ANTISENSE OLIGODEOXYRIBONUCLEOTIDE AGAINST THE MLL-LTG19 CHIMERIC TRANSCRIPT INHIBITS CELL-GROWTH AND INDUCES APOPTOSIS IN CELLS OF AN INFANTILE LEUKEMIA-CELL LINE CARRYING THE T(11-19) CHROMOSOMAL TRANSLOCATION

To clarify the role of the multiple lineage leukemia gene-leukemia tra nslocation gene of chromosome 19 (MLL-LTG19) protein in leukemogenesis , we synthesized antisense oligodeoxyribonucleotide (ODN) against the fused region of the MLL-LTG19 chimeric transcript and treated KOCL33 c ells carrying the t(11;19) translocation with antisense ODN, The antis ense ODN inhibited cell growth and induced apoptosis in KOCL33 cells b ut not in Daudi cells, which have no t(11;19). The levels of MLL-LTG19 mRNA and MLL-LTG19 protein in KOCL33 cells treated with antisense ODN were shown to decrease with time by reverse transcription-PCR and Wes tern blot analysis. These results suggest that the MLL-LTG19 fusion pr otein contributes to cell proliferation and malignant transformation i n infantile acute leukemia cells carrying the t(11;19) translocation.