Type I consensus interferon (CIFN) gene transfer into human melanoma cells up-regulates p53 and enhances cisplatin-induced apoptosis: implications for new therapeutic strategies with IFN-alpha.

In this study, we describe the effects produced by the retroviral transduction of human type I consensus IFN (CIFN) coding sequence into the 8863 and 1B6 human melanoma cell lines, derived from a metastatic and a primary human melanoma, respectively. Melanoma cell lines producing approximately 103 IU/ml of IFN were obtained. Interestingly, cisplatin treatment of IFN-producing 8863 and 1B6 melanoma cells resulted in a three- to four-fold increase in the percentage of apoptotic cells with respect to similarly treated parental or control-transduced cell cultures. A similar effect, although less intense, was caused by cultivation of parental melanoma cells in the presence of exogenous CIFN. The increased susceptibility of the IFN-producing melanoma cell lines to cisplatin-induced apoptosis was associated with an IFN-dependent accumulation of p53, which also correlated with a decrease in Bcl-2 expression. Addition of exogenous CIFN to parental melanoma cells resulted in similar although weaker modulations of p53 and Bcl-2 expression. Cisplatin administration to nude mice bearing 3-day-old IFN-producing 8863 tumors resulted in complete tumor regression, while only a partial tumor inhibition was observed upon cisplatin treatment of mice bearing parental or control-transduced 8863 tumors. Starting the cisplatin treatment 7 days after tumor cell injection still resulted in a stronger inhibition of tumor growth in the mice bearing IFN-producing 8863 tumors as compared with parental tumor-bearing mice. A comparable therapeutic effect was obtained after repeated peritumoral administration of 103 IU of exogenous CIFN and cisplatin treatment. Interestingly, a spontaneous tumor regression was observed in nude mice injected with IFN-producing 1B6 cells, in contrast to the progressive tumor growth occurring in mice receiving a similar inoculum of the parental or control-transduced 1B6 melanoma cells. Repeated peritumoral administration of 103 IU of exogenous CIFN to mice bearing parental 1B6 tumors caused only a transient inhibition of tumor growth. These results indicate that type I IFN gene transfer is an effective approach for suppressing the tumorigenic phenotype of human melanoma cells and for increasing the efficacy of anticancer drugs. These observations, together with our previous findings showing the importance of IFN-alpha-T cell interactions in the generation of an antitumor response in mouse models, underline the interest of using type I IFN in gene therapy strategies for the treatment of human melanoma.