Inversion of chromosome 16 and uncommon rearrangements of the CBFB and MYH11 genes in therapy-related acute myeloid leukemia: rare events related to DNA-topoisomerase II inhibitors?

To evaluate the frequency of inversion of chromosome 16 (inv[16]) and the type of rearrangement of the CBFB and MYH11 genes in therapy-related acute myeloid leukemia (t-AML) and to evaluate a possible relationship to specific types of previous chemotherapy. Cytogenetic studies were performed in 180 consecutive patients with therapy-related myelodysplasia (t-MDS) or t-AML in Copenhagen and in 270 consecutive patients in Chicago. Leukemic cells were available for studies of the molecular biology in 72 patients, including four with inv(16). An inv(16)(p13q22) was observed in only two of 180 cases of t-MDS and t-AML in Copenhagen and in only four of 270 cases of t-MDS and t-AML in Chicago. Four patients with t-AML and inv(16) previously had received combination chemotherapy, which included an alkylating agent, and in two a DNA topoisomerase II inhibitor was included (mitoxantrone and etoposide). One patient had received paclitaxel followed by etoposide and one patient had received radiotherapy only. One patient, previously treated with mitoxantrone and cyclophosphamide for breast cancer, presented a new and, to our knowledge not previously reported, type of fusion transcript, with breakpoint at nt 399 of the CBFB gene and at nt 2134 of the MYH11 gene. Two patients previously treated with alkylating agents both presented the less common type D transcript, whereas the most common A transcript, observed in 80% of acute myeloid leukemia (AML) de novo with inv(16), only was observed in the patient treated with paclitaxel and etoposide for leiomyosarcoma. Bone marrow or blood cells from 68 patients with t-MDS and t-AML without an inv(16) all were found to be negative for chimeric rearrangement between the CBFB gene and the MYH11 gene. The present study and a review of the literature shows that inv(16) is an uncommon aberration in t-AML and, like balanced translocations to chromosome bands 11q23 and 21q22 and the t(15;17), often is associated with prior chemotherapy with DNA topoisomerase II inhibitors. Breakpoints within the MYH11 gene may vary between t-AML and AML de novo.