Gamma interferon directly inhibits the growth of neurofibroma cells in vitro.

Various neurofibroma cell lines isolated from either dermal, plexiform, or diffuse neurofibromas were found to respond to human gamma interferon by decreasing proliferation rates in vitro. The cell number decreased to around 40-50% of controls (without gamma interferon) six days after the treatment. The cell lines showed dramatic inhibition of tritium-labeled thymidine uptake one day after the treatment with gamma interferon. Either 100 IU/ml or 1,000 IU/ml of gamma interferon resulted in the same range of inhibition. It is calculated that venous infusion of one vial of commercial recombinant gamma interferon (200 x 10(6) IU/ml) reaches more than 100 IU/ml in the peripheral blood, which means that it may be clinically useful. The cell lines also responded to gamma interferon by initiating expression of CD54. Immunological modulation of neurofibroma cell components by gamma interferon in vivo remains to be studied.