Honors & Awards
NIH T32 Cancer Biology Training Grant, Stanford University (2016-present)
Doctor of Philosophy, Stanford University, CANBI-PHD (2023)
BA, Columbia University, Neuroscience & Behavior (2013)
Maximilian Diehn, Postdoctoral Faculty Sponsor
Inferring gene expression from cell-free DNA fragmentation profiles.
Profiling of circulating tumor DNA (ctDNA) in the bloodstream shows promise for noninvasive cancer detection. Chromatin fragmentation features have previously been explored to infer gene expression profiles from cell-free DNA (cfDNA), but current fragmentomic methods require high concentrations of tumor-derived DNA and provide limited resolution. Here we describe promoter fragmentation entropy as an epigenomic cfDNA feature that predicts RNA expression levels at individual genes. We developed 'epigenetic expression inference from cell-free DNA-sequencing' (EPIC-seq), a method that uses targeted sequencing of promoters of genes of interest. Profiling 329 blood samples from 201 patients with cancer and 87 healthy adults, we demonstrate classification of subtypes of lung carcinoma and diffuse large B cell lymphoma. Applying EPIC-seq to serial blood samples from patients treated with PD-(L)1 immune-checkpoint inhibitors, we show that gene expression profiles inferred by EPIC-seq are correlated with clinical response. Our results indicate that EPIC-seq could enable noninvasive, high-throughput tissue-of-origin characterization with diagnostic, prognostic and therapeutic potential.
View details for DOI 10.1038/s41587-022-01222-4
View details for PubMedID 35361996
Integrating genomic features for non-invasive early lung cancer detection.
2020; 580 (7802): 245-251
Radiologic screening of high-risk adults reduces lung-cancer-related mortality1,2; however, a small minority of eligible individuals undergo such screening in the United States3,4. The availability of blood-based tests could increase screening uptake. Here we introduce improvements to cancer personalized profiling by deep sequencing (CAPP-Seq)5, a method for the analysis of circulating tumour DNA (ctDNA), to better facilitate screening applications. We show that, although levels are very low in early-stage lung cancers, ctDNA is present prior to treatment in most patients and its presence is strongly prognostic. We also find that the majority of somatic mutations in the cell-free DNA (cfDNA) of patients with lung cancer and of risk-matched controls reflect clonal haematopoiesis and are non-recurrent. Compared with tumour-derived mutations, clonal haematopoiesis mutations occur on longer cfDNA fragments and lack mutational signatures that are associated with tobacco smoking. Integrating these findings with other molecular features, we develop and prospectively validate a machine-learning method termed 'lung cancer likelihood in plasma' (Lung-CLiP), which can robustly discriminate early-stage lung cancer patients from risk-matched controls. This approach achieves performance similar to that of tumour-informed ctDNA detection and enables tuning of assay specificity in order to facilitate distinct clinical applications. Our findings establish the potential of cfDNA for lung cancer screening and highlight the importance of risk-matching cases and controls in cfDNA-based screening studies.
View details for DOI 10.1038/s41586-020-2140-0
View details for PubMedID 32269342
An improved ATAC-seq protocol reduces background and enables interrogation of frozen tissues.
We present Omni-ATAC, an improved ATAC-seq protocol for chromatin accessibility profiling that works across multiple applications with substantial improvement of signal-to-background ratio and information content. The Omni-ATAC protocol generates chromatin accessibility profiles from archival frozen tissue samples and 50-μm sections, revealing the activities of disease-associated DNA elements in distinct human brain structures. The Omni-ATAC protocol enables the interrogation of personal regulomes in tissue context and translational studies.
View details for PubMedID 28846090
DNA Methylation and Somatic Mutations Converge on the Cell Cycle and Define Similar Evolutionary Histories in Brain Tumors
2015; 28 (3): 307-317
The evolutionary history of tumor cell populations can be reconstructed from patterns of genetic alterations. In contrast to stable genetic events, epigenetic states are reversible and sensitive to the microenvironment, prompting the question whether epigenetic information can similarly be used to discover tumor phylogeny. We examined the spatial and temporal dynamics of DNA methylation in a cohort of low-grade gliomas and their patient-matched recurrences. Genes transcriptionally upregulated through promoter hypomethylation during malignant progression to high-grade glioblastoma were enriched in cell cycle function, evolving in parallel with genetic alterations that deregulate the G1/S cell cycle checkpoint. Moreover, phyloepigenetic relationships robustly recapitulated phylogenetic patterns inferred from somatic mutations. These findings highlight widespread co-dependency of genetic and epigenetic events throughout brain tumor evolution.
View details for DOI 10.1016/j.ccell.2015.07.012
View details for Web of Science ID 000361420900009
View details for PubMedID 26373278
View details for PubMedCentralID PMC4573399
- Noninvasive Cell-of-Origin Classification of Diffuse Large B-Cell Lymphoma Using Inferred Gene Expression from Cell-Free DNA Sequencing AMER SOC HEMATOLOGY. 2021
A comprehensive circulating tumor DNA assay for detection of translocation and copy number changes in pediatric sarcomas.
Molecular cancer therapeutics
Most circulating tumor DNA (ctDNA) assays are designed to detect recurrent mutations. Pediatric sarcomas share few recurrent mutations but rather are characterized by translocations and copy number changes. We applied CAncer Personalized Profiling by deep Sequencing (CAPP-Seq) for detection of translocations found in the most common pediatric sarcomas. We also applied ichorCNA to the combined off-target reads from our hybrid capture to simultaneously detect copy number alterations. We analyzed 64 prospectively collected plasma samples from 17 pediatric sarcoma patients. Translocations were detected in the pre-treatment plasma of 13 patients and were confirmed by tumor sequencing in 12 patients. Two of these patients had evidence of complex chromosomal rearrangements in their ctDNA. We also detected copy number changes in the pre-treatment plasma of 7 patients. We found that ctDNA levels correlated with metastatic status and clinical response. Furthermore, we detected rising ctDNA levels before relapse was clinically apparent, demonstrating the high sensitivity of our assay. This assay can be utilized for simultaneous detection of translocations and copy number alterations in the plasma of pediatric sarcoma patients. While we describe our experience in pediatric sarcomas, this approach can be applied to other tumors that are driven by structural variants.
View details for DOI 10.1158/1535-7163.MCT-20-0987
View details for PubMedID 34353895
Enhanced detection of minimal residual disease by targeted sequencing of phased variants in circulating tumor DNA.
Circulating tumor-derived DNA (ctDNA) is an emerging biomarker for many cancers, but the limited sensitivity of current detection methods reduces its utility for diagnosing minimal residual disease. Here we describe phased variant enrichment and detection sequencing (PhasED-seq), a method that uses multiple somatic mutations in individual DNA fragments to improve the sensitivity of ctDNA detection. Leveraging whole-genome sequences from 2,538 tumors, we identify phased variants and their associations with mutational signatures. We show that even without molecular barcodes, the limits of detection of PhasED-seq outperform prior methods, including duplex barcoding, allowing ctDNA detection in the ppm range in participant samples. We profiled 678 specimens from 213 participants with B cell lymphomas, including serial cell-free DNA samples before and during therapy for diffuse large B cell lymphoma. In participants with undetectable ctDNA after two cycles of therapy using a next-generation sequencing-based approach termed cancer personalized profiling by deep sequencing, an additional 25% have ctDNA detectable by PhasED-seq and have worse outcomes. Finally, we demonstrate the application of PhasED-seq to solid tumors.
View details for DOI 10.1038/s41587-021-00981-w
View details for PubMedID 34294911
- A noninvasive approach for early prediction of therapeutic benefit from immune checkpoint inhibition for lung cancer AMER ASSOC CANCER RESEARCH. 2020
- Chromatin accessibility patterns in cell-free DNA reveal tumor heterogeneity AMER ASSOC CANCER RESEARCH. 2020
- Integrating genomic features for non-invasive early lung cancer detection NATURE 2020
Noninvasive Early Identification of Therapeutic Benefit from Immune Checkpoint Inhibition.
Although treatment of non-small cell lung cancer (NSCLC) with immune checkpoint inhibitors (ICIs) can produce remarkably durable responses, most patients develop early disease progression. Furthermore, initial response assessment by conventional imaging is often unable to identify which patients will achieve durable clinical benefit (DCB). Here, we demonstrate that pre-treatment circulating tumor DNA (ctDNA) and peripheral CD8 T cell levels are independently associated with DCB. We further show that ctDNA dynamics after a single infusion can aid in identification of patients who will achieve DCB. Integrating these determinants, we developed and validated an entirely noninvasive multiparameter assay (DIREct-On, Durable Immunotherapy Response Estimation by immune profiling and ctDNA-On-treatment) that robustly predicts which patients will achieve DCB with higher accuracy than any individual feature. Taken together, these results demonstrate that integrated ctDNA and circulating immune cell profiling can provide accurate, noninvasive, and early forecasting of ultimate outcomes for NSCLC patients receiving ICIs.
View details for DOI 10.1016/j.cell.2020.09.001
View details for PubMedID 33007267
KEAP1/NFE2L2 mutations predict lung cancer radiation resistance that can be targeted by glutaminase inhibition.
Tumor genotyping is not routinely performed in localized non-small cell lung cancer (NSCLC) due to lack of associations of mutations with outcome. Here, we analyze 232 consecutive patients with localized NSCLC and demonstrate that KEAP1 and NFE2L2 mutations are predictive of high rates of local recurrence (LR) after radiotherapy but not surgery. Half of LRs occurred in KEAP1/NFE2L2 mutation tumors, indicating they are major molecular drivers of clinical radioresistance. Next, we functionally evaluate KEAP1/NFE2L2 mutations in our radiotherapy cohort and demonstrate that only pathogenic mutations are associated with radioresistance. Furthermore, expression of NFE2L2 target genes does not predict LR, underscoring the utility of tumor genotyping. Finally, we show that glutaminase inhibition preferentially radiosensitizes KEAP1 mutant cells via depletion of glutathione and increased radiation-induced DNA damage. Our findings suggest that genotyping for KEAP1/NFE2L2 mutations could facilitate treatment personalization and provide a potential strategy for overcoming radioresistance conferred by these mutations.
View details for DOI 10.1158/2159-8290.CD-20-0282
View details for PubMedID 33071215
Circulating tumor DNA analysis for detection of minimal residual disease after chemoradiotherapy for localized esophageal cancer.
Biomarkers are needed to identify patients at risk of tumor progression following chemoradiotherapy for localized esophageal cancer. These could improve identification of patients at risk for cancer progression and selection of therapy.We performed deep sequencing (CAPP-Seq) analyses of plasma cell-free DNA collected from 45 patients before and after chemoradiotherapy for esophageal cancer, as well as DNA from leukocytes, and fixed esophageal tumor biopsies collected during esophagogastroduodenoscopy. Patients were treated from May 2010 through October 2015; 23 patients subsequently underwent esophagectomy and 22 did not undergo surgery. We also sequenced DNA from blood samples from 40 healthy individuals (controls). We analyzed 802 regions of 607 genes for single-nucleotide variants previously associated with esophageal adenocarcinoma or squamous cell carcinoma. Patients underwent imaging analyses 6-8 weeks after chemoradiotherapy and were followed for 5 years. Our primary aim was to determine whether detection of circulating tumor DNA (ctDNA) following chemoradiotherapy is associated with risk of tumor progression (growth of local, regional, or distant tumors, detected by imaging or biopsy).The median proportion of tumor-derived DNA in total cell-free DNA before treatment was 0.07%, indicating that ultrasensitive assays are needed for quantification and analysis of ctDNA from localized esophageal tumors. Detection of ctDNA following chemoradiotherapy was associated with tumor progression (hazard ratio, 18.7; P<.0001), formation of distant metastases (hazard ratio, 32.1; P<.0001), and shorter disease-specific survival times (hazard ratio, 23.1; P<.0001). A higher proportion of patients with tumor progression had new mutations detected in plasma samples collected after chemoradiotherapy than patients without progression (P=.03). Detection of ctDNA after chemoradiotherapy preceded radiographic evidence of tumor progression by an average of 2.8 months. Among patients who received chemoradiotherapy without surgery, combined ctDNA and metabolic imaging analysis predicted progression in 100% of patients with tumor progression, compared with 71% for only ctDNA detection and 57% for only metabolic imaging analysis (P<.001 for comparison of either technique to combined analysis).In an analysis of cell-free DNA in blood samples from patients who underwent chemoradiotherapy for esophageal cancer, detection of ctDNA was associated with tumor progression, metastasis, and disease-specific survival. Analysis of ctDNA might be used to identify patients at highest risk for tumor progression.
View details for DOI 10.1053/j.gastro.2019.10.039
View details for PubMedID 31711920
Phased Variant Enrichment for Enhanced Minimal Residual Disease Detection from Cell-Free DNA
American Society of Hematology
View details for DOI 10.1182/blood-2019-131267
- Distinct Chromatin Accessibility Profiles of Lymphoma Subtypes Revealed By Targeted Cell Free DNA Profiling AMER SOC HEMATOLOGY. 2018
Polybrominated diphenyl ethers (PBDEs) and hydroxylated PBDE metabolites (OH-PBDEs) in maternal and fetal tissues, and associations with fetal cytochrome P450 gene expression.
2018; 112: 269-278
Human fetal exposures to polybrominated diphenyl ethers (PBDEs) and their metabolites (OH-PBDEs) are unique from adults, and in combination with a different metabolic profile, may make fetal development more sensitive to adverse health outcomes from these exposures. However, we lack data to characterize human fetal PBDE exposures and the metabolic factors that can influence these exposures.We examined differences between 2nd trimester maternal and fetal exposures to PBDEs and OH-PBDEs. We also characterized fetal cytochrome P450 (CYP) mRNA expression and its associations with PBDE exposures.We collected paired samples of maternal serum and fetal liver (n=86) with a subset having matched placenta (n=50). We measured PBDEs, OH-PBDEs, and mRNA expression of CYP genes (e.g. CYP1A1, -2E1, -2J2, -2C9) in all samples. As a sensitivity analysis, we measured PBDEs and OH-PBDEs in umbilical cord serum from a subset (n=22).BDE-47 was detected in ≥96% of all tissues. Unadjusted ∑PBDEs concentrations were highest in fetal liver (geometric mean (GM)=0.72ng/g), whereas lipid-adjusted concentrations were highest in cord serum (111.12ng/g lipid). In both cases, fetal concentrations were approximately two times higher than maternal serum levels (GM=0.33ng/g or 48.75ng/g lipid). ΣOH-PBDEs were highest in maternal and cord sera and 20-200 times lower than PBDE concentrations. In regression models, maternal BDE-47 explained more of the model variance of liver than of placenta BDE-47 concentrations (adjusted R2=0.79 vs 0.48, respectively). In adjusted logistic regression models, ∑PBDEs were positively associated with expression of CYP2E1 and -2J2 (placenta), and -1A1 (liver) (p<0.05).Our findings suggest that under normal conditions of mid-gestation, the human fetus is directly exposed to concentrations of PBDEs that may be higher than previously estimated based on maternal serum and that these exposures are associated with the expression of mRNAs coding for CYP enzymes. These results will help frame and interpret findings from studies that use maternal or cord blood as proxy measures of fetal exposures, and will inform the molecular pathways by which PBDEs affect human health.
View details for DOI 10.1016/j.envint.2017.12.030
View details for PubMedID 29316516
Transcriptional Dynamics of Cultured Human Villous Cytotrophoblasts.
2017; 158 (6): 1581-1594
During human pregnancy, cytotrophoblasts (CTBs) play key roles in uterine invasion, vascular remodeling, and anchoring of the feto-placental unit. Due to the challenges associated with studying human placentation in utero, cultured primary villous CTBs are used as a model of the differentiation pathway that leads to invasion of the uterine wall. In vitro, CTBs emulate in vivo cell behaviors, such as migration, aggregation, and substrate penetration. Although some of the molecular features related to these cell behaviors have been described, the underlying mechanisms, at a global level, remain undefined at midgestation. Thus, in this study, we characterized second-trimester CTB differentiation/invasion in vitro, correlating the major morphological transitions with the transcriptional changes that occurred at these steps. After plating on Matrigel as individual cells, CTBs migrated toward each other and formed multicellular aggregates. In parallel, using a microarray approach, we observed differentially expressed (DE) genes across time, which were enriched for numerous functions, including cell migration, vascular remodeling, morphogenesis, cell communication, and inflammatory signaling. DE genes encoded several molecules that we and others previously linked to critical CTB function in vivo, suggesting that the novel DE molecules we discovered played important roles. Immunolocalization confirmed that CTBs in situ gave a signal for two of the most highly expressed genes in vitro. In summary, we characterized, at a global level, the temporal dynamics of primary human CTB gene expression in culture. These data will enable future analyses of various types of in vitro perturbations-for example, modeling disease processes and environmental exposures.
View details for DOI 10.1210/en.2016-1635
View details for PubMedID 28323933
View details for PubMedCentralID PMC5460928