AbstractEpidemiological studies have shown that inhalation of radon is associated with an increased risk for lung cancer among underground miners. The cellular and molecular mechanisms for radon‐induced carcinogenesis are not clear. By using a human papillomavirus‐immortalized human bronchial epithelial cell line, we show here that a single 30 cGy dose of these high‐energy particles induced tumorigenic conversion of the cells 3–4 months postirradiation at frequencies estimated to be ∼4 × 10−7. Transformed cells arise through a series of sequential steps, including altered growth kinetics, loss of response to serum‐induced terminal differentiation, anchorage‐independent growth, and rumorigenesis, with each preceding stage representing a necessary yet insufficient step toward the later, more malignant phase. Northern and Western blot analyses showed overexpression of the G1 cell‐cycle‐control kinase, cyclin D1. Analysis of genomic DNA from the tumorigenic cell lines using polymerase chain reaction amplification and restriction enzyme analysis demonstrated no mutation in the K‐rasoncogene, which has frequently been found to be mutated in human lung cancers. Western blot analysis showed that both control BEP2D cells and their tumorigenic variants contained phosphorylated Rb proteins. This model provides an opportunity to study the cellular and molecular changes at the various stages in radiation carcinogenesis involving human cells.
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