Combination Targeted Therapy to Impair Self-Renewal Capacity of Human Blast Crisis Leukemia Stem Cells
Bibliographic record
Abstract
Abstract Abstract 1693 The aim of this study is to develop clinical strategies that will HALT progression of CML by reducing leukemia stem cell (LSC) burden using a clinical grade JAK2 inhibitor, SAR302503 (SAR503, Sanofi, Cambridge, MA), alone or in combination with a potent BCR-ABL inhibitor, dasatinib. For this, CML patient samples in blast crisis phase (BC CML) were subjected to immunomagnetic bead CD34 selection or FACS Aria ll sorted to obtain leukemic progenitors (LSC/CD34+CD38+Lin−). Malignant progenitors were then transplanted into neonatal RAG2−/−gc−/− mice, and 8 weeks post-transplant, mice were treated with SAR503, dasatinib and vehicle for 14 days. Following treatment, hematopoietic tissues were analyzed for human engraftment by FACS analysis. Our results revealed that single agent experiments with SAR503 had a cytostatic rather than a cytoreductive effect on BC LSC. The treatment alone (60 mg/kg twice daily administered by oral gavage) did not significantly reduce leukemic progenitor burden in the liver, spleen, bone marrow and peripheral blood. Conversely, combination therapy with SAR503 and dasatinib (50mg/kg/day) significantly reduced LSC progenitors in all tissues examined. Interestingly, we observed that dasatinib alone therapy reduced the LSC burden in the liver, spleen, and peripheral blood, but the bone marrow retained a significant population of BC LSC. Also we found that the GMP population, previously shown to be enriched for BC LSC (Jamieson et al NEJM 2004; Abrahamsson et al PNAS 2009), was preferentially localized in the bone marrow. As shown by our laboratory and others, LSC therapeutic resistance may be influenced by extrinsic cues provided by the niche (e.g. promoting quiescence). Because quiescence has been implicated in driving tyrosine kinase inhibitor resistance and LSC survival and because the bone marrow retains a resistant population, we decide to perform secondary transplantation experiments to determine relapse potential (self-renewal). LSC progenitors were isolated by immunomagnetic bead selection of human CD34+ cells from marrows and spleens of treated mice. After serially transplanting an equal number of this cells into secondary recipients, we observed a significant reduction in LSC serial transplantation only following combination treatment, suggesting that the combination therapy can abolish LSC self-renewal capacity and thereby potentially prevent relapse. To validate drug exposure, we have been performing both genomic and nanoproteomic analysis. Regarding the proteomics validation studies, we analyzed sorted LSC derived from spleen (pooled 5 mice per group) that were treated with vehicle or SAR503 for 14 days. The analysis was performed to detect status of p-JAK2, JAK2, p-STAT5 and B2-microglobulin (loading control). We observed a down regulation on the levels of p-JAk2 (active site Tyr 1007–08) and p-Stat5 (active site Tyr 694) (35% and 42% respectively), while no changes are observed for total JAK2 protein or B2M between both conditions. The full transcriptome sequencing, on sorted LSC treated with SAR503 alone and in combination with dasatinib, identified specific isoform changes in the JAK/STAT pathway that could be used as biomarkers of response and could explain the synergistic effect of the combination therapy. We have also characterized, at an isoform level, biomarkers of resistance that could explain relapse of disease after single agent therapy and we are currently validating these findings. Disclosures: No relevant conflicts of interest to declare.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".