Reciprocal activation between PLK1 and Stat3 contributes to survival and proliferation of esophageal cancer cells.

BACKGROUND & AIMS: Aberrant activation of the signal transducer and activator of transcription (Stat)3 and overexpression of polo-like kinase (PLK)1 each have been associated with cancer pathogenesis. The mechanisms and significance of dysregulation of Stat3 and PLK1 in carcinogenesis and cancer progression are unclear. We investigated the relationship between Stat3 and PLK1 and the effects of their dysregulation in esophageal squamous cell carcinoma (ESCC) cells. METHODS: We used immunoblot, quantitative reverse-transcription polymerase chain reaction, immunochemistry, chromatin immunoprecipitation, mobility shift, and reporter assays to investigate the relationship between Stat3 and PLK1. We used colony formation, fluorescence-activated cell sorting, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling, and xenograft tumor assays to determine the effects of increased activation of Stat3 and PLK1 in proliferation and survival of ESCC cells. RESULTS: Stat3 directly activated transcription of PLK1 in esophageal cancer cells and mouse embryonic fibroblast cell NIH3T3. PLK1 then potentiated the expression of Stat3; ß-catenin was involved in PLK1-dependent transcriptional activation of Stat3. This mutual regulation between Stat3 and PLK1 was required for proliferation of esophageal cancer cells and resistance to apoptosis in culture and as tumor xenografts in mice. Furthermore, phosphorylation of Stat3 and overexpression of PLK1 were correlated in a subset of ESCC. CONCLUSIONS: Stat3 and PLK1 control each other's transcription in a positive feedback loop that contributes to the development of ESCC. Increased activity of Stat3 and overexpression of PLK1 promote survival and proliferation of ESCC cells in culture and in mice.

Suppression of anoikis by SKP2 amplification and overexpression promotes metastasis of esophageal squamous cell carcinoma.

The gene of SKP2, located on chromosome 5p13, plays a critical role in cell cycle progression, especially at the G(1)-S transition, putatively through its control of several cell cycle regulator proteins including p27(kip1), p21(cip1), p57(kip2), p130, cyclin E, and c-Myc. Previous studies in this laboratory revealed that gain of chromosome 5p was often seen in esophageal squamous cell carcinoma (ESCC). In the present study, we examined the amplification status and expression level of SKP2 in ESCC and investigated its clinicopathologic significance. Amplification and elevated expression of SKP2 correlated significantly with tumor stage and positive lymph node metastasis (P < 0.05). The SKP2 protein expression level as determined by immunohistochemical staining showed a significant inverse correlation with p27 protein. In vivo assay showed that inhibition of SKP2 expression also decreased tumor growth and lung metastasis of ESCC cells. At the molecular level, knockdown of SKP2 by RNA interference inhibited cell migration and invasion ability. Knockdown of SKP2 expression sensitized cancer cells to anoikis, and a wobble mutant of SKP2 that is resistant to SKP2 small interfering RNA can rescue this effect. Expression level of pAkt decreased after SKP2 knockdown. Treatment of cells with phosphoinositidyl 3-kinase inhibitor (LY294002) and constitutively activator (insulin-like growth factor I) had significant effects on the anoikis of SKP2 RNA interference cells. These results show for the first time that SKP2 is amplified and overexpressed in ESCC. Elevated expression of SKP2 protected cancer cells from anoikis, and this effect was mediated, at least in part, by the phosphoinositidyl 3-kinase-Akt pathway.

Overexpression of PLK1 is associated with poor survival by inhibiting apoptosis via enhancement of survivin level in esophageal squamous cell carcinoma.

PLK1 is essential for the maintenance of genomic stability during mitosis. In our study, we found that overexpression of PLK1 was an independent prognostic factor (RR=4.253, p=0.020) and significantly correlated with survivin, an antiapoptotic protein, in esophageal squamous cell carcinoma (ESCC). Reverse transcription-polymerase chain reaction and fluorescence in situ hybridization (FISH) revealed upregulation of PLK1 mRNA and amplification of PLK1 gene, respectively. Depletion of PLK1 activated the intrinsic apoptotic pathway, which was substantiated by loss of mitochondrial membrane potential, reduction of Mcl-1 and Bcl-2 as well as activation of caspase-9. Coimmunoprecipitation and confocal microscopy displayed that PLK1 was associated with survivin and PLK1 depletion led to downregulation of survivin. Cotransfection of survivin constructs could partially reverse PLK1-depletion-induced apoptosis. These data suggest that PLK1 might be a useful prognostic marker and a potential therapeutic target for ESCC. Survivin is probably involved in antiapoptotic function of PLK1.

Amplification of PRKCI, located in 3q26, is associated with lymph node metastasis in esophageal squamous cell carcinoma.

DNA amplification is one of the mechanisms to activate genes that are implicated in neoplastic transformation and gain of chromosome band 3q26 is a common event in squamous cell carcinomas. The aim of the present work was to identify the specific target gene from four candidates (MDS1, PRKCI, ECT2, and PIK3CA) located on 3q26 amplification in esophageal squamous cell carcinomas (ESCCs). To assess the prevalence of copy number gains of putative genes, fluorescence in situ hybridization (FISH) was applied on 108 ESCCs and 9 ESCC cell lines. Our data showed that MDS1 and PRKCI were more frequently gained. Positive correlation was found only for PRKCI between amplification and tumor size (P = 0.043), lymph node metastasis (P = 0.015) and clinical stage (P = 0.002). PRKCI gene amplification was highly correlated with protein overexpression (P = 0.009), suggesting that gene amplification is one important mechanism involved in PRKCI overexpression. To investigate further the role of PRKCI alteration in esophageal tumors, a tissue microarray containing samples from 180 ESCCs was used for immunohistochemistry analysis. Statistical analysis revealed that PRKCI overexpression was correlated with lymph node metastasis (P = 0.002) and higher stage (P = 0.004). Performing multivariate logistic regression analysis, a significant association between PRKCI overexpression and presence of lymph node metastasis was found, which was independent of T-stage of the primary tumors (P = 0.004). Our results indicate that PRKCI is an attractive target in the 3q26 amplicon and that it may serve as a molecular marker for metastasis and occult advanced tumor stages in ESCC.

Exogenous expression of Esophagin/SPRR3 attenuates the tumorigenicity of esophageal squamous cell carcinoma cells via promoting apoptosis.

Esophagin/SPRR3 is one of the cornified-envelope structural precursor proteins, which is expressed during epithelia cell differentiation. In 1996, another research group discovered, and our own laboratory subsequently confirmed, frequent and dramatic decreased Esophagin/SPRR3 expression in esophageal squamous cell carcinoma (ESCC). However, the role of Esophagin/SPRR3 in tumorigenesis of esophageal epithelium remains undetermined. In this study, we demonstrate that expression of Esophagin/SPRR3 is frequently downregulated in ESCC. In contrast, no correlations between downregulation of Esophagin/SPRR3 expression and clinicopathologic characteristics were observed. Diminished Esophagin/SPRR3 expression was present in dysplastic epithelia, suggesting that Esophagin/SPRR3 alteration could represent an early event in squamous carcinogenesis of the esophagus. Exogenous expression of Esophagin/SPRR3 significantly suppressed the ability of ESCC cells to form colonies in plastic and soft agar, as well as tumor formation in vivo. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end label assay and immunofluorescence analysis of the active form of Caspase 3 indicated that dysregulated apoptosis might contribute to reduced tumorigenicity. In particular, upregulation of CDK11p46 protein was observed in ESCC cells expressing Esophagin/SPRR3, but not in control cells, indicating that Esophagin/SPRR3-induced apoptosis may be due, at least in part, to increased expression of CDK11p46 protein. These findings suggest that Esophagin/SPRR3 may play a role in the maintenance of normal esophageal epithelial homeostasis, and that aberrant expression of Esophagin/SPRR3 may contribute to the tumorigenesis of ESCC.

Proteomic profiling of proteins dysregulted in Chinese esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) is one of the leading causes of cancer death in China. In the present study, proteins in tumors and adjacent normal esophageal tissues from 41 patients with ESCC were extracted, and two-dimensional electrophoresis (2-DE) was performed using the pH 3-10 and 4-7 immobilized pH gradient strips. The protein spots expressed differentially between tumors and normal tissues were identified by matrix-assisted laser desorption/ionization and liquid chromatography electrospray/ionization ion trap mass spectrometry. A total of 22 proteins differentially expressed between ESCC and normal esophageal tissues were identified, in which 17 proteins were upregulated and 5 downregulated in tumors. Biological functions of these proteins are related to cell signal transduction, cell proliferation, cell motility, glycolysis, regulation of transcription, oxidative stress processes, and protein folding. Some of the proteins obtained were confirmed by Western blotting and immunohistochemical staining. We showed that high expression of calreticulin and 78-kDa glucose-regulated protein (GRP78) were correlated with poor prognosis by Kaplan-Meier analysis and log rank analysis. Zinc finger protein 410, annexin V, similar to the ubiquitin-conjugating enzyme E2 variant 1 isoform c, mutant hemoglobin beta chain, TPM4-ALK fusion oncoprotein type 2, similar to heat shock congnate 71-kDa protein, GRP78, and pyruvate kinase M2 (M2-PK) were for the first time observed to be dysregulated in human ESCC tissues. The proteins here identified will contribute to the understanding of the tumorigenesis and progression of Chinese ESCC and may potentially provide useful markers for diagnosis or targets for therapeutic intervention and drug development.

Interaction of MT1-MMP and laminin-5gamma2 chain correlates with metastasis and invasiveness in human esophageal squamous cell carcinoma.

To gain insights into metastatic mechanisms in esophageal squamous cell carcinoma (ESCC), we established sublines (MLuB1 and MLuC1) with different capacity of spontaneous lung metastasis by subcutaneous injection of a human ESCC cell line (EC 9706) into nude mices. The incidence of the mice with lung metastasis produced by MLuC1 (87%) was significantly higher than that of MLuB1 (22%). The gene expression profiles of the two sublines were compared with cDNA arrays containing 5,000 known genes, and 47 genes were differentially expressed > or =2.0 fold. Laminin-5gamma2 chain (Ln-5gamma2) was one of the up-regulated genes in MLuC1 cells. Proteolytically processed forms of gamma2 are known to promote migration of a multitude of epithelial cells in vitro. Western-blotting analysis revealed that degraded fragments of Ln-5gamma2 and active form of membrane-type matrix metalloproteinase-1 (MT1-MMP) in MLuC1 was significantly higher than those in MLuB1. Expression of MT1-MMP was observed in 60 of 75 Ln-5gamma2-positive carcinoma tissues (80%). Co-expression of the two proteins was significantly associated with depth of invasion (P = 0.012). Moreover, proteolytic fragments of Ln-5gamma2 and active forms of MT1-MMP were frequently found in tumor tissues, whereas in the corresponding normal esophageal tissues there were only intact forms of gamma2 and MT1-MMP. siRNA-mediated silencing of MT1-MMP significantly reduced production of gamma2' and gamma2x in MLuC1 cells and inhibited cell migration. The results suggest that MT1-MMP is an enzyme responsible for Ln-5gamma2 cleavage in ESCC, and interaction between them may play a critical role in promoting invasion and metastasis of human ESCC.

Up-regulated manganese superoxide dismutase expression increases apoptosis resistance in human esophageal squamous cell carcinomas.

BACKGROUND: Esophageal cancer is one of the most common malignancies in the world. In order to identify the proteins associated with esophageal squamous cell carcinomas (ESCC), we analyzed the protein profiles of ESCC cases with tumor and matched adjacent normal tissues. METHODS: Two-dimensional electrophoresis (2-DE) was carried out to analyze the protein profiles. Dysregulated protein spots were identified by Matrix-Assisted Laser Desorption Ionization Time-of-Flight (MALDI-TOF) and verified by liquid chromatography/electrospray ionization ion trap-mass spectrometry/mass spectrometry (LC-ESI-IT MS). RT-PCR and immunohistochemistry on tissue microarray were performed to confirm the gene dysregulation in esophageal cancerous tissues. RNA interference (RNAi) was used to knock down the gene expression in ESCC cell lines. Apoptosis assay with annexin V-FITC/PI staining was conducted and cells were analyzed by flow cytometry. RESULTS: 2-DE showed that two protein spots with approximate molecular weights and different pI were elevated in 12 out of 18 ESCCs as compared to the corresponding normal tissues. Both the two spots were identified as MnSOD by MALDI-TOF and were verified by LC-ESI-IT MS. MnSOD overexpression was detected in 14 tumors out of 24 cases by RT-PCR and 52 tumors out of 116 cases by immunohistochemistry comparing to normal epithelia. siRNA-mediated silencing of MnSOD in KYSE450 and KYSE150 cell lines revealed that MnSOD protected ESCC cells from apoptosis induced by ultraviolet (UV) and doxorubicin (DOX). CONCLUSIONS: These findings suggest that there existed two isoforms of MnSOD protein in normal and tumor esophageal tissues. MnSOD was overexpressed in ESCC and its up-regulation in esophageal cancer cells was associated with apoptosis resistance.

[Isolation and comparative study of clones from human esophageal carcinoma cell line EC9706].

Cell line is one of the important materials for cancer research. In the present study, single-cell clones were isolated from esophageal carcinoma cell line EC9706 by limited dilution method. Three sublines were obtained, namely EC1, EC2 and EC3. Cytogenetic analysis showed that EC1 was a mixed clone, and the chromosome number of sublines EC2 and EC3 were 117 and 62, respectively. There were significant differences in the growth rate, cell cycle distribution, cell mobility, and colony formation ability between EC2 and EC3. The degree of malignancy was significantly higher for EC3 than for EC2. The monoclonal sublines EC2 and EC3 with different malignant potential provide useful materials for exploring the pathogenesis and gene therapy of human esophageal carcinoma, investigating multidrug resistance, and screening anti-tumor medications.

Identification of chromosome aberrations in esophageal cancer cell line KYSE180 by multicolor fluorescence in situ hybridization.

Analysis of chromosomal changes in esophageal squamous cell carcinoma (ESCC) can illuminate the molecular mechanisms underlying the development and progression of this cancer, which is among the 10 most common malignant tumors. Cell lines are better suited than surgical samples for chromosome analysis in this cancer. This study used multicolor fluorescence in situ hybridization (M-FISH) to characterize the molecular cytogenetics of ESCC in cell line KYSE180. Two pools of 12-color whole-chromosome painting probes were designed, and two rounds of FISH were performed on the same metaphase spreads. Loss of DNA copy number was observed at 4p, 5q, 6q, 9, 10p, 12p, 13, 14p, 15p, 18p, 18q, 20, 22, and Y. Chromosomal gains and translocations occurred at the entire or part of 1, 2p, 3, 4p, 5p, 5q, 6p, 7, 8, 10q, 11, 12q, 14q, 16, 17q, 19, and Xp. Seven derivative chromosomes (5, 8, 12, 14, 14, 14, and 17) presented complex translocations, each involving three or four chromosomes. No chromosomes 9, 13, or Y were detected. These results add significant information to the existing karyotype description of KYSE180 and provide detailed cytogenetic background data for appropriate use of the cell line.

[Clinical observation on cake-separated mild-warm moxibustion for treatment of knee osteoarthritis].

OBJECTIVE: To observe clinical therapeutic effect of monkshood cake-separated mild-warm moxibustion at Zusanli (ST 36) and Xiyan (EX-LE 5) on knee osteoarthritis. METHODS: The patients of monkshood cake-separated mild-warm moxibustion group were treated with monkshood cake-separated mild-warm moxibustion at Dubi (ST 35), Zusanli (ST 36) and Neixiyan (EX-LE 4) on the affected side, and the medication group with oral administration of Xianling Gubao Capsules. After treatment for 4 weeks, VAS and index of severity of osteoarthritis (ISOA scale) were used for assessment of clinical therapeutic effect. RESULTS: After treatment, the arthralgia and the index of severity significantly improved in the two groups (P < 0.01), and the analgesic effect and improvement of ISOA in the monkshood cake-separated mild-warm moxibustion group were better than those in the medication group (P < 0.05). The basic clinical cured rate was 80.0% and the effect-producing time was (10.91 +/- 4.17) days in the monkshood cake-separated mild-warm moxibustion group, and 53.3% and (12.28 +/- 4.60) days in the medication group, respectively, with a significant difference between the two groups (P < 0.05). CONCLUSION: Therapeutic effect of monkshood cake-separated mild-warm moxibustion on knee osteoarthritis is better than that of oral administration of Xianling Gubao Capsules.

[Clinical observation on treatment of rheumatoid arthritis with cake-separated mild moxibustion combined with Western medicine].

OBJECTIVE: To observe the effect-increasing action of cake-separated mild moxibustion on rheumatoid arthritis (RA), and to probe a new method for RA. METHODS: Sixty cases were randomly divided into 2 groups. The control group (n=30) were treated with oral administration of methotrexate (MTX) as basic treatment, and non-steroid anti-inflammatory agents (NSAIDs) according to conditions of the patient. The treatment group (n=30) were treated with the same treatment as the control group, and Fuzi case-separated moxibustion at Guanyuan (CV 4) and Zusanli (ST 36) was added. They were treated for 3 months. RESULTS: After treatment of 3 months, the total effective rate was 83.3% in the treatment group, which was higher than 60.0% in the control group (P < 0.05); there were significant differences before and after treatment in all indexes in the two groups (P < 0.05 or P < 0.01); the ratio of the patients who completely withdrew NSAIDs in the treatment group was significantly higher than that in the control group (P < 0.05); the rate of adverse reaction in the treatment group was significantly lower than that in the control group (P < 0.05). CONCLUSION: Fuzi cake-separated mild moxibustion can increase clinical therapeutic effect on RA and reduce dosage of NSAIDs.