Establishment and characterization of a new xenograft-derived human esophageal squamous cell carcinoma cell line SLMT-1 of Chinese origin

The Anticancer Effect of a Novel Quinoline Derivative 91b1 through Downregulation of Lumican

Quinoline derivatives have been reported to possess a wide range of pharmaceutical activities. Our group previously synthesized a series of quinoline compounds, in which compound 91b1 showed a significant anticancer effect. The purpose of this study was to evaluate the anticancer activity of compound 91b1 in vitro and in vivo, and screen out its regulated target. A series of cancer cell lines and nontumor cell lines were treated with compound 91b1 by MTS cytotoxicity assay and cell-cycle assay. In vivo anticancer activity was evaluated by a xenografted model on nude mice. Target prediction of 91b1 was assessed by microarray assay and confirmed by pancancer analysis. Relative expression of the target gene Lumican was measured by qRT-PCR. 91b1 significantly reduced tumor size in the nude mice xenograft model. Lumican was downregulated after 91b1 treatment. Lumican was proven to increase tumorigenesis in vivo, as well as cancer cell migration, invasion, and proliferation in vitro. The results of this study suggest that the anticancer activity of compound 91b1 probably works through downregulating the gene Lumican.

Orthotopic Xenograft Mouse Model in Esophageal Squamous Cell Carcinoma

Orthotopic xenograft model recapitulates the faithful organ-specific microenvironment and facilitates analyses involving tumor-stromal interactions that are crucial for developing new-generation cancer therapy. Herein, we describe the detailed rationales and protocols of a versatile orthotopic xenograft model for esophageal squamous cell carcinoma.

Macroscopic Examination of Surgical Specimen of Esophageal Squamous Cell Carcinoma

Macroscopic examination of the surgical specimen of esophageal squamous cell carcinoma by pathologist is important for quality clinical management, research, as well as education purposes. The process includes dissection of the specimen, identification of the lesion, measurements, and taking appropriate samples for histopathological examination. The basic principle of the examination is to study the characteristics and extent of the cancer. In addition, examination of proximal resection margin and circumferential resection margin are important in the cancer. A standardized approach for macroscopic examination by professionals is needed for accurate diagnosis and to optimize the use of the surgical specimen with esophageal squamous cell carcinoma.

Development of a Novel Quinoline Derivative as a P-Glycoprotein Inhibitor to Reverse Multidrug Resistance in Cancer Cells

Multidrug resistance (MDR) is one of conventional cancer chemotherapy’s limitations. Our group previously synthesized a series of quinoline-based compounds in an attempt to identify novel anticancer agents. With a molecular docking analysis, the novel compound 160a was predicted to target p-glycoprotein, an MDR candidate. The purpose of this study is to evaluate 160a’s MDR reversal effect and investigate the underlying mechanism at the molecular level. To investigate 160a’s inhibitory effect, we used a series of parental cancer cell lines (A549, LCC6, KYSE150, and MCF-7), the corresponding doxorubicin-resistant cell lines, an MTS cytotoxicity assay, an intracellular doxorubicin accumulation test, and multidrug resistance assays. The Compusyn program confirmed, with a combination index (CI) value greater than 1, that 160a combined with doxorubicin exerts a synergistic effect. Intracellular doxorubicin accumulation and transported calcein acetoxymethyl (AM) (a substrate for p-glycoprotein) were both increased when cancer cells with MDR were treated with compound 160a. We also showed that compound 160a’s MDR reversal effect can persist for at least 1 h. Taken together, these results suggest that the quinoline compound 160a possesses high potential to reverse MDR by inhibiting p-glycoprotein-mediated drug efflux in cancer cells with MDR.

Chemotherapeutic Treatments Increase PD-L1 Expression in Esophageal Squamous Cell Carcinoma through EGFR/ERK Activation

The current study reveals the clinicopathological association of PD-L1 in Hong Kong esophageal squamous cell carcinoma (ESCC) patients and the differential regulation of PD-L1 by standard first-line chemotherapy in ESCC. Immunohistochemical analysis of tissue microarray data from 84 Hong Kong ESCC patients shows that PD-L1 was expressed in 21% of the tumors. Positive PD-L1 staining was significantly associated with later disease stage (stages III and IV) (P value = .0379) and lymph node metastasis (P value = .0466) in the Hong Kong cohort. Furthermore, PD-L1 expression was significantly induced in ESCC cell lines after standard chemotherapy treatments, along with EGFR and ERK activation in both in vitro studies and the in vivo esophageal orthotopic model. The endogenous expression of PD-L1 was reduced by treatment with an EGFR inhibitor (erlotinib) or by the knockdown of EGFR. Moreover, the upregulation of PD-L1 by chemotherapy was also attenuated by the treatment with erlotinib and a MAPK/MEK inhibitor (AZD6244), suggesting that PD-L1 is regulated by the EGFR/ERK pathway in ESCC. The regulation of PD-L1 by the EGFR pathway was further supported by the correlation of PD-L1 and EGFR expression observed in the commercially available tissue microarray set (P value = .028). Taken together, the current study was the first to demonstrate the upregulation of PD-L1 by chemotherapy in ESCC and its regulation through the EGFR/ERK pathway. The results suggest the potential usefulness of combined conventional chemotherapy together with anti-PD-L1 immunotherapy to achieve better treatment outcome.

Targeting DNA Binding for NF-κB as an Anticancer Approach in Hepatocellular Carcinoma

Quinoline core has been shown to possess a promising role in the development of anticancer agents. However, the correlation between its broad spectrum of bioactivity and the underlying mechanism of actions is poorly understood. The present study, with the use of bioinformatics approaches, reported a series of designed molecules which integrated quinoline core and sulfonyl moiety, with the objective of evaluating the substituent and linker effects on anticancer activities and associated mechanistic targets. We identified potent compounds (1h, 2h, 5 and 8) exhibiting significant anticancer effects towards liver cancer cells (Hep3B) with the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) relative values of cytotoxicity below 0.40, a value in the range of doxorubicin positive control with the value of 0.12. Bulky substituents and the presence of bromine atom, as well as the presence of sulfonamide linkage, are likely the favorable structural components for molecules exerting a strong anticancer effect. To the best of our knowledge, our findings obtained from chemical synthesis, in vitro cytotoxicity, bioinformatics-based molecular docking analysis (similarity ensemble approach, SEA),and electrophoretic mobility shift assay provided the first evidence in correlation to the anticancer activities of the selected compound 5 with the modulation on the binding of transcription factor NF-κB to its target DNA. Accordingly, compound 5 represented a lead structure for the development of quinoline-based NF-κB inhibitors and this work added novel information on the understanding of the mechanism of action for bioactive sulfonyl-containing quinoline compounds against hepatocellular carcinoma.

Expression of Insulin-Like Growth Factor Binding Protein-5 (IGFBP5) Reverses Cisplatin-Resistance in Esophageal Carcinoma

Cisplatin (CDDP) is one of the front-line chemotherapeutic drugs used in the treatment of esophageal squamous cell carcinoma (ESCC). Occurrence of resistance to CDDP has become one of the main challenges in cancer therapy. In this study, the gene expression profile of CDDP-resistant ESCC cells was investigated and molecular approaches were explored in an attempt to reverse the CDDP resistance. A CDDP-resistant SLMT-1/CDDP1R cell line was established from SLMT-1 cells by subculturing in the medium containing an increasing concentration of CDDP (0.1–1μg/mL). Mitochondrial (MTS) cytotoxicity assay, cell proliferation assay and cell morphology were used to assess the acquisition of cisplatin-resistance. The most differentially expressed gene in SLMT-1/CDDP1R cells was identified by cDNA microarray analysis compared with the parental SLMT-1 cells and validated by quantitative real-time polymerase chain reaction (qPCR). Association between expression of the most differentially expressed target gene to cisplatin-resistance was verified by RNA interference. An attempt to reversecisplatin-resistance phenotypes was made by using the vector expressing the most downregulated target gene in the CDDP-resistant cells. A CDDP-resistant ESCC cell line, SLMT-1/CDDP1R, was established with 2.8-fold increase CDDP-resistance (MTS₅₀ = 25.8 μg/mL) compared with the parental SLMT-1 cells. cDNA microarray analysis revealed that IGFBP5 showed the highest level of downregulation in SLMT-1/CDDP1R cells compared with the parental SLMT-1 cells. Suppression of IGFBP5 mediated by IGFBP5-targeting siRNA in parental SLMT-1 cells confirmed that IGFBP5 suppression in ESCC cells would induce CDDP-resistance. More importantly, upregulation of IGFBP5 using IGFBP5 expression vector reduced cisplatin-resistance in SLMT-1/CDDP1R cells by 41%. Thus, our results demonstrated that IGFBP5 suppression is one of the mechanisms for the acquisition of cisplatin-resistance in ESCC cells. Cisplatin-resistance phenotype can be reversed by increasing the expression level of IGFBP5. The overall findings of this study thus offered a new direction for reversing the CDDP resistance in ESCC and possibly in other cancer types with further investigations in future.

Anti-cancer Effects of a Novel Quinoline Derivative 83b1 on Human Esophageal Squamous Cell Carcinoma through Down-Regulation of COX-2 mRNA and PGE2

PURPOSE

83b1 is a novel quinoline derivative that has been shown to inhibit cancer growth in human esophageal squamous cell carcinoma (ESCC). This study was conducted to comprehensively evaluate the cytotoxic effects of 83b1 on a series of ESCC cell lines and investigate the mechanisms by which 83b1 suppresses cancer growth based on molecular docking analysis.

MATERIALS AND METHODS

A series of ESCC and nontumor immortalized cell lines were exposed to 83b1 and cisplatin (CDDP) in a dose-dependent manner, and the cytotoxicity was examined by a MTS assay kit. Prediction of the molecular targets of 83b1 was conducted by molecular docking analysis. Expression of cyclooxygenase 2 (COX-2) mRNA and COX-2-derived prostaglandin E₂ (PGE₂) were measured by quantitative real-time polymerase chain reaction and enzymelinked immuno-sorbent assay, respectively. In vivo anti-tumor effect was determined using a nude mice xenografted model transplanted with an ESCC cell line, KYSE-450.

RESULTS

83b1 showed the significant anti-cancer effects on all ESCC cell lines compared to CDDP; however, 83b1 revealed much lower toxic effects on non-tumor cell lines than CDDP. The predicted molecular target of 83b1 is peroxisome proliferator-activated receptor delta (PPARδ), which is a widely known oncoprotein. Additionally the expression of COX-2 mRNA and COX-2-derived PGE₂ were down-regulated by 83b1 in a dose-dependent manner in ESCC cell lines. Furthermore, 83b1 was shown to significantly reduce the tumor size in nude mice xenograft.

CONCLUSION

The results of this study suggest that the potential anti-cancer effects of 83b1 on human esophageal cancers occur through the possible oncotarget, PPARδ, and down-regulation of the cancer related genes and molecules.

Nuclear Localization of DNAJB6 Is Associated With Survival of Patients With Esophageal Cancer and Reduces AKT Signaling and Proliferation of Cancer Cells

BACKGROUND & AIMS

The DnaJ (Hsp40) homolog, subfamily B, member 6 (DNAJB6) is part of a family of proteins that regulates chaperone activities. One of its isoforms, DNAJB6a, contains a nuclear localization signal and regulates β-catenin signaling during breast cancer development. We investigated the role of DNAJB6 in the pathogenesis of esophageal squamous cell carcinoma (ESCC).

METHODS

We performed immunohistochemical analyses of primary ESCC samples and lymph node metastases from a cohort of 160 patients who underwent esophagectomy with no preoperative chemoradiotherapy at Hong Kong Queen Mary Hospital. Data were collected on patient outcomes over a median time of 12.1 ± 2.9 months. Retrospective survival association analyses were performed. Wild-type and mutant forms of DNAJB6a were overexpressed in cancer cell lines (KYSE510, KYSE 30TSI, KYSE140, and KYSE70TS), which were analyzed in proliferation and immunoblot assays, or injected subcutaneously into nude mice. Levels of DNAJB6 were knocked down in ESCC cell lines (KYSE450 and T.Tn), immortalized normal esophageal epithelial cell lines (NE3 and NE083), and other cells with short hairpin RNAs, or by genome engineering. Bimolecular fluorescence complementation was used to study interactions between proteins in living cells.

RESULTS

In primary ESCC samples, patients whose tumors had high nuclear levels of DNAJB6 had longer overall survival times (19.2 ± 1.8 months; 95% confidence interval [CI], 15.6-22.8 mo) than patients whose tumors had low nuclear levels of DNAJB6 (12.6 ± 1.4 mo; 95% CI, 9.8-15.4 mo; P = .004, log-rank test). Based on Cox regression analysis, patients whose tumors had high nuclear levels of DNAJB6 had a lower risk of death than patients with low levels (hazard ratio, 0.562; 95% CI, 0.379-0.834; P = .004). Based on log-rank analysis and Cox regression analysis, the combination of the nuclear level of DNAJB6 and the presence of lymph node metastases at diagnosis could be used to stratify patients into groups with good or bad outcomes (P < .0005 for both analyses). There was a negative association between the nuclear level of DNAJB6 and the presence of lymph node metastases (P = .022; Pearson χ(2) test). Cancer cell lines that overexpressed DNAJB6a formed tumors more slowly in nude mice than control cells or cells that expressed a mutant form of DNAJB6a that did not localize to the nucleus. DNAJB6 knockdown in cancer cell lines promoted their growth as xenograft tumors in mice. A motif of histidine, proline, and aspartic acid in the J domain of DNAJB6a was required for its tumor-suppressive effects and signaling via AKT1. Loss of DNAJB6a resulted in up-regulation of AKT signaling in cancer cell lines and immortalized esophageal epithelial cells. Expression of a constitutively active form of AKT1 restored proliferation to tumor cells that overexpressed DNAJB6a, and DNAJB6a formed a complex with AKT1 in living cells. The expression of DNAJB6a reduced the sensitivity of ESCC to AKT inhibitors; the expression level of DNAJB6a affected AKT signaling in multiple cancer cell lines.

CONCLUSIONS

Nuclear localization of DNAJB6 is associated with longer survival times of patients with ESCC. DNAJB6a reduces AKT signaling, and DNAJB6 expression in cancer cells reduces their proliferation and growth of xenograft tumors in mice. DNAJB6a might be developed as a biomarker for progression of ESCC.

Oxygen carrier YQ23 can enhance the chemotherapeutic drug responses of chemoresistant esophageal tumor xenografts

PURPOSE

Adjunct chemoradiation is offered to unresectable esophageal squamous cell carcinoma (ESCC) patients, while its use is limited in tumors with strong resistance. Oxygen carriers or anti-hypoxic drugs belong to an emerging class of regulators that can alleviate tumor hypoxia.

METHODS

We investigate the potential use of a novel oxygen carrier YQ23 in sensitizing chemoresistant ESCC in a series of subcutaneous tumor xenograft models developed using ESCC cell lines with different strengths of chemosensitivities.

RESULTS

Tumor xenografts were developed using SLMT-1 and HKESC-2 ESCC cell lines with different strengths of resistance to two chemotherapeutic drugs, 5-fluorouracil and cisplatin. More resistant SLMT-1 xenografts responded better to YQ23 treatment than HKESC-2, as reflected by the induced tumor oxygen level. YQ23 sensitized SLMT-1 xenografts toward 5-fluorouracil via its effect on reducing the level of a hypoxic marker HIF-1α. Furthermore, a derangement of tumor microvessel density and integrity was demonstrated with a concurrent decrease in the level of a tumor mesenchymal marker vimentin. Similar to the 5-fluorouracil sensitizing effect, YQ23 also enhanced the response of SLMT-1 xenografts toward cisplatin by reducing the tumor size and the number of animals with invasive tumors. Chemosensitive HKESC-2 xenografts were irresponsive to combined YQ23 and cisplatin treatment.

CONCLUSIONS

In all, YQ23 functions selectively on chemoresistant ESCC xenografts, which implicates its potential use as a chemosensitizing agent for ESCC patients.

A versatile orthotopic nude mouse model for study of esophageal squamous cell carcinoma

Increasing evidence indicates tumor-stromal interactions play a crucial role in cancer. An in vivo esophageal squamous cell carcinoma (ESCC) orthotopic animal model was developed with bioluminescence imaging established with a real-time monitoring platform for functional and signaling investigation of tumor-stromal interactions. The model was produced by injection of luciferase-labelled ESCC cells into the intraesophageal wall of nude mice. Histological examination indicates this orthotopic model is highly reproducible with 100% tumorigenesis among the four ESCC cell lines tested. This new model recapitulates many clinical and pathological properties of human ESCC, including esophageal luminal stricture by squamous cell carcinoma with nodular tumor growth, adventitia invasion, lymphovascular invasion, and perineural infiltration. It was tested using an AKT shRNA knockdown of ESCC cell lines and the in vivo tumor suppressive effects of AKT knockdown were observed. In conclusion, this ESCC orthotopic mouse model allows investigation of gene functions of cancer cells in a more natural tumor microenvironment and has advantages over previous established models. It provides a versatile platform with potential application for metastasis and therapeutic regimen testing.

Overexpression of transferrin receptor CD71 and its tumorigenic properties in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is the predominant type of esophageal cancer in endemic Asian regions. In the present study, we investigated the clinical implication and role of transferrin receptor CD71 in ESCC. CD71 has a physiological role in cellular iron intake and is implicated in the carcinogenesis of various types of tumors. In our cohort, more than a 2-fold upregulation of the CD71 transcript was detected in 61.5% of patients using quantitative polymerase chain reaction. Immunohistochemical analysis also showed strong membranous and cytoplasmic localization of CD71 in paraffin-embedded tumors. Staining parallel tumor sections with the proliferative marker Ki-67 revealed that the pattern of Ki-67 staining was associated with CD71 expression. Analysis of clinicopathological data indicated that CD71 overexpression can be used as an indicator for advanced T4 stage (p=0.0307). These data suggested a strong link between CD71 and ESCC. Subsequent in vitro assays using short interfering RNA (siRNA) to suppress CD71 expression confirmed the tumorigenic properties of CD71 in ESCC; cell growth inhibition and cell cycle arrest at S phase were observed in CD71-suppressed cells. The underlying mechanism involved activation of the MEK/ERK pathway. In summary, the present study provides evidence showing the tumorigenic properties of CD71 in ESCC with clinical correlations and suggests targeting CD71 as a strategy for the treatment of ESCC.

Cytoplasmic Forkhead box M1 (FoxM1) in esophageal squamous cell carcinoma significantly correlates with pathological disease stage

Abstract

Esophageal cancer is a deadly cancer with esophageal squamous cell carcinoma (ESCC) as the major type. Until now there has been a lack of reliable prognostic markers for this malignancy. This study aims to investigate the clinical correlation between Forkhead box M1 (FoxM1) and patients’ parameters in ESCC.

Methods

Immunohistochemistry was performed to investigate the expression and localization of FoxM1 in 64 ESCC tissues and 10 nontumor esophageal tissues randomly selected from 64 patients before these data were used for clinical correlations.

Results

Cytoplasmic and nuclear expressions of FoxM1 were found in 63 and 16 of the 64 ESCC tissues, respectively. Low cytoplasmic expression of FoxM1 was correlated with early pathological stage in ESCC (P = 0.018), while patients with nuclear FoxM1 were younger in age than those without nuclear expression (P < 0.001). Upregulation of FoxM1 mRNA was found in five ESCC cell lines (HKESC-1, HKESC-2, HKESC-3, HKESC-4, and SLMT-1) when compared to non-neoplastic esophageal squamous cell line NE-1 using quantitative polymerase chain reaction (qPCR). Except for HKESC-3, all studied ESCC cell lines demonstrated a high expression of FoxM1 protein using immunoblot. A high mRNA level of FoxM1 was observed in all of the ESCC tissues examined when compared to their adjacent nontumor tissues using qPCR.

Conclusion

Cytoplasmic FoxM1 was correlated with pathological stage and might be a biomarker for advanced ESCC.

Clinical correlation of nuclear survivin in esophageal squamous cell carcinoma

To examine the correlation of survivin (both total and nuclear survivin) with clinicopathological parameters of esophageal squamous cell carcinoma (ESCC) patients. Tumors and non-tumor tissues near the proximal resection margins were resected from ESCC patients undergone esophagectomy. Quantitative polymerase chain reaction (qPCR) was performed to detect survivin mRNA expression level in the 10 paired tumor and adjacent non-tumor tissues. To confirm with the clinical situation, survivin mRNA and protein expression were measured by qPCR and immunoblot, respectively, in 5 ESCC cell lines and a non-neoplastic esophageal epithelial cell line. Immunohistochemistry was employed to reveal the cellular localization of survivin in tumor tissues isolated from the 64 ESCC patients undergone surgery alone. Up-regulation of survivin mRNA and protein was found in 5 ESCC lines (HKESC-1, HKESC-2, HKESC-3, HKESC-4, and SLMT-1) when compared to a non-neoplastic esophageal epithelial cell line NE-1. In particular, HKESC-3, HKESC-4, and SLMT-1 cells demonstrated ~50-fold increase in survivin mRNA. High level of survivin mRNA in tumor tissues when compared to non-tumor tissues was found in 70 % (7 of 10) of clinical cases. The increase in expression ranged from ~twofold to ~16-fold. Immunohistochemistry results showed that survivin was found at the cell nuclei in all specimens examined. Nuclear expression of survivin was inversely associated with the likelihood of developing nodal metastasis (p = 0.021) and significantly associated with early-stage ESCC (p = 0.039). Nuclear survivin could serve as a marker for indicating disease status in ESCC patients.

Orthotopic models of esophageal carcinoma and their use in drug discovery

The protocol detailed in this unit is for the establishment of an orthotopic model of human esophageal adenocarcinoma in NMRI/nu mice. The resultant tumor has high metastatic potential, spreading readily to liver, lungs, and lymph nodes. This model is useful for studying primary esophageal carcinoma, tumor biology, pathogenesis, tumor progression, metastatic homing, and the efficacy of therapeutic approaches for treating this condition. The practical use of this preclinical model for drug discovery is illustrated with data from a study on the chemotherapeutic effects of HER2-targeted therapy.

Prognostic significance of phosphorylated RON in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is the most common type of esophageal cancer. RON is a transmembrane receptor overexpressed in various cancers; however, the clinical significance of its phosphorylated form (pRON) is not fully deciphered. This report is the first to investigate the expression and clinical significance of pRON in human ESCC. Quantitative polymerase chain reaction revealed an up-regulation of RON mRNA in 70% (7/10) of ESCC tissues when compared to the adjacent nontumor tissues. An overexpression of pRON protein was found in most of the ESCC cell lines studied (4/5) when compared to two non-neoplastic esophageal epithelial cells using immunoblot. In 64 ESCC tissues, pRON was localized at the cell membrane, cytoplasm and nucleus in 15 (23.4%), 63 (98.4%) and 61 (95.3%) cases using immunohistochemistry. Patients having high expression of cytoplasmic pRON significantly associated with shorter median survival when compared to those with low expression (25.41 months vs. 14.43 months), suggesting cytoplasmic pRON as a potential marker for poor prognosis in ESCC patients.

The LIM domain protein, CRIP2, promotes apoptosis in esophageal squamous cell carcinoma

The group 2 LIM domain protein, Cysteine-rich intestinal protein 2 (CRIP2) was found to play an important role in esophageal squamous cell carcinoma (ESCC) tumorigenesis. Subcellular fractionation studies show that CRIP2 is expressed in the nucleus. Real-time quantitative PCR shows CRIP2 expression is down-regulated in ESCC tissues and cell lines. Functional studies reveal that CRIP2 reduces colony formation, growth, and invasion abilities. Furthermore, over-expression of CRIP2 induces apoptosis through induction of active caspases 3 and 9 proteins. In conclusion, this study shows CRIP2 plays an important role in the development of ESCC.

Abrogated expression of DEC1 during oesophageal squamous cell carcinoma progression is age- and family history-related and significantly associated with lymph node metastasis

Background:

Oesophageal squamous cell carcinoma (SCC) causes the highest number of cancer deaths in some regions of Northern China. Previously, we narrowed down a critical region at 9q33-34, identified to be associated with tumour-suppressive function of deleted in oesophageal cancer 1 (DEC1) in oesophageal SCC.

Methods:

We generated DEC1 antibody and constructed tissue microarrays (TMAs) utilising tissue specimens from Henan, a high-risk region for oesophageal SCC, to investigate the importance of DEC1 expression in this cancer.

Results:

Tissue microarray immunohistochemical staining reveals significant loss of DEC1 from hyperplasia, to tumour, and to lymph node metastasis. In addition, the loss of DEC1 in tumour is age-dependent. Interestingly, there is significant abrogation of DEC1 expression in patients with a family history of oesophageal SCC. Deleted in oesophageal cancer 1 localises to both the cytoplasm and nucleus. The vesicular pattern of DEC1 in the cytoplasm appears to localise at the Golgi and Golgi–endoplasmic reticulum intermediate compartment.

Conclusion:

This is the first TMA study to suggest a clinical association of DEC1 in lymph node metastatic oesophageal SCC, early onset oesophageal SCC and familial oesophageal SCC development. Subcellular localisation of DEC1 and its expression in oesophageal SCC tissues provide important insight for further deciphering the molecular mechanism of DEC1 in oesophageal SCC development.

Establishment of a novel human esophageal squamous cell carcinoma cell line (ESC-410) and its partial biological characterization

Esophageal cancer exhibits an uneven geographical distribution strikingly, resulting in focal endemic high-incidence areas in several countries worldwide including China, which might be associated with the environmental and genetic risk factors in those areas. Permanent cancer cell lines are invaluable tools in understanding the biology of cancers and experimental therapeutics. To enrich cell line panel and animal models of human esophageal squamous cell carcinoma (ESCC) from different geographical areas and investigate the environmental and genetic risk factors in the carcinogenesis of ESCC, a novel human esophageal squamous cancer cell line (ESC-410) was established. The cell line grew adherent as a monolayer and maintained stable growth rate with a doubling time of 53 h and distinct epithelial morphological appearance; it was maintained in vitro for 18 months and subcultured for more than 50 passages. Ultrastructural examination revealed large irregular nuclei, desmosome, and tonofilaments; karyotype analysis showed a modal number of chromosomes that ranged from 35 to 73, with a median of 57, and 77% of analyzed cells were hyperdiploidy; reverse transcription polymerase chain reaction (RT-PCR) detected the mRNA expressions of CK8, CK18, and CK19 in the established cells; immunofluorescence assay identified the protein expressions of neurotrophin receptor p75 and integrin α6 (CD49f) in the ESC-410 cell line; xenotransplantation of ESC-410 cells into athymic nude mice subcutaneously induced the formation of solid tumor masses in about 2 weeks. By histopathological examination, heterogeneity of xenograft tumor was observed, as same as that of human primary ESCC. All findings and evidence in this experimental study suggested that this cell line might be a useful model in vitro and in vivo in cellular and molecular studies as well as in testing novel therapies for human ESCC.

Impact of G₂ checkpoint defect on centromeric instability

Centromeric instability is characterized by dynamic formation of centromeric breaks, deletions, isochromosomes and translocations, which are commonly observed in cancer. So far, however, the mechanisms of centromeric instability in cancer cells are still poorly understood. In this study, we tested the hypothesis that G(2) checkpoint defect promotes centromeric instability. Our observations from multiple approaches consistently support this hypothesis. We found that overexpression of cyclin B1, one of the pivotal genes driving G(2) to M phase transition, impaired G(2) checkpoint and promoted the formation of centromeric aberrations in telomerase-immortalized cell lines. Conversely, centromeric instability in cancer cells was ameliorated through reinforcement of G(2) checkpoint by cyclin B1 knockdown. Remarkably, treatment with KU55933 for only 2.5 h, which abrogated G(2) checkpoint, was sufficient to produce centromeric aberrations. Moreover, centromeric aberrations constituted the major form of structural abnormalities in G(2) checkpoint-defective ataxia telangiectasia cells. Statistical analysis showed that the frequencies of centromeric aberrations in G(2) checkpoint-defective cells were always significantly overrepresented compared with random assumption. As there are multiple pathways leading to G(2) checkpoint defect, our finding offers a broad explanation for the common occurrence of centromeric aberrations in cancer cells.

Mammary serine protease inhibitor inhibits epithelial growth factor-induced epithelial-mesenchymal transition of esophageal carcinoma cells

BACKGROUND

By using proteomic technology, the authors previously observed the substantial down-regulation of mammary serine protease inhibitor (maspin) in esophageal squamous cell carcinoma and metastases. In the current study, they examined the effects of maspin re-expression in a maspin-null esophageal cancer cell line EC109 and also investigated the underlying mechanism.

METHODS

A cell line with stable maspin expression was established. An epithelial growth factor (EGF)-induced epithelial-mesenchymal transition (EMT) model was used to mimic some aspects of the metastatic process in vitro. The effects of maspin reintroduction on EGF-induced EMT and cell growth characteristics were evaluated. Comparative proteomic analysis of transfected cells versus parental cells was then performed to explore the potential mechanism.

RESULTS

The introduction of maspin into EC109 cells was able to inhibit EGF-induced EMT and altered cell growth characteristics, including the serum dependence, proliferative response to EGF stimulation, and colony formation ability in soft agar, indicating a conversion from a malignant phenotype to a benign phenotype. Proteomic analysis revealed a significant down-regulation of a group of glycolytic enzymes in maspin-transfected cells. In addition, maspin-transfected cells expressed much lower levels of hypoxia-inducible factor 1alpha than parental cells or empty vector transfected cells.

CONCLUSIONS

Maspin exhibited a metastasis-suppressive effect, which may be a consequence of the reversal of the malignant phenotype of EC109 cells. The switch of cellular metabolic phenotype to low glycolysis by the gain of maspin function may play a key role in the process. This finding provides additional evidence of the tumor metastasis-suppressive activity of maspin and may indicate a new direction for future studies of the mechanism of maspin.

Early upregulation of cyclooxygenase-2 in human papillomavirus type 16 and telomerase-induced immortalization of human esophageal epithelial cells

BACKGROUND AND AIM

Cyclooxygenase-2 (COX-2) plays an important role in the carcinogenesis of esophageal squamous cell carcinoma (ESCC). However, it is not clear whether COX-2 is involved in the early or late stage of the development of ESCC. The aim of this study was to investigate the role of COX-2 in the carcinogenesis of ESCC by an immortalized esophageal epithelial cell line.

METHODS

Human papillomavirus type 16 (HPV16)-E6/E7 and human telomerase reverse transcriptase (hTERT) transfection were used for immortalization of esophageal epithelial cells. COX-2-specific RNA interference was used for the inhibition of COX-2 expression.

RESULTS

An immortalized esophageal epithelial cell line, NE6-E6E7/hTERT, was established, which had high proliferation activity but failed to induce colony formation in soft agar. COX-2 expression was upregulated in the early process of immortalization, while COX-2 small interfering RNA (siRNA) decreased the Bcl-2 expression, increased the expression of Bax, and induced cell-cycle arrest at the G0/G1 phase in NE6-E6E7/hTERT cells. Expressions of p53, cyclinD1, and the ratio of hyperphosphorylated-RB/hypophosphorylated-RB were progressively increased after E6E7 and the subsequent hTERT transfections. These changes were accompanied by the alteration of COX-2 expression, but could be reversed by COX-2 siRNA (P < 0.05). P16 expression was significantly downregulated in NE6-E6E7 or NE6-E6E7/hTERT cells (P < 0.05), and was not affected by COX-2 siRNA.

CONCLUSIONS

Our results suggest that induction of cyclooxygenase-2 is essential in the human papillomavirus type 16 and hTERT-induced immortalization of human esophageal epithelial cells, and that COX-2 inhibition may be a potential target to block the carcinogenesis of ESCC at the precancerous stage.

Frequent decreased expression of candidate tumor suppressor gene, DEC1, and its anchorage-independent growth properties and impact on global gene expression in esophageal carcinoma

Previous studies showed that expression of the novel candidate tumor suppressor gene, DEC1 (Deleted in Esophageal Cancer 1), is reduced in esophageal carcinoma and suppresses cancer cell growth in vitro and tumor growth in vivo in nude mice. This study shows that DEC1 gene expression was downregulated in 100% of 16 esophageal squamous cell carcinoma (ESCC) cell lines and 52 and 45%, respectively, of esophageal tumor specimens from Hong Kong and a high-risk ESCC region of Henan, China. Using epitope tagging, the DEC1 protein was localized to both the cytoplasm and nucleus of the cell. In 3D Matrigel culture, no significant difference in colony numbers formed was observed for DEC1 stable transfectants, as compared to vector-alone transfectant controls. However, significantly smaller colony sizes were observed for the DEC1 transfectants. In in vitro cell migration, invasion and soft agar assays of DEC1 transfectants, only the soft agar assay showed statistically significant differences in colony numbers with the vector-alone controls, indicating that DEC1 may be involved in anchorage-independent cell growth. In addition, the global gene expression affected by DEC1 in tumor-suppressive stable transfectants was investigated using cDNA oligonucleotide microarray hybridization. Three candidate genes, TFPI-2, GDF15 and DUSP6, were identified through this approach; they are downregulated in tumor segregants of DEC1 stable transfectants, ESCC cell lines and esophageal tumors and have a potential role in tumor growth and progression. These studies show that DEC1 is involved in esophageal cancer development and help elucidate its functional role in tumor development.

Characterization of one newly established esophageal cancer cell line CSEC from a high-incidence area in China

The Chaoshan littoral is located in a high-incidence area of esophageal cancer in the south of China. In this study, a new esophageal cancer cell line CSEC was established from a 47-year-old female Chinese patient in this district. The biological characters of the cultured cells were investigated, including morphology, ultrastructure, growth kinetic features, tumorigenicity, expression of tumor-associated antigen and cytogenetic features. CSEC cell line grew continuously with a doubling time of 39.5 h and had been passaged over 80 times. The CSEC cells possessed features of squamous epithelial cells with cytokeratin indicated by immunohistochemical staining and tonofilaments and desmosomes revealed by electron microscopy. Tumorigenicity to severe combined immunodeficient mice was confirmed and the tumors developed revealed well-differentiated squamous cell carcinoma, similar to the origin tumor from which the cell line derived. The cytogenetic analysis demonstrated hypertetraploid karyotypes. Chromosome structure aberrations were common and complicated. Immunohistochemical staining showed that CSEC cells were infected with HPV and over-expressed p53. In summary, the CSEC cell line is a well-differentiated esophageal squamous cell carcinoma cell line from a high-incidence area in southern China. It may provide a useful model for the pathogenesis and therapeutic research of esophageal squamous cell carcinoma.

Establishment and characterization of a new xenograft-derived human esophageal squamous cell carcinoma cell line HKESC-4 of Chinese origin

A new human esophageal cancer cell line, HKESC-4, was established from a nude-mouse xenograft of a moderately differentiated esophageal squamous cell carcinoma (ESCC) developed from a 65-year-old Hong Kong Chinese man. The cellular characteristics (morphological, electron microscopic, and immunohistochemical studies), tumorigenicity in athymic nude mice, cytogenetic features, and DNA ploidy of the cell line were investigated. The cell line was maintained in vitro for 17 months and passaged 80 times. HKESC-4 grew as a monolayer, with a doubling time of 63 hours. The epithelial nature of HKESC-4 included the presence of cytokeratin intermediate filaments, as shown by antibodies (AE1/AF3, CAM5.2, and MAK 6), and the presence of the tonofilaments, as seen under electron microscopy. HKESC-4 was tumorigenic in nude mice and had DNA aneuploidy. The cytogenetic abnormalities of HKESC-4 included -1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, -15, -16, -17, -18, -19, +20, -21, -22, +del(11)(p11), +i(11)(q10), and +21 marker chromosomes. Comparative genomic hybridization analysis demonstrated chromosomal gains at 1p36.13, 3q23 approximately q28, 5p15.33 approximately p15.1, 6p25.1 approximately p22.3, 7p21.3 approximately p11.2, 7q11.21 approximately q21.13, 8q23.3 approximately q23.3, 11p11.2, 11q12.1 approximately q13.2, 14q21.3 approximately q32.2, 17p13.3, 18p11.32 approximately p11.31, and 20p13 approximately p12.2 and chromosomal losses at 1q12, 2p25.1 approximately p24.3, 13p13 approximately p11.2, 21p, 22p13 approximately p11.2, and Y. The newly established cell line HKESC-4 promises to be a useful tool in future studies of molecular pathogenesis and therapeutics in ESCC.

The major 8p22 tumor suppressor DLC1 is frequently silenced by methylation in both endemic and sporadic nasopharyngeal, esophageal, and cervical carcinomas, and inhibits tumor cell colony formation

Identification of tumor suppressor genes (TSG) silenced by methylation uncovers mechanisms of tumorigenesis and identifies new epigenetic tumor markers for early cancer detection. Both nasopharyngeal carcinoma (NPC) and esophageal carcinoma are major tumors in Southern China and Southeast Asia. Through expression subtraction of NPC, we identified Deleted in Liver Cancer 1 (DLC1)/ARHGAP7 (NM_006094)--an 8p22 TSG as a major downregulated gene. Although expressed in all normal tissues, DLC1 was silenced or downregulated in 11/12 (91%) NPC, 6/15 (40%) esophageal, 5/8 (63%) cervical and 3/9 (33%) breast carcinoma cell lines. No genetic deletion of DLC1 was detected in NPC although a hemizygous deletion at 8p22-11 was found by 1-Mb array-CGH in some cell lines. We then located the functional DLC1 promoter by 5'-RACE and promoter activity assays. This promoter was frequently methylated in all downregulated cell lines and in a large collection of primary tumors including 89% (64/72) NPC (endemic and sporadic types), 51% (48/94) esophageal, 87% (7/8) cervical and 36% (5/14) breast carcinomas, but seldom in paired surgical marginal tissues and not in any normal epithelial tissue. The transcriptional silencing of DLC1 could be reversed by 5-aza-2'-deoxycytidine or genetic double knock-out of DNMT1 and DNMT3B. Furthermore, ectopic expression of DLC1 in NPC and esophageal carcinoma cells strongly inhibited their colony formation. We thus found frequent epigenetic silencing of DLC1 in NPC, esophageal and cervical carcinomas, and a high correlation of methylation with its downregulation, suggesting a predominant role of epigenetic inactivation. DLC1 appears to be a major TSG implicated in the pathogenesis of these tumors, and should be further tested as a molecular biomarker in patients with these cancers.

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Identification of a tumor suppressive critical region mapping to 3p14.2 in esophageal squamous cell carcinoma and studies of a candidate tumor suppressor gene, ADAMTS9

A gene critical to esophageal cancer has been identified. Functional studies using microcell-mediated chromosome transfer of intact and truncated donor chromosomes 3 into an esophageal cancer cell line and nude mouse tumorigenicity assays were used to identify a 1.61 Mb tumor suppressive critical region (CR) mapping to chromosome 3p14.2. This CR is bounded by D3S1600 and D3S1285 microsatellite markers. One candidate tumor suppressor gene, ADAMTS9, maps to this CR. Further studies showed normal expression levels of this gene in tumor-suppressed microcell hybrids, levels that were much higher than observed in the recipient cells. Complete loss or downregulation of ADAMTS9 gene expression was found in 15 out of 16 esophageal carcinoma cell lines. Promoter hypermethylation was detected in the cell lines that do not express this gene. Re-expression of ADAMTS9 was observed after demethylation drug treatment, confirming that hypermethylation is involved in gene downregulation. Downregulation of ADAMTS9 was also found in 43.5 and 47.6% of primary esophageal tumor tissues from Hong Kong and from the high-risk region of Henan, respectively. Thus, this study identifies and provides functional evidence for a CR associated with tumor suppression on 3p14.2 and provides the first evidence that ADAMTS9, mapping to this region, may contribute to esophageal cancer development.

Expression of candidate chromosome 3p21.3 tumor suppressor genes and down-regulation of BLU in some esophageal squamous cell carcinomas

The expression of six chromosome 3p21.3 candidate tumor suppressor genes (BLU, FUS2, HYAL2, NPRL2, RASSF1A, and SEMA3B) in esophageal squamous cell carcinoma (ESCC) has been investigated. Reduced expression of BLU was detected in some ESCC cell lines and tumor tissues and the difference was quantitated by real-time quantitative polymerase chain reaction. Methylation specific-PCR revealed the down-regulation of BLU by epigenetic inactivation. However, exogenous expression of BLU did not functionally suppress tumorigenicity in nude mice. These results suggest that over-expression of BLU alone is not sufficient to inhibit tumorigenicity. Further studies on BLU interacting proteins are required to elucidate the possible role of BLU in the development of ESCC.

Cytogenetic aberrations in immortalization of esophageal epithelial cells

To define the early cytogenetic events important in esophageal carcinogenesis, we immortalized normal esophageal epithelial cells by overexpression of human papillomavirus type 16 E6/E7 (HPV16E6/E7) and human telomerase reverse transcriptase (hTERT), and characterized the chromosomal abnormalities serially before and after cellular immortalizaiton. During crisis, most cells had simple nonclonal karyotypic changes with cytogenetic divergence. Mitotically unstable chromosomes (i.e., telomere association and dicentric chromosomes) were the most common aberrations. After crisis, the karyotypic patterns were more convergent with nonrandom clonal changes. A few clones dominated the culture. Gain of chromosome 20q was consistently observed in four HPVE6/E7 immortalized esophageal lines, whereas amplification of chromosome 5q was preferentially found in hTERT immortalized cells. In addition, chromosomal aberrations of immortalized cells, including del(3p) and centromere rearrangements, were similar to those observed in esophageal cancer. Furthermore, in E6/E7-expressing cells, the frequency of negative telomere termini and anaphase bridges were high during crisis and low after crisis. These findings suggested that telomere dysfunction might be an important cause of cellular crisis, and the resultant chromosomal aberrations, mainly amplification of chromosome 20q or 5q, might be early genetic events required in esophageal cell immortalization. These alterations might be valuable models for further study of molecular mechanisms contributing to esophageal carcinogenesis.

Hepatocyte growth factor promotes cancer cell migration and angiogenic factors expression: a prognostic marker of human esophageal squamous cell carcinomas

PURPOSE

Hepatocyte growth factor/scatter factor (HGF/SF) and its receptor, c-Met, play important roles in tumor development and progression. In this study, we measured the serum HGF levels in patients with esophageal squamous cell carcinoma (ESCC) to evaluate its relationships with clinicopathologic features and the role of HGF in ESCC.

EXPERIMENTAL DESIGN

One hundred and forty-nine patients with ESCC were studied. Pretherapy serum was collected and ELISA was used to detect the concentrations of HGF, vascular endothelial growth factor (VEGF), and interleukin 8 (IL-8). The function of HGF was shown by invasion chamber assay.

RESULTS

Pretherapy serum HGF was found to be significantly higher in patients with ESCC than in control subjects. The levels of HGF correlated significantly with advanced tumor metastasis stage and survival. Multivariate analyses showed that serum HGF level in cell migration was an independent prognostic factor. Increased HGF serum levels correlated positively with serum levels of VEGF and IL-8. Our results also showed that HGF was overexpressed in ESCC tissues and cell lines. In vitro study showed that HGF could stimulate ESCC cell to express VEGF and IL-8 and markedly enhance invasion and migration of ESCC cells. Furthermore, HGF-induced IL-8 and VEGF expression was dependent on extracellular signal-regulated kinase signaling pathways. The inhibition of extracellular signal-regulated kinase activation reduced HGF-mediated IL-8 and VEGF expression.

CONCLUSIONS

Our results suggest that serum HGF may be a useful biomarker of tumor progression and a valuable independent prognostic factor in patients with ESCC. HGF may be involved in the progression of ESCC as an autocrine/paracrine factor via enhancing angiogenesis and tumor cell invasion and migration.

Tumor suppressive role of a 2.4 Mb 9q33-q34 critical region and DEC1 in esophageal squamous cell carcinoma

The key genes involved in the development of esophageal squamous cell carcinoma (ESCC) remain to be elucidated. Previous studies indicate extensive genomic alterations occur on chromosome 9 in ESCC. Using a monochromosome transfer approach, this study provides functional evidence and narrows down the critical region (CR) responsible for chromosome 9 tumor suppressing activity to a 2.4 Mb region mapping to 9q33-q34 between markers D9S1798 and D9S61. Interestingly, a high prevalence of allelic loss in this CR is also observed in primary ESCC tumors by microsatellite typing. Allelic loss is found in 30/34 (88%) tumors and the loss of heterozygosity (LOH) frequency ranges from 67 to 86%. Absent to low expression of a 9q32 candidate tumor suppressor gene (TSG), DEC1 (deleted in esophageal cancer 1), is detected in four Asian ESCC cell lines. Stably expressing DEC1 transfectants provide functional evidence for inhibition of tumor growth in nude mice and DEC1 expression is decreased in tumor segregants arising after long-term selection in vivo. There is 74% LOH in the DEC1 region of ESCC primary tumors. This study provides the first functional evidence for the presence of critical tumor suppressive regions on 9q33-q34. DEC1 is a candidate TSG that may be involved in ESCC development.

Inactivation mechanisms and growth suppressive effects of p16INK4a in Asian esophageal squamous carcinoma cell lines

The inactivation mechanisms and functional role of p16INK4a in three Asian esophageal squamous cell carcinoma (ESCC) cell lines were investigated by polymerase chain reaction (PCR) amplification, DNA sequencing, methylation-specific PCR analysis, reverse transcription-PCR, Western blotting, and colony formation assays. The p16INK4a was inactivated by promoter hypermethylation in all three cell lines, a homozygous deletion of exons 2 and 3, and a frameshift deletion on exon 1, leading to transcriptional silencing or the production of mutant p16INK4a protein. Two ESCC cell lines transfected with wild type p16INK4a show significantly reduced cell growth properties. The results of the present studies support the suppressive role of p16INK4a in ESCC development.

Antiproliferative activity of the extract of Gleditsia sinensis fruit on human solid tumour cell lines

BACKGROUND

The fruit extract of Gleditsia sinensis Lam. (GSE) is a traditional herbal medicine that is saponin-rich. However, its activity on solid tumour cell lines has never been demonstrated.

METHODS

The activity of GSE was demonstrated in four cancer cell lines (breast cancer MCF-7, MDA-MB231, hepatoblastoma HepG2 and oesophageal squamous carcinoma cell line SLMT-1) using MTT assay, anchorage-independent clonogenicity assay, DNA laddering and in situ cell death detection.

RESULTS

The mean MTT(50) (the mean concentration of GSE to reduce MTT activity by 50%) ranged from 16 to 20 microg/ml of GSE. An anchorage-independent clonogenicity assay showed that all of the four solid tumour cell lines gradually lost their regeneration potential after treatment with GSE, DNA fragmentation and TUNEL analysis demonstrated that the action of GSE is both dose- and time course-dependent.

CONCLUSIONS

Our results suggest that GSE has a cytotoxic activity and can induce apoptosis in human solid tumour cell lines.