The specific N-ras mutation in rat 7,12-dimethylbenz[a]anthracene (DMBA)-induced leukemia.
Intravenous injections of 7,12-dimethylbenz[a]anthracene (DMBA) induce erythroblastic leukemia (erythroleukemia) with #2 trisomy and Long #2 in Long-Evans rats. Recently, a consistent type of mutation, A to T transversion in codon 61 of N-ras gene, was found in all of 6 cultured leukemia cell lines and 13 primary leukemias induced by DMBA using polymerase chain reaction (PCR) and direct sequencing. On the contrary, no mutation was observed in Ha- and Ki-ras genes in these leukemias. The consistent occurrence of the above N-ras mutation in DMBA-induced leukemias indicates that N-ras gene plays an important role in DMBA-leukemogenesis. Mutations in ras genes generally takes place during the initiation stage of carcinogenesis because they often appear in the premalignant stage of tumors. In order to detect the N-ras mutation in an early stage of leukemogenesis, we designed the mutant-allele-specific amplification (MASA) method to detect the mutation in bone marrow (BM) cells of DMBA-treated rats. The MASA method was sensitive enough to detect one mutant cell mixed in 10(6) normal cells. Using this method, the N-ras mutation was found in BM cells 2 days after single DMBA injection and thereafter throughout the preleukemic stage. These results suggest that the N-ras mutation is an earliest event in DMBA-induced leukemogenesis.
Osaka
M
M
Department of Pathology and Tumor Biology, Graduate School of Medicine, Kyoto University, Japan.
Koh
T
T
Matsuo
S
S
Sugiyama
T
T
D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D003062:Codon; D005260:Female; D011905:Genes, ras; D007621:Karyotyping; D004915:Leukemia, Erythroblastic, Acute / Q000139:chemically induced / Q000235:genetics*; D007942:Leukemia, Experimental / Q000139:chemically induced / Q000235:genetics*; D008297:Male; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics; D051381:Rats; D014314:Trisomy
D003062:Codon; D015127:9,10-Dimethyl-1,2-benzanthracene; D016283:Proto-Oncogene Proteins p21(ras)