Design and characterization of a specific SPARC promoter

VIALE, DL; LOPEZ, MV; CAFFERATA, EG; CHERNAJOVSKY; Y; GOULD, D; PODHAJCER, OL

Rosario Argentina

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.; 2006

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.

The successful use of transcriptional targeting for cancer therapy depends on the activity of a given promoter inside the malignant cell. We hypothesized that targeting the entire tumor mass might have better therapeutic effect than only tumor cells. SPARC is a matricellular protein overexpressed in human malignant melanomas both in the malignant cells compartment as in the stromal one (fibroblasts and endothelial cells). For this purpose, we assessed the activity of different SPARC promoter fragments that were isolated considering specific motives such as two GGA boxes, the presence of a TATA-like box and potential transcription initiation sites. We also investigated SPARC promoter sequence and found a putative downstream promoter element (DPE) sequence included in the first exon of the promoter. We assessed the strength and specificity of different SPARC promoter fragments by luciferase assay. A fragment of 548 base pairs (including –513/+35) gives the best ratio between SPARC expressing and SPARC non-expresing cells. In addition, we have demonstrated that both, TATA and DPE elements, are involved in transcriptional initiation. Different genes involved in tumor progression are regulated by steroid hormones. We evaluate the effects of dexamethasone on SPARC promoter and demonstrated that it reduces promoter activity.