STAT3 and MAPK in human lung cancer tissues and suppression of oncogenic growth by JAB and dominant negative STAT3

To search for the signaling events in lung carcinoma relevant to its tumorigenesis, we investigated the phosphorylation of MAPK and STAT3 in human lung carcinoma tissues and their paired normal tissues. Although relative amounts of MAPK levels differed among the cases examined, no clear difference in MAPK levels was observed between tumor tissues and their paired normal tissues. Of 79 cases examined, only 7 cases (8.9%) showed tumor-specific phosphorylation of MAPK, whereas 41 cases (52%) showed more than 2-fold lower levels of MAPK phosphorylation in tumor tissues. In contrast to MAPK, 42 cases (53%) showed tumor-specific increase in STAT3 expression. In addition, 15 cases (19%) showed tumor-specific increase of STAT3 phosphorylation and 51 cases (65%) had STAT3 phosphorylation proportional to its expression. Moreover, exogenous expression of either JAB or dominant negative STAT3 in lung carcinoma cell lines led to the suppression of STAT3 phosphorylation and the drastic reduction of anchorage- independent growth of the cells. Taken together, our results suggest that JAK-STAT3 signaling has a pivotal role for oncogenic growth of lung carcinoma cells.     

C-Cbl protein in human cancer tissues is frequently tyrosine phosphorylated in a tumor-specific manner

To search for the signaling pathway relevant to the tumorigenesis in human, we examined the expression and tyrosine phosphorylation of c-cbl proto-oncogene product, c-Cbl, in various human cancer cell lines and surgical specimens. In cells derived from human cancer, we found constitutive tyrosine phosphorylation of c-Cbl protein, whereas its phosphorylation was undetectable in control ECV304 cells. Expression and tyrosine phosphorylation of c-Cbl was also examined in various surgical specimens. Thirty-six surgical specimens obtained from human tumor tissues were studied: 9 gastric carcinomas, 10 colon carcinomas, 6 renal carcinomas, 2 hepatomas, 2 brain tumors, 2 uterus tumors, 1 breast carcinoma, 1 thyroid tumor, 1 bladder tumor and 2 lung carcinomas. We found tyrosine phosphorylation of c-Cbl protein in 12 cases (33%) of these tumor tissues in a tumor-specific manner. These results suggest the importance of c-Cbl signaling in tumorigenesis in human.     

Mitogen-activated protein kinase pathway-dependent tumor-specific survival signaling in melanoma cells through inactivation of the proapoptotic protein bad

Mitogen-activated protein kinase (MAPK) signaling regulates fundamental cellular functions including proliferation, differentiation, and survival. We have demonstrated previously that inhibiting MAPK signaling induces apoptosis in melanoma cells but not in normal melanocytes, suggesting that the MAPK pathway propagates essential survival signals in melanoma cells. Here, we report that the 90-kDa ribosomal S6 kinase (RSK), a downstream effector in the MAPK signaling cascade, phosphorylates and inactivates the Bcl-2 homology 3-only proapoptotic protein Bad, thereby mediating a MAPK-dependent tumor-specific survival signal in melanoma cells. The MAPK kinase (MEK)/extracellular signal-regulated kinase (ERK)/RSK MAPK signaling module is constitutively hyperactivated, and Bad is maintained in its inactive state by phosphorylation at Ser(75) in a MEK/ERK/RSK-dependent manner in melanoma cells. In contrast, in normal melanocytes, Bad is highly phosphorylated at multiple residues (Ser(75), Ser(99), and Ser(118)) in a MAPK pathway-independent manner. Importantly, ectopic expression of a constitutively activated RSK mutant abrogates Bad activation and renders melanoma cells resistant to apoptosis induced by a MEK inhibitor. Furthermore, overexpressing alanine-substituted (S75A) Bad further sensitizes melanoma cells to MEK inhibitor-induced apoptosis. Our results suggest that the MAPK pathway mediates melanoma-specific survival signaling by differentially regulating RSK-mediated phosphorylation of the proapoptotic protein Bad and may present potentially selective therapeutic targets for the treatment of melanomas.     

Somatic mutations of ERBB2 kinase domain in gastric, colorectal, and breast carcinomas.

PURPOSE: Recent reports revealed that the kinase domain of the ERBB2 gene is somatically mutated in lung adenocarcinoma, suggesting the mutated ERBB2 gene as an oncogene in human cancers. However, because previous reports focused the mutational search of ERBB2 primarily on lung cancers, the data on ERBB2 mutations in other types of human cancers have been largely unknown. EXPERIMENTAL DESIGN: Here, we did a mutational analysis of the ERBB2 kinase domain by PCR single-strand conformational polymorphism assay in gastric, colorectal, and breast carcinoma tissues. RESULTS: We detected the ERBB2 kinase domain mutations in 9 of 180 gastric carcinomas (5.0%), in 3 of 104 colorectal carcinomas (2.9%), and in 4 of 94 breast carcinomas (4.3%). All of the detected ERBB2 mutations except for one in-frame deletion mutation were missense mutations. Of the 16 ERBB2 mutations detected, 4 affected Val777 in the exon 20 site, and 3 affected Leu755 in the exon 19 site. We simultaneously analyzed the somatic mutations of EGFR, K-RAS, PIK3CA, and BRAF genes in the 16 samples with ERBB2 mutations, and found that all of the 3 colorectal carcinoma samples with ERBB2 mutations harbored K-RAS mutations. CONCLUSION: This study showed that in addition to lung adenocarcinomas, ERBB2 kinase domain mutation occurs in other common human cancers such as gastric, breast, and colorectal cancers, and suggested that alterations of ERBB2-mediated signaling pathway by ERBB2 mutations alone or together with K-RAS mutations may contribute to the development of human cancers.     

Cross‐signaling among phosphinositide‐3 kinase,mitogen‐activated protein kinase and sonic hedgehog pathways exists in esophageal cancer

The hedgehog (Hh) signaling pathway is essential for the development of tissues and organs. Hyperactive Hh signaling has been implicated in many gastric cancers, including esophageal cancer. However, the interaction between the Hh pathway and other potential signaling pathways in primary esophageal tumorigenesis has not been well investigated. In our study, we found that esophageal cancer cells expressed Hh signaling molecules and that the hyperexpression of Hh target genes was related to protein kinase B (AKT) activation but not extracellular signal‐regulated kinase activation. We analyzed the relationship between Gli1 or p‐AKT expression and clinicopathological features in esophageal carcinoma samples and found that Gli1 expression was associated with lymph vessel invasion (p = 0.016), blood vessel invasion (p = 0.006) and a poor prognosis (p = 0.003), and p‐AKT expression was associated with blood vessel invasion (p = 0.031) and a poor prognosis (p = 0.031). We also studied the relationship between Hh and phosphinositide‐3 kinase (PI3K)/AKT or mitogen‐activated protein kinase (MAPK) signaling pathways in both TE‐1 and TE‐10 cell lines. We found that the PI3K/AKT pathway played a critical role in Hh signaling after stimulation with epidermal growth factor, Gβγ and N‐Shh. Conversely, PI3K/AKT and MAPK signaling cooperated with the Shh pathway to promote esophageal cancer cell survival and proliferation. The results from esophageal cancer cells shed light on the significance of Hh signaling in esophageal tumor formation and the crosstalk of the Hh pathway with other basic signaling pathways, which is consistent with that observed in human tumor samples.     

BRCA1-associated protein induced proliferation and migration of gastric cancer cells through MAPK pathway

BRCA1-associated protein (BRAP) was first found to bind to the nuclear localization signal motifs of BRCA1. In this study, we investigated the role of BRAP in gastric cancer. The cancer genome atlas(TCGA) data were obtained from UALCAN. We downregulated and upregulated the level of BRAP in gastric cancer cells by transfection with shRNAs and plasmids. Then, we evaluated the expression of BRAP by qRT-PCR and investigated the expression of important proteins by Western blot analysis. We conducted a microarray analysis to identify the function of BRAP in gastric cancer cells. Then, we investigated the effect of BRAP on proliferation and migration by CCK-8 assays, colony formation assays, wound healing assays and an extreme limiting dilution analysis. The analysis of TCGA data showed that BRAP was significantly overexpressed in gastric cancer tissues compared to that in normal gastric mucosal tissues (P < 0.001). A hybridization-based microarray assay was used to analyze MGC-803 cells and BRAP-downregulated MGC-803 cells. We found 22,199 protein-coding RNAs that were differentially expressed. The genes in the two groups were analyzed with the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, and both the focal adhesion and MAPK pathways were significantly enriched. The results of Cell Counting Kit-8(CCK-8) assays, colony formation assays, wound healing assays and the extreme limiting dilution analysis showed that the knockdown of BRAP reduced gastric cancer cell proliferation and migration and inhibited the process of epithelial-mesenehymal transition (EMT). The overexpression of BRAP induced gastric cancer cell proliferation, migration and the process of EMT. To verify the function of the mitogen-activated protein kinase (MAPK) signaling pathway, we performed a Western blot analysis. The results showed that the downregulation of BRAP decreased the levels of p-ERK and p-Raf1, thereby decreasing the activity of the MAPK signaling pathway. The use of Honokiol increased the levels of p-ERK and p-Raf1, rescuing the function of BRAP downregulation in the MAPK pathway. Xenograft tumor transplantation experiments in nude mice further confirmed the role of BRAP in gastric cancer progression and metastasis.     

Vascular endothelial growth factor (VEGF) enhances gastric carcinoma invasiveness via integrin alpha(v)beta6

Integrins play an important role in tumor metastasis induced by vascular endothelial growth factor (VEGF). However, in the case of gastric cancer, the precise role of VEGF in regulating integrin αvβ6 is unclear. In this study, we found that most of the αvβ6 integrin-positive gastric cancer tissues were also VEGF-positive. Furthermore, when gastric carcinoma cells were exposed to VEGF, expression of αvβ6 integrin was up-regulated and the extracellular signal-related kinase (ERK) pathway was activated. When integrin αvβ6 was blocked either with β6 siRNA or anti-αvβ6 antibody, the migration of tumor cells normally induced by VEGF, as well as the activation of ERK, were markedly inhibited. Blocking the ERK signaling pathway significantly inhibited cell mobility. Taken together, the data suggest that VEGF is critical to the invasive process in human gastric cancer and that this occurs via up-regulation of integrin αvβ6 expression and activation of ERK.     

TS、ERCC1和DNA-PKcs在大肠癌组织中的表达及临床意义

[目的]探讨TS、ERCC1和DNA-PKcs在大肠癌组织中的表达及其临床意义.[方法]将133例大肠癌标本与17例正常大肠组织标本构建成组织芯片,应用免疫组化SP法检测TS、ERCC1和DNA-PKcs在大肠癌芯片中的表达,并分析其与大肠癌临床病理特征的关系.[结果]TS在大肠癌组织中的表达显著高于正常大肠组织(P＜0.05),而ERCC1、DNA-PKcs在大肠癌组织中的表达与正常大肠组织无明显差异(P＞0.05).TS、ERCC1和DNA-PKcs的表达均与淋巴结转移和Dukes分期有关(P＜0.05).ERCC1和DNA-PKcs、TS和ERCC1表达间均呈明显正相关(P＜0.01).[结论]检测TS、ERCC1和DNA-PKcs在大肠癌中的表达对预测大肠癌的发生、发展有一定意义.     

Differential regulation of MAP kinase cascade in human colorectal tumorigenesis

Hyper-activation of mitogen-activated protein kinase (MAPK) has recently been reported in several human cancers and activation of MAPK in those cancers may be associated with carcinogenesis through aberrant cell proliferation. To understand the roles of the MAPK pathway in colorectal tumorigenesis, we examined the status of extracellular signal-regulated protein kinases (ERK1/2) in 21 colorectal tumour specimens and compared it with that of paired normals. The specific MAPK activities were two- to tenfold lower in 71% (15 out of 21 cases) of colorectal tumours compared to those in paired normals. The individual MAPK kinase (MEK) correlated with MAPK activities (P = 0.006). Reduction of the MAPK and MEK activities in colorectal tumours was also observed in adenomas. These results suggested that down-regulation of the MAPK cascade may be caused by early genetic event(s) and that it may be related to the loss of normal growth control. Although MAPK activities were down-regulated both in adenomas and carcinomas, activities of the MAPKs in carcinomas were higher than those of paired adenomas. These results suggested that MAPK activities may be increased in the adenoma-to-carcinoma sequence and that it may play a role in the tumour progression. Observation of the differential regulation of MAPK activities in colorectal tumorigeneis suggested roles for the MAPK pathway in both positive and negative controls of cell growth.     

MUC15和PI3K/Akt 表达与胃癌临床病理特征及预后的相关性研究

目的:探讨MUC15 和PI 3K/Akt的表达与胃癌临床病理特征和预后的关系。方法:采用组织芯片和免疫组织化学法检测144 例胃癌组织及对应癌旁组织中MUC15、Akt的表达。结果:MUC15在胃癌中阳性表达率为79.8% ,高于癌旁组织中的阳性表达率22.2%（P < 0.01）;Akt在胃癌中阳性表达率为80.6% ,高于癌旁组织的阳性表达率16.7%（P < 0.01）。 MUC15和Akt表达均与胃癌分化程度、浸润深度、有无淋巴结转移和TNM 分期相关（P < 0.05）;且胃癌组织中MUC15表达和Akt表达呈正相关（P = 0.001）。 单因素生存分析显示,MUC15和Akt高表达均与生存时间呈负相关（P < 0.05）。 Cox 多元回归分析提示,MUC15和Akt同时阳性的胃癌患者预后更差（HR= 3.115,P < 0.05）。 结论:MUC15可能通过PI 3K/Akt细胞信号转导通路参与胃癌的发生、发展、浸润转移,MUC15结合Akt是胃癌预后强有力的预测因子。      

Expression of cripto, a Novel Gene of the Epidermal Growth Factor Family, in Human Gastrointestinal Carcinomas

The expression of mRNA for cripto gene, a novel transforming gene of the epidermal growth factor family, was examined in 20 alimentary tract carcinoma cell lines, 60 surgically resected tumor tissues and their adjacent normal mucosas. Although the cripto mRNA was not detected in esophageal carcinomas or in normal mucosas, it was detected in gastric and colorectal carcinomas. In gastric carcinomas, 2.2 kb cripto mRNA was detected in one cell line, all the gastric carcinoma tissues and their adjacent normal mucosas. Of 23 gastric tumor tissues 8 (34.8%) exhibited a higher mRNA level than normal gastric mucosas. cripto mRNA was detected in 2 out of 6 colorectal carcinoma cell lines. Interestingly, 18 (81.8%) out of 22 colorectal carcinoma specimens expressed a higher level of cripto mRNA than that in normal mucosas. The level of the expression was higher than that in gastric carcinoma tissues. The expression was also correlated to tumor stage of colorectal carcinomas.     

Livin蛋白在人大肠癌组织中的表达及临床意义

目的检测凋亡抑制因子Livin在大肠肿瘤组织中的表达,探讨Livin蛋白与大肠癌不同临床病理特征及预后的关系。方法采用免疫组织化学MaxVision^TM二步法检测Livin蛋白在178例大肠癌组织、60例癌旁组织及30例正常大肠组织中的表达情况。结果 178例大肠癌组织中Livin蛋白阳性率为65.7%（117/178）,高于癌旁组织（8.33%）及正常肠组织（0%）（P〈0.001）;Livin蛋白表达与肿瘤浸润深度、Duke’s分期、临床分期以及远处转移关系密切（P〈0.05）。经Cox回归模型多因素分析,示Livin蛋白表达是大肠癌患者长期生存的独立危险因素。结论人大肠癌组织中存在Livin蛋白表达,Livin蛋白表达与大肠癌患者的预后有关。     

Diverse mechanisms of Wnt activation and effects of pathway inhibition on proliferation of human gastric carcinoma cells

Human gastric carcinomas are among the most treatment-refractory epithelial malignancies. Increased understanding of the underlying molecular aberrations in such tumors could provide insights leading to improved therapeutic approaches. In this study, we characterized diverse genetic aberrations leading to constitutive Wnt signaling activation in a series of human gastric carcinoma cell lines. Downregulation of TCF signaling by stable transduction of dominant negative TCF4 (DNTCF4) resulted in inhibition of proliferation in Wnt-activated AGS tumor cells. c-Myc downregulation and the associated upregulation of its repression target, p21 observed in these tumor cells, as well as the profound growth inhibition induced by c-Myc small hairpin RNA (shRNA) implied their c-Myc addiction. In striking contrast, Wnt-activated MKN-28 and MKN-74 tumor cells appeared refractory to DNTCF4 inhibition of proliferation despite comparably decreased c-Myc expression levels. The resistance of these same tumor cells to growth inhibition by c-Myc shRNA established that their refractoriness to DNTCF was because of their independence from c-Myc for proliferation. There was no correlation between this resistance phenotype and the presence or absence of constitutive mitogen-activated protein kinase (MAPK) and/or AKT pathway activation, commonly observed in gastrointestinal tumors. However, in both DNTCF-sensitive and -resistant tumor cells with MAPK and/or AKT pathway activation, the ability of small molecule antagonists directed against either pathway to inhibit tumor cell growth was enhanced by Wnt pathway inhibition. These findings support the concept that although certain Wnt-activated tumors may escape c-Myc dependence for proliferation, disruption of other oncogenic pathways can unmask cooperative antiproliferative effects for Wnt pathway downregulation.     

Inhibition of MAPK kinase signaling pathways suppressed renal cell carcinoma growth and angiogenesis in vivo

The mitogen-activated protein kinase (MAPK) signaling pathways play essential roles in cell proliferation and differentiation. Recent studies also show the activation of MAPK signaling pathways in tumorigenesis, metastasis, and angiogenesis of multiple human malignancies, including renal cell carcinoma (RCC). To assess the role of this pathway in regulating the proliferation and survival of RCC cells, we first examined the expression of MAPK kinase (MKK) and MAPK in clear cell RCC and confirmed the overexpression of MKK1 and extracellular signal-regulated kinase 2 (ERK2) in these tumors. We then tested the effects of pharmacologic inhibition of MKK on human RCC cell lines, both in vitro and in vivo, using anthrax lethal toxin (LeTx), which cleaves and inactivates several MKKs. Western blotting showed that the phosphorylation levels of ERK, c-Jun-NH(2) kinase, and p38 MAPK decreased after 72 h of LeTx treatment. Exposure to LeTx for 72 h reduced cell proliferation by 20% without significant effects on cell cycle distribution and apoptosis. Anchorage-independent growth of RCC cells was dramatically inhibited by LeTx. In vivo studies showed that tumor growth of RCC xenografts could be suppressed by LeTx. Extensive necrosis and decreased tumor neovascularization were observed after LeTx treatment. LeTx also showed direct inhibition of proliferation of endothelial cells in vitro. Our results suggest that suppression of one or more MAPK signaling pathways may inhibit RCC growth through the disruption of tumor vasculature.     

Dominant negative EGFR-CD533 and inhibition of MAPK modify JNK1 activation and enhance radiation toxicity of human mammary carcinoma cells.

Exposure of MDA-MB-231 human mammary carcinoma cells to an ionizing radiation dose of 2 Gy results in immediate activation and Tyr phosphorylation of the epidermal growth factor receptor (EGFR). Doxycycline induced expression of a dominant negative EGFR-CD533 mutant, lacking the COOH-terminal 533 amino acids, in MDA-TR15-EGFR-CD533 cells was used to characterize intracellular signaling responses following irradiation. Within 10 min, radiation exposure caused an immediate, transient activation of mitogen activated protein kinase (MAPK) which was completely blocked by expression of EGFR-CD533. The same radiation treatment also induced an immediate activation of the c-Jun-NH2-terminal kinase 1 (JNK1) pathway that was followed by an extended rise in kinase activity after 30 min. Expression of EGFR-CD533 did not block the immediate JNK1 response but completely inhibited the later activation. Treatment of MDA-TR15-EGFR-CD533 cells with the MEK1/2 inhibitor, PD98059, resulted in approximately 70% inhibition of radiation-induced MAPK activity, and potentiated the radiation-induced increase of immediate JNK1 activation twofold. Inhibition of Ras farnesylation with a concomitant inhibition of Ras function completely blocked radiation-induced MAPK and JNK1 activation. Modulation of EGFR and MAPK functions also altered overall cellular responses of growth and apoptosis. Induction of EGFR-CD533 or treatment with PD98059 caused a 3-5-fold increase in radiation toxicity in a novel repeated radiation exposure growth assay by interfering with cell proliferation and potentiating apoptosis. In summary, this data demonstrates that both MAPK and JNK1 activation in response to radiation occur through EGFR-dependent and -independent mechanisms, and are mediated by signaling through Ras. Furthermore, we have demonstrated that radiation-induced activation of EGFR results in downstream activation of MAPK which may affect the radiosensitivity of carcinoma cells.     

ERK蛋白磷酸化在局部晚期结肠癌的临床意义

目的: 尽管MAPK通路异常活化在肿瘤发生、发展中发挥重要作用,但该通路在肿瘤特定阶段的具体作用尚缺乏研究。本文研究该通路活化在ⅢB期结肠癌的临床意义。 方法: 收集1997年1月至2002年5月中山大学肿瘤防治中心手术切除的ⅢB期结肠癌组织及其邻近的正常粘膜,采用免疫组织化学方法检测ERK蛋白磷酸化状态,分析其与临床病理特征以及5年生存率的关系。 结果: p-ERK1/2蛋白出现于细胞浆和(或)细胞核。在56例ⅢB期结肠癌患者中,癌旁正常肠粘膜几乎无ERK蛋白磷酸化。与癌旁正常粘膜相比,26例(46.4%)癌组织处于ERK高磷酸化状态(P<0.001),29例(51.8%)癌组织的ERK磷酸化水平无变化,1例(1.8%)癌组织处于低磷酸化状态。ERK1/2蛋白磷酸化状态与ⅢB期患者年龄、性别、部位及病理分级无关。癌组织ERK高磷酸化患者的5年生存率较高。患者年龄、性别、部位及病理分级与生存率无相关性。 结论: 局部晚期结肠癌组织中MAPK通路可能不是控制肿瘤生物学行为的关键信号通路。     

Des-γ-carboxyl prothrombin induces matrix metalloproteinase activity in hepatocellular carcinoma cells by involving the ERK1/2 MAPK signalling pathway

Des-γ-carboxy prothrombin (DCP), an aberrant prothrombin produced by hepatocellular carcinoma (HCC) cells, has been shown to be associated with the biological malignant potential of HCC. The aim of this study was to evaluate the effect of DCP on HCC cell growth and metastasis, and to explore the underlying molecular mechanisms. DCP significantly stimulated HCC cell growth, as measured by cell counting kit-8 assay. Transwell chamber assay showed that DCP increased HCC cell migration through reconstituted extracellular matrix (Matrigel). Gelatin zymography assay and Western blot analysis demonstrated that DCP increased the secretion and expression of matrix metalloproteinase (MMP)-2 and MMP-9 in the supernatant of cultured HCC cells and on tumour cell membranes. DCP was found to bind to the cell surface receptor Met, resulting in Met phosphorylation and subsequent activation of the epidermal growth factor receptor (EGFR). Western blot analysis demonstrated that DCP stimulated a sequential kinase phosphorylation cascade including ERK1/2, MEK1/2 and c-Raf, indicating activation of the extracellular signal-regulated kinase/mitogen activated protein kinase (ERK1/2 MAPK) signalling pathway. Furthermore, blocking ERK1/2 MAPK activation with ERK1/2 inhibitor PD98059 essentially abolished the DCP-induced MMP-2 and MMP-9 activity, confirming the signalling pathway of DCP stimulation. Taken together, these results suggested that DCP stimulates HCC growth and promotes HCC metastasis by increasing the activity of MMP-2 and MMP-9 through activation of the ERK1/2 MAPK signalling pathway.     

结直肠癌组织中肝素酶mRNA基因表达及其临床意义

目的:探讨结直肠癌组织中肝素酶mRNA表达及其与结直肠癌临床病理参数的关系。方法:采用逆转录聚合酶链反应(RT-PCR)及原位杂交技术检测62例结直肠癌组织及41例癌旁组织中肝素酶mRNA的表达。结果:肝素酶mR-NA在结直肠癌组织中的阳性表达明显高于癌旁组织(P<0·05),且其表达与结直肠癌Dukes分期、淋巴结转移有关(P<0·05)。结论:肝素酶促进了结直肠癌的生长、浸润及转移,与预后不良的病理特征有关。