Activation of cancer-specific gene expression by the survivin promoter

Survivin, a member of the IAP (inhibitor of apoptosis) gene family, appears to be overexpressed in common cancers but not in corresponding normal adult tissues. To investigate whether the survivin promoter controls cancer cell-specific gene expression, we determined whether the survivin gene promoter could regulate reporter gene expression in cancer cell lines and xenografts.

Survivin protein levels were determined in human and murine cancer cell lines and in normal tissues of adult C57BL/6 mice by Western blot analysis. A reporter construct in which a portion of the survivin gene promoter was used to drive transcription of a human secreted alkaline phosphatase (SEAP) gene was transiently transfected into cancer cells, and promoter activity was extrapolated from SEAP activity. A2780 human ovarian cancer cells were transfected with this construct, and stable transfectants were injected into the intrabursal ovarian space of immunodeficient mice. Tumor growth was monitored, and plasma SEAP levels were used as a measure of survivin promoter activity in vivo.

Survivin protein was detected in all cancer cell lines examined but not in most normal adult mouse tissues. After transfection, the survivin promoter was more active in all cancer cell lines than in normal ovarian surface epithelial cells or mouse 3T3 cells. After 0.8 x 10(6) stable transfectant cells were injected into the intrabursal cavity of mouse ovaries, plasma SEAP activity was detected within 24 hours, and the activity increased with time and tumor growth.

Transfection experiments indicate that survivin protein expression in cancer tissue appears to be regulated, at least in part, transcriptionally. Thus, the survivin promoter may be useful in controlling gene expression in cancer cells.