Acute myeloid leukemia has long been considered a disease that shrugs off glucocorticoids. While these steroid hormones form the therapeutic backbone of lymphoid malignancies such as acute lymphoblastic leukemia, lymphoma and multiple myeloma, they have never earned a place in standard treatment guidelines for AML, a heterogeneous cancer driven by the clonal expansion of immature myeloid blasts in the bone marrow. Standard AML care still relies on poorly tolerated chemotherapy built around cytarabine and anthracyclines, and relapse remains a persistent threat even among the roughly seventy percent of patients who achieve remission with induction therapy. Now, a new study published in Pharmacology Research & Perspectives suggests that a familiar signaling molecule, histamine, acting through its H2 receptor, could reshape how leukemic cells respond to glucocorticoids, potentially opening a route to combination therapies that lower drug doses and overcome chemoresistance.
The research, conducted by an Argentine team working with cell and molecular models of AML, focused on the glucocorticoid receptor, a nuclear receptor that, upon binding its ligand, translocates to the nucleus and modulates gene expression both directly, through binding to specific DNA sequences called glucocorticoid response elements, and indirectly, through interactions with other transcription factors. Glucocorticoids regulate nearly twenty percent of genome activity, and their transcriptional output is shaped by a web of cross-talking signaling pathways. The laboratory had previously shown that histamine signaling through the H1 receptor can modulate glucocorticoid receptor activity through a dual mechanism, potentiating the receptor via G-protein beta-gamma subunits while inhibiting it through the G-alpha-q pathway. The new work asked whether the H2 receptor, a related G-protein-coupled receptor, exerts similar control.
To answer this question, the researchers used the H2 receptor agonist amthamine alongside dexamethasone, a synthetic glucocorticoid, in engineered cell systems. When cells co-expressing the glucocorticoid receptor and the H2 receptor were treated with amthamine before dexamethasone, the maximal transcriptional response driven by the steroid increased by roughly fifty percent, measured with a luciferase reporter built from tandem glucocorticoid response elements. Notably, the potency of dexamethasone was essentially unchanged, indicating that amthamine amplified the ceiling of glucocorticoid-driven transcription rather than making the receptor more sensitive to its ligand. The effect was traced to signaling cascades downstream of the receptor rather than any direct interaction between histaminergic ligands and the glucocorticoid receptor itself, since inhibitors of those cascades abolished the potentiation.
Unpacking the mechanism revealed a strikingly composite picture. Activation of the H2 receptor canonically splits the G-alpha-s subunit from the G-protein beta-gamma dimer, raising intracellular cAMP. Paradoxically, this cAMP arm worked against the glucocorticoid receptor: directly stimulating adenylyl cyclase with forskolin reduced dexamethasone-induced receptor activity, and that inhibition was reversed by H89, a protein kinase A inhibitor, identifying PKA as the mediator of cAMP’s negative influence. The beta-gamma arm, by contrast, pushed in the opposite direction. Amthamine increased ERK phosphorylation while dampening PI3K-Akt and mTOR signaling, and blocking G-beta-gamma with the inhibitor gallein eliminated the potentiation. A MEK inhibitor completely abolished the amthamine effect, whereas inhibiting PI3K or mTOR on their own actually boosted glucocorticoid receptor activity, confirming that these pathways normally restrain the receptor. The net result of H2 receptor activation is therefore a contest between inhibitory cAMP signaling and stimulatory beta-gamma signaling, with the stimulatory side prevailing.
Intriguingly, the team found that clinically used H2 receptor inverse agonists, including cimetidine, famotidine and ranitidine, the familiar heartburn drugs, also enhanced dexamethasone-driven reporter activity. These ligands behave as ERK-biased antagonists, decreasing cAMP while increasing ERK phosphorylation, which tilts the same signaling balance toward potentiation. The finding raises the provocative possibility that widely available antihistamines could, in principle, modulate glucocorticoid signaling, although the authors stress that their study was conducted in cell models and that such a repurposing remains speculative.
The critical question was whether the artificial reporter results would hold for real genes in leukemic cells. In U937 cells, a human AML model, dexamethasone induced the expression of three endogenous glucocorticoid receptor target genes, GILZ, MKP1 and ANXA1, and amthamine co-treatment enhanced all three. But when the experiments were repeated in a U937 clone engineered to overexpress the H2 receptor, the picture became gene-specific: amthamine’s enhancement persisted for ANXA1, vanished for GILZ, and flipped to inhibition for MKP1. The researchers attribute this heterogeneity to differences in promoter architecture. GILZ is driven by tandem high-affinity glucocorticoid response elements, MKP1 by a single chromatin-remodeling element dependent on the coactivator p300, and ANXA1 by a tethering mechanism that does not require direct receptor binding to DNA. Each architecture confers different sensitivity to competition for limiting coactivators such as CBP/p300, and the relative stoichiometry of receptors, G-proteins and the glucocorticoid receptor itself determines the transcriptional outcome for each gene.
The functional consequences for leukemic cell behavior proved equally nuanced. Dexamethasone displayed a biphasic effect on U937 proliferation: low concentrations, from 0.1 to 10 nanomolar, actually increased cell growth, while higher concentrations suppressed it. Amthamine pretreatment dampened the pro-proliferative effect of low-dose dexamethasone without altering the antiproliferative action of high doses. Mechanistically, low-dose dexamethasone increased phosphorylation of S6K, a readout of mTOR pathway activity, and amthamine blocked this increase. Pharmacological mimicry supported the model: forskolin, the PI3K inhibitor wortmannin and rapamycin all hindered the proliferative effect of low-dose dexamethasone, and only rapamycin additionally boosted the antiproliferative effect of high doses. Consistent with these changes, low-dose dexamethasone reduced expression of the differentiation marker CD14, while high doses increased it, alongside parallel changes in the proliferation-related genes GADD45-beta and CDKN1A.
The most clinically resonant experiments involved cytarabine resistance. The team generated a U937-derived clone, U937-640R, that tolerates cytarabine concentrations more than two hundred times higher than the roughly 1.5 nanomolar IC50 that kills parental cells. In these resistant cells, dexamethasone alone re-sensitized the population to cytarabine, pulling the IC50 down from an effectively unmeasurable level to 3.7 nanomolar at a 10 nanomolar dexamethasone dose and to 20 nanomolar at 1 micromolar. Amthamine then produced a paradoxical, dose-dependent modulation: combined with low-dose dexamethasone, it shifted the cytarabine IC50 even lower, to 1.1 nanomolar, but with high-dose dexamethasone it pushed the IC50 back up to 170 nanomolar. In other words, the H2 agonist amplified chemosensitization at steroid doses low enough to minimize side effects but undermined it at high doses. In the sensitive parental cells, by contrast, neither drug alone nor in combination significantly shifted the cytarabine response curve, underscoring that the combination strategy is specifically relevant to the resistant state.
The authors propose a working model centered on REDD1, a canonical glucocorticoid receptor target gene that represses mTOR. In their framework, low glucocorticoid receptor occupancy fails to induce enough REDD1 to counter a constitutive mTOR-activating pathway, so cells proliferate; at higher occupancy, REDD1 induction overrides that pathway and proliferation halts. H2 receptor signaling may intervene at two points, both by lowering mTOR activity independently of the glucocorticoid receptor and by potentiating receptor activity enough to lower the occupancy threshold for REDD1 induction, thereby converting AML’s biphasic glucocorticoid response into a monotonically antiproliferative one. The model also connects to a broader re-evaluation of glucocorticoid resistance in AML: dexamethasone added to intensive chemotherapy has been associated with reduced relapse and improved survival in hyperleukocytic AML, an effect enriched in NPM1-mutated disease, and the recent DEXAML-02 Phase II trial has provided a first prospective clinical signal in older patients. Histamine itself already holds an approved niche in the disease, since histamine dihydrochloride combined with interleukin-2 has been used as maintenance therapy to prevent AML relapse by protecting antitumor lymphocytes and natural killer cells from oxidative damage.
The study’s practical implication is that pairing an H2 receptor agonist with low-dose dexamethasone could allow lower glucocorticoid and chemotherapy exposures while maintaining or enhancing antileukemic efficacy, a strategy that would matter greatly given the substantial adverse effects of chronic steroid use. The authors are careful to note the limitations: all results derive from a single cell line, and validation across additional models and primary AML samples is essential before any clinical translation. Even so, the demonstration that a histamine receptor can rewire glucocorticoid receptor transcription in a gene- and context-dependent manner, and that this rewiring can resensitize chemoresistant leukemic cells at low steroid doses, adds a compelling new dimension to the pharmacology of an old drug class and offers a fresh lead in the search for less toxic AML combinations.
Subject of Research: Cross-talk between the histamine H2 receptor and the glucocorticoid receptor in acute myeloid leukemia treatment
Article Title: Cross‐Talk Between Histamine H2 Receptor and Glucocorticoid Receptor: Potential Implications in Acute Myeloid Leukemia Treatment
Article References: Torralba‐Agu, V., Fernández, N., Shayo, C., Davio, C., Zappia, C. D., & Monczor, F. (2026). Cross‐Talk Between Histamine H 2 Receptor and Glucocorticoid Receptor: Potential Implications in Acute Myeloid Leukemia Treatment. Pharmacology Research & Perspectives, 14(5), Article e70314. https://doi.org/10.1002/prp2.70314
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DOI: 10.1002/prp2.70314
Keywords: acute myeloid leukemia, glucocorticoid receptor, histamine H2 receptor, dexamethasone, cytarabine resistance, amthamine, mTOR signaling, G-protein-coupled receptor, REDD1, chemosensitization, U937 cells, leukemia therapy
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Nathaniel Bowman. (September 21, 2026). Histamine Receptor Signaling Could Resensitize Resistant Leukemia Cells to Glucocorticoids. Scienmag. https://scienmag.com/histamine-receptor-signaling-could-resensitize-resistant-leukemia-cells-to-glucocorticoids/
Nathaniel Bowman. “Histamine Receptor Signaling Could Resensitize Resistant Leukemia Cells to Glucocorticoids.” Scienmag, 21 September 2026, https://scienmag.com/histamine-receptor-signaling-could-resensitize-resistant-leukemia-cells-to-glucocorticoids/. Accessed 21 September 2026.
Nathaniel Bowman. “Histamine Receptor Signaling Could Resensitize Resistant Leukemia Cells to Glucocorticoids.” Scienmag. September 21, 2026. https://scienmag.com/histamine-receptor-signaling-could-resensitize-resistant-leukemia-cells-to-glucocorticoids/
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Tags: acute myeloid leukemiaamthaminechemosensitizationcytarabine resistancedexamethasoneG protein-coupled receptorglucocorticoid receptorhistamine H2 receptorleukemia therapymTOR signalingREDD1U937 cells
