Tumor hypoxia and radiotherapy: A major driver of resistance even for novel radiotherapy modalities

Radiosensitization Strategies for Hepatocellular Carcinoma: Mechanisms, Therapeutic Advances, and Clinical Perspectives

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related mortality worldwide, with treatment efficacy limited by late-stage diagnosis, frequent recurrence, and therapeutic resistance. Radiotherapy is a key local treatment for HCC; however, its efficacy is frequently limited by intrinsic tumor radioresistance. This review discusses strategies to improve the therapeutic response of HCC to radiotherapy. Targeting DNA repair mechanisms can block tumor cells from recovering after radiation-induced damage, whereas modulating cell cycle arrest and programmed cell death pathways (e.g., apoptosis, autophagy) diminishes their survival capacity. Furthermore, remodeling the tumor microenvironment-through hypoxia alleviation, metabolic reprogramming, oxidative stress regulation, and immune activation-may potentiate radiotherapy efficacy. Technological advances, such as stereotactic body radiotherapy and nanomaterial-based approaches, have also improved the precision and effectiveness of radiotherapy. Clinically, combining radiotherapy with systemic therapies (e.g., immune checkpoint inhibitors and antiangiogenic agents) has demonstrated preliminary promise in enhancing treatment outcomes. However, translating preclinical findings into clinical practice remains challenging due to tumor heterogeneity, normal tissue toxicity, and the lack of predictive biomarkers for treatment selection. Future research should focus on integrating molecular profiling with multimodal therapies to enable personalized radiosensitization and bridge the gap between mechanistic insights and clinical outcomes.

Mitigating radioresistance mechanisms by polymer-lipid manganese dioxide nanoparticles enhances immunogenic cell death and antitumor immune response to facilitate abscopal effect in breast tumor models

Breast cancer is the most diagnosed cancer and the second leading cause of cancer death in women. Although treatments with major anti-cancer modalities are largely successful, resistance to treatments including widely applied radiation therapy (RT) can occur due largely to the multifaceted mechanisms in the tumor microenvironment (TME). The present work investigated the ability of Polymer-Lipid-Manganese Dioxide Nanoparticles (PLMD) to overcome hypoxia-associated radioresistant mechanisms and enhance RT-induced immunogenic cell death (ICD) and anti-tumor immunity for inhibiting growth of primary and distant tumors (the abscopal effect). The results showed that PLMD plus RT significantly inhibited the clonogenic survival of murine EMT6 and 4T1 breast cancer cells under hypoxic condition compared to RT alone. Analysis of ICD biomarkers revealed that PLMD profoundly enhanced RT-induced ICD compared to RT alone in EMT6 and 4T1 cells under hypoxic conditions but not under normoxic conditions. In a syngeneic murine breast tumor model with 4T1 orthotopic tumor, the PLMD treatment reduced tumor hypoxia significantly; PLMD + RT combination therapy increased infiltration of cytotoxic CD8+ T cells and CD86+ macrophages and decreased infiltration of immunosuppressive Tregs and CD163+ macrophages, as compared to RT alone. Importantly, the PLMD + RT treatment generated an abscopal effect in a tumor growth experiment using a double-tumor model, where the growth of an untreated tumor was inhibited by treatment of a tumor grown on the opposite side. Overall, the PLMD + RT induced an anti-tumor immune response that inhibited both primary and distant tumor growths and extended median survival in the tumor model.

Dopamine and Mn(II) Chelate Covalent-Doping Coated Ti(IV)-Nanotheranostics for Magnetic Resonance Imaging Guided Phototherapy in Oral Cancer

Purpose

Phototherapy have gained significant traction in the treatment of tumors. However, the successful implementation of these therapies relies on photosensitizers with superior properties and precise guidance mechanisms.

Methods

In this study, we introduce an innovative method for the surface modification of titanium dioxide (TiO2) nanoparticles through HRP-catalyzed covalent incorporation of Mn(II) chelate (Mn-Dopa) and dopamine.

Results

This modification extends TiO2 nanoparticels' light absorption from ultraviolet to the near-infrared (NIR) range, endowing the nanoparticles with MRI-guided phototherapy capabilities. The resulting nanotheranostics system, TiO2@PDA-MnDopa, demonstrated over 5-fold enhanced relaxivity compared to the monomeric MnDopa and exhibited synergistic phototherapy effects upon 808 nm laser excitation, with a photothermal conversion efficiency of 15.91%. In vitro and in vivo pharmacodynamics studies showed that the TiO2@PDA-MnDopa demonstrated good safety in the HSC3 cell line and corresponding tumor-bearing mice, while effectively inhibiting tumor growth under 808 nm laser excitation.

Conclusion

This multifunctional nanotheranostic, integrating high relaxivity with synergistic PTT/PDT for MR imaging-guided phototherapy, holds great potential for applications in the early diagnosis, noninvasive treatment, and prognostic evaluation of oral squamous cell carcinoma.

Stereotactic radiosurgery for patients with brain metastases: current principles, expanding indications and opportunities for multidisciplinary care

The management of brain metastases is challenging and should ideally be coordinated through a multidisciplinary approach. Stereotactic radiosurgery (SRS) has been the cornerstone of management for most patients with oligometastatic central nervous system involvement (one to four brain metastases), and several technological and therapeutic advances over the past decade have broadened the indications for SRS to include polymetastatic central nervous system involvement (>4 brain metastases), preoperative application and fractionated SRS, as well as combinatorial approaches with targeted therapy and immune-checkpoint inhibitors. For example, improved imaging and frameless head-immobilization technologies have facilitated fractionated SRS for large brain metastases or postsurgical cavities, or lesions in proximity to organs at risk. However, these opportunities come with new challenges and questions, including the implications of tumour histology as well as the role and sequencing of concurrent systemic treatments. In this Review, we discuss these advances and associated challenges in the context of ongoing clinical trials, with insights from a global group of experts, including recommendations for current clinical practice and future investigations. The updates provided herein are meaningful for all practitioners in clinical oncology.

miR-210: A non-invasive biomarker for hypoxia-driven lung cancer diagnosis and therapy

Lung cancer is one of the major cancer-related deaths in the world due to the low success rate in invasive diagnostic procedures and late staging. Hypoxia-associated molecular signatures have received attention due to a growing demand for non-invasive prognostic biomarkers, and miR-210 has been repoured as the only viable candidate. Tumor hypoxia is a characteristic of highly malignant lung cancer, and hypoxia-inducible factors increase miR-210 in this process as a way of allowing cancer cells to inhabit low oxygen conditions and grow further in lung cancer. MiR-210 takes up the responsibility of angiogenesis, survival, and metastasis. Notably, miR-210 is located downstream as a non-invasive diagnostic biomarker because of its stability and measurability in biofluids, including serum and plasma. Existing techniques, which can accurately detect miR-210 employing liquid biopsy and quantitative reverse transcription polymerase chain reaction (qRT-PCR), provide sensitivity and specificity, making it possible for early detection of hypoxic cancers. In addition to diagnostics, miR-210 is a cure different from other existing treatments as they show lesser efficiency because of hypoxia-resistant genes that may be suppressed by using miR-210. While it holds great promise, such problems as biological variation and the uniformity of the detection techniques may need further research. MiR-210 holds significant possibilities in Lung cancer diagnosis and treatment; however, there is a need for further investigation and confirmation to place miR-210 in the list of biomarkers for customized medicine.

A Nanoradiosensitizer Potentiates Tumor Radiotherapy through JFK Inhibition and Hypoxia Alleviation

Radiotherapy (RT) is a primary treatment for breast cancer, but its effectiveness is often compromised by hypoxia and intrinsic resistance mechanisms. The F-box protein JFK is overexpressed in breast cancer and is associated with reduced radiosensitivity, but specific JFK inhibitors are currently unavailable. Herein, we developed spherical nanoparticles (SNP-JC) designed to co-deliver small interfering RNA targeting JFK and catalase to the tumor, aiming to silence JFK and alleviate hypoxia to overcome RT resistance. Positron emission tomography imaging demonstrated that SNP-JC efficiently accumulated in the tumors. SNP-JC significantly increased DNA damage in tumor cells after RT and promoted the immunogenic cell death. The combination of SNP-JC and RT activated CD8+ T cells and elicited a robust antitumor immunity, resulting in suppressed primary tumor growth and reduced lung metastasis. Our findings demonstrate that a nanoplatform capable of simultaneously silencing JFK and mitigating hypoxia can enhance tumor radiosensitivity, improve antitumor efficacy, and prevent metastasis.

Hydrogen-Bonded Organic Framework Nanoscintillators for X-Ray-Induced Photodynamic Therapy in Hepatocellular Carcinoma

X-ray induced photodynamic therapy (X-PDT) leverages penetrating X-ray to generate singlet oxygen (1O2) for treating deep-seated tumors. However, conventional X-PDT typically relies on heavy metal inorganic scintillators and organic photosensitizers to produce 1O2, which presents challenges related to toxicity and energy conversion efficiency. In this study, highly biocompatible organic phosphorescent nanoscintillators based on hydrogen-bonded organic frameworks (HOF) are designed and engineered, termed BPT-HOF@PEG, to enhance X-PDT in hepatocellular carcinoma (HCC) treatment. BPT-HOF@PEG functions simultaneously as both scintillator and photosensitizer, effectively absorbing and transferring X-ray energy to generate abundant 1O2. Both in vitro and in vivo investigations demonstrate that internalized BPT-HOF@PEG efficiently produces significant quantities of 1O2 upon X-ray irradiation. Additionally, X-ray exposure directly inflicts DNA damage, and the synergistic effects of these mechanisms result in pronounced cell death and substantial tumor growth inhibition, with a significant inhibition rate of up to 90.4% in vivo assessments. RNA sequencing analyses reveal that X-PDT induces apoptosis in Hepa1-6 cells while inhibiting cell proliferation, culminating in tumor cell death. Therefore, this work highlights the considerable potential of efficient phosphorescent HOF nanoscintillators-based X-PDT as a promising therapeutic approach for HCC, providing a highly effective alternative with negligible toxicity for patients with unresectable tumors.

Tumor‑associated neutrophils: Critical regulators in cancer progression and therapeutic resistance (Review)

Cancer is the second leading cause of death among humans worldwide. Despite remarkable improvements in cancer therapies, drug resistance remains a significant challenge. The tumor microenvironment (TME) is intimately associated with therapeutic resistance. Tumor‑associated neutrophils (TANs) are a crucial component of the TME, which, along with other immune cells, play a role in tumorigenesis, development and metastasis. In the current review, the roles of TANs in the TME, as well as the mechanisms of neutrophil‑mediated resistance to cancer therapy, including immunotherapy, chemotherapy, radiotherapy and targeted therapy, were summarized. Furthermore, strategies for neutrophil therapy were discussed and TANs were explored as potential targets for cancer treatment. In conclusion, the need to explore the precise roles, recruitment pathways and mechanisms of action of TANs was highlighted for the purpose of developing therapies that precisely target TANs and reverse drug resistance.

Predictors of Radiation Resistance and Novel Radiation Sensitizers in Head and Neck Cancers: Advancing Radiotherapy Efficacy

Radiation resistance in head and neck squamous cell carcinoma (HNSCC), driven by intrinsic and extrinsic factors, poses a significant challenge in radiation oncology. The key contributors are tumor hypoxia, cancer stem cells, cell cycle checkpoint activation, and DNA repair processes (homologous recombination and non-homologous end-joining). Genetic modifications such as TP53 mutations, KRAS mutations, EGFR overexpression, and abnormalities in DNA repair proteins like BRCA1/2 additionally affect radiation sensitivity. Novel radiosensitizers targeting these pathways demonstrate the potential to overcome resistance. Hypoxia-activated drugs and gold nanoparticles enhance the efficacy of radiotherapy and facilitate targeted distribution. Integrating immunotherapy, especially immune checkpoint inhibitors, with radiation therapy, enhances anti-tumor responses and reduces resistance. Epigenetic alterations, such as DNA methylation and histone acetylation, significantly influence radiation response, with the potential for sensitization through histone deacetylase inhibitors and non-coding RNA regulators. Metabolic changes linked to glucose, lipid, and glutamine metabolism influence radiosensitivity, uncovering new targets for radiosensitization. Human papillomavirus (HPV)-associated malignancies exhibit increased radiosensitivity relative to other tumors due to impaired DNA repair mechanisms and heightened immunogenicity. Furthermore, understanding the interplay between HPV oncoproteins and p53 functionality can enhance treatment strategies for HPV-related cancers. Using DNA damage response inhibitors (PARP, ATM/ATR), cell cycle checkpoint inhibitors (WEE1, CHK1/2), and hypoxia-targeted agents as radiosensitizing strategies exhibit considerable promise. Immunomodulatory approaches, including PD-1 and CTLA-4 inhibitors in conjunction with radiation, enhance anti-tumor immunity. Future directions emphasize personalized radiation therapy using genetics, sophisticated medication delivery systems, adaptive radiotherapy, and real-time monitoring. These integrated strategies seek to diminish radiation resistance and improve therapeutic efficacy in HNSCC.

Hypoxia Imaging in Lung Cancer: A PET-Based Narrative Review for Clinicians and Researchers

Background: Hypoxia plays a critical role in lung cancer progression and treatment resistance by contributing to aggressive tumor behavior and poor therapeutic response. Molecular imaging, particularly positron emission tomography (PET), has become an essential tool for noninvasive hypoxia detection, providing valuable insights into tumor biology and aiding in personalized treatment strategies. Objective: This narrative review explores recent advancements in PET imaging for detecting hypoxia in lung cancer, with a focus on the development, characteristics, and clinical applications of various radiotracers. Findings: Numerous PET-based hypoxia radiotracers have been investigated, each with distinct pharmacokinetics and imaging capabilities. Established tracers such as 18F-Fluoromisonidazole (18F-FMISO) remain widely used, while newer alternatives like 18F-Fluoroazomycin Arabinoside (18F-FAZA) and 18F-Flortanidazole (18F-HX4) demonstrate improved clearance and image contrast. Additionally, 64Cu-ATSM has gained attention for its rapid tumor uptake and hypoxia selectivity. The integration of PET with hybrid imaging modalities, such as PET/CT and PET/MRI, enhances the spatial resolution and functional interpretation, making hypoxia imaging a promising approach for guiding radiotherapy, chemotherapy, and targeted therapies. Conclusions: PET imaging of hypoxia offers significant potential in lung cancer diagnosis, treatment planning, and therapeutic response assessment. However, challenges remain, including tracer specificity, quantification variability, and standardization of imaging protocols. Future research should focus on developing next-generation radiotracers with enhanced specificity, optimizing imaging methodologies, and leveraging multimodal approaches to improve clinical utility and patient outcomes.

Unraveling the triad of hypoxia, cancer cell stemness, and drug resistance

In the domain of addressing cancer resistance, challenges such as limited effectiveness and treatment resistance remain persistent. Hypoxia is a key feature of solid tumors and is strongly associated with poor prognosis in cancer patients. Another significant portion of the development of acquired drug resistance is attributed to tumor stemness. Cancer stem cells (CSCs), a small tumor cell subset with self-renewal and proliferative abilities, are crucial for tumor initiation, metastasis, and intra-tumoral heterogeneity. Studies have shown a significant association between hypoxia and CSCs in the context of tumor resistance. Recent studies reveal a strong link between hypoxia and tumor stemness, which together promote tumor survival and progression during treatment. This review elucidates the interplay between hypoxia and CSCs, as well as their correlation with resistance to therapeutic drugs. Targeting pivotal genes associated with hypoxia and stemness holds promise for the development of novel therapeutics to combat tumor resistance.

Highly efficient tumor oxygen supplementation MnO2 nano-MOF encapsulated Sorafenib for multiple synergistic CDT/PDT/RT

Tumor growth often creates hypoxic conditions within the tumor microenvironment, which can limit the effectiveness of therapies. To address this issue, a novel "all-in-one" nanoplatform called PCN-224(Hf)@Sorafenib@(PSM) has been developed. This nanoplatform utilizes PCN-224(Hf)-modified MnO2 and combines various therapeutic modalities-chemotherapy, chemodynamic therapy (CDT), photodynamic therapy (PDT), and radiotherapy (RT)-to enhance treatment efficacy. In the PSM nanoplatform, MnO2 decomposes H2O2 to produce oxygen (O2) and reacts with glutathione (GSH) to form Mn2+. This process catalyzes a Fenton-like reaction that generates hydroxyl radicals (·OH), facilitating CDT. When exposed to 635 nm light irradiation, the porphyrin ligand in PCN-224(Hf) produces singlet oxygen (1O2), while the Hf6 clusters contribute to the PDT effects. Furthermore, the nanoplatform enhances radiotherapy by harnessing high-energy radiation. Studies have demonstrated that PSM effectively kills solid tumors even in hypoxic conditions and significantly inhibits tumor growth. This innovative nanoplatform showcases high efficacy in multimodal synergistic tumor treatment, successfully integrating multiple therapeutic approaches to overcome the challenges posed by hypoxia.

Nucleic Acid Drugs in Radiotherapy

Radiotherapy remains a cornerstone of cancer treatment, using high-energy radiation to induce DNA damage in tumor cells, leading to cell death. However, its efficacy is often hindered by challenges such as radiation resistance and side effects. As a powerful class of functional molecules, nucleic acid drugs (NADs) present a promising solution to these limitations. Engineered to target key pathways like DNA repair and tumor hypoxia, NADs can enhance radiotherapy sensitivity. NADs can also serve as delivery vehicles for radiotherapy agents such as radionuclides, improving targeting accuracy and minimizing side effects. This review explores the role of NADs in optimizing radiotherapy, highlighting their mechanisms, clinical applications, and synergies with radiotherapy, ultimately offering a promising strategy for improving patient outcomes in cancer therapy.

Peptide-based PET/CT imaging visualizes PD-L1-driven radioresistance in glioblastoma

Radioresistance remains a great challenge for radiotherapy in the treatment of glioblastoma (GBM). PD-L1 expression is a key contributor to radioresistance and immune escape in GBM. The lack of effective methods to monitor the change of PD-L1 during radiotherapy in patients limits timely intervention and management of the resistance. Here, we developed a novel peptide tracer [18F]AlF-NOTA-PCP2 for PET/CT to visualize the changes of PD-L1 expression in response to radiotherapy, revealing PD-L1-driven radioresistance in GBM. The [18F]AlF-NOTA-PCP2 demonstrated high specificity and binding affinity to PD-L1 in vitro. The uptake of [18F]AlF-NOTA-PCP2 on PET/CT showed a strong positive correlation with PD-L1 expression by immunohistochemistry (IHC) (R² = 0.861, P < 0.001) in GBM xenograft tumors. The radiotracer uptake in PD-L1-positive tumors significantly increased post-radiotherapy (21.25 ± 0.91 % vs. 25.12 ± 0.82 %, P = 0.008), aligning with the radioresistance observed in these tumors. In vitro studies revealed that PD-L1-driven radioresistance by enhancing DNA damage repair through upregulation of RAD51 after activation of the PI3K-Akt pathway in cells. Preliminary clinical application in a radiotherapy-treated GBM patient demonstrated the ability to monitor PD-L1 dynamics, supporting its potential for clinical translation. Collectively, this peptide-based small molecule PET/CT radiotracers offer a noninvasive, real-time, and quantitative method to dynamically visualize PD-L1-driven radioresistance in GBM. It could serve as a potential radiotracer for facilitating patient stratification, adjusting radiotherapy regimens, and guiding personalized immunotherapy strategies.

Radionuclide treatments of cancer: molecular mechanisms, biological responses, histopathological changes, and role of PET imaging

Radiation treatments [radiotherapy and radionuclide treatments (RNTs)] are one of the main and effective treatment modalities of cancer. Globally, the number of cancer patients treated with radionuclides are much less as compared to number of radiotherapy cases but with the development of new radiotracers, most notably 177 Lu and 225 Ac-labeled prostate-specific membrane antigen ligands, and 223 Ra-dichloride for prostate cancer and 177 Lu-somatostatin analogs for neuroendocrine tumors, there is a significant rise in RNTs in the last decade. As therapeutic applications of nuclear medicine is on the rise, the aim of this review is to summarize biological responses to radiation treatments and molecular mechanisms of radiation-induced cell death (e.g. ionization, DNA damages such as double-strand breaks, DNA repair mechanisms, types of cell deaths such as apoptosis, necrosis, and immunogenic cell death), histopathological changes with radiation treatments, and role of PET imaging in RNTs as part of radionuclide theranostics for selecting and planning patients for RNTs, dosimetry, predicting and assessing response to RNTs, predicting toxicities, and other possible PET findings which may be seen after RNTs such as activation of immune system.

Live-cell imaging and analysis of 3D spheroids in hypoxia- and radiotherapy-related research

3D spheroids are a valuable tool for investigating the interplay between hypoxia and radioresistance. However, standardized methods for visualizing normoxic and hypoxic regions within spheroids and assessing treatment responses are lacking. We developed a straightforward workflow for the analysis of spheroids based on image processing using a novel custom-written script, and flow cytometry.

Radiation therapy-induced normal tissue damage: involvement of EMT pathways and role of FLASH-RT in reducing toxicities

Radiation therapy (RT) is fundamental to the fight against cancer because of its exceptional ability to target and destroy cancer cells. However, conventional radiation therapy can significantly affect the adjacent normal tissues, leading to fibrosis, inflammation, and decreased organ function. This tissue damage not only reduces the quality of life but also prevents the total elimination of cancer. The transformation of epithelial cells into mesenchymal-like cells, termed epithelial-mesenchymal transition (EMT), is essential for processes such as fibrosis, embryogenesis, and wound healing. Conventional radiation therapy increases the asymmetric activation of fibrotic and inflammatory pathways, and the resulting chronic fibrotic changes and organ dysfunction are linked to radiation-induced epithelial-mesenchymal transition. Recent advances in radiation therapy, namely flash radiation therapy (FLASH-RT), have the potential to widen the therapeutic index. Radiation delivered by FLASH-RT at very high dose rates (exceeding 40 Gy/s) can protect normal tissue from radiation-induced damage, a phenomenon referred to as the "FLASH effect". Preclinical studies have demonstrated that FLASH-RT successfully inhibits processes associated with fibrosis and epithelial-mesenchymal transition, mitigates damage to normal tissue, and enhances regeneration. Three distinct types of EMT have been identified: type-1, associated with embryogenesis; Type-2, associated with injury potential; and type-3, related with cancer spread. The regulation of EMT via pathways, including TGF-β/SMAD, WNT/β-catenin, and NF-κB, is essential for radiation-induced tissue remodelling. This study examined radiation-induced EMT, TGF-β activity, multiple signalling pathways in fibrosis, and the potential of FLASH-RT to reduce tissue damage. FLASH-RT is a novel approach to treat chronic tissue injury and fibrosis post-irradiation by maintaining epithelial properties and regulating mesenchymal markers including vimentin and N-cadherin. Understanding these pathways will facilitate the development of future therapies that can alleviate fibrosis, improve the efficacy of cancer therapy, and improve the quality of life of patients.

Radiotherapy can significantly improve survival outcomes in patients with muscle-invasive bladder cancer who are unsuitable for cystectomy or chemoradiotherapy

Radical cystectomy and bladder preservation therapy are effective for muscle-invasive bladder cancer (MIBC); however, many patients over 70 are medically unfit for these options. For such patients, radiotherapy serves as a viable alternative. This study compares survival outcomes of radiotherapy versus supportive care in MIBC patients ineligible for cystectomy or bladder preservation with concurrent chemoradiotherapy. Using the Taiwan Cancer Registry and National Health Insurance Research Database (2011-2020), we identified patients with cT2-T4N0-1M0 urinary bladder urothelial carcinoma. Patients were excluded if they had undergone cystectomy or chemotherapy. Patients received either radiotherapy or supportive care, with endpoints of overall survival (OS) and cancer-specific survival (CSS) analyzed by Kaplan-Meier and multivariate Cox regression. Among 485 MIBC patients, 301 (62%) received radiotherapy, and 184 (38%) supportive care. After 13.93 months of median follow-up, radiotherapy significantly improved OS and CSS (P<0.001). Mortality rates were 26.9% for radiotherapy and 76.1% for supportive care at one year, and 59.5% vs. 94.0% at three years. OS and CSS benefits were confirmed for stages II-IV (adjusted hazard ratios: 5.47, 3.23, and 12.44, respectively), with T3, T4, N1, and chronic obstructive pulmonary disease (COPD) predicting worse OS. In conclusion, radiotherapy offers superior survival benefits compared to supportive care in MIBC patients who are unfit for cystectomy or chemoradiotherapy. These findings provide valuable insights for clinicians in making treatment decisions, particularly for elderly or medically unfit patients with early or locally advanced-stage MIBC.

Bidirectional regulation of reactive oxygen species for radiosensitization in nasopharyngeal carcinoma

Radiotherapy (RT) is the primary treatment modality for nasopharyngeal carcinoma (NPC). However, the tumor microenvironment (TME)-induced radioresistance often compromises its therapeutic efficacy. Herein, we propose an innovative bidirectional radiosensitization strategy for NPC. Specifically, we have encapsulated metformin (Met) and copper sulfide nanoparticles (CuS NPs) within injectable DNA supramolecular hydrogels (DSH) to create a novel radiosensitizer, Met-CuS@DSH. This radiosensitizer not only effectively reverses tumor hypoxia to promote reactive oxygen species (ROS) generation but also significantly inhibits glutathione (GSH)-mediated ROS scavenging, thereby achieving bidirectional radiosensitization by enhancing ROS production and suppressing its scavenging. This strategy significantly improves the therapeutic effect of NPC while reducing the RT dose (3 Gy in total), which provides a promising approach for overcoming the radioresistance of NPC caused by TME.

Modulation of the local angiotensin II: Suppression of ferroptosis and radiosensitivity in nasopharyngeal carcinoma via the HIF-1α-HILPDA axis

PURPOSE

Radiotherapy presents a curative approach for nasopharyngeal carcinoma (NPC); however, the cellular radiosensitivity heterogeneity limits its efficacy. Thus, investigating the specific mechanisms of radioresistance in NPC is crucial for identifying and employing effective radiosensitizing agents to enhance treatment success.

METHODS AND MATERIALS

Radioresistant NPC cell lines HONE1-RR and SUNE1-RR were established. Quantitative reverse transcription-PCR (qRT-PCR), western blot, and enzyme-linked immuno sorbent assay (ELISA) were employed to detect the activation of the angiotensinogen (AGT) and local angiotensin II (Ang II). Transmission electron microscopy, ferrous ion detection, and lipid oxidation levels were utilized to detect radiation-induced ferroptosis in NPC. Bioinformatics analysis, along with qRT-PCR, western blotting, co-immunoprecipitation, and dual-luciferase assays were employed to explore downstream mechanisms. Colony formation assay, Cell Counting Kit-8 (CCK-8) assay, and a nude mouse xenograft model were utilized to assess NPC radiosensitivity. The expression of AGT, hypoxia-inducible factor-1 alpha (HIF-1α), hypoxia-inducible lipid droplet-associated protein (HILPDA), and glutathione peroxidase 4 (GPX4) in NPC tissues was detected through immunohistochemistry.

RESULTS

Activation of local Ang II was revealed to play a critical role in driving radioresistance in NPC cells modulating ferroptosis. This local Ang II established a positive feedback loop with HIF-1α through two parallel pathways; Ang II stabilizes HIF-1α by activating the MAPK pathway, and AGT directly binds HIF-1α to prevent its degradation. This AGT-HIF-1α loop regulated NPC cell ferroptosis via transcriptional regulation of HILPDA expression. Moreover, the co-administration of Ang II receptor antagonist (ARB) and ferroptosis inducers markedly increased NPC radiosensitivity.Additionally, the expression of AGT, HIF-1α, and HILPDA was closely correlated with the intensity of ferroptosis, radiosensitivity, and prognosis in NPC.

CONCLUSIONS

Our findings suggest that the AGT-HIF-1α-HILPDA pathway promotes radioresistance in NPC by enhancing lipid droplet accumulation, thereby suppressing ferroptosis. Targeting local Ang II alongside ferroptosis induction offers a promising strategy to improve radiosensitivity in NPC.

Nanoparticle-enabled In Situ drug potency activation for enhanced tumor-specific therapy

Cancer treatment faces significant challenges including inadequate tumor specificity, drug resistance, and severe side effects, often resulting in unsatisfactory patient outcomes. Nanomedicines offer a transformative platform for tumor-targeted drug delivery and antitumor potency activation, providing an indispensable strategy for overcoming the severe damage to normal tissues caused by the inherent "always-on" cytotoxicity of conventional therapeutic agents. This review focuses on the emerging concept of "nanoparticle-enabled in situ drug potency activation", where inactive or minimally toxic agents are selectively activated within tumors to enhance the therapeutic efficacy and minimize the adverse effects. We systematically analyzed literature from PubMed and Web of Science databases spanning the last two decades, emphasizing experimental evidence supporting this in situ drug potency activation concept. Key strategies including stimuli-responsive prodrug nanoparticles, metal-induced activation, and bioorthogonal reactions are critically evaluated for their potential to overcome limitations in current cancer therapies. The findings highlight the potential of in situ potency activation as a promising alternative to conventional therapeutics, with far-reaching implications for advancing effective and safe cancer treatments.

Engineered Cell Microenvironments: A Benchmark Tool for Radiobiology

The development of engineered cell microenvironments for fundamental cell mechanobiology, in vitro disease modeling, and tissue engineering applications increased exponentially during the last two decades. In such context, in vitro radiobiology is a field of research aiming at understanding the effects of ionizing radiation (e.g., X-rays/photons, high-speed electrons, and high-speed protons) on biological (cancerous) tissues and cells, in particular in terms of DNA damage leading to cell death. Herein, the perspective provides a comparative assessment overview of scaffold-free, scaffold-based, and organ-on-a-chip models for radiobiology, highlighting opportunities, limitations, and future pathways to improve the currently existing approaches toward personalized cancer medicine.

Iron-Based Nanomaterials for Modulating Tumor Microenvironment

Iron-based nanomaterials (IBNMs) have been widely applied in biomedicine applications including magnetic resonance imaging, targeted drug delivery, tumor therapy, and so forth, due to their unique magnetism, excellent biocompatibility, and diverse modalities. Further research on its enormous biomedical potential is still ongoing, and its new features are constantly being tapped and demonstrated. Among them, various types of IBNMs have demonstrated significant cancer therapy capabilities by regulating the tumor microenvironment (TME). In this review, a variety of IBNMs including iron oxide-based nanomaterials (IONMs), iron-based complex conjugates (ICCs), and iron-based single iron atom nanomaterials (ISANMs) will be introduced, and their advantages in regulating TME would also be emphasized. Besides, the recent progress of IBNMs for cancer diagnosis and treatment through the strategy of modulating TME will be summarized, including overcoming hypoxia, modulating acidity, decreasing redox species, and immunoregulation. Finally, the challenges and opportunities in this field are briefly discussed. This review is expected to contribute to the future design and development of next-generation TME-modulate IBNMs for cancer treatment.

Two-pronged strategy: A mitochondria targeting AIE photosensitizer for hydrogen sulfide detection and type I and type II photodynamic therapy

Multifunctional type-I photosensitizers (PSs) for hydrogen sulfide (H2S) detection and photodynamic therapy (PDT) of hypoxia tumors exhibits attractive curative effect but remains a challenging task. Herein, a mitochondria targeted aggregation-induced emission (AIE) photosensitizer TSPy-SS-P was designed and synthesized, which could be used for H2S detection and simultaneously type I and type II PDT. TSPy-SS-P had excellent selectivity and anti-interference abilities for endogenous and exogenous H2S detection in tumor cells. TSPy-SS-P was able to distinguish tumor cells with high level of H2S from normal cells by fluorescence "turn off" response to H2S. In addition, TSPy-SS-P showed type Ⅰ and type Ⅱ reactive oxygen species (ROS) generation ability to effectively ablate hypoxic tumor cells. TSPy-SS-P showed mitochondria targeting capacity which could produce ROS in situ to disrupt mitochondria and promote cell apoptosis. In vivo PDT experiments showcased that TSPy-SS-P had excellent tumor retention capability, effective tumor ablation ability and good biocompatibility. This work provided a two-pronged strategy to design organelles targeted photosensitizers for H2S detection and effective PDT of tumors.

Recent advances in reactive oxygen species (ROS)-responsive drug delivery systems for photodynamic therapy of cancer

Reactive oxygen species (ROS)-responsive drug delivery systems (DDSs) have garnered significant attention in cancer research because of their potential for precise spatiotemporal drug release tailored to high ROS levels within tumors. Despite the challenges posed by ROS distribution heterogeneity and endogenous supply constraints, this review highlights the strategic alliance of ROS-responsive DDSs with photodynamic therapy (PDT), enabling selective drug delivery and leveraging PDT-induced ROS for enhanced therapeutic efficacy. This review delves into the biological importance of ROS in cancer progression and treatment. We elucidate in detail the operational mechanisms of ROS-responsive linkers, including thioether, thioketal, selenide, diselencide, telluride and aryl boronic acids/esters, as well as the latest developments in ROS-responsive nanomedicines that integrate with PDT strategies. These insights are intended to inspire the design of innovative ROS-responsive nanocarriers for enhanced cancer PDT.

AQ4N nanocomposites for hypoxia-associated tumor combination therapy

Hypoxia in solid tumors increases their invasiveness and resistance to therapy, presenting a formidable obstacle in tumor therapy. The hypoxia prodrug banoxantrone (AQ4N) undergoes conversion into its topoisomerase II inhibitor form AQ4 under hypoxic conditions, which inhibits tumor cells while leaving normal cells unharmed. Numerous studies have found that AQ4N significantly enhances the tumor effect while minimizing toxicity to normal tissues when combined with other drugs or therapeutic approaches. Thus, to maximize AQ4N's effectiveness, co-delivery of AQ4N with other therapeutic agents to the tumor site is paramount, leading to the development of multifunctional multicomponent AQ4N nanocomposites thereby emerging as promising candidates for combination therapy in tumor treatment. However, currently there is a lack of systematic analysis and reviews focusing on AQ4N. Herein, this review provides a comprehensive retrospect and analysis of the recent advancements in AQ4N nanocomposites. Specifically, we discuss the synergistic effects observed when AQ4N is combined with chemotherapeutic drugs, radiotherapy, phototherapy, starvation, sonodynamic therapy and immunotherapy in preclinical models. Moreover, the advantages, limitations, and future perspectives of different AQ4N nanocomposites are highlighted, providing researchers from diverse fields with novel insights into tumor treatment.

A novel high-risk model identified by epithelial-mesenchymal transition predicts prognosis and radioresistance in rectal cancer

Many studies have shown that tumor cells that survive radiotherapy are more likely to metastasize, but the underlying mechanism remains unclear. Here we aimed to identify epithelial-mesenchymal transition (EMT)-related key genes, which associated with prognosis and radiosensitivity in rectal cancer. First, we obtained differentially expressed genes by analyzing the RNA expression profiles of rectal cancer retrieved from The Cancer Genome Atlas database, EMT-related genes, and radiotherapy-related databases, respectively. Then, Lasso and Cox regression analyses were used to establish an EMT-related prognosis model (EMTPM) based on the identified independent protective factor Fibulin5 (FBLN5) and independent risk gene EHMT2. The high-EMTPM group exhibited significantly poorer prognosis. Then, we evaluated the signature in an external clinical validation cohort. Through in vivo experiments, we further demonstrated that EMTPM effectively distinguishes radioresistant from radiosensitive patients with rectal cancer. Moreover, individuals in the high-EMTPM group showed increased expression of immune checkpoints compared to their counterparts. Finally, pan-cancer analysis of the EMTPM model also indicated its potential for predicting the prognosis of lung squamous cell carcinoma and breast cancer patients undergoing radiotherapy. In summary, we established a novel predictive model for rectal cancer prognosis and radioresistance based on FBLN5 and EHMT2 expressions, and suggested that immune microenvironment may be involved in the process of radioresistance. This predictive model could be used to select management strategies for rectal cancer.

The oxygen puzzle in FLASH radiotherapy: A comprehensive review and experimental outlook

FLASH radiotherapy is attracting increasing interest because it maintains tumor control while inflicting less damage to normal tissues compared to conventional radiotherapy. This sparing effect, the so-called FLASH effect, is achieved when radiation is delivered at ultra-high dose rates (≥40 Gy/s). Although the FLASH effect has already been demonstrated in several preclinical models, a complete mechanistic description explaining why tumors and normal tissues respond differently is still missing. None of the current hypotheses fully explains the experimental evidence. A common point between many of these is the role of oxygen, which is described as a major factor, either through transient hypoxia in the form of dissolved molecules, or reactive oxygen species (ROS). Therefore, this review focuses on both forms of this molecule, retracing old and more recent theories, while proposing new mechanisms that could provide a complete description of the FLASH effect based on preclinical and experimental evidence. In addition, this manuscript describes a set of experiments designed to provide the FLASH community with new tools for exploring the post-irradiation fate of ROS and their potential biological implications.

"Reductive stress" the overlooked side of cellular redox modulation in cancer: opportunity for design of next generation redox chemotherapeutics

The last three decades of redox biology research have been dominated by the term "oxidative stress" since it was first coined by Helmut Sies to represent a form of cellular redox modulation characterized by redox imbalance toward overproduction of oxidants. Almost every pathological condition, including cancer, has been linked with oxidative stress and so forth; targeting oxidative stress became the strategy for the new drug discovery with anticancer drugs aiming to selectively induce oxidative stress in cancerous cells while antioxidants aiming to prevent carcinogenesis as prophylactic agents. Time has now come to realize, how harmful the other side of the cellular redox spectrum, "reductive stress," characterized by redox imbalance toward the accumulation of reducing equivalents, maybe during carcinogenesis, and to tap its potential for the design of next-generation chemotherapeutic agents. Adjuvants-causing reductive stress may also work synergistically with radiation therapy under hypoxia to achieve better tumor control. Keeping this evolving field into account, the present review provides a current understating of the role of reductive stress in carcinogenesis, the status of reductive stress-based chemotherapeutic agents with particular emphasis on sulfhydryl and selenium-containing compounds and the gap areas that need to be addressed in future.

Ultraviolet (UV) radiation: a double-edged sword in cancer development and therapy

It has long been widely acknowledged that ultraviolet (UV) light is an environment risk factor that can lead to cancer, particularly skin cancer. However, it is worth noting that UV radiation holds potential for cancer treatment as a relatively high-energy electromagnetic wave. With the help of nanomaterials, the role of UV radiation has caught increasing attention in cancer treatment. In this review, we briefly summarized types of UV-induced cancers, including malignant melanoma, squamous cell carcinoma, basal cell carcinoma, Merkel cell carcinoma. Importantly, we discussed the primary mechanisms underlying UV carcinogenesis, including mutations by DNA damage, immunosuppression, inflammation and epigenetic alterations. Historically limited by its shallow penetration depth, the introduction of nanomaterials has dramatically transformed the utilization of UV light in cancer treatment. The direct effect of UV light itself generally leads to the suppression of cancer cell growth and the initiation of apoptosis and ferroptosis. It can also be utilized to activate photosensitizers for reactive oxygen species (ROS) production, sensitize radiotherapy and achieve controlled drug release. Finally, we comprehensively weigh the significant risks and limitations associated with the therapeutic use of UV radiation. And the contradictory effect of UV exposure in promoting and inhibiting tumor has been discussed. This review provides clues for potential clinical therapy as well as future study directions in the UV radiation field. The precise delivery and control of UV light or nanomaterials and the wavelength as well as dose effects of UV light are needed for a thorough understanding of UV radiation.

Three-Dimensional-Bioprinted Non-Small Cell Lung Cancer Models in a Mouse Phantom for Radiotherapy Research

Lung cancer continues to have one of the highest morbidity and mortality rates of any cancer. Although radiochemotherapy, in combination with immunotherapy, has significantly improved overall survival, new treatment options are urgently needed. However, preclinical radiotherapy testing is often performed in animal models, which has several drawbacks, including species-specific differences and ethical concerns. To replace animal models, this study used a micro-extrusion bioprinting approach to generate a three-dimensional (3D) human lung cancer model consisting of lung tumor cells embedded in human primary lung fibroblasts for radiotherapy research. The models were placed in a mouse phantom, i.e., a 3D-printed mouse model made of materials that mimic the X-ray radiation attenuation rates found in mice. In radiotherapy experiments, the model demonstrated a selective cytotoxic effect of X-rays on tumor cells, consistent with findings in 2D cells. Furthermore, the analysis of metabolic activity, cell death, apoptosis, and DNA damage-induced γH2AX foci formation revealed different results in the 3D model inside the phantom compared to those observed in irradiated models without phantom and 2D cells. The proposed setup of the bioprinted 3D lung model inside the mouse phantom provides a physiologically relevant model system to study radiation effects.

Monte Carlo investigation of the nucleus size effect and cell's oxygen content on the damage efficiency of protons

Living tissues could suffer different types of DNA damage as a result of being exposed to ionizing radiations. Monte Carlo simulations of the underlying interactions have been instrumental in predicting the damage types and the processes involved. In this work, we employed Geant4-DNA and MCDS for extracting the initial DNA damage and investigating the dependence of damage efficiency on the cell's oxygen content. The frequency-mean lineal (y¯F) and specific (z¯F) energies were derived for a spherical volume of water of various diameters between 2 and 11.1 μm. This sphere would serve as the nucleus of a cell of 100 μm diameter, engulfed by a homogeneous beam of protons. These microdosimetric quantities were calculated assuming spherical samples of 1 μm diameter in MCDS. The simulation results showed that for 230 MeV protons, an increase in the oxygen content from 0 by 10% raised the frequency of single- and double-strand breaks and lowered the base damage frequency. The resulting damage frequencies appeared to be independent of nucleus diameter. For proton energies between 2 and 230 MeV,y¯Fshowed no dependence on the cell diameter and an increase of the cell size resulted in a decrease inz¯F.An increase in the proton energy slowed down the decreasing rate ofz¯Fas a function of nucleus diameter. However, the ratio ofy¯Fvalues corresponding to two proton energies of choice showed no dependence on the nucleus size and were equal to the ratio of the correspondingz¯Fvalues. Furthermore, the oxygen content of the cell did not affect these microdosimetric quantities. Contrary to damage frequencies, these quantities appeared to depend only on direct interactions due to deposited energies. Our calculations showed the near independence of DNA damages on the nucleus size of the human cells. The probabilities of different types of single and double-strand breaks increase with the oxygen content.

Remote Control of Energy Transformation-Based Cancer Imaging and Therapy

Cancer treatment requires precise tumor-specific targeting at specific sites that allows for high-resolution diagnostic imaging and long-term patient-tailorable cancer therapy; while, minimizing side effects largely arising from non-targetability. This can be realized by harnessing exogenous remote stimuli, such as tissue-penetrative ultrasound, magnetic field, light, and radiation, that enable local activation for cancer imaging and therapy in deep tumors. A myriad of nanomedicines can be efficiently activated when the energy of such remote stimuli can be transformed into another type of energy. This review discusses the remote control of energy transformation for targetable, efficient, and long-term cancer imaging and therapy. Such ultrasonic, magnetic, photonic, radiative, and radioactive energy can be transformed into mechanical, thermal, chemical, and radiative energy to enable a variety of cancer imaging and treatment modalities. The current review article describes multimodal energy transformation where a serial cascade or multiple types of energy transformation occur. This review includes not only mechanical, chemical, hyperthermia, and radiation therapy but also emerging thermoelectric, pyroelectric, and piezoelectric therapies for cancer treatment. It also illustrates ultrasound, magnetic resonance, fluorescence, computed tomography, photoluminescence, and photoacoustic imaging-guided cancer therapies. It highlights afterglow imaging that can eliminate autofluorescence for sustained signal emission after the excitation.

CircRNA_101491 regulated the radiation sensitivity of esophageal squamous cell carcinomas via sponging miR-125a-5p

BACKGROUND

At present, it has been found that many patients have acquired resistance to radiotherapy, which greatly reduces the effect of radiotherapy and further affects the prognosis. CircRNAs is involved in the regulation of radiosensitivity of many kinds of tumor cells. Therefore, the main purpose of this study is to explore the regulatory effect of CircRNA_101491 on radiosensitivity of ESCC and its related mechanism.

METHODS

We established ESCC radiation-resistant cell line (KYSE150R cell) by gradient dose method, and tested the difference of KYSE150 between KYSE150R cell and parent cell in vitro. Then, after knocking down the expression of CircRNA_101491, a series of in vitro experiments were conducted to verify the effects of CircRNA_101491 on the phenotype and radiosensitivity of KYSE150R cells, and further analyzed the related regulatory mechanism. In addition, we also used the model of transplanted tumor in nude mice to investigate the effect of CircRNA_101491 on the radiosensitivity of ESCC in vivo.

RESULTS

According to a series of in vitro experiments, we confirmed that KYSE150R cells lost the epithelial phenotype and obtained interstitial cell-like phenotype, and found that CircRNA_101491 was highly expressed in KYSE150R cells. In addition, we found that knocking down the expression of CircRNA_101491 will lift the inhibition of miR-125a-5p, and then reverse the process of EMT, accelerate the process of apoptosis, thus play a role in radiosensitization. The in vivo experiment of transplanted tumor in nude mice also showed that knocking down the expression of CircRNA_101491 could enhance the radiosensitivity of ESCC.

CONCLUSION

In conclusion, we confirmed that interfering with the expression of CircRNA_101491 can relieve the inhibition of miR-125a-5p, thus reverse the process of interstitial phenotype, accelerate the process of apoptosis, and enhance the radiosensitivity of ESCC.

The role of HOTAIR in the modulation of resistance to anticancer therapy

Leading anti-tumour therapeutic strategies typically involve surgery and radiotherapy for locally advanced (non-metastatic) cancers, while hormone therapy, chemotherapy, and molecular targeted therapy are the current treatment options for metastatic cancer. Despite the initially high sensitivity rate to anticancer therapies, a large number of patients develop resistance, leading to a poor prognosis. The mechanisms related to drug resistance are highly complex, and long non-coding RNAs appear to play a crucial role in these processes. Among these, the lncRNA homeobox transcript antisense intergenic RNA (HOTAIR), widely implicated in cancer initiation and progression, likewise plays a significant role in anticancer drug resistance. It can modulate cell activities such as proliferation, apoptosis, hypoxia, autophagy, as well as epithelial-mesenchymal transition, thereby contributing to the development of resistant tumour cells. In this manuscript, we describe different mechanisms of antitumor drug resistance in which HOTAIR is involved and suggest its potential as a therapeutic predictive biomarker for the management of cancer patients.