Impact of mutational profiles on response of primary oestrogen receptor-positive breast cancers to oestrogen deprivation

Pre-surgical studies allow study of the relationship between mutations and response of oestrogen receptor-positive (ER+) breast cancer to aromatase inhibitors (AIs) but have been limited to small biopsies. Here in phase I of this study, we perform exome sequencing on baseline, surgical core-cuts and blood from 60 patients (40 AI treated, 20 controls). In poor responders (based on Ki67 change), we find significantly more somatic mutations than good responders. Subclones exclusive to baseline or surgical cores occur in ∼30% of tumours. In phase II, we combine targeted sequencing on another 28 treated patients with phase I. We find six genes frequently mutated: PIK3CA, TP53, CDH1, MLL3, ABCA13 and FLG with 71% concordance between paired cores. TP53 mutations are associated with poor response. We conclude that multiple biopsies are essential for confident mutational profiling of ER+ breast cancer and TP53 mutations are associated with resistance to oestrogen deprivation therapy

The gene for the α2 chain of the human fibrillar collagen type XI (COL11A2) assigned to the short arm of chromosome 6

A cosmid clone (CosHcol.11) containing the α2(XI) collagen gene (COL11A2) has been isolated. The gene contains conserved DNA and amino-acid sequences characteristic of fibril forming collagen, which is in accordance with the classification of type XI collagen as a fibrillar collagen. The genomic clone containing the α2(XI) gene has been used as probe in the Southern blot analysis of DNA from a panel of human/hamster somatic cell hybrids containing different numbers and combinations of human chromosomes. Synteny analysis revealed that only chromosome 6 showed complete concordant segregation with COL11A2. Furthermore, the gene was regionally mapped to the short arm of chromosome 6 by using a hybrid which contained only the long arm of the chromosome.link_to_subscribed_fulltex

The human α2(XI) collagen (COL11A2) chain. Molecular cloning of cDNA and genomic DNA reveals characteristics of a fibrillar collagen with differences in genomic organization

We have isolated three overlapping cDNA clones encoding the proα2(XI) collagen chain from a human chondrocyte cDNA library. Together, the cDNAs code for 257 uninterrupted Gly-X-Y triplets (almost 80% of the triple helical domain) and about 200 amino acid residues of the carboxyl telopeptide and carboxyl propeptide. The identification of the clones as proα2(XI) cDNAs was based on the complete identity between the amino acid sequences of three tryptic peptides derived from human α2(XI) collagen and the cDNA-derived sequence. We have also sequenced six exons within a human genomic α2(XI) cosmid clone. This sequence shows that although type XI collagen belongs to the fibril-forming class of collagens, there are substantial differences in exon sizes at the 3' end of the gene when comparing the α2(XI) gene with those of human types I, II, and III collagens. Finally, proα2(XI) cDNA has been used as a probe to determine the location of the gene by in situ hybridization of chromosome spreads. The results demonstrate that the gene is located close to the region p212 on chromosome 6. Northern blot analysis shows that the gene is expressed in cartilage but not in adult liver, skin, and tendon.link_to_subscribed_fulltex

A cis-acting control region is required exclusively for the tissue-specific imprinting of Gnas

Genomic imprinting brings about allele-specific silencing according to parental origin1. Silencing is controlled by cis-acting regulatory regions that are differentially marked during gametogenesis and can act over hundreds of kilobases to silence many genes2, 3, 4, 5, 6. Two candidate imprinting control regions (ICRs) have been identified at the compact imprinted Gnas cluster on distal mouse chromosome 2, one at exon 1A upstream of Gnas itself7 and one covering the promoters for Gnasxl and the antisense Nespas (ref. 8). This imprinted cluster is complex, containing biallelic, maternally and paternally expressed transcripts that share exons9. Gnas itself is mainly biallelically expressed but is weakly paternally repressed in specific tissues10. Here we show that a paternally derived targeted deletion of the germline differentially methylated region at exon 1A abolishes tissue-specific imprinting of Gnas. This rescues the abnormal phenotype of mice with a maternally derived Gnas mutation11, 12. Imprinting of alternative transcripts, Nesp, Gnasxl and Nespas (ref. 13), in the cluster is unaffected. The results establish that the differentially methylated region at exon 1A contains an imprinting control element that specifically regulates Gnas and comprises a characterized ICR for a gene that is only weakly imprinted in a minority of tissues. There must be a second ICR regulating the alternative transcripts