Adenovirus-mediated Bak gene transfer induces apoptosis in mesothelioma cell lines

Objective: Conventional treatment for mesothelioma is largely ineffective. We therefore evaluated the novel approach of adenoviral gene transfer of the proapoptotic Bcl-2 family member Bak in mesothelioma cancer cell lines, which are sensitive and resistant to adenoviral p53. Methods: Binary adenoviral Bak (Ad/GT-Bak and Ad/GV16) and LacZ (Ad/GT-LacZ and Ad/GV16) vectors were used for transduction of the mesothelioma cell lines I-45 (p53 resistant) and REN (p53 sensitive). Protein levels were determined by Western blotting. Apoptosis was assessed by morphologic changes, caspase-3 cleavage, and fluorescence-activated cell sorter analysis of subdiploid populations. Cell viability was determined with the XTT assay. Statistical analysis was performed with analysis of variance and the Student t test. Results: High levels of Bak gene transfer were seen after coadministration of Ad/GT-Bak and Ad/GV16 in both mesothelioma cell lines. Apoptosis was induced 24 hours after Bak but not LacZ gene transfer ([Bak: I-45, 36%; REN, 25%] vs [LacZ: I-45, 1%; REN, 3%], P < .05]) in p53-sensitive (REN) and p53-resistant (1-45) cell lines. Cellular viability was significantly decreased 48 to 72 hours after Bak gene transfer compared with control vector in both cell lines (72 hours: Bak 1-45, 1.4% +/- 1.0%, and Bak REN, 4.7% +/- 1%, vs Lac-Z I-45, 83% +/- 3%, and Lac-Z REN, 100% +/- 1%; P < .05). Conclusions: Adenovirus-mediated overexpression of the Bak gene induces apoptosis and decreased cellular viability in p53-sensitive and p53-resistant mesothelioma cells. These data suggest that the gene transfer of proapoptotic Bcl-2 family members may represent a novel gene therapy strategy to treat mesothelioma.