肝细胞生长因子受体原癌基因c-Met mRNA在鼻咽癌中的表达及意义

Objective： To explore the expression of c-Met mRNA in nasopharyngeal carcinomas （NPC） and its relation with clinical biological behavior. Methods： In situ hybridisation was used to detect mRNA expression of c-Met in 15 cases of non-tumor nasopharyngeal （NP）, 55 cases of NPC. Results： The positive rates of c-Met mRNA in NP and NPC cells were 13.3% （2/15） and 61.8% （34/55） respectively. The expression of c-Met mRNA was significantly correlated with lymph node metastasis, local invasion （skull base erosion）, and clinical stage. In cases with cervical lymph node metastasis, local invasion, and clinical stage III and IV （UICC）, the positive rates of expression of c-Met mRNA were significantly higher than that in those without the conditions mentioned above （P 〈 0.05 or P 〈 0.01）. But it was not significantly correlated with age, gender, histologic grade, and cranial nerve palsy （P 〉 0.05）. Conclusion： The abnormal expression of c-Met gene was well correlated with the biological behavior of metastasis and invasion. To detection the expression of c-Met mRNA could serve as an important index to estimate the prognosis of NPC. C-Met may be a new diagnostic/therapeutic target of NPC.     

Tumor-stromal cell interaction under hypoxia increases the invasiveness of pancreatic cancer cells through the hepatocyte growth factor/c-Met pathway

The hypoxic environment in tumor is reported to play an important role in pancreatic cancer progression. The interaction between stromal and cancer cells also contributes to the malignant behavior of pancreatic cancer. In the present study, we investigated whether hypoxic stimulation affects stromal as well as pancreatic cancer cells. Our findings demonstrated that hypoxia remarkably elevated the HIF-1alpha expression in both pancreatic cancer (PK8) and fibroblast cells (MRC5). Hypoxic stimulation accelerated the invasive activity of PK8 cells, and invasiveness was thus further accelerated when the hypoxic PK8 cells were cultured with conditioned medium prepared from hypoxic MRC5 cells (hypoxic conditioned medium). MMP-2, MMP-7, MT1-MMP and c-Met expressions were increased in PK8 cells under hypoxia. Hypoxic stimulation also increased the hepatocyte growth factor (HGF) secretion from MRC5 cells, which led to an elevation of c-Met phosphorylation in PK8 cells. Conversely, the elevated cancer invasion, MMP activity and c-Met phosphorylation of PK8 cells were reduced by the removal of HGF from hypoxic conditioned medium. In immunohistochemical study, the HIF-1alpha expression was observed in surrounding stromal as well as pancreatic cancer cells, thus indicating hypoxia exists in both of cancer and stromal cells. Moreover, the stromal HGF expression was found to significantly correlate with not only the stromal HIF-1alpha expression but also the c-Met expression in cancer cells. These results indicate that the hypoxic environment within stromal as well as cancer cells activates the HGF/c-Met system, thereby contributing to the aggressive invasive features of pancreatic cancer.     

Radiation stimulates HGF receptor/c-Met expression that leads to amplifying cellular response to HGF stimulation via upregulated receptor tyrosine phosphorylation and MAP kinase activity in pancreatic cancer cells

Hepatocyte growth factor (HGF) is a stromal-derived cytokine that plays a crucial role in invasion and metastasis of tumor cells through the interaction with HGF receptor, c-Met, which is frequently overexpressed in pancreatic cancer. The present study was designed to investigate the change in HGF receptor and HGF-mediated signaling after irradiation in pancreatic cancer cells. Six cell lines from human pancreatic cancer were included in the study. Gamma-radiation was used for irradiation treatment. The changes in expression levels of c-Met were evaluated by immunoblot and confirmed morphologically by indirect immunofluorescence staining. Whether the resultant alteration in c-Met would cascade as biologically usable signals upon HGF ligation was traced by receptor tyrosine phosphorylation analysis and mitogen activated protein kinase (MAP kinase or MAPK) activity assay. The various biological responses to HGF (including cell proliferation, cell scattering, migration and invasion) were evaluated as well. We also used a 4-kringle antagonist of HGF, NK4, to block the HGF/c-Met signaling pathway. Both immunoblot and immunofluorescent analysis showed moderate increased expression of c-Met in 3 of 6 pancreatic cancer cell lines after irradiation. The actions seemed to be dose-responsible, which began at 3 hr and reached its peak value at 24 hr following irradiation. The radiation-increased expression of c-Met could transform into magnifying receptor tyrosine phosphorylation reaction and MAP kinase activity once the ligand was added, fairly corresponding with alteration in the receptor. Sequentially, the cellular responses to HGF, including scattering and invasion but not proliferation, were enhanced. Also, in the presence of HGF, the elevated receptor could help to recover the radiation-compromised cell migration. A recombinant HGF antagonist, NK4 could effectively block these aberrant effects activated by irradiation both in molecular and cellular levels, thus suggesting the deep involvement of the c-Met/HGF pathway in the enhanced malignant potential after irradiation. These results suggest that radiation may promote HGF-induced malignant biological behaviors of certain pancreatic cancer cells through the up-regulated HGF/c-Met signal pathway. Selectively targeted blockade of the HGF/c-Met pathway could help to abolish the enforced malignant behavior of tumor cells by irradiation and therefore may improve the efficacy of radiotherapy for pancreatic cancer.     

沉默FOXM1拮抗肝细胞生长因子对胃癌细胞SGC7901增殖、迁移和侵袭的诱导作用

目的:探索转录因子FOXM1在肝细胞生长因子(HGF)诱导胃癌细胞增殖、迁移和侵袭过程中的作用.方法:体外培养胃癌细胞SGC7901,根据不同处理将细胞分组:空白对照组、20 ng/ml HGF组、40 ng/ml HGF组、60 ng/ml HGF组、siRNA-scramble+HGF组、siRNA-FOXM1+HGF组.采用MTT法检测各组SGC7901细胞的增殖,Transwell法检测各组细胞的迁移和侵袭情况,qRT-PCR和Western blot法分别检测各组细胞中FOXM1 mRNA和蛋白水平.结果:与空白对照组相比,不同浓度HGF均能够促进胃癌细胞SGC7901增殖、迁移和侵袭,同时上调FOXM1的表达水平,并且呈浓度依赖性关系.沉默HOXM1表达能够明显抑制HGF对SGC7901细胞的增殖、迁移和侵袭的诱导作用.结论:HGF对胃癌细胞增殖、迁移和侵袭的诱导作用可能与上调FOXM1表达有关,沉默FOXM1表达能够抑制HGF的作用.     

HGF/ Met与甲状腺癌侵袭性的研究进展

HGF/Met系统相关分子的激活与多种肿瘤的发生、侵袭和转移相关。本文综述了其在甲状腺癌的研究近况。通过对肿瘤表达Met水平及其机制的探讨,对Met的激活与肿瘤移动、血管生成和炎症反应的分析,认为HGF/Met相关分子的研究将提高对甲状腺癌的诊治水平,同时也将深化对肿瘤侵袭机制的认识。     

Prognostic significance of c-Met expression in glioblastomas

BACKGROUD:

The authors investigated whether expression of c‐Met protein in glioblastomas is associated with overall survival and biologic features representing tumor invasiveness in patients with glioblastomas.

METHODS:

Paraffin‐embedded specimens of glioblastomas from 62 patients treated in a single institution were assessed by immunohistochemical (IHC) analysis of c‐Met expression. On the basis of the clinical data for these patients, the association between c‐Met expression and clinicobiologic features representing tumor invasiveness was analyzed.

RESULTS:

c‐Met overexpression was detected in 29.0% (18 of 62) of glioblastomas. In patients with c‐Met overexpression, the median survival was 11.7 months (95% confidence interval [95% CI], 9.9 months‐13.5 months), compared with a median survival of 14.3 months (95% CI, 7.6 months‐21.0 months) for patients whose tumors had no or little expression of c‐Met (P = .031). On the radiographic analysis, 9 of 18 patients (50%) with tumors overexpressing c‐Met demonstrated invasive and multifocal lesions on the initial magnetic resonance images, whereas only 9 of 44 patients (20.5%) with tumors that expressed no or little c‐Met demonstrated these features (P = .030). Using immunohistochemistry, we also found a significant association between c‐Met expression and matrix metalloproteinase‐2,‐9 (P = .020 and P = .013). Furthermore, Myc overexpression was found to be closely correlated with c‐Met overexpression on IHC analysis (P = .004).

CONCLUSIONS:

The authors suggest that c‐Met overexpression is associated with shorter survival time and poor treatment response in glioblastomas, the mechanism for which is elevated tumor invasiveness on the molecular and clinical phenotypes. This implies that more effective therapeutic strategies targeting c‐Met receptors may have important clinical implication. Cancer 2009. © 2008 American Cancer Society.     

Co-expression of hepatocyte growth factor and c-Met predicts peritoneal dissemination established by autocrine hepatocyte growth factor/c-Met signaling in gastric cancer

Epithelial-mesenchymal transition (EMT) promotes and facilitates migration and invasion of epithelial tumor cells. EMT is induced by factors such as hepatocyte growth factor (HGF). This study aimed to establish whether the HGF/c-Met pathway is associated with gastric cancer metastasis; especially peritoneal dissemination. HGF and c-Met expression and EMT-related molecules were evaluated using real-time PCR and immunohistochemistry. The role of the HGF/c-Met pathway in EMT and anoikis was determined, and kinase inhibitor SU11274 was tested for its ability to block HGF-induced biological effects. In HGF(-) /c-Met(+) gastric cancer cells, recombinant HGF promoted an EMT phenotype that was characterized by morphology, impaired E-cadherin and induction of vimentin. HGF promoted cell growth, invasiveness and migration and inhibition of anoikis. SU11274 blocked HGF-induced EMT and biological effects in vitro. In HGF(+) /c-Met(+) gastric cancer cells, HGF did not affect the biological outcome of EMT and anoikis, but SU11274 exerted the same inhibitory effects as in HGF(-) /c-Met(+) cells. In vivo, HGF(+) /c-Met(+) gastric cancer cells only established peritoneal dissemination and SU11274 inhibited tumor growth. Clinically, HGF expression was significantly correlated with c-Met expression in gastric cancer. Increased HGF and c-Met had a significant association with poor prognosis and predicted peritoneal dissemination. We demonstrated that the HGF/c-Met pathway induces EMT and inhibition of anoikis in gastric cancer cells. Co-expression of HGF and c-Met has the potential to promote peritoneal dissemination in gastric cancer. Blockade of the autocrine HGF/c-Met pathway could be clinically useful for the treatment of peritoneal dissemination in gastric cancer.     

Antisense-mediated reduction in thrombospondin-1 expression reduces cell motility in malignant glioma cells.

Thrombospondin-1 (TSP-1) is a multifunctional matrix protein implicated in cancer cell adhesion, migration, invasion, inhibition of angiogenesis and activation of latent transforming growth factor-beta. The involvement of TSP-1 in the motility of malignant glioma cells was investigated by transfection of TSP-1 complementary deoxyribonucleic acid (cDNA) sense and antisense expression vectors into the glioblastoma cell line T98G-G7 that secretes high amounts of TSP-1. TSP-1 production in the 3 antisense cDNA-transfected clones was significantly reduced to 51%, 43% and 47% compared to the host T98G-G7 cells. Motility of the 3 clones was evaluated by invasion assay and compared to the motility of host T98G-G7 cells and 2 sense-transfected clones. Migration of cells was significantly reduced in the 3 antisense-transfected clones with reduced TSP-1 production to 56%, 61% and 43% compared to the host T98G-G7 cells. The host T98G-G7 and another TSP-1-secreting A172 and YMG5 glioblastoma cells were also treated with a synthetic peptide, WSHWSPWSSCSVTCG, which includes 3 consecutive sequences of the adhesion sites in the TSP-1 molecule and with a control peptide. The synthetic peptide significantly inhibited the migration of T98G-G7 and A172 cells in a dose-related manner. Maximum inhibition of migration was achieved by 100 microg/ml of the peptide and the reduction of cell motility compared to untreated cells was 34.6 % and 53.9 %, respectively. On the other hand, the inhibition of migration by the peptide was minimal in YMG5 cells, which secretes a smaller amount of TSP-1 than T98G-G7 and A172 cells. These results suggest that TSP-1 secreted by malignant glioma cells is involved in the motility of glioma cells.     

Elevated hepatocyte growth factor expression as an autocrine c‐Met activation mechanism in acquired resistance to sorafenib in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and the third leading cause of cancer‐related deaths worldwide. Limitations in HCC treatment result due to poor prognosis and resistance against traditional radiotherapy and chemotherapies. The multikinase inhibitor sorafenib is the only FDA approved drug available for advanced HCC patients, and development of second‐line treatment options for patients who cannot tolerate or develop resistance to sorafenib is an urgent medical need. In this study, we established sorafenib‐resistant cells from Huh7 and Mahlavu cell lines by long‐term sorafenib exposure. Sorafenib‐resistant HCC cells acquired spindle‐shape morphology, upregulated mesenchymal markers, and showed significant increase in both migration and invasion abilities compared to their parental counterparts. Moreover, after long‐term sorafenib treatment, HCC cells showed induction of hepatocyte growth factor (HGF) synthesis and secretion along with increased levels of c‐Met kinase and its active phosphorylated form, indicating autocrine activation of HGF/c‐Met signaling. Importantly, the combined treatment of the resistant cells with c‐Met kinase inhibitor SU11274 and HGF neutralizing antibody significantly reversed the increased invasion ability of the cells. The combined treatment also significantly augmented sorafenib‐induced apoptosis, suggesting restoration of sorafenib sensitivity. These results describe, for the first time, compensatory upregulation of HGF synthesis leading to autocrine activation of HGF/c‐Met signaling as a novel cellular strategy in the acquisition of sorafenib resistance. Therefore, we suggest that combinatorial therapeutic strategies with HGF and c‐Met inhibitors comprise promising candidates for overcoming sorafenib resistance.     

Ganglioside GD3 induces convergence and synergism of adhesion and hepatocyte growth factor/Met signals in melanomas

Ganglioside GD3 is highly expressed in human melanomas and enhances malignant properties of melanomas, such as cell proliferation and invasion activity. In this study, we analyzed the effects of GD3 expression on cell signals triggered by hepatocyte growth factor (HGF)/Met interaction and by adhesion to collagen type I (CL-I). Although stimulation of melanoma N1 cells (GD3+ and GD3−) with either HGF or adhesion to CL-I did not show marked differences in the phosphorylation levels of Akt at Ser473 and Thr308 between two types of cells, simultaneous treatment resulted in definite and markedly increased activation of Akt in GD3+ cells. Similar increases were also shown in Erk1/2 phosphorylation levels with the costimulation in GD3+ cells. When resistance to induced apoptosis by H₂O₂ was examined, only GD3+ cells treated with both HGF and adhesion to CL-I showed clearly low percentages of dead cells compared with GD3− cells or GD3+ cells treated with either one of the stimulants. Cell growth measured by 5-ethynyl-2‘ deoxyuridine uptake also showed synergistic effects in GD3+ cells. These results suggested that GD3 plays a crucial role in the convergence of multiple signals, leading to the synergistic effects of those signals on malignant properties of melanomas.     

Inhibition of HGF/SF-induced breast cancer cell motility and invasion by the HGF/SF variant, NK4

NK4 is a variant form of HGF/SF, comprising the N-terminal and subsequent four kringle domains of mature HGF/SF. HGF/SF is a multifunctional cytokine that enhances the metastatic behaviour of tumour cells in vitro by stimulation of the c-met receptor tyrosine kinase and has been implicated in the development of tumour metastasis in vivo. The aims of this study were to further investigate the potential antagonistic effects of the recently described variant form of HGF/SF, NK4, on HGF/SF activity in breast cancer cells. All cell lines used expressed both the HGF/SF receptor gene and protein as shown by RT-PCR and Western blotting. NK4 inhibited HGF/SF-induced tumour cell invasion through an artificial basement membrane. Tumour cell motility and scattering induced by HGF/SF were also dramatically reduced by the inclusion of NK4. Immunoprecipitation studies revealed that NK4 inhibited the phosphorylation of the c-met receptor in response to HGF/SF. Treatment of these cells with NK4 alone did not have any significant effects on their metastatic behaviour. From this data we conclude that NK4 demonstrates significant antagonistic properties towards HGF/SF, inhibiting HGF/SF-stimulated breast tumour cell invasion, motility and migration. NK4 may therefore be of potential benefit in the development of anti-metastasis therapies.     

HGF诱导不同EGFR基因型非小细胞肺癌细胞对厄洛替尼的耐药

目的：探究肝细胞生长因子（hepatocyte growth factor,HGF） 体外诱导不同EGFR基因型非小细胞肺癌（non-small cell lung cancer,NSCLC）细胞对厄洛替尼的耐药及其可能的机制。方法：用HGF、厄洛替尼单独或联合处理人NSCLC细胞株PC9（EGFR突变型,敏感株）、H292（EGFR野生型,敏感株）、A549（EGFR野生型,原发性耐药株）,实验分为四组：C组（不加药对照组）、H组（HGF处理）、E组（厄洛替尼处理组）、HE组（HGF+厄洛替尼联合处理组）。MTT法检测其对细胞增殖的影响,流式细胞术检测其对细胞周期和凋亡的影响,Western blotting检测其对细胞中c-Met、EGFR、ErbB3及其磷酸化蛋白表达的影响。结果：厄洛替尼对3种细胞增殖抑制的作用均呈浓度依赖性,HGF处理能够缓解厄洛替尼对瘤细胞增殖的抑制作用。3种细胞的HE组凋亡率均显著低于E组（均P<0.05）。厄洛替尼阻滞3种细胞周期于G1期,对于H292、A549细胞,HE组G0/G1期比例显著低于E组（P<0.05）。HE组p-Met蛋白含量较E组显著升高（P<0.05）,而p-EGFR和p-ErbB3表达无显著差异（P>0.05）。结论：在体外,HGF能够诱导不同EGFR基因型NSCLC细胞株对厄洛替尼耐药,其机制可能与其诱导c-Met磷酸化活化有关。     

自分泌IGF-1/IGF-1R环路促进NK/T细胞淋巴瘤细胞株迁移和侵袭

目的 探讨IGF-1/IGF-1R信号通路对NK/T细胞淋巴瘤(NK/TCL)细胞株迁移和侵袭的作用及其调控机制.方法 采用反转录聚合酶链反应(RT-PCR)及免疫荧光技术检测IGF-1和IGF-1R的表达,Transwell技术观察NK/TCL细胞迁移和侵袭.酶联免疫吸附实验(ELISA)检测MMP-2、MMP-9及TIMP1水平.结果 NK/TCL细胞株SNK-1和SNK-6均表达IGF-1与IGF-1R,而健康人NK细胞不表达IGF-1R.IGF-1R抑制剂显著抑制SNK-1和SNK-6的迁移和侵袭.外源性IGF-1则促进细胞迁移及侵袭,而IGF-1R抑制剂能阻断该效应.IGF-1R下游相关激酶p38、PI3K及JNK的抑制剂均可降低细胞迁移能力.外源性IGF-1可上调MMP-2、MMP-9的分泌水平,IGF-1R抑制剂则抑制MMP-2、MMP-9的分泌.结论 NK/TCL细胞株中存在IGF-1/IGF-1R自分泌环路,并通过IGF-1/IGF-1R通路促进MMP-2、MMP-9分泌及IGF-1R下游p38、PI3K及JNK等激酶促进肿瘤细胞的迁移和侵袭.     

Ganglioside GD1a inhibits HGF-induced motility and scattering of cancer cells through suppression of tyrosine phosphorylation of c-Met.

We previously reported that ganglioside GD1a, which is highly expressed in poorly metastatic FBJ-S1 cells, inhibits the serum-induced motility of FBJ-LL cells and that the metastatic potential of FBJ-LL cells is completely suppressed by enforced GD1a expression (Hyuga et al., Int J Cancer 1999;83:685-91). We recently discovered that hepatocyte growth factor (HGF) induces FBJ-LL cell motility. In the present study, the HGF-induced motility of FBJ-S1 cells was found to be one-thirtieth that of FBJ-LL cells. This motility of GD1a-expressing transfectants, which were produced by transfection of FBJ-LL cells with GM2/GD2 synthase cDNA, decreased with increases in their GD1a expression and HGF induced almost no motility in GD1a-pretreated FBJ-LL cells, indicating that GD1a inhibits the HGF-induced motility of FBJ-LL cells. The expression of the HGF receptor c-Met on FBJ-S1 cells, FBJ-LL cells, transfectants and a mock-transfectant was almost the same. The level of tyrosine phosphorylation of c-Met after HGF stimulation in FBJ-S1 cells, GD1a-pretreated FBJ-LL cells and a GD1a-expressing transfectant was significantly lower than in FBJ-LL cells and a mock-transfectant. These findings suggested that GD1a inhibits the HGF-induced motility of FBJ-LL cells through suppression of tyrosine phosphorylation of c-Met. HepG2 cells, a human hepatoma cell line, were used to investigate whether GD1a interferes with other cancer cells expressing c-Met. HepG2 cells did not express GD1a. HGF induced cell scattering of HepG2 cells and the scattering was inhibited by pretreating the cells with GD1a. The c-Met in the cells was autophosphorylated by stimulation with HGF, but after treating the cells with GD1a, the HGF-induced autophosphorylation of c-Met was suppressed. These results suggest that GD1a acts as a negative regulator of c-Met in cancer cells.     

小鼠肾发育过程中肝细胞生长因子及其受体的表达

目的观察肝细胞生长因子（hepatocyte growth factor,HGF）及其受体（c-Met）在小鼠肾发育中的时空性表达,探讨其与肾发育的关系。方法采用免疫组织化学技术结合体视学方法对不同胚龄及生后日龄小鼠肾组织HGF和c-Met的表达及其含量变化进行系统观察和定量分析。结果HGF和c-Met在各期的肾小体、皮质肾小管及集合管均有表达,且随胚（日）龄增加在各期肾小体、皮质肾小管及集合管的表达是先增后减。结论推测HGF和c-Met可能对肾各结构的发育以及成熟肾的形态维持起重要作用。     

Expression of hepatocyte growth factor and its receptor c-Met in human pituitary adenomas

Hepatocyte growth factor (HGF) and its receptor c-Met have been known as key determinants of growth and angiogenesis in some brain tumors like gliomas, meningiomas, and schwannomas. But little is known about their expression in pituitary adenomas. In this study, the expression of HGF and c-Met in pituitary adenomas of different histology types was investigated by immunohistochemistry, and correlative analysis of their expression with microvessel density (MVD), Ki-67 expression, and other clinicopathologic factors was made. The results showed that the expression of HGF and c-Met exists in 98% (64 of 65) and 92% (60 of 65) pituitary adenomas, respectively, and co-expression of them existed in 91% (59 of 65) adenomas. HGF had significant correlation with MVD (Spearman''s correlation coefficient, r = .31, P = .01) and Ki-67 (r = .32, P = .01). c-Met had significant correlation with MVD (r = .30, P = .02) and Ki-67 (r = .38, P = .00). HGF and c-Met expression had no significant correlation with age or extrasellar extension. There were no significant differences in HGF and c-Met expression between pituitary adenomas of different histology types. The results indicate that HGF and c-Met are widely expressed in pituitary adenomas, and their expression correlates with MVD and Ki-67 expression.     

Interactions of glioma cells and extracellular matrix

Summary The communication between tumor cells and extracellular matrix (ECM) is responsible for clinically important features of malignant gliomas, such as cerebral invasion and leptomeningeal spread. The synthesis of ECM components, ECM-degrading activities and ECM receptors as well as the interaction between ECM components and their receptors represents the molecular basis for these processes. Recent studies have shown that proteases and integrins, the major group of ECM receptors, may be over-expressed by astrocytic tumor cells. Furthermore, integrins and the hyaluronate receptor CD44 have been found to be involved in adhesion and basement membrane invasion of glioma cells. Critical issues which are poorly understood so far include the ECM composition of the normal human brain and of brain tumors, the function of individual ECM components and receptors in a neuro-oncological context, and the molecular processes mediating the diffuse invasion of glioma cells into the brain.