Clonal diversity of mTORC high and low AML before and after chemotherapy

There are two possible mechanisms for the shift of gene expression to a high mTORC1 activity signature after chemotherapy; one is the selection of mTORC1 high cells and the second is the induction of mTORC1 activity following chemotherapy. We assessed these two possible scenarios by introducing genetic barcodes using the ClonTracer library that allowed for clonal tracking of ~0.2 million AML cells. We found that a significant proportion of unique barcodes are represented in both the mTORC1 high and low cell populations. Since barcodes only infect a single cell which has to exist in a high or low state, a significant proportion of barcodes that are represented by cells in both states suggests that induction occurs. Otherwise the proportion should be close to an extreme (0 or 1) meaning most of the populations exist only in mTORC1 high or mTORC1 low states. Additionally, clonal abundance based on barcodes revealed more similarity with respect to the cumulative proportion of represented barcodes between mTORC1 high and low cells in treated cohorts compared with non-treated cohorts. These data suggest a more similar distribution of mTORC1 high and low cells in these populations which would arise primarily due to induction rather than selection. Overall design: Clonal abundance between four hundred thousand mTORC1 high (mVenus low) or mTORC1 low (mVenus high) AML cells harvested from the mouse bone marrow before (day 0) or at either of the 3 different time after chemotherapy (day 5, 7, and 14) were compared.