Expression of IAP family proteins in esophageal cancer

Members of the inhibitor of apoptosis protein (IAP) family, including survivin, have been reported to be expressed in many tumors. However, their expression in esophageal cancer has not been clarified completely. We investigated the expression of mRNA for IAP family proteins in samples from esophageal cancers and their adjacent normal mucosa tissues by real-time quantitative RT-PCR. The survivin expression in esophageal cancer was significantly higher than that in normal mucosa (P < 0.05). Other IAP family proteins including cIAP1, cIAP2, NAIP and XIAP tended to show stronger expression in cancer tissue than normal mucosa, although the differences were not significant. As to the histological type of tumor, poorly differentiated squamous cell carcinomas exhibited significantly higher level of expression than well-differentiated carcinomas (P < 0.05). The proportion of apoptotic cells of cancer tissue inversely correlated with the intensity of survivin expression (P < 0.05). Immunohistochemical staining demonstrated cytoplasmic as well as nuclear expression of survivin in esophageal cancer, and further, in situ hybridization analysis demonstrated cytoplasmic expression of mRNA for survivin. The results suggest that the expression of IAP family proteins, especially survivin, may be associated with the biological character of esophageal cancer, such as apoptosis.