RESUMO
The pathogenesis of duodenal tumors in the inherited tumor syndromes familial adenomatous polyposis (FAP) and MUTYH-associated polyposis (MAP) is poorly understood. This study aimed to identify genes that are significantly mutated in these tumors and to explore the effects of these mutations. Whole exome and whole transcriptome sequencing identified recurrent somatic coding variants of phosphatidylinositol N-acetylglucosaminyltransferase subunit A (PIGA) in 19/70 (27%) FAP and MAP duodenal adenomas, and further confirmed the established driver roles for APC and KRAS. PIGA catalyzes the first step in glycosylphosphatidylinositol (GPI) anchor biosynthesis. Flow cytometry of PIGA-mutant adenoma-derived and CRISPR-edited duodenal organoids confirmed loss of GPI anchors in duodenal epithelial cells and transcriptional profiling of duodenal adenomas revealed transcriptional signatures associated with loss of PIGA. IMPLICATIONS: PIGA somatic mutation in duodenal tumors from patients with FAP and MAP and loss of membrane GPI-anchors may present new opportunities for understanding and intervention in duodenal tumorigenesis.
Assuntos
Polipose Adenomatosa do Colo , Neoplasias Duodenais , Glicosilfosfatidilinositóis , Mutação , Humanos , Glicosilfosfatidilinositóis/metabolismo , Glicosilfosfatidilinositóis/genética , Neoplasias Duodenais/genética , Neoplasias Duodenais/metabolismo , Neoplasias Duodenais/patologia , Polipose Adenomatosa do Colo/genética , Polipose Adenomatosa do Colo/metabolismo , Polipose Adenomatosa do Colo/patologia , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Carcinogênese/genética , Masculino , FemininoAssuntos
Pólipos Adenomatosos/patologia , DNA Glicosilases/genética , Neoplasias Duodenais/epidemiologia , Pólipos Adenomatosos/diagnóstico , Pólipos Adenomatosos/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias Duodenais/diagnóstico , Neoplasias Duodenais/genética , Neoplasias Duodenais/patologia , Duodenoscopia/estatística & dados numéricos , Duodeno/diagnóstico por imagem , Duodeno/patologia , Feminino , Humanos , Mucosa Intestinal/diagnóstico por imagem , Mucosa Intestinal/patologia , Masculino , Pessoa de Meia-Idade , Prevalência , Estudos Prospectivos , Adulto JovemRESUMO
Liquid biopsies offer the potential to monitor cancer response and resistance to therapeutics in near real-time. However, the plasma cell free DNA (cfDNA) level can be low and the fraction of circulating tumour DNA (ctDNA) bearing a mutation - lower still. Detection of tumour-derived mutations in ctDNA is thus challenging and requires highly sensitive and specific assays. Droplet digital PCR (ddPCR) is a technique that enables exquisitely sensitive detection and quantification of DNA/RNA markers from very limiting clinical samples, including plasma. The Bio-Rad QX200 ddPCR system provides absolute quantitation of target DNA molecules using fluorescent dual-labelled probes. Critical to accurate sample analysis are validated assays that are highly specific, reproducible, and with known performance characteristics, especially with respect to false positives. We present a systematic approach to the development and optimisation of singleplex and multiplex ddPCR assays for the detection of point mutations with a focus on ensuring extremely low false positives whilst retaining high sensitivity. We also present a refined method to determine cfDNA extraction efficiency allowing for more accurate extrapolation of mutational levels in source samples. We have applied these approaches to successfully analyse many ctDNA samples from multiple clinical studies and generated exploratory data of high quality.
Assuntos
DNA Tumoral Circulante/genética , Reação em Cadeia da Polimerase Multiplex/métodos , Mutação/genética , Bioensaio , DNA Tumoral Circulante/sangue , Sondas de DNA/metabolismo , Humanos , Proteínas Proto-Oncogênicas B-raf/genética , Proteínas Proto-Oncogênicas p21(ras)/genética , Temperatura , Fatores de Transcrição/genéticaRESUMO
Purpose: Duodenal polyposis and cancer are important causes of morbidity and mortality in familial adenomatous polyposis (FAP) and MUTYH-associated polyposis (MAP). This study aimed to comprehensively characterize somatic genetic changes in FAP and MAP duodenal adenomas to better understand duodenal tumorigenesis in these disorders.Experimental Design: Sixty-nine adenomas were biopsied during endoscopy in 16 FAP and 10 MAP patients with duodenal polyposis. Ten FAP and 10 MAP adenomas and matched blood DNA samples were exome sequenced, 42 further adenomas underwent targeted sequencing, and 47 were studied by array comparative genomic hybridization. Findings in FAP and MAP duodenal adenomas were compared with each other and to the reported mutational landscape in FAP and MAP colorectal adenomas.Results: MAP duodenal adenomas had significantly more protein-changing somatic mutations (P = 0.018), truncating mutations (P = 0.006), and copy number variants (P = 0.005) than FAP duodenal adenomas, even though MAP patients had lower Spigelman stage duodenal polyposis. Fifteen genes were significantly recurrently mutated. Targeted sequencing of APC, KRAS, PTCHD2, and PLCL1 identified further mutations in each of these genes in additional duodenal adenomas. In contrast to MAP and FAP colorectal adenomas, neither exome nor targeted sequencing identified WTX mutations (P = 0.0017).Conclusions: The mutational landscapes in FAP and MAP duodenal adenomas overlapped with, but had significant differences to those reported in colorectal adenomas. The significantly higher burden of somatic mutations in MAP than FAP duodenal adenomas despite lower Spigelman stage disease could increase cancer risk in the context of apparently less severe benign disease. Clin Cancer Res; 23(21); 6721-32. ©2017 AACR.