Modulated expression of cell surface molecules and in vivo outgrowth of modified melanoma cells

Modulation of cell surface molecules involved in immune recognition and cellular interactions (class I major histocompatibility complex or MHC-I, B7.1 or CD80, integrin α4 or CD49d, tetraspanins CD9, CD81) was examined in modified B16 melanoma cells displaying either inhibited IGF-I expression or transfected OVA encoding gene. It was shown that inhibiting IGF-I expression or inserting OVA encoding gene did not lead to modification relevant to the presence of MHC-I or B7.1. However downregulation of tetraspanin CD9 was observed in modified IGF-I but not in OVA encoding gene inserted melanoma cells. Expression of tetraspanin CD81 and integrin α4/CD49d remained unchanged. Inoculated into syngeneic recipients, the modified melanoma cells exhibited significant delayed outgrowth with a reduction in the percentage of lethal tumors observed essentially in hosts injected with inhibited IGF-I expression cells.