The human pim-1 gene is not directly activated by the translocation (6;9) in acute nonlymphocytic leukemia.

In Acute Nonlymphocytic Leukemia (ANLL) specified by a reciprocal translocation (6;9), defined clinical and morphological features are observed. This suggests that genes located near the breakpoints of the translocation chromosomes are involved in the generation of this subtype of leukemia. The human pim-1 gene has been mapped near the t(6;9) breakpoint on chromosome 6. Using somatic cell hybrids we demonstrated that the pim-1 gene remains on chromosome 6. We investigated whether pim-1 plays a role in t(6;9) ANLL. The expression of pim-1 is elevated in two out of three patients with t(6;9) ANLL. However, the pim-1 gene has a size of only 6 kb and using field inversion gel electrophoresis, no chromosomal breakpoint can be detected within a distance of 165 kb from the pim-1 locus. Therefore it seems more likely that the elevated expression is due to the differentiation state of the cells rather than transcriptional activation by the translocation.