👤 Francesca Micci

Mixed phenotype acute leukemia (MPAL) is a rare hematologic malignancy in which the leukemic cells cannot be assigned to any specific lineage. The lack of well-defined, pathogenetically relevant diagnostic criteria makes the clinical handling of MPAL patients challenging. We herein report the genetic findings in bone marrow cells from two pediatric MPAL patients. Bone marrow cells were examined using G-banding, array comparative genomic hybridization, RNA sequencing, reverse transcription polymerase chain reaction, Sanger sequencing, and fluorescence in situ hybridization. In the first patient, the genetic analyses revealed structural aberrations of chromosomal bands 8p11, 10p11, 11q21, and 17p11, the chimeras MLLT10::PICALM and PICALM::MLLT10, and imbalances (gains/losses) on chromosomes 2, 4, 8, 13, and 21. A submicroscopic deletion in 21q was also found including the RUNX1 locus. In the second patient, there were structural aberrations of chromosome bands 1p32, 8p11, 12p13, 20p13, and 20q11, the chimeras ETV6::LEXM and NCOA6::ETV6, and imbalances on chromosomes 2, 8, 11, 12, 16, 19, X, and Y. The leukemic cells from both MPAL patients carried chromosome aberrations resulting in fusion genes as well as genomic imbalances resulting in gain and losses of many gene loci. The detected fusion genes probably represent the main leukemogenic events, although the gains and losses are also likely to play a role in leukemogenesis. Show less

Acute undifferentiated leukemia (AUL) is leukemia which does not express lineage-specific antigens. Such cases are rare, accounting for 2.7% of all acute leukemia. The reported genetic information of AULs is limited to less than 100 cases with abnormal karyotypes and a few cases carrying chimeric genes or point mutation of a gene. We herein present the genetic findings and clinical features of a case of AUL. Bone marrow cells obtained at diagnosis from a 31-year-old patient with AUL were genetically investigated. G-Banding karyotyping revealed an abnormal karyotype: 45,X,-Y,t(5;10)(q35;p12),del(12)(p13)[12]/46,XY[5]. Array comparative genomic hybridization examination confirmed the del(12)(p13) seen by G-banding but also detected additional losses from 1q, 17q, Xp, and Xq corresponding to the deletion of approximately 150 genes from these five chromosome arms. RNA sequencing detected six HNRNPH1::MLLT10 and four MLLT10::HNRNPH1 chimeric transcripts, later confirmed by reverse-transcription polymerase chain reaction together with Sanger sequencing. Fluorescence in situ hybridization analysis showed the presence of HNRNPH1::MLLT10 and MLLT10::HNRNPH1 chimeric genes. To the best of our knowledge, this is the first AUL in which a balanced t(5;10)(q35;p12) leading to fusion of HNRNPH1 with MLLT10 has been detected. The relative leukemogenic importance of the chimeras and gene losses cannot be reliably assessed, but both mechanisms were probably important in the development of AUL. Show less