Characterization of a specific SPARC promoter suitable for Cancer Gene Therapy

VIALE, D.L; LOPEZ, M.V; CAFFERATA, E.G; GOULD, D; CHERNAJOVSKY; Y; PODHAJCER, O.L

Rosario

Congreso; SAIB; 2006

The success of transcriptional targeting in cancer gene therapy depends on the activity of a particular promoter inside the malignant cell. We hypothesized that targeting the entire tumor mass (malignant and stromal cells) might provide better therapeutic effect than conventional tumor cells directed strategies. SPARC is a matricellular protein overexpressed in human malignant melanomas both in tumour and stromal cells (fibroblasts and endothelial cells). For this purpose, we cloned different SPARC promoter fragments that were isolated considering specific motifs such as two GGA boxes, the presence of a TATA-like box and potential transcription initiation sites and a putative downstream promoter element (DPE) that we discovered in the first exon. We tested the strength and specificity of different SPARC promoter fragments by luciferase assay. A fragment of 548 bp (including ?513/+35) presents the best ratio, determined as the activity produced between SPARC expressing and SPARC non-expressing cells. Finally, by different mutations we have demonstrated that both elements, TATA and DPE, are involved in transcriptional initiation. In addition, we also demonstrated that dexamethasone reduces SPARC promoter activity. Taken together, our data suggest that our SPARC promoter is a good candidate for transcriptional targeting in cancer gene therapy.