Variation in Sp1 binding sites correlates with expression of survivin in breast cancer

Survivin is the smallest member of the inhibitor of apoptosis (IAP) family and is deregulated in breast cancer, where it is associated with a poor overall prognosis. It is well established that survivin overexpression predominately occurs at the transcriptional level. Numerous transcription factors bind to specific sequences in the promoter regions of genes and are involved in transcriptional regulation. Specificity protein (Sp) 1 binding sites have been found in the promoter region of the survivin gene. The present study aimed to investigate whether variations in Sp1 binding sites affect survivin expression. Nested polymerase chain reaction followed by DNA sequencing were performed to analyze the survivin gene promoter region in 42 breast cancer tissue samples. Furthermore, survivin expression was assessed using immunohistochemistry. High survivin protein expression was found in 66.7% (28/42) of breast cancer tissue samples. In addition, 15 variations in seven Sp1 binding sites were detected in 12 samples and Sp1 binding site variation was found to be associated with low survivin expression in the 42 samples. These findings suggested that variations in Sp1 binding sites may be associated with survivin expression.