Probabilistic pathway-based multimodal factor analysis.

MOTIVATION: Multimodal profiling strategies promise to produce more informative insights into biomedical cohorts via the integration of the information each modality contributes. To perform this integration, however, the development of novel analytical strategies is needed. Multimodal profiling strategies often come at the expense of lower sample numbers, which can challenge methods to uncover shared signals across a cohort. Thus, factor analysis approaches are commonly used for the analysis of high-dimensional data in molecular biology, however, they typically do not yield representations that are directly interpretable, whereas many research questions often center around the analysis of pathways associated with specific observations. RESULTS: We develop PathFA, a novel approach for multimodal factor analysis over the space of pathways. PathFA produces integrative and interpretable views across multimodal profiling technologies, which allow for the derivation of concrete hypotheses. PathFA combines a pathway-learning approach with integrative multimodal capability under a Bayesian procedure that is efficient, hyper-parameter free, and able to automatically infer observation noise from the data. We demonstrate strong performance on small sample sizes within our simulation framework and on matched proteomics and transcriptomics profiles from real tumor samples taken from the Swiss Tumor Profiler consortium. On a subcohort of melanoma patients, PathFA recovers pathway activity that has been independently associated with poor outcome. We further demonstrate the ability of this approach to identify pathways associated with the presence of specific cell-types as well as tumor heterogeneity. Our results show that we capture known biology, making it well suited for analyzing multimodal sample cohorts. AVAILABILITY AND IMPLEMENTATION: The tool is implemented in python and available at https://github.com/ratschlab/path-fa.

Mutant SF3B1 promotes malignancy in PDAC.

The splicing factor SF3B1 is recurrently mutated in various tumors, including pancreatic ductal adenocarcinoma (PDAC). The impact of the hotspot mutation SF3B1K700E on the PDAC pathogenesis, however, remains elusive. Here, we demonstrate that Sf3b1K700E alone is insufficient to induce malignant transformation of the murine pancreas, but that it increases aggressiveness of PDAC if it co-occurs with mutated KRAS and p53. We further show that Sf3b1K700E already plays a role during early stages of pancreatic tumor progression and reduces the expression of TGF-ß1-responsive epithelial-mesenchymal transition (EMT) genes. Moreover, we found that SF3B1K700E confers resistance to TGF-ß1-induced cell death in pancreatic organoids and cell lines, partly mediated through aberrant splicing of Map3k7. Overall, our findings demonstrate that SF3B1K700E acts as an oncogenic driver in PDAC, and suggest that it promotes the progression of early stage tumors by impeding the cellular response to tumor suppressive effects of TGF-ß.

Mutation Rates in Cancer Susceptibility Genes in Patients With Breast Cancer With Multiple Primary Cancers.

PURPOSE: Women with breast cancer have a 4%-16% lifetime risk of a second primary cancer. Whether mutations in genes other than BRCA1/2 are enriched in patients with breast and another primary cancer over those with a single breast cancer (S-BC) is unknown. PATIENTS AND METHODS: We identified pathogenic germline mutations in 17 cancer susceptibility genes in patients with BRCA1/2-negative breast cancer in 2 different cohorts: cohort 1, high-risk breast cancer program (multiple primary breast cancer [MP-BC], n = 551; S-BC, n = 449) and cohort 2, familial breast cancer research study (MP-BC, n = 340; S-BC, n = 1,464). Mutation rates in these 2 cohorts were compared with a control data set (Exome Aggregation Consortium [ExAC]). RESULTS: Overall, pathogenic mutation rates for autosomal, dominantly inherited genes were higher in patients with MP-BC versus S-BC in both cohorts (8.5% v 4.9% [P = .02] and 7.1% v 4.2% [P = .03]). There were differences in individual gene mutation rates between cohorts. In both cohorts, younger age at first breast cancer was associated with higher mutation rates; the age of non-breast cancers was unrelated to mutation rate. TP53 and MSH6 mutations were significantly enriched in patients with MP-BC but not S-BC, whereas ATM and PALB2 mutations were significantly enriched in both groups compared with ExAC. CONCLUSION: Mutation rates are at least 7% in all patients with BRCA1/2 mutation-negative MP-BC, regardless of age at diagnosis of breast cancer, with mutation rates up to 25% in patients with a first breast cancer diagnosed at age < 30 years. Our results suggest that all patients with breast cancer with a second primary cancer, regardless of age of onset, should undergo multigene panel testing.

Case-control analysis identifies shared properties of rare germline variation in cancer predisposing genes.

Along with traditional effects of aging and carcinogen exposure-inherited DNA variation has substantial contribution to cancer risk. Extraordinary progress made in analysis of common variation with GWAS methodology does not provide sufficient resolution to understand rare variation. To fulfill missing classification for rare germline variation we assembled dataset of whole exome sequences from>2000 patients (selected cases tested negative for candidate genes and unselected cases) with different types of cancers (breast cancer, colon cancer, and cutaneous and ocular melanomas) matched to more than 7000 non-cancer controls and analyzed germline variation in known cancer predisposing genes to identify common properties of disease-associated DNA variation and aid the future searches for new cancer susceptibility genes. Cancer predisposing genes were divided into non-overlapping classes according to the mode of inheritance of the related cancer syndrome or known tumor suppressor activity. Out of all classes only genes linked to dominant syndromes presented significant rare germline variants enrichment in cases. Separate analysis of protein-truncating and missense variation in this list of genes confirmed significant prevalence of protein-truncating variants in cases only in loss-of-function tolerant genes (pLI < 0.1), while ultra-rare missense variants were significantly overrepresented in cases only in constrained genes (pLI > 0.9). In addition to findings in genetically enriched cases, we observed significant burden of rare variation in unselected cases, suggesting substantial role of inherited variation even in relatively late cancer manifestation. Taken together, our findings provide reference for distribution and types of DNA variation underlying inherited predisposition to some common cancer types.

Erratum: Author Correction: The contribution of pathogenic variants in breast cancer susceptibility genes to familial breast cancer risk.

[This corrects the article DOI: 10.1038/s41523-017-0024-8.].

The contribution of pathogenic variants in breast cancer susceptibility genes to familial breast cancer risk.

Understanding the gene-specific risks for development of breast cancer will lead to improved clinical care for those carrying germline mutations in cancer predisposition genes. We sought to detail the spectrum of mutations and refine risk estimates for known and proposed breast cancer susceptibility genes. Targeted massively-parallel sequencing was performed to identify mutations and copy number variants in 26 known or proposed breast cancer susceptibility genes in 2134 BRCA1/2-negative women with familial breast cancer (proband with breast cancer and a family history of breast or ovarian cancer) from a largely European-Caucasian multi-institutional cohort. Case-control analysis was performed comparing the frequency of internally classified mutations identified in familial breast cancer women to Exome Aggregation Consortium controls. Mutations were identified in 8.2% of familial breast cancer women, including mutations in high-risk (odds ratio > 5) (1.4%) and moderate-risk genes (2 < odds ratio < 5) (2.9%). The remaining familial breast cancer women had mutations in proposed breast cancer genes (1.7%), Lynch syndrome genes (0.5%), and six cases had two mutations (0.3%). Case-control analysis demonstrated associations with familial breast cancer for ATM, PALB2, and TP53 mutations (odds ratio > 3.0, p < 10-4), BARD1 mutations (odds ratio = 3.2, p = 0.012), and CHEK2 truncating mutations (odds ratio = 1.6, p = 0.041). Our results demonstrate that approximately 4.7% of BRCA1/2 negative familial breast cancer women have mutations in genes statistically associated with breast cancer. We classified PALB2 and TP53 as high-risk, ATM and BARD1 as moderate risk, and CHEK2 truncating mutations as low risk breast cancer predisposition genes. This study demonstrates that large case-control studies are needed to fully evaluate the breast cancer risks associated with mutations in moderate-risk and proposed susceptibility genes.

A Recurrent ERCC3 Truncating Mutation Confers Moderate Risk for Breast Cancer.

Known gene mutations account for approximately 50% of the hereditary risk for breast cancer. Moderate and low penetrance variants, discovered by genomic approaches, account for an as-yet-unknown proportion of the remaining heritability. A truncating mutation c.325C>T:p.Arg109* (R109X) in the ATP-dependent helicase ERCC3 was observed recurrently among exomes sequenced in BRCA wild-type, breast cancer-affected individuals of Ashkenazi Jewish ancestry. Modeling of the mutation in ERCC3-deficient or CRISPR/Cas9-edited cell lines showed a consistent pattern of reduced expression of the protein and concomitant hypomorphic functionality when challenged with UVC exposure or treatment with the DNA alkylating agent IlludinS. Overexpressing the mutant protein in ERCC3-deficient cells only partially rescued their DNA repair-deficient phenotype. Comparison of frequency of this recurrent mutation in over 6,500 chromosomes of breast cancer cases and 6,800 Ashkenazi controls showed significant association with breast cancer risk (ORBC = 1.53, ORER+ = 1.73), particularly for the estrogen receptor-positive subset (P < 0.007). SIGNIFICANCE: A functionally significant recurrent ERCC3 mutation increased the risk for breast cancer in a genetic isolate. Mutated cell lines showed lower survival after in vitro exposure to DNA-damaging agents. Thus, similar to tumors arising in the background of homologous repair defects, mutations in nucleotide excision repair genes such as ERCC3 could constitute potential therapeutic targets in a subset of hereditary breast cancers. Cancer Discov; 6(11); 1267-75. ©2016 AACR.This article is highlighted in the In This Issue feature, p. 1197.

Evaluation of ACMG-Guideline-Based Variant Classification of Cancer Susceptibility and Non-Cancer-Associated Genes in Families Affected by Breast Cancer.

Sequencing tests assaying panels of genes or whole exomes are widely available for cancer risk evaluation. However, methods for classification of variants resulting from this testing are not well studied. We evaluated the ability of a variant-classification methodology based on American College of Medical Genetics and Genomics (ACMG) guidelines to define the rate of mutations and variants of uncertain significance (VUS) in 180 medically relevant genes, including all ACMG-designated reportable cancer and non-cancer-associated genes, in individuals who met guidelines for hereditary cancer risk evaluation. We performed whole-exome sequencing in 404 individuals in 253 families and classified 1,640 variants. Potentially clinically actionable (likely pathogenic [LP] or pathogenic [P]) versus nonactionable (VUS, likely benign, or benign) calls were 95% concordant with locus-specific databases and Clinvar. LP or P mutations were identified in 12 of 25 breast cancer susceptibility genes in 26 families without identified BRCA1/2 mutations (11%). Evaluation of 84 additional genes associated with autosomal-dominant cancer susceptibility identified LP or P mutations in only two additional families (0.8%). However, individuals from 10 of 253 families (3.9%) had incidental LP or P mutations in 32 non-cancer-associated genes, and 9% of individuals were monoallelic carriers of a rare LP or P mutation in 39 genes associated with autosomal-recessive cancer susceptibility. Furthermore, 95% of individuals had at least one VUS. In summary, these data support the clinical utility of ACMG variant-classification guidelines. Additionally, evaluation of extended panels of cancer-associated genes in breast/ovarian cancer families leads to only an incremental clinical benefit but substantially increases the complexity of the results.

Germline Variants in Targeted Tumor Sequencing Using Matched Normal DNA.

IMPORTANCE: Tumor genetic sequencing identifies potentially targetable genetic alterations with therapeutic implications. Analysis has concentrated on detecting tumor-specific variants, but recognition of germline variants may prove valuable as well. OBJECTIVE: To estimate the burden of germline variants identified through routine clinical tumor sequencing. DESIGN, SETTING, AND PARTICIPANTS: Patients with advanced cancer diagnoses eligible for studies of targeted agents at Memorial Sloan Kettering Cancer Center are offered tumor-normal sequencing with MSK-IMPACT, a 341-gene panel. We surveyed the germline variants seen in 187 overlapping genes with Mendelian disease associations in 1566 patients who had undergone tumor profiling between March and October 2014. MAIN OUTCOMES AND MEASURES: The number of presumed pathogenic germline variants (PPGVs) and variants of uncertain significance per person in 187 genes associated with single-gene disorders and the proportions of individuals with PPGVs in clinically relevant gene subsets, in genes consistent with known tumor phenotypes, and in genes with evidence of second somatic hits in their tumors. RESULTS: The mean age of the 1566 patients was 58 years, and 54% were women. Presumed pathogenic germline variants in known Mendelian disease-associated genes were identified in 246 of 1566 patients (15.7%; 95% CI, 14.0%-17.6%), including 198 individuals with mutations in genes associated with cancer susceptibility. Germline findings in cancer susceptibility genes were concordant with the individual's cancer type in only 81 of 198 cases (40.9%; 95% CI, 34.3%-47.9%). In individuals with PPGVs retained in the tumor, somatic alteration of the other allele was seen in 39 of 182 cases (21.4%; 95% CI, 16.1%-28.0%), of which 13 cases did not show a known correlation of the germline mutation and a known syndrome. Mutations in non-cancer-related Mendelian disease genes were seen in 55 of 1566 cases (3.5%; 95% CI, 27.1%-45.4%). Almost every individual had more than 1 variant of uncertain significance (1565 of 1566 patients; 99.9%; 95% CI, 99.6%-99.9%). CONCLUSIONS AND RELEVANCE: Germline variants are common in individuals undergoing tumor-normal sequencing and may reveal otherwise unsuspected syndromic associations.

Collaborative science in the next-generation sequencing era: a viewpoint on how to combine exome sequencing data across sites to identify novel disease susceptibility genes.

The purpose of this article is to inform readers about technical challenges that we encountered when assembling exome sequencing data from the 'Simplifying Complex Exomes' (SIMPLEXO) consortium-whose mandate is the discovery of novel genes predisposing to breast and ovarian cancers. Our motivation is to share these obstacles-and our solutions to them-as a means of communicating important technical details that should be discussed early in projects involving massively parallel sequencing.