Three-way complex translocations in infant acute myeloid leukemia with t(7;12)(q36;p13): the incidence and correlation of a HLXB9 overexpression.

The t(7;12)(q36;p13) is one of the recurrent cytogenetic abnormalities that involves the ETV6 gene. It is found in patients suffering with infantile acute myeloid leukemia (AML). We reviewed the cytogenetic and clinical findings of 215 pediatric patients (ages </=17) who were diagnosed with AML to check for abnormalities of 7q and/or 12p. Fluorescence in situ hybridization (FISH) analysis using an ETV6 (12p13) break-apart probe was done to confirm the breakage of the ETV6 gene on 12p. We also performed immunohistochemistry to verify the upregulated expression of the HLXB9 protein, which is coded by the HLXB9 gene at 7q36. Three patients (1.4%) with t(7;12) were detected and they made up 15.8% of the patients who were less than 24 months old. New three-way complex translocations were found in two cases - t(5;7;12)(q31;q36;p13) and t(1;7;12)(q25;q36;p13) - and we detected these by performing FISH. All three patients died early during treatment due to multiple organ failure or relapse. HLXB9 overexpression was proven by immunohistochemistry for the first time in this study. In connection with this, we prudently propose that downregulation of the HLXB9 expression may be a new treatment strategy for AML patients with t(7;12).