The research team, led by investigators at Shandong University and collaborating institutions across China, set out to answer a question that has puzzled oncologists for years: how do colorectal cancer cells that survive chemotherapy manage to keep their mitochondria, the cellular power plants, in working order? Drug-tolerant persister cells are known to enter a reversible adaptive state, rather than acquiring permanent genetic resistance mutations, which makes them especially insidious. When therapy stops, these cells can resume proliferation and regenerate the tumor with its original drug sensitivity intact. The researchers built a comprehensive experimental system to catch these cells in the act, using patient-derived xenografts, organoids grown from patient tumors, conventional colorectal cancer cell lines, and cell line-derived xenografts in animal models.

What they observed in the surviving cells was a profound metabolic transformation. The persister cells showed markedly reduced proliferation without a corresponding increase in apoptosis, the programmed cell death that chemotherapy is designed to trigger. When the researchers withdrew the drugs, the cells resumed growth, confirming that the tolerant state was genuinely reversible. At the metabolic level, the persister cells suppressed glycolysis, the sugar-burning pathway that most cancer cells rely on heavily, and produced far less lactate, the acidic byproduct of that pathway. Instead, they became increasingly dependent on oxidative phosphorylation, the more efficient mitochondrial process that generates cellular energy using oxygen. This metabolic shift was accompanied by a striking activation of mitophagy, the cellular quality-control system that selectively recycles damaged mitochondria.

The centerpiece of the discovery is a protein called UQCRC2, or ubiquinol-cytochrome c reductase core protein 2, a structural component of complex III in the mitochondrial electron transport chain. The researchers found that UQCRC2 accumulated in the drug-tolerant persister cells, where it supported Parkin and SQSTM1-associated mitophagy and enabled the residual cells to survive. But the truly novel element lies in how UQCRC2 is regulated. The team employed an emerging field of post-translational modification research known as lactylomics, using global mass-spectrometry-based profiling to map lysine lactylation sites, a chemical tagging process in which lactate-derived lactyl groups attach to lysine residues on proteins. Because the persister cells produced less lactate, the overall level of lysine lactylation across the proteome dropped, and specifically, lactylation of UQCRC2 at the amino acid lysine 430 declined sharply.

Here the story takes a turn worthy of a molecular thriller. When UQCRC2 is heavily lactylated at position 430, the modified protein becomes a target for K48-linked ubiquitination, a molecular tag that condemns proteins to destruction by the proteasome, the cell’s waste-disposal machinery. Reduced lactylation therefore protects UQCRC2 from degradation and allows it to accumulate. The researchers identified the enzyme responsible for removing the lactyl tag: SIRT1, a member of the sirtuin family of NAD-dependent deacylases that has long been associated with longevity, stress resistance, and metabolic regulation. Through a cell-free delactylation assay, the team demonstrated that SIRT1 directly removes the lactylation from UQCRC2 at lysine 430 in a manner dependent on NAD, the cellular energy carrier. This delactylation stabilizes UQCRC2, preserving mitochondrial function and fueling the mitophagy program that keeps the persister cells alive.

The functional consequences of this pathway were confirmed through a series of genetic and pharmacological experiments. When the researchers depleted PINK1, the kinase that initiates the mitophagy cascade, or knocked down UQCRC2 itself, the survival of the residual drug-tolerant cells plummeted and tumor regrowth was significantly delayed. Inhibiting SIRT1, either genetically or with drugs, produced the same effect, effectively collapsing the survival mechanism that the persister cells depend upon. These results suggest that the SIRT1-UQCRC2 axis represents a genuine therapeutic vulnerability, a chink in the armor of chemotherapy-tolerant cells that could be exploited to prevent the outgrowth of tumors after treatment.

Perhaps the most clinically significant finding came from analyses of actual patient samples. Among chemotherapy-responsive patients with advanced colorectal cancer, low expression of the UQCRC2-K430 lactylation mark in tumor tissue remained associated with poorer overall survival even after multivariable statistical adjustment. The researchers also examined paired samples of circulating tumor cells, rare cancer cells that travel through the bloodstream, collected from patients before and after chemotherapy exposure. In these paired samples, increased SIRT1 expression or decreased UQCRC2-K430 lactylation after chemotherapy was associated with shorter progression-free survival. This pattern suggests that the molecular signature of the persister state, detectable in a simple blood-based assay, could serve as an early warning system identifying patients whose residual disease is primed for relapse.

The methodological breadth of the study deserves particular attention. By integrating whole-exome sequencing with transcriptomic, proteomic, metabolomic, and lactylomic analyses, the researchers were able to triangulate the mechanism from multiple independent angles, ruling out genetic mutation as the driver and instead pointing to a reversible epiproteomic program. Whole-exome sequencing confirmed that the persister cells had not acquired new resistance mutations, while the multi-omic profiling revealed the coordinated metabolic and post-translational remodeling that defines the tolerant state. Metabolic assays measuring oxygen consumption and extracellular acidification rates quantified the shift from glycolysis to oxidative phosphorylation, while protein stability and ubiquitination analyses traced the fate of UQCRC2 through the degradation pathway.

The broader implications of this work extend well beyond colorectal cancer. Drug-tolerant persister cells have been implicated in treatment failure across many tumor types, and the discovery that lysine lactylation functions as a metabolic sensor linking glycolytic output to mitochondrial quality control provides a unifying framework for understanding how cancer cells weather therapeutic stress. Lactate, long dismissed as a mere metabolic waste product, is increasingly recognized as a signaling molecule, and this study adds a striking new dimension to that picture: lactate levels directly tune the stability of a core respiratory protein, thereby determining whether a cell can maintain the mitochondrial infrastructure needed to survive chemotherapy. The finding also positions sirtuins, and SIRT1 in particular, as enzymatic gatekeepers of this lactylation-dependent survival program, raising the prospect that existing and experimental SIRT1 inhibitors could be repurposed as anti-persister agents.

For patients, the road from laboratory discovery to clinical application is long, but this study offers concrete waypoints. The identification of UQCRC2-K430 lactylation as a candidate biomarker of chemotherapy-associated residual disease opens the door to trials that could monitor this mark in circulating tumor cells during treatment, potentially allowing oncologists to intervene before overt relapse occurs. Therapeutic strategies that combine standard FOLFOXIRI chemotherapy with agents that disrupt the SIRT1-UQCRC2-mitophagy axis could, in principle, eliminate the reservoir of persister cells that currently seed tumor regrowth. As the authors conclude, this low-lactate, SIRT1-regulated mechanism couples metabolic suppression to mitochondrial quality control and enables reversible chemotherapy tolerance, and it now stands as one of the most mechanistically complete portraits of drug tolerance assembled in any cancer type to date. The study was supported by the National Natural Science Foundation of China and multiple Chinese research foundations, and the full open-access article is available in Molecular Cancer.

Subject of Research: Lactylation-mediated mitophagy in colorectal cancer drug tolerance during chemotherapy

Article Title: UQCRC2 lactylation-mediated mitophagy orchestrates colorectal cancer cell metabolism to establish a drug-tolerant state during chemotherapy

Article References: UQCRC2 lactylation-mediated mitophagy orchestrates colorectal cancer cell metabolism to establish a drug-tolerant state during chemotherapy. (n.d.). https://doi.org/10.1186/s12943-026-02793-5

Image Credits: AI Generated

DOI: 10.1186/s12943-026-02793-5

Keywords: colorectal cancer, drug-tolerant persister cells, FOLFOXIRI chemotherapy, UQCRC2, lysine lactylation, SIRT1, mitophagy, oxidative phosphorylation, metabolic reprogramming, circulating tumor cells, chemotherapy tolerance, Molecular Cancer

The findings, published in Genome Medicine, challenge the conventional picture of a tumour as a mass of rapidly multiplying cells. Within the same tumour, researchers identified regions dominated by proliferating cancer cells alongside distinct pockets populated by quiescent cells. These dormant cells have temporarily paused their cell cycle, a biological state that makes them far less vulnerable to many chemotherapy drugs, which are designed to damage cells as they divide. Although they may be inactive, the cells can later re-enter the cell cycle and contribute to tumour growth, recurrence or metastatic spread.

“Quiescent cancer cells are very dangerous,” said Dr Alexis Barr, co-lead author and head of the Cell Cycle Control group at the MRC Laboratory of Medical Sciences. Cancer cells can enter quiescence when they encounter stresses such as limited nutrients, oxygen shortages or inadequate blood supply. Rather than dying, they reduce their activity and wait for conditions to improve. This survival strategy resembles hibernation: the cells conserve resources during hostile conditions and may reactivate after treatment has ended, when the tumour environment becomes more favourable.

To locate and characterise these cells, Barr’s team collaborated with Dr Maria Secrier’s computational biology group at UCL. The researchers integrated single-cell RNA sequencing with spatial transcriptomics, two technologies that provide complementary views of tumour biology. Single-cell RNA sequencing measures the genes active in individual cells, allowing researchers to distinguish proliferating, dormant, immune and connective-tissue populations. Spatial transcriptomics adds the missing geography by recording where those cells are located within the tumour and which other cell types occupy the surrounding tissue.

This combined approach produced a cellular map showing that features associated with treatment resistance can exist before therapy begins. The researchers detected tumour cells resembling therapy-resistant populations in untreated breast cancers, suggesting that resistance is not always created by exposure to drugs. Some resistant characteristics may already be embedded within the tumour’s cellular organisation. The pattern appeared in both aggressive breast cancer subtypes and slower-developing forms, an important observation because dormancy has often been linked primarily with less aggressive disease.

The most striking discovery was the repeated association between dormant cancer cells and two types of neighbouring cells: CXCL10-positive macrophages and myofibroblastic cancer-associated fibroblasts. Macrophages are immune cells that can perform very different functions depending on signals from their surroundings. Cancer-associated fibroblasts are connective-tissue cells reprogrammed by tumours to support tumour architecture, blood-vessel formation and disease progression. In the mapped tumours, these populations gathered around dormant cancer cells, creating what the researchers described as a potential protective shell.

The biological meaning of this arrangement remains unresolved. The surrounding macrophages and fibroblasts may actively encourage cancer cells to enter or remain in quiescence, or dormant cancer cells may recruit and reshape nearby support cells. The relationship could also operate in both directions, with tumour cells and their environment continually influencing one another. The researchers caution that the spatial association does not yet prove that these cells form a physical barrier against chemotherapy or immune cells. Experimental studies will be needed to determine whether the proposed “shield” directly protects dormant cancer cells and which molecular signals maintain the niche.

The tumour maps also revealed increased activity of the complement pathway in dormant regions. Complement is a network of immune proteins that can recognise and mark abnormal cells, regulate inflammation and influence interactions between immune and tumour cells. Its heightened activity in quiescent niches could provide a vulnerability, although the outcome may depend on the precise complement signals present and how cancer cells manipulate them. Treatments aimed at this pathway, or at the macrophages and fibroblasts surrounding dormant cells, could eventually be combined with therapies that attack actively dividing tumour cells.

The study therefore points towards a treatment strategy that targets the tumour as an ecosystem rather than as a single, uniform population. Drugs that eliminate proliferating cancer cells may leave dormant cells untouched, while therapies directed at dormant niches could disrupt the support system that enables them to survive. Combining these approaches might suppress tumour growth in the short term while reducing the reservoir of cells capable of causing relapse years later. However, the researchers emphasise that their predictions are based on computational analysis of publicly available tumour data and must be tested in laboratory models and clinical studies before they can guide treatment.

By placing dormant cancer cells on the map, the work offers a more detailed explanation of why breast cancer can return after apparently successful therapy. The danger may not lie only in a small number of unusually resilient cancer cells, but in the specialised neighbourhoods that help them persist. Understanding how cancer cells, immune cells and fibroblasts co-evolve inside these regions could enable more precise drug combinations—treating active tumour growth while dismantling the biological shelters that allow hidden disease to survive.

Subject of Research: Spatial organisation of proliferating and dormant breast cancer cells, their interactions with immune and stromal cells, and potential treatment-resistant tumour niches.

Article Title: Spatial ecology of breast cancer reveals co-evolution of proliferative and dormant niches

Web References: https://link.springer.com/article/10.1186/s13073-026-01711-0

References: Genome Medicine; DOI: 10.1186/s13073-026-01711-0

Keywords: Breast cancer, dormant cancer cells, quiescence, tumour microenvironment, spatial transcriptomics, single-cell RNA sequencing, macrophages, cancer-associated fibroblasts, complement pathway, treatment resistance, cancer recurrence, tumour niches

The primary focus of the study revolves around the insights gained into the cellular adaptations that lead to therapy resistance. Cancer cells possess an uncanny ability to adjust their biochemical pathways in response to treatment. Koeberle’s team observed that exposure to certain natural cytotoxic agents triggers a stress response within these cells, effectively altering their biological state. This stress response is critical in understanding how cancer cells can survive despite the presence of chemotherapeutic agents that should otherwise lead to their demise.

One of the key mechanisms identified involves the increased incorporation of polyunsaturated fatty acids into the cellular membrane of cancer cells subjected to these natural cytotoxic substances. This process enhances the cell membrane’s susceptibility to ferroptosis, a form of regulated cell death distinct from apoptosis. Ferroptosis is characterized by the accumulation of reactive oxygen species, which damage the polyunsaturated fatty acids in the membrane, leading to pore formation and ultimately cell death. This discovery marks a vital step forward in cancer research, as it identifies a potential vulnerability in cancer cells that could be exploited therapeutically.

The team’s experimental approach utilized a range of cancer cell lines and various cytotoxic agents to explore this phenomenon across different types of cancer. Their research highlights a universal mechanism, suggesting that the observed changes in cell membrane composition and sensitivity to ferroptosis could apply broadly across multiple cancer types. This finding carries significant implications for the development of new treatment regimens that could be effective even when traditional chemotherapy fails.

Moreover, the discovery of this mechanism not only sheds light on existing treatment challenges but also presents an opportunity to enhance therapeutic strategies. By targeting the alterations in membrane composition and promoting ferroptosis in conjunction with conventional treatments, researchers could potentially devise a dual-action approach that raises the likelihood of successful tumor elimination. Koeberle speculates that the addition of ferroptosis-inducing agents to existing treatment plans may help overcome the barriers presented by therapy resistance in cancer cells.

The collaboration among researchers from various global institutions enriches the findings of the study. This interdisciplinary effort brings together expertise from Innsbruck, Hamburg, Jena, Salzburg, Tokyo, and Valbonne, demonstrating the collective commitment of the scientific community to unravel the complexities of cancer treatment resistance. Their collective work underscores the importance of collaborative research in tackling daunting challenges in oncology.

As the study unfolds its findings, it prompts a call to action for further exploration into the therapeutic potential of natural substances in cancer treatment. The ability of these agents to alter cellular membranes and induce ferroptosis opens up a realm of possibilities. Future research could aim to identify specific compounds that can be effectively integrated into treatment protocols alongside existing chemotherapeutics, potentially maximizing treatment efficacy and providing new hope for patients facing resistant tumors.

In light of these revelations, patients and healthcare providers are encouraged to remain informed about ongoing research in the field of oncology. This study serves as a reminder of the dynamic nature of cancer research and the constant progress being made in understanding and combating this complex disease. The findings not only provide insight into the molecular underpinnings of resistance but also stimulate discussions about personalized treatment approaches that could revolutionize patient care.

The publication of this research marks a significant milestone in the ongoing quest for effective cancer treatments. As more discoveries emerge, the scientific community remains optimistic about the potential for innovative therapies that can improve patient outcomes. Advances in our understanding of cancer cell biology, particularly in relation to natural substances and their mechanisms of action, lay the groundwork for the next generation of cancer therapies.

As we witness developments in this area, it is essential to continue supporting research initiatives that seek to explore the untapped potential of nature-derived compounds in medicine. The journey towards overcoming cancer’s challenges requires both scientific inquiry and public support to foster breakthroughs that can transform the lives of those affected by this disease. The hope is that through continued investigation and collaboration, we can shift the paradigms of cancer treatment and enhance the quality of life for countless patients worldwide.

The scientific community eagerly anticipates further studies that will build on these findings, as the need for effective treatments against therapy-resistant tumors remains pressing. By integrating knowledge from various branches of science, including pharmacology, molecular biology, and clinical research, the possibilities for novel treatment strategies will expand. The dedication of researchers and institutions worldwide is crucial in the ongoing fight against cancer, where every advance can lead to meaningful improvements in patient care and outcomes.

In conclusion, the groundbreaking research led by Andreas Koeberle and his team provides valuable insights into the mechanisms of therapy resistance in cancer cells. The identification of polyunsaturated fatty acids’ role in cell membrane changes and increased susceptibility to ferroptosis paves the way for innovative treatment options. The intersection of natural substances and advanced cancer therapies could herald a new era in oncology, one that aligns with the pressing need for more effective and personalized treatment solutions for patients battling cancer.

Subject of Research: Cells
Article Title: Attenuated growth factor signaling during cell death initiation sensitizes membranes towards peroxidation
News Publication Date: 25-Feb-2025
Web References: http://dx.doi.org/10.1038/s41467-025-56711-2
References: Nature Communications
Image Credits: Credit: University of Graz/Tzivanopoulos

Keywords: therapy resistance, cancer treatment, cytotoxic natural substances, ferroptosis, polyunsaturated fatty acids, cell membranes, chemotherapy, innovative treatment strategies, oncological research, University of Graz.