A Tumor Suppressor microRNA Defines the Leukemic Hierarchy in Acute Myeloid Leukemia
Bibliographic record
Abstract
Abstract In order to identify functionally relevant microRNAs (miRNA) in AML, we profiled global miRNA expression in a murine AML progression model based on Hoxa9 and Meis1 overexpression. We found miR-155 and miR-708 as the most significantly upregulated miRNA species in leukemic Hoxa9/Meis1 cells compared to the preleukemic Hoxa9/ctrl cells (both p<0.01). Subsequent analysis of various AML subtypes (CN-AML, t(11q23), t(8;21), t(15;17), n=38) showed significantly elevated levels of miR-155 and miR-708 in all tested samples (n=5-10) compared to total bone marrow from healthy donors, indicating potential oncogenic roles for these miRNAs. We further investigated, in vivo, the role of miR-155 and miR-708 in AML by retroviral overexpression with Hoxa9 in murine bone marrow (mbm) cells followed by syngeneic transplantation. Overexpression of miR-155 in conjunction with Hoxa9 (Hoxa9/miR-155) caused a significantly accelerated onset of a myelomonocytic leukemia within 93 days (survival 93±23 days, p<0.0001), but still a less aggressive course of disease compared to mice transplanted with Hoxa9/Meis1 (survival 36±4 days, p<0.0001). We then hypothesized that the combination of miR-155 and miR-708 could further replace the oncogenic potential of Meis1. Therefore, mbm cells were retrovirally transduced with Hoxa9, miR-155 and miR-708 (Hoxa9/155/708) or Hoxa9 and miR-708 (Hoxa9/miR-708) and functionally analyzed in vitro and in vivo. To our surprise, miR-708 abrogated the leukemogenic effect of Hoxa9, alone or in combination with Hoxa9/miR-155 in vivo (p=0.0117, p<0.0001, the mice were sacrificed after 197 days), with little or no engraftment. To understand why miR-708, a potent tumor suppressor miRNA, is upregulated in the highly aggressive Hoxa9/Meis1 AML cells, we first showed in vivo that miR-708 does not impair the development of AML by Hoxa9/Meis1 cells. In order to explore the role of miR-708 in leukemia initiating cells (LIC), we FACS-sorted subpopulations enriched for LIC based on c-kit, Mac-1 and Gr-1 expression within the Hoxa9/Meis1 cells. Of the three subpopulations (c-kit+ Gr-1- Mac-1-, c-kit+ Gr-1+ Mac-1+, c-kit- Gr-1+ Mac-1+) the transplanted c-kit+ Gr-1- Mac-1- cells caused a significantly shorter survival (survival 36 days, range: 32-37d) compared to the other sorted subpopulations (p=0.0072 and p=0.0021, respectively), whereas the c-kit- Gr-1+ Mac-1+ subpopulation exhibited the longest survival (survival 44 days, range: 42-51d). Based on these findings, we measured miR-708 and miR-155 levels in the sorted Hoxa9/Meis1 subpopulations by qRT-PCR. Strikingly, no difference compared to bulk cells was detected for miR-155, highlighting its role as an oncogenic driver in all subpopulations. In contrast, miR-708 showed a distinct expression pattern with lower expression in the LIC-enriched c-kit+ Gr-1- Mac-1- subpopulation compared to bulk (p=0.032), allowing discernment of the LIC enriched population and highlighting its role as an orchestrator of the leukemic hierarchy. Adapted from these findings, we developed an AML 4-step model (Hoxa9/miR-708, Hoxa9/ctrl, Hoxa9/miR-155, Hoxa9/Meis1) based on four immortalized Hoxa9 based cell lines with completely different in vivo properties ranging from no engraftment to induction of highly aggressive AML. Considering the central role of Hoxa9/Meis1 in AML, we demonstrate, for the first time, the concept of a tumor suppressor miRNA that stratifies the leukemic hierarchy driven by an oncogenic miRNA. Moreover, we present a new AML 4-step model as a novel tool that will allow detailed investigation of the impact of new oncogenes at every step of leukemogenesis. Disclosures Buske: CELLTRION, Inc.: Consultancy, Honoraria.
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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".