Flow cytometric analysis of DMBA-induced early in vivo ras expression.

According to recent publications 7,12-dimethylbenz[a]anthracene (DMBA) induces not only mammary cancer but also leukemia in Long-Evans (LE) rats. After treatment with DMBA, trisomy of the chromosome bearing N-ras and mutations in the codon 61 of different ras family genes are frequent. These alterations are already visible within 48 hours. Since there are very few data on ras genes' expression in the early stages of leukemogenesis, in our investigations LE rats were treated with DMBA and the expression of ras genes was measured within two days. DMBA was administered to outbred Long-Evans rats and the fluorescence intensity of the antibody recognizing the ras gene family was measured in femoral bone marrow cells 24 and 48 hours after the treatment. One of the bone marrow cell populations, separated by FSC and SSC, showed elevated ras gene expression at both 24 and 48 hours after the administration of the carcinogen. These results suggest that, besides the specific chromosomal aberrations and gene mutations, elevated ras gene expression could also be the marker of DMBA exposure.