Stanniocalcin-2 promotes epithelial-mesenchymal transition and invasiveness in hypoxic human ovarian cancer cells

The human glycoprotein, stanniocalcin-2 (STC2) is a HIF-1 target gene that is found to be associated with tumor development. The relationship of the prognostic outcome to the level of its expression in cancer tissues is controversial; however experimental evidence suggests that STC2 is a positive regulator of cancer progression. In the present study, we investigated if the expression of STC2 in hypoxic cells is associated with cancer invasion and metastasis. We studied the epithelial-mesenchymal transition (EMT) markers in STC2-silenced and over-expressed SKOV3 cells maintained in hypoxic condition. Western blot and immunocytochemical analysis revealed that the stable expression of exogenous STC2 promoted EMT, as revealed by the increase of N-cadherin/vimentin but a decrease of E-cadherin levels. This observation was further confirmed by colony formation assay where the STC2 stably transfected cells showed high degree of motility with fibroblast morphology under hypoxic condition. In conducting invasion assay in hypoxia, the STC2 stably transfected cells showed high degree of invasiveness. This observation was correlated with the significant increase of MMP2 and MMP9 expression in the STC2 stably transfected cells. In HUVEC/SKOV3 co-culture invasion study, endothelial invasion was found to be enhanced by the seeding of STC2 stably transfected cells in the lower compartment. These observations were possibly mediated by an increase of ROS and activated ERK1/2 levels in the cells. Collectively, the finding provides the first evidence that STC2 is a positive regulator in tumor progression at hypoxia.     

缺氧诱导因子与肾细胞癌关系的研究进展

缺氧诱导因子(hypoxia inducible factor,HIF)对维持肿瘤细胞的能量代谢、肿瘤血管生成、促进肿瘤细胞增殖和转移起着重要作用,是肿瘤细胞低氧条件下产生的关键信号分子。本综述旨在总结前人研究,阐述HIF与肾癌细胞之间的内在关系。HIF成员是参与肾癌细胞对缺氧应答反应中的关键因子,并通过靶基因的调节,促进新生血管的生成,导致肿瘤生长。其中,HIF-1α及HIF-2α在促进新生血管的生成方面发挥着主要作用。HIF-1α及HIF-2α与VEGF密切相关,随着其的表达增高,VEGF在数量上及m RNA水平上均显著增高,显示其可通过调控VEGF参与肾癌血管生成,而HIF-2α转录激活VEGF m RNA的特异性较HIF-1α更强。HIF-3α可能存在的负性调控作用,其异构体-4的作用可能与HIF-lα的负性调节有关,其可以阻止HIF-lα与下游靶基因的缺氧反应元件(hypoxia response elements,HRE)结合,同时可在转录水平抑制HIF-lα。HIF在未来可能有成为肾细胞癌治疗的靶点。     

Implications of Proprotein Convertases in Ovarian Cancer Cell Proliferation and Tumor Progression: Insights for PACE4 as a Therapeutic Target

Proprotein convertases are a family of kexin-like serine proteases that process proteins at single and multiple basic residues. Among the predicted and identified PC substrates, an increasing number of proteins having functions in cancer progression indicate that PCs may be potential targets for antineoplastic drugs. In support of this notion, we identified PACE4 as a vital PC involved in prostate cancer proliferation and progression, contrasting with the other co-expressed PCs. The aim of the present study was to test the importance of PCs in ovarian cancer cell proliferation and tumor progression. Based on tissue-expression profiles, furin, PACE4, PC5/6 and PC7 all displayed increased expression in primary tumor, ascites cells and metastases. These PCs were also expressed in variable levels in three model ovarian cell lines tested, namely SKOV3, CAOV3 and OVCAR3 cells. Since SKOV3 cells closely represented the PC expression profile of ovarian cancer cells, we chose them to test the effects of PC silencing using stable gene-silencing shRNA strategy to generate knockdown SKOV3 cells for each expressed PC. In vitro and in vivo assays confirmed the role of PACE4 in the sustainment of SKOV3 cell proliferation, which was not observed with the other three PCs. We also tested PACE4 peptide inhibitors on all three cell lines and observed consequent reduced cell proliferation which was correlated with PACE4 expression. Overall, these data support a role of PACE4 in promoting cell proliferation in ovarian cancer and provides further evidence for PACE4 as a potential therapeutic target.     

miR-125b慢病毒表达载体的构建及其对卵巢癌SKOV3细胞增殖和迁移的影响

构建并鉴定miR-125b慢病毒过表达载体,研究miR-125b对卵巢癌细胞增殖和迁移的影响及其可能机制。将PcR扩增的rniR-125b前体序列与经过酶切后的GP—SupersilencingVector进行连接,产生miR-125b重组慢病毒表达载体。将重组慢病毒载体质粒、pGag／Pol、pRev和pVSV-G共转染293T细胞,包装产生慢病毒。使用收获的病毒颗粒感染卵巢癌SKOV3细胞,嘌呤霉素筛选稳定感染细胞株;实时荧光定量PCR（Real．timeqPCR）检测miR-125b在SKV03细胞中的表达;Westernblot检测其潜在靶基因HER-2的表达：MTT实验和Transwell侵袭实验分别观察miR-125b过表达后SKOV3细胞增殖和迁移能力的改变。该研究成功构建miR-125b陧病毒过表达载体,感染卵巢癌SKOV3细胞后,能够过表达miR-125b,并抑制SKOV3细胞的增殖及迁移,降低潜在靶基因HER-2的表达。该研究证叽miR-125b能够抑制SKOV3细胞的增殖及迁移,并可能通过降低潜在靶基因HER-2的表达而实现。     

Quercetin suppresses hypoxia-induced accumulation of hypoxia-inducible factor-1alpha (HIF-1alpha) through inhibiting protein synthesis

Quercetin, a ubiquitous bioactive plant flavonoid, has been shown to inhibit the proliferation of cancer cells and induce the accumulation of hypoxia-inducible factor-1alpha (HIF-1alpha) in normoxia. In this study, under hypoxic conditions (1% O(2)), we examined the effect of quercetin on the intracellular level of HIF-1alpha and extracellular level of vascular endothelial growth factor (VEGF) in a variety of human cancer cell lines. Surprisingly, we observed that quercetin suppressed the HIF-1alpha accumulation during hypoxia in human prostate cancer LNCaP, colon cancer CX-1, and breast cancer SkBr3 cells. Quercetin treatment also significantly reduced hypoxia-induced secretion of VEGF. Suppression of HIF-1alpha accumulation during treatment with quercetin in hypoxia was not prevented by treatment with 26S proteasome inhibitor MG132 or PI3K inhibitor LY294002. Interestingly, hypoxia (1% O(2)) in the presence of 100 microM quercetin inhibited protein synthesis by 94% during incubation for 8 h. Significant quercetin concentration-dependent inhibition of protein synthesis and suppression of HIF-1alpha accumulation were observed under hypoxic conditions. Treatment with 100 microM cycloheximide, a protein synthesis inhibitor, replicated the effect of quercetin by inhibiting HIF-1alpha accumulation during hypoxia. These results suggest that suppression of HIF-1alpha accumulation during treatment with quercetin under hypoxic conditions is due to inhibition of protein synthesis.     

Adrenomedullin promotes human endothelial cell proliferation via HIF-1α

Adrenomedullin (ADM) and hypoxia-inducible factor-1α (HIF-1α) are important pro-proliferation genes in response to hypoxic stress. Although it was reported that ADM is a target gene for HIF-1, recent studies also showed that ADM regulates HIF-1 expression and its activity; however, the mechanism of action remains unknown. Two stable human endothelial cell lines with HIF-1α knockdown by hy926-siHIF-1α or HMEC-siHIF-1α were established. mRNA and protein expression of ADM and HIF-1α in EA.hy926 and HMEC1 cells were examined under hypoxic stress. Upon ADM treatment, cell proliferation was investigated and the expression profiles of HIF-1α and its target genes (VEGF, PFKP, PGK1, and AK1) were examined. Furthermore, the proline hydroxylase (PHD) mRNA level and its activity were investigated. We observed that mRNA and protein expression of ADM in hypoxia are earlier events than HIF-1α in EA.hy926 and HMEC1 cells. ADM-promoted cell proliferation of endothelial cells, which was HIF-1α dependent. We also found that ADM up-regulated the mRNA and protein expressions of HIF-1α- and HIF-1-targeted genes, and ADM up-regulated the protein expressions of HIF-1α through down-regulation of PHD mRNA expression and PHD activity.     

Chronic hypoxia promotes an aggressive phenotype in rat prostate cancer cells

In general, tumors cells that are resistant to apoptosis and increase angiogenesis are a result of the hypoxic responses contributing to the malignant phenotype. In this study, we developed a chronic hypoxic cell model (HMLL), by incubating the prostate cancer MatLyLu cells in a hypoxic chamber (1% O₂) over 3 weeks. Surviving cells were selected through each cell passage and were grown in the hypoxic condition up to 8 weeks. This strategy resulted in survival of only 5% of the cells. The surviving hypoxic cells displayed a greater stimulation on hypoxic adaptive response, including a greater expression of glucose transporter1 (Glut1) and VEGF secretion. In addition, higher invasion activity was observed in the chronic hypoxic HMLL cells as compared to MatLyLu cells exposed to acute hypoxia (1% O₂, 5 h) using the matrigel assay. To further examine the role of HIF-1α in tumor progression, both MatLyLu and HMLL cells were transfected with dominant-negative form of HIF-1α (DNHIF-1α). The Matrigel invasion activity induced by chronic hypoxia was significantly attenuated by DNHIF-1α. These results suggest that signaling pathways leading to hypoxic response may be differentially regulated in chronic hypoxic cells and acute hypoxic cells. Chronic hypoxia may play a greater role than acute hypoxia in promoting the aggressive phenotype of tumor cells. This observation mimics the clinical scenario where tumor cells following treatment with radiation are subjected to hypoxic conditions. The reemergence of tumor following treatment usually results in tumor cells that are more aggressive and metastatic.     

miR-335靶向Rho相关卷曲螺旋形成蛋白激酶1对卵巢癌细胞增殖的影响

目的: 探讨miR-335 靶向Rho相关卷曲螺旋形成蛋白激酶1(rho associated coiled-coil forming protein kinase 1,ROCK1)对卵巢癌细胞系SKOV3增殖的调控作用。方法:(1)选取卵巢癌细胞系SKOV3及人正常卵巢上皮细胞系IOSE80,采用RT-PCR检测各组细胞中miR-335表达;采用Western blot检测各组细胞中ROCK1蛋白表达;(2)选取卵巢癌细胞系SKOV3,分别转染miR-335 mimic及mimic control,采用RT-PCR检测细胞中miR-335表达;(3)选取卵巢癌细胞系SKOV3,将SKOV3荧光素酶报告载体与miR-335 mimic共转染,采用荧光素酶活性实验验证miR-335对SKOV3的靶向作用;(4)选取卵巢癌细胞系SKOV3,分为3组,即SKOV3组(转染mimic control)、miR-335 mimic组(转染miR-335 mimic)及miR-335 mimic+ROCK1组(共转染miR-335 mimic+ROCK1),采用MTT法检测各组细胞增殖活性,采用Western blot检测各组细胞中ROCK1蛋白表达,采用RT-PCR检测细胞中Cyclin D1表达。结果: (1)RT-PCR结果显示,卵巢癌细胞SKOV3中miR-335表达显著低于人正常卵巢上皮细胞IOSE80(P < 0.05);Western blot结果显示,卵巢癌细胞SKOV3中ROCK1蛋白表达显著高于人正常卵巢上皮细胞IOSE80(P < 0.05);(2)RT-PCR结果显示,转染miR-335 mimic可使卵巢癌细胞SKOV3中miR-335表达上调,与转染mimic control相比较差异具有统计学意义(P < 0.05);(3)双荧光素酶活性检测结果显示,miR-335 mimic可显著抑制野生型ROCK1-Wt报告载体的荧光素酶活性,但对突变型ROCK1-Mut报告载体的荧光素酶活性并无显著抑制作用;(4)转染miR-335mimic后,卵巢癌细胞SKOV3增殖活性及Cyclin D1表达较阴性对照组显著降低(P < 0.05);而转染miR-335 mimic+ROCK1后,卵巢癌细胞SKOV3增殖活性及Cyclin D1表达较单纯转染miR-335 mimic组显著提高(P < 0.05),但仍显著低于阴性对照组(P < 0.05)。Western blot检测结果显示,转染miR-335mimic后,卵巢癌细胞SKOV3中ROCK1蛋白表达较阴性对照组显著降低(P < 0.05);而转染miR-335 mimic+ROCK1后,ROCK1蛋白表达较单纯转染miR-335mimic组显著增高(P < 0.05),且显著高于阴性对照组(P < 0.05)。结论: miR-335可通过靶向ROCK1抑制卵巢癌细胞系SKOV3增殖。