Ki-ras-2 in acute lymphoblastic leukemia cells with chromosome change at 12p12

Cytogenetic and molecular investigations were performed on a pre-B-lymphoblastic acute leukemic cell line (NALM-6). The NALM-6 cells contained a del(5)(q32) and an ins(12)(p12;?), chromosomal material of unknown origin being inserted between subbands 12p12.1 and 12p12.2. Chromosomal in situ hybridization using a 3.0-kb c-Ki-ras-2 probe showed a significant accumulation of grains on the proximal portion of the inserted chromosomal material (12p12.1), as well as on the normal chromosome #12 with a peak at 12p11p12. The signal intensity obtained after hybridization of the c-Ki-ras-2 specific probe to the NALM-6 cells DNA is comparable with the intensity of the signal after hybridization of the same probe with the control cell line (MC/B) DNA. The findings indicate that the c-Ki-ras-2 gene is neither amplified nor transposed in the NALM-6 cells.