCs) can efficiently generate cortical neuroepithelium (NE) and layer-specific cortical neurons. However, the cortical NE generated in this mESC culture was structurally unstable and broke into small neural rosettes by culture day 7, suggesting that some factors for reinforcing the structural integrity were missing. Here we report substantial supporting effects of the extracellular matrix (ECM) protein laminin on the continuous formation of properly polarized cortical NE in floating aggregate culture of mESCs. The addition of purified laminin and entactin (a laminin-associated protein), even at low concentrations, stabilized the formation of continuous cortical NE as well as the maintenance of basement membrane and prevented rosette formation. Treatment with the neutralizing ß1-integrin antibody impaired the continuous NE formation. The stabilized cortical NE exhibited typical interkinetic nuclear migration of cortical progenitors, as seen in the embryonic cortex. The laminin-treated cortical NE maintained a continuous structure even on culture days 12 and 15, and contained ventricular, basal-progenitor, cortical-plate and Cajal-Retzius cell layers. The cortical NE in this culture was flanked by cortical hem-like tissue. Furthermore, when Shh was added, ventral telencephalic structures such as lateral ganglionic eminence–like tissue formed in the region adjacent to the cortical NE. Thus, our results indicate that laminin-entactin ECM promotes the formation of structurally stable telencephalic tissues in 3D ESC culture, and supports the morphogenetic recapitulation of cortical development.

Epithelial-mesenchymal transition stimulates human cancer cells to extend microtubule-based invasive protrusions and suppresses cell growth in collagen gel

Epithelial-mesenchymal transition (EMT) is a crucial event in tumor invasion and metastasis. However, most of past EMT studies have been conducted in the conventional two-dimensional (2D) monolayer culture. Therefore, it remains unclear what invasive phenotypes are acquired by EMT-induced cancer cells. To address this point, we attempted to characterize EMT cells in more physiological, three-dimensional (3D) collagen gel culture. EMT was induced by treating three human carcinoma cell lines (A549, Panc-1 and MKN-1) with TGF-ß. The TGF-ß treatment stimulated these cells to overexpress the invasion markers laminin γ2 and MT1-MMP in 2D culture, in addition to the induction of well-known morphological change and EMT marker expression. EMT induction enhanced cell motility and adhesiveness to fibronectin and collagen in 2D culture. Although EMT cells showed comparable cell growth to control cells in 2D culture, their growth rates were extremely suppressed in soft agar and collagen gel cultures. Most characteristically, EMT-induced cancer cells commonly and markedly extended invasive protrusions in collagen gel. These protrusions were mainly supported by microtubules rather than actin cytoskeleton. Snail-introduced, stable EMT cells showed similar protrusions in 3D conditions without TGF-ß. Moreover, these protrusions were suppressed by colchicine or inhibitors of heat shock protein 90 (HSP-90) and protein phosphatase 2A. However, MMP inhibitors did not suppress the protrusion formation. These data suggest that EMT enhances tumor cell infiltration into interstitial stroma by extending microtubule-based protrusions and suppressing cell growth. The elevated cell adhesion to fibronectin and collagen and high cell motility also seem important for the tumor invasion.

Chimaerin suppresses Rac1 activation at the apical membrane to maintain the cyst structure

Epithelial organs are made of a well-polarized monolayer of epithelial cells, and their morphology is maintained strictly for their proper functions. Previously, we showed that Rac1 activation is suppressed at the apical membrane in the mature organoid, and that such spatially biased Rac1 activity is required for the polarity maintenance. Here we identify Chimaerin, a GTPase activating protein for Rac1, as a suppressor of Rac1 activity at the apical membrane. Depletion of Chimaerin causes over-activation of Rac1 at the apical membrane in the presence of hepatocyte growth factor (HGF), followed by luminal cell accumulation. Importantly, Chimaerin depletion did not inhibit extension formation at the basal membrane. These observations suggest that Chimaerin functions as the apical-specific Rac1 GAP to maintain epithelial morphology.

Hepatocyte growth factor and lung fibrosis

Idiopathic pulmonary fibrosis is currently believed to be driven by alveolar epithelial cells, with abnormally activated alveolar epithelial cells accumulating in an attempt to repair injured alveolar epithelium (1). Thus, targeting the alveolar epithelium to prevent or inhibit the development of pulmonary fibrosis might be an interesting therapeutic option in this disease. Hepatocyte growth factor (HGF) is a growth factor for epithelial and endothelial cells, which is secreted by different cell types, especially fibroblasts and neutrophils. HGF has mitogenic, motogenic, and morphogenic properties and exerts an antiapoptotic action on epithelial and endothelial cells. HGF has also proangiogenic effect. In vitro, HGF inhibits epithelial-to-mesenchymal cell transition and promotes myofibroblast apoptosis. In vivo, HGF has antifibrotic properties demonstrated in experimental models of lung, kidney, heart, skin, and liver fibrosis. Hence, the modulation of HGF may be an attractive target for the treatment of lung fibrosis.

Loss of HGF activator inhibits foveolar hyperplasia induced by oxyntic atrophy without altering gastrin levels

Spasmolytic polypeptide/trefoil family factor 2 expressing metaplasia (SPEM) is induced by oxyntic atrophy and is known as a precancerous or paracancerous lesion. We now have sought to determine whether hepatocyte growth factor (HGF) influences the development of SPEM and oxyntic atrophy. DMP-777, a parietal cell ablating reagent, was administered to HGF activator (HGFA)-deficient mice and wild-type mice. Gastric mucosal lineage changes were analyzed in the DMP-777 treatment phase and recovery phase. Both wild-type and HGFA knockout mice showed SPEM, and there was no difference in SPEM development. However, after cessation of DMP-777, HGFA-deficient mice showed delayed recovery from SPEM compared with wild-type mice. Foveolar cell hyperplasia and the increase in proliferating cells after parietal cell loss were reduced in HGFA-deficient mice. The HGFA does not affect emergence of SPEM. However, the absence of HGFA signaling causes a delay in the recovery from SPEM to normal glandular composition. HGFA also promotes foveolar cell hyperplasia and mucosal cell proliferation in acute oxyntic injury.

Hepatocyte growth factor increases vascular endothelial growth factor-A production in human synovial fibroblasts through c-Met receptor pathway

Background

Angiogenesis is essential for the progression of osteoarthritis (OA). Hepatocyte growth factor (HGF) is an angiogenic mediator, and it shows elevated levels in regions of OA. However, the relationship between HGF and vascular endothelial growth factor (VEGF-A) in OA synovial fibroblasts (OASFs) is mostly unknown.

Methodology/Principal Findings

Here we found that stimulation of OASFs with HGF induced concentration- and time-dependent increases in VEGF-A expression. Pretreatment with PI3K inhibitor (Ly294002), Akt inhibitor, or mTORC1 inhibitor (rapamycin) blocked the HGF-induced VEGF-A production. Treatment of cells with HGF also increased PI3K, Akt, and mTORC1 phosphorylation. Furthermore, HGF increased the stability and activity of HIF-1 protein. Moreover, the use of pharmacological inhibitors or genetic inhibition revealed that c-Met, PI3K, Akt, and mTORC1 signaling pathways were potentially required for HGF-induced HIF-1α activation.

Conclusions/Significance

Taken together, our results provide evidence that HGF enhances VEGF-A expression in OASFs by an HIF-1α-dependent mechanism involving the activation of c-Met/PI3K/Akt and mTORC1 pathways.

c-Met: A potential therapeutic target for hepatocellular carcinoma

The approval of receptor tyrosine kinase (RTK) targeted agent sorafenib as the first effective drug for the systemic treatment of advanced hepatocellular carcinoma (HCC) represents a milestone in the treatment of this disease. A better understanding of HCC pathogenesis will lead to development of novel targeted treatments. As a typical member of the RTK family, c-Met represents an intriguing target for cancer therapy. The c-Met signaling pathway has been shown to be deregulated and to correlate with poor prognosis in a number of major human cancers. This review discusses the possibility of c-Met as a target in HCC treatment from the following respects: i) c-Met expression and activation profile in HCC, ii) relationship between c-Met and clinicopathologic state and prognosis of HCC, iii) role of c-Met signaling activity in HCC genesis and progression, and iv) strategy of c-Met pathway targeting therapy in HCC treatment.

Mechanisms of HGF/Met signaling to Brk and Sam68 in breast cancer progression

Signal transduction pathways downstream of receptor tyrosine kinases (RTKs) are often deregulated during oncogenesis, tumor progression, and metastasis. In particular, the peptide growth factor hormone, hepatocyte growth factor (HGF), and its specific receptor, Met tyrosine kinase, regulate cancer cell migration, thereby conferring an aggressive phenotype (Nakamura et al., J Clin Invest 106(12):1511-1519, 2000; Huh et al., Proc Natl Acad Sci U S A 101:4477-4482, 2004). Additionally, overexpression of Met is associated with enhanced invasiveness of breast cancer cells (Edakuni et al., Pathol Int 51(3):172-178, 2001; Jin et al., Cancer 79(4):749-760, 1997; Tuck et al., Am J Pathol 148(1):225-232, 1996). Here, we review the regulation of recently identified novel downstream mediators of HGF/Met signaling, Breast tumor kinase (Brk/PTK6), and Src-associated substrate during mitosis of 68 kDa (Sam68), and discuss their relevance to mechanisms of breast cancer progression.

RACK1 regulates mesenchymal cell recruitment during sexual and asexual reproduction of budding tunicates

A homolog of receptor for activated protein kinase C1 (RACK1) was cloned from the budding tunicate Polyandrocarpa misakiensis. By RT-PCR and in situ hybridization analyses, PmRACK1 showed biphasic gene expression during asexual and sexual reproduction. In developing buds, the signal was exclusively observed in the multipotent atrial epithelium and undifferentiated mesenchymal cells that contributed to morphogenesis by the mesenchymal-epithelial transition (MET). In juvenile zooids, the signal was first observable in germline precursor cells that arose as mesenchymal cell aggregated in the ventral hemocoel. In mature zooids, the germinal epithelium in the ovary and the pharynx were the most heavily stained parts. GFP reporter assay indicated that the ovarian expression of PmRACK1 was constitutive from germline precursor cells to oocytes. To elucidate the in vivo function of PmRACK1, RNA interference was challenged. When growing buds were incubated with 5 nmol/mL siRNA, most mesenchymal cells remained round and appeared to have no interactions with the extracellular matrix (ECM), causing lower activity of MET without any apparent effects on cell proliferation. The resultant zooids became growth-deficient. The dwarf zooids did not form buds or mature gonads. Prior to RNAi, buds were treated with human BMP4 that could induce PmRACK1 expression, which resulted in MET activity. We conclude that in P. misakiensis, PmRACK1 plays roles in mesenchymal cell recruitment during formation of somatic and gonad tissues, which contributes to zooidal growth and sexual and asexual reproduction.

Hepatocyte growth factor increases osteopontin expression in human osteoblasts through PI3K, Akt, c-Src, and AP-1 signaling pathway

BACKGROUND

Hepatocyte growth factor (HGF) has been demonstrated to stimulate osteoblast proliferation and participated bone remodeling. Osteopontin (OPN) is a secreted phosphoglycoprotein that belongs to the SIBLING family and is present during bone mineralization. However, the effects of HGF on OPN expression in human osteoblasts are large unknown.

METHODOLOGY/PRINCIPAL FINDINGS

Here we found that HGF induced OPN expression in human osteoblasts dose-dependently. HGF-mediated OPN production was attenuated by c-Met inhibitor and siRNA. Pretreatment of osteoblasts with PI3K inhibitor (Ly294002), Akt inhibitor, c-Src inhibitor (PP2), or AP-1 inhibitor (curcumin) blocked the potentiating action of HGF. Stimulation of osteoblasts with HGF enhanced PI3K, Akt, and c-Src activation. In addition, incubation of cells with HGF also increased c-Jun phosphorylation, AP-1-luciferase activity, and c-Jun binding to the AP-1 element on the OPN promoter. HGF-mediated AP-1-luciferase activity and c-Jun binding to the AP-1 element was reduced by c-Met inhibitor, Ly294002, Akt inhibitor, and PP2.

CONCLUSIONS/SIGNIFICANCE

Our results suggest that the interaction between HGF and c-Met increases OPN expression in human osteoblasts via the PI3K, Akt, c-Src, c-Jun, and AP-1 signaling pathway.

Scrib regulates HGF-mediated epithelial morphogenesis and is stabilized by Sgt1-HSP90

Scribble was originally identified as a Drosophila protein that regulates epithelial polarity and formation of the basolateral surface. The mammalian orthologue, Scrib, is evolutionarily conserved, but does not appear to be necessary for apical-basolateral epithelial polarity. Instead, it is implicated in the regulation of cell survival, protein trafficking, adhesion and migration. A key issue is to understand the molecular pathway by which Scrib participates in these processes. We have investigated Scrib using a three-dimensional epithelial cell culture system. We show a novel association between the leucine-rich repeat domain of Scrib and the co-chaperone Sgt1 and demonstrate that these proteins are necessary for epithelial morphogenesis and tubulogenesis following hepatocyte growth factor (HGF) stimulation. The molecular chaperone HSP90 is also required for Sgt1 association with Scrib, and both Sgt1 and HSP90 are needed to ensure proper Scrib protein levels. Furthermore, reduced Scrib stability, following inhibition of Sgt1-HSP90, lowers the cellular abundance of the Scrib-βPix-PAK complex. Inhibition of any member of this complex, Scrib, βPix or PAK, is sufficient to block HGF-mediated epithelial morphogenesis. The identification of Scrib as an Sgt1-HSP90 client protein required for three-dimensional cell migration suggests that chaperone-mediated regulation of polarity protein stability and homeostasis is an unappreciated mechanism underlying dynamic rearrangements during morphogenesis.

Paracrine receptor activation by microenvironment triggers bypass survival signals and ALK inhibitor resistance in EML4-ALK lung cancer cells

PURPOSE

Cancer cell microenvironments, including host cells, can critically affect cancer cell behaviors, including drug sensitivity. Although crizotinib, a dual tyrosine kinase inhibitor (TKI) of ALK and Met, shows dramatic effect against EML4-ALK lung cancer cells, these cells can acquire resistance to crizotinib by several mechanisms, including ALK amplification and gatekeeper mutation. We determined whether microenvironmental factors trigger ALK inhibitor resistance in EML4-ALK lung cancer cells.

EXPERIMENTAL DESIGN

We tested the effects of ligands produced by endothelial cells and fibroblasts, and the cells themselves, on the susceptibility of EML4-ALK lung cancer cell lines to crizotinib and TAE684, a selective ALK inhibitor active against cells with ALK amplification and gatekeeper mutations, both in vitro and in vivo.

RESULTS

EML4-ALK lung cancer cells were highly sensitive to ALK inhibitors. EGF receptor (EGFR) ligands, such as EGF, TGF-α, and HB-EGF, activated EGFR and triggered resistance to crizotinib and TAE684 by transducing bypass survival signaling through Erk1/2 and Akt. Hepatocyte growth factor (HGF) activated Met/Gab1 and triggered resistance to TAE684, but not crizotinib, which inhibits Met. Endothelial cells and fibroblasts, which produce the EGFR ligands and HGF, respectively, decreased the sensitivity of EML4-ALK lung cancer cells to crizotinib and TAE684, respectively. EGFR-TKIs resensitized these cells to crizotinib and Met-TKI to TAE684 even in the presence of EGFR ligands and HGF, respectively.

CONCLUSIONS

Paracrine receptor activation by ligands from the microenvironment may trigger resistance to ALK inhibitors in EML4-ALK lung cancer cells, suggesting that receptor ligands from microenvironment may be additional targets during treatment with ALK inhibitors.