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International audience; In recent years, through whole genome analyses, convincing evidence for the contribution of genetic predisposition to childhood B-cell precursor-acute lymphoblastic leukemia (BCP-ALL) due to altered PAX5 has been provided. A recurrent mutation p.Gly183Ser affecting the octapeptide domain has been described in three unrelated families and a p.Arg38His mutation affecting the DNA-binding paired domain reported in another one. We strengthen here the assumption of the inherited character of familial BCP-ALL by identifying the PAX5 p.Arg38His mutation in a family in which the three children developed BCP-ALL. One relapsed two years after his initial diagnosis and was allografted with his brother's cells before the latter developed BCP-ALL. The patient allografted relapsed later from donor-related cells. By syngeneic transplantations in mice, we showed that p.Arg38His expression does not abrogate the engraftment capacity of transduced Pax5-/pro-B cells unlike wild type PAX5-rescued Pax5-/pro-B cells and can predispose to BCP-ALL. Through functional and molecular analyses, we demonstrated that p.Arg38His acts as a hypomorphic variant altering the pattern of expression of PAX5 target genes. Our data highlight the importance of transcriptional deregulation, particularly of genes involved in B cell differentiation in familial BCP-ALL. We demonstrated that inherited genetic basis of susceptibility to BCP-ALL has been underestimated and should be considered before any familial allograft.

Myelodysplastic syndromes (MDS) represent a heterogeneous group of clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis leading to peripheral cytopenias and in a substantial proportion of cases to acute myeloid leukemia. The deletion of the long arm of chromosome 11, del(11q), is a rare but recurrent clonal event in MDS. Here, we detail the largest series of 113 cases of MDS and myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN) harboring a del(11q) analyzed at clinical, cytological, cytogenetic, and molecular levels. Female predominance, a survival prognosis similar to other MDS, a low monocyte count, and dysmegakaryopoiesis were the specific clinical and cytological features of del(11q) MDS. In most cases, del(11q) was isolated, primary and interstitial encompassing the 11q22-23 region containing ATM, KMT2A, and CBL genes. The common deleted region at 11q23.2 is centered on an intergenic region between CADM1 (also known as Tumor Suppressor in Lung Cancer 1) and NXPE2. CADM1 was expressed in all myeloid cells analyzed in contrast to NXPE2. At the functional level, the deletion of Cadm1 in murine Lineage-Sca1+Kit+ cells modifies the lymphoid-to-myeloid ratio in bone marrow, although not altering their multilineage hematopoietic reconstitution potential after syngenic transplantation. Together with the frequent simultaneous deletions of KMT2A, ATM, and CBL and mutations of ASXL1, SF3B1, and CBL, we show that CADM1 may be important in the physiopathology of the del(11q) MDS, extending its role as tumor-suppressor gene from solid tumors to hematopoietic malignancies.

Key Points We detail at clinical, cytological, cytogenetic, and molecular levels 113 cases of MDS and MDS/MPN with del(11q), a rare recurrent event.CADM1, a tumor suppressor gene identified initially in solid tumors, ATM, CBL, and KMT2A are deleted and/or mutated in del(11q)., Visual Abstract, Myelodysplastic syndromes (MDS) represent a heterogeneous group of clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis leading to peripheral cytopenias and in a substantial proportion of cases to acute myeloid leukemia. The deletion of the long arm of chromosome 11, del(11q), is a rare but recurrent clonal event in MDS. Here, we detail the largest series of 113 cases of MDS and myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN) harboring a del(11q) analyzed at clinical, cytological, cytogenetic, and molecular levels. Female predominance, a survival prognosis similar to other MDS, a low monocyte count, and dysmegakaryopoiesis were the specific clinical and cytological features of del(11q) MDS. In most cases, del(11q) was isolated, primary and interstitial encompassing the 11q22-23 region containing ATM, KMT2A, and CBL genes. The common deleted region at 11q23.2 is centered on an intergenic region between CADM1 (also known as Tumor Suppressor in Lung Cancer 1) and NXPE2. CADM1 was expressed in all myeloid cells analyzed in contrast to NXPE2. At the functional level, the deletion of Cadm1 in murine Lineage-Sca1+Kit+ cells modifies the lymphoid-to-myeloid ratio in bone marrow, although not altering their multilineage hematopoietic reconstitution potential after syngenic transplantation. Together with the frequent simultaneous deletions of KMT2A, ATM, and CBL and mutations of ASXL1, SF3B1, and CBL, we show that CADM1 may be important in the physiopathology of the del(11q) MDS, extending its role as tumor-suppressor gene from solid tumors to hematopoietic malignancies.