Treatment with IFN-α-2b and IFN-β-1a also resulted in decreased proliferation index of human melanoma xenograft tumors as manifest by immunohistochemical staining with Ki-67; again, IFN-β-1a-treated tumors showed less staining with Ki-67 than did IFN-α-2b-treated tumors [37]. This evidence concerns the gene MKI67 and melanoma.