SELECTIVE HYPEREXPRESSION OF C-JUN ONCOPROTEIN BY GLASS FIBER-TRANSFORMED AND SILICA-TRANSFORMED BALB C-3T3 CELLS/

Mining and mineral processing are important industries in the United S tates. A large number of workers are potentially exposed to silica dur ing mining and to glass fibers during manufacturing. There is a concer n regarding lung cancer risk among workers exposed to silica and glass fibers. Our previous studies showed that both glass fibers and silica induced transformation of BALB/c-3T3 cells, In order to explore the r elationship between silica and glass fiber-induced cell transformation and oncoprotein expression, the protein products of seven proto-oncog enes (c-K-ras, c-H-ras, c-sis, c-myc, c-myb, c-erb B1 and c-jun) and o ne tumor suppressor gene (p53) were examined in BALB/c-3T3 cells trans formed by glass fibers or silica using immunoblotting with specific mo noclonal or polyclonal antibodies. The results showed that all transfo rmants,including eight induced by glass fibers and eight by silica (Mi n-U-Sil 5), were positive for c-jun protein expression; the level of c -jun protein was elevated 8-21-fold in these transformants. Other prot ooncogene proteins in transformed cells were either not detectable or not different from non-transformed cells. These results suggest that t he overexpression of c-jun is common in BALB/c-3T3 transformed cells i nduced by glass fibers or silica. It seems, therefore, that the expres sion of c-jun may play an important role in the transformation process . (C) 1997 Elsevier Science Ireland Ltd.