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- Ali, Muhammad Akhtar
(author)
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Understanding Cancer Mutations by Genome Editing
- 2014
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Doctoral thesis (other academic/artistic)abstract
- Mutational analyses of cancer genomes have identified novel candidate cancer genes with hitherto unknown function in cancer. To enable phenotyping of mutations in such genes, we have developed a scalable technology for gene knock-in and knock-out in human somatic cells based on recombination-mediated construct generation and a computational tool to design gene targeting constructs. Using this technology, we have generated somatic cell knock-outs of the putative cancer genes ZBED6 and DIP2C in human colorectal cancer cells. In ZBED6-/- cells complete loss of functional ZBED6 was validated and loss of ZBED6 induced the expression of IGF2. Whole transcriptome and ChIP-seq analyses revealed relative enrichment of ZBED6 binding sites at upregulated genes as compared to downregulated genes. The functional annotation of differentially expressed genes revealed enrichment of genes related to cell cycle and cell proliferation and the transcriptional modulator ZBED6 affected the cell growth and cell cycle of human colorectal cancer cells. In DIP2C-/-cells, transcriptome sequencing revealed 780 differentially expressed genes as compared to their parental cells including the tumour suppressor gene CDKN2A. The DIP2C regulated genes belonged to several cancer related processes such as angiogenesis, cell structure and motility. The DIP2C-/-cells were enlarged and grew slower than their parental cells. To be able to directly compare the phenotypes of mutant KRAS and BRAF in colorectal cancers, we have introduced a KRASG13D allele in RKO BRAFV600E/-/-/ cells. The expression of the mutant KRAS allele was confirmed and anchorage independent growth was restored in KRASG13D cells. The differentially expressed genes both in BRAF and KRAS mutant cells included ERBB, TGFB and histone modification pathways. Together, the isogenic model systems presented here can provide insights to known and novel cancer pathways and can be used for drug discovery.
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- Carlsson, Jonas, et al.
(author)
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Investigation and prediction of the severity of p53 mutants using parameters from structural calculations
- 2009
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In: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 276:15, s. 4142-4155
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Journal article (peer-reviewed)abstract
- A method has been developed to predict the effects of mutations in the p53 cancer suppressor gene. The new method uses novel parameters combined with previously established parameters. The most important parameter is the stability measure of the mutated structure calculated using molecular modelling. For each mutant, a severity score is reported, which can be used for classification into deleterious and nondeleterious. Both structural features and sequence properties are taken into account. The method has a prediction accuracy of 77% on all mutants and 88% on breast cancer mutations affecting WAF1 promoter binding. When compared with earlier methods, using the same dataset, our method clearly performs better. As a result of the severity score calculated for every mutant, valuable knowledge can be gained regarding p53, a protein that is believed to be involved in over 50% of all human cancers.
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- Doffe, Flora, et al.
(author)
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Identification and functional characterization of new missense SNPs in the coding region of the TP53 gene
- 2021
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In: Cell Death and Differentiation. - : Springer Science and Business Media LLC. - 1350-9047 .- 1476-5403. ; 28:5, s. 1477-1492
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Journal article (peer-reviewed)abstract
- Infrequent and rare genetic variants in the human population vastly outnumber common ones. Although they may contribute significantly to the genetic basis of a disease, these seldom-encountered variants may also be miss-identified as pathogenic if no correct references are available. Somatic and germline TP53 variants are associated with multiple neoplastic diseases, and thus have come to serve as a paradigm for genetic analyses in this setting. We searched 14 independent, globally distributed datasets and recovered TP53 SNPs from 202,767 cancer-free individuals. In our analyses, 19 new missense TP53 SNPs, including five novel variants specific to the Asian population, were recurrently identified in multiple datasets. Using a combination of in silico, functional, structural, and genetic approaches, we showed that none of these variants displayed loss of function compared to the normal TP53 gene. In addition, classification using ACMG criteria suggested that they are all benign. Considered together, our data reveal that the TP53 coding region shows far more polymorphism than previously thought and present high ethnic diversity. They furthermore underline the importance of correctly assessing novel variants in all variant-calling pipelines associated with genetic diagnoses for cancer.
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- Edlund, Karolina, et al.
(author)
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Data-driven unbiased curation of the TP53 tumor suppressor gene mutation database and validation by ultradeep sequencing of human tumors
- 2012
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 109:24, s. 9551-9556
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Journal article (peer-reviewed)abstract
- Cancer mutation databases are expected to play central roles in personalized medicine by providing targets for drug development and biomarkers to tailor treatments to each patient. The accuracy of reported mutations is a critical issue that is commonly overlooked, which leads to mutation databases that include a sizable number of spurious mutations, either sequencing errors or passenger mutations. Here we report an analysis of the latest version of the TP53 mutation database, including 34,453 mutations. By using several data-driven methods on multiple independent quality criteria, we obtained a quality score for each report contributing to the database. This score can now be used to filter for high-confidence mutations and reports within the database. Sequencing the entire TP53 gene from various types of cancer using next-generation sequencing with ultradeep coverage validated our approach for curation. In summary, 9.7% of all collected studies, mostly comprising numerous tumors with multiple infrequent TP53 mutations, should be excluded when analyzing TP53 mutations. Thus, by combining statistical and experimental analyses, we provide a curated mutation database for TP53 mutations and a framework for mutation database analysis.
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- Lazarian, Gregory, et al.
(author)
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The Broad Spectrum of TP53 Mutations in CLL : Evidence of Multiclonality and Novel Mutation Hotspots
- 2023
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In: Human Mutation. - : Hindawi Limited. - 1059-7794 .- 1098-1004. ; 2023
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Journal article (peer-reviewed)abstract
- TP53 aberrations are a major predictive factor of resistance to chemoimmunotherapy in chronic lymphocytic leukemia (CLL), and an assessment of them before each line of treatment is required for theranostic stratification. Acquisition of subclonal TP53 abnormalities underlies the evolution of CLL. To better characterize the distribution, combination, and impact of TP53 variants in CLL, 1,056 TP53 variants collected from 683 patients included in a multicenter collaborative study in France were analyzed and compared to UMD_CLL, a dataset built from published articles collectively providing 5,173 TP53 variants detected in 3,808 patients. Our analysis confirmed the presence of several CLL-specific hotspot mutations, including a two-base pair deletion in codon 209 and a missense variant at codon 234, the latter being associated with alkylating treatment. Our analysis also identified a novel CLL-specific variant in the splice acceptor signal of intron 6 leading to the use of a cryptic splice site, similarly utilized by TP53 to generate p53psi, a naturally truncated p53 isoform localized in the mitochondria. Examination of both UMD_CLL and several recently released large-scale genomic analyses of CLL patients confirmed that this splice variant is highly enriched in this disease when compared to other cancer types. Using a TP53-specific single-nucleotide polymorphism, we also confirmed that copy-neutral loss of heterozygosity is frequent in CLL. This event can lead to misinterpretation of TP53 status. Unlike other cancers, CLL displayed a high proportion of patients harboring multiple TP53 variants. Using both in silico analysis and single molecule smart sequencing, we demonstrated the coexistence of distinct subclones harboring mutations on distinct alleles. In summary, our study provides a detailed TP53 mutational architecture in CLL and gives insights into how treatments may shape the genetic landscape of CLL patients.
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- Matas, Julia, et al.
(author)
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Colorectal Cancer Is Associated with the Presence of Cancer Driver Mutations in Normal Colon
- 2022
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In: Cancer Research. - : American Association for Cancer Research (AACR). - 0008-5472 .- 1538-7445. ; 82:8, s. 1492-1502
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Journal article (peer-reviewed)abstract
- Although somatic mutations in colorectal cancer are well characterized, little is known about the accumulation of cancer mutations in the normal colon before cancer. Here, we have developed and applied an ultrasensitive, single-molecule mutational test based on CRISPR-DS technology, which enables mutation detection at extremely low frequency (< 0.001) in normal colon from patients with and without colorectal cancer. This testing platform revealed that normal colon from patients with and without colorectal cancer carries mutations in common colorectal cancer genes, but these mutations are more abundant in patients with cancer. Oncogenic KRAS mutations were observed in the normal colon of about one third of patients with colorectal cancer but in none of the patients without colorectal cancer. Patients with colorectal cancer also carried more TP53 mutations than patients without cancer and these mutations were more pathogenic and formed larger clones, especially in patients with early-onset colorectal cancer. Most mutations in the normal colon were different from the driver mutations in tumors, suggesting that the occurrence of independent clones with pathogenic KRAS and TP53 mutations is a common event in the colon of individuals who develop colorectal cancer. These results indicate that somatic evolution contributes to clonal expansions in the normal colon and that this process is enhanced in individuals with cancer, particularly in those with early-onset colorectal cancer. Significance: This work suggests prevalent somatic evolution in the normal colon of patients with colorectal cancer, highlighting the potential of using ultrasensitive gene sequencing to predict disease risk. [GRAPHICS]
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