A Mechanistic Role For Mir-126, a Hematopoietic Stem Cell Microrna, In Acute Leukemias
Bibliographic record
Abstract
Abstract We have recently shown that miR-126 expression faithfully identifies the engrafting fraction of bone marrow (BM) and cord blood (Gentner et al, Sci Transl Med 2010), in which it regulates hematopoietic stem cell (HSC) pool size by modulating cell cycle progression (Lechman et al., Cell Stem Cell 2012). Antagonizing miR-126 expands HSC by enhancing PI3K/AKT signaling, without causing their exhaustion or transformation. By reconstituting mice with lentivirally transduced BM cells ectopically expressing miR-126, we noted differential effects in HSC and progenitors: while miR-126 overexpressing (126OE) HSC were more quiescent and outcompeted by HSC with physiologic miR-126 expression, progenitor subsets were increased in number and proliferated more upon 126OE. In particular, B lymphopoiesis was enhanced, with the appearance of 126OE-vector marked, CD45(low)CD19+Ig(-) B cell progenitors in the peripheral blood. This abnormal population was transiently observed in all 126OE (n=45), but in none of the control mice (n=30), and BM B cell precursors and progenitors from 126OE mice showed significantly reduced levels of apoptosis, as well as a differentiation block at the immature B cell stage. At least part of this effect was due to interference of miR-126 with p53 activation. Consequentially, 20-30% of 126OE mice (as compared to 0% of control mice) followed over 1 year developed vector-marked, high-grade B-cell neoplasms which resembled diffuse large B-cell lymphoma, lymphoblastic lymphoma or acute lymphoblastic leukemia (ALL). Strikingly, by using a tetracycline-regulated, conditional miR-126OE vector, we observed full regression of the expanded abnormal B cell population after switching miR-126 expression off by doxycycline administration, demonstrating that miR-126 is an oncogenic driver in hematologic malignancies. To establish the relevance of miR-126 in human disease, we studied primary samples from patients with acute leukemia. We measured miR-126 expression in blasts from 12 adult patients with acute lymphoblastic leukemia (ALL). miR-126 was highly expressed in all studied cases of ALL (Phil+: n=7, Phil-: n=5), often surpassing the levels found in normal HSC. Unlike in HSC, miR-126 expression was independent from expression of its host gene EGFL7, suggesting an ALL-specific regulation of the miR-126 locus. By exploiting a lentiviral miR-126 reporter vector, we quantified miR-126 activity with single cell resolution after xenotransplantation of miR-126 reporter vector transduced ALL blasts into NSG mice. In 7 out of 12 ALL cases, we identified distinct subpopulations exhibiting different levels of miR-126 activity, and miR-126 (hi) ALL cells were more frequently contained in the CD34+ cell fraction. Moreover, high miR-126 expression correlated with faster and higher ALL engraftment in NSG mice. In acute myeloid leukemia (AML), miR-126 is significantly enriched in leukemic stem cells (LSC) where it governs quiescence and chemotherapy resistance (see abstract by Lechman et al), and analogous studies in ALL are ongoing. To further substantiate the role of miR-126 in AML, we studied miR-126 activity in 11 primary AML cases (4 AML with CBF, core binding factor, mutations; 7 AML with normal karyotype) using the reporter vector technology and the NSG xenotransplantation model. Globally, we found highest miR-126 activity in CBF-mutated AML. However, there was substantial heterogeneity in subpopulations of each single disease. Significantly higher miR-126 levels were found in CD34+, and particularly in CD34+CD38- AML cells, a fraction that is enriched for LSC. To see whether there is a correlation between miR-126 expression and disease progression, we measured miR-126 levels in sorted blasts from paired diagnosis/relapse (n=6) and diagnosis/chemotherapy-refractory (n=8) patient samples. Strikingly, we found a significant up-regulation of miR-126 in the disease progression sample, suggesting a mechanistic role for miR-126 in AML persistence after chemotherapy. In summary, these data support a clinically relevant role of miR-126 in the pathogenesis, treatment response and progession of acute leukemias. Authors AG and SN contributed equally, and LN and BG contributed equally. 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) | 0.001 | 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".