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Neoplastic transformation and cytogenetic aberrations of rat tracheal epithelial cells induced by alpha-particle irradiation.

Primary rat tracheal epithelium (RTE) cells can be transformed in vitro by alpha-particles irradiation. One out of 3 isolated morphologically transformed colonies gave rise to an immortal cell line and ultimately became neoplastic by successive passaging. Cytogenetic analysis was performed on the cell line in order to understand how the specific chromosome alterations participate in the process of neoplastic transformation of RTE cells. The 5th, 18th, 39th passage cells and the colony cells isolated from soft agar (SA) culturing of the 40th passage cells were analyzed. The results showed that the 20th passage cells were nontumorigenic, but the 40th passage cells were tumorigenic. The increase of the length of the long arm of chromosome 15 (15q+) was frequent at the 5th passage (67.8%), especially in SA cells in which it occurred in a clonal fashion (100%). Therefore, 15q+ might be the critical gene lesion after alpha-particles irradiation. Monosomy of chromosome 8 that occurred frequently at passage 5 (54%) and 40 (53%) might be correlated with earlier transformation of RTE cells. In addition, three marker chromosomes (M1, M2 and M3) showed a passage-dependent increase. In particular M1 and M2 that were highly frequent at passage 39 (90%) suggested that they might play an important role in the process of cell transformation.