MicroRNAs are small, non-coding RNA molecules, typically only 19 to 25 nucleotides in length, that do not encode proteins but instead regulate gene expression after transcription. Their mechanism of action is elegant in its simplicity: a microRNA associates with a protein complex known as the RNA-induced silencing complex, or RISC, and uses its sequence to recognize complementary stretches of messenger RNA, most commonly within the 3′-untranslated region of target transcripts. When binding occurs, the microRNA either promotes degradation of the messenger RNA or blocks its translation into protein, effectively turning down the volume on specific genes. Because a single microRNA can target hundreds of different messenger RNAs, and because each messenger RNA can be regulated by multiple microRNAs, these molecules form dense regulatory networks that influence virtually every cellular pathway. In the liver, where microRNAs help maintain the delicate balance between regeneration and quiescence, disruption of these networks can tip cells toward malignant transformation.

What makes microRNAs particularly fascinating in the context of cancer is their dual nature. Depending on the genes they target, individual microRNAs can act either as oncogenes, promoting tumor growth when they suppress protective factors, or as tumor suppressors, restraining cancer when they silence growth-promoting genes. The new review catalogs dozens of examples of this duality in hepatocellular carcinoma. Tumor-suppressive microRNAs frequently rein in the activity of critical signaling cascades, whereas oncogenic microRNAs, often overproduced in tumor cells, dismantle the cell’s natural brakes on proliferation. This yin-and-yang quality means that therapeutic strategies must be carefully tailored: restoring a lost tumor-suppressive microRNA requires replenishing it, while silencing an overactive oncogenic microRNA demands inhibitors, often chemically modified antisense oligonucleotides designed to bind and neutralize the offending molecule.

At the heart of the review’s technical analysis lies the interplay between microRNAs and four major signaling pathways that dominate hepatocellular carcinoma biology. The first, the Wnt/β-catenin pathway, is a master regulator of liver development and regeneration. In healthy cells, the protein β-catenin is continuously targeted for destruction by a destruction complex containing the adenomatous polyposis coli protein, or APC, and axis inhibition protein, Axin, along with glycogen synthase kinase 3 beta. When this complex is disabled, β-catenin accumulates, enters the nucleus, and partners with T-Cell Factor 4 to activate genes driving cell division. The review describes how microRNAs can influence this pathway at multiple points, either promoting β-catenin degradation or, conversely, silencing its negative regulators such as PTEN, the phosphatase and tensin homolog that restrains parallel growth signaling. The result is a pathway that tumor cells exploit with remarkable consistency, and one that microRNA-based therapies could theoretically recalibrate.

The second major axis involves the PI3K/AKT/mTOR pathway, a growth-control circuit that transduces signals from receptor tyrosine kinases at the cell surface into metabolic and survival programs within the cell. When phosphatidylinositol phosphate signaling activates AKT, the kinase phosphorylates a host of downstream targets, including members of the Forkhead box O transcription factor family, promoting cell survival and blocking programmed cell death. Multiple microRNAs in hepatocellular carcinoma converge on this pathway, frequently by suppressing PTEN, the lipid phosphatase whose loss unleashes unrestrained AKT signaling. The review also highlights the TGF-β/Smad pathway, a signaling system with paradoxical roles that suppress tumor growth early in carcinogenesis but later fuel invasion and metastasis through epithelial-mesenchymal transition, a process in which epithelial cancer cells shed their adhesive properties and acquire the motile, invasive characteristics of mesenchymal cells. Transcription factors such as Zinc finger E-box binding homeobox 1, or ZEB1, orchestrate this transition, and microRNAs that regulate ZEB1 and related factors can either accelerate or restrain metastatic spread. Finally, the MAPK/ERK cascade, which relays signals from the Kirsten rat sarcoma viral oncogene homolog, KRAS, through rapidly accelerated fibrosarcoma, RAF, and mitogen-activated protein kinase kinase, MEK, to extracellular signal-regulated kinase, ERK, is another frequent microRNA target, with regulators such as the Sprouty RTK signaling antagonist 2 modulating the intensity of proliferative signals.

Beyond these canonical pathways, the review devotes considerable attention to how microRNAs reshape the tumor microenvironment, the complex ecosystem of immune cells, fibroblasts, blood vessels and extracellular matrix that surrounds and supports the tumor. Hepatocellular carcinoma is a notoriously inflammatory cancer, arising most often in livers scarred by chronic hepatitis B virus infection, hepatitis C virus infection, alcohol-related damage or metabolic dysfunction-associated steatotic liver disease. Within the tumor microenvironment, tumor-associated macrophages, cancer-associated fibroblasts and hepatic stellate cells communicate with malignant cells through cytokines and chemokines, including C-C motif chemokine ligand 2 and macrophage migration inhibitory factor. MicroRNAs mediate much of this crosstalk. Some microRNAs secreted by tumor cells within extracellular vesicles travel to recipient immune cells and reprogram them toward a pro-tumor state, dampening the activity of natural killer cells and cytotoxic T lymphocytes. Others influence the expression of programmed death-ligand 1, PD-L1, the molecular shield that tumors use to evade immune checkpoint blockade, suggesting that microRNA levels could predict which patients will respond to immunotherapy. Hypoxia-inducible factor 1 alpha, the master transcriptional response to low oxygen, also intersects with microRNA networks to promote angiogenesis and metabolic adaptation in oxygen-starved tumor regions.

Metabolic reprogramming, a hallmark of cancer in which tumor cells alter how they generate energy and build biomass, emerges as another major theme. The review details how microRNAs regulate glycolysis through targets such as hexokinase 2, modulate glutamine and serine metabolism, and restructure lipid biochemistry by controlling enzymes including stearoyl-CoA desaturase-1, glycerol-3-phosphate acyltransferase, and carnitine palmitoyl transferase 1C, which governs fatty acid oxidation. MicroRNAs also influence the mevalonate pathway, fatty acid-binding proteins, and the consumption of coenzyme Q10 within mitochondrial fatty acid oxidation complexes such as hydroxyacyl-CoA dehydrogenase trifunctional multienzyme complex subunit alpha. Even lactate transport, through monocarboxylate transporter 1, falls under microRNA control. These metabolic regulators matter clinically because metabolic dysfunction-associated steatotic liver disease and its inflammatory progression to metabolic dysfunction-associated steatohepatitis are rapidly becoming leading drivers of liver cancer worldwide, meaning that microRNA networks sit at the intersection of tumor metabolism and the metabolic disease environment of the host liver.

The review also addresses how microRNAs shape more specialized malignant behaviors, including the maintenance of cancer stem cells, the subpopulation of tumor cells capable of self-renewal and of seeding recurrence after treatment. Epigenetic regulators such as SET domain bifurcated histone lysine methyltransferase 1 and the chromobox homolog 4 protein, as well as DNA repair and stress-response factors including BRCA1-associated protein 1, superoxide dismutase 1, and the solute carrier family 7 member 11 involved in antioxidant defense, are all subject to microRNA regulation. Long noncoding RNAs and circular RNAs add another layer of complexity, acting as molecular sponges that sequester microRNAs and thereby soften their repressive effects, a phenomenon known as competing endogenous RNA regulation. This dense interplay among RNA species means that microRNA activity in a tumor reflects not just its own abundance but the entire non-coding RNA landscape, offering a rich source of potential biomarkers.

On the clinical translation front, the authors evaluate microRNAs both as diagnostic tools and as therapeutic targets. Circulating microRNAs in blood plasma and serum are remarkably stable, protected from degradation by association with proteins or enclosure in extracellular vesicles, making them attractive minimally invasive biomarkers, so-called liquid biopsies, for detecting hepatocellular carcinoma earlier and monitoring treatment response. On the therapeutic side, the field has already produced one landmark success: the tumor-suppressive microRNA mimic known as TargomiRs and, more pertinently for liver disease, the microRNA-122 antisense inhibitor miravirsen, which reached clinical testing as an antiviral agent against hepatitis C virus. For hepatocellular carcinoma itself, strategies under investigation include viral vectors carrying tumor-suppressive microRNAs, lipid nanoparticles delivering microRNA mimics, and antisense oligonucleotides silencing oncogenic microRNAs. Challenges remain formidable, however, including targeted delivery to tumor cells while sparing healthy hepatocytes, the risk that a single microRNA affects unintended genes in normal tissue, dose-limiting toxicity, and the heterogeneity of microRNA expression among patients.

The authors emphasize that these obstacles, while significant, are not insurmountable. Advances in extracellular vesicle engineering, chemically stabilized nucleic acid therapeutics, and combination regimens pairing microRNA therapies with existing multitarget tyrosine kinase inhibitors or immune checkpoint inhibitors are steadily expanding the therapeutic toolkit. The regulatory networks mapped in this review provide a roadmap for identifying which microRNA interventions are most likely to synergize with current treatments, and which patient subgroups, defined by viral etiology, metabolic status or molecular subtype, stand to benefit most. As hepatocellular carcinoma continues to claim hundreds of thousands of lives each year, the humble microRNA, a molecule barely two decades old in the scientific consciousness, is proving to be far more than a curiosity; it is emerging as a central orchestrator of cancer biology and a genuinely promising frontier in the fight against one of humanity’s most lethal cancers. The research was supported by the National Natural Science Foundation of China and the Science and Technology Research Program of Chongqing Municipal Education Commission.

Topotecan, a topoisomerase I inhibitor, functions by stabilizing the DNA-topoisomerase I complex, leading to DNA damage and ultimately cell death. Despite its efficacy in a variety of solid tumors including ovarian and small cell lung cancers, clinical outcomes are often hampered by the emergence of resistance. Recent research has begun illuminating how ncRNAs—segments of RNA that do not encode proteins but regulate gene expression and cellular processes—play a formidable role in this resistance phenomenon. Among these, microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) stand out as key modulators.

The systematic review underlines that miRNAs frequently act as either tumor suppressors or oncogenes, and their dysregulation can drastically influence Topotecan sensitivity. By targeting messenger RNAs (mRNAs) of genes involved in apoptosis, cell cycle regulation, and drug efflux, miRNAs fine-tune the cellular responses to DNA damage induced by Topotecan. For example, downregulation of specific tumor-suppressive miRNAs often leads to enhanced expression of proteins that mediate drug resistance, such as transporters responsible for drug efflux like ABC transporters, which actively pump Topotecan out of cancer cells, reducing intracellular drug concentrations.

Long non-coding RNAs also manifest as crucial players in shaping chemotherapy outcomes. Unlike miRNAs, lncRNAs exert their influence through diverse mechanisms including chromatin remodeling, acting as molecular sponges for miRNAs, or interacting with transcription factors and signaling molecules. The review presents compelling evidence that aberrantly expressed lncRNAs interfere with apoptotic pathways and DNA repair mechanisms, thereby mitigating the cytotoxic effects of Topotecan. In some cases, lncRNAs promote the epithelial-to-mesenchymal transition (EMT), a cellular state associated with enhanced invasiveness and resistance to chemotherapy.

Furthermore, circular RNAs, the relatively recently characterized class of ncRNAs distinguished by their covalently closed loop structure, emerge as intricate regulatory hubs. Their ability to act as miRNA sponges enables them to indirectly regulate gene expression in ways that affect cell survival and drug response. Specific circRNAs have been identified that enhance resistance by interfering with signaling cascades central to the DNA damage response, thereby attenuating the efficacy of Topotecan.

Delving deeper, the interactions among these various ncRNA species weave a complex regulatory network that modulates gene expression far beyond individual effects. These networks orchestrate a delicate balance between pro-survival and pro-death signals within cancer cells exposed to Topotecan. For instance, a lncRNA may sequester a miRNA that ordinarily suppresses a drug resistance gene, creating an axis that favors tumor survival. Understanding these ncRNA-mediated axes could pave the way for innovative therapeutic strategies that aim to dismantle the resistance machinery at multiple regulatory checkpoints simultaneously.

The clinical implications of these findings are profound. By profiling the expression patterns of ncRNAs in tumor biopsies, oncologists may be able to predict patient responses to Topotecan more accurately. Moreover, ncRNAs themselves or their molecular targets could serve as novel biomarkers for resistance, aiding in the customization of chemotherapy regimens and improving patient outcomes through precision medicine approaches.

Therapeutically, the prospect of modulating ncRNAs to re-sensitize tumors to Topotecan is an exhilarating avenue under active exploration. Approaches such as siRNA-mediated knockdown of oncogenic ncRNAs, delivery of synthetic tumor-suppressive miRNAs, or the use of small molecules that disrupt ncRNA interactions hold significant promise. However, these strategies face numerous challenges, including efficient delivery to tumor cells, off-target effects, and immune activation. Advances in nanoparticle-based delivery systems and exosome engineering may overcome these hurdles, ushering in a new era of ncRNA-based adjuvant therapies.

Another dimension highlighted by the review is the dynamic and context-dependent expression of ncRNAs, influenced by the tumor microenvironment and chemotherapy-induced stress. Hypoxia, inflammation, and stromal interactions all modulate ncRNA profiles, potentially reshaping Topotecan sensitivity over the course of treatment. This underscores the necessity for longitudinal monitoring of ncRNA changes during therapy to enable timely adjustments of treatment plans.

At the molecular level, studies employing transcriptomic and epigenomic profiling reveal that ncRNAs participate extensively in DNA repair pathways that are critical for overcoming Topotecan-induced damage. For example, ncRNAs can influence homologous recombination and non-homologous end joining repair mechanisms, which determine the fate of DNA strand breaks. By modulating these pathways, ncRNAs directly affect the efficacy of Topotecan’s cytotoxic action.

The interplay between ncRNAs and key signaling pathways such as PI3K/Akt, Wnt/β-catenin, and NF-κB further complicates the landscape of Topotecan resistance. These pathways orchestrate cellular survival, proliferation, and apoptosis and are frequently altered in resistant tumors. NcRNAs can regulate the expression and activity of pivotal components within these cascades, thereby reinforcing survival signals despite chemotherapeutic insult.

Given the multifaceted role of ncRNAs in cancer biology and drug resistance, there is an increasing rationale to integrate ncRNA profiling into combination therapeutic strategies. Combining Topotecan with agents that target ncRNAs or their downstream effectors could break resistance loops and achieve synergistic tumor killing. Preclinical models and early-phase clinical trials exploring such combinatorial approaches are eagerly awaited.

Importantly, the systematic review draws attention to the heterogeneity in ncRNA patterns across different cancer types and even within subpopulations of tumor cells. This heterogeneity necessitates the development of tailored ncRNA-targeted interventions adapted to specific tumor contexts. Advances in single-cell sequencing technologies and bioinformatics are instrumental in dissecting this complexity and uncovering personalized resistance mechanisms.

Ethical and practical considerations also come to the forefront as the field moves towards ncRNA-based diagnostics and therapeutics. Standardization of ncRNA detection methods, validation in large patient cohorts, and assessment of long-term safety profiles are essential steps before routine clinical translation. Nonetheless, the landscape is rapidly evolving, propelled by a deeper understanding of ncRNA biology and innovative biotechnologies.

In summation, the recognition of non-coding RNAs as central architects in the modulation of cancer cell sensitivity to Topotecan marks a significant paradigm shift. This knowledge transcends traditional views centered on protein-coding genes and drug metabolism enzymes, revealing a nuanced, multilayered regulatory network. Exploiting this new understanding holds the promise of transforming therapeutic strategies and overcoming one of the most critical obstacles in cancer treatment: chemoresistance.

As research accelerates, the marriage of molecular insights into ncRNAs with precision oncology could herald a new epoch where overcoming resistance is achievable not only through targeting cancer proteins but also by reprogramming the non-coding genome itself. This approach has the potential to redefine patient prognosis and reshape the future of cancer chemotherapy.

Subject of Research: Non-coding RNAs and their role in modulating cancer cell sensitivity to Topotecan chemotherapy.

Article Title: Non-coding RNAs’ pivotal importance in modulation of cancer sensitivity to Topotecan: a systematic review.

Article References:
Rahimi, S.M., Bagheri, A. Non-coding RNAs’ pivotal importance in modulation of cancer sensitivity to Topotecan: a systematic review. Med Oncol 42, 470 (2025). https://doi.org/10.1007/s12032-025-03029-0

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