2 FORMS OF HOX11, A T-CELL LEUKEMIA ONCOGENE, ARE EXPRESSED IN FETAL SPLEEN BUT NOT IN PRIMARY LYMPHOCYTES

HOX11 is identified from the breakpoint of human T cell acute lymphobl astic leukemias with t(10;14). Since overexpression of HOX11 in T cell s caused leukemias in transgenic mice, the endogenous HOX11 may play a role in proliferation and differentiation of T cells. In order to elu cidate the role, we examined the expression of Hox11 in normal lymphoc ytes by a reverse transcriptase-polymerase chain reaction analysis. Tw o alternatively spliced Hox11 mRNAs were expressed in fetal spleens. H owever, lymphocytes did not express Hox11 mRNA during differentiation. Furthermore, it was not induced in primary lymphocytes after activati on. These results suggest that ectopic expression of HOX11 in T cells is responsible for leukemogenesis.