Decorin-mediated inhibition of colorectal cancer growth and migration is associated with E-cadherin in vitro and in mice

Previous studies have shown that decorin expression is significantly reduced in colorectal cancer tissues and cancer cells, and genetic deletion of the decorin gene is sufficient to cause intestinal tumor formation in mice, resulting from a downregulation of p21, p27(kip1) and E-cadherin and an upregulation of β-catenin signaling [Bi,X. et al. (2008) Genetic deficiency of decorin causes intestinal tumor formation through disruption of intestinal cell maturation. Carcinogenesis, 29, 1435-1440]. However, the regulation of E-cadherin by decorin and its implication in cancer formation and metastasis is largely unknown. Using a decorin knockout mouse model (Dcn(-/-) mice) and manipulated expression of decorin in human colorectal cancer cells, we found that E-cadherin, a protein that regulates cell-cell adhesion, epithelial-mesenchymal transition and metastasis, was almost completely lost in Dcn(-/-) mouse intestine, and loss of decorin and E-cadherin accelerated colon cancer cell growth and invasion in Dcn(-/-) mice. However, increasing decorin expression in colorectal cancer cells attenuated cancer cell malignancy, including inhibition of cancer cell proliferation, promotion of apoptosis and importantly, attenuation of cancer cell migration. All these changes were linked to the regulation of E-cadherin by decorin. Moreover, overexpression of decorin upregulated E-cadherin through increasing of E-cadherin protein stability as E-cadherin messenger RNA and promoter activity were not affected. Co-immunoprecipitation assay showed a physical binding between decorin and E-cadherin proteins. Taken together, our results provide direct evidence that decorin-mediated inhibition of colorectal cancer growth and migration are through the interaction with and stabilization of E-cadherin.     

Genetic deficiency of decorin causes intestinal tumor formation through disruption of intestinal cell maturation

Decorin is a member of the small leucine-rich proteoglycan gene family and plays an important role in suppressing cancer cell growth and metastasis. To elucidate the importance of decorin in intestinal carcinogenesis, a decorin-deficient (Dcn(-/-)) mouse model was employed. We found that targeted inactivation of decorin was sufficient to cause intestinal tumor formation with 30% of the Dcn(-/-) mice developing intestinal tumors with no other chemical or genetic initiation. Moreover, a high-risk diet amplified and accelerated the tumors initiated by decorin deficiency. Further, tumorigenesis in Dcn(-/-) mice was associated with disruption of intestinal maturation, including decreased cell differentiation and increased proliferation, which were linked to the downregulation of p21(WAF1/cip1), p27(kip1), intestinal trefoil factor and E-cadherin and to the upregulation of beta-catenin signaling. In addition, we found that decorin was highly expressed in the differentiated area of human normal colonic mucosa, but was dramatically reduced in paired colorectal cancer tissues. Taken together, our data demonstrate that decorin acts as a tumor suppressor gene and plays an important role in the maintenance of cell maturation and therefore homeostasis in the intestinal tract.     

Suppression of tumorigenicity by adenovirus-mediated gene transfer of decorin

There is mounting evidence that decorin inhibits the growth of various tumor cell lines when either over-expressed in vitro or provided as a recombinant protein. The mechanism of action is primarily via a protracted inactivation of the epidermal growth factor receptor (EGFR) tyrosine kinase. In this study we explored the possibility of retarding the growth of tumor xenografts by decorin gene delivery into the growing neoplastic tissues. We demonstrate that transient transgene expression of replication-deficient adenovirus-containing decorin causes a significant growth inhibition of colon and squamous carcinoma tumor xenografts. These cytostatic effects were achieved with relatively low viral titers and correlated with a reduced proliferative index and an attenuation of the EGFR phosphorylation in vivo. Thus, decorin gene therapy helps in retarding the growth of human tumors in immunocompromised animals and could represent a new independent or adjunctive therapeutic modality against cancer.     

姜黄素抑制鼠转基因卵巢癌细胞系增殖及其与 p21/BRCA1 信号通路关系的研究

目的:探讨姜黄素对鼠转基因卵巢癌细胞系增殖活性的影响及其与p21/BRCA1信号通路的关系.方法:MTT法检测姜黄素对三种不同鼠转基因卵巢癌细胞系T1、T2、TBR6增殖活性的影响.T1细胞系基因型为:p53-/-,c-myc,K-ras BRCA1;T2为:p53-/-,c-myc,Akt,BRCA1;TBR6为p53-/-,C-myc,BRCA1-/-.RT-PCR法检测姜黄素作用后鼠转基因卵巢癌细胞系BRCA1和p21基因表达的变化.结果:姜黄素对鼠转基因卵巢癌细胞系T1、T2和TBR6均有明显抑制作用,且呈剂量-时间依赖性,但T1,T2的抑制率明显高于TBR6(P均＜0.05).姜黄素作用后,T1、T2细胞系BRCA1mRNA表达增高(P均＜0.05).姜黄素作用后,T1,T2,TBR6中p21 mRNA表达无明显差异.结论:姜黄素对三种鼠卵巢癌转基因细胞系均有明显抑制作用,但有BRCA1基因表达的细胞系对姜黄素作用更敏感.姜黄素抑制鼠卵巢癌转基因细胞系增殖的作用机制与上调抑癌基因BRCA1的表达有关.姜黄素对鼠转基因卵巢癌细胞系的抑制作用可能与p21信号通路无关.     

Phosphatidylinositol-3-OH kinase/AKT and survivin pathways as critical targets for geranylgeranyltransferase I inhibitor-induced apoptosis

Geranylgeranyltransferase I inhibitors (GGTIs) represent a new class of anticancer drugs. However, the mechanism by which GGTIs inhibit tumor cell growth is still unclear. Here, we demonstrate that GGTI-298 and GGTI-2166 induce apoptosis in both cisplatin-sensitive and -resistant human ovarian epithelial cancer cells by inhibition of PI3K/AKT and survivin pathways. Following GGTI-298 or GGTI-2166 treatment, kinase levels of PI3K and AKT were decreased and survivin expression was significantly reduced. Ectopic expression of constitutively active AKT2 and/or survivin significantly rescue human cancer cells from GGTI-298-induced apoptosis. Previous studies have shown that Akt mediates growth factor-induced survivin, whereas p53 inhibits survivin expression. However, constitutively active AKT2 failed to rescue the GGTIs downregulation of survivin. Further, GGTIs suppress survivin expression and induce programmed cell death in both wild-type p53 and p53-deficient ovarian cancer cell lines. These data indicate that GGTI-298 and GGTI-2166 induce apoptosis by targeting PI3K/AKT and survivin parallel pathways independent of p53. Owing to the fact that upregulation of Akt and survivin as well as inactivation of p53 are frequently associated with chemoresistance, GGTIs could be valuable agents to overcome antitumor drug resistance.     

Adenovirus-mediated expression of p53 or p21 in a papillary serous endometrial carcinoma cell line (SPEC-2) results in both growth inhibition and apoptotic cell death: potential application of gene therapy to endometrial cancer.

Papillary serous endometrial carcinoma is an aggressive tumor characterized by late-stage presentation, i.p. spread, and poor prognosis. It is histologically similar to serous papillary carcinoma of the ovary. Preclinical studies have shown that adenovirus-mediated expression of p53 in ovarian cancer cell lines causes growth inhibition and apoptosis in vitro and in vivo. Such studies provide the rationale for Phase I Adp53 gene therapy clinical trials in ovarian cancer. In the present study, we compared the efficacy of adenoviral vectors containing p53 (Adp53) or p21 (Adp21) in a papillary serous endometrial tumor cell line (SPEC-2) that contains mutated p53. Growth assays revealed that both Adp53 and Adp21 were efficacious in decreasing cell proliferation as assessed by anchorage-dependent and anchorage-independent growth assays. However, as compared with Adp53, the effects of Adp21 tended to be more transient and less marked. Strikingly, Adp21, but not Adp53, induced a G1 arrest in SPEC-2 endometrial adenocarcinoma cells. In contrast, as assessed by induction of hypodiploid peaks, free DNA ends detected by a terminal deoxynucleotidyl transferase-based assay, and annexin V positivity, p53 was more effective than p21 in inducing cell death by apoptosis. Compatible with the more efficient induction of apoptosis, Adp53, but not Adp21, induced a marked increase in expression of the preapoptotic molecule BAX without a concomitant change in expression of the antiapoptotic mediator Bcl-2. The differential effects of Adp53 and Adp21 on cell cycle progression and apoptosis may be related to the reversibility of p21-induced cell cycle arrest and the irreversibility of p53-induced apoptosis. Thus, at least in the papillary serous endometrial carcinoma cell line SPEC-2, Adp53 may be more effective than Adp21 as a gene therapeutic. Nevertheless, these preclinical studies suggest that papillary serous endometrial carcinoma is a potential target for p53- or p21-mediated gene therapy.     

Apigenin induces cell cycle arrest and p21/WAF1 expression in a p53-independent pathway

Apigenin, a common dietary flavonoid, has been shown to induce cell growth-inhibition and cell cycle arrest in many cancer cell lines. One important effect of apigenin is to increase the stability of the tumor suppressor p53 in normal cells. Therefore, apigenin is expected to play a large role in cancer prevention by modifying the effects of p53 protein. However, the mechanisms of apigenin's effects on p53-mutant cancer cells have not been revealed yet. We assessed the influence of apigenin on cell growth and the cell cycle in p53-mutant cell lines. Treatment with apigenin resulted in growth-inhibition and G2/M phase arrest in two p53-mutant cancer cell lines, HT-29 and MG63. These effects were associated with a marked increase in the protein expression of p21/WAF1. We have shown that p21/WAF1 mRNA expression was also markedly increased by treatment with apigenin in a dose- and time-dependent manner. However, we could not detect p21/WAF1 promoter activity following treatment with apigenin. Similarly, promoter activity from pG13-Luc, a p53-responsive promoter plasmid, was not activated by treatment with apigenin with or without p53 protein expression. These results suggest that there is a p53-independent pathway for apigenin in p53-mutant cell lines, which induces p21/WAF1 expression and growth-inhibition. Apigenin may be a useful chemopreventive agent not only in wild-type p53 status, but also in cancer with mutant p53.     

The oncogene phosphatidylinositol 3'-kinase catalytic subunit alpha promotes angiogenesis via vascular endothelial growth factor in ovarian carcinoma

The gene of phosphatidylinositol 3-kinase catalytic subunit alpha (PIK3CA) has been implicated as an oncogene in ovarian cancer [L. Shayesteh et al., Nat. Genet., 21: 99-102, 1999]. In this study, we examined the expression of PIK3CA mRNA and its p110alpha protein product in human ovarian carcinoma and investigated its role in regulating angiogenesis via vascular endothelial growth factor (VEGF). PIK3CA mRNA was detected in 66.6% of stage I and 93.9% of advanced stage ovarian cancer specimens and in all 17 ovarian cancer cell lines. PIK3CA mRNA levels were significantly higher in invasive carcinomas compared with benign and low malignant potential neoplasms (P = 0.007), but no significant difference was seen between early and advanced stage carcinomas (P = 0.812). Strong expression of immunoreactive p110alpha was detected in tumor cells and/or stroma endothelium. PIK3CA expression in vivo positively correlated, both at the mRNA and the protein level, with the expression of VEGF as well as with the extent of microvascular development. Furthermore, PIK3CA mRNA overexpression positively correlated with increased proliferation and decreased apoptosis of tumor cells in vivo. In vitro, PIK3CA expression positively correlated with the expression of VEGF in ovarian cancer cells, whereas the phosphatidylinositol 3'-kinase inhibitor Ly294002 reduced both the constitutive and inducible expression of hypoxia-inducible factor-1alpha at the mRNA and protein levels and abrogated VEGF up-regulation by glucose starvation. Furthermore, Ly294002 suppressed cell proliferation and, at higher doses, induced marked apoptosis in ovarian cancer cells. Collectively, these data strongly indicate that PIK3CA supports ovarian cancer growth through multiple and independent pathways affecting cell proliferation, apoptosis and angiogenesis, and plays an important role in ovarian cancer progression.     

Ovarian cancer cells that coexpress endogenous Rb and p16 are insensitive to overexpression of functional p16 protein

Defects of the 'Rb/cyclin D1/p16 pathway' have been shown to play a critical role in the development of virtually all human malignancies assessed. To determine the contribution of G1 phase cell cycle defects to ovarian tumorigenesis, we have examined a panel of normal and tumor ovarian tissues and ovarian cancer cell lines for the expression of Rb, p16 and cyclin D1 proteins. Unlike most types of human cancer whose development involves the loss of either Rb or p16 expression, we observed the coexpression of Rb, p16 and cyclin D1 in 82% of ovarian cancer tissues and cell lines. Furthermore, the growth and cell cycle distribution profiles of three ovarian cancer cell lines (ES-2, PA-1 and NIH OVCAR-3) that coexpressed Rb and p16, were found to be unaffected by adenoviral-mediated overexpression of functional p16 protein, indicating the existence of a defect(s) downstream from p16 in these cells. By contrast overexpression of ectopic p16 in the one ovarian cancer cell line (SK-OV-3) that expressed Rb but lacked p16 protein, resulted in a G1 growth arrest. These data suggest that defects of the 'Rb/cyclin D1/p16 pathway', other than the loss of Rb or p16, may play a major role in the development of ovarian cancer.     

RAD001 inhibits human ovarian cancer cell proliferation, enhances cisplatin-induced apoptosis, and prolongs survival in an ovarian cancer model.

PURPOSE: mTOR (mammalian target of rapamycin) plays a central role in regulating cell growth and cell cycle progression and is regarded as a promising therapeutic target. We examined whether mTOR inhibition by RAD001 (everolimus) is therapeutically efficacious in the treatment of ovarian cancer as a single agent and in combination with cisplatin. EXPERIMENTAL DESIGN: Using four human ovarian cancer cell lines, we determined the effect of RAD001 by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, Western blot, and apoptosis assays. We evaluated the association between phospho-AKT/mTOR activity and RAD001 sensitivity. We also determined the effect of RAD001 on tumor growth and malignancy using mice inoculated with human ovarian cancer cells. RESULTS: RAD001 markedly inhibited cell proliferation of human ovarian carcinoma cells with high AKT activity (OVCAR10 and SKOV-3), but the effect was minimal in cells with low AKT activity (OVCAR4 and OVCAR5). Sensitivity to RAD001 was independent of p53 expression. RAD001 inhibited the phosphorylation of downstream 4E-BP1 and p70S6 kinase and attenuated the expression of Myc. RAD001 also attenuated the expression of HIF-1 alpha and vascular endothelial growth factor, important factors in angiogenesis and tumor invasiveness. RAD001 enhanced cisplatin-induced apoptosis in cells with high AKT/mTOR activity, with minimal effect in cells with low AKT-mTOR activity. Mouse xenografts of SKOV-3 cells revealed that RAD001 inhibits tumor growth, angiogenesis, and i.p. dissemination and ascites production and prolongs survival. Moreover, treatment with RAD001 significantly enhanced the therapeutic efficacy of cisplatin in vivo. CONCLUSION: These results indicate that RAD001 could have therapeutic efficacy in human ovarian cancers with hyperactivated AKT/mTOR signaling.     

Multiple actions of the chemokine CXCL12 on epithelial tumor cells in human ovarian cancer

Of 14 chemokine receptors investigated, only CXCR4 was expressed on ovarian cancer cells [C. J. Scotton et al., Cancer Res., 61: 4961-4965, 2001]. To further understand the role of this chemokine receptor in ovarian tumor biology, we studied the action of its ligand, CXCL12 (stromal cell-derived factor 1), on the CXCR4-expressing ovarian cancer cell lines IGROV. Ligand stimulation of the CXCR4 receptor resulted in sustained activation of Akt/protein kinase B and biphasic phosphorylation of p44/42 mitogen-activated protein kinase in IGROV. When IGROV cells were cultured under suboptimal conditions, CXCL12 stimulated their in vitro growth, an effect that was abrogated by neutralizing antibodies to CXCR4. This increase in cell number was attributable to stimulation of DNA synthesis, not protection from apoptosis. CXCL12 treatment of IGROV cells also induced mRNA and protein for tumor necrosis factor alpha, a cytokine that is expressed by tumor cells in ovarian cancer biopsies. IGROV cells invaded through Matrigel toward a CXCL12 gradient. Invasion was abrogated by the broad spectrum matrix metalloproteinase and TNFalpha converting enzyme inhibitor Marimastat and was partially inhibited by neutralizing antitumor necrosis factor alpha antibodies. These effects were not limited to the IGROV cell line. They could also be demonstrated in the CAOV-3 ovarian cancer cell line and primary ovarian tumor cells isolated from ovarian ascites. These biological effects of CXCL12 on IGROV cells were also inhibited by the small molecular weight CXCR4 antagonist AMD3100. Finally, we found abundant intracellular CXCL12 protein in tumor cells in 15 of 18 ovarian cancer biopsies but not in epithelial cells from normal ovary or borderline disease. The chemokine CXCL12 may have multiple biological effects in ovarian cancer, stimulating cell migration and invasion through extracellular matrix, as well as DNA synthesis and establishment of a cytokine network in situations that are suboptimal for tumor cell growth.     

Increased expression of phospho-acetyl-CoA carboxylase protein is an independent prognostic factor for human gastric cancer without lymph node metastasis

Triptolide is a traditional Chinese medicinal herb-derived antineoplastic agent. However, its antitumor activity against gynecologic carcinomas has not yet been well described. It is the purpose of this article to investigate the effect and mechanism of triptolide in human ovarian cancer using both A2780 (p53 wild) and OVCAR-3 (p53 mutated) cells. Our results showed that triptolide exerted a potent inhibitory effect on the growth and proliferation of both cell lines in a dose- and time-dependent manner and that the effect was independent of the expression of p53. In contrast, triptolide had only a marginal cytotoxicity in noncancerous ovary cells, lung fibroblast cells, and macrophage cells, indicating differential inhibitory effects of the drug on cell growth between ovarian cancer cells and normal tissue cells. Exposure of the ovarian cancer cells to triptolide induced apoptosis, as evaluated by annexin V/propidium iodide-labeled flow cytometry. Triptolide-induced apoptosis was accompanied by cytochrome c release and caspase-3 activation and was associated with downregulation of Bcl-2 and upregulation of Bax. Cell cycle analysis demonstrated that treatment with triptolide induced cell cycle S phase arrest in A2780 cells and G2/M phase arrest in OVCAR-3 cells. Further detection by Western blotting revealed that the cell cycle arrest by triptolide in both cell lines occurred in concert with increased expression of p21^CIP1/WAF1. This study shows that triptolide selectively kills ovarian cancer cells with different p53 status predominantly through regulating the coordinate and dynamic cellular processes of proliferation and apoptosis, thereby making it a promising chemotherapeutic agent against a broad spectrum of ovarian carcinomas.     

Expression of decorin, a small leucine-rich proteoglycan, as a prognostic factor in soft tissue tumors

BACKGROUND AND OBJECTIVES: Decorin is a major extracellular matrix protein which has recently become the focus of various cancer studies. However, there have so far been no reports describing the clinicopathological implications of decorin in soft tissue tumors. The aim of this study was to examine whether decorin expression is a prognostic factor in soft tissue tumors. METHODS: Decorin expression was examined in 85 samples obtained from 77 patients by real-time quantitative PCR and immunohistochemistry. RESULTS: Lower levels of decorin were expressed in liposarcoma and malignant peripheral nerve sheath tumor than in lipoma (<0.01) and neurofibroma (P < 0.05), respectively. An immunohistochemical analysis for spindle-cell sarcomas demonstrated decorin protein to be produced by myofibroblastic cells in the peripheral stromal extracellular spaces. On a Kaplan-Meier analysis, lower levels of decorin were associated with lower disease-free and overall survival rates (P < 0.05) in 31 spindle-cell sarcomas. A multivariate analysis revealed a significant correlation between a reduced decorin expression and a poor disease-free survival (P = 0.04). In all seven patients with recurrent or metastatic lesions, the decorin expression levels were lower in secondary lesions than in primary lesions. CONCLUSIONS: A reduced decorin expression was found to be a useful biomarker of aggressiveness in soft tissue tumor.     

miR-142-5p对人上皮性卵巢癌细胞增殖和凋亡的影响

目的:探讨miR-142-5p靶向PTEN-PI3K/Akt信号调控人上皮性卵巢癌SKOV3细胞增殖和凋亡的具体机制。方法:Real-time PCR检测miR-142-5p在人卵巢癌组织及各卵巢癌细胞系中的表达情况。利用MTT、细胞克隆形成实验观察miR-142-5p对SKOV3细胞增殖活力的影响;Caspase-3活力检测miR-142-5p对SKOV3细胞凋亡情况;信号通路抑制剂处理及Western blot检测miR-142-5p、PTEN与PI3K/Akt信号通路的关系及PI3K/Akt信号下游基因Akt、FOXO1、cyclin D1等的表达情况;Luciferase实验验证miR-142-5p和PTEN 3' UTR的结合。结果:人上皮性卵巢癌组织及其细胞系中miR-142-5p表达显著增加（P<0.05)。与对照组相比,SKOV3细胞转染miR-142-5p mimics后活细胞数量显著增加,增殖能力显著上升,细胞凋亡下降（P<0.05);与之相反的,转染miR-142-5p inhibitor后SKOV3细胞增殖能力下调,凋亡增加。信号通路抑制剂处理显示miR-142-5p过表达激活PI3K/Akt信号通路。Luciferase实验显示miR-142-5p与PTEN 3' UTR直接结合。与对照组相比,miR-142-5p mimics组PTEN表达显著降低,p-Akt蛋白表达则显著上调（P<0.05）,同时过表达PTEN后p-Akt表达则显著降低（P<0.05）。结论:miR-142-5p通过抑制PTEN基因表达活化PI3K/Akt信号通路,促进人上皮性卵巢癌组织及SKOV3细胞增殖存活,抑制细胞凋亡。