Persistence of chromosomal alterations affecting the 1cen-q12 region in a human lymphoblastoid cell line exposed to diepoxybutane and mitomycin C

Multicolor fluorescence in situ hybridization (FISH) with tandem-labeling p robes for the 1cen-q12 region is a potential biomarker for the detection of structural chromosomal aberrations (CAs) in human cells. To determine the suitability of this technique for biomonitoring humans exposed to 1,3-butad iene (BD) and to characterize the alterations induced as well as their stab ility over time, the human lymphoblastoid cell line AZH-1 was treated with 5 mu M diepoxybutane (DEB) or the positive control mitomycin C (MMC; 0.1 mu M) for 24 h. Following the removal of the test chemicals, cell cultures we re grown for an additional 19 days in the absence of the test compound, Usi ng the tandem FISH technique, aliquots from the main cultures were examined for the induction of CAs affecting the 1cen-q12 region at various interval s. A significant increase in chromosomal breakage/exchanges affecting the 1 cen-q12 region was seen in both the DEB- and MMC-treated interphase and met aphase cells. The damage peaked at approximately 48 h following the additio n of the test compound and declined with time. However, at day 20, the freq uency of aberrant cells was still significantly higher than the control lev els. For comparison, the frequency of micronuclei (MN) formed and their ori gin was determined using the cytochalasin B-modified MN assay and FISH with a pancentromeric probe. Showing a similar pattern, the frequency of centro nere-negative MN peaked at 48 h, but however was not significantly elevated above control levels at 20 days. At early time points, aberrations detecte d using the FISH assay consisted of nearly equal proportions of unstable- a nd stable-type aberrations, while at the later rime points, translocations were the predominant aberration type. In addition, the use of tandem-label FISH in combination with BrdU-immunfluorescence staining, showed that almos t identical frequencies of structural aberrations could be seen in actively replicating and non-replicating cell populations. These studies indicate t hat a small but significant proportion of the alterations detected using th is FISH technique persists over time and that this technique may be valuabl e for biomonitoring chromosomal alterations in ED-exposed populations. (C) 1999 Elsevier Science B.V. All rights reserved.