Adaptor protein CRK induces epithelial–mesenchymal transition and metastasis of bladder cancer cells through HGF/c‐Met feedback loop

We have previously reported that an adaptor protein CRK, including CRK‐I and CRK‐II, plays essential roles in the malignant potential of various aggressive human cancers, suggesting the validity of targeting CRK in molecular targeted therapy of a wide range of cancers. Nevertheless, the role of CRK in human bladder cancer with marked invasion, characterized by distant metastasis and poor prognosis, remains obscure. In the present study, immunohistochemistry indicated a striking enhancement of CRK‐I/‐II, but not CRK‐like, in human bladder cancer tissues compared to normal urothelium. We established CRK‐knockdown bladder cancer cells using 5637 and UM‐UC‐3, which showed a significant decline in cell migration, invasion, and proliferation. It is noteworthy that an elimination of CRK conferred suppressed phosphorylation of c‐Met and the downstream scaffold protein Gab1 in a hepatocyte growth factor‐dependent and ‐independent manner. In epithelial–mesenchymal transition‐related molecules, E‐cadherin was upregulated by CRK elimination, whereas N‐cadherin, vimentin, and Zeb1 were downregulated. A similar effect was observed following treatment with c‐Met inhibitor SU11274. Depletion of CRK significantly decreased cell proliferation of 5637 and UM‐UC‐3, consistent with reduced activity of ERK. An orthotopic xenograft model with bioluminescent imaging revealed that CRK knockdown significantly attenuated not only tumor volume but also the number of circulating tumor cells, resulted in a complete abrogation of metastasis. Taken together, this evidence uncovered essential roles of CRK in invasive bladder cancer through the hepatocyte growth factor/c‐Met/CRK feedback loop for epithelial–mesenchymal transition induction. Thus, CRK might be a potent molecular target in bladder cancer, particularly for preventing metastasis, leading to the resolution of clinically longstanding critical issues.     

Effects of neuregulins on invasion and metastasis of non-overexpression ErbB2 breast cancer cells

Objective: To explore the effects of neuregulins on ErbB2 receptor signal transduction pathway activation, and invasion and metastasis of non-overexpression ErbB2 breast cancer cell MDA-MB-231. Methods: The expressions of neuregulin were detected by immunocytochemistry and Western blot. MDA-MB-231 cells were treated with ErbB2 kinase inhibitor AG825. Proliferations were measured with MTT assay. Invasion and metastasis of MDA-ME-231 cells were evaluated with transwell chamber. The enzyme activities of MMP-2 and MMP-9 were detected by gelatin zymography. The expressions of MMP-2 and HIF-1α were detected by Western blot.Results: MDA-MB-231 cells expressed a relatively higher level of neuregulin. In Western blot, the positive reaction band was found at 44KD which coincides with the molecular weight of NRG. When MDA-MB-231 cells were treated with AG825, the proliferation was inhibited in a time-dose-dependent manner (P＜0.01), invasion and metastasis were also depressed (P＜0.05). The enzyme activities of MMP-2 and MMP-9 were lower (P＜0.05). The expression levels of MMP-2 and HIF-1α were decreased (P＜0.05).Conclusion: Our study indicates that neuregulins are synthesized in MDA-MB-231 cells as transmembrane proteins, neuregulins could activate ErbB2 receptor signal transduction pathway by autocrine or paracrine secretion, and induce invasion and metastasis of MDA-MB-231 cells.     

Silencing circular RNA UVRAG inhibits bladder cancer growth and metastasis by targeting the microRNA‐223/fibroblast growth factor receptor 2 axis

Circular RNA UVRAG (circUVRAG), a type of non‐coding RNA, is derived and cyclized by part of the exon from the UVRAG gene. However, the role of circUVRAG in bladder cancer (BLCA) has not been reported. The purpose of the present study was therefore to characterize the role of circUVRAG in BLCA. Bioinformatics analysis showed interactive relationships among circUVRAG, microRNA‐223 (miR‐223), and fibroblast growth factor receptor 2 (FGFR2). Quantitative real‐time PCR was used to detect the expression of circUVRAG in BLCA cell lines. UM‐UC‐3 cells were stably transfected with siRNA against circUVRAG, and cell proliferation and migration ability were tested using the CCK8 assay, clone formation, and Transwell assays in vitro. Tumor xenograft formation and metastasis were determined using nude mice. Fluorescence in situ hybridization was used to confirm the subcellular localization of circUVRAG, and the luciferase reporter assay was used to confirm the relationships among circUVRAG, miR‐223, and FGFR2. Results showed that circUVRAG was upregulated in BLCA cell lines. Downregulation of circUVRAG expression suppressed proliferation and metastasis both in vitro and in vivo. Downregulation of circUVRAG suppressed FGFR2 expression by “sponging” miR‐223, which was confirmed by rescue experiments and luciferase reporter assay. Overall, the results showed that downregulation of circUVRAG suppressed the aggressive biological phenotype of BLCA. Taken together, silencing circular RNA UVRAG inhibited bladder cancer growth and metastasis by targeting the miR‐223/FGFR2 axis, which may provide a potential biomarker and therapeutic target for the management of BLCA.     

Trastuzumab-induced recruitment of Csk-homologous kinase (CHK) to ErbB2 receptor is associated with ErbB2-Y1248 phosphorylation and ErbB2 degradation to mediate cell growth inhibition

The inhibitory effect of trastuzumab, a humanized monoclonal antibody directed against the extracellular domain of ErbB2, is associated with its ability to induce ErbB2-Y1248 phosphorylation, and the status of phosphorylated ErbB2-Y1248 (ErbB2-pY1248) may correlate with the sensitivity of breast cancers to trastuzumab. The mechanisms of which remain unclear. Here, we show that binding of trastuzumab to ErbB2 activates ErbB2 kinase activity and enhances ErbB2-Y1248 phosphorylation in trastuzumab-sensitive breast cancer cells. This in turn increases the interaction between ErbB2 and non-receptor Csk-homologous kinase (CHK), leading to growth inhibition of breast cancer cells. Overexpression of CHK mimics trastuzumab treatment to mediate ErbB2-Y1248 phosphorylation, Akt downregulation, and growth inhibition of trastuzumab-sensitive breast cancer cells. CHK overexpression combined with trastuzumab exerts an additive effect on cell growth inhibition. We further demonstrate that positive ErbB2-pY1248 staining in ErbB2-positive breast cancer biopsies correlates with the increased trastuzumab response in trastuzumab neoadjuvant settings. Collectively, this study highlights an important role for ErbB2-pY1248 in mediating trastuzumab-induced growth inhibition and trastuzumab-induced interactions between CHK and ErbB2-pY1248 is identified as a novel mechanism of action that mediates the growth inhibition of breast cancer cells. The novel mechanistic insights into trastuzumab action revealed by this study may impact the design of next generation of therapeutic monoclonal antibodies targeting receptor tyrosine kinases, as well as open new avenues to identify novel targets for the treatment of ErbB2-positive cancers.     

慢病毒介导NDRG2基因过表达抑制人膀胱癌T24细胞的侵袭和迁移

目的： 观察N-Myc下游调节基因-2（N-Myc downstream-regulated gene 2, NDRG2）过表达对人膀胱癌T24细胞体外侵袭和迁移的影响。 方法： 采用携带NDRG2基因的慢病毒Lenti-NDRG2感染T24细胞,构建稳定过表达NDRG2的细胞株。Western blotting检测T24细胞中NDRG2、基质金属蛋白酶（matrix metalloproteinase,MMP）-2和MMP-9的表达,Transwell体外迁移和侵袭实验观察过表达NDRG2对T24细胞体外迁移和侵袭的影响。 结果： 建立了稳定过表达NDRG2的T24细胞株。与Lenti-Lacz组和空白对照组相比,Lenti-NDRG2组NDRG2蛋白的表达\[(30.1±1.27) vs (9.9±1.24)、(8.2±1.28), P<001\]明显提高;Lenti-NDRG2组MMP-2 \[(13.5±1.32) vs (30.7±1.29)、(28.8±1.30), 均P<0.01\]和MMP-9 \[(11.7±127) vs (25.2±1.28)、(26.4±1.31), 均P<0.01\]的表达明显降低;Lenti-NDRG2组T24细胞的侵袭细胞数\[(18.1±3.4) vs (88.5±4.2)、(90.2±4.1)个,均P<0.01\]和迁移细胞数\[(20.1±3.5) vs (109.4±5.6)、(113.0±4.9)个,均P<0.01\]明显减少。 结论： 慢病毒介导的NDRG2基因过表达可能通过降低MMP-2和MMP-9的表达而抑制人膀胱癌T24细胞的转移与侵袭。     

Effective suppression of breast tumor growth by an anti-EGFR/ErbB2 bispecific antibody

Despite the effectiveness of the anti-ErbB2 humanized antibody trastuzumab, less than 35% of patients with ErbB2-overexpressing breast cancer respond to the treatment. Here we engineered an anti-EGFR/ErbB2 bispecific antibody (TC-BsAb) using trastuzumab and cetuximab, an anti-EGFR chimeric antibody. TC-BsAb treatment led to internalization of both EGFR and ErbB2, whereas trastuzumab and cetuximab, either alone or in combination, failed to induce ErbB2 internalization. Both in vitro and in vivo experiments indicated that TC-BsAb was significantly more potent in inhibiting the growth of breast cancer cell lines than trastuzumab, cetuximab, and trastuzumab plus cetuximab, suggesting its potential use for treating breast cancer.     

Heregulin-induced activation of ErbB3 by EGFR tyrosine kinase activity promotes tumor growth and metastasis in melanoma cells

ErbB3 receptor tyrosine kinase has been shown to induce tumor progression in several types of cancer through heterodimerization with ErbB2. However, the role of ErbB3 and its ligand heregulin (HRG) in tumor metastasis remains poorly understood. In the present study, we tried to clarify their contributions to the metastasis of ErbB3-overexpressing B16-BL6 melanoma cells. Stimulation with HRG induced phosphorylation of ErbB3 and metastatic properties including MMP-9 expression, invasion, adhesion and experimental lung metastasis in vivo. These cellular responses were blocked by inhibiting the tyrosine kinase activity of EGFR with PD153035. In addition, phosphorylation of EGFR was rapidly induced by HRG, suggesting that EGFR is a possible heterodimeric counterpart of ErbB3. RNA interference demonstrated that subcutaneous tumor growth and angiogenesis was attenuated by inactivation of ErbB3 in cancer cells. Although experimental pulmonary metastasis was not affected by the knockdown of ErbB3, spontaneous metastasis was, even when primary tumors in the foot pad were amputated at a similar size. These results indicate that HRG-induced activation of ErbB3 via EGFR promotes tumor growth and metastasis of melanoma cells.     

A feedback loop between BEX2 and ErbB2 mediated by c-Jun signaling in breast cancer

BEX2 is a member of brain expressed X-linked gene family that is differentially expressed in primary breast tumors. We have previously demonstrated that BEX2 expression protects breast cancer cells against mitochondrial apoptosis and G1 cell cycle arrest. In addition, we have shown that BEX2 is a c-Jun target gene and, in turn, regulates the phosphorylation of c-Jun in breast cancer cells. In our study, we investigated BEX2 protein expression in a tissue microarray cohort of 225 breast tissue samples with known clinical, pathological and biomarker information. We observed that BEX2 protein was overexpressed in ～50% of malignant breast tumors compared to only 7% of benign breast samples. Notably, BEX2 positive tumors identified a subset of breast cancers with the overexpression of ErbB2 and phosphorylated c-Jun proteins. Furthermore, using in vitro models, we demonstrated that the mechanism of this association is a functional feedback loop involving ErbB2, c-Jun and BEX2 in breast cancer cells. In this feedback loop, ErbB2 overexpression results in an induction of c-Jun and BEX2 expression. Importantly, ErbB2 induction of BEX2 expression was abrogated by a dominant-negative mutant of c-Jun, suggesting that this effect was mediated through the regulation of c-Jun signaling. In turn, the overexpression of BEX2 led to an increase in both c-Jun-mediated induction of ErbB2 and c-Jun binding to the ErbB2 promoter in MCF-7 cells. Our study suggests that BEX2 protein is overexpressed in approximately half of breast cancers and has a positive feedback loop with ErbB2 mediated by c-Jun signaling in breast cancer cells.     

ErbB2／Grb2／mTOR通路在胃癌发生发展中的作用

目的：检测ErbB2／neu、Grb2和mTOR胃癌中的表达并探讨ErbB2／Grb2／mTOR通路在胃癌发生发展中的作用。方法：构建含有1072例胃癌的组织芯片，利用免疫组化检测ErbB2／neu、Grb2和mTOR在胃癌中的表达。结果：ErbB2／neu、Grb2和mTOR在胃癌中的表达率分别为30．2％、47．5％和50．8％。ErbB2／neu和Grb2的过度表达与年龄（〉60岁）、肿瘤部位、肿瘤类型和高分化相关（P〈0．01）；mTOR的过度表达与肿瘤部位、肿瘤类型、高分化、T分期和TNM分期相关（P〈0．05）。Spearman相关性检验显示，3个蛋白两两之间存在显著相关（P〈0．001）。单因素生存分析表明，Grb2和mTOR与预后有关（P=0．0067，P=0．0001）；而在Cox回归多因素分析中，roTOR与预后有关（P=0．046）。结论：ErbB2／Grb2／mTOR通路在胃癌的发生发展中起到极其重要的作用，mTOR还可能作为胃癌患者预后的独立指标。3个蛋白可以作为胃癌治疗的靶点，继而为胃癌的治疗开拓新的思路。     

Exosomes enriched in stemness/metastatic-related mRNAS promote oncogenic potential in breast cancer

Cancer cells efficiently transfer exosome contents (essentially mRNAs and microRNAs) to other cell types, modifying immune responses, cell growth, angiogenesis and metastasis. Here we analyzed the exosomes release by breast tumor cells with different capacities of stemness/metastasis based on CXCR4 expression, and evaluated their capacity to generate oncogenic features in recipient cells. Breast cancer cells overexpressing CXCR4 showed an increase in stemness-related markers, and in proliferation, migration and invasion capacities. Furthermore, recipient cells treated with exosomes from CXCR4-cells showed increased in the same abilities. Moreover, inoculation of CXCR4-cell-derived exosomes in immunocompromised mice stimulated primary tumor growth and metastatic potential. Comparison of nucleic acids contained into exosomes isolated from patients revealed a “stemness and metastatic” signature in exosomes of patients with worse prognosis. Finally, our data supported the view that cancer cells with stem-like properties show concomitant metastatic behavior, and their exosomes stimulate tumor progression and metastasis. Exosomes-derived nucleic acids from plasma of breast cancer patients are suitable markers in the prognosis of such patients.     

Exosomes in development,metastasis and drug resistance of breast cancer

Transport through the cell membrane can be divided into active, passive and vesicular types (exosomes). Exosomes are nano‐sized vesicles released by a variety of cells. Emerging evidence shows that exosomes play a critical role in cancers. Exosomes mediate communication between stroma and cancer cells through the transfer of nucleic acid and proteins. It is demonstrated that the contents and the quantity of exosomes will change after occurrence of cancers. Over the last decade, growing attention has been paid to the role of exosomes in the development of breast cancer, the most life‐threatening cancer in women. Breast cancer could induce salivary glands to secret specific exosomes, which could be used as biomarkers in the diagnosis of early breast cancer. Exosome‐delivered nucleic acid and proteins partly facilitate the tumorigenesis, metastasis and resistance of breast cancer. Exosomes could also transmit anti‐cancer drugs outside breast cancer cells, therefore leading to drug resistance. However, exosomes are effective tools for transportation of anti‐cancer drugs with lower immunogenicity and toxicity. This is a promising way to establish a drug delivery system.     

Dominant negative knockout of p53 abolishes ErbB2-dependent apoptosis and permits growth acceleration in human breast cancer cells

We previously reported that the ErbB2 oncoprotein prolongs and amplifies growth factor signalling by impairing ligand-dependent downregulation of hetero-oligomerised epidermal growth factor receptors. Here we show that treatment of A431 cells with different epidermal growth factor receptor ligands can cause growth inhibition to an extent paralleling ErbB2 tyrosine phosphorylation. To determine whether such growth inhibition signifies an interaction between the cell cycle machinery and ErbB2-dependent alterations of cell signalling kinetics, we used MCF7 breast cancer cells (which express wild-type p53) to create transient and stable ErbB2 transfectants (MCF7-B2). Compared with parental cells, MCF7-B2 cells are characterised by upregulation of p53, p21(WAF) and Myc, downregulation of Bcl2, and apoptosis. In contrast, MCF7-B2 cells co-transfected with dominant negative p53 (MCF7-B2/Delta p53) exhibit reduced apoptosis and enhanced growth relative to both parental MCF7-B2 and control cells. These data imply that wild-type p53 limits survival of ErbB2-overexpressing breast cancer cells, and suggest that signals of varying length and/or intensity may evoke different cell outcomes depending upon the integrity of cell cycle control genes. We submit that acquisition of cell cycle control defects may play a permissive role in ErbB2 upregulation, and that the ErbB2 overexpression phenotype may in turn select for the survival of cells with p53 mutations or other tumour suppressor gene defects.     

Inhibition of heregulin mediated MCF-7 breast cancer cell growth by the ErbB3 binding protein EBP1

The ErbB2/3 heterodimer plays a critical role in breast cancer genesis and progression. EBP1, an ErbB3 binding protein, inhibits breast cancer growth but its effects on ErbB3 ligand mediated signal transduction or ErbB receptors is not known. We report here that ectopic expression of EBP1 in MCF-7 and AU565 breast cancer cell lines inhibited HRG-induced proliferation. ErbB2 protein levels were substantially decreased in EBP1 transfectants, while ErbB3 levels were unchanged. HRG-induced AKT activation was attenuated in EBP1 stable transfectants and transfection of a constitutively activated AKT partially restored the growth response to HRG. Down-regulation of EBP1 expression in MCF-7 cells by shRNA resulted in increased cell growth in response to HRG and increased cyclin D1 and ErbB2 expression. These results suggest that EBP1, by down-regulating ErbB signal transduction, attentuates HRG-mediated growth of breast cancer cells.     

表皮生长因子受体3在乳腺癌中的研究进展

表皮因子受体3(ErbB3/HER3)是表皮生长因子跨膜受体家族的成员之一。近年来证实ErbB3/HER3与乳腺癌的发病、复发转移、化疗以及内分泌治疗的疗效密切相关,已成为非常有前景的治疗候选靶点。本文简要综述近年来ErbB3/HER3在乳腺癌中的研究进展。     

Wnt5b‐associated exosomes promote cancer cell migration and proliferation

Wnt5b is a member of the same family of proteins as Wnt5a, the overexpression of which is associated with cancer aggressiveness. Wnt5b is also suggested to be involved in cancer progression, however, details remain unclarified. We analyzed the biochemical properties of purified Wnt5b and the mode of secretion of Wnt5b by cancer cells. Wnt5b was glycosylated at three asparagine residues and lipidated at one serine residue, and these post‐translational modifications of Wnt5b were essential for secretion. Purified Wnt5b showed Dvl2 phosphorylation and Rac activation abilities to a similar extent as Wnt5a. In cultured‐cell conditioned medium, Wnt5b was detected in supernatant or precipitation fractions that were separated by centrifugation at 100 000 g. In PANC‐1 pancreatic cancer cells, 55% of secreted endogenous Wnt5b was associated with exosomes. Exosomes from wild‐type PANC‐1 cells, but not those from Wnt5b‐knockout PANC‐1 cells, activated Wnt5b signaling in CHO cells and stimulated migration and proliferation of A549 lung adenocarcinoma cells, suggesting that endogenous, Wnt5b‐associated exosomes are active. The exosomes were taken up by CHO cells and immunoelectron microscopy revealed that Wnt5b is indeed associated with exosomes. In Caco‐2 colon cancer cells, most Wnt5b was recovered in precipitation fractions when Wnt5b was ectopically expressed (Caco‐2/Wnt5b cells). Knockdown of TSG101, an exosome marker, decreased the secretion of Wnt5b‐associated exosomes from Caco‐2/Wnt5b cells and inhibited Wnt5b‐dependent cell proliferation. Exosomes secreted from Caco‐2/Wnt5b cells stimulated migration and proliferation of A549 cells. These results suggest that Wnt5b‐associated exosomes promote cancer cell migration and proliferation in a paracrine manner.     

Expression of Aggrus/podoplanin in bladder cancer and its role in pulmonary metastasis

Platelet aggregation‐inducing factor Aggrus, also known as podoplanin, is associated with tumor malignancy by promoting hematogenous metastasis. Aggrus overexpression has been reported in some tumor tissues including lung, esophagus, head and neck and brain. We here found the frequent upregulation of aggrus mRNA in urinary bladder cancers using cancer tissue panels from various organs. Immunohistochemical analysis confirmed Aggrus protein expression in urinary bladder cancers and suggested a positive correlation between Aggrus expression and metastatic tendency in bladder cancers. Endogenous expression of Aggrus protein on the cell surface was found in the mouse bladder cancer MBT‐2 cell line and human bladder cancer SCaBER cell lines. Knockdown of Aggrus expression in MBT‐2 cells decreased their ability to induce platelet aggregation and form pulmonary metastasis in syngeneic mouse models. Knockdown of Aggrus expression in the human bladder cancer SCaBER cells also attenuated their ability to induce platelet aggregation and form pulmonary metastasis in mice. Moreover, pulmonary metastasis of SCaBER cells was prevented by prior administration of our generated anti‐Aggrus neutralizing monoclonal antibodies by attenuating their retention in lung. These results indicate that Aggrus plays an important role in bladder cancer metastasis. Thus, anti‐Aggrus neutralizing antibodies would be useful for the prevention of hematogenous metastasis of Aggrus‐positive bladder cancer.     

外泌体在胃癌转移中作用机制的研究进展

胃癌是发病率高且进展较快的消化道恶性肿瘤之一。随着手术、化疗、靶向治疗等多种治疗方法的不断进步,胃癌患者的5年生存率较过去有所改善,但由于胃癌早期缺乏有效的诊断方法,多数患者在确诊时往往已发生转移,预后较差。因此,对胃癌转移机制的探寻始终是胃癌研究领域的热点之一。外泌体是一种可以传递蛋白质、核酸等多种分子、实现细胞间信息交流的胞外囊泡。外泌体运载的分子参与了胃癌的转移过程,并且可能成为诊断胃癌的新型分子标志物,为胃癌的精准治疗提供了新方向。本文就外泌体在胃癌转移中的作用及机制进行综述。     

The oncogenic receptor ErbB2 modulates gemcitabine and irinotecan/SN-38 chemoresistance of human pancreatic cancer cells via hCNT1 transporter and multidrug-resistance associated protein MRP-2

Pancreatic adenocarcinoma (PDAC) is one of the most deadly cancers because of a lack of early diagnotic markers and efficient therapeutics. The fluorinated analog of deoxycytidine, gemcitabine and emerging FOLFIRINOX protocol (5-fluorouracil (5-FU), irinotecan/SN-38, oxaliplatin and leucovorin) are the main chemotherapies to treat PDAC. The ErbB2/HER2 oncogenic receptor is commonly overexpressed in PDAC. In this context, we aimed to decipher the ErbB2-mediated mechanisms of chemoresistance to the two main chemotherapy protocols used to treat PDAC.ErbB2 knocking down (KD) in CAPAN-1 and CAPAN-2 cells led to an increased sensitivity to gemcitabine and an increased resistance to irinotecan/SN-38 both in vitro and in vivo (subcuteanous xenografts) This was correlated to an increase of hCNT1 and hCNT3 transporters and ABCG2, MRP1 and MRP2 ATP-binding cassette transporters expression and resistance to cell death. We also show that MRP2 is repressed following activation of JNK, Erk1/2 and NF-κB pathways by ErbB2. Finally, in datasets of human PDAC samples, ErbB2 and MRP2 expression was conversely correlated. Altogether, we propose that ErbB2 mediates several intracellular mechanisms linked to PDAC cell chemoresistance that may represent potential targets in order to ameliorate chemotherapy response and allow stratification of patients eligible for either gemcitabine or FOLFIRINOX treatment.