Role of metabolism in cancer cell radioresistance and radiosensitization methods

Radiotheranostics in oncology: current challenges and emerging opportunities

Structural imaging remains an essential component of diagnosis, staging and response assessment in patients with cancer; however, as clinicians increasingly seek to noninvasively investigate tumour phenotypes and evaluate functional and molecular responses to therapy, theranostics - the combination of diagnostic imaging with targeted therapy - is becoming more widely implemented. The field of radiotheranostics, which is the focus of this Review, combines molecular imaging (primarily PET and SPECT) with targeted radionuclide therapy, which involves the use of small molecules, peptides and/or antibodies as carriers for therapeutic radionuclides, typically those emitting α-, β- or auger-radiation. The exponential, global expansion of radiotheranostics in oncology stems from its potential to target and eliminate tumour cells with minimal adverse effects, owing to a mechanism of action that differs distinctly from that of most other systemic therapies. Currently, an enormous opportunity exists to expand the number of patients who can benefit from this technology, to address the urgent needs of many thousands of patients across the world. In this Review, we describe the clinical experience with established radiotheranostics as well as novel areas of research and various barriers to progress.

Human lung-cancer-cell radioresistance investigated through 2D network topology

Radiation therapy (RT) is now considered to be a main component of cancer therapy, alongside surgery, chemotherapy and monoclonal antibody-based immunotherapy. In RT, cancer tissues are exposed to ionizing radiation causing the death of malignant cells and favoring cancer regression. However, the efficiency of RT may be hampered by cell-radioresistance (RR)—that is a feature of tumor cells of withstanding RT. To improve the RT performance, it is decisive developing methods that can help to quantify cell sensitivity to radiation. In acknowledgment of the fact that none of the existing methods to assess RR are based on cell graphs topology, in this work we have examined how 2D cell networks, within a single colony, from different human lung cancer lines (H460, A549 and Calu-1) behave in response to doses of ionizing radiation ranging from 0 to 8 Gy. We measured the structure of resulting cell-graphs using well-assessed networks-analysis metrics, such as the clustering coefficient (cc), the characteristic path length (cpl), and the small world coefficient (SW). Findings of the work illustrate that the clustering characteristics of cell-networks show a marked sensitivity to the dose and cell line. Higher-than-one values of SW coefficient, clue of a discontinuous and inhomogeneous cell spatial layout, are associated to elevated levels of radiation and to a lower radio-resistance of the treated cell line. Results of the work suggest that topology could be used as a quantitative parameter to assess the cell radio-resistance and measure the performance of cancer radiotherapy.

Carbon Ion Radiotherapy Induce Metabolic Inhibition After Functional Imaging-Guided Simultaneous Integrated Boost for Prostate Cancer

Purpose

As local recurrence remains a challenge and the advantages of the simultaneous integrated boost (SIB) technique have been validated in photon radiotherapy, we applied the SIB technique to CIRT. The aim was to investigate the metabolomic changes of the CIRT with concurrent androgen deprivation therapy (ADT) in localized prostate cancer (PCa) and the unique metabolic effect of the SIB technique.

Material and Methods

This study enrolled 24 pathologically confirmed PCa patients. All patients went through CIRT with concurrent ADT. The gross target volume (GTV) boost was defined as positive lesions on both 68Ga-PSMA PET/CT and mpMRI images. Urine samples collected before and after CIRT were analyzed by the Q-TOF UPLC-MS/MS system. R platform and MetDNA were used for peak detection and identification. Statistical analysis and metabolic pathway analysis were performed on Metaboanalyst.

Results

The metabolite profiles were significantly altered after CIRT. The most significantly altered metabolic pathway is PSMA participated alanine, aspartate and glutamate metabolism. Metabolites in this pathway showed a trend to be better suppressed in the SIB group. A total of 11 identified metabolites were significantly discriminative between two groups and all of them were better down-regulated in the SIB group. Meanwhile, among these metabolites, three metabolites in DNA damage and repair related purine metabolism were down-regulated to a greater extent in the SIB group.

Conclusion

Metabolic dysfunction was one of the typical characteristics of PCa. CIRT with ADT showed a powerful inhibition of PCa metabolism, especially in PSMA participated metabolic pathway. The SIB CIRT showed even better performance on down-regulation of most metabolism than uniform-dose-distribution CIRT. Meanwhile, the SIB CIRT also showed its unique superiority to inhibit purine metabolism. PSMA PET/CT guided SIB CIRT showed its potentials to further benefit PCa patients.

Construction of a lncRNA–mRNA Co-Expression Network for Nasopharyngeal Carcinoma

Long non-coding RNAs (lncRNAs) widely regulate gene expression and play important roles in the pathogenesis of human diseases, including malignant tumors. However, the functions of most lncRNAs remain to be elucidated. In order to study and screen novel lncRNAs with important functions in the carcinogenesis of nasopharyngeal carcinoma (NPC), we constructed a lncRNA expression profile of 10 NPC tissues and 6 controls through a gene microarray. We identified 1,276 lncRNAs, of which most are unknown, with different expression levels in the healthy and NPC tissues. In order to shed light on the functions of these unknown lncRNAs, we first constructed a co-expression network of lncRNAs and mRNAs using bioinformatics and systematic biological approach. Moreover, mRNAs were clustered and enriched by their biological functions, and those lncRNAs have similar expression trends with mRNAs were defined as functional molecules with potential biological significance. The module may help identify key lncRNAs in the carcinogenesis of NPC and provide clues for in-depth study of their functions and associated signaling pathways. We suggest the newly identified lncRNAs may have clinic value as biomarkers and therapeutic targets for NPC diagnosis and treatment.

Exploring the impact of metabolic imaging in head and neck cancer treatment

Background

Target volume delineation is performed with anatomical imaging for head and neck cancer. Molecular imaging allows the recognition of specific tumor regions. Its inclusion in the pathway could lead to changes in delineation and resultant treatment plans.

Methods

PRISMA methodology was adhered to when selecting the articles for analysis and only full articles were quality assessed.

Results

Seventeen articles were included. Gross tumor volume (GTV) primary, GTV nodal, and other target volumes were evaluated. Positron emission tomography/computerized tomography (PET/CT) produced smaller primary GTVs, although not with diffusion‐weighted imaging‐magnetic resonance imaging (DWI‐MRI) or PET/MRI. The impact of these image modalities on GTV nodal did not display any consistency. Additionally, there was considerable heterogeneity in metrics comparing delineations. Four studies included appraised the dosimetric impact of the changes in target volume delineation.

Conclusion

Quantifying the impact of molecular imaging is difficult, due to heterogeneity in reporting metrics in molecular imaging modalities and a paucity of detail regarding delineation method and guideline adherence.

Assessment of lipid peroxidation in irradiated cells

Lipid peroxidation occurs under conditions where reactive oxygen species (ROS) readily react with vulnerable lipids on cell membranes. Polyunsaturated fatty acids (PUFAs) are highly susceptible to lipid peroxidation because of their unstable double bonds. Because the cell membrane is particularly rich in PUFAs, it is often the site at which many lipid peroxidation chain reactions occur. Lipid peroxidation is considered the ultimate trigger of ferroptosis, an iron-dependent form of non-apoptotic cell death. Radiotherapy is a common cancer treatment that uses high-energy ionizing radiation to kill cancer cells, and radiation-induced cell death is partially attributed to lipid peroxidation-driven ferroptosis. Here, we describe methods to assess lipid peroxidation in irradiated cells. The same techniques can be applied to a variety of lipid peroxidation measurements under different treatment conditions.

Regulatory pathways and drugs associated with ferroptosis in tumors

Ferroptosis is a type of cell death that depends on iron and reactive oxygen species (ROS). The accumulation of iron and lipid peroxidation primarily initiates oxidative membrane damage during ferroptosis. The core molecular mechanism of ferroptosis includes the regulation of oxidation and the balance between damage and antioxidant defense. Tumor cells usually contain a large amount of H₂O₂, and ferrous/iron ions will react with excessive H₂O₂ in cells to produce hydroxyl radicals and induce ferroptosis in tumor cells. Here, we reviewed the latest studies on the regulation of ferroptosis in tumor cells and introduced the tumor-related signaling pathways of ferroptosis. We paid particular attention to the role of noncoding RNA, nanomaterials, the role of drugs, and targeted treatment using ferroptosis drugs for mediating the ferroptosis process in tumor cells. Finally, we discussed the currently unresolved problems and future research directions for ferroptosis in tumor cells and the prospects of this emerging field. Therefore, we have attempted to provide a reference for further understanding of the pathogenesis of ferroptosis and proposed new targets for cancer treatment.

Norcantharidin promotes cancer radiosensitization through Cullin1 neddylation-mediated CDC6 protein degradation

Radiotherapy (RT) is a conventional cancer therapeutic modality. However, cancer cells tend to develop radioresistance after a period of treatment. Diagnostic markers and therapeutic targets for radiosensitivity are severely lacking. Our recently published studies demonstrated that the cell division cycle (CDC6) is a critical molecule contributing to radioresistance, and maybe a potential therapeutic target to overcome radioresistance. In the present study, we for the first time reported that Norcantharidin (NCTD), a demethylated form of cantharidin, re-sensitized radioresistant cancer cells to overcome radioresistance, and synergistically promoted irradiation (IR)-induced cell killing and apoptosis by inducing CDC6 protein degradation. Mechanistically, NCTD induced CDC6 protein degradation through the ubiquitin-proteasome pathways. By using small interfering RNA (siRNA) interference or small compound inhibitors, we further determined that NCTD induced CDC6 protein degradation through a neddylation-dependent pathway, but not through Huwe1, Cyclin F, and APC/C-mediated ubiquitin-proteasome pathways. We screened the six most relevant Cullin subunits (CUL1, 2, 3, 4A, 4B, and 5) using siRNAs. The knockdown of Cullin1 but not the other five cullins remarkably elevated CDC6 protein levels. NCTD promoted the binding of Cullin1 to CDC6, thereby promoting CDC6 protein degradation through a Cullin1 neddylation-mediated ubiquitin-proteasome pathway. NCTD can be used in combination with radiotherapy to achieve better anticancer efficacy, or work as a radiosensitizer to overcome cancer radioresistance.

Integrating mechanism-based modeling with biomedical imaging to build practical digital twins for clinical oncology

Digital twins employ mathematical and computational models to virtually represent a physical object (e.g., planes and human organs), predict the behavior of the object, and enable decision-making to optimize the future behavior of the object. While digital twins have been widely used in engineering for decades, their applications to oncology are only just emerging. Due to advances in experimental techniques quantitatively characterizing cancer, as well as advances in the mathematical and computational sciences, the notion of building and applying digital twins to understand tumor dynamics and personalize the care of cancer patients has been increasingly appreciated. In this review, we present the opportunities and challenges of applying digital twins in clinical oncology, with a particular focus on integrating medical imaging with mechanism-based, tissue-scale mathematical modeling. Specifically, we first introduce the general digital twin framework and then illustrate existing applications of image-guided digital twins in healthcare. Next, we detail both the imaging and modeling techniques that provide practical opportunities to build patient-specific digital twins for oncology. We then describe the current challenges and limitations in developing image-guided, mechanism-based digital twins for oncology along with potential solutions. We conclude by outlining five fundamental questions that can serve as a roadmap when designing and building a practical digital twin for oncology and attempt to provide answers for a specific application to brain cancer. We hope that this contribution provides motivation for the imaging science, oncology, and computational communities to develop practical digital twin technologies to improve the care of patients battling cancer.

Multifunctional nanocomposites DDMplusAF inhibit the proliferation and enhance the radiotherapy of breast cancer cells via modulating tumor-promoting factors and metabolic reprogramming

Background

Tumor-promoting factors (TPF) and metabolic reprogramming are hallmarks of cancer cell growth. This study is designed to combine the newly synthesized two nanocomposites DDM (HA-FA-2DG@DCA@MgO) and AF (HA-FA-Amygdaline@Fe2O3) with fractionated doses of radiotherapy (6 Gy-FDR; fractionated dose radiotherapy) to improve the efficiency of chemo-radiotherapy against breast cancer cell lines (BCCs; MCF-7 and MDA-MB-231). The physicochemical properties of each nanocomposite were confirmed using energy dispersive XRD, FTIR, HR-TEM, and SEM. The stability of DDMPlusAF was also examined, as well as its release and selective cellular uptake in response to acidic pH. A multiple-MTT assay was performed to evaluate the radiosensitivity of BCCs to DDMPlusAF at 3 Gy (single dose radiotherapy; SDR) and 6 Gy-FDR after 24, 48, and 72 h. Finally, the anti-cancer activity of DDMPlusAF with 6 Gy-FDR was investigated via assessing the cell cycle distribution and cell apoptosis by flow cytometry, the biochemical mediators (HIF-1α, TNF-α, IL-10, P53, PPAR-α, and PRMT-1), along with glycolytic pathway (glucose, HK, PDH, lactate, and ATP) as well as the signaling effectors (protein expression of AKT, AMPK, SIRT-1, TGF-β, PGC-1α, and gene expression of ERR-α) were determined in this study.

Results

The stability of DDMPlusAF was verified over 6 days without nanoparticle aggregation. DDMPlusAF release and selectivity data revealed that their release was amenable to the acidic pH of the cancer environment, and their selectivity was enhanced towards BCCs owing to CD44 and FR-α receptors-mediated uptake. After 24 h, DDMPlusAF boosted the BCC radiosensitivity to 6 Gy-FDR. Cell cycle arrest (G2/M and pre-G1), apoptosis induction, modulation of TPF mediators and signaling effectors, and suppression of aerobic glycolysis, all confirmed DDMPlusAF + 6 Gy’s anti-cancer activity.

Conclusions

It could be concluded that DDMPlusAF exerted a selective cancer radiosensitizing efficacy with targeted properties for TPF and metabolic reprogramming in BCCs therapy.

The Role of LncRNAs in the Regulation of Radiotherapy Sensitivity in Cervical Cancer

Cervical cancer (CC) is one of the three majors gynecological malignancies, which seriously threatens women’s health and life. Radiotherapy (RT) is one of the most common treatments for cervical cancer, which can reduce local recurrence and prolong survival in patients with cervical cancer. However, the resistance of cancer cells to Radiotherapy are the main cause of treatment failure in patients with cervical cancer. Long non-coding RNAs (LncRNAs) are a group of non-protein-coding RNAs with a length of more than 200 nucleotides, which play an important role in regulating the biological behavior of cervical cancer. Recent studies have shown that LncRNAs play a key role in regulating the sensitivity of radiotherapy for cervical cancer. In this review, we summarize the structure and function of LncRNAs and the molecular mechanism of radiosensitivity in cervical cancer, list the LncRNAs associated with radiosensitivity in cervical cancer, analyze their potential mechanisms, and discuss the potential clinical application of these LncRNAs in regulating radiosensitivity in cervical cancer.

Ultrafast Fabrication of Iron/Manganese Co-Doped Bismuth Trimetallic Nanoparticles: A Thermally Aided Chemodynamic/Radio-Nanoplatform for Low-Dose Radioresistance

Low-dose radioresistance continues to be one of the major limitations for clinical curative treatment of cancer. Luckily, nanotechnology mediated by multifunctional nanomaterials provides potential opportunity to relieve the radioresistance via increasing the radiosensitivity of cancer cells. Herein, an ultrafast fabrication strategy is reported to prepare iron/manganese co-doped bismuth trimetallic nanoparticles (pFMBi NPs) as a multifunctional radiosensitizer for combined therapy. The bismuth matrix provides the intrinsic radiosensitization effect under the low and safe radiation dose via Auger electrons, photoelectrons, and Rayleigh scattering. Meanwhile, co-doping of iron and manganese ions endows pFMBi NPs with both the Fenton reaction property for reactive oxygen species (ROS) generation and photothermal conversion performance for heat production. Additional ROS generation enhances the radiosensitization effect by collaborating with Rayleigh scattering-mediated water radiolysis, and endogenous heat production under near-infrared 808 nm laser irradiation makes DNA more sensitive to radiation and ROS damage. Both in vitro and in vivo evaluations demonstrate the effective antitumor and radiosensitization effects via thermally aided chemodynamic/radiotreatment with a low radiation dose (6 Gy). Therefore, this work provides a potential strategy for overcoming the low-dose radioresistance in cancer therapy.

Reactive oxygen species-inducing titanium peroxide nanoparticles as promising radiosensitizers for eliminating pancreatic cancer stem cells

BACKGROUND

Despite recent advances in radiotherapy, radioresistance in patients with pancreatic cancer remains a crucial dilemma for clinical treatment. Cancer stem cells (CSCs) represent a major factor in radioresistance. Developing a potent radiosensitizer may be a novel candidate for the eradication of pancreatic CSCs.

METHODS

CSCs were isolated from MIA PaCa-2 and PANC1 human pancreatic cancer cell lines. Titanium peroxide nanoparticles (TiOxNPs) were synthesized from titanium dioxide nanoparticles (TiO2NPs) and utilized as radiosensitizers when added one hour prior to radiation exposure. The antitumor activity of this novel therapeutic strategy was evaluated against well-established pancreatic CSCs model both in vitro and in vivo.

RESULTS

It is shown that TiOxNPs combined with ionizing radiation exhibit anti-cancer effects on radioresistant CSCs both in vitro and in vivo. TiOxNPs exhibited a synergistic effect with radiation on pancreatic CSC-enriched spheres by downregulating self-renewal regulatory factors and CSC surface markers. Moreover, combined treatment suppressed epithelial-mesenchymal transition, migration, and invasion properties in primary and aggressive pancreatic cancer cells by reducing the expression of proteins relevant to these processes. Notably, radiosensitizing TiOxNPs suppressed the growth of pancreatic xenografts following primary or dissociating sphere MIA PaCa-2 cell implantation. It is inferred that synergy is formed by generating intolerable levels of reactive oxygen species (ROS) and inactivating the AKT signaling pathway.

CONCLUSIONS

Our data suggested the use of TiOxNPs in combination with radiation may be considered an attractive therapeutic strategy to eliminate pancreatic CSCs.

Stratification of radiosensitive brain metastases based on an actionable S100A9/RAGE resistance mechanism

Whole-brain radiotherapy (WBRT) is the treatment backbone for many patients with brain metastasis; however, its efficacy in preventing disease progression and the associated toxicity have questioned the clinical impact of this approach and emphasized the need for alternative treatments. Given the limited therapeutic options available for these patients and the poor understanding of the molecular mechanisms underlying the resistance of metastatic lesions to WBRT, we sought to uncover actionable targets and biomarkers that could help to refine patient selection. Through an unbiased analysis of experimental in vivo models of brain metastasis resistant to WBRT, we identified activation of the S100A9–RAGE–NF-κB–JunB pathway in brain metastases as a potential mediator of resistance in this organ. Targeting this pathway genetically or pharmacologically was sufficient to revert the WBRT resistance and increase therapeutic benefits in vivo at lower doses of radiation. In patients with primary melanoma, lung or breast adenocarcinoma developing brain metastasis, endogenous S100A9 levels in brain lesions correlated with clinical response to WBRT and underscored the potential of S100A9 levels in the blood as a noninvasive biomarker. Collectively, we provide a molecular framework to personalize WBRT and improve its efficacy through combination with a radiosensitizer that balances therapeutic benefit and toxicity.

Group and Basis Restricted Non-Negative Matrix Factorization and Random Forest for Molecular Histotype Classification and Raman Biomarker Monitoring in Breast Cancer

Raman spectroscopy is a non-invasive optical technique that can be used to investigate biochemical information embedded in cells and tissues exposed to ionizing radiation used in cancer therapy. Raman spectroscopy could potentially be incorporated in personalized radiation treatment design as a tool to monitor radiation response in at the metabolic level. However, tracking biochemical dynamics remains challenging for Raman spectroscopy. Here we developed a novel analytical framework by combining group and basis restricted non-negative matrix factorization and random forest (GBR-NMF-RF). This framework can monitor radiation response profiles in different molecular histotypes and biochemical dynamics in irradiated breast cancer cells. Five subtypes of; human breast cancer (MCF-7, BT-474, MDA-MB-230, and SK-BR-3) and normal cells derived from human breast tissue (MCF10A) which had been exposed to ionizing radiation were tested in this framework. Reference Raman spectra of 20 biochemicals were collected and used as the constrained Raman biomarkers in the GBR-NMF-RF framework. We obtained scores for individual biochemicals corresponding to the contribution of each Raman reference spectrum to each spectrum obtained from the five cell types. A random forest classifier was then fitted to the chemical scores for performing molecular histotype classifications (HER2, PR, ER, Ki67, and cancer versus non-cancer) and assessing the importance of the Raman biochemical basis spectra for each classification test. Overall, the GBR-NMF-RF framework yields classification results with high accuracy (>97%), high sensitivity (>97%), and high specificity (>97%). Variable importance calculated in the random forest model indicated high contributions from glycogen and lipids (cholesterol, phosphatidylserine, and stearic acid) in molecular histotype classifications.

Dietary Phytochemicals Targeting Nrf2 to Enhance the Radiosensitivity of Cancer

Nowadays, cancer has become the second leading cause of death worldwide. Radiotherapy (RT) is the mainstay in management of carcinoma; however, overcoming radioresistance remains a great challenge to successfully treat cancer. Nrf2 is a key transcription factor that is responsible for maintaining cellular redox homeostasis. Activation of Nrf2 signaling pathway could upregulate multifarious antioxidant and detoxifying enzymes, further scavenging excessive reactive oxygen species (ROS). Despite its cytoprotective roles in normal cells, it could also alleviate oxidative stress and DNA damage caused by RT in cancer cells, thus promoting cancer cell survival. Accumulating evidence indicates that overactivation of Nrf2 is associated with radioresistance; therefore, targeting Nrf2 is a promising strategy to enhance radiosensitivity. Dietary phytochemicals coming from natural products are characterized by low cost, low toxicity, and general availability. Numerous phytochemicals are reported to regulate Nrf2 and intensify the killing capability of RT through diverse mechanisms, including promoting oxidative stress, proapoptosis, and proautophagy as well as inhibiting Nrf2-mediated cytoprotective genes expression. This review summarizes recent advances in radiosensitizing effects of dietary phytochemicals by targeting Nrf2 and discusses the underlying mechanisms, including N6-methyladenosine (m6A) modification of Nrf2 mediated by phytochemicals in cancer.

The Radiosensitivity Index (RSI) Gene Signature Identifies Distinct Tumor Immune Microenvironment Characteristics Associated with Susceptibility to Radiotherapy

PURPOSE

Radiotherapy (RT) is a mainstay of cancer care and accumulating evidence suggests the potential for synergism with components of the immune response. However, little data describes the tumor immune contexture in relation to RT-sensitivity. To address this challenge, we employed the radiation sensitivity index (RSI) gene signature to estimate the RT-sensitivity of >10,000 primary tumors and characterized their immune microenvironments in relation to the RSI.

MATERIAL AND METHODS

We analyzed gene expression profiles of 10,469 primary tumors (31 types) within a prospective tissue collection protocol. The RT-sensitivity of each tumor was estimated by the RSI and respective distributions were characterized. The tumor biology measured by the RSI was evaluated by differentially expressed genes (DEGs) combined with single sample gene set enrichment analysis (ssGSEA). Differences in the expression of immune regulatory molecules were assessed and deconvolution algorithms were used to estimate immune cell infiltrates in relation to the RSI. A subset (n=2,368) of tumors underwent DNA sequencing for mutational frequency characterization.

RESULTS

We identified a wide range of RSI values within and across various tumor types, with several demonstrating non-unimodal distributions (e.g. colon, renal, lung, prostate, esophagus, pancreas and PAM50 breast subtypes; p <0.05). Across all tumors types, stratifying RSI at a tumor type-specific median, identified 7,148 DEGs, of which 146 were coordinate in direction. Network topology analysis demonstrates RSI measures a coordinated STAT1, IRF1, and CCL4/MIP-1β transcriptional network. Tumors with an estimated high sensitivity to RT demonstrated distinct enrichment of interferon-associated signaling pathways and immune cell infiltrates (e.g. CD8+ T cells, activated natural killer cells, M1-macrophages; q < 0.05), which was in the context of diverse expression patterns of various immunoregulatory molecules.

CONCLUSION

This analysis describes the immune microenvironments of patient tumors in relation to the RSI gene expression signature.

Factors and molecular mechanisms of radiation resistance in cancer cells

PURPOSE

The aim of this work is to review the published studies on radiation resistance mechanisms and molecular markers involved in different tumors. The revision has been focused in the last 5 years (2016-2021).

CONCLUSIONS

Radioresistance is a cause of concern as it causes failure of radiation therapy and subsequent tumor relapse. Combination chemotherapy and radiation therapy are clinically successful in treating many types of tumors. Despite continued improvements in cancer treatment, locoregional recurrence or metastatic spread continues to occur in a high proportion of patients after being treated with radiation therapy or combination treatments. There is strong evidence that cancer stem cells contribute to radiation resistance, contributing to treatment failure. The mechanisms of radiation resistance in different tumors are not fully understood. A better understanding of cancer stem cells and the associated signaling pathways that regulate radiation resistance will open up new strategies for treating cancer by radiation therapy. Radiation can damage malignant cells mainly by the induction of DNA double strand breaks. However, in some tumors appear resistant cells that repopulate the tumor following therapy leading over time to the failure of the treatment. Native mechanisms and induced pathways, are the cause of radiation resistance. It has been described that numerous molecular markers acting through numerous mechanisms of action involved in radiation resistance, such as apoptosis resistance, alterations of cell growth, proliferation and DNA repair, hypoxia, increase in invasiveness and migration capacity, cell cycle alterations and expression of heat shock proteins, among others. Therefore, resistance to radiation is a multifactorial phenomenon that, in different cell types, it occurs through different regulatory mechanisms in which different molecules intervene. Resistance can be acquired by altering different regulatory pathways in different tumors. The knowledge of radiation resistance markers could help in the classification and treatment of patients with more aggressive tumors.

Molecular Composition of Serum Exosomes Could Discriminate Rectal Cancer Patients with Different Responses to Neoadjuvant Radiotherapy

Identification of biomarkers that could be used for the prediction of the response to neoadjuvant radiotherapy (neo-RT) in locally advanced rectal cancer remains a challenge addressed by different experimental approaches. Exosomes and other classes of extracellular vesicles circulating in patients' blood represent a novel type of liquid biopsy and a source of cancer biomarkers. Here, we used a combined proteomic and metabolomic approach based on mass spectrometry techniques for studying the molecular components of exosomes isolated from the serum of rectal cancer patients with different responses to neo-RT. This allowed revealing several proteins and metabolites associated with common pathways relevant for the response of rectal cancer patients to neo-RT, including immune system response, complement activation cascade, platelet functions, metabolism of lipids, metabolism of glucose, and cancer-related signaling pathways. Moreover, the composition of serum-derived exosomes and a whole serum was analyzed in parallel to compare the biomarker potential of both specimens. Among proteins that the most properly discriminated good and poor responders were GPLD1 (AUC = 0.85, accuracy of 74%) identified in plasma as well as C8G (AUC = 0.91, accuracy 81%), SERPINF2 (AUC = 0.91, accuracy 79%) and CFHR3 (AUC = 0.90, accuracy 81%) identified in exosomes. We found that the proteome component of serum-derived exosomes has the highest capacity to discriminate samples of patients with different responses to neo-RT when compared to the whole plasma proteome and metabolome. We concluded that the molecular components of exosomes are associated with the response of rectal cancer patients to neo-RT and could be used for the prediction of such response.

Radiotherapy resistance: identifying universal biomarkers for various human cancers

Radiotherapy (RT) is considered as a standard in the treatment of most solid cancers, including glioblastoma, lung, breast, rectal, prostate, colorectal, cervical, esophageal, and head and neck cancers. The main challenge in RT is tumor cell radioresistance associated with a high risk of locoregional relapse and distant metastasis. Despite significant progress in understanding mechanisms of radioresistance, its prediction and overcoming remain unresolved. This review presents the state-of-the-art for the potential universal biomarkers correlated to the radioresistance and poor outcome in different cancers. We describe radioresistance biomarkers functionally attributed to DNA repair, signal transduction, hypoxia, and angiogenesis. We also focus on high throughput genetic and proteomic studies, which revealed a set of molecular biomarkers related to radioresistance. In conclusion, we discuss biomarkers which are overlapped in most several cancers.

Metabolic response to radiation therapy in cancer

Tumor metabolism has emerged as a hallmark of cancer and is involved in carcinogenesis and tumor growth. Reprogramming of tumor metabolism is necessary for cancer cells to sustain high proliferation rates and enhanced demands for nutrients. Recent studies suggest that metabolic plasticity in cancer cells can decrease the efficacy of anticancer therapies by enhancing antioxidant defenses and DNA repair mechanisms. Studying radiation-induced metabolic changes will lead to a better understanding of radiation response mechanisms as well as the identification of new therapeutic targets, but there are few robust studies characterizing the metabolic changes induced by radiation therapy in cancer. In this review, we will highlight studies that provide information on the metabolic changes induced by radiation and oxidative stress in cancer cells and the associated underlying mechanisms.

Lipophagy-related protein perilipin-3 (PLIN3) and resistance of prostate cancer to radiotherapy

PURPOSE

Radiotherapy is a principal treatment modality for localized and locally advanced prostate cancer (PCa). Metabolic alterations, including lipid metabolism, may reduce treatment efficacy resulting in tumor relapse and poor therapeutic outcome. In the current study, we investigated the role of the lipophagy-related protein perilipin-3 (PLIN3) and the lysosomal acid lipase (LAL) in PCa response to radiotherapy.

METHODS AND MATERIALS

We explored the in vitro and xenograft (in NOD.SCID and R2G2 mice) response to radiation of either PLIN3-depleted or LAL-depleted hormone-refractory (DU145, PC3), and hormone-responsive 22Rv1 PCa cell lines. Moreover, we evaluated the clinical role of PLIN3 and LAL protein expression in a series of PCa tissue specimens from patients treated with radical radiotherapy.

RESULTS

In vitro and in vivo experiments showed reduced proliferation and strong radiosensitization of all studied PCa cell lines upon PLIN3 depletion. In vivo experiments demonstrated the significantly augmented radiotherapy efficacy upon PLIN3 depletion, resulting in extensive tissue necrosis. PLIN3 overexpression in tissue specimens was correlated with increased MIB1 proliferation index, increased autophagy flux, reduced response to radiotherapy and poor prognosis. The impact of LAL depletion on radiotherapy was of lesser importance.

CONCLUSIONS

Assessment of PLIN3 expression may identify subgroups of PCa patients less responsive to radiotherapy, and at high risk of relapse post irradiation. Whether radiotherapy efficacy may be enhanced by concurrent autophagy or PLIN3 inhibition in this sub-group of patients demands clinical evaluation.

Metabolic and lipidomic characterization of radioresistant MDA-MB-231 human breast cancer cells to investigate potential therapeutic targets

To provide preliminary insights into metabolic and lipidomic characteristics in radioresistant triple-negative breast cancer (TNBC) cells and suggest potential therapeutic targets, we performed a comprehensive metabolic and lipidomic profiling of radioresistant MDA-MB-231 (MDA-MB-231/RR) TNBC cells and their parental cells using gas chromatography-mass spectrometry and nano electrospray ionization-mass spectrometry, followed by multivariate statistical analysis. Buthionine sulfoximine (BSO) and radiation were co-treated to radioresistant TNBC cells. The level of glutathione (GSH) was significantly increased, and the levels of GSH synthesis-related metabolites, such as cysteine, glycine, and glutamine were also increased in MDA-MB-231/RR cells. In contrast, the level of lactic acid was significantly reduced. In addition, reactive oxygen species (ROS) level was decreased in MDA-MB-231/RR cells. In the lipidomic profiles of MDA-MB-231/RR cells, the levels of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were significantly increased, whereas those of most of the phosphatidylinositol species were significantly decreased. BSO sensitized MDA-MB-231/RR cells to radiotherapy, which resulted in decreased GSH level and increased ROS level and apoptosis. Radioresistant TNBC cells showed distinct metabolic and lipidomic characteristics compared to their parental cells. We suggested activated GSH, PC, and PE biosynthesis pathways as potential targets for treating radioresistant TNBC cells. Particularly, enhanced radiosensitivity was achieved by inhibition of GSH biosynthesis in MDA-MB-231/RR cells.

Cabazitaxel suppresses the proliferation and promotes the apoptosis and radiosensitivity of castration-resistant prostate cancer cells by inhibiting PI3K/AKT pathway

BACKGROUND

Cabazitaxel has been applied to the treatment of castration-resistant prostate cancer (CRPC), but the molecular mechanism remained to be fully understood.

METHODS

After treatment with Cabazitaxel alone or in combination with ionizing radiation (IR), CRPC cell viability, proliferation and apoptosis were determined by Cell Counting Kit-8 (CCK-8) assay, colony formation, and flow cytometry, respectively. Tumor volume was measured after the establishment of animal xenograft model. Relative expressions of proteins related to apoptosis (B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), and cleaved caspase 3) and phosphoinositide 3-kinase (PI3K)/AKT pathway were measured by Western blot, and the phosphorylated-PI3K/PI3K and p-AKT/AKT ratios were determined as well.

RESULTS

Cell viability and proliferation were suppressed, and apoptosis was promoted in CRPC cells after Cabazitaxel treatment alone, accompanied with upregulated expressions of Bax and cleaved caspase 3 and downregulated Bcl-2 expression. Also, a single treatment with Cabazitaxel resulted in suppression of PI3K/AKT pathway activation, along with downregulated expressions of p-PI3K and p-AKT and a reduced ratio of p-PI3K/PI3K to p-AKT/AKT. Meanwhile, Cabazitaxel enhanced the effects of IR on suppressing survival and promoting apoptosis in CRPC cells through downregulating Bcl-2 and upregulating Bax and cleaved caspase 3. However, Cabazitaxel suppressed IR-induced PI3K/AKT pathway activation via downregulating p-PI3K and p-AKT, leading to a reduced ratio of p-PI3K/PI3K to p-AKT/AKT. Furthermore, Cabazitaxel further promoted the effects of IR on suppressing tumor growth in vivo.

CONCLUSION

Cabazitaxel inhibited the proliferation and promoted the apoptosis and radiosensitivity of CRPC cells, which is related to the suppression of PI3K/AKT pathway, providing a therapeutic method for CRPC in clinical practice.

Effect of GADD45G on the radioresistance of nasopharyngeal carcinoma cells

The development of radioresistance by nasopharyngeal carcinoma (NPC) cells almost always results in tumor recurrence and metastasis, making clinical treatment of the disease difficult. In this study, the mechanism of radioresistance in NPC cells was investigated. First, a gene array and quantitative reverse-transcription-PCR assays were used to screen for genes exhibiting significantly altered expression in the DNA damage signaling pathway. Based on those results, GADD45G was further studied in the context of radioresistance. A GADD45G-knockout NPC cell line (CNE-2R-KO) was constructed using CRISPR-Cas9 technology and used for a comparison of differences in radioresistance with other radiosensitive and radioresistant NPC cells, as evaluated using colony formation assays. Cell cycle changes were observed using flow cytometry. Cell proliferation and migration were measured using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide and wound healing assays, respectively. The sequencing results revealed the successful construction of the CNE-2R-KO cell line, the radiosensitivity of which was higher than that of its parent radioresistant cell line owing to the GADD45G knockout. This was likely related to the increase in the number of cells in the G1 phase and decrease in those in the S1 phase as well as the increased cell proliferation rate and decreased migratory ability. GADD45G is associated with radioresistance in NPC cells and likely has a role in the occurrence and metastasis of NPC.

BPIFB1 inhibits vasculogenic mimicry via downregulation of GLUT1-mediated H3K27 acetylation in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) demonstrates significant regional differences and a high incidence in Southeast Asia and Southern China. Bactericidal/permeability-increasing-fold- containing family B member 1 (BPIFB1) is a relatively specific and highly expressed protein in the nasopharyngeal epithelium. BPIFB1 expression is substantially downregulated in NPC and is significantly associated with poor prognosis in patients with NPC. However, the specific molecular mechanism by which BPIFB1 regulates NPC is not well understood. In this study, we found that BPIFB1 inhibits vasculogenic mimicry by regulating the metabolic reprogramming of NPC. BPIFB1 decreases GLUT1 transcription by downregulating the JNK/AP1 signaling pathway. Altered glycolysis reduces the acetylation level of histone and decreases the expression of vasculogenic mimicry-related genes, VEGFA, VE-cadherin, and MMP2, ultimately leading to the inhibition of vasculogenic mimicry. To our knowledge, this is the first report on the role and specific mechanism of BPIFB1 as a tumor suppressor gene involved in regulating glycolysis and vasculogenic mimicry in NPC. Overall, these results provide a new therapeutic target for NPC diagnosis and treatment.

Combination of Radiosensitivity Gene Signature and PD-L1 Status Predicts Clinical Outcome of Patients With Locally Advanced Head and Neck Squamous Cell Carcinoma: A Study Based on The Cancer Genome Atlas Dataset

Aim: The aim of our study was to investigate the potential predictive value of the combination of radiosensitivity gene signature and PD-L1 expression for the prognosis of locally advanced head and neck squamous cell carcinoma (HNSCC).

Methods: The cohort was selected from The Cancer Genome Atlas (TCGA) and classified into the radiosensitive (RS) group and radioresistant (RR) group by a radiosensitivity-related gene signature. The cohort was also grouped as PD-L1-high or PD-L1-low based on PD-L1 mRNA expression. The least absolute shrinkage and selection operator (lasso)-based Cox model was used to select hub survival genes. An independent validation cohort was obtained from the Gene Expression Omnibus (GEO) database.

Results: We selected 288 locally advanced HNSCC patients from TCGA. The Kaplan–Meier method found that the RR and PD-L1-high group had a worse survival than others (p = 0.033). The differentially expressed gene (DEG) analysis identified 553 upregulated genes and 486 downregulated genes (p < 0.05, fold change >2) between the RR and PD-L1-high group and others. The univariate Cox analysis of each DEG and subsequent lasso-based Cox model revealed five hub survival genes (POU4F1, IL34, HLF, CBS, and RNF165). A further hub survival gene-based risk score model was constructed, which was validated by an external cohort. We observed that a higher risk score predicted a worse prognosis (p = 0.0013). The area under the receiver operating characteristic curve (AUC) plots showed that this risk score model had good prediction value (1-year AUC = 0.684, 2-year AUC = 0.702, and 3-year AUC = 0.688). Five different deconvolution methods all showed that the B cells were lower in the RR and PD-L1-high group (p < 0.05). Finally, connectivity mapping analysis showed that the histone deacetylase (HDAC) inhibitor trichostatin A might have the potential to reverse the phenotype of RR and PD-L1-high in locally advanced HNSCC (p < 0.05, false discovery rate <0.1).

Conclusion: The combination of 31-gene signature and the PD-L1 mRNA expression had a potential predictive value for the prognosis of locally advanced HNSCC who had RT. The B cells were lower in the RR and PD-L1-high group. The identified risk gene signature of locally advanced HNSCC and the potential therapeutic drug trichostatin A for the RR and PD-L1-high group are worth being further studied in a prospective homogenous cohort.

Dose-dependent expression of extracellular microRNAs in HCT116 colorectal cancer cells exposed to high-dose-rate ionising radiation

Biomarkers of tumour response to radiotherapy may help optimise cancer treatment. The aim of the present study was to identify changes in extracellular microRNAs (miRNAs) as a biomarker of radiation-induced damage to human colorectal cancer cells. HCT116 cells were exposed to increasing doses of X-rays, and extracellular miRNAs were analysed by microarray. The results were correlated with the frequency of micronuclei. A total of 59 miRNAs with a positive correlation and 4 with a negative correlation between dose (up to 6 Gy) and extracellular miRNA expression were identified. In addition, for doses between 0 and 10 Gy, 12 miRNAs among those 59 miRNAs with a positive correlation were identified; for these extracellular miRNAs, a significantly positive correlation was observed between their expression and the frequency of micronuclei for doses up to 10 Gy. These results suggest that specific miRNAs may be considered as cell damage markers and may serve as secreted radiotherapy response biomarkers for colorectal cancer; however, the results must be further validated in serum samples collected from patients undergoing radiotherapy.

Help or hindrance: The obesity paradox in cancer treatment response

Obesity is a rising epidemic, the influence of which on cancer development, progression as well as its impact on current standard of care cancer treatments is profound with many facets. Obesity is emerging as a modulating factor in many cancer therapies, such as chemotherapy, radiotherapy, immunotherapy and combination therapies. It has been reported to diminish the efficacy of some treatments but has also been alluded to being protective in terms of reduced treatment toxicities, thus the evolution of the obesity paradox. The obese tumour microenvironment influences treatment response through modulation of a series of aspects, including altered adipocyte secretome, angiogenesis, hypoxia, fibrosis, free fatty acid uptake as well as a modulated immune landscape. However, the influence of these underlying mechanisms on cancer treatment response and the biological action of adipose tissue is still largely unknown. Elucidation of these facets may lead to the enhanced efficacy of current treatment options or the identification of novel methods to combat cancer in the obese tumour microenvironment.

EGFR-mediated Rad51 expression potentiates intrinsic resistance in prostate cancer via EMT and DNA repair pathways

AIM

To study the role of EGFR signaling in regulation of intrinsic resistance in prostate cancer.

MATERIALS AND METHODS

Radioresistant prostate carcinoma DU145 and PC-3 cells were used to study the effect of shRNA-mediated knockdown of EGFR on intrinsic radioresistance mechanisms. Semi-quantitative PCR, western blotting, growth kinetics, colony formation, transwell migration, invasion and trypan blue assays along with inhibitors erlotinib, NU7441, B02, PD98059 and LY294002 were used.

KEY FINDINGS

EGFR knock-down induced morphological alterations along with reduction in clonogenic potential and cell proliferation in DU145 cells. Migratory potential of prostate cancer cells were reduced concomitant with upregulation of epithelial marker, E-cadherin and decreased expression of mesenchymal markers, vimentin and snail. Further, EGFR knock-down decreased the expression of Rad51 and DNA-PK at mRNA as well as protein levels. Likewise, erlotinib, an EGFR inhibitor, and NU7441, a DNA-PK inhibitor increased the expression of E-cadherin and decreased the level of vimentin. Both these inhibitors also decreased the levels of DNA damage regulatory protein Rad51. Further, Rad51 inhibitor, B02, inhibited the clonogenic potential, cell migration and reduced the expression of vimentin, Ku70 and Ku80, and also, B02 radiosensitized DU145 cells. EGFR-regulated expression of Rad51 was found to be mediated via PI3K/Akt and Erk1/2 pathways.

SIGNIFICANCE

EGFR was found to regulate DNA damage repair, survival and EMT responses in prostate cancer cells through transcriptional regulation of Rad51. A novel role of EGFR-Erk1/2/Akt-Rad51 axis through modulation of EMT and DNA repair pathways in prostate cancer resistance mechanisms is suggested.

Impact of Pelvic Radiation Therapy for Prostate Cancer on Global Metabolic Profiles and Microbiota-Driven Gastrointestinal Late Side Effects: A Longitudinal Observational Study

PURPOSE

Radiation therapy to the prostate and pelvic lymph nodes (PLNRT) is part of the curative treatment of high-risk prostate cancer. Yet, the broader influence of radiation therapy on patient physiology is poorly understood. We conducted comprehensive global metabolomic profiling of urine, plasma, and stools sampled from patients undergoing PLNRT for high-risk prostate cancer.

METHODS AND MATERIALS

Samples were taken from 32 patients at 6 timepoints: baseline, 2 to 3 and 4 to 5 weeks of PLNRT; and 3, 6, and 12 months after PLNRT. We characterized the global metabolome of urine and plasma using 1H nuclear magnetic resonance spectroscopy and ultraperformance liquid chromatography-mass spectrometry, and of stools with nuclear magnetic resonance. Linear mixed-effects modeling was used to investigate metabolic changes between timepoints for each biofluid and assay and determine metabolites of interest.

RESULTS

Metabolites in urine, plasma and stools changed significantly after PLNRT initiation. Metabolic profiles did not return to baseline up to 1 year post-PLNRT in any biofluid. Molecules associated with cardiovascular risk were increased in plasma. Pre-PLNRT fecal butyrate levels directly associated with increasing gastrointestinal side effects, as did a sharper fall in those levels during and up to 1 year postradiation therapy, mirroring our previous results with metataxonomics.

CONCLUSIONS

We showed for the first time that an overall metabolic effect is observed in patients undergoing PLNRT up to 1 year posttreatment. These metabolic changes may effect on long-term morbidity after treatment, which warrants further investigation.

Radiosensitizing Effect of Bromelain Using Tumor Mice Model via Ki-67 and PARP-1 Inhibition

Recent reports have shown that bromelain (BL), a pineapple extract, acts as an adjuvant therapy in cancer treatment and prevention of carcinogenesis. The present study was designed to investigate the possible mechanisms by which BL could radiosensitize tumor cells in vitro and in a mouse tumor model. BL has shown a significant reduction in the viability of the radioresistant human breast carcinoma (MCF-7) cell line using cell proliferation assay. The in vivo study was designed using the Ehrlich model in female albino mice, treated with BL (6 mg/kg b. wt., intraperitoneal, once daily for 10 days) 1 hour before exposure to a fractionated dose of gamma radiation (5 Gy, 1 Gy for 5 subsequent days). The radiosensitizing effect of BL was evident in terms of a significant reduction in tumor volume, poly ADP ribose polymerase-1 (PARP-1), the proliferation marker Ki-67 and nuclear factor kappa activated B cells (NF-κB) with a significant elevation in the reactive oxygen species (ROS) content and lipid peroxidation (LPO) in tumor cells. The present findings offer a novel insight into the radiosensitizing effect of BL and its potential application in the radiotherapy course.

The MTT Assay: Utility, Limitations, Pitfalls, and Interpretation in Bulk and Single-Cell Analysis

The MTT assay for cellular metabolic activity is almost ubiquitous to studies of cell toxicity; however, it is commonly applied and interpreted erroneously. We investigated the applicability and limitations of the MTT assay in representing treatment toxicity, cell viability, and metabolic activity. We evaluated the effect of potential confounding variables on the MTT assay measurements on a prostate cancer cell line (PC-3) including cell seeding number, MTT concentration, MTT incubation time, serum starvation, cell culture media composition, released intracellular contents (cell lysate and secretome), and extrusion of formazan to the extracellular space. We also assessed the confounding effect of polyethylene glycol (PEG)-coated gold nanoparticles (Au-NPs) as a tested treatment in PC-3 cells on the assay measurements. We additionally evaluated the applicability of microscopic image cytometry as a tool for measuring intracellular MTT reduction at the single-cell level. Our findings show that the assay measurements are a result of a complicated process dependant on many of the above-mentioned factors, and therefore, optimization of the assay and rational interpretation of the data is necessary to prevent misleading conclusions on variables such as cell viability, treatment toxicity, and/or cell metabolism. We conclude, with recommendations on how to apply the assay and a perspective on where the utility of the assay is a powerful tool, but likewise where it has limitations.

The Herbal Formula JI017 Induces ER Stress via Nox4 in Breast Cancer Cells

Chemotherapy is a powerful anti-tumor therapeutic strategy; however, resistance to treatment remains a serious concern. To overcome chemoresistance, combination therapy with anticancer drugs is a potential strategy. We developed a novel herbal extract, JI017, with lower toxicity and lesser side effects. JI017 induced programmed cell death and excessive unfolded protein response through the release of intracellular reactive oxygen species (ROS) and calcium in breast cancer cells. JI017 treatment increased the expression of endoplasmic reticulum (ER) stress markers, including p-PERK, p-eIF2α, ATF4, and CHOP, via the activation of both exosomal GRP78 and cell lysate GRP78. The ROS inhibitors diphenyleneiodonium and N-acetyl cysteine suppressed apoptosis and excessive ER stress by inhibiting Nox4 in JI017-treated breast cancer cells. Furthermore, in paclitaxel-resistant breast cancer cell lines, MCF-7R and MDA-MB-231R, a combination of JI017 and paclitaxel overcame paclitaxel resistance by blocking epithelial-mesenchymal transition (EMT) processes, such as the downregulation of E-cadherin expression and the upregulation of HIF-1α, vimentin, Snail, and Slug expression. These findings suggested that JI017 exerts a powerful anti-cancer effect in breast cancer and a combination therapy of JI017 and paclitaxel may be a potential cancer therapy for paclitaxel resistant breast cancer.

Targeting the metabolism of cancer stem cells by energy disruptor molecules

Cancer stem cells (CSCs) have been identified in various tumor types. CSCs are believed to contribute to tumor metastasis and resistance to conventional therapy. So targeting these cells could be an effective strategy to eliminate tumors and a promising new type of cancer treatment. Alterations in metabolism play an essential role in CSC biology and their resistance to treatment. The metabolic properties pathways in CSCs are different from normal cells, and to some extent, are different from regular tumor cells. Interestingly, CSCs can use other nutrients for their metabolism and growth. The different metabolism causes increased sensitivity of CSCs to agents that disrupt cellular homeostasis. Compounds that interfere with the central metabolic pathways are known as energy disruptors and can reduce CSC survival. This review highlights the differences between regular cancer cells and CSC metabolism and discusses the action mechanisms of energy disruptors at the cellular and molecular levels.

Metabolism of cancer cells commonly responds to irradiation by a transient early mitochondrial shutdown

Cancer bioenergetics fuel processes necessary to maintain viability and growth under stress conditions. We hypothesized that cancer metabolism supports the repair of radiation-induced DNA double-stranded breaks (DSBs). We combined the systematic collection of metabolic and radiobiological data from a panel of irradiated cancer cell lines with mathematical modeling and identified a common metabolic response with impact on the DSB repair kinetics, including a mitochondrial shutdown followed by compensatory glycolysis and resumption of mitochondrial function. Combining ionizing radiation (IR) with inhibitors of the compensatory glycolysis or mitochondrial respiratory chain slowed mitochondrial recovery and DNA repair kinetics, offering an opportunity for therapeutic intervention. Mathematical modeling allowed us to generate new hypotheses on general and individual mechanisms of the radiation response with relevance to DNA repair and on metabolic vulnerabilities induced by cancer radiotherapy. These discoveries will guide future mechanistic studies for the discovery of metabolic targets for overcoming intrinsic or therapy-induced radioresistance.

Radioresistance of Human Cancers: Clinical Implications of Genetic Expression Signatures

Although radiotherapy is given to more than 50% of cancer patients, little progress has been made in identifying optimal radiotherapy - drug combinations to improve treatment efficacy. Using molecular data from The Cancer Genome Atlas (TCGA), we extracted a total of 1016 cancer patients that received radiotherapy. The patients were diagnosed with head-and-neck (HNSC - 294 patients), cervical (CESC - 166 patients) and breast (BRCA - 549 patients) cancer. We analyzed mRNA expression patterns of 50 hallmark gene sets of the MSigDB collection, which we divided in eight categories based on a shared biological or functional process. Tumor samples were split into upregulated, neutral or downregulated mRNA expression for all gene sets using a gene set analysis (GSEA) pre-ranked analysis and assessed for their clinical relevance. We found a prognostic association between three of the eight gene set categories (Radiobiological, Metabolism and Proliferation) and overall survival in all three cancer types. Furthermore, multiple single associations were revealed in the other categories considered. To the best of our knowledge, our study is the first report suggesting clinical relevance of molecular characterization based on hallmark gene sets to refine radiation strategies.

Radiosensitization effects by bismuth oxide nanorods of different sizes in megavoltage external beam radiotherapy

Background

Nanotechnology application has successfully reached numerous scientific breakthroughs including in radiotherapy. However, the clinical application of nanoparticles requires more diligent research primarily on the crucial parameters such as nanoparticle sizes. This study is aimed to investigate the influence of bismuth oxide nanorod (Bi₂O₃-NR) sizes on radiosensitization effects on MCF-7 and HeLa cell lines for megavoltage photon and electron beam radiotherapy.

Materials and methods

MCF-7 and HeLa cells were treated with and without 0.5 μMol/L of Bi₂O₃-NR of varying sizes (60, 70, 80, and 90 nm). The samples, including the control groups, were exposed to different radiation doses (0-10 Gy), using photon (6 MV and 10 MV), and electron beam (6 MeV and 12 MeV) radiotherapy. Clonogenic assay was performed, and sensitization enhancement ratio (SER) was determined from linear quadratic based cell survival curves.

Results

The results depicted that 60 nm Bi₂O₃-NR yields the most excellent SER followed by 70 nm Bi₂O₃-NR. Meanwhile, the 80 and 90 nm Bi₂O₃-NR showed an insignificant difference between treated and untreated cell groups. This study also found that MCF-7 was subjected to more cell death compared to HeLa.

Conclusion

60 nm Bi₂O₃-NR was the optimal Bi₂O₃-NR size to induce radiosensitization effects for megavoltage external beam radiotherapy. The SER in photon beam radiotherapy marked the highest compared to electron beam radiotherapy due to decreased primary radiation energy from multiple radiation interaction and higher Compton scattering.

DNAzymes, Novel Therapeutic Agents in Cancer Therapy: A Review of Concepts to Applications

The past few decades have witnessed a rapid evolution in cancer drug research which is aimed at developing active biological interventions to regulate cancer-specific molecular targets. Nucleic acid-based therapeutics, including ribozymes, antisense oligonucleotides, small interference RNA (siRNA), aptamer, and DNAzymes, have emerged as promising candidates regulating cancer-specific genes at either the transcriptional or posttranscriptional level. Gene-specific catalytic DNA molecules, or DNAzymes, have shown promise as a therapeutic intervention against cancer in various in vitro and in vivo models, expediting towards clinical applications. DNAzymes are single-stranded catalytic DNA that has not been observed in nature, and they are synthesized through in vitro selection processes from a large pool of random DNA libraries. The intrinsic properties of DNAzymes like small molecular weight, higher stability, excellent programmability, diversity, and low cost have brought them to the forefront of the nucleic acid-based therapeutic arsenal available for cancers. In recent years, considerable efforts have been undertaken to assess a variety of DNAzymes against different cancers. However, their therapeutic application is constrained by the low delivery efficiency, cellular uptake, and target detection within the tumour microenvironment. Thus, there is a pursuit to identify efficient delivery methods in vivo before the full potential of DNAzymes in cancer therapy is realized. In this light, a review of the recent advances in the use of DNAzymes against cancers in preclinical and clinical settings is valuable to understand its potential as effective cancer therapy. We have thus sought to firstly provide a brief overview of construction and recent improvements in the design of DNAzymes. Secondly, this review stipulates the efficacy, safety, and tolerability of DNAzymes developed against major hallmarks of cancers tested in preclinical and clinical settings. Lastly, the recent advances in DNAzyme delivery systems along with the challenges and prospects for the clinical application of DNAzymes as cancer therapy are also discussed.

HAX1 maintains the glioma progression in hypoxia through promoting mitochondrial fission

HCLS1‐associated protein X‐1 (HAX1), an anti‐apoptotic molecular, overexpresses in glioma. However, the role of HAX1 in glioma cell surviving in hypoxic environment remains unclear. Western blotting, qRT‐PCR, Transwell assay, TUNEL assay, wounding healing assay, clone formation, tumour xenograft model and immunohistochemical staining were used to investigate the role of HAX1 in glioma. HAX1 regulated by HIF‐1α was increased in glioma cells cultured in hypoxia. Silencing of HAX1 could cause an increased apoptosis of glioma cells cultured in hypoxia. Silencing of HAX1 also decreased the proliferation, migration and invasion of glioma cells cultured in hypoxia. Increased mitochondrial fission could prevent glioma cells from the damage induced by HAX1 knockdown in hypoxia. Furthermore, HAX1 was found to regulate glioma cells through phosphorylated AKT/Drp signal pathway. In conclusion, our study suggested that HAX1 promoted survival of glioma cells in hypoxic environment via AKT/Drp signal pathway. Our study also provided a potential therapeutic target for glioma.

Dual Hyaluronic Acid and Folic Acid Targeting pH-Sensitive Multifunctional 2DG@DCA@MgO-Nano-Core-Shell-Radiosensitizer for Breast Cancer Therapy

Simple Summary

In this study, we have developed CD44 and folate receptor-targeting multi-functional dual drug-loaded nanoparticles. This comprises hyaluronic acid (HA) and folic acid (FA) conjugated to 2-deoxy glucose (2DG) and a shell linked to a dichloroacetate (DCA) and magnesium oxide (MgO) core (2DG@DCA@MgO; DDM) to enhance the localized chemo-radiotherapy for effective breast cancer (BC) treatment. The physicochemical properties of nanoparticles including stability, selectivity, responsive release to pH, cellular uptake, and anticancer efficacy were comprehensively examined. Mechanistically, we identified multiple component signal pathways as important regulators of BC metabolism and mediators for the inhibitory effects exerted by DDM. Nanoparticles exhibited sustained DDM release properties in bio-relevant media, which was responsive to acidic pH providing edibility to the control of drug release from nanoparticles. DDM-loaded and HA–FA-functionalized nanoparticles exhibited increased selectivity and uptake by BC cells. Cell-based assays indicated that the functionalized DDM significantly suppressed cancer cell growth and boosted radiotherapy (RT) efficacy via inducing cell cycle arrest, enhancing apoptosis, and modulating glycolytic and OXPHOS pathways. Accordingly, the inhibition of glycolysis/OXPHOS by DDM and RT treatment may result in cancer metabolic reprogramming via a novel PI3K/AKT/mTOR/P53NF-κB/VEGF pathway in BC cells. Therefore, the dual targeting of glycolysis/OXPHOS pathways is suggested as a promising antitumor strategy.

Abstract

Globally, breast cancer (BC) poses a serious public health risk. The disease exhibits a complex heterogeneous etiology and is associated with a glycolytic and oxidative phosphorylation (OXPHOS) metabolic reprogramming phenotype, which fuels proliferation and progression. Due to the late manifestation of symptoms, rigorous treatment regimens are required following diagnosis. Existing treatments are limited by a lack of specificity, systemic toxicity, temporary remission, and radio-resistance in BC. In this study, we have developed CD44 and folate receptor-targeting multi-functional dual drug-loaded nanoparticles. This composed of hyaluronic acid (HA) and folic acid (FA) conjugated to a 2-deoxy glucose (2DG) shell linked to a layer of dichloroacetate (DCA) and a magnesium oxide (MgO) core (2DG@DCA@MgO; DDM) to enhance the localized chemo-radiotherapy for effective BC treatment. The physicochemical properties of nanoparticles including stability, selectivity, responsive release to pH, cellular uptake, and anticancer efficacy were thoroughly examined. Mechanistically, we identified multiple component signaling pathways as important regulators of BC metabolism and mediators for the inhibitory effects elicited by DDM. Nanoparticles exhibited sustained DDM release properties in a bio-relevant media, which was responsive to the acidic pH enabling eligibility to the control of drug release from nanoparticles. DDM-loaded and HA–FA-functionalized nanoparticles exhibited increased selectivity and uptake by BC cells. Cell-based assays revealed that the functionalized DDM significantly suppressed cancer cell growth and improved radiotherapy (RT) through inducing cell cycle arrest, enhancing apoptosis, and modulating glycolytic and OXPHOS pathways. By highlighting DDM mechanisms as an antitumor and radio-sensitizing reagent, our data suggest that glycolytic and OXPHOS pathway modulation occurs via the PI3K/AKT/mTOR/NF-κB/VEGF_low and P53_high signaling pathway. In conclusion, the multi-functionalized DDM opposed tumor-associated metabolic reprogramming via multiple signaling pathways in BC cells as a promising targeted metabolic approach.

Clinical and Preclinical Outcomes of Combining Targeted Therapy With Radiotherapy

In the era of precision medicine, radiation medicine is currently focused on the precise delivery of highly conformal radiation treatments. However, the tremendous developments in targeted therapy are yet to fulfill their full promise and arguably have the potential to dramatically enhance the radiation therapeutic ratio. The increased ability to molecularly profile tumors both at diagnosis and at relapse and the co-incident progress in the field of radiogenomics could potentially pave the way for a more personalized approach to radiation treatment in contrast to the current ‘‘one size fits all’’ paradigm. Few clinical trials to date have shown an improved clinical outcome when combining targeted agents with radiation therapy, however, most have failed to show benefit, which is arguably due to limited preclinical data. Several key molecular pathways could theoretically enhance therapeutic effect of radiation when rationally targeted either by directly enhancing tumor cell kill or indirectly through the abscopal effect of radiation when combined with novel immunotherapies. The timing of combining molecular targeted therapy with radiation is also important to determine and could greatly affect the outcome depending on which pathway is being inhibited.

miR-29b-3p Increases Radiosensitivity in Stemness Cancer Cells via Modulating Oncogenes Axis

Radioresistance conferred by cancer stem cells (CSCs) is the principal cause of the failure of cancer radiotherapy. Eradication of CSCs is a prime therapeutic target and a requirement for effective radiotherapy. Three dimensional (3D) cell-cultured model could mimic the morphology of cells in vivo and induce CSC properties. Emerging evidence suggests that microRNAs (miRNAs) play crucial roles in the regulation of radiosensitivity in cancers. In this study, we aim to investigate the effects of miRNAs on the radiosensitivity of 3D cultured stem-like cells. Using miRNA microarray analysis in 2D and 3D cell culture models, we found that the expression of miR-29b-3p was downregulated in 3D cultured A549 and MCF7 cells compared with monolayer (2D) cells. Clinic data analysis from The Cancer Genome Atlas database exhibited that miR-29b-3p high expression showed significant advantages in lung adenocarcinoma and breast invasive carcinoma patients’ prognosis. The subsequent experiments proved that miR-29b-3p overexpression decreased the radioresistance of cells in 3D culture and tumors in vivo through interfering kinetics process of DNA damage repair and inhibiting oncogenes RBL1, PIK3R1, AKT2, and Bcl-2. In addition, miR-29b-3p knockdown enhanced cancer cells invasion and migration capability. MiR-29b-3p overexpression decreased the stemness of 3D cultured cells. In conclusion, our results demonstrate that miR-29b-3p could be a sensitizer of radiation killing in CSC-like cells via inhibiting oncogenes expression. MiR-29b-3p could be a novel therapeutic candidate target for radiotherapy.

Long Noncoding RNAs Regulate the Radioresistance of Breast Cancer

Breast cancer (BRCA) has severely threatened women's health worldwide. Radiotherapy is a treatment for BRCA, which applies high doses of ionizing radiation to induce cancer cell death and reduce disease recurrence. Radioresistance is one of the most important elements that affect the therapeutic efficacy of radiotherapy. Long noncoding RNAs (lncRNAs) are suggested to dominate crucial roles in regulating the biological behavior of BRCA. Currently, some studies indicate that overexpression or inhibition of lncRNAs can greatly alter the radioresistance of BRCA. In this review, we summarized the knowledge on the classification and function of lncRNAs and the molecular mechanism of BRCA radioresistance, listed lncRNAs related to the BRCA radioresistance, highlighted their underlying mechanisms, and discussed the potential application of these lncRNAs in regulating BRCA radioresistance.

Adjuvant therapy for high-risk cutaneous squamous cell carcinoma: 10-year review

Standard of care for high-risk cutaneous squamous cell carcinoma (cSCC) is surgical excision of the primary lesion with clear margins when possible, and additional resection of positive margins when feasible. Even with negative margins, certain high-risk factors warrant consideration of adjuvant therapy. However, which patients might benefit from adjuvant therapy is unclear, and supporting evidence is conflicting and limited to mostly small retrospective cohorts. Here, we review literature from the last decade regarding adjuvant radiation therapy and systemic therapy in high-risk cSCC, including recent and current trials and the role of immune checkpoint inhibitors. We demonstrate evidence gaps in adjuvant therapy for high-risk cSCC and the need for prognostic tools, such as gene expression profiling, to guide patient selection. More large-cohort clinical studies are needed for collecting high-quality, evidence-based data for determining which patients with high-risk cSCC may benefit from adjuvant therapy and which therapy is most appropriate for patient management.

The promising potential of piperlongumine as an emerging therapeutics for cancer

In spite of the immense advancement in the diagnostic and treatment modalities, cancer continues to be one of the leading causes of mortality across the globe, responsible for the death of around 10 million patients every year. The foremost challenges faced in the treatment of this disease are chemoresistance, adverse effects of the drugs, and the high cost of treatment. Though scientific studies over the past few decades have foreseen and are focusing on the cancer-preventive and therapeutic potential of natural products and their underlying mechanism of action, many more of these agents are not still explored. Piperlongumine (PL), or piplartine, is one such alkaloid isolated from Piper longum Linn. which is shown to be safe and has significant potential in the prevention and therapy of cancer. Numerous shreds of evidence have established the ability of this alkaloid and its analogs and nanoformulations in modulating various complex molecular pathways such as phosphatidylinositol-3-kinase/protein kinase B /mammalian target of rapamycin, nuclear factor kappa-B, Janus kinases/signal transducer and activator of transcription 3, etc. and inhibit different hallmarks of cancer such as cell survival, proliferation, invasion, angiogenesis, epithelial-mesenchymal-transition, metastases, etc. In addition, PL was also shown to inhibit radioresistance and chemoresistance and sensitize the cancer cells to the standard chemotherapeutic agents. Therefore, this compound has high potential as a drug candidate for the prevention and treatment of different cancers. The current review briefly reiterates the anti-cancer properties of PL against different types of cancer, which permits further investigation by conducting clinical studies.

Evaluation of Epigenetic and Radiomodifying Effects during Radiotherapy Treatments in Zebrafish

Radiotherapy is still a long way from personalizing cancer treatment plans, and its effectiveness depends on the radiosensitivity of tumor cells. Indeed, therapies that are efficient and successful for some patients may be relatively ineffective for others. Based on this, radiobiological research is focusing on the ability of some reagents to make cancer cells more responsive to ionizing radiation, as well as to protect the surrounding healthy tissues from possible side effects. In this scenario, zebrafish emerged as an effective model system to test for radiation modifiers that can potentially be used for radiotherapeutic purposes in humans. The adoption of this experimental organism is fully justified and supported by the high similarity between fish and humans in both their genome sequences and the effects provoked in them by ionizing radiation. This review aims to provide the literature state of the art of zebrafish in vivo model for radiobiological studies, particularly focusing on the epigenetic and radiomodifying effects produced during fish embryos’ and larvae’s exposure to radiotherapy treatments.