To develop novel therapeutic and diagnostic methods for esophageal cancer, it is important to understand the precise biological mechanism. Micro-RNAs (miRNAs) seem to be crucial factors in diverse regulation pathways. In this study, we analyzed the expression of mature miRNAs in esophageal squamous cell carcinoma (ESCC). The expression of 73 miRNAs was quantified by qRT-PCR in 30 primary ESCC specimens. We examined the correlation between miRNA expressions and the clinicopathological factors and prognosis of ESCC. The Kaplan-Meier survival curves showed that the high expression levels of 6 of the 72 miRNAs correlated with significantly lower patient survival rates. The overexpression of miR-129 was identified as a significant and independent prognostic factor (P = 0.031) in surgically treated ESCC patients. The hazard ratio for the prediction of early death was 18.11 for high versus low expression levels of miR-129. Similar results were obtained from an analysis performed on an additional 19 patients (test cohort) (P = 0.0057, for training cohort; P = 0.011, for test cohort; log-rank test). This experiment supports the notion that the high miR-129 expression levels, as observed in this study, might play a important role in the development of esophageal cancer.

Abstract. In this study, we examined the expression of esophageal cancer-related gene 4 (ECRG4) mRNA and evaluated its clinical significance in esophageal squamous cell carcinoma (ESCC). ECRG4 mRNA expression was quantified by real-time RT-PCR in 63 ESCC and corresponding normal esophageal mucosal samples. ECRG4 mRNA expression levels were significantly lower in ESCC tissues compared with corresponding normal esophageal mucosa (P<0.0001), in patients with locally invasive T2-4 tumors compared with less invasive T1 tumors (P=0.0229) and in stage 4 tumors compared with stage 0-3 tumors (P=0.0120). Furthermore, low ECRG4 mRNA expression levels were associated with significantly shorter survival after surgery compared with high ECRG4 mRNA expression levels (P=0.0150) in ESCC patients. On the basis of multivariate analysis, we conclude that ECRG4 mRNA expression level could be a candidate for an independent prognostic factor for ESCC patients.

Runt-related transcription factor 3 (RUNX3) has been reported to be a candidate tumor suppressor gene in gastric cancer. However, in esophageal cancer, the role of RUNX3 has not been studied. The expression of RUNX3 mRNA was quantified by real-time reverse transcription polymerase chain reaction using Taq Man PCR in 15 esophageal cancer cell lines (TE1-15) and 70 esophageal squamous cell carcinoma (ESCC) specimens and their paired normal esophageal mucosa. The data were analyzed with reference to clinicopathological factors. Using specific primers, methylation of the promoter region of RUNX3 was examined. RUNX3 mRNA expression in ESCC tissue was significantly lower than that in the corresponding normal esophageal mucosa (3.913±4.617 vs. 7.795±15.361, P=0.0345). RUNX3 mRNA expression levels in locally invasive T4 tumors were significantly lower than those in less invasive T1-3 tumors (P=0.0454). Patients who had low RUNX3 mRNA expression levels had a significantly shorter survival after surgery compared with patients who had high RUNX3 mRNA expression (P=0.0299). Among the 15 esophageal cancer cell lines studied, one had methylation of the promoter region of RUNX3. Only 4 in 70 ESCC tumors had methylation in this region. In conclusion, RUNX3 expression may be involved in the tumor invasion and poor prognosis of patients with ESCC. The methylation of the RUNX3 promoter region in esophageal cancer is rare. A study on the mechanisms that underlie the reduced expression of RUNX3 in ESCC is warranted.

Abstract. Esophageal squamous cell carcinoma (ESCC) is a common malignancy and one of the more difficult diseases to diagnose in Japan due to its poor prognosis. MicroRNAs are small non-coding RNAs of 21-23 nucleotides that regulate gene expression. MicroRNA-34b (miR-34b) has been reported to be overexpressed in various types of cancer. However, its role in ESCC has yet to be extensively studied. The present study investigated the expression of miR-34b in 88 ESCC patients. The miR-34b expression in ESCC was significantly higher than that in the corresponding normal esophageal mucosa. It was more highly expressed in tumors with more advanced stages. However, its expression did not correlate with the p53 status. Transfection of anti-miR-34b to the ESCC cells suppressed cell growth in vitro. These results suggest an oncogenic role of miR in ESCC.

Background. The prognosis of esophageal cancer patients is poor. Cisplatin (CDDP) is most often used for advanced esophageal cancer; however, the emergence of drug resistance has prevented successful treatment in many cases. Methods. Using microarray analysis, we identifi ed GP73 as a candidate gene that is overexpressed in TE4, an esophageal cancer cell line which is highly resistant to CDDP. We downregulated GP73 expression in TE4 using siRNA methods. To determine the effect of reduced GP73 expression on the proliferation of TE4, we used cytotoxicity assays. Results. Downregulation of GP73 expression using siRNA induced a signifi cant decrease in the IC 50 compared with cells treated with either control siRNA or mock transfection. Conclusions. GP73 is a candidate gene in esophageal cancer that may be the target of future molecular-targeted therapy in combination with CDDP.