Mutations in the retinoblastoma-related gene RB2/p130 in lung tumors and suppression of tumor growth in vivo by retrovirus-mediated gene transfer

The retinoblastoma (Rb) family consists of the tumor suppressor pRh/p105 an d related proteins p107 and pRb2/p130, Recent immunohistochemical studies o f the retinoblastoma family of proteins in 235 specimens of lung cancer sho w the tightest inverse association between the histological grading in the most aggressive tumor types and pRb2/p130. This led us to study a panel of human lung cancers for mutations in the RB2/p130 gene. Mutations in the Rb- related gene RB2/p130 were detected in 11 of 14 (78.5%) primary lung tumors by single-strand conformation polymorphism and sequence analysis, A Molone y leukemia virus-based retroviral system was set up, and a comparable viral concentration of 1 x 10(7) infectious units/ml was obtained. Retrovirus-me diated delivery of wild-type RB2/p130 to the lung tumor cell line H23 poten tly inhibited tumorigenesis in vitro and in vitro, as shown by the dramatic growth arrest observed in a colony assay and the suppression of anchorage- independent growth potential and tumor formation in nude mice. The tumors t ransduced with the RB2/p130 retrovirus diminished in size after a single in jection, and a 12-fold reduction in tumor growth after RB2/p130 transductio n compared with the Pac-transduced tumors (92% reduction, P = 0.003) and la cZ-transduced tumors (93% reduction, P < 0.001) was found to be statistical ly significant, These findings provide the missing confirmation that RB2/p1 30 is a "bona fide" tumor suppressor gene and strengthen the hypothesis tha t it may be a candidate for cancer gene therapy for lung cancer.