Summary: The anti-diarrheal drug loperamide induces autophagy and promotes autophagy-dependent cell death in glioblastoma cells.
Source: Goethe University
A research team led by Dr Sjoerd van Wijk at the Institute of Experimental Cancer Research in Paediatrics, Goethe University, previously reported that loperamide, a common anti-diarrheal medication, can trigger death in glioblastoma cell lines. In their latest work they have clarified how loperamide acts on these tumour cells and identified molecular players that connect cellular stress to selective degradation of the endoplasmic reticulum, offering potential new directions for therapeutic development.
When cells digest themselves
In some tumour cells, loperamide causes a stress response in the endoplasmic reticulum (ER), the cellular compartment responsible for protein folding and processing. This ER stress initiates a targeted degradation process of ER membranes—reticulophagy—which can progress into self-digestion of the cell through hyperactivated autophagy. While autophagy normally serves as a protective, homeostatic mechanism that recycles damaged or surplus cellular components and supports survival under nutrient shortage, excessive or dysregulated autophagy can destroy essential cellular structures and lead to cell death.
“Our cell line experiments indicate that activating autophagy in this way could be a strategy to treat glioblastoma,” says van Wijk. Glioblastoma is an aggressive and often lethal brain tumour in both children and adults that typically responds poorly to existing chemotherapy, so new therapeutic approaches are urgently needed.
The team identified the transcription factor ATF4 as a key link between ER stress and reticulophagy. ATF4 production increases during ER stress and in response to loperamide exposure, and this increase promotes dismantling of ER membranes and the ER itself, driving the reticulophagy process.
Anti-diarrheal drug triggers cell death in glioblastoma cells
When the researchers inhibited ATF4, far fewer tumour cells underwent cell death after loperamide treatment, demonstrating that ATF4 is necessary for the full cytotoxic effect. Electron microscopy of loperamide-treated glioblastoma cells revealed ER fragments and degradation products, confirming that reticulophagy contributes visibly to the demise of these cancer cells. In contrast, loperamide induced autophagy without causing cell death in other cell types tested, such as embryonic mouse fibroblasts.
Van Wijk notes that, in its conventional use as an anti-diarrheal, loperamide primarily acts on the gut and is poorly absorbed into the bloodstream, which makes it safe at standard doses for that indication. Translating the anti-cancer potential of loperamide into a clinical setting, particularly for brain tumours, will require overcoming delivery challenges such as crossing the blood-brain barrier.
Mechanism of action may apply to other diseases
Beyond glioblastoma, these findings may have broader relevance for diseases in which ER turnover and reticulophagy are disrupted, including certain neurodegenerative disorders and other cancer types. The research highlights ATF4 and reticulophagy receptors as central mediators of drug-induced ER degradation, suggesting new molecular targets for therapeutic exploration.
Further research is needed before loperamide or related compounds could be applied clinically to treat glioblastoma or other conditions. Key next steps include determining safe and effective ways to deliver loperamide into the brain—nanoparticle-based transport is one potential approach—and screening for other compounds that trigger reticulophagy. The Frankfurt research group plans to identify additional reticulophagy-inducing agents and to investigate strategies that amplify or refine loperamide’s effect to improve therapeutic potential.
Funding: The work from Sjoerd van Wijk’s laboratory was supported by the Frankfurt Foundation for Children with Cancer (Frankfurter Stiftung für krebskranke Kinder) and by the Collaborative Research Centre 1177 “Molecular and Functional Characterisation of Selective Autophagy,” funded by the German Research Foundation (Deutsche Forschungsgemeinschaft). The study reflects collaboration with Dr Muriel Mari and Professor Fulvio Reggiori (University of Groningen, The Netherlands) and Professor Donat Kögel (Experimental Neurosurgery, Goethe University).
About this brain cancer research news
Source: Goethe University
Contact: Markus Bernards – Goethe University
Image: The image is in the public domain
Original Research: Closed access. “ATF4 links ER stress with reticulophagy in glioblastoma cells” by Sjoerd van Wijk et al. Published in Autophagy.
Abstract
ATF4 links ER stress with reticulophagy in glioblastoma cells
Reticulophagy, the selective autophagic degradation of endoplasmic reticulum fragments, is triggered by conditions such as amino acid deprivation and ER stress and serves to restore cellular energy balance and ER homeostasis. In this study, the authors examined how the autophagy-inducing compound loperamide (LOP) promotes autophagic cell death (ACD) in glioblastoma cells. Loperamide stimulates the expression of the transcription factor ATF4 alongside other markers of ER stress. Deletion of ATF4 markedly reduced loperamide-induced autophagy and ACD. Functionally, loperamide caused large ER fragments to be sequestered within autophagosomes and lysosomes, as shown by electron and fluorescence microscopy. Loperamide-induced reticulophagy and cell death were primarily mediated by the reticulophagy receptor RETREG1/FAM134B and, to a lesser extent, by TEX264, indicating that reticulophagy receptors can drive ACD. Importantly, ATF4 was required not only for loperamide-driven autophagy and cell death but also for the induction of reticulophagy itself. These findings establish a mechanistic connection among ER stress, ATF4 activation, reticulophagy receptors, and autophagy-dependent cell death, with implications for other contexts of drug-induced ER stress.