Education & Certifications
Bachelor of Arts, Harvard University, Neurobiology (2013)
Epidemiologic Investigation of a Cluster of Neuroinvasive Bacillus cereus Infections in 5 Patients With Acute Myelogenous Leukemia.
Open forum infectious diseases
2015; 2 (3): ofv096-?
Background. Five neuroinvasive Bacillus cereus infections (4 fatal) occurred in hospitalized patients with acute myelogenous leukemia (AML) during a 9-month period, prompting an investigation by infection control and public health officials. Methods. Medical records of case-patients were reviewed and a matched case-control study was performed. Infection control practices were observed. Multiple environmental, food, and medication samples common to AML patients were cultured. Multilocus sequence typing was performed for case and environmental B cereus isolates. Results. All 5 case-patients received chemotherapy and had early-onset neutropenic fevers that resolved with empiric antibiotics. Fever recurred at a median of 17 days (range, 9-20) with headaches and abrupt neurological deterioration. Case-patients had B cereus identified in central nervous system (CNS) samples by (1) polymerase chain reaction or culture or (2) bacilli seen on CNS pathology stains with high-grade B cereus bacteremia. Two case-patients also had colonic ulcers with abundant bacilli on autopsy. No infection control breaches were observed. On case-control analysis, bananas were the only significant exposure shared by all 5 case-patients (odds ratio, 9.3; P = .04). Five environmental or food isolates tested positive for B cereus, including a homogenized banana peel isolate and the shelf of a kitchen cart where bananas were stored. Multilocus sequence typing confirmed that all case and environmental strains were genetically distinct. Multilocus sequence typing-based phylogenetic analysis revealed that the organisms clustered in 2 separate clades. Conclusions. The investigation of this neuroinvasive B cereus cluster did not identify a single point source but was suggestive of a possible dietary exposure. Our experience underscores the potential virulence of B cereus in immunocompromised hosts.
View details for DOI 10.1093/ofid/ofv096
View details for PubMedID 26269794
View details for PubMedCentralID PMC4531223
The human microbiome in hematopoiesis and hematologic disorders.
2015; 126 (3): 311-318
Humans are now understood to be in complex symbiosis with a diverse ecosystem of microbial organisms, including bacteria, viruses, and fungi. Efforts to characterize the role of these microorganisms, commonly referred as the microbiota, in human health have sought to answer the fundamental questions of what organisms are present, how are they functioning to interact with human cells, and by what mechanism are these interactions occurring. In this review, we describe recent efforts to describe the microbiota in healthy and diseased individuals, summarize the role of various molecular technologies (ranging from 16S ribosomal RNA to shotgun metagenomic sequencing) in enumerating the community structure of the microbiota, and explore known interactions between the microbiota and humans, with a focus on the microbiota's role in hematopoiesis and hematologic diseases.
View details for DOI 10.1182/blood-2015-04-574392
View details for PubMedID 26012569
View details for PubMedCentralID PMC4504946
EGFR Variant Heterogeneity in Glioblastoma Resolved through Single-Nucleus Sequencing
2014; 4 (8): 956-971
Glioblastomas (GBM) with EGFR amplification represent approximately 50% of newly diagnosed cases, and recent studies have revealed frequent coexistence of multiple EGFR aberrations within the same tumor, which has implications for mutation cooperation and treatment resistance. However, bulk tumor sequencing studies cannot resolve the patterns of how the multiple EGFR aberrations coexist with other mutations within single tumor cells. Here, we applied a population-based single-cell whole-genome sequencing methodology to characterize genomic heterogeneity in EGFR-amplified glioblastomas. Our analysis effectively identified clonal events, including a novel translocation of a super enhancer to the TERT promoter, as well as subclonal LOH and multiple EGFR mutational variants within tumors. Correlating the EGFR mutations onto the cellular hierarchy revealed that EGFR truncation variants (EGFRvII and EGFR carboxyl-terminal deletions) identified in the bulk tumor segregate into nonoverlapping subclonal populations. In vitro and in vivo functional studies show that EGFRvII is oncogenic and sensitive to EGFR inhibitors currently in clinical trials. Thus, the association between diverse activating mutations in EGFR and other subclonal mutations within a single tumor supports an intrinsic mechanism for proliferative and clonal diversification with broad implications in resistance to treatment.We developed a novel single-cell sequencing methodology capable of identifying unique, nonoverlapping subclonal alterations from archived frozen clinical specimens. Using GBM as an example, we validated our method to successfully define tumor cell subpopulations containing distinct genetic and treatment resistance profiles and potentially mutually cooperative combinations of alterations in EGFR and other genes.
View details for DOI 10.1158/2159-8290.CD-13-0879
View details for Web of Science ID 000343120400029
View details for PubMedID 24893890
View details for PubMedCentralID PMC4125473
In Search of a Candidate Pathogen for Giant Cell Arteritis: Sequencing-Based Characterization of the Giant Cell Arteritis Microbiome
ARTHRITIS & RHEUMATOLOGY
2014; 66 (7): 1939-1944
To characterize the microbiome of the temporal artery in patients with giant cell arteritis (GCA), and to apply an unbiased and comprehensive shotgun sequencing-based approach to determine whether there is an enrichment of candidate pathogens in the affected tissue.Temporal artery biopsy specimens were collected from patients at a single institution over a period of 4 years, and unbiased DNA sequencing was performed on 17 formalin-fixed, paraffin-embedded specimens. Twelve of the 17 patients fulfilled the clinical and histopathologic criteria for GCA, and the other 5 patients served as controls. Using PathSeq software, human DNA sequences were computationally subtracted, and the remaining non-human DNA sequences were taxonomically classified using a comprehensive microbial sequence database. The relative abundance of microbes was inferred based on read counts assigned to each organism. Comparison of the microbial diversity between GCA cases and controls was carried out using hierarchical clustering and linear discriminant analysis of effect size.Propionibacterium acnes and Escherichia coli were the most abundant microorganisms in 16 of the 17 samples, and Moraxella catarrhalis was the most abundant organism in 1 control sample. Pathogens previously described to be correlated with GCA were not differentially abundant in cases compared to controls. There was not a significant burden of likely pathogenic viruses.DNA sequencing of temporal artery biopsy specimens from GCA cases, in comparison with non-GCA controls, showed no evidence of previously identified candidate GCA pathogens. A single pathogen was not clearly and consistently associated with GCA in this case series.
View details for DOI 10.1002/art.38631
View details for Web of Science ID 000339092800029
View details for PubMedID 24644069
View details for PubMedCentralID PMC4113339
Somatic mutation of CDKN1B in small intestine neuroendocrine tumors
2013; 45 (12): 1483-U110
The diagnosed incidence of small intestine neuroendocrine tumors (SI-NETs) is increasing, and the underlying genomic mechanisms have not yet been defined. Using exome- and genome-sequence analysis of SI-NETs, we identified recurrent somatic mutations and deletions in CDKN1B, the cyclin-dependent kinase inhibitor gene, which encodes p27. We observed frameshift mutations of CDKN1B in 14 of 180 SI-NETs, and we detected hemizygous deletions encompassing CDKN1B in 7 out of 50 SI-NETs, nominating p27 as a tumor suppressor and implicating cell cycle dysregulation in the etiology of SI-NETs.
View details for DOI 10.1038/ng.2821
View details for Web of Science ID 000327715800016
View details for PubMedID 24185511
View details for PubMedCentralID PMC4239432
Passenger deletions generate therapeutic vulnerabilities in cancer
2012; 488 (7411): 337-?
Inactivation of tumour-suppressor genes by homozygous deletion is a prototypic event in the cancer genome, yet such deletions often encompass neighbouring genes. We propose that homozygous deletions in such passenger genes can expose cancer-specific therapeutic vulnerabilities when the collaterally deleted gene is a member of a functionally redundant family of genes carrying out an essential function. The glycolytic gene enolase 1 (ENO1) in the 1p36 locus is deleted in glioblastoma (GBM), which is tolerated by the expression of ENO2. Here we show that short-hairpin-RNA-mediated silencing of ENO2 selectively inhibits growth, survival and the tumorigenic potential of ENO1-deleted GBM cells, and that the enolase inhibitor phosphonoacetohydroxamate is selectively toxic to ENO1-deleted GBM cells relative to ENO1-intact GBM cells or normal astrocytes. The principle of collateral vulnerability should be applicable to other passenger-deleted genes encoding functionally redundant essential activities and provide an effective treatment strategy for cancers containing such genomic events.
View details for DOI 10.1038/nature11331
View details for Web of Science ID 000307501000033
View details for PubMedID 22895339
View details for PubMedCentralID PMC3712624