Combined p19Arf and interferon-beta gene transfer enhances cell death of B16 melanoma in vitro and in vivo.

Approximately 90% of melanomas retain wild-type p53, a characteristic that may help shape the development of novel treatment strategies. Here, we employed an adenoviral vector where transgene expression is controlled by p53 to deliver the p19 alternate reading frame (Arf) and interferon-β (IFNβ) complementary DNAs in the B16 mouse model of melanoma. In vitro, cell death was enhanced by combined gene transfer (63.82±15.30% sub-G0 cells); yet introduction of a single gene resulted in significantly fewer hypoploid cells (37.73±7.3% or 36.96±11.58%, p19Arf or IFNβ, respectively, P<0.05). Annexin V staining and caspase-3 cleavage indicate a cell death mechanism consistent with apoptosis. Using reverse transcriptase quantitative PCR, we show that key transcriptional targets of p53 were upregulated in the presence of p19Arf, although treatment with IFNβ did not alter expression of the genes studied. In situ gene therapy revealed significant inhibition of subcutaneous tumors by IFNβ (571±25 mm3) or the combination of p19Arf and IFNβ (489±124 mm3) as compared with the LacZ control (1875±33 mm3, P<0.001), whereas p19Arf yielded an intermediate result (1053±169 mm3, P<0.01 vs control). However, only the combination was associated with increased cell death and prolonged survival (P<0.01). As shown here, the combined transfer of p19Arf and IFNβ using p53-responsive vectors enhanced cell death both in vitro and in vivo.