The original study, published on 4 February 2019, reported that circNRIP1 promoted the growth and spread of gastric cancer cells by binding and sequestering microRNA-149-5p, thereby relieving repression of AKT1 and activating the mTOR pathway, a central growth-control circuit in many cancers. The circular RNA sponge hypothesis was one of the most fashionable ideas in cancer biology at the time: circular RNAs, which lack the free ends of linear messenger RNAs and are therefore unusually stable, were proposed to soak up microRNAs and prevent them from silencing their protein-coding targets. Hundreds of papers in the late 2010s described competing endogenous RNA networks of this kind, and circNRIP1 became one of the frequently cited examples in the gastric cancer literature.

The retraction notice lays out the specific concerns with unusual precision. Figure 5B of the paper, which was supposed to show microscopy or assay images related to microRNA-149-5p, appears highly similar to Figure 6B, which was supposed to show the effects of silencing circNRIP1 with small interfering RNA. In a well-constructed experiment, those two conditions should produce distinct images, since they represent different experimental manipulations. When images from nominally different conditions are highly similar or identical, it raises the possibility that the same raw data were reused to support different conclusions, whether through careless figure assembly or something more troubling.

The problems extended beyond the paper itself. The notice states that a panel in Figure 5E of the retracted article, labeled as circNRIP1 overexpression at day one, appears highly similar to a panel in a separate 2018 publication by largely overlapping authors in the Journal of Experimental and Clinical Cancer Research, specifically a panel showing a microRNA-133a-3p mimic at day ten. Another Figure 5E panel, labeled circNRIP1 knockdown at day ten, appears highly similar to a control knockdown panel at day ten in yet another publication. Within the retracted paper itself, the PFK and P62 western blots in Figure 6A also appear highly similar to each other, a red flag because those proteins were supposed to reflect different biological readouts, in that case glycolytic enzyme expression and autophagy flux respectively.

The overlapping publications implicated by the notice have themselves faced consequences. The 2018 paper on microRNA-133a-3p, which reported that this microRNA represses gastric cancer growth and metastasis by blocking autophagy-mediated glutaminolysis, received its own retraction in July 2024. A third related paper, published in Cell Death and Disease in 2021, described circular RNA UBE2Q2 promoting malignant progression of gastric cancer through STAT3-mediated autophagy and glycolysis. The recurrence of the same themes, autophagy, glycolysis, and circular RNAs, across the group’s output is precisely what made cross-paper image comparisons possible, and the notice indicates that the sheer number of concerns overwhelmed the authors’ explanations.

A second, independent line of concern involved the cell lines used in the study. The authors employed SGC-7901, BGC-823, and MGC-803, three gastric cancer cell lines that have been reported in the scientific literature to be contaminated with HeLa cells, the notorious cervical cancer line that has silently infiltrated laboratories worldwide since the 1950s. The notice specifies that these contaminated lines were used in Figures 1E, 2B through 2D, and 3B through 3E. Cell line misidentification is one of the most pervasive quality problems in cancer research, because experiments attributed to gastric cancer may in fact have been performed on HeLa-derived cells, invalidating the tissue-specific conclusions the authors drew about gastric tumor biology.

The authors did respond to the initial concerns, according to the notice. They explained that the image duplications arose from similar experimental design and errors in figure preparation across the three articles, and they asserted that the images presented in Figure 5E were correct for this particular study. That explanation, however, did not satisfy the journal. Given the high number of concerns, spanning duplicated images within the paper, duplication across multiple external publications, and the use of contaminated cell lines, the Editor-in-Chief concluded that confidence in the presented data could not be maintained. Notably, the authors have not responded to any correspondence from the publisher about the retraction notice itself.

The retraction carries technical lessons for anyone following the circular RNA literature. The competing endogenous RNA framework depends on a chain of evidence: that the circular RNA is genuinely expressed and stable, that it physically binds the claimed microRNA, that the microRNA target is derepressed, and that the downstream kinase pathway, here AKT1 and mTOR, changes accordingly. Western blots for proteins like PFK, a rate-limiting glycolytic enzyme, and P62, an autophagy receptor whose accumulation signals impaired autophagic degradation, were meant to anchor the metabolic arm of that story. When the underlying images cannot be trusted, every downstream inference, from sponge activity to pathway activation, loses its empirical foundation, which is why journals treat figure-level integrity as inseparable from the scientific claim itself.

For the broader field, the case illustrates how the explosion of circular RNA papers in the late 2010s created conditions in which errors and duplications could propagate. Similar experimental designs across a laboratory’s projects make accidental figure mix-ups more likely, but they also make deliberate reuse harder to detect at peer review, since reviewers rarely have access to a group’s unpublished datasets. Databases now flag cross-references between retracted papers, and tools that detect duplicated image regions have become standard parts of post-publication scrutiny. The fact that this retraction was finalized years after the original publication, and after a companion paper had already been retracted, shows that the process works, albeit slowly.

Readers who cited the circNRIP1 paper, or who built experiments on the claim that microRNA-149-5p derepresses AKT1/mTOR signaling in gastric cancer, should now treat those findings as unsupported. The retraction notice, published in volume 25 of Molecular Cancer as article number 228, is freely accessible, and the original article remains online but is watermarked as retracted. The episode is a reminder that striking molecular mechanisms, especially those involving elegant regulatory circuits like circular RNA sponges, deserve scrutiny not just for their biological plausibility but for the provenance of every image and every cell line that supports them.

Subject of Research: Retraction of a gastric cancer circular RNA study due to image duplication and cell line contamination concerns

Article Title: Retraction Note: Circular RNA circNRIP1 acts as a microRNA-149-5p sponge to promote gastric cancer progression via the AKT1/mTOR pathway

Article References: Zhang, X., Wang, S., Wang, H., Cao, J., Huang, X., Chen, Z., Xu, P., Sun, G., Xu, J., Lv, J., & Xu, Z. (2026). Retraction Note: Circular RNA circNRIP1 acts as a microRNA-149-5p sponge to promote gastric cancer progression via the AKT1/mTOR pathway. Molecular Cancer, 25(1), Article 228. https://doi.org/10.1186/s12943-026-02804-5

Image Credits: AI Generated

DOI: 10.1186/s12943-026-02804-5

Keywords: circNRIP1, gastric cancer, retraction, microRNA-149-5p, AKT1/mTOR pathway, circular RNA, cell line contamination, HeLa, image duplication, Molecular Cancer, research integrity, autophagy