Midkine promoter can mediate transcriptional activation of a fused suicide gene in a broader range of human breast cancer compared with c-erbB-2 promoter.

We examined the expression level of the midkine (MK) and c-erbB-2 genes in both tumorous and matched nontumorous specimens from 18 patients with breast cancer. Expression of the MK and c-erbB-2 genes in nontumorous regions was relatively low, and the expression levels of both genes were not markedly different among the nontumorous samples. In contrast, the expression of the MK and c-erbB-2 genes in tumorous specimens was upregulated in 18 and 6 specimens, respectively. Regulatory regions of the MK gene were able to activate a reporter gene to a similar degree as those of the c-erbB-2 gene in the human breast cancer cell lines tested. Transfection of breast cancer cells with either the MK promoter- or the c-erbB-2 promoter-linked herpes simplex virus thymidine kinase gene increased their sensitivity to the prodrug ganciclovir. These data showed that the MK promoter activated a therapeutic gene in a wider range of human breast cancer than the c-erbB-2 promoter and suggest that MK promoter-mediated gene therapy is potentially more favorable in clinical settings.