A comparison of bleomycin-induced damage in lymphocytes and primary oral fibroblasts and keratinocytes in 30 subjects

The number of chromatid breaks in peripheral blood lymphocytes (PBL) after exposure to bleomycin in the S/G(2) phase of the cell cycle (in the literat ure referred to as 'mutagen sensitivity') is associated with an increased r isk of environmentally related cancers, including oral cancer. The aim of t his study was to elucidate whether mutagen sensitivity measured in lymphocy tes actually reflects chromosomal instability of normal cells in the areas in which tumors develop. Therefore, bleomycin-induced chromosomal damage in and growth inhibition of cultured oral fibroblasts and oral keratinocytes from 30 persons were compared with the standard mutagen sensitivity score i n PBL, A correlation was found for the percentage of aberrant metaphases be tween PBL and oral fibroblasts but not for the number of breaks per cell. T hese data do not allow a conclusion to be drawn on the use of fibroblasts t o study cancer risk. Within the fibroblasts it was found that a high number of breaks per cell was associated with less growth inhibition, indicative of damage-resistant growth. Oral keratinocytes were extremely sensitive to bleomycin, as indicated by a strong cell cycle block which resulted in a mi totic index too low to determine chromosomal breaks, Moreover, in the cell proliferation assay keratinocytes were found to be 100 times more sensitive as compared with fibroblasts, There was no correlation between bleomycin s ensitivity of keratinocytes compared with fibroblasts from a single patient as measured by growth inhibition. This may be due to the strong influence of alcohol consumption by the subjects, which was found to increase the sen sitivity of keratinocytes but not of PBL and fibroblasts. In conclusion, or al fibroblasts but not keratinocytes can be used to measure sensitivity for chromatid breaks. The apparent influence of environmental factors on kerat inocytes makes them a useful source to study exposure characteristics but l imits their application for the determination of genetic factors.