Mineral fibre toxicity: expression of retinoblastoma (Rb) and phospho-retinoblastoma (pRb) protein in alveolar epithelial and mesothelial cell lines exposed to fluoro-edenite fibres.

Several asbestos-like mineral fibres, including fluoro-edenite, may cause lung cancer and/or other lung diseases. However, biological and molecular mechanisms linked to cancer development after mineral fibre exposure have not been fully investigated. In the present study, human non-malignant mesothelial (MeT-5A) and human bronchoalveolar alveolar epithelial (A549) cell lines were incubated with rising concentrations of fluoro-edenite to evaluate the expression of retinoblastoma (Rb) protein, which has been demonstrated to play an important role in cell cycle control and tumour progression. Intriguingly, these results show that Rb expression was unchanged, while the level of the phosphorylated protein increased significantly in a dose-dependent manner, suggesting an involvement of this regulator protein in the pathogenesis of the lung diseases induced by mineral fibres. In conclusion, fluoro-edenite regulates the expression of phospho-retinoblastoma to trigger a network of signals strictly connected with cell proliferation and neoplastic cell transformation.