Identification and molecular characterization of CALM/AF10 fusion productsin T cell acute lymphoblastic leukemia and acute myeloid leukemia

The t(10;11)(p12-p13;q14-q21) observed in a subset of patients with either acute lymphoblastic leukemia or acute myeloid leukemia has been shown to re sult in the fusion of AF10 on chromosome In with CALM(also named CLTH) on c hromosome 11. AF10 was originally identified as a fusion partner of MLL in the t(10;11)(p12-p13;q23) observed in myeloid leukemia. CALM is a newly iso lated gene, cloned as the fusion partner of AF10 in the monocytoid cell lin e, U937. In order to understand the relationship between MLL, AF10, CALM an d the leukemic process, fluorescence in site hybridization and reverse tran scriptase polymerase chain reaction were used to study a series of nine leu kemia patients with a t(10;11), Six had myeloid leukemia (AML-MO, AML-M1, A ML-M4 and AML-M5) and three had T cell lymphoblastic leukemia. We identifie d four different CALM/AF10 fusion products in five patients and AF10/CALM r eciprocal message in one. We conclude that fusion of CALM and AF10 is a rec urring abnormality in both lymphoid and myeloid leukemias of various types including AML-MB, and that the breakpoints in the two types of leukemia do not differ. Our data indicate that the CALM/AF10 fusion product on the der( 10) chromosome is critical to leukemogenesis.