INCREASED LEVELS OF A CHROMOSOME 21-ENCODED TUMOR INVASION AND METASTASIS FACTOR (TIAM1) MESSENGER-RNA IN BONE-MARROW OF DOWN-SYNDROME CHILDREN DURING THE ACUTE-PHASE OF AML(M7)

Children with Down syndrome (DS) have a 10-20-fold increased risk of a cute lymphocytic leukemia (ALL) and acute myeloid leukemia (AML), comp ared to non-DS children. The myeloid leukemia that accounts for nearly 50% of DS leukemias is usually the otherwise uncommon megakaryoblasti c type (AML-M7). Though an etiological role of trisomy 21 in leukemoge nesis has been suggested, the expression of genes on chromosome 21 in relation to trisomy, DS, and specific DS phenotypes such as leukemia i s poorly understood. We used a heterologous-mimic competitive RT-PCR t echnique to measure the mRNA levels of a chromosome 21 tumour invasion and metastasis factor (TIAMI) directly in bone marrow samples of DS l eukemic patients. In the limited number of cases analysed so far, we f ound TIAMI mRNA levels in the DS AML-M7 samples of bone marrow taken i n the acute phase of the disease (presentation or relapse, n = 8) to b e highly significantly raised, nearly threefold, compared to that meas ured in the remission samples or normal individuals (normals + remissi ons, n = 10). (C) 1998 Wiley-Liss, Inc.