The effects of transferring tumor suppressor gene p16INK4A to p16INK4A-deleted cancer cells*

OBJECTIVES p16 is known to be an important tumor suppressor gene and is also called MTS1 (multiple tumor suppressive gene 1). Especially in the case of non-small cell lung cancer, it was not expressed in more than 70% of cell lines examined. To determine changes in cell-cycle related proteins and the tumorigenic effect, we, therefore, transfected p16INK4A gene into lung cancer cell lines. METHODS We transfected p16INK4A gene into lung cancer cell lines which do not express p16 protein. We evaluated the effect by clonogenic assay and observed the changes of cell-cycle related proteins. RESULTS The newly-expressed p16 formed a complex with cdk4, and phosphorylated pRB was decreased, although cyclin D1 and pRB:cyclin D1 complex were unchanged. Clonogenic assay after selection with G418 showed that, in the cell lines transfected with p16, tumorigenicity was significantly less than in the control. CONCLUSION These results suggest that the p16INK4A gene can be a candidate for gene therapy in cases of NSCLC in which p16INK4A gene is inactivated.