29 research outputs found
Whole-exome sequencing of circulating tumor cells provides a window into metastatic prostate cancer
Comprehensive analyses of cancer genomes promise to inform prognoses and precise cancer treatments. A major barrier, however, is inaccessibility of metastatic tissue. A potential solution is to characterize circulating tumor cells (CTCs), but this requires overcoming the challenges of isolating rare cells and sequencing low-input material. Here we report an integrated process to isolate, qualify and sequence whole exomes of CTCs with high fidelity using a census-based sequencing strategy. Power calculations suggest that mapping of >99.995% of the standard exome is possible in CTCs. We validated our process in two patients with prostate cancer, including one for whom we sequenced CTCs, a lymph node metastasis and nine cores of the primary tumor. Fifty-one of 73 CTC mutations (70%) were present in matched tissue. Moreover, we identified 10 early trunk and 56 metastatic trunk mutations in the non-CTC tumor samples and found 90% and 73% of these mutations, respectively, in CTC exomes. This study establishes a foundation for CTC genomics in the clinic.National Science Foundation (U.S.). Graduate Research FellowshipNational Cancer Institute (U.S.) (Koch Institute Support (Core) Grant P30-CA14051)Janssen Pharmaceutical Ltd.Klarman Family Foundatio
Calibrating genomic and allelic coverage bias in single-cell sequencing
Artifacts introduced in whole-genome amplification (WGA) make it difficult to derive accurate genomic information from single-cell genomes and require different analytical strategies from bulk genome analysis. Here, we describe statistical methods to quantitatively assess the amplification bias resulting from whole-genome amplification of single-cell genomic DNA. Analysis of single-cell DNA libraries generated by different technologies revealed universal features of the genome coverage bias predominantly generated at the amplicon level (1–10 kb). The magnitude of coverage bias can be accurately calibrated from low-pass sequencing (∼0.1 × ) to predict the depth-of-coverage yield of single-cell DNA libraries sequenced at arbitrary depths. We further provide a benchmark comparison of single-cell libraries generated by multi-strand displacement amplification (MDA) and multiple annealing and looping-based amplification cycles (MALBAC). Finally, we develop statistical models to calibrate allelic bias in single-cell whole-genome amplification and demonstrate a census-based strategy for efficient and accurate variant detection from low-input biopsy samples.National Cancer Institute (U.S.) (Grant P30-CA14051
Single cells from human primary colorectal tumors exhibit polyfunctional heterogeneity in secretions of ELR+ CXC chemokines
Cancer is an inflammatory disease of tissue that is largely influenced by the interactions between multiple cell types, secreted factors, and signal transduction pathways. While single-cell sequencing continues to refine our understanding of the clonotypic heterogeneity within tumors, the complex interplay between genetic variations and non-genetic factors ultimately affects therapeutic outcome. Much has been learned through bulk studies of secreted factors in the tumor microenvironment, but the secretory behavior of single cells has been largely uncharacterized. Here we directly profiled the secretions of ELR+ CXC chemokines from thousands of single colorectal tumor and stromal cells, using an array of subnanoliter wells and a technique called microengraving to characterize both the rates of secretion of several factors at once and the numbers of cells secreting each chemokine. The ELR+ CXC chemokines are highly redundant, pro-angiogenic cytokines that signal via the CXCR1 and CXCR2 receptors, influencing tumor growth and progression. We find that human primary colorectal tumor and stromal cells exhibit polyfunctional heterogeneity in the combinations and magnitudes of secretions for these chemokines. In cell lines, we observe similar variance: phenotypes observed in bulk can be largely absent among the majority of single cells, and discordances exist between secretory states measured and gene expression for these chemokines among single cells. Together, these measures suggest secretory states among tumor cells are complex and can evolve dynamically. Most importantly, this study reveals new insight into the intratumoral phenotypic heterogeneity of human primary tumors.Janssen Pharmaceutical Ltd.National Cancer Institute (U.S.) (Cancer Center Support (Core) Grant P30-CA14051)National Science Foundation (U.S.). Graduate Research FellowshipSingapore. Agency for Science, Technology and ResearchSwiss National Science Foundation (Fellowship for Advanced Researchers PA00P3 139659
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Whole exome sequencing of circulating tumor cells provides a window into metastatic prostate cancer
Comprehensive analyses of cancer genomes promise to inform prognoses and precise cancer treatments. A major barrier, however, is inaccessibility of metastatic tissue. A potential solution is to characterize circulating tumor cells (CTCs), but this requires overcoming the challenges of isolating rare cells and sequencing low-input material. Here we report an integrated process to isolate, qualify and sequence whole exomes of CTCs with high fidelity, using a census-based sequencing strategy. Power calculations suggest that mapping of >99.995% of the standard exome is possible in CTCs. We validated our process in two prostate cancer patients including one for whom we sequenced CTCs, a lymph node metastasis and nine cores of the primary tumor. Fifty-one of 73 CTC mutations (70%) were observed in matched tissue. Moreover, we identified 10 early-trunk and 56 metastatic-trunk mutations in the non-CTC tumor samples and found 90% and 73% of these, respectively, in CTC exomes. This study establishes a foundation for CTC genomics in the clinic
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Resistance to checkpoint blockade therapy through inactivation of antigen presentation
Treatment with immune checkpoint blockade (CPB) therapies often leads to prolonged responses in patients with metastatic melanoma, but the common mechanisms of primary and acquired resistance to these agents remain incompletely characterized and have yet to be validated in large cohorts. By analyzing longitudinal tumor biopsies from 17 metastatic melanoma patients treated with CPB therapies, we observed point mutations, deletions or loss of heterozygosity (LOH) in beta-2-microglobulin (B2M), an essential component of MHC class I antigen presentation, in 29.4% of patients with progressing disease. In two independent cohorts of melanoma patients treated with anti-CTLA4 and anti-PD1, respectively, we find that B2M LOH is enriched threefold in non-responders (~30%) compared to responders (~10%) and associated with poorer overall survival. Loss of both copies of B2M is found only in non-responders. B2M loss is likely a common mechanism of resistance to therapies targeting CTLA4 or PD1
The Mutational Landscape of Circulating Tumor Cells in Multiple Myeloma
The development of sensitive and non-invasive
‘‘liquid biopsies’’ presents new opportunities for
longitudinal monitoring of tumor dissemination and
clonal evolution. The number of circulating tumor
cells (CTCs) is prognostic in multiple myeloma
(MM), but there is little information on their genetic
features. Here, we have analyzed the genomic landscape
of CTCs from 29 MM patients, including eight
cases with matched/paired bone marrow (BM) tumor
cells. Our results show that 100% of clonal mutations
in patient BM were detected in CTCs and that 99% of
clonal mutations in CTCs were present in BM MM.
These include typical driver mutations in MM such
as in KRAS, NRAS, or BRAF. These data suggest
that BM and CTC samples have similar clonal structures,
as discordances between the two were
restricted to subclonal mutations. Accordingly, our
results pave the way for potentially less invasive
mutation screening of MM patients through characterization
of CTCs
Scalable whole-exome sequencing of cell-free DNA reveals high concordance with metastatic tumors
Whole-exome sequencing of cell-free DNA (cfDNA) could enable comprehensive profiling of tumors from blood but the genome-wide concordance between cfDNA and tumor biopsies is uncertain. Here we report ichorCNA, software that quantifies tumor content in cfDNA from 0.1× coverage whole-genome sequencing data without prior knowledge of tumor mutations. We apply ichorCNA to 1439 blood samples from 520 patients with metastatic prostate or breast cancers. In the earliest tested sample for each patient, 34% of patients have ≥10% tumor-derived cfDNA, sufficient for standard coverage whole-exome sequencing. Using whole-exome sequencing, we validate the concordance of clonal somatic mutations (88%), copy number alterations (80%), mutational signatures, and neoantigens between cfDNA and matched tumor biopsies from 41 patients with ≥10% cfDNA tumor content. In summary, we provide methods to identify patients eligible for comprehensive cfDNA profiling, revealing its applicability to many patients, and demonstrate high concordance of cfDNA and metastatic tumor whole-exome sequencing
Genome sequencing and phenotypic analysis of single cells in cancer
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2015.Cataloged from PDF version of thesis.Includes bibliographical references.Relatively little is known about metastatic cancer. The vast majority of cancer genome profiling (~99%) is done on primary tumors; yet, metastatic cancer is attributed to >90% of cancer-related deaths. The underlying challenge is that metastatic cancer is difficult to sample: surgical resections are less common, metastatic biopsies are not part of clinical routine, and such invasive biopsies are not a repeated solution. In the first half of my thesis, I describe our advances in unlocking comprehensive sequencing of metastatic cancer from blood. We demonstrate that confident and powered sequencing of all genes in the human genome from single circulating tumor cells (CTCs) is both possible and useful clinically. We also describe a statistical framework for evaluating amplification bias in single-cell sequencing and two new methods for enriching CTCs from blood. In the second half of my thesis, I present our advances in characterizing the phenotypic behavior of single cells in cancer. We examine the polyfunctional heterogeneity in secretions of ELR+ CXC chemokines from single tumor and stromal cells and demonstrate how the true behavior of single cells can be hidden in bulk assays. We also describe assays to measure the growth kinetics of tens of thousands of single cells in parallel and to identify B cells that produce autologous antibodies against tumor-associated antigens. Together, these advances in genomic and phenotypic characterizations enable a deeper understanding of cancer that should help to develop and deploy more effective cancer therapies tailored to individual patients.by Viktor Adalsteinsson.Ph. D
Toward engineered processes for sequencing-based analysis of single circulating tumor cells
Sequencing-based analysis of single circulating tumor cells (CTCs) has the potential to revolutionize our understanding of metastatic cancer and improve clinical care. Technologies exist to enrich, identify, recover, and sequence single cells, but to enable systematic routine analysis of single CTCs from a range of cancer patients, there is a need to establish processes that efficiently integrate these specific operations. Such engineered processes should address challenges associated with the yield and viability of enriched CTCs, the robust identification of candidate single CTCs with minimal degradation of DNA, the bias in whole-genome amplification, and the efficient handling of candidate single CTCs or their amplified DNA products. Advances in methods for single-cell analysis and nanoscale technologies suggest opportunities to overcome these challenges, and could create integrated platforms that perform several of the unit operations together. Ultimately, technologies should be selected or adapted for optimal performance and compatibility in an integrated process. © 2014 Elsevier Ltd
Technological considerations for genome-guided diagnosis and management of cancer
Abstract Technological, methodological, and analytical advances continue to improve the resolution of our view into the cancer genome, even as we discover ways to carry out analyses at greater distances from the primary tumor sites. These advances are finally making the integration of cancer genomic profiling into clinical practice feasible. Formalin fixation and paraffin embedding, which has long been the default pathological biopsy medium, is now being supplemented with liquid biopsy as a means to profile the cancer genomes of patients. At each stage of the genomic data generation process—sample collection, preservation, storage, extraction, library construction, sequencing, and variant calling—there are variables that impact the sensitivity and specificity of the analytical result and the clinical utility of the test. These variables include sample degradation, low yields of nucleic acid, and low variant allele fractions (proportions of assayed molecules carrying variant allele(s)). We review here the most common pre-analytical and analytical factors relating to routine cancer patient genome profiling, some solutions to common challenges, and the major sample preparation and sequencing technology choices available today