Localization of c-Ha-ras-1 oncogene in the t(7p-;11p+) abnormality of two cases with myeloid leukemia.

A reciprocal translocation involving the short arms of chromosomes #7 and #11, t(7;11)(p15;p15), was found in two patients with myeloid leukemia, one with acute myelogenous leukemia (AML-M2) and the other with Philadelphia chromosome-positive chronic myelocytic leukemia (CML) in blastic phase. In both cases, a minor fraction of leukemic blasts in the bone marrow had Auer rods in the cytoplasm. In situ chromosome hybridization showed that the c-Ha-ras-1 oncogene localized to the breakpoint (p15) of chromosome #11 is translocated to the rearranged chromosome #7 in the AML case, whereas, it remained on the conserved region of the rearranged chromosome #11 in the CML case. The significance of the t(7;11) abnormality in myeloid leukemia is discussed.