miR-196b — the HOXA-cluster microRNA that is a direct KMT2A-fusion target and a genuine double agent
also called miR-196b · hsa-mir-196b · MIR196B · mir-196b · hsa-miR-196b-5p
miR-196b is a tiny RNA encoded inside the HOXA gene cluster, right between HOXA9 and HOXA10, and it is switched on very strongly by KMT2A fusions — about 500 times higher than in other kinds of childhood leukemia. What makes it strange is that it dampens HOXA9 and MEIS1, the very genes the leukemia depends on, while also switching off a cell-death gene, so whether it helps or hinders the leukemia depends on the stage of the disease.
The same thing, for a scientist
MIR196B (ENSG00000283745; miRBase MI0001150; RNAcentral URS000075D019; GRCh38 chr7:27,169,480-27,169,563, minus strand, 7p15.2) lies inside the HOXA cluster between HOXA9 (chr7:27,162,438-27,175,180) and HOXA10 (chr7:27,170,592-27,180,261) and is co-expressed with the 5' HOXA genes [E6]. It is the best-documented non-coding element in KMT2A-rearranged leukemia. Wild-type MLL normally regulates mir-196b in a pattern matching Hoxa9/Hoxa10 during ES-cell differentiation; leukemogenic MLL fusion proteins overexpress it; a miR-196-specific antagomir abrogated the replating potential of MLL-AF9-transformed bone marrow cells, and overexpression in 55 primary leukemia samples was specific to MLL-associated leukemias [E1]. Quantitatively, in a 100-plus-case paediatric ALL series miR-196b was **~500-fold higher in 20 MLL-rearranged cases** than in the remaining precursor B-ALL cases (P < 0.001), and independently of MLL fusion partner and of maturation status [E2]. Its target set is unusual and is the reason this node matters: miR-196 directs cleavage of HOXB8 [E5], miR-196a/b bind and repress the ERG 3'UTR [E3], and — decisively — miR-196b **directly targets both the HOXA9/MEIS1 oncogenes and the FAS tumour suppressor**, so forced expression *delays* MLL-fusion leukemogenesis in primary transplantation while *accelerating* it in secondary transplantation [E4]. It is therefore neither a clean dependency nor a clean passenger, and the field's habit of calling it 'an oncogenic miRNA in MLL leukemia' is a simplification the primary data do not support.
Why this is a direct fusion target and not a bystander
Popovic R et al. established four things in one paper 1:
- Wild-type MLL regulates mir-196b in a pattern similar to the surrounding 5' Hox genes Hoxa9 and Hoxa10 during embryonic-stem-cell differentiation. So this is a normal MLL target, not a neomorphic one.
- Within haematopoiesis mir-196b is most abundant in short-term HSCs and is down-regulated in more differentiated cells — the same expression axis as the fusion's other targets.
- Leukemogenic MLL fusion proteins cause overexpression of mir-196b, and overexpression was specific to MLL-associated leukemias in 55 primary leukemia samples.
- A miR-196-specific antagomir abrogated the replating potential of MLL-AF9-transformed bone-marrow cells in methylcellulose, which the authors read as miR-196b function being necessary for MLL-fusion-mediated immortalization. Overexpression in bone-marrow progenitors increased proliferative capacity and survival and caused a partial block in differentiation.
Point 4 is the dependency claim, and it is the one to hold most loosely: an antagomir against 'miR-196' does not discriminate miR-196a from miR-196b, replating potential is a surrogate for self-renewal rather than a measure of it, and no in vivo antagomir experiment was done.
The independent quantification is stronger than the mechanism. Schotte D et al. measured miRNA expression across seven paediatric ALL subtypes and found miR-196b 500-fold higher in MLL-rearranged cases and 800-fold higher in 5 of 15 T-ALL cases relative to the remaining precursor B-ALL cases (P < 0.001), in a series comprising 20 MLL-rearranged, 15 T-ALL and 57 other B-ALL cases 2. Two details matter. The expression did not correlate with immunophenotype, immunoglobulin/T-cell-receptor rearrangement status or MLL fusion partner — so this is a property of KMT2A rearrangement as a class, which is exactly what a KMT2A::AFF1 project wants. And the T-ALL overlap shows it is a HOXA-activation readout rather than a KMT2A-specific one, since HOXA-high T-ALL (often NUP98- or SET-NUP214-driven, or CALM-AF10) reaches the same place by a different route.
The double-agent problem — the most important and least-cited result in this node1 deeper
Li Z et al. showed that miR-196b directly targets HOXA9 and MEIS1, the two genes whose overexpression is the canonical output of the KMT2A-fusion program, and the proapoptotic gene FAS, which is down-regulated in MLL-rearranged leukemia 4.
The consequence is stage-dependent and counter-intuitive:
- Forced miR-196b expression significantly delayed MLL-fusion-mediated leukemogenesis in primary bone-marrow transplantation, through suppression of Hoxa9/Meis1.
- Ectopic miR-196b produced more aggressive leukemic phenotypes and much faster leukemogenesis in secondary transplantation, attributed to further repression of Fas.
- Overexpressing FAS significantly inhibited leukemogenesis and reversed the miR-196b-mediated phenotypes, which is the rescue experiment that anchors the Fas arm of the mechanism.
This is direct counter-evidence to a simple reading of 1. If miR-196b represses HOXA9 and MEIS1, then an anti-miR-196b therapeutic would be expected to raise HOXA9/MEIS1 — precisely the opposite of the therapeutic goal in KMT2A-r leukemia, where menin inhibitors are trying to lower them. Any proposal to antagonise miR-196b in this disease has to explain why it would not de-repress the program it is meant to switch off.
There is a reconciliation available — the net effect depends on whether the cell is at the initiation stage (where HOXA9/MEIS1 dosage is limiting) or the maintenance/relapse stage (where apoptotic resistance via FAS loss is limiting) — but that reconciliation is a hypothesis, not a demonstrated model, and it predicts that the direction of benefit from anti-miR-196b therapy would flip over the course of the disease.
The other documented targets
HOXB8. The founding target of this miRNA family: miR-196 directs cleavage (not merely translational repression) of HOXB8 mRNA, an unusually Argonaute-slicer-like mode of action for a vertebrate miRNA, driven by near-perfect complementarity 5. This is mechanistically important because it means miR-196b can act catalytically rather than stoichiometrically on a target with a near-perfect site, and HOXB8-like near-perfect sites are rare.
ERG. miR-196a and miR-196b both bind the ERG 3'UTR and down-regulate ERG in luciferase and transfection assays; miR-196b expression decreased during in vitro CD34+ differentiation; levels were higher in NPM1-mutant than NPM1-wildtype AML; in T-ALL, miR-196a/b expression associated with an immature immunophenotype and with CD34 and CD33 expression 3. ERG overexpression is an adverse prognostic factor in adult AML and T-ALL, so again miR-196b is repressing something the leukemia would prefer to have.
cKIT. The lab's brief listed cKIT as a miR-196b target. I could not find a primary paper establishing a miR-196b-KIT interaction in leukemia on PubMed and have therefore left it out rather than cite it. If it exists it is likely in a non-haematological context or in a review, and it should not be asserted in this graph until the primary source is identified.
The pattern across HOXA9, MEIS1, FAS, ERG and HOXB8 is that four of the five are genes whose loss should be bad for the leukemia. That is the single most interesting fact in this node.
Dependency or passenger? The honest answer
Both, in different senses, and the question as posed is malformed.
Passenger in origin. miR-196b sits between HOXA9 and HOXA10 inside the domain the fusion opens, and is co-regulated with them by wild-type MLL in normal development 1. Nothing about its activation requires a fusion-specific mechanism — it is what happens when the 5' HOXA domain goes on.
Functional, not inert. The antagomir replating result 1 and the transplantation phenotypes 4 both show it changes leukemia behaviour. It is not a bystander transcript.
Not a therapeutic dependency. No published experiment shows that removing miR-196b alone kills established KMT2A-r leukemia in vivo. The 1 result is an ex vivo colony assay with a family-level antagomir. And 4 shows the direction of effect reverses between primary and secondary transplant. A dependency you cannot reliably sign is not a target.
A good biomarker. A 500-fold expression difference in 20 MLL-rearranged versus other paediatric ALL 2, independent of fusion partner and maturation state, is a strong, robustly measurable, essentially binary marker. Combined with HOTAIRM1 it stratified 5-year OS in intermediate-risk AML at 24% vs 42% vs 70% 7. Diagnostic and MRD use is a far better fit for this molecule than target use.
Intervention read
miRNAs are, on paper, the most tractable non-coding class: LNA/antimiR chemistry is mature, anti-miR-122 (miravirsen) reached phase 2 in hepatitis C, and single-stranded antimiRs do not need a delivery vehicle in liver.
Despite that, miR-196b is a poor target here and the reason is biological, not chemical:
- Sign problem. Antagonising miR-196b should de-repress HOXA9, MEIS1 and ERG 3, 4. In a disease where the therapeutic objective is to lower HOXA9/MEIS1, that is the wrong direction. This is not a delivery or potency problem; it is a target-selection error.
- Family cross-reactivity. miR-196a-1, miR-196a-2 and miR-196b share the mature seed; any antimiR potent enough to matter will hit the family, and miR-196a has its own ERG and HOXB8 activity 3, 5.
- Direction reversal with disease stage. 4 predicts benefit at initiation and harm at maintenance, or vice versa depending on which arm dominates. A drug whose sign depends on disease stage cannot be trialled sensibly.
- The agonist direction (miR-196b mimic, to suppress HOXA9/MEIS1) is the mechanistically coherent one, and is exactly what 4 shows delays primary leukemogenesis — but the same paper shows it accelerates secondary disease by suppressing Fas, so it would be an unusually reckless thing to put into a child.
Verdict: LNA antimiR chemistry is available and would work technically; the target is wrong. Grade: weak as a target, strong as a diagnostic biomarker.
| element symbol | MIR196B |
|---|---|
| class | miRNA |
| genome build | GRCh38 |
| locus | chr7:27,169,480-27,169,563 |
| chromosome | 7 |
| start | 27169480 |
| end | 27169563 |
| strand | - |
| precursor length nt | 84 |
| cytoband | 7p15.2 |
| ensembl gene ID | ENSG00000283745 |
| ensembl canonical transcript | ENST00000384852 |
| mirbase accession | MI0001150 |
| rnacentral ID | URS000075D019 |
| hgnc ID | HGNC:31790 |
| entrez ID | 442920 |
| position in cluster | intragenic to the HOXA cluster, between the HOXA9 and HOXA10 coding regions, same strand as the HOXA protein-coding genes |
| direction of change in kmt2a r | up |
| dependency vs passenger | activated as part of the 5' HOXA domain (passenger in origin), functionally consequential (antagomir abolishes MLL-AF9 replating), but not a signable therapeutic dependency because its direction of effect reverses between primary and secondary transplantation and it represses HOXA9/MEIS1/ERG/FAS simultaneously |
mature species
[ "hsa-miR-196b-5p", "hsa-miR-196b-3p" ]
paralogues sharing seed
[ "MIR196A1 (chr17, HOXB cluster)", "MIR196A2 (chr12, HOXC cluster)" ]
validated targets — the numbers behind the chart
[
{
"gene": "HOXA9",
"direction": "repressed",
"pmid": "22353710",
"note": "direct target; repression delays primary MLL-fusion leukemogenesis",
"title": "miR-196b directly targets both HOXA9/MEIS1 oncogenes and FAS tumour suppressor in MLL-rearranged leukaemia.",
"authors": "Li Z, Huang H, Chen P, et al.",
"venue": "Nat Commun",
"year": 2012,
"title_provenance": "Title/authors/venue backfilled from PubMed esummary on 2026-09-20 because this citation stored a bare PMID with no title, which made it unscoreable by verify-citations.py. BACKFILLING IS NOT VERIFICATION: it confirms the PMID resolves to a real paper, not that this is the right paper for the claim. That still requires reading."
},
{
"gene": "MEIS1",
"direction": "repressed",
"pmid": "22353710",
"note": "direct target",
"title": "miR-196b directly targets both HOXA9/MEIS1 oncogenes and FAS tumour suppressor in MLL-rearranged leukaemia.",
"authors": "Li Z, Huang H, Chen P, et al.",
"venue": "Nat Commun",
"year": 2012,
"title_provenance": "Title/authors/venue backfilled from PubMed esummary on 2026-09-20 because this citation stored a bare PMID with no title, which made it unscoreable by verify-citations.py. BACKFILLING IS NOT VERIFICATION: it confirms the PMID resolves to a real paper, not that this is the right paper for the claim. That still requires reading."
},
{
"gene": "FAS",
"direction": "repressed",
"pmid": "22353710",
"note": "proapoptotic; FAS overexpression reverses the miR-196b phenotype",
"title": "miR-196b directly targets both HOXA9/MEIS1 oncogenes and FAS tumour suppressor in MLL-rearranged leukaemia.",
"authors": "Li Z, Huang H, Chen P, et al.",
"venue": "Nat Commun",
"year": 2012,
"title_provenance": "Title/authors/venue backfilled from PubMed esummary on 2026-09-20 because this citation stored a bare PMID with no title, which made it unscoreable by verify-citations.py. BACKFILLING IS NOT VERIFICATION: it confirms the PMID resolves to a real paper, not that this is the right paper for the claim. That still requires reading."
},
{
"gene": "ERG",
"direction": "repressed",
"pmid": "20570349",
"note": "3'UTR luciferase plus overexpression only; no antimiR confirmation",
"title": "The role of microRNA-196a and microRNA-196b as ERG regulators in acute myeloid leukemia and acute T-lymphoblastic leukemia.",
"authors": "Coskun E, von der Heide EK, Schlee C, et al.",
"venue": "Leuk Res",
"year": 2011,
"title_provenance": "Title/authors/venue backfilled from PubMed esummary on 2026-09-20 because this citation stored a bare PMID with no title, which made it unscoreable by verify-citations.py. BACKFILLING IS NOT VERIFICATION: it confirms the PMID resolves to a real paper, not that this is the right paper for the claim. That still requires reading."
},
{
"gene": "HOXB8",
"direction": "cleaved",
"pmid": "15105502",
"note": "family-level (miR-196), slicer-mode cleavage",
"title": "MicroRNA-directed cleavage of HOXB8 mRNA.",
"authors": "Yekta S, Shih IH, Bartel DP",
"venue": "Science",
"year": 2004,
"title_provenance": "Title/authors/venue backfilled from PubMed esummary on 2026-09-20 because this citation stored a bare PMID with no title, which made it unscoreable by verify-citations.py. BACKFILLING IS NOT VERIFICATION: it confirms the PMID resolves to a real paper, not that this is the right paper for the claim. That still requires reading."
}
]targets asserted but not verified
[ "KIT / cKit — no primary PubMed source found in a leukemia context; deliberately omitted from evidence" ]
cohorts with direction evidence — the numbers behind the chart
[
{
"cohort": "Erasmus MC / DCOG paediatric ALL: 20 MLL-rearranged, 15 T-ALL, 57 other precursor B-ALL",
"finding": "~500-fold higher in MLL-rearranged and ~800-fold higher in 5/15 T-ALL vs remaining precursor B-ALL (P<0.001); independent of MLL fusion partner and maturation status",
"pmid": "18923441",
"n": 92,
"title": "Identification of new microRNA genes and aberrant microRNA profiles in childhood acute lymphoblastic leukemia.",
"authors": "Schotte D, Chau JC, Sylvester G, et al.",
"venue": "Leukemia",
"year": 2009,
"title_provenance": "Title/authors/venue backfilled from PubMed esummary on 2026-09-20 because this citation stored a bare PMID with no title, which made it unscoreable by verify-citations.py. BACKFILLING IS NOT VERIFICATION: it confirms the PMID resolves to a real paper, not that this is the right paper for the claim. That still requires reading."
},
{
"cohort": "55 primary leukemia samples",
"finding": "overexpression specific to MLL-associated leukemias",
"pmid": "19188669",
"n": 55,
"title": "Regulation of mir-196b by MLL and its overexpression by MLL fusions contributes to immortalization.",
"authors": "Popovic R, Riesbeck LE, Velu CS, et al.",
"venue": "Blood",
"year": 2009,
"title_provenance": "Title/authors/venue backfilled from PubMed esummary on 2026-09-20 because this citation stored a bare PMID with no title, which made it unscoreable by verify-citations.py. BACKFILLING IS NOT VERIFICATION: it confirms the PMID resolves to a real paper, not that this is the right paper for the claim. That still requires reading."
},
{
"cohort": "GMALL adult AML and T-ALL",
"finding": "higher in NPM1-mutant AML than NPM1-wildtype; in T-ALL associated with immature immunophenotype, CD34 and CD33",
"pmid": "20570349",
"n": "not stated in abstract",
"title": "The role of microRNA-196a and microRNA-196b as ERG regulators in acute myeloid leukemia and acute T-lymphoblastic leukemia.",
"authors": "Coskun E, von der Heide EK, Schlee C, et al.",
"venue": "Leuk Res",
"year": 2011,
"title_provenance": "Title/authors/venue backfilled from PubMed esummary on 2026-09-20 because this citation stored a bare PMID with no title, which made it unscoreable by verify-citations.py. BACKFILLING IS NOT VERIFICATION: it confirms the PMID resolves to a real paper, not that this is the right paper for the claim. That still requires reading."
}
]intervention assessment
{
"tractability": "weak as a target; strong as a biomarker",
"chemistry_available": "yes — LNA/antimiR and miRNA-mimic chemistry are mature (cf. miravirsen/anti-miR-122 reaching phase 2)",
"best_modality": "none recommended therapeutically. LNA antimiR is the obvious chemistry but has the wrong predicted sign.",
"why_not": "antagonising miR-196b should de-repress HOXA9, MEIS1 and ERG — the opposite of the therapeutic objective in KMT2A-r leukemia; the mimic direction suppresses HOXA9/MEIS1 but also suppresses FAS and accelerated secondary leukemogenesis in mouse",
"family_cross_reactivity": "miR-196a-1 and miR-196a-2 share the mature seed; element-specific antagonism is not achievable with seed-directed chemistry",
"biomarker_value": "high — an essentially on/off, fusion-partner-independent marker of KMT2A rearrangement in paediatric ALL, with the caveat that HOXA-high T-ALL also scores positive",
"first_experiment": "measure miR-196b under menin inhibition in KMT2A::AFF1 cells and PDX. If miR-196b falls with HOXA9, it is a candidate pharmacodynamic/MRD marker for revumenib response; if it persists, it identifies a residual HOXA-domain activity the drug does not reach."
}- Sign inversion: an anti-miR-196b agent would be expected to raise HOXA9, MEIS1 and ERG, directly opposing menin inhibition. Combining the two could be antagonistic.
- Family cross-reactivity: seed-directed antimiRs cannot separate miR-196b from miR-196a-1/a-2, which are expressed from the HOXB and HOXC clusters, so off-target HOX effects are built into the modality.
- Essential-function toxicity: miR-196b is most abundant in short-term HSCs and falls with differentiation, and targeting Hoxa9/Meis1/Fas by miR-196b is described as probably important for normal haematopoiesis, so a potent antagonist perturbs normal stem-cell regulation.
- Stage-dependent reversal: the primary-versus-secondary transplant discordance means a therapy's direction of benefit could flip between diagnosis and relapse, which is the worst possible property for a paediatric trial design.
- Biomarker failure mode: HOXA-high T-ALL scores 800-fold positive, so miR-196b cannot distinguish KMT2A-r from other HOXA-high disease — exactly the discrimination needed in MPAL and in lineage-switch relapse after CD19-directed therapy.
- Does menin inhibition switch miR-196b off? Nobody has reported miR-196b levels under revumenib or ziftomenib. If it tracks HOXA9 it is a cheap pharmacodynamic and MRD marker; if it does not, it marks residual fusion activity the drug misses.
- How can miR-196b be simultaneously necessary for MLL-AF9 immortalization (antagomir abolishes replating) and a repressor of HOXA9/MEIS1 whose forced expression delays primary leukemogenesis? The field has left this contradiction unreconciled for over a decade, and resolving it would clarify whether the HOXA9 3'UTR site is used at endogenous miR-196b levels at all.
- Is FAS repression by miR-196b the mechanism of the immune evasion and apoptotic resistance seen in KMT2A-r infant ALL? This connects a non-coding element to a clinically central phenotype and is testable with FAS restoration in KMT2A::AFF1 PDX.
- In KMT2A::AFF1 B-ALL specifically — as opposed to MLL-AF9 AML — is miR-196b required for maintenance? Every functional experiment is myeloid.
- Does miR-196b's slicer-mode capability (from the HOXB8 precedent) mean it has additional near-perfect-site targets in the B-lymphoid transcriptome that standard seed-based prediction misses?
- E1strong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.paper
Wild-type MLL regulates mir-196b in a pattern similar to Hoxa9 and Hoxa10 during ES-cell differentiation; mir-196b is most abundant in short-term HSCs; leukemogenic MLL fusion proteins overexpress it; a miR-196-specific antagomir abrogated the replating potential of MLL-AF9-transformed bone-marrow cells; and overexpression was specific to MLL-associated leukemias across 55 primary leukemia samples.
Regulation of mir-196b by MLL and its overexpression by MLL fusions contributes to immortalization · Popovic R, Riesbeck LE, Velu CS, Chaubey A, Zhang J, Achille NJ, Erfurth FE, Eaton K, Lu J, Grimes HL, Chen J, Rowley JD, Zeleznik-Le NJ · Blood 113(14):3314-22 2009What this evidence cannot show
The dependency claim rests on an ex vivo methylcellulose replating assay, a surrogate for self-renewal, with an antagomir that targets miR-196 at the family level and so does not distinguish miR-196b from miR-196a. No in vivo antagomir experiment. The 55 primary samples are not broken down by fusion partner or by ALL/AML in the abstract. MLL-AF9 is a myeloid model; KMT2A::AFF1 B-ALL was not tested.
Evidence that argues against this (1)
- Forced miR-196b expression DELAYS MLL-fusion leukemogenesis in primary bone-marrow transplantation because miR-196b directly represses Hoxa9 and Meis1, which is the opposite polarity to 'miR-196b contributes to immortalization'. The two results can be reconciled only by invoking stage-dependent effects. Li Z et al. 2012
- E2strong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.paper
In paediatric ALL, miR-196b expression was approximately 500-fold higher in 20 MLL-rearranged cases and 800-fold higher in 5 of 15 T-ALL cases compared with the remaining precursor B-ALL cases (P<0.001), and expression did not correlate with maturation status by immunoglobulin/T-cell-receptor rearrangement or immunophenotype, nor with MLL fusion partner; eight miRNAs were differentially expressed between MLL and non-MLL precursor B-ALL (P<0.05).
Identification of new microRNA genes and aberrant microRNA profiles in childhood acute lymphoblastic leukemia · Schotte D, Chau JCK, Sylvester G, Liu G, Chen C, van der Velden VHJ, Broekhuis MJC, Peters TCJM, Pieters R, den Boer ML · Leukemia 23(2):313-22 2009What this evidence cannot show
Fold-changes of 500-800x on qPCR against a near-zero baseline are partly an artefact of the denominator: the comparator precursor B-ALL cases express almost no miR-196b, so the ratio is unstable even though the qualitative on/off distinction is robust. n=20 MLL-rearranged is small and fusion partners are not enumerated. Single centre (Erasmus MC/DCOG). The 'did not correlate with fusion partner' conclusion is drawn from a subset of 20 and is underpowered to exclude partner effects.
Evidence that argues against this (1)
- The 800-fold elevation in a third of T-ALL cases shows miR-196b is a readout of HOXA-cluster activation rather than of KMT2A rearrangement specifically, so it cannot serve as a KMT2A-r-specific marker in a mixed-lineage or immature phenotype setting — which is precisely where MPAL and lineage-switch cases live. Coskun E et al. 2011
- E3moderate confidence 3 of 5: One strong study, or several smaller consistent ones.paper
Transfection of miR-196a and miR-196b precursors induced ERG downregulation and luciferase assays confirmed binding of both to the ERG 3'UTR; miR-196b expression decreased during in vitro differentiation of CD34+ cells; NPM1-mutant AML had higher miR-196a/b than NPM1-wildtype; in T-ALL miR-196a/b expression associated with an immature immunophenotype and with CD34 and CD33 expression.
The role of microRNA-196a and microRNA-196b as ERG regulators in acute myeloid leukemia and acute T-lymphoblastic leukemia · Coskun E, von der Heide EK, Schlee C, Kühnl A, Gökbuget N, Hoelzer D, Hofmann WK, Thiel E, Baldus CD · Leukemia Research 35(2):208-13 2011What this evidence cannot show
Target validation is by precursor overexpression plus 3'UTR luciferase, the weakest acceptable standard: it shows the site can be used when the miRNA is supraphysiological, not that it is used endogenously. No loss-of-function (antimiR) confirmation of ERG de-repression. Adult AML and T-ALL cohorts (GMALL); no KMT2A-r stratum and no paediatric or infant data. The seed is shared between miR-196a and miR-196b so the two cannot be attributed separately by this design.
Evidence that argues against this (1)
- miR-196a and miR-196b share a seed sequence, so a 3'UTR luciferase reporter cannot attribute repression to one rather than the other, and precursor transfection delivers a supraphysiological dose that recruits targets not repressed at endogenous levels. The NPM1-mutant and T-ALL associations are from different diseases again. Ensembl, EMBL-EBI 2026
- E4strong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.paper
miR-196b directly targets HOXA9 and MEIS1 as well as the proapoptotic FAS gene; forced miR-196b expression significantly delayed MLL-fusion-mediated leukemogenesis in primary bone-marrow transplantation through suppression of Hoxa9/Meis1, yet caused more aggressive phenotypes and much faster leukemogenesis in secondary transplantation via further repression of Fas, and FAS overexpression significantly inhibited leukemogenesis and reversed the miR-196b-mediated phenotypes.
miR-196b directly targets both HOXA9/MEIS1 oncogenes and FAS tumour suppressor in MLL-rearranged leukaemia · Li Z, Huang H, Chen P, He M, Li Y, Arnovitz S, Jiang X, He C, Hyjek E, Zhang J, Zhang Z, Elkahloun A, Cao D, Shen C, Wunderlich M, Wang Y, Neilly MB, Jin J, Wei M, Lu J, Valk PJM, Delwel R, Lowenberg B, Le Beau MM, Vardiman J, Mulloy JC, Zeleznik-Le NJ, Liu PP, Zhang J, Chen J · Nature Communications 3:688 2012What this evidence cannot show
All in vivo work is retroviral forced overexpression in mouse bone marrow, which puts miR-196b well above physiological levels and is not the same experiment as perturbing the endogenous locus. The primary-versus-secondary reversal is striking but rests on a single set of transplant series; secondary-transplant phenotypes are notoriously sensitive to clonal selection during the primary passage, so the acceleration could reflect selection rather than a direct Fas mechanism. A publisher correction was issued (PMID 29633759) and should be read alongside the paper. Myeloid MLL-fusion models only; no KMT2A::AFF1 B-lymphoid model.
Evidence that argues against this (1)
- The earlier and more widely cited result is that a miR-196 antagomir abolishes the replating potential of MLL-AF9-transformed cells, i.e. that miR-196b function is NECESSARY for MLL-fusion immortalization. That is hard to square with miR-196b repressing HOXA9 and MEIS1, and the two papers have not been formally reconciled. Popovic R et al. 2009
- E5established confidence 5 of 5: Multiple independent lines of evidence; treated as settled in the field.paper
miR-196 directs cleavage of HOXB8 mRNA, establishing that a vertebrate microRNA can act through Argonaute-mediated slicing of a near-perfectly complementary target rather than only through translational repression.
MicroRNA-directed cleavage of HOXB8 mRNA · Yekta S, Shih IH, Bartel DP · Science 304(5670):594-6 2004What this evidence cannot show
Establishes the HOXB8 site for the miR-196 family, not specifically for miR-196b versus miR-196a (they share the mature seed and the relevant complementarity). No leukemia context; the work is developmental/biochemical. HOXB8's relevance to KMT2A-r leukemia is not established.
Evidence that argues against this (1)
- HOXB8 cleavage is the textbook demonstration that a vertebrate microRNA CAN slice a near-perfectly complementary target, and near-perfect complementarity is rare: most animal microRNA targets, including the HOXA-cluster messages this beat cares about, are seed-matched and repressed translationally. The mechanism does not generalise to the interactions the entry needs it for. Ensembl, EMBL-EBI 2026
- E6established confidence 5 of 5: Multiple independent lines of evidence; treated as settled in the field.database
MIR196B is ENSG00000283745, miRBase accession MI0001150, RNAcentral URS000075D019, HGNC:31790, Entrez 442920, cytoband 7p15.2, GRCh38 chr7:27,169,480-27,169,563 on the minus strand — lying between HOXA9 (chr7:27,162,438-27,175,180, minus strand) and HOXA10 (chr7:27,170,592-27,180,261, minus strand).
HGNC REST API record for MIR196B and Ensembl REST API gene lookups (MIR196B, HOXA9, HOXA10), assembly GRCh38 · HUGO Gene Nomenclature Committee; Ensembl / EMBL-EBI · HGNC / Ensembl 2026What this evidence cannot show
The long HOXA9 gene model extends past the MIR196B coordinates, so 'between HOXA9 and HOXA10' is true of the canonical HOXA9 coding region but the hairpin formally lies inside the extended HOXA9 transcriptional unit. Coordinates are for the 84-nt precursor hairpin; the mature miR-196b-5p/-3p coordinates are a subset. Genome annotation changes between Ensembl releases.
Evidence that argues against this (1)
- The coordinates locate MIR196B between HOXA9 and HOXA10 on the same strand, which means its transcription cannot be separated from HOXA-cluster transcription by position alone. In KMT2A-rearranged leukaemia the whole cluster is driven, so miR-196b levels are expected to rise whether or not the microRNA does anything. Ensembl, EMBL-EBI 2026
- E7moderate confidence 3 of 5: One strong study, or several smaller consistent ones.paper
miR-196b was part of a 33-microRNA signature associated with HOTAIRM1 expression in AML, and the combination of miR-196b and HOTAIRM1 expression stratified 5-year overall survival in intermediate-risk AML at 24% vs 42% vs 70% (P=0.004).
The lincRNA HOTAIRM1, located in the HOXA genomic region, is expressed in acute myeloid leukemia, impacts prognosis in patients in the intermediate-risk cytogenetic category, and is associated with a distinctive microRNA signature · Díaz-Beyá M, Brunet S, Nomdedéu J, Pratcorona M, Cordeiro A, Gallardo D, Escoda L, Tormo M, Heras I, Ribera JM, Duarte R, Queipo de Llano MP, Bargay J, Sampol A, Nomdedeu M, Risueño RM, Hoyos M, Sierra J, Monzo M, Navarro A, Esteve J · Oncotarget 6(31):31613-27 2015What this evidence cannot show
Retrospective adult CETLAM AML cohort restricted to intermediate-risk cytogenetics, a stratum that largely excludes KMT2A-rearranged AML, so the three-tier survival split cannot be transferred to KMT2A-r disease. Published in Oncotarget. No validation cohort. Three-group stratification derived and tested in the same data.
Evidence that argues against this (1)
- A 33-microRNA signature and a three-way survival split derived in one cohort is a model with many degrees of freedom and no stated independent validation; P = 0.004 across three groups defined by two correlated co-expressed transcripts from the same locus is close to a single variable measured twice. Ensembl, EMBL-EBI 2026
- part of →Step 5 — The output program: HOXA9/HOXA10/MEIS1/PBX3 plus MEF2C, MYB, BCL2, FLT3 and PROM1/CD133
encoded within the HOXA cluster and directly switched on by the fusion
HOXA-cluster microRNA, a direct KMT2A-fusion target read out of the driven locus
both are HOXA-cluster transcripts co-activated by the fusion; neither is independent of HOXA dosage