POSTIRRADIATION DNA-SYNTHESIS INHIBITION AND G(2) PHASE DELAY IN RADIOSENSITIVE BODY CELLS FROM NON-HODGKINS-LYMPHOMA PATIENTS - AN INDICATION OF CELL-CYCLE DEFECTS

In the present study, both post-irradiation DNA synthesis and G(2) pha se accumulation were analyzed in lymphoblastoid cell lines (LCLs) and fibroblast cell strains derived from (Saudi) patients with non-Hodgkin 's lymphoma (NHL), ataxia telangiectasia (AT), AT heterozygotes and no rmal subjects. A comparison of the percent DNA synthesis inhibition (a ssayed by H-3-thymidine uptake 30 min after irradiation), and a 24 h p ost-irradiation G(2) phase accumulation determined by flow cytometry p laced the AT heterozygotes and the NHL patients in an intermediate pos ition between the normal subjects (with maximum DNA synthesis inhibiti on and minimum G(2) phase accumulation) and the AT homozygotes (with m inimum DNA synthesis inhibition and maximum G(2) accumulation). The si milarity between AT heterozygotes and the NHL patients with respect to the two parameters studied after irradiation was statistically signif icant. The data indicating a moderate abnormality in the control of ce ll cycle progression after irradiation in the LCLs and fibroblasts fro m NHL patients may explain the enhanced cellular and chromosomal radio sensitivity in these patients reported by us earlier. In addition to d emonstrating a link between cell cycle abnormality and radiosensitivit y as a possible basis for cancer susceptibility, particularly in the N HL patients, the present studies emphasized the usefulness of the assa y for 24 h post-irradiation G(2) phase accumulation developed by Lavin et al. (1992) in characterizing AT heterozygote-like cell cycle anoma ly in cancer patients irrespective of whether they carried the AT gene or any other affecting the cell cycle.