Study of Transformation and Chromosomal Instability of Human Tracheal Epithelial Cells Induced by Formaldehyde

Objective: To determine the mechanisms of chemical carcinogenesis, the relationship between malignant transformation and genome /chromosomal instability of human bronchial epithelial cell, cell line - BEAS-2B cell exposed to formaldehyde was studied. Methods: The LC₅₀ value of formaldehyde to BEAS-2B cells was tested by MTT assay. Then the cells were induced with formaldehyde at the concentration of 20% LC₅₀; the characteristics of transformation of cells were identified though the characters of growth curve and colony formation rate of semi-solid agar. The metaphase modal chromosome numbers, karyotypes and nonrandom structural change of induced cell strains were analysed with the G-banding technique. Results: The growth curve of induced cells showed a trend of infinite proliferation and the anchorage independent growth was appeared in 15 generation cells. Before transformed, BEAS-2B cells had a pseudodiploid karyotype and were relatively stable genotypically. After transformed, three characteristic abnormal chromosomes were found. Most of the induced cells were triploid and/or tetraploid cells. The loss of one normal or two homologs of chromosome 14 also had a higher frequency. Furthermore, in their karyotypes, one or two unknown chromosomes appeared and trisomy-5 or trisomy-16 was observed. The induced cells also had a higher frequency of non-stabilizing aberration (39%), including chromosome loss, endoduplication, translocation, break, dicentromere and/or tricentromere etc. Conclusion: Formaldehyde could contribute to progression of transformation and result in genome instability.