Niche-mediated chemoprotection in KMT2A-rearranged leukaemia — real for cytarabine, unsupported for menin inhibitors, and the one hypoxia experiment points the other way
also called environment-mediated drug resistance · stromal protection · CAM-DR (cell adhesion mediated drug resistance)
Leukaemia cells sitting against bone-marrow support cells survive chemotherapy better than the same cells growing alone, and in this particular leukaemia the effect is stronger than in other childhood leukaemias. But 'the marrow protects the cells' is not a general licence: for the newest drugs in this disease, the menin inhibitors, there is no evidence of it, and the one experiment that tested low oxygen found it made the cells easier to kill, not harder.
The same thing, for a scientist
Niche-mediated chemoprotection is demonstrated in KMT2A-rearranged disease and its scope is narrower than it is usually stated. **Established:** direct contact between AML cells and marrow components mediates chemoprotection in **KMT2A-rearranged paediatric AML** specifically, modulated by stromal, endothelial and mesenchymal stem cells and the extracellular matrix, and azacitidine plus panobinostat synergistically sensitises MV4;11 and KMT2A-rearranged paediatric PDX lines to cytarabine in multicell co-culture, reduces leukaemic association with the monolayer and ECM, increases mobilization from marrow in vivo, and improves chemotherapy efficacy in vivo when given as pretreatment [E1]. In infant KMT2A-rearranged **ALL**, stroma differentially protects relative to non-rearranged ALL and CXCR4 antagonism reverses it (recorded in `mechanism-kmt2a-r-tissue-localization`). The mechanism is repeatedly **metabolic**: nestin+ BMSCs supply OXPHOS and glutathione-mediated antioxidant defence [E2]; adipocyte leptin drives complex I and a compensatory antioxidant programme [E3]. **Not established:** protection against menin inhibitors, which the resistance beat rejected as a candidate because no primary study supports it. **Contradicted:** hypoxic protection — hypoxia induction **sensitised** KMT2A-rearranged AML to venetoclax plus MI-503 [E4].
What is demonstrated, in what drug, in what disease
The honest table:
| claim | drug | disease | status |
|---|---|---|---|
| stroma protects, reversible by CXCR4 antagonism | lestaurtinib, cytarabine | infant KMT2A-r ALL | demonstrated in co-culture and xenograft |
| direct contact with BM components mediates chemoprotection | cytarabine | KMT2A-r paediatric AML | demonstrated in multicell co-culture and in vivo 1 |
| mesenchymal metabolic support (OXPHOS, glutathione) | chemotherapy generally | MLL-AF9 murine AML | demonstrated 2 |
| adipocyte leptin/LEPR metabolic support | cytarabine | AML incl. MLL-AF9 | demonstrated 2026, unreplicated 3 |
| niche protection against menin inhibitors | revumenib, ziftomenib etc. | KMT2A-r | no primary study — 216 menin-inhibitor records against 543,067 niche records intersect in 9, all read, none testing it |
| hypoxic protection | venetoclax + MI-503 | KMT2A-r AML | contradicted — hypoxia sensitised 4 |
The last two rows are the reason this entry exists in this form. A beat that wrote 'the niche protects KMT2A-rearranged leukaemia from therapy' as an unqualified claim would be writing against the data on the two questions the lab most cares about.
The one KMT2A-specific chemoprotection study, and what it actually did
Lehner and colleagues built a multicell co-culture — stromal, endothelial and mesenchymal stem cells plus extracellular matrix — and showed that direct contact between AML cells and marrow components mediates chemoprotection. They then showed that azacitidine plus panobinostat synergistically sensitises MV4;11 and KMT2A-rearranged paediatric patient-derived xenograft lines to cytarabine in that co-culture. The epigenetic combination reduced leukaemic association with the multicell monolayer and with ECM in vitro and increased mobilization of leukaemic cells from marrow in vivo, and pretreatment with the combination improved chemotherapy efficacy in vivo 1.
That is an adhesion-directed result achieved with epigenetic drugs rather than with an adhesion inhibitor, which is unusual and worth noting: the handle on the niche here is a hypomethylating agent plus an HDAC inhibitor, both of which this graph already tracks in other contexts.
Cell-line identity. MV4;11 carries KMT2A::AFF1 with FLT3-ITD and is Cellosaurus CVCL_0064. This entry does not assert a Cellosaurus verification it did not perform; the identity and lesion status of MV4;11 should be confirmed against the accession by whoever builds on this, in line with the standing rule that a comparator arm must be screened for pathway-equivalent lesions (PICALM::MLLT10, NUP98 fusions, NPM1c and other HOXA/MEIS1 drivers) and not only for KMT2A rearrangement.
The hypoxia result, and why the graph must keep it in front
In KMT2A-rearranged AML, hypoxia induces HDAC9; HDAC9 is indispensable for KMT2A-rearranged AML proliferation; venetoclax plus a menin inhibitor represses HIF-1A and thereby HDAC9; and hypoxia induction sensitised KMT2A-rearranged AML to venetoclax plus MI-503, both for proliferation inhibition and apoptosis induction 4.
This was already recorded by the resistance beat as a rejected candidate, with the note that a hypoxia-protection entry 'would have been written against the data'. This beat confirms the record by fetching the paper and restates it here because the niche literature's default framing — low oxygen, dormancy, protection — would otherwise reassert itself through the back door of a marrow-niche beat.
It also generates a prediction worth testing rather than assuming. Direct pO2 measurement puts the marrow's lowest oxygen in the deep peri-sinusoidal compartment (concept-perivascular-sinusoidal-niche). If hypoxia sensitises, then that compartment should be where a venetoclax plus menin-inhibitor combination clears disease best. Nobody has looked, and a spatially resolved response readout in a xenograft would answer it.
| mechanism class | environment-mediated drug resistance |
|---|---|
| recurring mechanism | metabolic and redox buffering (OXPHOS, glutathione, complex I, CXCL12-dependent ROS control) rather than adhesion-only anti-apoptotic signalling |
| cell line identity note | MV4;11 is used in E1 and was NOT verified against Cellosaurus by accession in this beat; whoever builds on this must verify, and must screen any comparator group for pathway-equivalent lesions (PICALM::MLLT10, NUP98 fusions, NPM1c and other HOXA/MEIS1 drivers), not only for KMT2A rearrangement |
demonstrated against
[
{
"drug": "cytarabine",
"setting": "KMT2A-r paediatric AML multicell co-culture and in vivo",
"source_evidence": "E1"
},
{
"drug": "lestaurtinib and cytarabine",
"setting": "infant KMT2A-r ALL stromal co-culture and xenograft",
"source_evidence": "see mechanism-kmt2a-r-tissue-localization"
},
{
"drug": "cytarabine",
"setting": "marrow leptin/LEPR, AML including MLL-AF9",
"source_evidence": "E3"
}
]not demonstrated against
[ "menin inhibitors (revumenib, ziftomenib, bleximenib, enzomenib) - no primary study; controlled intersection re-run in this beat gives 216 menin-inhibitor records x 543,067 niche records = 9, titles all read, none testing niche protection against a menin inhibitor" ]
contradicted
[
{
"claim": "hypoxic niche protects KMT2A-rearranged AML",
"finding": "hypoxia induction SENSITISED to venetoclax plus MI-503",
"source_evidence": "E4"
}
]pharmacological handles reported
[ "azacitidine plus panobinostat (reduces adhesion, mobilizes cells, improves chemotherapy efficacy)", "CXCR4 antagonism (plerixafor, POL5551)", "LEPR antagonism (Allo-aca, research peptide)" ]
atlas refs
[
{
"label": "BM microenvironment-induced chemoprotection in KMT2A-r paediatric AML",
"pmid": "37370721",
"title": "Bone Marrow Microenvironment-Induced Chemoprotection in KMT2A Rearranged Pediatric AML Is Overcome by Azacitidine-Panobinostat Combination.",
"authors": "Lehner KM, Gopalakrishnapillai A, Kolb EA, et al.",
"venue": "Cancers (Basel)",
"year": 2023,
"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."
},
{
"label": "Hypoxia SENSITISES KMT2A-r AML to venetoclax plus menin inhibitor",
"pmid": "38053201",
"title": "Repressing HIF-1α-induced HDAC9 contributes to the synergistic effect of venetoclax and MENIN inhibitor in KMT2Ar AML.",
"authors": "Ling Q, Zhou Y, Qian Y, et al.",
"venue": "Biomark Res",
"year": 2023,
"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."
}
]- Mobilising leukaemic cells out of the niche to sensitise them raises circulating blast counts in a disease that already presents with hyperleukocytosis and leukostasis risk.
- Every agent that reverses niche protection also strips the patient's normal stem cells of the same protection, during a period when those stem cells are the only route back to functioning marrow.
- If niche protection is redox buffering, then antioxidant-containing supportive care could phenocopy the niche and blunt a chemotherapy dose - an interaction nobody appears to have looked for.
- Claiming niche protection against menin inhibitors without a primary study is precisely the error the resistance beat rejected; this entry must not be cited as licensing that claim.
- Does the marrow niche protect KMT2A-rearranged cells from a menin inhibitor? The experiment is a stromal co-culture with revumenib and a viability readout, it would take a week, and its absence is the largest single gap in this beat.
- If hypoxia sensitises to venetoclax plus a menin inhibitor, does the combination clear the deep peri-sinusoidal compartment preferentially? A spatially resolved response readout in a xenograft would test it.
- Does azacitidine plus panobinostat reduce niche adhesion in KMT2A-rearranged ALL as it does in AML, and is the effect separable from its direct cytotoxicity?
- Do the redox-buffering and the hypoxia-sensitisation literatures make opposite predictions because they used different drugs, or because one of them is wrong? Running cytarabine and venetoclax-plus-menin-inhibitor side by side under the same oxygen conditions would settle it.
- E1strong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.paper
In KMT2A-rearranged paediatric AML, direct contact between AML cells and bone-marrow components mediates chemoprotection modulated by stromal, endothelial and mesenchymal stem cells and the extracellular matrix; azacitidine and panobinostat synergistically sensitise MV4;11 cells and KMT2A-rearranged paediatric patient-derived xenograft lines to cytarabine in multicell co-culture; the epigenetic drug combination reduces leukaemic cell association with the multicell monolayer and ECM in vitro and increases mobilization of leukaemic cells from the bone marrow in vivo; and pretreatment with the combination improves the efficacy of chemotherapy in vivo.
Bone Marrow Microenvironment-Induced Chemoprotection in KMT2A Rearranged Pediatric AML Is Overcome by Azacitidine-Panobinostat Combination · Lehner KM, Gopalakrishnapillai A, Kolb EA, Barwe SP · Cancers (Basel) 2023What this evidence cannot show
Cell lines plus PDX in a reconstructed multicell co-culture, which is an in vitro approximation of marrow architecture. MV4;11 is an adult-derived line carrying KMT2A::AFF1 with FLT3-ITD; its Cellosaurus identity was NOT verified by accession in this beat. The clinical partner drugs are cytarabine and an epigenetic combination, not menin inhibitors. Panobinostat's paediatric development has been limited by toxicity. No untreated-niche comparator arm screened for pathway-equivalent non-KMT2A lesions is reported in the abstract. Read: abstract only.
Evidence that argues against this (1)
- Niche-mediated protection does not extend to menin inhibitors on current evidence, and the absence was re-tested in this beat with BOTH halves counted rather than inherited. Disease half `(menin inhibitor OR menin inhibition OR revumenib OR ziftomenib OR bleximenib OR MI-503 OR VTP-50469)[tiab]` = 216 records; niche half `(bone marrow stroma OR stromal OR mesenchymal OR co-culture OR microenvironment OR niche)[tiab]` = 543,067 records; intersection = 9 records, whose titles were all read. None tests stromal or niche protection against a menin inhibitor: they are a GIST paper where 'stromal' means gastrointestinal stromal tumour, renal fibrosis, urologic cancers, two reviews, a differentiation-syndrome proteomics paper, bleximenib immune evasion, CDK9 synergy in infant leukaemia, and the 2026 resistance review that lists the category without a primary study. Generalising this cytarabine result to the drug class the lab is developing would repeat an error this project has already catalogued. Counts run 2026-09-19. NCBI E-utilities 2026
- E2strong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.paper
In MLL-AF9-driven AML in vivo, nestin+ bone-marrow mesenchymal stem cell numbers are not reduced while bulk stroma is, their function changes to support AML cells at the expense of non-mutated HSCs, nestin+ cell depletion delays leukaemogenesis and selectively decreases AML but not normal cells in chimeric mice, and nestin+ BMSCs support AML survival and chemotherapy relapse through increased oxidative phosphorylation, TCA cycle activity and glutathione-mediated antioxidant defence.
Bone Marrow Mesenchymal Stem Cells Support Acute Myeloid Leukemia Bioenergetics and Enhance Antioxidant Defense and Escape from Chemotherapy · Forte D, Garcia-Fernandez M, Sanchez-Aguilera A, Stavropoulou V, Fielding C, Martin-Perez D, Lopez JA, Costa ASH, et al. · Cell Metabolism 2020What this evidence cannot show
Mouse MLL-AF9, nestin-GFP-based identification and depletion, with the reporter-identity caveat that runs through this whole literature. Myeloid, adult. 'Chemotherapy relapse' is a model readout, not a clinical endpoint. Read: abstract only.
Evidence that argues against this (1)
- A redox-buffering account of niche protection makes the wrong prediction about the one oxidative-stress manipulation performed in this genotype: hypoxia induction SENSITISED KMT2A-rearranged AML to venetoclax plus MI-503, and the combination works partly by repressing HIF-1A and its target HDAC9. If adaptation to oxidative stress protected these cells, that experiment should have gone the other way. Read: abstract only. Ling Q et al. 2023
- E3moderate confidence 3 of 5: One strong study, or several smaller consistent ones.paper
Elevated marrow leptin and blast LEPR associate with poor cytarabine clearance and reduced survival in newly diagnosed AML; exogenous leptin blunts cytarabine cytotoxicity in human AML lines, primary blasts and two syngeneic mouse models including MLL-AF9, while the high-affinity LEPR antagonist Allo-aca restores chemosensitivity without altering baseline leukaemia growth; leptin upregulates LEPR and triggers JAK2/STAT3 signalling raising mitochondrial complex I activity, oxidative phosphorylation and mitochondrial ROS, and the mtROS surge activates a compensatory antioxidant programme that shields blasts from drug-induced oxidative damage.
Marrow leptin-LEPR signaling rewires mitochondrial oxidative metabolism to confer chemoresistance in acute myeloid leukemia · Liao X, Dai W, Xu X, Cai D, Tan M, Wang Z, Huang Y, Hou D, et al. · Cell Death and Disease 2026What this evidence cannot show
2026 paper, unreplicated. Results from the MLL-AF9 and AML1-ETO9a models are not separated in the abstract, so the KMT2A-specific effect size is unknown. Adults. Allo-aca is a research peptide. Infants have minimal marrow adipose tissue, so the human relevance to this graph's population is doubtful. Read: abstract only.
Evidence that argues against this (1)
- Marrow adipocytes are predominantly NEGATIVE regulators of haematopoiesis, and reducing marrow adiposity accelerates engraftment after irradiation. A compartment that suppresses normal blood formation and supports leukaemic chemoresistance cannot be managed by a single directional intervention, and the net effect of manipulating marrow fat in a patient with residual disease is unknown. Read: abstract only. Naveiras O et al. 2009
- E4moderate confidence 3 of 5: One strong study, or several smaller consistent ones.paper
Hypoxia induces HDAC9 expression in KMT2A-rearranged AML; HDAC9 is indispensable for KMT2A-rearranged AML proliferation and its repression contributes to the proliferation inhibition produced by venetoclax plus a menin inhibitor; venetoclax plus MEN1 inhibitor inhibits the hypoxia pathway, especially HIF-1A, and its target HDAC9; and hypoxia induction SENSITISED KMT2A-rearranged AML to venetoclax plus MI-503-mediated proliferation inhibition and apoptosis induction.
Repressing HIF-1alpha-induced HDAC9 contributes to the synergistic effect of venetoclax and MENIN inhibitor in KMT2Ar AML · Ling Q, Zhou Y, Qian Y, Qian J, Zhang Y, Wang J, Zhu Y, Zhou Y, et al. · Biomarker Research 2023What this evidence cannot show
PubMed record is a Letter. Cell lines, primary ex vivo cells and a MOLM-13 xenograft; hypoxia is a culture condition, not a measured marrow compartment, so the inference to the perisinusoidal region is this entry's and not the paper's. Adult-derived myeloid lines; MI-503 is a tool compound, not the clinical menin inhibitors. Read: abstract only.
Evidence that argues against this (1)
- Three independent niche compartments protect KMT2A-rearranged or MLL-AF9 leukaemia by buffering oxidative stress - Prx1+ mesenchymal CXCL12 controlling LSC redox, nestin+ BMSC glutathione and OXPHOS transfer, and adipocyte leptin driving complex I with a compensatory antioxidant programme. Those results predict that a hypoxic, oxidative-stress-adapted state should be protective, which is the opposite of the sensitisation reported here. The two literatures have never been tested against each other, and neither has run the other's drug. Read: abstract only. Vinado AC et al. 2022
distinct claims kept apart: niche chemoprotection concerns whether hypoxia shields cells from drugs (contradicted in KMT2Ar AML), this entry concerns whether the hypoxia programme is itself a dependency
protection is conferred by direct contact with stromal, endothelial and mesenchymal niche cells and ECM
- confers resistance to →KMT2A-rearranged acute myeloid leukaemia in children and infants
niche contact protects KMT2A-rearranged paediatric AML from cytarabine; azacitidine plus panobinostat overcomes it
hypoxia SENSITISES KMT2A-r AML to venetoclax plus a menin inhibitor, contradicting a hypoxic-protection account
- depends on →Nestin+ mesenchymal stem cell — the niche cell that MLL-AF9 leukaemia wakes up and then loses
nestin+ BMSCs supply OXPHOS and glutathione antioxidant defence enabling chemotherapy escape
marrow leptin acting on blast LEPR blunts cytarabine cytotoxicity via complex I and an antioxidant programme
the state through which niche protection is usually explained; the chemoprotection here is metabolic rather than cell-cycle-based
the only completed paediatric clinical test of reversing niche-mediated chemoprotection
contradicts a hypoxic-sanctuary account of niche protection in this genotype
natalizumab potentiated standard-of-care chemotherapy in KMT2A-r B-ALL PDX, the combination effect niche disruption predicts
reframes the documented chemoprotection as metabolic and post-treatment rather than dormancy-based
extends the documented cytarabine chemoprotection to the menin-inhibitor class
redox and energy-balance arm of niche chemoprotection in MLL::AF9
CXCR4 blockade reverses stromal chemoprotection in MLL-rearranged ALL
leptin-LEPR JAK2/STAT3 raises OXPHOS and mtROS and blunts cytarabine in MLL-AF9
AMD3100 reverses stromal protection and potentiates lestaurtinib in MLL-R ALL xenograft
E-selectin-binding blasts are 12-fold more likely to survive chemotherapy in AML models; never tested in KMT2A-rearranged disease
differential stromal protection of primary infant MLL-rearranged ALL is the load-bearing comparative result