|M.Sc Student||Pery Neta|
|Subject||Unrevealing the Heterogeneity of Leukemia using|
Single Cells Analysis
|Department||Department of Medicine||Supervisor||Professor Emeritus Jacob Rowe|
|Full Thesis text|
Human cancers display substantial intra-tumoral genetic heterogeneity, which may facilitate tumor survival and present a major challenge to treatment. We focused our research on acute leukemia which although had major discoveries in the last decade still has poor prognosis, mainly due to relapse. It is not known whether after chemotherapy relapse is initiated by cells that escape chemotherapy stochastically, or by special cells unharmed by chemotherapy due to intrinsic properties, such as quiescence.
In order to explore the genetic relations between leukemia cells at relapse and diagnosis, we applied a method which initially separates the cells based on leukemia associated immuno phenotype and then utilizes somatic mutations in over 100 microsatellites among individual cells to reconstruct cell lineage trees from cells harvested from acute leukemia patients at diagnosis and relapse. Each tree reflects the intra-tumoral heterogeneity and evolution of the tumor from which the cells were harvested. Reconstructing the lineage trees of 11 acute myeloid leukemia patients demonstrated that most relapse cells are rarely dividing and are related to the stem cells population, indicating dormancy is a possible mechanism for their survival. However, when examining the lineage trees of acute lymphoid leukemia, this dormancy is not exhibited. In addition a single chronic myeloid leukemia patient in myeloid blast crisis was examined and was found to have mismatch-repair deficiency in most of the relapse cells. Two common acute myeloid leukemia mutations were studied in single cells. Loss of heterozygousity (LOH) was demonstrated to a varying degree in diagnosis and relapse.
In conclusion, diverse relapse mechanisms were observed by reconstruction of lineage trees from single cells and most likely more than one mechanism affects each leukemia type and patient.