Tumor-specific Gene Therapy for Renal Cell Carcinoma Using MN/CA9-directed Replication-competent Adenovirus

Abstract

Purpose: A new therapeutic approach is needed in patients with metastatic renal cell carcinoma (RCC) because of a dismal prognosis. MN/CA9 is a transmembrane glycoprotein that was first identified in the human cervical carcinoma cell line, HeLa. Since MN/CA9 protein is highly expressed in RCC tissues, but not in normal kidney, we constructed a tumor-specific replication-competent adenoviral vector utilizing MN/CA9 promoter (Ad-MN/CA9-E1a) and demonstrated its selective cytotoxicity toward MN/CA9-expressing RCC cells in vitro. Materials and Methods: MN/CA9-positive (HeLa, SK-RC-52) and MN/ CA9-negative (SK-RC-29) cells were used. RT-PCR assay for MN/CA9 mRNA was performed in each cells. Ad5 E1a protein production in each cells after infection with Ad-MN/CA9-E1a was determined by western blot analysis. In vitro cytotoxicity assay was performed for assessing the selective cytotoxicity of Ad-MN/CA9-E1a to MN/CA9-expressing cells. Results: RT-PCR assay showed that a distinct 255-bp fragment corresponding to the sequence within MN/CA9 cDNA was detected in HeLa and SK-RC-52 cells, but SK-RC-29 cells did not have MN/CA9 transcripts. Western blot analysis demonstrated that HeLa and SK-RC-52 cells showed much stronger Ad5 E1a protein expressions compared with SK-RC-29. In vitro cytotoxicity assay revealed that the growth of MN/CA9-positive cells was significantly inhibited with 0.1-1MOI of Ad-MN/CA9-E1a, but the growth of MN/CA9-negative cells (SK-RC-29) could only be inhibited by as many as 100MOI. Conclusions: These results suggest that a novel replication-competent adenoviral vector mediated by MN/CA9 promoter, Ad-MN/CA9-E1a, can selectively replicate in MN/CA9-expressing cancer cells with cytotoxic effects and may be utilized for the treatment of RCC.