Fas-associating death domain protein overexpression induces apoptosis in lung cancer cells

Objectives: Non-small cell lung cancers commonly develop resistance to radiation and chemotherapy, and they often present at stages beyond surgical resectability. Because current treatment modalities are inadequate, novel therapies are necessary to reduce the effects of the increasing incidence in pulmonary neoplasms. Fas-associating death domain protein is a central mediator of death receptor-initiated apoptosis that directly activates the caspase-8 protease. We hypothesized that overexpression of Fas-associating death domain protein would effectively eradicate lung cancer cells by induction of apoptosis. Methods: Cultured A549 alveolar carcinoma and NCI-H226 squamous carcinoma cells were exposed to increasing multiplicities of infection of a replication-deficient, adenoviral vector that expresses the wild-type murine Fas-associating death domain protein gene or control virus for 4 hours. Twenty-four hours later, cells were assessed for viability by crystal violet staining and caspase activation by microscopic analysis. Protein lysates were examined by Western blotting for expression of Fas-associating death domain protein and activated caspase-8. Results: Adenoviral infection with the wild-type murine Fas-associating death domain protein gene in A549 cells resulted in a dose-dependent expression of Fas-associating death domain protein and the appearance of cleaved, activated caspase-8. Increasing multiplicities of infection of the wild-type murine Fas-associating death domain protein gene, but not control adenovirus, was associated with increased cell death in A549 and NCI-H226 cells. The wild-type murine Fas-associating death domain protein gene infection of A549 cells at multiplicities of infection of 50 induced at least 10-fold increase in Fas-associating death domain protein levels and decreased viability by > 50% (n = 3; P < .001). Conclusion: Overexpression of Fas-associating death domain protein induced dose-dependent cell death in A549 and NCI-H226 lung epithelial cancer cells. Expression of Fas-associating death domain protein results in activation of caspases, a hallmark of apoptosis. Delivery of the wild-type murine Fas-associating death domain protein gene to drug- and radiation-resistant lung cancer may be a novel method for therapy of non-small cell lung cancer.