Detection of hypermethylation of the c-abl genomic locus in the spleen of juvenile LE rats.

Tumor induction by treatment with polycylic hydrocarbons depends on age and the strains of rats used. Juvenile LE rats are very sensitive to the induction of leukemia and chromosomal breaks by intravenous DMBA injection. We have previously demonstrated a chromosomal translocation in chromosome 3 and 12 in a DMBA induced LE rat leukemia cell K3D. In our present communication we have examined the c-abl expression in the leukemic cell line as well as in the LE rats at different ages. We found that in the leukemic cell K3D the c-abl expression is elevated both at the level of mRNA and protein. In the preleukemic stage, highly elevated expression of c-abl mRNA was detected exclusively in the spleen of the juvenile LE rats. Furthermore this high expression of the c-abl gene correlates well with hypermethylation of possible cytosine residue in the c-abl genomic locus.