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SUMMARY. Radiotherapy plays a key role in the control of tumor growth in esophageal cancer patients. To identify the patients who will benefit most from radiation therapy, it is important to know the genes that are involved in the radiosensitivity of esophageal cancer cells. Hence, we examined the global gene expression in radiosensitive and radioresistant esophageal squamous cell carcinoma cell lines. Radiosensitivities of 13 esophageal cancer cell lines were measured. RNA was extracted from each esophageal cancer cell line and a normal esophageal epithelial cell line, and the global gene expression profiles were analyzed using a 34 594-spot oligonucleotide microarray. In the clonogenic assay, one cell line (TE-11) was identified to be highly sensitive to radiation, while the other cell lines were found to be relatively radioresistant. We identified 71 candidate genes that were differentially expressed in TE-11 by microarray analysis. The up-regulated genes included CABPR, FABP5, DSC2, GPX2, NME, CBR3, DOCK8, and ABCC5, while the down-regulated genes included RPA1, LDOC1, NDN, and SKP1A. Our investigation provided comprehensive information on genes related to radiosensitivity of esophageal cancer cells; this information can serve as a basis for further functional studies.

Cisplatin is the most common chemotherapeutic agent used in esophageal cancer. However, sensitivity to cisplatin varies greatly between patients. It is important to identify the gene(s) that are related to the sensitivity to cisplatin in esophageal cancer patients. The IC50 for cisplatin was measured for 15 esophageal cancer cell lines (TE1-5, TE8-15, KYSE140, and KYSE150). RNA was extracted from each of these cell lines and a normal esophageal epithelial cell line, namely, Het1A, and gene expression profiles were analyzed using an oligonucleotide microarray consisting of 34 594 genes. TE4 was highly resistant and TE12, 14, and 15 were sensitive to cisplatin. Thirty-seven genes were differentially expressed in the cisplatin-resistant esophageal cancer cell line. Our investigation provides a list of candidate genes that may be associated with resistance to cisplatin in esophageal cancer cells, which may serve as a basis for additional functional studies.

Caveolin-1 (CAV1) and caveolin-2 (CAV2) are the major structural proteins of caveolae. We investigated the relationship between the clinicopathological factors of esophageal squamous cell carcinoma (ESCC) and the expression of CAV1 and CAV2. CAV1 and CAV2 expression were analyzed by quantitative reverse transcription-polymerase chain reaction (RT-PCR) in 15 esophageal cancer cell lines (TE1-15) and a normal esophageal epithelium cell line (Het-1A). CAV1 and CAV2 expression was examined by RT-PCR and immunohistochemical analysis in 47 ESCC specimens. High levels of CAV1 and CAV2 mRNA were detected in TE1-15, but neither CAV1 nor CAV2 mRNA were detected in Het-1A. In the ESCC samples CAV1 and CAV2 mRNA expression in the ESCC samples were significantly higher than in the corresponding normal esophageal mucosa (CAV1, P=0.0024; CAV2, P=0.0136). However, we could not find any significant relationship between CAV1 or CAV2 mRNA expression and clinicopathological factors. Immunostaining for CAV1 was positive in 13 of 47 patients (27.7%), whereas CAV2 was positive in 22 of 47 patients (46.8%). A significant correlation was observed between CAV1 and CAV2 immunostaining and T factor, lymphatic invasion, vein invasion and differentiation. The patients with positive staining for CAV1 or CAV2 had a significantly shorter survival than those with negative staining (P=0.0105 and 0.0424 for CAV1 and CAV2, respectively). These results suggest that positive staining for CAV1 and CAV2 could be a potentially useful prognostic marker of ESCC.

Esophageal squamous cell carcinoma (ESCC) is one of the most common and deadly cancers in Japan. In this study we performed fluorescent in situ hybridization (FISH) and loss of heterozygosity (LOH) analysis for chromosome 18q in ESCC cells to investigate allelic imbalance of chromosome 18q in ESCC. In the FISH analysis, only one signal for chromosome 18q was detected in TE-1 esophageal cancer cells, whereas two signals were detected in TE-2 cells. Two of five resected ESCC samples from patients showed loss of one copy of chromosome 18q. To construct a precise deletion map of chromosome 18q, LOH analysis was performed using 30 microsatellite markers localized to chromosome 18q. LOH was observed in 31 of 46 ESCC samples (67.4%) for at least one locus on chromosome 18q. LOH frequency for individual markers varied from 18.5% (D18S460) to 48.4% (D18S866). Thirteen of 46 ESCC samples (28.3%) showed the loss of most of the long arm of chromosome 18. Lymph node metastasis and vein invasion were significantly associated with the deletion of chromosome 18q. Loss of chromosome 18q may play an important role in the progression of ESCC.