Expression of copper-transporting P-type adenosine triphosphatase in human esophageal carcinoma

A major obstacle in the treatment of esophageal carcinoma is the intrinsic/acquired resistance to cisplatin-based chemotherapy. Copper-transporting P-type adenosine triphosphatase (ATP7B) has been reported to be associated with cisplatin resistance in vitro. However, the clinical significance of this transporter has not previously been addressed. Our goal was to investigate if ATP7B is expressed in esophageal carcinoma and whether its expression correlates with reduced responsiveness to cisplatin treatment. We retrospectively examined the expression of ATP7B in primary esophageal carcinoma and its association with chemotherapeutic effect. Tissues were surgically removed from 17 esophageal carcinoma patients. Twelve of them received cisplatin-based chemotherapy before surgery. We performed immunohistochemical analysis of ATP7B using a monoclonal antibody against ATP7B in 17 esophageal carcinomas. A variable degree of cytoplasmic staining of tumor cells was observed in 76.5% (13/17 cases) of the analyzed carcinomas. ATP7B expression was not observed in adjacent non-neoplastic tissues. ATP7B positivity was not significant in gender, age, histopathological grading or TNM categories. Patients with ATP7B-positive tumors tended to have an inferior response to chemotherapy compared with the patients with ATP7B-negative tumors. These findings suggest that overexpression of ATP7B in esophageal carcinoma could be associated with unfavorable clinical outcome in patients treated with cisplatin-based chemotherapy. Therefore, ATP7B gene expression might be considered as a chemoresistance marker for cisplatin in the patients of esophageal carcinoma and provider of important information on the strategy against esophageal carcinoma.