Accelerated tumor development in interferon-treated B6.C-Hyal-1 a mice.

The Hyal-1 locus, which we have previously described and mapped to mouse chromosome 9, influences the serum levels and molecular weight forms of hyaluronidase. We have also shown that the growth of two transplantable tumors, the 3LL carcinoma and the B16F10 melanoma, is influenced by the alleles at Hyal-1, in that the tumors develop more slowly in congenic B6.C-Hyal-1a (also called HW23) mice than in the parental Hyal-1b C57BL/6 mice. Here we present evidence that tumor development is stimulated and mortality is accelerated in B6.C-Hyal-1a mice grafted with 3LL carcinoma cells when treated with alpha/beta interferon (IFN-alpha/beta) or with IFN-beta, whereas in IFN-treated C57BL/6 mice 3LL tumor growth is inhibited. Likewise, in B6.C-Hyal-1a mice grafted with B16F10 melanoma cells, IFN-alpha/beta treatment results in stimulation of tumor growth, whereas in IFN-treated C57BL/6 mice tumor growth, whereas in IFN-treated C57BL/6 mice tumor growth is inhibited and mortality delayed. Thus, IFN-alpha/beta treatment of B6.C-Hyal-1a mice results in stimulation of tumor development and sometimes in accelerated mortality. This is the opposite of the usually described effect of IFN treatment in mice, which is inhibition of tumor development and delayed mortality, as was indeed observed in the C57BL/6 mice in the present experiments. These results provide the first indication that host genes can up- or down-regulate the antitumor activity of IFN and that, on some genetic backgrounds, IFN treatment enhances rather than inhibits tumor development. This may help to explain the apparent discordance between mouse model studies, which hitherto have consistently reported inhibition of tumor formation by IFN, and the clinical trials, in which only a limited percentage of individuals show tumor regression while others have no beneficial effect or even have progression of disease in spite of the IFN treatment.