Integrated genome-wide genotyping and gene expression profiling reveals BCL11B as a putative oncogene in acute myeloid leukemia with 14q32 aberrations.

Acute myeloid leukemia is a neoplasm characterized by recurrent molecular aberrations traditionally demonstrated by cytogenetic analyses. We used high density genome-wide genotyping and gene expression profiling to reveal acquired cryptic abnormalities in acute myeloid leukemia. By genome-wide genotyping of 137 cases of primary acute myeloid leukemia, we disclosed a recurrent focal amplification on chromosome 14q32, which included the genes BCL11B, CCNK, C14orf177 and SETD3, in two cases. In the affected cases, the BCL11B gene showed consistently high mRNA expression, whereas the expression of the other genes was unperturbed. Fluorescence in situ hybridization on 40 cases of acute myeloid leukemia with high BCL11B mRNA expression [2.5-fold above median; 40 out of 530 cases (7.5%)] revealed 14q32 abnormalities in two additional cases. In the four BCL11B-rearranged cases the 14q32 locus was fused to different partner chromosomes. In fact, in two cases, we demonstrated that the focal 14q32 amplifications were integrated into transcriptionally active loci. The translocations involving BCL11B result in increased expression of full-length BCL11B protein. The BCL11B-rearranged acute myeloid leukemias expressed both myeloid and T-cell markers. These biphenotypic acute leukemias all carried FLT3 internal tandem duplications, a characteristic marker of acute myeloid leukemia. BCL11B mRNA expression in acute myeloid leukemia appeared to be strongly associated with expression of other T-cell-specific genes. Myeloid 32D(GCSF-R) cells ectopically expressing Bcl11b showed decreased proliferation rate and less maturation. In conclusion, by an integrated approach involving high-throughput genome-wide genotyping and gene expression profiling we identified BCL11B as a candidate oncogene in acute myeloid leukemia.

Acquired mutations in ASXL1 in acute myeloid leukemia: prevalence and prognostic value.

Somatic mutations in the additional sex comb-like 1 (ASXL1) gene have been described in various types of myeloid malignancies, including acute myeloid leukemia. Analysis of novel markers, such as ASXL1 mutations, in independent clinical trials is indispensable before considering them for clinical decision-making. We analyzed 882 well-characterized acute myeloid leukemia cases to determine the prevalence and prognostic impact of ASXL1 exon12 mutations. Truncating ASXL1 mutations were present in 46 cases (5.3%). ASXL1 mutations were inversely associated with FLT3 internal tandem duplications and mutually exclusive with NPM1 mutations. ASXL1 mutations were an unfavorable prognostic factor as regards survival (median overall survival 15.9 months vs. 22.3 months; P=0.019), with a significantly lower complete response rate (61% vs. 79.6%; P=0.004). In multivariate analyses, ASXL1 mutations were independently associated with inferior poor overall survival (HR 1.52, P=0.032). In conclusion, ASXL1 mutations are common mutations in acute myeloid leukemia and indicate a poor therapy outcome.

Acquired mutations in the genes encoding IDH1 and IDH2 both are recurrent aberrations in acute myeloid leukemia: prevalence and prognostic value.

Somatic mutations in isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) were recently demonstrated in acute myeloid leukemia (AML), but their prevalence and prognostic impact remain to be explored in large extensively characterized AML series, and also in various other hematologic malignancies. Here, we demonstrate in 893 newly diagnosed cases of AML mutations in the IDH1 (6%) and IDH2 (11%) genes. Moreover, we identified IDH mutations in 2 JAK2 V617F myeloproliferative neoplasias (n = 96), a single case of acute lymphoblastic leukemia (n = 96), and none in chronic myeloid leukemias (n = 81). In AML, IDH1 and IDH2 mutations are more common among AML with normal karyotype and NPM1(mutant) genotypes. IDH1 mutation status is an unfavorable prognostic factor as regards survival in a composite genotypic subset lacking FLT3(ITD) and NPM1(mutant). Thus, IDH1 and IDH2 mutations are common genetic aberrations in AML, and IDH1 mutations may carry prognostic value in distinct subtypes of AML.

Impaired nipple development and parturition in LGR7 knockout mice.

LGR7 is a G-protein coupled receptor with structural homology to the gonadotrophin and thyrotrophin receptors. Recently, LGR7 was deorphanized, and it was shown that relaxin is the ligand for LGR7. To further study the function of this receptor, mice deficient for LGR7 were generated by replacing part of the transmembrane-encoding region with a LacZ reporter cassette. Here we show that LGR7 is expressed in various tissues, including the uterus, heart, brain, and testis. Fertility studies using female LGR7-/- mice showed normal fertility and litter size. However, some females were incapable of delivering their pups, and several pups were found dead. Moreover, all offspring died within 24 to 48 h after delivery because female LGR7-/- mice were unable to feed their offspring due to impaired nipple development. In some male LGR7-/- mice, spermatogenesis was impaired, leading to azoospermia and a reduction in fertility. Interestingly, these phenomena were absent in mutant mice at older ages or in later generations. Taken together, results from LGR7 knockout mice indicate an essential role for the LGR7 receptor in nipple development during pregnancy. Moreover, a defect in parturition was observed, suggesting a role for LGR7 in the process of cervical ripening.