[Increase of BIRC5 gene expression in non-small cell lung cancer and esophageal squamous cell carcinoma does not correlate with expression of genes SMAC/DIABLO and PML encoding its inhibitors].

Survivin (BIRC5) is one of the members of IAP-family apoptosis inhibitors. The BIRCS gene is expressed in most human embryonic tissues and malignant tumors but not in normal differentiated tissues of adult human. It was suggested that BIRC5 proteins inhibit apoptosis and play an essential role in tumorigenesis, makings surviving an attractive target for anticancer therapy. The mechanisms regulating level of survivin are not completely understood. It was supposed that natural inhibitors of survivin, namely SMAC and PML, play an important role in these processes. Using RT-PCR and immunoblotting we analyzed the transcription level of BIRC5, SMAC and PML genes and content of corresponding proteins in normal and tumor human tissues in non-small cell lung cancer and esophageal squamous cell carcinoma. It was demonstrated that BIRC5 is transcribed only in tumor tissues, whereas expression levels of SMAC and PML are the same in normal and tumor tissues. The contents of proteins correspond to levels of mRNA of the respective genes. Thus the increase of level of survivin in tumor tissues is not the result of decrease in content of its inhibitors SMAC and PML, as their content in tumor and normal cells is the same.