Abnormalities of the short arm of chromosome 12 in acute nonlymphocytic leukemia and dysmyelopoietic syndrome.

Abnormalities of the short arm of chromosome #12 (12p) were found in 18 patients, 7 with previously untreated acute nonlymphocytic leukemia (ANLL) and 11 with dysmyelopoietic syndromes (MDS) or ANLL following treatment for another malignant disease. The chromosome #12 abnormality was a partial deletion in 15 patients and a translocation in 3. The 12p- was the sole chromosomal abnormality in seven patients (four with de novo ANLL) and was associated with other chromosome abnormalities in eight patients. Thus, partial monosomy for 12p was often associated with other chromosomal changes and was a secondary abnormality in some cases. The consequences of this hemizygosity for genes located at 12p are discussed with references to the possible expression of a potentially mutated recessive gene. The study of c-K-ras 2, normally located at 12p, must be done in such cases, as the association of secondary blood disorders and multiple chromosome abnormalities suggests a possible mutation of this c-oncogene on chromosome #12.