Validation of Polo-like kinase 1 as a therapeutic target in pancreatic cancer cells

Polo-like kinase 1 (PLK1) is a serine/threonine protein kinase and plays a critical role in mitosis. PLK1 has also been regarded as a valuable target for cancer treatment, and several PLK1 inhibitors are currently undergoing clinical investigations. In this study, our data show that the expression level of PLK1 is upregulated in human pancreatic cancer cells. Molecular modeling studies indicate that DMTC inhibits PLK1 activity through competitive displacement of ATP from its binding pocket. Our data further show that DMTC suppresses the proliferation of pancreatic cancer cells and induces the formation of multinucleated cells, ultimately resulting in apoptosis. In addition, combination index analysis demonstrates that DMTC acts synergistically with the chemotherapeutic drug gemcitabine in inhibiting the proliferation of pancreatic cancer cells. These results thus suggest a potential of using PLK1 inhibitors for the treatment of pancreatic cancer.     

microRNA和食管癌关系的研究进展

microRNA是一类非蛋白编码的微小RNA分子,在人类多种生理和病理过程中起着重要的调节作用。越来越多的证据表明,miRNA和食管癌关系十分密切。本文就miRNA在食管癌中的表达、对食管癌生物学特性的影响和对食管癌治疗、预后的价值及研究进展等方面作一综述。     

Polo-like kinase 1 overexpression is an early event in the progression of papillary carcinoma

Polo-like kinase 1 (PLK1) is one of the serine threonine kinases that contributes to cell mitosis and is regarded as a marker of cellular proliferation. However, its protein expression in human carcinoma has not been studied in depth. We investigated PLK1 expression in various thyroid neoplasms in order to elucidate its physiological significance in thyroid carcinoma. Normal follicular cells only occasionally expressed PLK1. In follicular tumours and anaplastic carcinoma, PLK1 overexpression was not a common event and only 5.9% of follicular adenoma, 7.1% of follicular carcinoma, and 11.8% of anaplastic carcinoma overexpressed this protein. However, 43.7% of papillary carcinoma overexpressed PLK1. Polo-like kinase 1 overexpression was more frequently observed in smaller papillary carcinoma lesions, and 62.5% of microcarcinoma (ranging from 4 mm to 1.0 cm) and even 66.7% of incidental carcinoma (less than 4 mm) overexpressed it, whereas this phenomenon could only be seen in 20.0% of lesions larger than 4.0 cm. Furthermore, PLK1 overexpression was not related to cell-proliferating activity evaluated by Ki-67 labelling index, but it was inversely linked to UICC stage, extrathyroidal invasion, and the presence of poorly differentiated lesion as proposed by Sakamoto et al. These findings strongly suggest that, unlike other carcinomas previously studied, PLK1 does not act as a cell cycle regulator but plays a constitutive role in papillary carcinoma especially in the early phase, and may contribute to the malignant transformation of this carcinoma.     

RNAi技术沉默DKK1基因对食管癌ECA109及EC1细胞系增殖的影响

目的:通过构建DKK1的靶向小干扰RNA(small interfering RNA),探讨干扰DKK1基因的表达和对食管癌ECA109及EC1细胞系增殖的影响.方法:转染DKK1 siRNA于食管癌细胞系ECA109、EC1,应用蛋白免疫印迹方法检测转染前后细胞中DKK1的蛋白表达变化.食管癌细胞系ECA109及EC1成功干扰DKK1表达后,应用CCK-8法检测癌细胞增殖变化,平板克隆法检测癌细胞的克隆形成能力变化.结果:食管癌细胞系转染DKK1 siRNA后,ECA109中DKK1蛋白表达降低48.62％ (P ＜0.01),EC1中DKK1蛋白表达降低50％(P＜0.01).在CCK-8法检测癌细胞增殖变化实验中,DKK1 siRNA转染后24 h、48 h及72 h,相比阴性对照组,细胞增殖能力显著降低.平板克隆实验中,DKK1 siRNA转染后,ECA109细胞克隆均数(77.53±4.948)低于空白对照组(44.2±7.704),克隆率下降42.98％,而EC1细胞克隆均数(71.67±5.239)低于空白对照组(36±2.646),克隆率下降49.76％.结论:干扰DKK1的表达能够抑制食管癌细胞的增殖,DKK1可能成为抑制食管癌增殖的分子靶点.     

In vitro targeting of Polo-like kinase 1 in bladder carcinoma: Comparative effects of four potent inhibitors

Despite the improvements in neoadjuvant chemotherapy, the outcome of patients with advanced bladder cancer has changed very little over the past 30 years. In the present study we tested and compared the in vitro antitumor activities of four different inhibitors of Polo-like kinase 1 (PLK1) (BI 2536, BI 6727, GW843682X, and GSK461364), against 3 bladder carcinoma cell lines RT4, 5637 and T24. The impact on radiosensitivity and drug interactions in simultaneous treatments with cisplatin, methotrexate, and doxorubicin were also investigated. Our results showed that PLK1 inhibition prevented cell proliferation and clonogenicity, causing significant inhibition of invasion of tumor cells, though modest differences were observed between drugs. Moreover, all PLK1 inhibitors induced G₂/M arrest, with the subsequent induction of death in all 3 cell lines. Drug interactions studies showed auspicious results for all PLK1 inhibitors when combined with the commonly used cisplatin and methotrexate, though combinations with doxorubicin showed mostly antagonistic effects. Comparably, the four PLK1 inhibitors efficiently sensitized cells to ionizing radiation. Our findings demonstrate that irrespective of the inhibitor used, the pharmacological inhibition of PLK1 constrains bladder cancer growth and dissemination, providing new opportunities for future therapeutic intervention. However, further laboratorial and pre-clinical tests are still needed to corroborate the usefulness of using them in combination with other commonly used chemotherapeutic drugs.     

Regulation of UHRF1 by microRNA‐9 modulates colorectal cancer cell proliferation and apoptosis

The UHRF1 protein is pivotal for DNA methylation and heterochromatin formation, leading to decreased expressions of tumor suppressor genes and contributing to tumorigenesis. However, the factors that modulate UHRF1 expression in colorectal cancer (CRC) remain unclear. Here we showed that, compared with corresponding normal tissues, UHRF1 was upregulated and microRNA‐9 (miR‐9) was downregulated in CRC tissues. The expression of UHRF1 was inversely correlated with overall survival rates of patients with CRC. Overexpression of miR‐9 in CRC cell lines significantly attenuated CRC cell proliferation and promoted cell apoptosis. The expression of UHRF1 was markedly reduced in pre‐miR‐9 transfected CRC cells. Using luciferase reporter assay, we confirmed that miR‐9 was a direct upstream regulator of UHRF1. Finally, analysis of miR‐9 and UHRF1 levels in human CRC tissues revealed that expression of miR‐9 was inversely correlated with UHRF1 expression. Collectively, our results offer in vitro validation of the concept that miR‐9 could repress the expression of UHRF1, and function as a tumor‐suppressive microRNA in CRC. It may serve as a prognostic and therapeutic marker for CRC.     

miR －375在食管癌中的研究进展

MicroRNAs（miRNAs）是一类非蛋白编码的微小 RNA 分子,在人类多种生理和病理过程中起着重要的调节作用。大量研究表明,miRNAs 异常表达是肿瘤的重要特征之一。其中,miR －375和食管癌关系十分密切。miR －375在食管癌组织和血清中的低表达,表明患者预后较差。     

miR-320c regulates gemcitabine-resistance in pancreatic cancer via SMARCC1

Background:

Gemcitabine-based chemotherapy is the standard treatment for pancreatic cancer. However, the issue of resistance remains unresolved. The aim of this study was to identify microRNAs (miRNAs) that govern the resistance to gemcitabine in pancreatic cancer.

Methods:

miRNA microarray analysis using gemcitabine-resistant clones of MiaPaCa2 (MiaPaCa2-RGs), PSN1 (PSN1-RGs), and their parental cells (MiaPaCa2-P, PSN1-P) was conducted. Changes in the anti-cancer effects of gemcitabine were studied after gain/loss-of-function analysis of the candidate miRNA. Further assessment of the putative target gene was performed in vitro and in 66 pancreatic cancer clinical samples.

Results:

miR-320c expression was significantly higher in MiaPaCa2-RGs and PSN1-RGs than in their parental cells. miR-320c induced resistance to gemcitabine in MiaPaCa2. Further experiments showed that miR-320c-related resistance to gemcitabine was mediated through SMARCC1, a core subunit of the switch/sucrose nonfermentable (SWI/SNF) chromatin remodeling complex. In addition, clinical examination revealed that only SMARCC1-positive patients benefited from gemcitabine therapy with regard to survival after recurrence (P=0.0463).

Conclusion:

The results indicate that miR-320c regulates the resistance of pancreatic cancer cells to gemcitabine through SMARCC1, suggesting that miR-320c/SMARCC1 could be suitable for prediction of the clinical response and potential therapeutic target in pancreatic cancer patients on gemcitabine-based therapy.     

Tumor‐suppressive microRNA‐218 inhibits cancer cell migration and invasion via targeting of LASP1 in prostate cancer

Our recent studies of the microRNA (miRNA) expression signature in prostate cancer (PCa) indicated that miRNA‐218 (miR‐218) was significantly downregulated in clinical specimens, suggesting that miR‐218 might act as a tumor‐suppressive miRNA in PCa. The aim of the present study was to investigate the functional significance of miR‐218 in PCa and to identify novel miR‐218‐regulated cancer pathways and target genes involved in PCa oncogenesis and metastasis. Restoration of miR‐218 in PCa cell lines (PC3 and DU145) revealed that this miRNA significantly inhibited cancer cell migration and invasion. Gene expression data and in silico analysis demonstrated that LIM and SH3 protein 1 (LASP1) is a potential target of miR‐218 regulation. LASP1 is a cytoskeletal scaffold protein that plays critical roles in cytoskeletal organization and cell migration. Luciferase reporter assays showed that miR‐218 directly regulated expression of LASP1. Moreover, downregulating the LASP1 gene significantly inhibited cell migration and invasion in cancer cells, and the expression of LASP1 was upregulated in cancer tissues. We conclude that loss of tumor‐suppressive miR‐218 enhanced cancer cell migration and invasion in PCa through direct regulation of LASP1. Our data on pathways regulated by tumor‐suppressive miR‐218 provide new insight into the potential mechanisms of PCa oncogenesis and metastasis.     

可条件性诱导PLK1稳定敲降的食管癌细胞株的建立

目的： 建立可条件性诱导PLK1-shRNA稳定表达的食管癌细胞株,为深入研究PLK1在食管癌发生发展中的作用及分子机制提供细胞模型。方法：合成PLK1-shRNA寡核苷酸,退火后连接到慢病毒表达载体pLKO-Tet-On并转化至感受态细胞Stbl3,利用菌落PCR和测序分析鉴定阳性重组子。用pLKO-shPLK1-Tet-On重组质粒和包装质粒共转染293T细胞,收集病毒上清,感染食管癌细胞KYSE510,利用嘌呤霉素筛选可诱导PLK1-shRNA稳定表达的细胞株。采用qRT-PCR和Western blot检测强力霉素(Dox)诱导PLK1-shRNA表达的效率。结果：菌落PCR和测序分析结果显示,pLKO-shPLK1-Tet-On重组质粒中PLK1-shRNA的序列及插入位点正确。包装、收获病毒并感染KYSE510细胞后,筛选获得了具有嘌呤霉素抗性的稳定细胞株KYSE510-shPLK1-Tet-On。qRT-PCR和Western blot的检测结果显示,0.1 μg/mL Dox即可显著下调KYSE510-shPLK1-Tet-On细胞中PLK1的表达。结论：成功构建了诱导型PLK1-shRNA慢病毒表达载体,并筛选获得了可条件性诱导PLK1稳定敲降的食管癌细胞株,为进一步探讨PLK1异常表达与食管癌发生发展的关系提供了理想的细胞模型。     

The tumor suppressor microRNA‐29c is downregulated and restored by celecoxib in human gastric cancer cells

MicroRNAs (miRNAs) are small noncoding RNAs that function as endogenous silencers of target genes and play critical roles during carcinogenesis. The selective cyclooxygenase‐2 (COX‐2) inhibitor celecoxib has been highlighted as a potential drug for treatment of gastrointestinal tumors. The aim of this study was to investigate the role of miRNAs in gastric carcinogenesis and the feasibility of a new therapeutic approach for gastric cancer. miRNA expression profiles were examined in 53 gastric tumors including gastric adenomas (atypical epithelia), early gastric cancers and advanced gastric cancers and in gastric cancer cells treated with celecoxib. miRNA microarray analysis revealed that miR‐29c was significantly downregulated in gastric cancer tissues relative to nontumor gastric mucosae. miR‐29c was significantly activated by celecoxib in gastric cancer cells. Downregulation of miR‐29c was associated with progression of gastric cancer and was more prominent in advanced gastric cancers than in gastric adenomas and early gastric cancer. In addition, expression of the oncogene Mcl‐1, a target of miR‐29c, was significantly increased in gastric cancer tissues relative to nontumor gastric mucosae. Activation of miR‐29c by celecoxib induced suppression of Mcl‐1 and apoptosis in gastric cancer cells. These results suggest that downregulation of the tumor suppressor miR‐29c plays critical roles in the progression of gastric cancer. Selective COX‐2 inhibitors may have clinical promise for the treatment of gastric cancer via restoration of miR‐29c.     

MicroRNA‐338‐5p reverses chemoresistance and inhibits invasion of esophageal squamous cell carcinoma cells by targeting Id‐1

5‐Fluorouracil (5‐FU) is a chemotherapeutic agent commonly used to treat esophageal squamous cell carcinoma (ESCC), but acquisition of chemoresistance frequently occurs and the underlying mechanisms are not fully understood. We found that microRNA (miR)‐338‐5p was underexpressed in ESCC cells with acquired 5‐FU chemoresistance. Forced expression of miR‐338‐5p in these cells resulted in downregulation of Id‐1, and restoration of both in vitro and in vivo sensitivity to 5‐FU treatment. The effects were abolished by reexpression of Id‐1. In contrast, miR‐338‐5p knockdown induced 5‐FU resistance in chemosensitive esophageal cell lines, and knockdown of both miR‐338‐5p and Id‐1 resensitized the cells to 5‐FU. In addition, miR‐338‐5p had suppressive effects on migration and invasion of ESCC cells. Luciferase reporter assay confirmed a direct interaction between miR‐338‐5p and the 3′‐UTR of Id‐1. We also found that miR‐338‐5p was significantly downregulated in tumor tissue and serum samples of patients with ESCC. Notably, low serum miR‐338‐5p expression level was associated with poorer survival and poor response to 5‐FU/cisplatin‐based neoadjuvant chemoradiotherapy. In summary, we found that miR‐338‐5p can modulate 5‐FU chemoresistance and inhibit invasion‐related functions in ESCC by negatively regulating Id‐1, and that serum miR‐338‐5p could be a novel noninvasive prognostic and predictive biomarker in ESCC.     

PDK1 regulates the progression of esophageal squamous cell carcinoma through metabolic reprogramming

Esophageal squamous cell carcinoma (ESCC) is one of the deadliest human malignancies characterized by late-stage diagnosis, drug resistance, and poor prognosis. Pyruvate dehydrogenase kinase 1 (PDK1) plays an important role in regulating the metabolic reprogramming of cancer cells. However, its expression, function, and regulatory mechanisms of PDK1 in ESCC have not been reported. In this study, we found that PDK1 silence and dichloroacetic acid (DCA) significantly inhibited the growth of ESCC cells and induced cell apoptosis. Interestingly, PDK1 is a direct target of miR-6516-5p, and miR-6516-5p/PDK1 axis suppressed the growth of ESCC cell by inhibiting glycolysis. Moreover, DCA and cisplatin (cis-diammine-dichloroplatinum, DDP) synergistically inhibited the progression and glycolysis ability of ESCC cells both in vitro and in vivo by increasing oxidative stress via the inhibition of the Keap1/Nrf2 signaling pathway. And, Tert-butylhydroquinone (TBHQ), a specific activator of the Keap1/Nrf2 signaling, could diminish the synergic antitumor effects of DCA and DDP on ESCC cells. Collectively, our findings indicate that PDK1 may regulate the progression of ESCC by metabolic reprogramming, which provides new strategy for the treatment of ESCC.     

食管癌细胞系KYSE150中RNA干扰MTA1的基因芯片分析

目的探讨MTA1对食管癌转移相关基因的影响。方法用RNA干扰的方法在食管癌细胞系KYSE150中沉默MTA1基因的表达,随后进行转移相关基因芯片分析。以两次芯片分析中均上调2倍以上(或下调1/2)为差异显著基因。通过DIVID生物信息学数据库进行gene ontology的通路分析。结果在两次基因芯片分析中均有意义上调的基因共有7个,分别是LAMC1、MMP14、MMP15、MDM2、API5、ODC1、PTGS2;而两次均显著下调的基因共有14个,它们是CSF1R、HGF、IGF2、ITGA6、MMP9、MMP11、MMP13、CASP8、CTSD、TMPRSS4、THBS2、TIMP1、ENPP2、SNCG。通过在DAVID生物信息学数据库中对上述表达差异显著的基因进行通路分析,结果提示差异基因主要富集在5条信号通路上,分别是肿瘤信号通路(MDM2、CASP8、CSF1R、HGF、ITGA6、LAMC1、MMP9、PTGS2)、ECM受体整合信号通路(LAMC1、THBS、ITGA6)、基质金属蛋白酶信号通路(TIMP1、MMP9)、小细胞肺癌信号通路(ITGA6、Cox2)和黏着斑信号通路(ITGA6、HGF、IGF2)。结论 MTA1参与了转移相关的一系列分子改变事件,尚需进一步的分子生物学方法验证这些基因调控的信号途径。     

Glucose transporter 1 regulates the proliferation and cisplatin sensitivity of esophageal cancer

Glucose transporter 1 (GLUT1) expression is a prognostic marker for esophageal squamous cell carcinoma (ESCC). Recent work on GLUT1 and development of specific inhibitors supports the feasibility of GLUT1 inhibition as a treatment for various cancers. The anti–proliferative effects of GLUT1‐specific small interfering RNA (siRNA) and a GLUT1 inhibitor were evaluated in ESCC cell lines. Expression of pro–proliferative and anti–proliferative signaling and effector molecules was examined by western blotting and quantitative RT‐PCR. GLUT1 expression in pretreatment clinical biopsy samples was measured by immunohistochemistry and correlated with various clinicopathological parameters and response to chemotherapy. The reduction in standardized uptake value (SUV) of ¹⁸F‐fluoro‐deoxyglucose was calculated using the formula: ([pretreatment SUV_max – posttreatment SUV_max]/pretreatment SUV_max) × 100. GLUT1‐specific siRNA expression in ESCC cells inhibited their proliferation, increased expression of p27kip, and decreased expression of cyclin‐dependent kinase 6, pyruvate kinase muscle isozyme M2, lactate dehydrogenase A and phospho‐ERK1/2. Suppression of GLUT1 by siRNA increased low‐dose cisplatin‐induced inhibition of proliferation of TE‐11 ESCC cells, which express high GLUT1 levels. Similarly, BAY‐876, a GLUT1 inhibitor, enhanced cisplatin‐mediated inhibition of ESCC cell proliferation. GLUT1 expression in pretreatment biopsy samples was associated with the response to chemotherapy as well as the pathological tumor stage and histological response grade after esophagectomy. Finally, GLUT1‐negative tumors showed a significantly larger reduction in SUV_max (61.2% ± 4.5%) compared with GLUT1‐positive tumors (46.2% ± 4.4%). GLUT1 expression may be a surrogate marker of response to chemotherapy, and inhibition of GLUT1 may be a potential novel therapy for ESCC patients.