Date of Award

5-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Program

Pharmaceutical Sciences

Track

Pharmacometrics

Research Advisor

Charles Gawad, MD, Ph.D.

Committee

Hassan Almoazen, Ph.D. Gerard P. Zambetti, Ph.D.

Keywords

Acute Lymphoblastic Leukemia, Circulating-tumor DNA (Ct-DNA), Clonal Dynamics, Leukemia-derived Circulating DNA, Pediatrics, Somatic Mutations

Abstract

Despite the improved outcome associated with current treatment strategies ofpediatric acute lymphoblastic leukemia (ALL), relapse still represents a major challenge. Pediatric ALL demonstrates branched evolution in response to selective pressure exerted by therapy; relapse founder clones emerge from pre-leukemic clones or minor subclones present at diagnosis. It is hence crucial to develop biomarkers capable of tracking subclones throughout therapy. Current practices for monitoring disease response in leukemia rely on the analysis of BM biopsy sample at specific time points throughout therapy. Not only the invasiveness of the BM biopsy hinders the sequential sampling, but also, the currently implied techniques are associated with a lack of sensitivity to detect subclones other than the major diagnostic clone. Somatic mutation detection in circulating-tumor DNA (Ct-DNA) offers a new venue for non-invasive studying of genetic heterogeneity and tracking clonal dynamics throughout therapy. Here, we employ targeted Next-Generation Sequencing (NGS) using a specifically designed ALL custom gene panel for Ct-DNA analysis of sequential plasma samples of 14 pediatric ALL during remission induction therapy. Utilizing 1 ml of plasma, Ct-DNA successfully captured all the clinically relevant somatic single nucleotide variants (SNVs) detected by whole exome sequencing (WES) in bone marrow (BM) biopsy samples at diagnosis. Moreover, we were able to show the ability of Ct-DNA analysis to track the change in the mutant allele fraction (MAF) across multiple time points as well as, to detect mutations in Flowcytometry (FC) MRD-negative patients. Taken together, sequential analysis of Ct-DNA in plasma demonstrates a role, as a non-invasive technique, for detecting the clonal composition as well as, tracking clonal dynamics in pediatric ALL.

ORCID

http://orcid.org/https://orcid.org/0000-0001-8681-2680

DOI

10.21007/etd.cghs.2018.0453

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