Adenovirus lacking the 19-kDa and 55-kDa E1B genes exerts a marked cytotoxic effect in human malignant cells

The adenovirus (Ad) E1A gene exerts an antitumor effect and can induce sens itivity to treatment With DNA-damaging agents. In contrast, the Ad 19-kDa E 1B protein inhibits E1A-mediated apoptosis and the 55-kDa E1B inactivates t he p53 protein. In this paper, we study the in vitro and in vivo effects of a 19-kDa and 55-kDa E1B-defective Ad in several malignant human tumor cell lines. Materials and Methods. Nontumorigenic human fibroblasts (CCD-45SK and Hs67) , peripheral blood lymphocytes, and several human tumor cell lines derived from cervix, colon, and breast carcinomas, epidermoid carcinoma, and osteos arcoma (HeLa, HT29, MCF7, Saos-2, and A431 cell lines) were studied. Wild-t ype (wt) Ad type 5 and H5 dL118 Ad, a mutant with the deleted E1B region, w ere employed. The cells were infected at 20 plaque-forming units, and cell viability was evaluated by the crystal violet method. In the in vivo experi ments, 2 x 10(6) cells from the carcinoma cell lines HeLa, A431, and HT29 w ere injected into nude mice. The tumorigenicity of previously infected cell s and after an intratumoral injection of Ad was analyzed. The mice received whole-body gamma-irradiation. Results. The H5 dL118 mutant produced a marked cytopathic effect in all of the malignant cells, surpassing that of the wt Ad; viability at 72 hours ra nged from 11% to 20% for H5 dL118 Ad and from 70% to 93% for the wt Ad With respect to uninfected controls. In the in vivo experiments, a total inhibi tion of tumorigenicity was detected when cells were infected prior to injec tion and a partial and transitory decrease in tumorigenicity was detected w hen the mutant H5 dL118 was injected intratumorally. gamma-irradiation enha nced the in vivo antitumor effects. Conclusions, These results indicate that infection with completely E1B-defi cient Ads induced a marked cytopathic effect on malignant cells that was hi gher than that seen for wt Ads; in addition, infection with such Ads exerts a tumor suppressor effect in vivo.