Single stem cell clones of an acute myeloid leukaemia patient display functional heterogeneity in vivo

Zeller, Christina Maria (2020): Single stem cell clones of an acute myeloid leukaemia patient display functional heterogeneity in vivo. Dissertation, LMU München: Faculty of Biology

Abstract

Acute myeloid leukaemia (AML) is a haematopoietic malignancy characterised by major genetic and functional heterogeneity. As clinical challenge, the most adverse subclone determines a patient’s outcome. A better understanding of tumour heterogeneity is required to direct treatment strategies against adverse subclones. In the present work, I aimed at characterising the genetic, epigenetic, transcriptomic and functional heterogeneity within the tumour sample of a single patient with AML. To enable functional in vivo studies, a patient-derived xenograft (PDX) mouse model was established from the AML sample. Upon re-transplanting minor numbers of PDX AML cells into immunocompromised mice, I generated twelve PDX AML populations that derived from a single stem cell, as proven by molecular barcoding using lentiviruses. The resulting PDX AML single cell clones (SCCs) were lentivirally marked with an individual combination of fluorochromes, enabling their separate analysis via flow cytometry in competitive in vivo assays. Epigenetic and transcriptomic analyses showed that PDX AML SCCs clustered according to their origin from first or second relapse. Genetic analyses revealed the existence of at least four genetically distinct subclones. Functional in vivo assays uncovered heterogeneity between the different PDX AML SCCs concerning stem cell capacity, growth, dormancy and treatment response. The most adverse PDX AML SCC displayed rapid growth in competitive in vivo assays combined with a partial resistance towards treatment with conventional chemotherapy. The aggressive functional behaviour was associated with a unique deletion of chromosome 17q correlating to i.a. an enrichment in HOX signalling. Of clinical importance and while resistant towards several treatment options, the clone responded to systemic treatment with the hypomethylating agent 5-azacitidine. Taken together, the data revealed that the known heterogeneity within tumor cells of a single patient with AML results in major functional heterogeneity in vivo. Clonal evolution of genetic changes can generate functionally aggressive clones, which might still respond to well-chosen second-line treatment, improving the clinical situation.

• Item Type: Theses (Dissertation, LMU Munich)
• Keywords: acute myeloid leukaemia, patient-derived xenograft, single cell clones, cancer, tumour heterogeneity
• Subjects: 500 Natural sciences and mathematics; 500 Natural sciences and mathematics > 570 Life sciences
• Faculties: Faculty of Biology
• Language: English
• Date of oral examination: 22. December 2020
• 1. Referee: Enard, Wolfgang
• Signature of the printed copy: 0001/UMC 29325