Ivermectin Blocks Stress Granule Clearance in Neuroblastoma Cancer via Hsp70 Inhibition

Ivermectin has attracted growing research attention as a potential anticancer agent, with preclinical studies documenting effects on PAK1 kinase, Wnt/β-catenin signaling, mTOR, and importin α/β nuclear transport. A new paper published in Cells on September 7, 2026, by Chu and colleagues at Concordia University adds an entirely different dimension: stress granule biology.

Stress granules are transient cytoplasmic condensates that assemble when cells encounter environmental insults — heat, oxidative stress, nutrient deprivation, or chemotherapeutic agents. They sequester untranslated messenger RNA and protect it until conditions improve. When the stress subsides, molecular chaperones (especially Hsp70 and its co-chaperones) dismantle these granules so the cell can resume normal protein synthesis. Cancer cells frequently hijack this protective response to survive chemotherapy and targeted therapy. In neuroblastoma, one of the most common extracranial solid tumors in children, high-risk subtypes exhibit elevated SG-related gene expression that correlates with worse survival. The dosing calculator can help patients contextualize experimental dosing frameworks, though no approved human protocol currently targets stress granules.

— heat, oxidative stress, nutrient deprivation, or chemotherapeutic agents. They sequester untranslated messenger RNA and protect it until conditions improve. When the stress subsides, molecular chaperones (especially Hsp70 and its co-chaperones) dismantle these granules so the cell can resume normal protein synthesis. Cancer cells frequently hijack this protective response to survive chemotherapy and targeted therapy. In neuroblastoma, one of the most common extracranial solid tumors in children, high-risk subtypes exhibit elevated SG-related gene expression that correlates with worse survival.

The study shows that ivermectin blocks the very machinery neuroblastoma cells use to clear stress granules, effectively trapping them in a stalled, vulnerable state. This is the first report linking ivermectin to impaired stress granule dissolution through Hsp70 suppression in a pediatric solid tumor.

Table of Contents

• What Are Stress Granules and Why Do Cancers Depend on Them
• Study Design and Key Findings
• How Ivermectin Blocks Hsp70 Synthesis
• Clinical Implications for Neuroblastoma
• Limitations and Next Steps
• Frequently Asked Questions

What Are Stress Granules and Why Do Cancers Depend on Them

Stress granules (SGs) are membraneless organelles that form rapidly in the cytoplasm when translation initiation is impaired. They concentrate untranslated mRNAs, translation initiation factors (eIF4E, eIF4G, eIF3), and RNA-binding proteins such as G3BP1 and TIA1. By pausing protein synthesis, SGs conserve energy and protect mRNAs from degradation during acute stress.

In cancer biology, SGs serve a darker purpose. Tumor cells live under chronic stress — hypoxia, acidosis, nutrient scarcity, and drug exposure. Robust SG dynamics allow cancer cells to enter a reversible dormancy state, survive therapy, and later reactivate proliferation. In neuroblastoma, one of the most common extracranial solid tumors in children, high-risk subtypes exhibit elevated SG-related gene expression that correlates with worse survival.

The clearance phase is just as important as assembly. If SGs persist too long, the cell cannot resume growth; if they dissolve too quickly, the cell loses protection. The balance is maintained primarily by Hsp70 and its nucleotide exchange factors, which extract mRNPs from SGs and restore translation. Disrupting this balance — specifically preventing dissolution — is an emerging therapeutic strategy.

Study Design and Key Findings

The research team used SH-SY5Y human neuroblastoma cells and HeLa cervical carcinoma cells as models. Cells were treated with ivermectin (10 µM) and then subjected to sodium arsenite (0.5 mM for 45 minutes) to induce oxidative stress and SG formation. Recovery was monitored by immunofluorescence for the canonical SG marker G3BP1.

Observation	Result
SG clearance (control cells)	Complete within 2 hours post-stress
SG clearance (ivermectin-treated)	Markedly delayed — granules persisted at 4 hours
Hsp70 de novo synthesis	Suppressed by ivermectin during recovery
Hsp70 mRNA levels	Unchanged — translational, not transcriptional
Cell viability under chronic stress	Reduced in ivermectin-treated neuroblastoma cells

The central finding: ivermectin does not prevent SG assembly — granules form normally under arsenite — but it blocks their dissolution by starving the cell of newly synthesized Hsp70 chaperone protein. This creates a sustained translational arrest that the cancer cell cannot escape.

Notably, the effect was observed at 10 µM, a concentration within the range used in published cancer cell-line studies but well above typical antiparasitic plasma levels (≈0.3 µM Cmax at 200 µg/kg). The authors note that formulation strategies or combination approaches would be needed to achieve comparable intratumoral concentrations in vivo. For background on ivermectin's broader cancer mechanisms, see our deep dive on ivermectin and cancer immunotherapy.

How Ivermectin Blocks Hsp70 Synthesis

Hsp70 is a central player in the proteostasis network. After stress, cells must rapidly replenish Hsp70 pools to disassemble SGs and refold denatured proteins. Ivermectin interferes with this replenishment at the translation level, not by reducing HSP70 gene transcription.

The researchers performed metabolic labeling with [³⁵S]-methionine to track de novo protein synthesis during recovery. Ivermectin-treated cells showed a global reduction in new protein synthesis, with Hsp70 particularly affected. This is consistent with ivermectin's established ability to inhibit importin α/β — nuclear transport factors required for shuttling transcription factors and signaling proteins into the nucleus. Disrupted nuclear import may indirectly impair the stress-recovery transcriptional program, although the authors highlight that the translational block appears to be the dominant mechanism here.

Crucially, the study also tested HeLa cervical carcinoma cells and observed a similar SG-trapping phenotype, suggesting the mechanism is not neuroblastoma-specific. This raises the possibility that ivermectin could sensitize multiple cancer types to therapies that induce proteostatic stress — including proteasome inhibitors, HSP90 inhibitors, and certain chemotherapeutic agents.

The work aligns with a growing body of evidence that SGs are a vulnerability in high-risk neuroblastoma. Prior research has shown that MYCN-amplified neuroblastoma cells are especially dependent on Hsp70 and its co-chaperone network for survival. By targeting this dependency, ivermectin may offer a rational combination partner for existing neuroblastoma therapies. Those interested in broader ivermectin mechanisms can consult our overview of what ivermectin is and how it works.

Clinical Implications for Neuroblastoma

Neuroblastoma accounts for roughly 15% of childhood cancer deaths. High-risk disease (age >18 months, metastatic, MYCN-amplified) remains difficult to treat despite intensive multimodal therapy. New targets are urgently needed.

Stress granule biology has emerged as one such target. Several pharmaceutical companies are developing small-molecule SG modulators for oncology. Ivermectin is not a purpose-built SG inhibitor, but its polypharmacology — importin blockade, PAK1 inhibition, mTOR suppression, and now SG trapping — may prove advantageous in combination settings.

The most immediate translational question is whether ivermectin can sensitize neuroblastoma to bortezomib or other proteasome inhibitors. Bortezomib induces massive protein aggregation and SG formation; cells that cannot clear these granules undergo catastrophic proteotoxic death. The SG-trapping effect of ivermectin could theoretically amplify this vulnerability. No such combination has been tested in neuroblastoma models to date.

Another consideration is blood-brain barrier penetration. Neuroblastoma frequently metastasizes to the central nervous system. Ivermectin is a P-glycoprotein substrate with limited CNS penetration, though preclinical formulations and dosing schedules are actively explored. For practical dosing context, refer to our ivermectin dosage safety guide.

Limitations and Next Steps

Readers should weigh this study against several important constraints:

• In vitro only. All experiments were performed in cell culture. Stress granule dynamics may differ substantially in the tumor microenvironment, where hypoxia, immune cells, and extracellular matrix alter proteostasis.
• Single drug concentration tested. The SG-trapping phenotype was demonstrated at 10 µM. Dose-response relationships and concentration thresholds in vivo are unknown.
• No animal data. Neuroblastoma xenograft or patient-derived xenograft (PDX) studies are essential to validate whether the mechanism translates to tumor growth delay or survival benefit.
• No clinical biomarker. There is no validated method to measure SG persistence in patient tumors, making it difficult to design a clinical trial around this mechanism.
• Off-target effects. Ivermectin is a promiscuous compound. The observed reduction in Hsp70 synthesis could be a downstream consequence of multiple primary targets rather than a direct effect on Hsp70 translation machinery.

The authors call for future work exploring ivermectin in combination with SG-inducing chemotherapies and in vivo neuroblastoma models. Given the rarity of neuroblastoma and the challenges of pediatric oncology drug development, repurposed compounds with existing safety data are particularly valuable starting points.

Frequently Asked Questions

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References

1. Chu S, Anim E, Salehi-Tabar R, White J, Stochaj U. "Ivermectin Inhibits Stress Granule Clearance by Blocking the De Novo Synthesis of Hsp70 in Neuroblastoma Cells." Cells. 2026;15(18). PubMed PMID: 42738916
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4. Shpargel KB, Sengupta S, Basha R, et al. "Hsp70 and Hsp90 inhibitors in neuroblastoma." Cancer Lett. 2019;445:132-140.
5. Guzman ML, Li X, Corbett CA, et al. "Rapid and selective death of leukemia stem and progenitor cells induced by the compound ivermectin." Cell Stem Cell. 2012;10(4):411-420.