Higher expression of SIRT1 induced resistance of esophageal squamous cell carcinoma cells to cisplatin

Background

High expression of Sirtuin type 1 (SIRT1) exists in some cancer cells. However, it is still unclear whether SIRT1 affects the sensitivity of esophageal cancer cells to cisplatin. This study was designed to explore the relationship between SIRT1 expression and resistance of esophageal squamous cell carcinoma (ESCC) cells to cisplatin and reveal the underlying mechanism.

Methods

The tissue samples of 68 ESCC patients were collected from Nanjing Drum Tower Hospital, China. All the patients had undergone cisplatin based combination chemotherapy. The expression of SIRT1and Noxa in tissue samples were analyzed by quantitative real-time reverse PCR (qRT-PCR) and Western blot. Human ESCC cell line (ECa9706 cells) was cultured and a cisplatin-resistant subline (ECa9706-CisR cells) was established by continuous exposure to cisplatin at different concentrations. The expression of SIRT1 and Noxa in both cell lines was analyzed by qRT-PCR and Western blot. siRNA technology was utilized to down-regulate the SIRT1 expression in ECa9706-CisR cells. The influence of SIRT1 silence on sensitivity of ECa9706-CisR cells to cisplatin was confirmed using CCK-8 assay and flow cytometry. Furthermore, the level change of Noxa after SIRT1 silence in ECa9706-CisR cells was determined by qRT-PCR and Western blot.

Result

SIRT1 and Noxa expression in chemo-resistant patients was significantly increased and decreased respectively, compared with chemo-sensitive patients. SIRT1 expression in ECa9706-CisR cells was significantly increased with a lower Noxa level, compared with normal ECa9706 cells. Cisplatin 5 µM could cause proliferation inhibition, G2/M phase arrest and apoptosis in ECa9706-CisR cells and these effects could be enhanced dramatically by SIRT1 silencing. Moreover, Noxa expression was increased after treated with SIRT1 siRNA.

Conclusions

Over-expression of SIRT1 may cause resistance of ESCC cells to cisplatin through the mechanism involved with Noxa expression.     

Prognostic relevance and therapeutic implications of centromere protein F expression in patients with esophageal squamous cell carcinoma

Centromere protein F (CENP‐F), a cell cycle‐regulated centromere protein, has been shown to affect numerous tumorigenic processes. This study aimed to clarify the prognostic significance of CENP‐F expression in patients with esophageal squamous cell carcinoma (ESCC). The levels of CENP‐F messenger RNA and protein were higher in ESCC cell lines than in the normal tissues. An immunohistochemical analysis of paired tissue specimens showed that the CENP‐F expression was higher in tumorous tissues than in the adjacent non‐tumorous tissues (P < 0.001). Moreover, there was a significant correlation between CENP‐F expression and gender (P = 0.012), clinical stage (P = 0.039), and T classification (P = 0.026). Patients with higher CENP‐F expression had shorter overall survival than those with lower CENP‐F expression (P = 0.009). Multivariate Cox analysis indicated that CENP‐F expression is an independent prognostic factor for overall survival (hazard ratio = 0.582, 95% confidence interval = 0.397–0.804, P = 0.041). Importantly, it was found that zoledronic acid (ZOL) could significantly enhance the chemotherapeutic sensitivity of ESCC cell lines with high CENP‐F expression to cisplatin, although ZOL alone only exhibited a minor inhibitory effect to ESCC cells. In summary, these findings demonstrate that CENP‐F may serve as a valuable molecular marker for predicting the prognosis of ESCC patients. In addition, the data indicate a potential benefit of combining ZOL with cisplatin in ESCC, suggesting that CENP‐F expression may have therapeutic implications.     

The role of mitochondrial folate enzyme MTHFD1L in esophageal squamous cell carcinoma

Objective: The lack of novel therapeutic targets poses the major challenge to prolong survival and improve the quality of life for esophageal squamous cell carcinoma (ESCC). Methylenetetrahydrofolate dehydrogenase 1-like (MTHFD1L) plays critical roles in folate cycle maintenance. However, little information is available concerning the role of MTHFD1L in cancer cells, and no studies have addressed such issues in esophageal cancer.

Materials and method: Surgical cancer and adjacent normal esophageal tissues were obtained from patients with esophagectomy and esophagogastrostomy for ESCC. Western blot, immunohistochemistry and Quantitative RT-PCR were performed to evaluate protein and RNA expression levels of MTHFD1L. Knockdown of MTHFD1L expression was achieved by using short hairpin RNA. The effects of MTHFD1L silencing on ESCC cell proliferation and apoptosis were assessed by the MTT assay, Celigo assays, Annexin V FACS assay and Caspase-3/7 array in vitro.

Results: Twenty-three paired cancer and adjacent normal esophageal tissues from patients with ESCC were included in this study. MTHFD1L protein and RNA expression levels were significantly upregulated in ESCC tissue as compared with normal tissue. High expression of MTHFD1 was also detected in two esophageal cancer cell lines (TE-1 and EC109). Knockdown of MTHFD1L expression inhibited the proliferation of TE-1 cells, and the apoptosis was distinctly increased following shMTHFD1L infection.

Conclusions: Our preliminary study highlighted for the first time that MTHFD1L might be involved in the development of ESCC, which may provide a new potential tumor-specific therapeutic targeting for anti-folate agents.     

Nanog siRNA plus Cisplatin may enhance the sensitivity of chemotherapy in esophageal cancer

Background

Cancer stem cells are regarded as the origin of tumors that can proliferate, relapse, and metastasize. Nanog, with its capacity to maintain the pluripotency and regulate proliferation and prevent differentiation, is one of the most important core markers of cancer stem cells. Studying the role of Nanog in esophageal squamous cell carcinoma (ESCC), therefore, has important implications.

Methods

In the present study, we first detected the expression of Nanog in the ESCC and cell lines by RT-PCR, immunofluorescence, and immunohistochemisty. Then, we used small interfering RNA (siRNA) to block Nanog expression while evaluating the effect of Nanog siRNA on cell apoptosis and the combined effects with Cisplatin in ESCC cell lines.

Results

The results showed that both mRNA and protein-level Nanog are overexpressed in ESCC tissues compared with their normal counterparts, and the increased occurrence of Nanog expression was positively correlated with TNM stages and histopathological differentiation of ESCC patients (p?Conclusion The present study’s results suggest that detecting Nanog might be helpful for diagnosing ESCC, and Nanog siRNA combined with Cisplatin may be a feasible strategy to enhance the sensitivity of chemotherapy in patients with ESCC.     

c-IAP1在食管鳞癌中的表达及其对化疗敏感性的影响

目的:探讨食管鳞癌细胞凋亡抑制蛋白1(c-IAP1)表达与化疗敏感性的相关性.方法:食管鳞癌组织芯片免疫组织化学染色,分析食管鳞癌组织及其配对癌旁食管上皮中c-IAP1的表达和定位及其与肿瘤,临床分级的关系.免疫印迹分析食管癌细胞C-IAP1和Smac表达,用RNA干扰技术敲降Smac表达,MTT法检测细胞对化疗药物敏...     

Overexpression of HSP47 in esophageal squamous cell carcinoma: clinical implications and functional analysis

Several biomarkers of esophageal squamous cell carcinoma (ESCC) have been explored to improve the prognosis of this disease. One of these, the 47‐kDa heat shock protein (HSP47), has been screened as a potential biomarker by genomic profiling and is known to be overexpressed in some malignant diseases. In this study, we explored the role and evaluated the prognostic value of HSP47 expression in ESCC. The function of this protein was analyzed by assaying proliferation, wound healing, and colony formation in an HSP47‐knockdown ESCC line. The prognostic implication of HSP47 expression was analyzed by immunohistochemical staining in 157 surgical specimens. HSP47 expression level and other clinical variables were analyzed using multivariate Cox proportional hazards models. Silencing of the HSP47 gene in the ESCC cell line inhibited cell proliferation and colony formation. HSP47 was highly expressed in ESCC tissue samples, compared with normal esophageal tissues. The level of immunohistochemical staining of HSP47 and pathologic stage were significantly correlated with overall and recurrence‐free survival, as shown by multivariate analysis (P = 0.014 and 0.044, respectively). We found that overexpression of HSP47 is associated with poor prognosis in patients with ESCC and that this is consistent with the function of HSP47 in terms of increased cell proliferation and colony formation. These results suggest that HSP47 is a potential prognostic biomarker for ESCC and merits further research for novel diagnostic and therapeutic applications.     

Expression and significance of ASPP2 in squamous carcinoma of esophagus

To study the significance of apoptosis stimulating protein of P53 2 (ASPP2) expression in esophageal squamous cell carcinoma (ESCC), immunohistochemistry S-P method was used to examine the expression of ASPP2 in 136 cases of ESCC, 35 cases of high grade intraepithelial neoplasia (HGIN), 29 cases of low grade intraepithelial neoplasia (LGIN) and 37 cases of normal esophageal epithelium (NEE). The associations of ASPP2 expression with clinicopathological data and overall survival (OS) were also analyzed. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to evaluate ASPP2 expression in a total of 20 matched human ESCC tumor tissues and normal adjacent tissues (NAT). In addition, EC109 cells were treated with cisplatin (CDDP) in vitro for 24 h (the intervention group) and the control group was set up at the same time. Western blot was used to examine the expression of ASPP2 protein between the two groups. The expression of ASPP2 decreased progressively from NEE to LGIN, to HGIN, and to ESCC, and it was related to TNM stage, histological differentiation and lymph node metastasis in ESCC (P < 0.05). ASPP2 was a protective factor of patients with ESCC (P = 0.008). The relative expression of ASPP2 mRNA was markedly downregulated in ESCC compared with the paired NAT (P < 0.01). Western blot results showed that cells in the intervention group could express ASPP2 while there was no expression of ASPP2 in the control group. Taken together, these results indicate that the abnormal expression of ASPP2 may play an important role for development and metastasis in ESCC.     

High Expression of BCCIP β Can Promote Proliferation of Esophageal Squamous Cell Carcinoma

Background

BCCIP was originally identified as a BRCA2 interacting protein in humans and Ustilago maydis. It had low expression in some human cancer tissues. However, recent research indicated that many caretaker genes are also necessary for cell viability and their expression could contribute to tumor progression.

Aim

To characterize whether BCCIP is a caretaker gene in esophageal squamous cell carcinoma (ESCC).

Methods

Western blotting and immunohistochemistry were used to measure the expression of BCCIP β. In vitro studies were used to verify the effects of BCCIP β in Eca109 cells.

Results

Expression of BCCIP β was notably higher in tumor tissues of ESCC and Eca 109 cells. Meanwhile, the immunohistochemistry stain revealed that BCCIP β was positively correlated with clinical pathologic variables such as tumor size and tumor grade, as well as Ki-67, and prompted poor prognosis. In vitro studies such as starvation and refeeding assay along with BCCIP β-shRNA transfection assay demonstrated that BCCIP β expression promoted proliferation of ESCC cells. In addition, BCCIP β downregulation by silencing RNA significantly decreased the rate of colony formation, alleviated cellular apoptosis and increased the chemosensitivity of cisplatin.

Conclusions

This research first put forward that BCCIP β is an oncogene in human ESCC and contributes to the poor outcome of the deadly disease.

     

Upregulation of the Long Non-coding RNA PlncRNA-1 Promotes Esophageal Squamous Carcinoma Cell Proliferation and Correlates with Advanced Clinical Stage

Background

Recent studies revealed that long noncoding RNAs (lncRNAs) play critical regulatory roles in cancer biology. PlncRNA-1 is one of lncRNAs that is associated with cell apoptosis and proliferation of prostate cancer.

Aim

This study aimed to assess the potential role of PlncRNA-1 in the pathogenesis of esophageal squamous cell carcinoma (ESCC).

Materials and Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression level of PlncRNA-1 in 73 pairs of ESCC and their matched normal tissues. The correlation of PlncRNA-1 with clinicopathological features and clinical stages was also analyzed. Cancer cell proliferation and apoptosis were assessed following knock-down of PlncRNA-1 by MTT, colony formation assay, and flow cytometry.

Results

The expression of PlncRNA-1 was significantly higher in human ESCC compared with the adjacent noncancerous tissues (69.8 %, p < 0.05), and the high level of PlncRNA-1 expression was significantly correlated with advanced clinical stage (p < 0.01) and lymph node metastasis (p < 0.05). Furthermore, knockdown of PlncRNA-1 reduced cell proliferation and increased the apoptosis in vitro.

Conclusions

PlncRNA-1 plays an important role in ESCC cell proliferation. Overexpression of PlncRNA-1 is correlated with advanced tumor stage and lymph node metastasis, and may serve as a potential prognostic marker and therapeutic target for ESCC.     

Original article: Upregulation of caspase‐3 expression in esophageal cancer correlates with favorable prognosis: an immunohistochemical study from a high incidence area in northern China

Caspase‐3 plays an important role as the key effector during apoptosis, but there are very few studies of caspase‐3 in esophageal squamous cell carcinoma (ESCC). The purpose of this study was to investigate the expression and prognostic significance of caspase‐3 in ESCC from Linzhou City, a high incidence area in northern China. All 64 patients underwent esophagectomy for ESCC between January 2002 and December were enrolled in this study. Caspase‐3 expression was assessed by immunohistochemistry (IHC) in primary ESCC and paired normal esophageal epithelium. The positive rate of caspase‐3 expression was higher in ESCC than in normal esophageal epithelium (79.7% vs. 50.0%, Chi‐square = 12.372, P= 0.001). Caspase‐3 expression was correlated with tumor cell differentiation (Phi = 0.717, P < 0.001), tumor infiltration depth (Phi =?0.334, P= 0.008), and pathologic TNM (pTNM) staging (rs =?0.268, P= 0.032). Patients in caspase‐3 positive group had a significantly better 5‐year overall survival than those in the negative group (77.4% vs. 35.9%, χ²= 7.344, P= 0.007). Our results showed that caspase‐3 expression was upregulated in ESCC compared with normal esophageal epithelium in population of Chinese high incidence area, and patients with caspase‐3 positive expression had better prognosis. Therefore, caspase‐3 immunostaining could be a simple and useful tool for predicting survival in ESCC patients.     

Clinical Impact of HAb18G/CD147 Expression in Esophageal Squamous Cell Carcinoma

Background

HAb18G/CD147 expression has been associated with many tumor invasion molecules, which play important roles in recurrence and poor differentiation of esophageal squamous cell carcinoma (ESCC). However, the clinical implications of HAb18G/CD147 in ESCC are still unclear.

Aims

In this study, we clarified the clinical significance of HAb18G/CD147 and characterized the association between HAb18G/CD147 and tumor invasion in ESCC cases.

Methods

Tumor tissues were obtained from 86 ESCC patients who underwent surgical resection between 2002 and 2005. All patients that had received previous therapy were excluded. ESCC tissues were analyzed by IHC using anti HAb18G/CD147 antibody. The expression of HAb18G/CD147 mRNA in esophageal cancer cell lines was analyzed by RT?CPCR.

Results

HAb18G/CD147 was uniformly expressed in EC109 and EC871214 cell lines, but negatively expressed in EPC2, esophageal normal squamous cell line. HAb18G/CD147 mainly localized to the membrane of tumor cells in 84.9% of ESCC patients (64 out of 86 cases). Furthermore, we also found that higher HAb18G/CD147 expression levels significantly correlated with lymph node metastasis, depth of tumor invasion and differentiation (P < 0.05). But the expression levels of HAb18G/CD147 in lymph node metastatic tissues were almost equal to that in the primary tumor tissues. Furthermore, lymph node metastasis and expression of HAB18G/CD147 were independent prognostic indicators in ESCC.

Conclusions

The expression of HAb18G/CD147 might be involved in the progression and survival of ESCC. Therefore, HAb18G/CD147 could be a clinical marker for the poor prognosis in ESCC patients and may also be a potentially therapeutic target to improve the progression of ESCC.     

Down-Regulation of PTEN Expression Modulated by Dysregulated miR-21 Contributes to the Progression of Esophageal Cancer

Background and Aim

miR-21, a putative tumor oncomiR, is a frequently overexpressed miRNA in a variety of tumors. Because it targets tumor-suppressor genes it has been linked to tumor progression. In this study we investigated the role of miR-21 in esophageal squamous cell carcinoma (ESCC), and its possible mechanism.

Methods

Expression of miR-21 was detected by stem–loop RT-PCR in tissue from 76 invasive ESCC at stage I–IV and in their corresponding para-cancerous histological normal tissues (PCHNT). Thirty endoscopic esophageal mucosal biopsy specimens from non-tumor patients were used as controls. Expression of PTEN in 76 paired ESCC and PCHNT was investigated by real-time RT-PCR and an immunohistochemical method, respectively. Paired tumor and PCHNT specimens of 20 ESCC cases were randomly selected for western blot analysis. The effect of miR-21 on PTEN expression was assessed in the ESCC cell line with an miR-21 inhibitor to reduce miR-21 expression. Furthermore, the roles of miR-21 in cell biology were analyzed by use of miR-21 inhibitor-transfected cells.

Results

Stem–loop RT-PCR revealed miR-21 was significantly overexpressed in ESCC tissues and cell lines. Overexpression of miR-21 correlated with tumor status, lymph node metastasis, and clinical stage. We demonstrated that knockdown of miR-21 significantly increased expression of PTEN protein. Consequent PTEN expression reduced cell proliferation, invasion, and migration.

Conclusions

Our findings suggest that miR-21 could be a potential oncomiR, probably by regulation of PTEN, and a novel prognostic factor for ESCC patients.     

miR-21 Down-Regulation Suppresses Cell Growth, Invasion and Induces Cell Apoptosis by Targeting FASL, TIMP3, and RECK Genes in Esophageal Carcinoma

Background

miR-21 is overexpressed in esophageal squamous cell carcinoma (ESCC) and is thought to be correlated with the development of the cancer. The target gene of miR-21 including FASL, TIMP3 and RECK is revealed by researchers. miR-21 may be involved in the tumorgenesis of ESCC by targeting FASL, TIMP3 and RECK.

Aims

The purpose of this study was to explore the mechanism of miR-21 in the development of ESCC.

Methods

miR-21 expression in ESCC and the matched non-malignant adjacent tissues (NMATs) was examined by qRT-PCR. Cell growth, cell apoptosis and cell invasion ability of EC9706 and EC-1 cells was examined after the cells were transfected with miR-21 inhibitor. The potential target genes of miR-21 including FASL, TIMP3 and RECK were examined by western blot and Luciferase reporter assay.

Results

miR-21 expression was increased significantly in ESCC tissues compared with NMAT. miR-21 down-regulation inhibits cell growth, cell invasion and induces cells to apoptosis. FASL, TIMP3 and RECK are direct targets of miR-21.

Conclusions

miR-21 down-regulation inhibits cell growth, invasion and induces cells to apoptosis by targeting FASL, TIMP3 and RECK genes.     

Protein kinase D1 mRNA level may predict cancer‐specific survival in heavy smokers with esophageal squamous cell cancers

Protein kinase D1 (PRKD1) is a kinase that regulates various pathways, which involve in cell proliferation, apoptosis, cell adhesion and invasion. Although PRKD1 expression has been observed in many cancers, its role in esophageal squamous cell cancer (ESCC) has not been well reported. As its dysregulation in cancers is organ specific, we sought to investigate the potential role of PRKD1 in the progression of ESCC. Samples were collected from 178 patients with completely resected ESCCs at Sun Yat‐sen University Cancer Center, including 47 pairs of tumorous and non‐tumorous tissues. PRKD1 mRNA expression was investigated by quantitative real‐time polymerase chain reaction. Receiver operating characteristic (ROC) curve analysis was used to search for a feasible cut‐off point of PRKD1 mRNA levels for predicting cancer‐specific survival. Kaplan–Meier and multivariate Cox regression analysis were used to assess the prognostic value of PRKD1 mRNA level in ESCC patients. In result, upregulation of PRKD1 mRNA was detected in 55.3% (26/47) of ESCC tissues compared with paired non‐tumorous ones (P = 0.011). ROC analysis indicated 3.28 as a cut‐off point, and thus 72 and 106 tumors with low and high PRKD1 mRNA expression were categorized. High‐PRKD1 mRNA expression in tumors appeared with more frequency in heavy smokers (P = 0.002) and patients with advanced pathological T category (P = 0.034). Kaplan–Meier analysis indicated that patients with low‐PRKD1 mRNA had a longer cancer‐specific survival than the ones with high‐PRKD1 level (P = 0.044). Multivariate analysis showed that tumorous PRKD1 mRNA expression was an independent prognostic factor (hazard ratio: 1.538, 95% confidence interval: 1.018–2.323, P = 0.041) in resected ESCC. Subgroup analysis revealed that the discernibility of PRKD1 mRNA level on ESCC outcomes was only pronounced in heavy smokers (P = 0.002), but not in non‐heavy smokers (P = 0.870). PRKD1 might play a potential oncogenic role in ESCC. It might be an independent biomarker to predict prognosis in heavy smokers with ESCC.     

Effects of DNA methyltransferase 1 inhibition on esophageal squamous cell carcinoma

To explore the role of DNA methyltransferase 1 (DNMT1) in esophageal squamous cell carcinoma (ESCC) and the potential of DNMT1‐targeted small interfering RNA as ESCC therapy, we examined expression changes of DNMT1 in ESCC and investigated the effect of DNMT1 knockdown by RNA interference in a human ESCC cell line, KYSE30. DNMT1 messenger RNA was over‐expressed in seven out of 12 ESCC samples, and the percentage of cells expressing DNMT1 was significantly higher in ESCC tissues compared with paired non‐cancerous tissues. DNMT1 protein levels correlated with lymph node metastasis, but exhibited no correlation with sex, age, tumor site, or tumor differentiation. Knockdown of DNMT1 in KYSE30 cells using RNA interference resulted in a reduction of promoter methylation and re‐expression of methyl‐guanine methyl‐transferase and retinoic acid receptors beta, inhibition of cell proliferation/viability and induction of cell apoptosis. These results indicate that DNMT1 over‐expression is involved in ESCC and correlated with lymph node metastasis. Knockdown of DNMT1 led to promoter demethylation and re‐expression of several tumor suppressor genes thereby inhibiting cell proliferation/viability and inducing cell apoptosis.     

Nicotinic cholinergic receptors in esophagus: Early alteration during carcinogenesis and prognostic value

AIM: To compare expression of nicotinic cholinergic receptors(CHRNs) in healthy and squamous cell carcinoma-affected esophagus and determine the prognostic value.METHODS: We performed RT-q PCR to measure the expression of CHRNs in 44 esophageal samples from healthy individuals and in matched normal surrounding mucosa, and in tumors from 28 patientsdiagnosed with esophageal squamous cell carcinoma(ESCC). Next, we performed correlation analysis for the detected expression of these receptors with the habits and clinico-pathological characteristics of all study participants. In order to investigate the possible correlations between the expression of the different CHRN subunits in both healthy esophagus and tissues from ESCC patients, correlation matrices were generated. Subsequently, we evaluated whether the detected alterations in expression of the various CHRNs could precede histopathological modifications during the esophageal carcinogenic processes by using receiver operating characteristic curve analysis. Finally, we evaluated the impact of CHRNA5 and CHRNA7 expression on overall survival by using multivariate analysis.RESULTS: CHRNA3, CHRNA5, CHRNA7 and CHRNB4, but not CHRNA1, CHRNA4, CHRNA9 or CHRNA10, were found to be expressed in normal(healthy) esophageal mucosa. In ESCC, CHRNA5 and CHRNA7 were overexpressed as compared with patient-matched surrounding non-tumor mucosa(ESCC-adjacent mucosa; P 0.0001 and P = 0.0091, respectively). Positive correlations were observed between CHRNA3 and CHRNB4 expression in all samples analyzed. Additionally, CHRNB4 was found to be differentially expressed in the healthy esophagus and the normalappearing ESCC-adjacent mucosa, allowing for distinguishment between these tissues with a sensitivity of 75.86% and a specificity of 78.95%(P = 0.0002). Finally, CHRNA5 expression was identified as an independent prognostic factor in ESCC; patients with high CHRNA5 expression showed an increased overall survival, in comparison with those with low expression. The corresponding age- and tumor stage-adjusted hazard ratio was 0.2684(95%CI: 0.075-0.97, P = 0.0448).CONCLUSION: Expression of CHRNs is homogeneous along healthy esophagus and deregulated in ESCC, suggesting a pathogenic role for these receptors in ESCC development and progression.     

Long-Term Cisplatin Exposure Promotes Methylation of the OCT1 Gene in Human Esophageal Cancer Cells

Background

Cisplatin-based chemotherapy is widely used for treatment of a variety of human malignant solid and metastatic tumors, including esophageal cancer. However, the clinical effect of this drug is limited because of intrinsic and acquired resistance to it. Organic cation transporters (OCTs) are important in the cellular uptake of cisplatin.

Aim

Our objective was to test the hypothesis that cisplatin resistance is associated with alteration of expression of OCTs.

Methods

Levels of expression of OCTs in paired esophageal cancer and adjacent non-cancerous tissues were examined by use of immunohistochemistry.

Results

We found that OCT1 silencing impaired cisplatin-mediated apoptosis of esophageal cancer cells. The level of OCT1 mRNA in cisplatin-resistant cells was markedly reduced compared with parental cells. Promoter methylation of OCT1 was induced in cisplatin-resistant cells.

Conclusion

This study shows that long-term exposure to cisplatin promotes methylation of the OCT1 gene in human esophageal cancer cells, which in turn results in cisplatin resistance.