Integrin antagonist augments the therapeutic effect of adenovirus-mediated REIC/Dkk-3 gene therapy for malignant glioma

Reduced expression in immortalized cells/Dickkopf-3 (REIC/Dkk-3) was identified as a gene whose expression is reduced in many human cancers. REIC/Dkk-3 expression is also downregulated in malignant glioma and regulates cell growth through caspase-dependent apoptosis. cRGD (EMD121974), an antagonist of integrins, has demonstrated preclinical efficacy against malignant glioma. In this study, we investigated the antiglioma effect of combination therapy using an adenovirus vector carrying REIC/Dkk-3 (Ad-REIC) and cRGD. Quantitative real-time reverse-transcription PCR revealed the reduction of REIC/Dkk-3 mRNA levels in malignant glioma cell lines. The reduction of REIC/Dkk-3 protein expression in malignant glioma cell lines was also confirmed with western blot analysis. After treatment with Ad-REIC and cRGD, the proliferative rate of malignant glioma cells was significantly reduced in a time-dependent manner. In vivo, there was a statistically significant increase in the survival of mice treated with Ad-REIC and cRGD combination therapy compared with Ad-REIC monotherapy. We identified an apoptotic effect following monotherapy with Ad-REIC. Moreover, cRGD augmented the antiglioma efficacy of Ad-REIC. These results may lead to a promising new approach for the treatment of malignant glioma.