Scientists have designed a small, cell-penetrating peptide that shuts down a key autophagy enzyme in cancer cells, raising their levels of reactive oxygen species and triggering cell death, according to a study published in Cellular Oncology. In a xenograft mouse model, administration of the peptide led to a significant reduction in tumor size.
Autophagy is a cellular recycling process in which the protease ATG4 cleaves ATG8 family proteins, a step needed to activate the pathway. Because autophagy has been linked to cancer progression, the research team set out to design alpha-helical peptides targeting ATG4 and to evaluate their potential as autophagy inhibitors for cancer therapy.
The researchers synthesized three alpha-helical peptides, designated H1 through H3, derived from GBRL2, a human ATG8 homolog. Using reporter assays and molecular dynamics simulations, they assessed the peptides’ effects on ATG4B activity and binding stability. Autophagy modulation was analyzed by immunoblotting and confocal microscopy, while anticancer effects were evaluated with flow cytometry, fluorescence imaging, tumorsphere models, and xenograft studies.
Among the three candidates, the second helical peptide, GBRL2H2, significantly inhibited ATG4B and ATG4A enzymatic activity in vitro. According to the study’s highlights, the ATG4B Targeting Peptide, abbreviated ATP, suppresses ATG4B proteolytic activity with an IC50 of 0.7 micromolar.
To get the peptide into cells, the team fused it with Tat, a well-known cell-penetrating peptide. The resulting Tat-ATP construct entered cells and reduced intracellular ATG4 activity and autophagic flux, whereas the Tat peptide or ATP alone produced only minimal to modest effects. Tat-ATP treatment also decreased cancer cell viability and colony formation.
The cell-killing effects were traced to mitochondrial and caspase-related mechanisms. Tat-ATP significantly increased the population of dead cancer cells, and this occurred alongside decreased mitophagy, reduced mitochondrial membrane potential, elevated reactive oxygen species, and increased caspase-3/7 activity. Importantly, the observed cell death was substantially reversed when cells were treated with ROS scavengers and caspase inhibitors, indicating that ROS and caspase-mediated pathways are involved in the peptide’s lethal effect.
Beyond killing cells in culture, Tat-ATP impaired cancer cell motility and reduced the viability of both cancer cell line-derived and patient-derived tumorspheres, three-dimensional cell models that often better reflect tumor biology than flat cell layers.
The therapeutic promise extended to living animals. In a xenograft mouse model, administration of Tat-ATP led to a significant reduction in tumor size, and the study’s highlights note that the peptide triggers cancer cell death in patient-derived tumorspheres and xenografted tumors.
The authors conclude that Tat-ATP is a novel ATG4 inhibitor, highlighting its potential as an anticancer agent. The findings position the peptide as a candidate ATG4B inhibitor for targeted cancer therapy, though the work described here represents preclinical laboratory and animal-model evidence rather than clinical results in patients.
The article was published as an open-access paper in Cellular Oncology on 19 September 2026 and is being shared early to provide faster access to peer-reviewed, accepted research; the publisher notes that this version is subject to further edits and will be replaced by the final Version of Record.
Subject of Research: Design of an ATG4-targeting peptide that inhibits autophagy and induces cancer cell death
Article Title: ATG4 targeting peptide inhibits autophagy and elevates reactive oxygen species to trigger cancer cell death
Article References: Liu, P.-F., Tsai, W.-L., Hu, W.-H., Morgan, P., Chang, H.-W., Pan, H.-W., Hsieh, A.-T., Li, P.-C., Yang, S.-Y., Jhou, P.-Y., & Shu, C.-W. (2026). ATG4 targeting peptide inhibits autophagy and elevates reactive oxygen species to trigger cancer cell death. Cellular Oncology. https://doi.org/10.1007/s13402-026-01302-6
Image Credits: AI Generated
DOI: 10.1007/s13402-026-01302-6
Keywords: ATG4, autophagy, ATG4B inhibitor, reactive oxygen species, cancer therapy, peptide inhibitor, Tat-ATP, tumorspheres, xenograft model, mitophagy, caspase, Cellular Oncology
News Source: Nathaniel Bowman. (October 30, 2026). New ATG4-targeting peptide blocks autophagy and kills cancer cells in mice. Scienmag.
