The TSLC1 tumor-suppressor gene is silenced in a number of human cancer tissues and cell lines, including lung, prostate, liver, stomach, pancreatic, and breast cancers. Expression of TSLC1 in a non-small-cell lung cancer (NSCLC) cell line A549 suppresses tumorigenicity in nude mice. However, the molecular mechanism of TSLC1 action is not yet elucidated. In the present study, we show that the expression of TSLC1 from a recombinant adenovirus vector (Ad-TSLC1) inhibited cell proliferation and induced apoptosis in the NSCLC cell line A549. We also demonstrated that subcutaneous tumor growth in nude mice induced by A549 cells was suppressed to the extent of 70-80% by intratumoral injection of Ad-TSLC1. Re-expression of TSLC1 also resulted in activation of the apoptotic protease caspase-3, accompanied by the cleavage of its substrate poly (ADP-ribose) polymerase (PARP). The antiproliferative and pro-apoptotic activity of TSLC1 required the presence of the FERM-binding and PDZ-interacting motifs located in the cytoplasmic domain. Our results demonstrate the pro-apoptotic and oncosuppressive activity of TSLC1 protein, and suggest the potential of TSLC1 for gene therapy.
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