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Pancreatic stellate cells (PSCs) are a key component of tumor microenvironment in pancreatic ductal adenocarcinoma (PDAC) and contribute to drug resistance. c-MET receptor tyrosine kinase activation plays an important role in tumorigenesis in different cancers including PDAC. In this study, effects of PSC conditioned medium (PCM) on c-MET phosphorylation (by immunocytochemistry enzyme-linked immunosorbent assay (ELISA)) and drug response (by sulforhodamine B assay) were investigated in five primary PDAC cells. In novel 3D-spheroid co-cultures of cyan fluorescence protein (CFP)-firefly luciferase (Fluc)-expressing primary human PDAC cells and green fluorescence protein (GFP)-expressing immortalized PSCs, PDAC cell growth and chemosensitivity were examined by luciferase assay, while spheroids’ architecture was evaluated by confocal microscopy. The highest phospho-c-MET expression was detected in PDAC5 and its subclone sorted for “stage specific embryonic antigen-4” (PDAC5 (SSEA4)). PCM of cells pre-incubated with PDAC conditioned medium, containing increased hepatocyte growth factor (HGF) levels, made PDAC cells significantly more resistant to gemcitabine, but not to c-MET inhibitors. Hetero-spheroids containing both PSCs and PDAC5 (SSEA4) cells were more resistant to gemcitabine compared to PDAC5 (SSEA4) homo-spheroids. However, c-MET inhibitors (tivantinib, PHA-665752 and crizotinib) were equally effective in both spheroid models. Experiments with primary human PSCs confirmed the main findings. In conclusion, we developed spheroid models to evaluate PSC–PDAC reciprocal interaction, unraveling c-MET inhibition as an important therapeutic option against drug resistant PDAC.

Background Muscle-invasive bladder cancer (MIBC) treatment depends on histological subtypes. While urothelial carcinoma (UC) benefits from novel therapies, options beyond radical cystectomy for rare subtypes such as squamous cell carcinoma (SCC) remain limited. Since we previously demonstrated ATR inhibitor (ATRi) enhanced radiation sensitivity in vitro , we aimed to further decipher the therapeutic impact of ATRi and compensatory pathways bypassing ATRi-resistance in patient-derived ex vivo cultures (PDCs). Methods PDCs (p-SCC, p-UC, n  = 6) were established and characterized by immunohistochemistry, qPCR, and whole-exome sequencing. Independent ATRi-resistant cell models (p-SCC ATRi ) were generated through long-term ATRi treatment (Ceralasertib) and characterized by multi-dimensional profiling. Drug responses were analyzed via cell viability (IC50) and clonogenic survival assays ± ionizing radiation (IR). DNA repair capacity was measured via γH2AX immunofluorescence, comet assays, qPCR, and immunoblotting. ATR siRNA knockdown and ATRi short-term studies validated the ATR-RAD51 axis. RAD51 inhibitor (RAD51i) B02 was tested in p-SCC ATRi by cell cycle analysis and in ovo tumor growth of chorioallantoic membrane (CAM) xenografts, complemented by apoptosis staining. Results ATRi treatment sensitized cells to IR, reducing IC50 values up to 2.5-fold (at 8 Gy: 0.52 µM in SCC, 0.82 µM in UC). Clonogenic assays and γH2AX staining confirmed impaired DNA repair (γH2AX foci at 8 Gy: 11-fold in SCC, 15-fold in UC). In resistant p-SCC ATRi models, ATRi-adaptation triggered various compensatory and potentially epigenetic regulated DNA repair pathways, particularly homologous recombination (HR) repair involving genes like BRCA1 and RAD51 . Downstream consequences of functional ATR loss also affected non-DNA repair processes such as cell cycle, chromatin reorganization, and immunomodulation. As a therapeutic strategy, RAD51i overcame resistance by lowering IC50 by 40–80%, increasing DNA damage (2.2-fold γH2AX foci), and inducing G2/M arrest (2.4-fold). Finally, in ovo , RAD51i significantly induced apoptosis impairing tumor growth in p-SCC ATRi xenografts by up to 37%. Conclusion Our results propose ATR as a promising target in bladder cancer by (1) enhancing radio-sensitivity through classical ATR inhibition and (2) exploiting resistant ATRi-adaptation as a vulnerability by targeting compensatory HR repair reliance through RAD51 inhibition. These findings on the ATR–HR axis suggest novel strategies to improve bladder cancer treatment and addressing therapy resistance.

Multi‐drug resistance (MDR) is a major cause of cancer therapy failure. Photodynamic therapy (PDT) is a promising modality that can circumvent MDR and synergize with chemotherapies, based on the generation of reactive oxygen species (ROS) by photosensitizers. However, overproduction of glutathione (GSH) by cancer cells scavenges ROS and restricts the efficacy of PDT. Additionally, side effects on normal tissues are unavoidable after PDT treatment. Here, to develop organic systems that deliver effective anticancer PDT and chemotherapy simultaneously with very little side effects, three GSH‐sensitive photosensitizer‐drug conjugates (CyR‐SS‐L) are designed and synthesized. CyR‐SS‐L localized in the mitochondria then is cleaved into CyR‐SG and SG‐L parts by reacting with and consuming high levels of intracellular GSH. Notably, CyR‐SG generates high levels of ROS in tumor cells instead of normal cells and be exploited for PDT and the SG‐L part is used for chemotherapy. CyR‐SS‐L inhibits better MDR cancer tumor inhibitory activity than indocyanine green, a photosensitizer (PS) used for PDT in clinical applications. The results appear to be the first to show that CyR‐SS‐L may be used as an alternative PDT agent to be more effective against MDR cancers without obvious damaging normal cells by the combination of PDT, GSH depletion, and chemotherapy. A glutathione‐sensitive photosensitizer‐drug is firsted designed to simultaneously realize tumor photodynamic therapy and chemotherapy. The disulfide linkage in predrug is broken by glutathione reductase, releasing active photosensitizers and Lonidamine. Due to the synergistic effect, the expression of ATP‐binding cassette subfamily B member 1 (ABCB1) is reduced and the drug resistance pathway is broken, resulting to the efficient cancer treatment.

Drug resistance represents a major obstacle in cancer management, and the mechanisms underlying stress adaptation of cancer cells in response to therapy-induced hostile environment are largely unknown. As the central organelle for cellular energy supply, mitochondria can rapidly undergo dynamic changes and integrate cellular signaling pathways to provide bioenergetic and biosynthetic flexibility for cancer cells, which contributes to multiple aspects of tumor characteristics, including drug resistance. Therefore, targeting mitochondria for cancer therapy and overcoming drug resistance has attracted increasing attention for various types of cancer. Multiple mitochondrial adaptation processes, including mitochondrial dynamics, mitochondrial metabolism, and mitochondrial apoptotic regulatory machinery, have been demonstrated to be potential targets. However, recent increasing insights into mitochondria have revealed the complexity of mitochondrial structure and functions, the elusive functions of mitochondria in tumor biology, and the targeting inaccessibility of mitochondria, which have posed challenges for the clinical application of mitochondrial-based cancer therapeutic strategies. Therefore, discovery of both novel mitochondria-targeting agents and innovative mitochondria-targeting approaches is urgently required. Here, we review the most recent literature to summarize the molecular mechanisms underlying mitochondrial stress adaptation and their intricate connection with cancer drug resistance. In addition, an overview of the emerging strategies to target mitochondria for effectively overcoming chemoresistance is highlighted, with an emphasis on drug repositioning and mitochondrial drug delivery approaches, which may accelerate the application of mitochondria-targeting compounds for cancer therapy.

Trafficking of biological material across membranes is an evolutionary conserved mechanism and is part of any normal cell homeostasis. Such transport is composed of active, passive, export through microparticles, and vesicular transport (exosomes) that collectively maintain proper compartmentalization of important micro- and macromolecules. In pathological states, such as cancer, aberrant activity of the export machinery results in expulsion of a number of key proteins and microRNAs resulting in their misexpression. Exosome-mediated expulsion of intracellular drugs could be another barrier in the proper action of most of the commonly used therapeutics, targeted agents, and their intracellular metabolites. Over the last decade, a number of studies have revealed that exosomes cross-talk and/or influence major tumor-related pathways, such as hypoxia-driven epithelial-to-mesenchymal transition, cancer stemness, angiogenesis, and metastasis involving many cell types within the tumor microenvironment. Emerging evidence suggests that exosome-secreted proteins can also propel fibroblast growth, resulting in desmoplastic reaction, a major barrier in effective cancer drug delivery. This comprehensive review highlights the advancements in the understanding of the biology of exosomes secretions and the consequence on cancer drug resistance. We propose that the successful combination of cancer treatments to tackle exosome-mediated drug resistance requires an interdisciplinary understanding of these cellular exclusion mechanisms, and how secreted biomolecules are involved in cellular cross-talk within the tumor microenvironment.

Cancer drug resistance represents the main obstacle in cancer treatment. Drug-resistant cancers exhibit complex molecular mechanisms to hit back therapy under pharmacological pressure. As a reversible epigenetic modification, N 6 -methyladenosine (m 6 A) RNA modification was regarded to be the most common epigenetic RNA modification. RNA methyltransferases (writers), demethylases (erasers), and m 6 A-binding proteins (readers) are frequently disordered in several tumors, thus regulating the expression of oncoproteins, enhancing tumorigenesis, cancer proliferation, development, and metastasis. The review elucidated the underlying role of m 6 A in therapy resistance. Alteration of the m 6 A modification affected drug efficacy by restructuring multidrug efflux transporters, drug-metabolizing enzymes, and anticancer drug targets. Furthermore, the variation resulted in resistance by regulating DNA damage repair, downstream adaptive response (apoptosis, autophagy, and oncogenic bypass signaling), cell stemness, tumor immune microenvironment, and exosomal non-coding RNA. It is highlighted that several small molecules targeting m 6 A regulators have shown significant potential for overcoming drug resistance in different cancer categories. Further inhibitors and activators of RNA m 6 A-modified proteins are expected to provide novel anticancer drugs, delivering the therapeutic potential for addressing the challenge of resistance in clinical resistance.

To become resistant, cancer cells need to activate and maintain molecular defense mechanisms that depend on an energy trade-off between resistance and essential functions. Metabolic reprogramming has been shown to fuel cell growth and contribute to cancer drug resistance. Recently, changes in lipid metabolism have emerged as an important driver of resistance to anticancer agents. In this review, we highlight the role of choline metabolism with a focus on the phosphatidylcholine cycle in the regulation of resistance to therapy. We analyze the contribution of phosphatidylcholine and its metabolites to intracellular processes of cancer cells, both as the major cell membrane constituents and source of energy. We further extended our discussion about the role of phosphatidylcholine-derived lipid mediators in cellular communication between cancer and immune cells within the tumor microenvironment, as well as their pivotal role in the immune regulation of therapeutic failure. Changes in phosphatidylcholine metabolism are part of an adaptive program activated in response to stress conditions that contribute to cancer therapy resistance and open therapeutic opportunities for treating drug-resistant cancers.

This review provides a comprehensive synthesis of current knowledge on immunotherapy resistance in non-small cell lung cancer (NSCLC), a disease that accounts for approximately 85% of all lung cancer cases and remains the leading cause of cancer-related death worldwide. Although immune checkpoint inhibitors (ICIs) have significantly improved survival for a subset of patients with advanced NSCLC, over 70% of cases ultimately exhibit primary or acquired resistance, underscoring the urgent need to understand the underlying mechanisms. The review categorizes resistance into tumor-intrinsic and tumor-extrinsic processes and provides an in-depth mechanistic analysis of how factors such as tumor antigen loss, impaired antigen presentation, cGAS-STING pathway dysregulation, metabolic reprogramming in tumor microenvironment (TME), immune cell exhaustion, and microbiomes collectively contribute to immune escape. In parallel, the influence of the lung and gut microbiome on shaping immunotherapy responses is discussed, with emphasis on microbial dysbiosis, immunosuppressive metabolite production, and TME remodeling. Therapeutic strategies to overcome resistance are also discussed, including combination approaches involving chemotherapy, radiotherapy, and antiangiogenic agents, as well as epigenetic modulators (HDAC and BET inhibitors). Moreover, the review explores bispecific antibodies, antibody-drug conjugates, and small-molecule agents that enhance T cell function or disrupt immunosuppressive signaling networks. By integrating insights from preclinical models and clinical trials, the review underscores the necessity of biomarker-guided patient stratification, combination immunotherapy approaches, and interventions that restore tumor immunogenicity. It concludes that a multipronged therapeutic strategy, one that addresses both immune evasion and TME-induced suppression, holds the greatest promise for improving response durability and advancing personalized immunotherapy for NSCLC.

Extracellular vesicles (EVs) are key mediators in the communication between cancer cells and their microenvironment, significantly influencing drug resistance. This review provides a comprehensive analysis of the roles of EVs in promoting drug resistance through mechanisms such as drug efflux, apoptosis resistance, autophagy imbalance, and tumor microenvironment modulation. Despite extensive research, details of EVs biogenesis, cargo selection, and specific pathways in EVs-mediated drug resistance are not fully understood. This review critically examines recent advancements, highlighting key studies that elucidate the molecular mechanisms of EVs functions. Additionally, innovative therapeutic strategies targeting EVs are explored, including inhibiting EVs biogenesis, engineering EVs for drug delivery, and identifying resistance-inhibiting molecules within EVs. By integrating insights from primary research and proposing new directions for future studies, this review aims to advance the understanding of EVs in cancer biology and foster effective interventions to mitigate drug resistance in cancer therapy.