RESUMO
Relapse of acute lymphoblastic leukemia (ALL) remains a leading cause of childhood death. Prior studies have shown clonal mutations at relapse often arise from relapse-fated subclones that exist at diagnosis. However, the genomic landscape, evolutionary trajectories and mutational mechanisms driving relapse are incompletely understood. In an analysis of 92 cases of relapsed childhood ALL, incorporating multimodal DNA and RNA sequencing, deep digital mutational tracking and xenografting to formally define clonal structure, we identify 50 significant targets of mutation with distinct patterns of mutational acquisition or enrichment. CREBBP, NOTCH1, and Ras signaling mutations rose from diagnosis subclones, whereas variants in NCOR2, USH2A and NT5C2 were exclusively observed at relapse. Evolutionary modeling and xenografting demonstrated that relapse-fated clones were minor (50%), major (27%) or multiclonal (18%) at diagnosis. Putative second leukemias, including those with lineage shift, were shown to most commonly represent relapse from an ancestral clone rather than a truly independent second primary leukemia. A subset of leukemias prone to repeated relapse exhibited hypermutation driven by at least three distinct mutational processes, resulting in heightened neoepitope burden and potential vulnerability to immunotherapy. Finally, relapse-driving sequence mutations were detected prior to relapse using deep digital PCR at levels comparable to orthogonal approaches to monitor levels of measurable residual disease. These results provide a genomic framework to anticipate and circumvent relapse by earlier detection and targeting of relapse-fated clones.
Assuntos
Evolução Clonal , Leucemia-Linfoma Linfoblástico de Células Precursoras , Criança , Evolução Clonal/genética , Genômica , Humanos , Mutação , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , RecidivaRESUMO
Nucleotide excision repair (NER) is one of the main DNA repair pathways that protect cells against genomic damage. Disruption of this pathway can contribute to the development of cancer and accelerate aging. Mutational characteristics of NER-deficiency may reveal important diagnostic opportunities, as tumors deficient in NER are more sensitive to certain treatments. Here, we analyzed the genome-wide somatic mutational profiles of adult stem cells (ASCs) from NER-deficient Ercc1 -/Δ mice. Our results indicate that NER-deficiency increases the base substitution load twofold in liver but not in small intestinal ASCs, which coincides with the tissue-specific aging pathology observed in these mice. Moreover, NER-deficient ASCs of both tissues show an increased contribution of Signature 8 mutations, which is a mutational pattern with unknown etiology that is recurrently observed in various cancer types. The scattered genomic distribution of the base substitutions indicates that deficiency of global-genome NER (GG-NER) underlies the observed mutational consequences. In line with this, we observe increased Signature 8 mutations in a GG-NER-deficient human organoid culture, in which XPC was deleted using CRISPR-Cas9 gene-editing. Furthermore, genomes of NER-deficient breast tumors show an increased contribution of Signature 8 mutations compared with NER-proficient tumors. Elevated levels of Signature 8 mutations could therefore contribute to a predictor of NER-deficiency based on a patient's mutational profile.
Assuntos
Reparo do DNA/genética , Mutação , Neoplasias/genética , Células-Tronco Adultas , Animais , Neoplasias da Mama/genética , Estudos de Coortes , Análise Mutacional de DNA , DNA de Neoplasias , Proteínas de Ligação a DNA/genética , Endonucleases/genética , Feminino , Humanos , Camundongos , Organoides , Técnicas de Cultura de Tecidos , Sequenciamento Completo do GenomaRESUMO
BACKGROUND: Base substitution catalogues represent historical records of mutational processes that have been active in a cell. Such processes can be distinguished by various characteristics, like mutation type, sequence context, transcriptional and replicative strand bias, genomic distribution and association with (epi)-genomic features. RESULTS: We have created MutationalPatterns, an R/Bioconductor package that allows researchers to characterize a broad range of patterns in base substitution catalogues to dissect the underlying molecular mechanisms. Furthermore, it offers an efficient method to quantify the contribution of known mutational signatures within single samples. This analysis can be used to determine whether certain DNA repair mechanisms are perturbed and to further characterize the processes underlying known mutational signatures. CONCLUSIONS: MutationalPatterns allows for easy characterization and visualization of mutational patterns. These analyses willsupport fundamental research into mutational mechanisms and may ultimately improve cancer diagnosis and treatment strategies. MutationalPatterns is freely available at http://bioconductor.org/packages/MutationalPatterns .
Assuntos
Genoma Humano , Mutação/genética , Software , Adulto , Células-Tronco Adultas/metabolismo , Humanos , Transcrição GênicaRESUMO
Characterization of mutational processes in adult stem cells (ASCs) will improve our understanding of aging-related diseases, such as cancer and organ failure, and may ultimately help prevent the development of these diseases. Here, we present a method for cataloging mutations in individual human ASCs without the necessity of using error-prone whole-genome amplification. Single ASCs are expanded in vitro into clonal organoid cultures to generate sufficient DNA for accurate whole-genome sequencing (WGS) analysis. We developed a data-analysis pipeline that identifies with high confidence somatic variants that accumulated in vivo in the original ASC. These genome-wide mutation catalogs are valuable resources for the characterization of the underlying mutational mechanisms. In addition, this protocol can be used to determine the effects of culture conditions or mutagen exposure on mutation accumulation in ASCs in vitro. Here, we describe a protocol for human liver ASCs that can be completed over a period of 3-4 months with hands-on time of â¼5 d.
Assuntos
Células-Tronco Adultas/citologia , Acúmulo de Mutações , Mutação/genética , Organoides/citologia , Sequenciamento Completo do Genoma/métodos , Células Cultivadas , DNA/análise , DNA/genética , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Fígado/citologiaRESUMO
Breast cancer (BC) comprises multiple distinct subtypes that differ genetically, pathologically, and clinically. Here, we describe a robust protocol for long-term culturing of human mammary epithelial organoids. Using this protocol, >100 primary and metastatic BC organoid lines were generated, broadly recapitulating the diversity of the disease. BC organoid morphologies typically matched the histopathology, hormone receptor status, and HER2 status of the original tumor. DNA copy number variations as well as sequence changes were consistent within tumor-organoid pairs and largely retained even after extended passaging. BC organoids furthermore populated all major gene-expression-based classification groups and allowed in vitro drug screens that were consistent with in vivo xeno-transplantations and patient response. This study describes a representative collection of well-characterized BC organoids available for cancer research and drug development, as well as a strategy to assess in vitro drug response in a personalized fashion.
Assuntos
Neoplasias da Mama/patologia , Heterogeneidade Genética , Organoides/patologia , Bancos de Tecidos , Animais , Antineoplásicos/farmacologia , Neoplasias da Mama/genética , Células Cultivadas , Ensaios de Seleção de Medicamentos Antitumorais/métodos , Feminino , Humanos , Camundongos , Camundongos Nus , Organoides/efeitos dos fármacos , Medicina de Precisão/métodosRESUMO
During kidney development, progressively committed progenitor cells give rise to the distinct segments of the nephron, the functional unit of the kidney. Similar segment-committed progenitor cells are thought to be involved in the homeostasis of adult kidney. However, markers for most segment-committed progenitor cells remain to be identified. Here, we evaluate Troy/TNFRSF19 as a segment-committed nephron progenitor cell marker. Troy is expressed in the ureteric bud during embryonic development. During postnatal nephrogenesis, Troy+ cells are present in the cortex and papilla and display an immature tubular phenotype. Tracing of Troy+ cells during nephrogenesis demonstrates that Troy+ cells clonally give rise to tubular structures that persist for up to 2 y after induction. Troy+ cells have a 40-fold higher capacity than Troy- cells to form organoids, which is considered a stem cell property in vitro. In the adult kidney, Troy+ cells are present in the papilla and these cells continue to contribute to collecting duct formation during homeostasis. The number of Troy-derived cells increases after folic acid-induced injury. Our data show that Troy marks a renal stem/progenitor cell population in the developing kidney that in adult kidney contributes to homeostasis, predominantly of the collecting duct, and regeneration.
Assuntos
Células Epiteliais/metabolismo , Néfrons/embriologia , Organogênese/fisiologia , Receptores do Fator de Necrose Tumoral/metabolismo , Células-Tronco/metabolismo , Animais , Camundongos , Camundongos Transgênicos , Receptores do Fator de Necrose Tumoral/genéticaRESUMO
Mutational processes underlie cancer initiation and progression. Signatures of these processes in cancer genomes may explain cancer etiology and could hold diagnostic and prognostic value. We developed a strategy that can be used to explore the origin of cancer-associated mutational signatures. We used CRISPR-Cas9 technology to delete key DNA repair genes in human colon organoids, followed by delayed subcloning and whole-genome sequencing. We found that mutation accumulation in organoids deficient in the mismatch repair gene MLH1 is driven by replication errors and accurately models the mutation profiles observed in mismatch repair-deficient colorectal cancers. Application of this strategy to the cancer predisposition gene NTHL1, which encodes a base excision repair protein, revealed a mutational footprint (signature 30) previously observed in a breast cancer cohort. We show that signature 30 can arise from germline NTHL1 mutations.
Assuntos
Sistemas CRISPR-Cas , Colo , Desoxirribonuclease (Dímero de Pirimidina)/genética , Proteína 1 Homóloga a MutL/genética , Neoplasias/genética , Organoides , Neoplasias da Mama/genética , Neoplasias Colorretais/genética , Reparo de Erro de Pareamento de DNA/genética , Reparo do DNA/genética , Replicação do DNA , Feminino , Mutação em Linhagem Germinativa , Humanos , Mutação INDEL , Mutagênese , Células-TroncoRESUMO
The gradual accumulation of genetic mutations in human adult stem cells (ASCs) during life is associated with various age-related diseases, including cancer. Extreme variation in cancer risk across tissues was recently proposed to depend on the lifetime number of ASC divisions, owing to unavoidable random mutations that arise during DNA replication. However, the rates and patterns of mutations in normal ASCs remain unknown. Here we determine genome-wide mutation patterns in ASCs of the small intestine, colon and liver of human donors with ages ranging from 3 to 87 years by sequencing clonal organoid cultures derived from primary multipotent cells. Our results show that mutations accumulate steadily over time in all of the assessed tissue types, at a rate of approximately 40 novel mutations per year, despite the large variation in cancer incidence among these tissues. Liver ASCs, however, have different mutation spectra compared to those of the colon and small intestine. Mutational signature analysis reveals that this difference can be attributed to spontaneous deamination of methylated cytosine residues in the colon and small intestine, probably reflecting their high ASC division rate. In liver, a signature with an as-yet-unknown underlying mechanism is predominant. Mutation spectra of driver genes in cancer show high similarity to the tissue-specific ASC mutation spectra, suggesting that intrinsic mutational processes in ASCs can initiate tumorigenesis. Notably, the inter-individual variation in mutation rate and spectra are low, suggesting tissue-specific activity of common mutational processes throughout life.
Assuntos
Células-Tronco Adultas/metabolismo , Envelhecimento/genética , Acúmulo de Mutações , Taxa de Mutação , Especificidade de Órgãos , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Criança , Pré-Escolar , Colo/metabolismo , Análise Mutacional de DNA , Feminino , Genes Neoplásicos/genética , Humanos , Incidência , Intestino Delgado/metabolismo , Fígado/metabolismo , Masculino , Camundongos , Pessoa de Meia-Idade , Células-Tronco Multipotentes/metabolismo , Neoplasias/epidemiologia , Neoplasias/genética , Organoides/metabolismo , Mutação Puntual/genética , Adulto JovemRESUMO
The rat is an important model for liver regeneration. However, there is no in vitro culture system that can capture the massive proliferation that can be observed after partial hepatectomy in rats. We here describe the generation of rat liver stem cell lines. Rat liver stem cells, which grow as cystic organoids, were characterized by high expression of the stem cell marker Lgr5, by the expression of liver progenitor and duct markers, and by low expression of hepatocyte markers, oval cell markers, and stellate cell markers. Prolonged cultures of rat liver organoids depended on high levels of WNT-signalling and the inhibition of BMP-signaling. Upon transplantation of clonal lines to a Fah(-/-) Il2rg(-/-) rat model of liver failure, the rat liver stem cells engrafted into the host liver where they differentiated into areas with FAH and Albumin positive hepatocytes. Rat liver stem cell lines hold potential as consistent reliable cell sources for pharmacological, toxicological or metabolic studies. In addition, rat liver stem cell lines may contribute to the development of regenerative medicine in liver disease. To our knowledge, the here described liver stem cell lines represent the first organoid culture system in the rat.
Assuntos
Hepatócitos/metabolismo , Hepatócitos/transplante , Falência Hepática/terapia , Regeneração Hepática/fisiologia , Transplante de Células-Tronco , Células-Tronco/citologia , Animais , Biomarcadores/metabolismo , Proteínas de Transporte/farmacologia , Técnicas de Cultura de Células , Diferenciação Celular/fisiologia , Proliferação de Células , Células Cultivadas , Hidrolases/deficiência , Hidrolases/genética , Subunidade gama Comum de Receptores de Interleucina/deficiência , Subunidade gama Comum de Receptores de Interleucina/genética , Fígado/citologia , Falência Hepática/patologia , Transplante de Fígado , Ratos , Ratos Transgênicos , Proteína Wnt3A/farmacologiaRESUMO
Despite the enormous replication potential of the human liver, there are currently no culture systems available that sustain hepatocyte replication and/or function in vitro. We have shown previously that single mouse Lgr5+ liver stem cells can be expanded as epithelial organoids in vitro and can be differentiated into functional hepatocytes in vitro and in vivo. We now describe conditions allowing long-term expansion of adult bile duct-derived bipotent progenitor cells from human liver. The expanded cells are highly stable at the chromosome and structural level, while single base changes occur at very low rates. The cells can readily be converted into functional hepatocytes in vitro and upon transplantation in vivo. Organoids from α1-antitrypsin deficiency and Alagille syndrome patients mirror the in vivo pathology. Clonal long-term expansion of primary adult liver stem cells opens up experimental avenues for disease modeling, toxicology studies, regenerative medicine, and gene therapy.