Brca1 deficiency causes bone marrow failure and spontaneous hematologic malignancies in mice.

BRCA1 is critical for maintenance of genomic stability and interacts directly with several proteins that regulate hematopoietic stem cell function and are part of the Fanconi anemia (FA) double-strand break DNA repair pathway. The effects of complete BRCA1 deficiency on bone marrow (BM) function are unknown. To test the hypothesis that Brca1 is essential in hematopoiesis, we developed a conditional mouse model with Mx1-Cre-mediated Brca1 deletion. Mice lacking Brca1 in the BM have baseline cytopenias and develop spontaneous bone marrow failure or diverse hematologic malignancies by 6 months of age. Brca1(-/-) BM cells have a reduced capacity to form hematopoietic colonies in vitro and to reconstitute hematopoiesis in irradiated recipients, consistent with a hematopoietic progenitor functional defect. Brca1(-/-) BM cells also show FA-like hypersensitivity to the DNA crosslinking agent mitomycin C, and karyotypes feature genomic instability. Taken together, our results show that loss of Brca1 in murine BM causes hematopoietic defects similar to those seen in people with FA, which provides strong evidence that Brca1 is critical for normal hematopoiesis and that Brca1 is a bona fide FA-like gene.

Identifying Inherited and Acquired Genetic Factors Involved in Poor Stem Cell Mobilization and Donor-Derived Malignancy.

Analysis of the clinical characteristics of hematopoietic stem cell transplant (HSCT) donors has proven beneficial for identifying cases of heritable hematopoietic disorders. This study examines poor peripheral blood hematopoietic stem cell mobilization after granulocyte colony-stimulating factor administration among 328 donors as a potential marker for suspected familial predisposition to myeloid malignancies. Here, we present data comparing the clinical characteristics of poor-mobilizing versus nonpoor-mobilizing donors and the results of panel-based sequencing of hematopoietic genes in poor-mobilizing donors. From this analysis, we identified a novel case of a donor-derived myelodysplastic syndrome in an HSCT recipient that is consistent with clonal evolution of TET2-mutated clonal hematopoiesis of indeterminate potential (CHIP) within the donor. This study demonstrates the potential risk of using hematopoietic stem cells from a donor with CHIP and raises the question of whether there should be increased screening measures to identify such donors.

Inherited mutations in cancer susceptibility genes are common among survivors of breast cancer who develop therapy-related leukemia.

BACKGROUND: Risk factors for the development of therapy-related leukemia (TRL), an often lethal late complication of cytotoxic therapy, remain poorly understood and may differ for survivors of different malignancies. Survivors of breast cancer (BC) now account for the majority of TRL cases, making the study of TRL risk factors in this population a priority. METHODS: Subjects with TRL after cytotoxic therapy for a primary BC were identified from the TRL registry at The University of Chicago. Those with an available germline DNA sample were screened with a comprehensive gene panel covering known inherited BC susceptibility genes. Clinical and TRL characteristics of all subjects and those with identified germline mutations were described. RESULTS: Nineteen of 88 survivors of BC with TRL (22%) had an additional primary cancer and 40 of the 70 survivors with an available family history (57%) had a close relative with breast, ovarian, or pancreatic cancer. Of the 47 subjects with available DNA, 10 (21%) were found to carry a deleterious inherited mutation in BRCA1 (3 subjects; 6%), BRCA2 (2 subjects; 4%), TP53 (tumor protein p53) (3 subjects; 6%), CHEK2 (checkpoint kinase 2) (1 subject; 2%), and PALB2 (partner and localizer of BRCA2) (1 subject; 2%). CONCLUSIONS: Survivors of BC with TRL have personal and family histories suggestive of inherited cancer susceptibility and frequently carry germline mutations in BC susceptibility genes. The data from the current study support the role of these genes in TRL risk and suggest that long-term follow-up studies of women with germline mutations who are treated for BC and functional studies of the effects of heterozygous mutations in these genes on bone marrow function after cytotoxic exposures are warranted. Cancer 2016;122:304-311. © 2015 American Cancer Society.

Inherited predisposition to breast cancer among African American women.

African Americans have a disproportionate burden of aggressive young-onset breast cancer. Genomic testing for inherited predisposition to breast cancer is increasingly common in clinical practice, but comprehensive mutation profiles remain unknown for most minority populations. We evaluated 289 patients who self-identified as African American with primary invasive breast cancer and with personal or family cancer history or tumor characteristics associated with high genetic risk for all classes of germline mutations in known breast cancer susceptibility genes using a validated targeted capture and multiplex sequencing approach. Sixty-eight damaging germline mutations were identified in 65 (22 %, 95 % CI 18-28 %) of the 289 subjects. Proportions of patients with unequivocally damaging mutations in a breast cancer gene were 26 % (47/180; 95 % confident interval [CI] 20-33 %) of those with breast cancer diagnosis before age 45; 25 % (26/103; 95 % CI 17-35 %) of those with triple-negative breast cancer (TNBC); 29 % (45/156; 95 % CI 22-37 %) of those with a first or second degree relative with breast cancer before age 60 or with ovarian cancer; and 57 % (4/7; 95 % CI 18-90 %) of those with both breast and ovarian cancer. Of patients with mutations, 80 % (52/65) carried mutations in BRCA1 and BRCA2 genes and 20 % (13/65) carried mutations in PALB2, CHEK2, BARD1, ATM, PTEN, or TP53. The mutational allelic spectrum was highly heterogeneous, with 57 different mutations in 65 patients. Of patients meeting selection criteria other than family history (i.e., with young age at diagnosis or TNBC), 48 % (64/133) had very limited information about the history of cancer in previous generations of their families. Mutations in BRCA1 and BRCA2 or another breast cancer gene occur in one in four African American breast cancer patients with early onset disease, family history of breast or ovarian cancer, or TNBC. Each of these criteria defines patients who would benefit from genomic testing and novel therapies targeting DNA repair pathways.

Natural killer/T-cell lymphoma and secondary haemophagocytic lymphohistiocytosis in pregnancy.

Haemophagocytic lymphohistiocytosis (HLH) is a rare and potentially fatal disorder. It is challenging to diagnose due to its rarity and variation in clinical presentation, laboratory abnormalities and underlying aetiologies. A reproductive-aged woman, gravida 2 para 1001 at 27 weeks gestation presented with fever, hypotension and subacute upper respiratory infection. She delivered a male infant by caesarean section secondary to fetal distress. Subsequently, she was diagnosed with T-cell lymphoma and secondary HLH. Despite management with supportive care and multiple chemotherapeutic agents, she ultimately died of multiorgan failure. Patients with HLH secondary to malignancy have a particularly poor prognosis. This case highlights the importance of considering secondary HLH in the differential diagnosis of a patient with fever, pancytopenia and systemic symptoms of unclear aetiology in pregnancy.

Germline ETV6 mutations in familial thrombocytopenia and hematologic malignancy.

We report germline missense mutations in ETV6 segregating with the dominant transmission of thrombocytopenia and hematologic malignancy in three unrelated kindreds, defining a new hereditary syndrome featuring thrombocytopenia with susceptibility to diverse hematologic neoplasms. Two variants, p.Arg369Gln and p.Arg399Cys, reside in the highly conserved ETS DNA-binding domain. The third variant, p.Pro214Leu, lies within the internal linker domain, which regulates DNA binding. These three amino acid sites correspond to hotspots for recurrent somatic mutation in malignancies. Functional studies show that the mutations abrogate DNA binding, alter subcellular localization, decrease transcriptional repression in a dominant-negative fashion and impair hematopoiesis. These familial genetic studies identify a central role for ETV6 in hematopoiesis and malignant transformation. The identification of germline predisposition to cytopenias and cancer informs the diagnosis and medical management of at-risk individuals.