Expression of the ETS2 and transferrin receptor genes in Philadelphia‐positive chronic myeloid leukemia patients with a reciprocal t(3;21)

Abstract The translocation t(3;21)(q26;q22) is a rare recurring clonal abnormality, either preceding or associated with blast crisis in Philadelphia chromosome‐positive chronic myeloid leukemia (CML) patients. We previously localized the chromosomal breakpoints at 3q26.2 and 21q22.2, using high resolution chromosomal analysis. Two genes of interest are localized near the breakpoints, the transferrin receptor gene and the ETS2 proto‐oncogene. Their chromosomal localizations, determined by in situ hybridization on normal metaphase cells, were 3q29 and 21q22.3, respectively. They underwent a reciprocal translocation in patients with t(3;21). Their structures were not altered by the translocation, and both were expressed to varying levels in t(3;21) patients. Southern blotting investigations showed that the structure of other single‐copy genes, including FIM3, localized near the breakpoints, were not affected by the translocation. An analysis of ETS2 expression performed on CML patients without t(3;21) showed the presence of the transcript in 100% of the blast crises, but only in 20% of the chronic‐phase patients. Thus ETS2 expression may either be linked to or play a role in CML progression.