DNA damage response signaling pathways and targets for radiotherapy sensitization in cancer

Overcoming the Impact of Hypoxia in Driving Radiotherapy Resistance in Head and Neck Squamous Cell Carcinoma

Hypoxia is very common in most solid tumours and is a driving force for malignant progression as well as radiotherapy and chemotherapy resistance. Incidences of head and neck squamous cell carcinoma (HNSCC) have increased in the last decade and radiotherapy is a major therapeutic technique utilised in the treatment of the tumours. However, effectiveness of radiotherapy is hindered by resistance mechanisms and most notably by hypoxia, leading to poor patient prognosis of HNSCC patients. The phenomenon of hypoxia-induced radioresistance was identified nearly half a century ago, yet despite this, little progress has been made in overcoming the physical lack of oxygen. Therefore, a more detailed understanding of the molecular mechanisms of hypoxia and the underpinning radiobiological response of tumours to this phenotype is much needed. In this review, we will provide an up-to-date overview of how hypoxia alters molecular and cellular processes contributing to radioresistance, particularly in the context of HNSCC, and what strategies have and could be explored to overcome hypoxia-induced radioresistance.

Mechanisms governing the accessibility of DNA damage proteins to constitutive heterochromatin

Chromatin is thought to regulate the accessibility of the underlying DNA sequence to machinery that transcribes and repairs the DNA. Heterochromatin is chromatin that maintains a sufficiently high density of DNA packing to be visible by light microscopy throughout the cell cycle and is thought to be most restrictive to transcription. Several studies have suggested that larger proteins and protein complexes are attenuated in their access to heterochromatin. In addition, heterochromatin domains may be associated with phase separated liquid condensates adding further complexity to the regulation of protein concentration within chromocenters. This provides a solvent environment distinct from the nucleoplasm, and proteins that are not size restricted in accessing this liquid environment may partition between the nucleoplasm and heterochromatin based on relative solubility. In this study, we assessed the accessibility of constitutive heterochromatin in mouse cells, which is organized into large and easily identifiable chromocenters, to fluorescently tagged DNA damage response proteins. We find that proteins larger than the expected 10 nm size limit can access the interior of heterochromatin. We find that the sensor proteins Ku70 and PARP1 enrich in mouse chromocenters. At the same time, MRE11 shows variability within an asynchronous population that ranges from depleted to enriched but is primarily homogeneously distribution between chromocenters and the nucleoplasm. While larger downstream proteins such as ATM, BRCA1, and 53BP1 are commonly depleted in chromocenters, they show a wide range of concentrations, with none being depleted beyond approximately 75%. Contradicting exclusively size-dependent accessibility, many smaller proteins, including EGFP, are also depleted in chromocenters. Our results are consistent with minimal size-dependent selectivity but a distinct solvent environment explaining reduced concentrations of diffusing nucleoplasmic proteins within the volume of the chromocenter.

Emerging roles of ferroptosis in glioma

Glioma is the most common primary malignant tumor in the central nervous system, and directly affects the quality of life and cognitive function of patients. Ferroptosis, is a new form of regulated cell death characterized by iron-dependent lipid peroxidation. Ferroptosis is mainly due to redox imbalance and involves multiple intracellular biology processes, such as iron metabolism, lipid metabolism, and antioxidants synthesis. Induction of ferroptosis could be a new target for glioma treatment, and ferroptosis-related processes are associated with chemoresistance and radioresistance in glioma. In the present review, we provide the characteristics, key regulators and pathways of ferroptosis and the crosstalk between ferroptosis and other programmed cell death in glioma, we also proposed the application and prospect of ferroptosis in the treatment of glioma.

Irradiation combined with PD-L1-/- and autophagy inhibition enhances the antitumor effect of lung cancer via cGAS-STING-mediated T cell activation

Radiotherapy combined with immune checkpoint blockade has gradually revealed the superiority in the antitumor therapy; however, the contribution of host PD-L1 remains elusive. In this study, we found that the activation of CD8⁺ T cells was strikingly increased in both irradiated PD-L1-expressing primary tumor and distant non-irradiated syngeneic tumor in PD-L1-deficient mouse host, and thus enhanced radiation-induced antitumor abscopal effect (ATAE) by activating cGAS-STING pathway. Notably, the autophagy inhibitors distinctively promoted dsDNA aggregation in the cytoplasm and increased the release of cGAS-STING-regulated IFN-β from irradiated cells, which further activated bystander CD8⁺ T cells to release IFN-γ and contributed to ATAE. These findings revealed a signaling cascade loop that the cytokines released from irradiated tumor recruit CD8⁺ T cells that in turn act on the tumor cells with amplified immune responses in PD-L1-deficient host, indicating a potential sandwich therapy strategy of RT combined with PD-L1 blockage and autophagy inhibition.

DNA repair inhibitors and radiotherapy

Radiotherapy (RT) is one of the main cancer treatments and grows in importance due to improved techniques. DNA damage caused by ionizing radiation creates DNA strand breaks that trigger an intervention of DNA repair pathways involving numerous proteins and enzymes. In recent years, we have identified DNA repair inhibitors as targets for inhibiting cellular repair systems and thus causing cell death. Combining RT with these DNA repair inhibitors appears to be a new approach for cancer treatment, but safety and real efficiency of this combination in practice is unclear. Numerous trials are underway in various diseases and initial results are promising overall, yet remain controversial.

Targeting O-GlcNAcylation to overcome resistance to anti-cancer therapies

In cancer cells, metabolic reprogramming is associated with an alteration of the O-GlcNAcylation homeostasis. This post-translational modification (PTM) that attaches O-GlcNAc moiety to intracellular proteins is dynamically and finely regulated by the O-GlcNAc Transferase (OGT) and the O-GlcNAcase (OGA). It is now established that O-GlcNAcylation participates in many features of cancer cells including a high rate of cell growth, invasion, and metastasis but little is known about its impact on the response to therapies. The purpose of this review is to highlight the role of O-GlcNAc protein modification in cancer resistance to therapies. We summarize the current knowledge about the crosstalk between O-GlcNAcylation and molecular mechanisms underlying tumor sensitivity/resistance to targeted therapies, chemotherapies, immunotherapy, and radiotherapy. We also discuss potential benefits and strategies of targeting O-GlcNAcylation to overcome cancer resistance.

A new biomarker to enhance the radiosensitivity of hepatocellular cancer: miRNAs

Aims: This review summarizes findings regarding miRNAs that modulate radiation in hepatocellular carcinoma (HCC) and evaluates their potential clinical therapeutic uses. Materials & methods: We searched the relevant English-language medical databases for papers on miRNAs and radiation therapy for tumors to identify miRNAs that are linked with radiosensitivity and radioresistance, focusing on those associated with HCC radiation. Results: There were 88 papers assessed for miRNAs associated with tumor radiation, 56 of which dealt with radiosensitization, 21 with radioresistance and 11 with radiosensitization for HCC. Conclusion: Further work in this area would enable future evaluation of radiation responses and the potential use of miRNAs as therapeutic agents in HCC patients.

DNA Damage Repair and Current Therapeutic Approaches in Gastric Cancer: A Comprehensive Review

DNA in cells is frequently damaged by endogenous and exogenous agents. However, comprehensive mechanisms to combat and repair DNA damage have evolved to ensure genomic stability and integrity. Improper DNA damage repair may result in various diseases, including some types of tumors and autoimmune diseases. Therefore, DNA damage repair mechanisms have been proposed as novel antitumor drug targets. To date, numerous drugs targeting DNA damage mechanisms have been developed. For example, PARP inhibitors that elicit synthetic lethality are widely used in individualized cancer therapies. In this review, we describe the latent DNA damage repair mechanisms in gastric cancer, the types of DNA damage that can contribute to the development of gastric cancer, and new therapeutic approaches for gastric cancer that target DNA damage repair pathways.

Ionizing Radiation-Induced Ferroptosis Based on Nanomaterials

Ferroptosis is an iron-dependent form of regulated cell death (RCD), that is associated with peroxidative damage to cellular membranes. A promising therapeutic method is to target ferroptosis. Nanomaterial-induced ferroptosis attracts enormous attention. Nevertheless, there are still certain shortcomings in ferroptosis, such as inadequate triggered immunogenic cell death to suit clinical demands. Various investigations have indicated that ionizing radiation (IR) can further induce ferroptosis. Consequently, it is a potential strategy for cancer therapy that combines nanomaterials and IR to induce ferroptosis. Initially, we discuss various ferroptosis inducers based on nanomaterials in this review. Furthermore, mechanisms of IR-induced ferroptosis are briefly introduced. Ultimately, we assess the feasibility of combining nanomaterials with IR to induce ferroptosis, paving the way for future research.

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.

Functional Immune Cell-Derived Exosomes Engineered for the Trilogy of Radiotherapy Sensitization

The limited efficacy of radiotherapy leads to radio-resistance and high rates of tumor recurrence and metastasis, which is caused by tumor hypoxia, rapid DNA damage repair, and especially the suppressive immune microenvironment of tumor. Lots of immune cell-derived exosomes can regulate antitumor immunity, but their application in enhancing radiotherapy is rarely studied. Herein, as a model of concept, M1 macrophage-derived exosomes (M1Exos) is engineered as effective radiotherapy sensitizers, realizing the trilogy of radiotherapy sensitization: 1) M1Exos is engineered to express catalases on the inside of membrane, which can effectively relieve tumor hypoxia, and enhance DNA damage. 2) The DNA damage repair inhibitor is loaded in M1Exos to effectively inhibit DNA damage repair. 3) M1Exos can polarize M2 macrophages into M1 phenotypes, and the anti-PD-L1 nanobody engineered on the outside of M1Exos can relieve the immunosuppression of T cells, both ultimately leading to the remodeling of the tumor suppressive microenvironment. The trilogy of radiotherapy sensitization achieves excellent antitumor efficacy, exhibiting the good utility of engineering immune cell-derived exosomes as radiotherapy sensitizers, inspiring the future efforts to explore different kinds of immune cell-derived exosomes for enhanced radiotherapy.

Radiotherapy combined with immunotherapy: the dawn of cancer treatment

Radiotherapy (RT) is delivered for purposes of local control, but can also exert systemic effect on remote and non-irradiated tumor deposits, which is called abscopal effect. The view of RT as a simple local treatment has dramatically changed in recent years, and it is now widely accepted that RT can provoke a systemic immune response which gives a strong rationale for the combination of RT and immunotherapy (iRT). Nevertheless, several points remain to be addressed such as the interaction of RT and immune system, the identification of the best schedules for combination with immunotherapy (IO), the expansion of abscopal effect and the mechanism to amplify iRT. To answer these crucial questions, we roundly summarize underlying rationale showing the whole immune landscape in RT and clinical trials to attempt to identify the best schedules of iRT. In consideration of the rarity of abscopal effect, we propose that the occurrence of abscopal effect induced by radiation can be promoted to 100% in view of molecular and genetic level. Furthermore, the “radscopal effect” which refers to using low-dose radiation to reprogram the tumor microenvironment may amplify the occurrence of abscopal effect and overcome the resistance of iRT. Taken together, RT could be regarded as a trigger of systemic antitumor immune response, and with the help of IO can be used as a radical and systemic treatment and be added into current standard regimen of patients with metastatic cancer.

1,4-Naphthoquinone (CNN1) Induces Apoptosis through DNA Damage and Promotes Upregulation of H2AFX in Leukemia Multidrug Resistant Cell Line

The multidrug resistance (MDR) phenotype is one of the major obstacles in the treatment of chronic myeloid leukemia (CML) in advantage stages such as blast crisis. In this scenario, more patients develop resistance mechanisms during the course of the disease, making tyrosine kinase inhibitors (TKIs) target therapies ineffective. Therefore, the aim of the study was to examine the pharmacological role of CNN1, a para-naphthoquinone, in a leukemia multidrug resistant cell line. First, the in vitro cytotoxic activity of Imatinib Mesylate (IM) in K-562 and FEPS cell lines was evaluated. Subsequently, membrane integrity and mitochondrial membrane potential assays were performed to assess the cytotoxic effects of CNN1 in K-562 and FEPS cell lines, followed by cell cycle, alkaline comet assay and annexin V-Alexa Fluor® 488/propidium iodide assays (Annexin/PI) using flow cytometry. RT-qPCR was used to evaluate the H2AFX gene expression. The results demonstrate that CNN1 was able to induce apoptosis, cell membrane rupture and mitochondrial membrane depolarization in leukemia cell lines. In addition, CNN1 also induced genotoxic effects and caused DNA fragmentation, cell cycle arrest at the G2/M phase in leukemia cells. No genotoxicity was observed on peripheral blood mononuclear cells (PBMC). Additionally, CNN1 increased mRNA levels of H2AFX. Therefore, CNN1 presented anticancer properties against leukemia multidrug resistant cell line being a potential anticancer agent for the treatment of resistant CML.

Nanodelivery Systems Delivering Hypoxia-Inducible Factor-1 Alpha Short Interfering RNA and Antisense Oligonucleotide for Cancer Treatment

Hypoxia-inducible factor (HIF), which plays a crucial role in oxygen homeostasis, contributes to immunosuppression, tumor angiogenesis, multidrug resistance, photodynamic therapy resistance, and metastasis. HIF as a therapeutic target has attracted scientists’ strong academic research interests. Short interfering RNA (siRNA) and antisense oligonucleotide (ASO) are the more promising and broadly utilized methods for oligonucleotide-based therapy. Their physicochemical characteristics such as hydrophilicity, negative charge, and high molecular weight make them impossible to cross the cell membrane. Moreover, siRNA and ASO are subjected to a rapid deterioration in circulation and cannot translocate into nuclear. Delivery of siRNA and ASO to specific gene targets should be realized without off-target gene silencing and affecting the healthy cells. Nanoparticles as vectors for delivery of siRNA and ASO possess great advantages and flourish in academic research. In this review, we summarized and analyzed regulation mechanisms of HIF under hypoxia, the significant role of HIF in promoting tumor progression, and recent academic research on nanoparticle-based delivery of HIF siRNA and ASO for cancer immunotherapy, antiangiogenesis, reversal of multidrug resistance and radioresistance, potentiating photodynamic therapy, inhibiting tumor metastasis and proliferation, and enhancing apoptosis are reviewed in this thesis. Furthermore, we hope to provide some rewarding suggestions and enlightenments for targeting HIF gene therapy.

LncRNA CTBP1-DT-encoded microprotein DDUP sustains DNA damage response signalling to trigger dual DNA repair mechanisms

Sustaining DNA damage response (DDR) signalling via retention of DDR factors at damaged sites is important for transmitting damage-sensing and repair signals. Herein, we found that DNA damage provoked the association of ribosomes with IRES region in lncRNA CTBP1-DT, which overcame the negative effect of upstream open reading frames (uORFs), and elicited the novel microprotein DNA damage-upregulated protein (DDUP) translation via a cap-independent translation mechanism. Activated ATR kinase-mediated phosphorylation of DDUP induced a drastic 'dense-to-loose' conformational change, which sustained the RAD18/RAD51C and RAD18/PCNA complex at damaged sites and initiated RAD51C-mediated homologous recombination and PCNA-mediated post-replication repair mechanisms. Importantly, treatment with ATR inhibitor abolished the effect of DDUP on chromatin retention of RAD51C and PCNA, thereby leading to hypersensitivity of cancer cells to DNA-damaging chemotherapeutics. Taken together, our results uncover a plausible mechanism underlying the DDR sustaining and might represent an attractive therapeutic strategy in improvement of DNA damage-based anticancer therapies.

Specific Targeting of Antiapoptotic Bcl-2 Proteins as a Radiosensitizing Approach in Solid Tumors

Avoidance of therapy-induced apoptosis is a hallmark of acquired resistance towards radiotherapy. Thus, breaking resistance still challenges modern cancer therapy. The Bcl-2 protein family is known for its regulatory role in apoptosis signaling, making Bcl-2, Mcl-1 and Bcl-x_L promising targets. This study evaluates the effects of highly specific inhibitors for Bcl-x_L (WEHI-539), Bcl-2 (ABT-199) and Mcl-1 (S63845) as radiosensitizers. Covering a broad spectrum of solid tumors, Non-Small-Cell Lung Cancer (NSCLC), Head and Neck Squamous Cell Carcinoma (HNSCC) and synovial sarcoma cell lines were exposed to fractionated radiation as standard therapy with or without Bcl-2 protein inhibition. Protein expression was detected by Western blot and cell death was assessed by flow cytometry measuring apoptosis. In contrast to NSCLC, a high level of Bcl-x_L and its upregulation during radiotherapy indicated radioresistance in HNSCC and synovial sarcoma. Radioresistant cell lines across all entities benefited synergistically from combined therapy with Bcl-x_L inhibition and fractionated radiation. In NSCLC cell lines, Mcl-1 inhibition significantly augmented radiotherapy independent of the expression level. Our data suggest that among antiapoptotic Bcl-2 proteins, targeting Bcl-x_L may break resistance to radiation in HNSCC, synovial sarcoma and NSCLC in vitro. In NSCLC, Mcl-1 might be a promising target that needs further investigation.

The DDR-related gene signature with cell cycle checkpoint function predicts prognosis, immune activity, and chemoradiotherapy response in lung adenocarcinoma

BACKGROUND

As a DNA surveillance mechanism, cell cycle checkpoint has recently been discovered to be closely associated with lung adenocarcinoma (LUAD) prognosis. It is also an essential link in the process of DNA damage repair (DDR) that confers resistance to radiotherapy. Whether genes that have both functions play a more crucial role in LUAD prognosis remains unclear.

METHODS

In this study, DDR-related genes with cell cycle checkpoint function (DCGs) were selected to investigate their effects on the prognosis of LUAD. The TCGA-LUAD cohort and two GEO external validation cohorts (GSE31210 and GSE42171) were performed to construct a prognosis model based on the least absolute shrinkage and selection operator (LASSO) regression. Patients were divided into high-risk and low-risk groups based on the model. Subsequently, the multivariate COX regression was used to construct a prognostic nomogram. The ssGSEA, CIBERSORT algorithm, TIMER tool, CMap database, and IC50 of chemotherapeutic agents were used to analyze immune activity and responsiveness to chemoradiotherapy.

RESULTS

4 DCGs were selected as prognostic signatures, and patients in the high-risk group had a lower overall survival (OS). The lower infiltration levels of immune cells and the higher expression levels of immune checkpoints appeared in the high-risk group. The damage repair pathways were upregulated, and chemotherapeutic agent sensitivity was poor in the high-risk group.

CONCLUSIONS

The 4-DCGs signature prognosis model we constructed could predict the survival rate, immune activity, and chemoradiotherapy responsiveness of LUAD patients.

Downregulation of annexin A3 promotes ionizing radiation-induced EGFR activation and nuclear translocation and confers radioresistance in nasopharyngeal carcinoma

Radioresistance currently poses a significant challenge to successful disease control of nasopharyngeal carcinoma (NPC). We previously uncovered that annexin A3 (ANXA3), a calcium-dependent phospholipid binding protein, is underexpressed in radioresistant NPC cells and mouse xenografts. This study aims to further unravel the mechanistic basis underlying ANXA3-mediated radioresistance in NPC. We show that either innate ANXA3 downregulation or short hairpin RNA(shRNA)-based knockdown of ANXA3 confers resistance to ionizing radiation (IR) in NPC both in vitro and in mouse xenograft models in vivo, whereas radiosensitization was observed when ANXA3 was ectopically expressed. Mechanistically, ANXA3 knockdown dramatically enhances IR-induced epidermal growth factor receptor (EGFR) phosphorylation and nuclear translocation, leading to increased post-IR phosphorylation of DNA-dependent protein kinase catalytic subunit (DNA-PKcs) concomitant with markedly accelerated DNA DSB repair. In addition, pretreatment with cetuximab efficiently abrogated the radioresistant phenotype of ANXA3-low cells as well as the ANXA3 knockdown-induced post-IR EGFR nuclear accumulation, suggesting that EGFR is an essential mediator for ANXA3 depletion-mediated radioprotection in NPC. Collectively, this work reveals for the first time a critical role of ANXA3 in radiation survival and DNA repair mechanism of NPC and provides mechanistic evidence to support ANXA3 as a potential therapeutic target to improve radiocurability for NPC.

A Non-Cell-Autonomous Mode of DNA Damage Response in Soma of Caenorhabditis elegans

Life has evolved a mechanism called DNA damage response (DDR) to sense, signal and remove/repair DNA damage, and its deficiency and dysfunction usually lead to genomic instability and development of cancer. The signaling mode of the DDR has been believed to be of cell-autonomy. However, the paradigm is being shifted with in-depth research into model organism Caenorhabditis elegans. Here, we mainly investigate the effect of DDR activation on the radiosensitivity of vulva of C. elegans, and first found that the vulval radiosensitivity is mainly regulated by somatic DDR, rather than the DDR of germline. Subsequently, the worm lines with pharynx-specific rescue of DDR were constructed, and it is shown that the 9-1-1-ATR and MRN-ATM cascades in pharynx restore approximately 90% and 70% of vulval radiosensitivity, respectively, through distantly regulating the NHEJ repair of vulval cells. The results suggest that the signaling cascade of DDR might also operate in a non-cell autonomous mode. To further explore the underlying regulatory mechanisms, the cpr-4 mutated gene is introduced into the DDR-rescued worms, and CPR-4, a cysteine protease cathepsin B, is confirmed to mediate the inter-tissue and inter-individual regulation of DDR as a signaling molecule downstream of 9-1-1-ATR. Our findings throw some light on the regulation of DNA repair in soma of C. elegans, and might also provide new cues for cancer prevention and treatment.

The Influence of Different γ-Irradiation Patterns on Factors that May Affect Cell Cycle Progression in Male Rats

Most studies of the biological effects of ionizing radiation have been done on a single acute dose, while clinically and environmentally exposures occur under chronic/repetitive conditions. It is important to study effects of different patterns of ionizing radiation. In this study, a rat model was used to compare the effects of repetitive and acute exposure. Groups: (I) control, (II, III) were exposed to fractionated doses (1.5 GyX4) and (2 GyX4), respectively/24h interval, and (IV, V) were exposed to 6 Gy and 8 Gy of whole-body gamma irradiation, respectively. The gene expression of MAPT and tau phosphorylation increased in all irradiated groups but the gene expression of PKN not affected. TGFβ% increased at dose of 2 GyX4 only. In addition, the cell cycle was arrested in S phase. Micronucleus (MN) increased and cell proliferation decreased. In conclusion, the dose and pattern of ionizing radiation do not affect the MAPT and PKN gene expression, but TGF-β, p-tau, MN assay and cell proliferation are significantly affected. The dose of 2 GyX4 showed distinctive effect. Repetitive exposure may increase TGF-β%, which causes radio-resistance and, G2/M delay. Thus, the cell cycle could be regulated in a different manner according to the dose and pattern of irradiation.

Survival-related indicators ALOX12B and SPRR1A are associated with DNA damage repair and tumor microenvironment status in HPV 16-negative head and neck squamous cell carcinoma patients

OBJECTIVES

To investigate prognostic-related gene signature based on DNA damage repair and tumor microenvironment statue in human papillomavirus 16 negative (HPV16-) head and neck squamous cell carcinoma (HNSCC).

METHODS

For the RNA-sequence matrix in HPV16- HNSCC in the Cancer Genome Atlas (TCGA) cohort, the DNA damage response (DDR) and tumor microenvironment (TM) status of each patient sample was estimated by using the ssGSEA algorithm. Through bioinformatics analysis in DDR_high/TM_high (n = 311) and DDR_high/TM_low (n = 53) groups, a survival-related gene signature was selected in the TCGA cohort. Two independent external validation cohorts (GSE65858 (n = 210) and GSE41613 (n = 97)) with HPV16- HNSCC patients validated the gene signature. Correlations among the clinical-related hub differentially expressed genes (DEGs) and infiltrated immunocytes were explored with the TIMER2.0 server. Drug screening based on hub DEGs was performed using the CellMiner and GSCALite databases. The loss-of-function studies were used to evaluate the effect of screened survival-related gene on the motility of HPV- HNSCC cells in vitro.

RESULTS

A high DDR level (P = 0.025) and low TM score (P = 0.012) were independent risk factors for HPV16- HNSCC. Downregulated expression of ALOX12B or SPRR1A was associated with poor survival rate and advanced cancer stages. The pathway enrichment analysis showed the DDR_high/TM_low samples were enriched in glycosphingolipid biosynthesis-lacto and neolacto series, glutathione metabolism, platinum drug resistance, and ferroptosis pathways, while the DDR_high/TM_low samples were enriched in Th17 cell differentiation, Neutrophil extracellular trap formation, PD - L1 expression and PD - 1 checkpoint pathway in cancer. Notably, the expression of ALOX12B and SPRR1A were negatively correlated with cancer-associated fibroblasts (CAFs) infiltration and CAFs downstream effectors. Sensitivity to specific chemotherapy regimens can be derived from gene expressions. In addition, ALOX12B and SPRR1A expression was associated with the mRNA expression of insulin like growth factor 1 receptor (IGF1R), AKT serine/threonine kinase 1 (AKT1), mammalian target of rapamycin (MTOR), and eukaryotic translation initiation factor 4E binding protein 1 (EIF4EBP1) in HPV negative HNSCC. Down-regulation of ALOX12B promoted HPV- HNSCC cells migration and invasion in vitro.

CONCLUSIONS

ALOX12B and SPRR1A served as a gene signature for overall survival in HPV16- HNSCC patients, and correlated with the amount of infiltrated CAFs. The specific drug pattern was determined by the gene signature.

Chronically Radiation-Exposed Survivor Glioblastoma Cells Display Poor Response to Chk1 Inhibition under Hypoxia

Glioblastoma is the most malignant primary brain tumor, and a cornerstone in its treatment is radiotherapy. However, tumor cells surviving after irradiation indicates treatment failure; therefore, better understanding of the mechanisms regulating radiotherapy response is of utmost importance. In this study, we generated clinically relevant irradiation-exposed models by applying fractionated radiotherapy over a long time and selecting irradiation-survivor (IR-Surv) glioblastoma cells. We examined the transcriptomic alterations, cell cycle and growth rate changes and responses to secondary radiotherapy and DNA damage response (DDR) modulators. Accordingly, IR-Surv cells exhibited slower growth and partly retained their ability to resist secondary irradiation. Concomitantly, IR-Surv cells upregulated the expression of DDR-related genes, such as CHK1, ATM, ATR, and MGMT, and had better DNA repair capacity. IR-Surv cells displayed downregulation of hypoxic signature and lower induction of hypoxia target genes, compared to naïve glioblastoma cells. Moreover, Chk1 inhibition alone or in combination with irradiation significantly reduced cell viability in both naïve and IR-Surv cells. However, IR-Surv cells’ response to Chk1 inhibition markedly decreased under hypoxic conditions. Taken together, we demonstrate the utility of combining DDR inhibitors and irradiation as a successful approach for both naïve and IR-Surv glioblastoma cells as long as cells are refrained from hypoxic conditions.

Radiotherapy-induced metabolic hallmarks in the tumor microenvironment

Radiation is frequently administered for cancer treatment, but resistance or remission remains common. Cancer cells alter their metabolism after radiotherapy to reduce its cytotoxic effects. The influence of altered cancer metabolism extends to the tumor microenvironment (TME), where components of the TME exchange metabolites to support tumor growth. Combining radiotherapy with metabolic targets in the TME can improve therapy response. We review the metabolic rewiring of cancer cells following radiotherapy and put these observations in the context of the TME to describe the metabolic hallmarks of radiotherapy in the TME.

High Levels of DEAH-Box Helicases Relate to Poor Prognosis and Reduction of DHX9 Improves Radiosensitivity of Hepatocellular Carcinoma

Background

Liver hepatocellular carcinoma (LIHC), one of the most common primary malignancies, exhibits high levels of molecular and clinical heterogeneity. Increasing evidence has confirmed the important roles of some RNA helicase families in tumor development, but the function of the DEAH-box RNA helicase family in LIHC therapeutic strategies has not yet been clarified.

Methods

The LIHC dataset was downloaded from The Cancer Genome Atlas (TCGA). Consensus clustering was applied to group the patients. Least absolute shrinkage and selection operator Cox regression and univariate and multivariate Cox regression were used to develop and validate a prognostic risk model. The Tumor Immune Estimation Resource and Tumor Immune Single Cell Hub databases were used to explore the role of DEAH-box RNA helicases in LIHC immunotherapy. In vitro experiments were performed to investigate the role of DHX9 in LIHC radiosensitivity.

Results

Twelve survival-related DEAH-box RNA helicases were identified. High helicase expression levels were associated with a poor prognosis and clinical features. A prognostic model comprising six DEAH-box RNA helicases (DHX8, DHX9, DHX34, DHX35, DHX38, and DHX57) was constructed. The risk score of this model was found to be an independent prognostic indicator, and LIHC patients with different prognosis were distinguished by the model in the training and test cohorts. DNA damage repair pathways were also enriched in patients with high-risk scores. The six DEAH-box RNA helicases in the risk model were substantially related to innate immune cell infiltration and immune inhibitors. In vitro experiments showed that DHX9 knockdown improved radiosensitivity by increasing DNA damage.

Conclusion

The DEAH-box RNA helicase signature can be used as a reliable prognostic biomarker for LIHC. In addition, DHX9 may be a definitive indicator and therapeutic target in radiotherapy and immunotherapy for LIHC.

Combination of [177Lu]Lu-DOTA-TATE Targeted Radionuclide Therapy and Photothermal Therapy as a Promising Approach for Cancer Treatment: In Vivo Studies in a Human Xenograft Mouse Model

Peptide receptor radionuclide therapy (PRRT) relies on α- and β-emitting radionuclides bound to a peptide that commonly targets somatostatin receptors (SSTRs) for the localized killing of tumors through ionizing radiation. A Lutetium-177 (¹⁷⁷Lu)-based probe linked to the somatostatin analog octreotate ([¹⁷⁷Lu]Lu-DOTA-TATE) is approved for the treatment of certain SSTR-expressing tumors and has been shown to improve survival. However, a limiting factor of PRRT is the potential toxicity derived from the high doses needed to kill the tumor. This could be circumvented by combining PRRT with other treatments for an enhanced anti-tumor effect. Photothermal therapy (PTT) relies on nanoparticle-induced hyperthermia for cancer treatment and could be a useful add-on to PRRT. Here, we investigate a strategy combining [¹⁷⁷Lu]Lu-DOTA-TATE PRRT and nanoshell (NS)-based PTT for the treatment of SSTR-expressing small-cell lung tumors in mice. Our results showed that the combination treatment improved survival compared to PRRT alone, but only when PTT was performed one day after [¹⁷⁷Lu]Lu-DOTA-TATE injection (one of the timepoints examined), showcasing the effect of treatment timing in relation to outcome. Furthermore, the combination treatment was well-tolerated in the mice. This indicates that strategies involving NS-based PTT as an add-on to PRRT could be promising and should be investigated further.

PVP-Modified Multifunctional Bi2WO6 Nanosheets for Enhanced CT Imaging and Cancer Radiotherapy

Malignant tumors are one of the main causes of human death. The clinical treatment of malignant tumors is usually surgery, chemotherapy, radiotherapy, and so forth. Radiotherapy, as a traditional and effective treatment method for cancer, is widely used in clinical practice, but the radiation resistance of tumor cells and the toxic side effects to normal cells are still the Achilles heel of radiotherapy. Multifunctional inorganic high-atom nanomaterials are expected to enhance the effect of tumor radiotherapy. Tungsten and bismuth, which contain elements with high atomic coefficients, have strong X-ray energy attenuation capability. We synthesized Bi₂WO₆ nanosheets (NSs) using a hydrothermal synthesis method and modified polyvinylpyrrolidone (PVP) on their surface to make them more stable. PVP-Bi₂WO₆ NSs have a variety of effects after absorbing X-rays (such as the photoelectric effect and Compton effect) and release a variety of particles such as photoelectrons, Compton electrons, auger electrons, and so forth, which can react with organic molecules or water in cells, generate a large number of free radicals, and promote cell apoptosis, thereby improving the effect of radiotherapy. We show through γ-H2AX and DCFH-DA probe analysis experiments that PVP-Bi₂WO₆ NSs can effectively increase cell DNA damage and reactive oxygen species formation under X-ray irradiation. Clone formation analysis showed that PVP-Bi₂WO₆ NSs can effectively suppress cell colony formation under X-ray irradiation. These versatile functions endow PVP-Bi₂WO₆ NSs with enhanced radiotherapy efficacy in animal models. In addition, PVP-Bi₂WO₆ NSs can also be used as contrast agents for X-ray computed tomography (CT) imaging with obvious effects. Therefore, PVP-Bi₂WO₆ NSs can be used as CT imaging contrast agents and tumor radiotherapy sensitizers and have potential medical applications.

Immune Landscape and Classification in Lung Adenocarcinoma Based on a Novel Cell Cycle Checkpoints Related Signature for Predicting Prognosis and Therapeutic Response

Lung adenocarcinoma (LUAD) is one of the most common malignancies with the highest mortality globally, and it has a poor prognosis. Cell cycle checkpoints play a central role in the entire system of monitoring cell cycle processes, by regulating the signalling pathway of the cell cycle. Cell cycle checkpoints related genes (CCCRGs) have potential utility in predicting survival, and response to immunotherapies and chemotherapies. To examine this, based on CCCRGs, we identified two lung adenocarcinoma subtypes, called cluster1 and cluster2, by consensus clustering. Enrichment analysis revealed significant discrepancies between the two subtypes in gene sets associated with cell cycle activation and tumor progression. In addition, based on Least Absolute Shrinkage and Selection Operator (LASSO) Cox regression, we have developed and validated a cell cycle checkpoints-related risk signature to predict prognosis, tumour immune microenvironment: (TIME), immunotherapy and chemotherapy responses for lung adenocarcinoma patients. Results from calibration plot, decision curve analysis (DCA), and time-dependent receiver operating characteristic curve (ROC) revealed that combining age, gender, pathological stages, and risk score in lung adenocarcinoma patients allowed for a more accurate and predictive nomogram. The area under curve for lung adenocarcinoma patients with 1-, 3-, 5-, and 10-year overall survival was: 0.74, 0.73, 0.75, and 0.81, respectively. Taken together, our proposed 4-CCCRG signature can serve as a clinically useful indicator to help predict patients outcomes, and could provide important guidance for immunotherapies and chemotherapies decision for lung adenocarcinoma patients.

Targeting thioredoxin reductase by micheliolide contributes to radiosensitizing and inducing apoptosis of HeLa cells

Inhibition of thioredoxin reductase (TrxR) is a crucial strategy for the discovery of antineoplastic drugs and radiosensitizers. As an anticancer candidate derived from Michelia, micheliolide (MCL) is converted readily from parthenolide (PTL), and has better stability and solubility than PTL. However, the anticancer mechanism of MCL has not been fully dissected. We present here for the first time that MCL-targeted inhibition of TrxR not only promotes oxidative stress-mediated HeLa cell apoptosis but also sensitizes ionizing radiation (IR) treatment. Further mechanistic studies demonstrate that MCL covalently binds to Sec at position 498 of TrxR to restrain the biological function of TrxR. It exhibits the inhibition of TrxR activity, enhancement of oxidized Trx, and sensitization of IR in the cellular environment, accompanied by the accumulation of reactive oxygen species (ROS) and the collapse of the intracellular redox balance. In addition, HeLa-shTrxR1 cells with knockdown of TrxR were more sensitive than the HeLa-shNT cells to either MCL-treated or IR-induced cytotoxicity, ROS, and apoptosis, suggesting that inhibition of TrxR by MCL is likely responsible for increased cytotoxicity and enhanced radiation response. These findings further establish the mechanistic understanding and preclinical data to support the further investigation of MCL's potential as a prospective radiosensitizer and cancer chemotherapeutic agent.

Central Nervous System Delivery of the Catalytic Subunit of DNA-Dependent Protein Kinase Inhibitor Peposertib as Radiosensitizer for Brain Metastases

Cytotoxic effects of chemotherapy and radiation therapy (RT) used for the treatment of brain metastases results from DNA damage within cancer cells. Cells rely on highly evolved DNA damage response (DDR) pathways to repair the damage caused by these treatments. Inhibiting these repair pathways can further sensitize cancer cells to chemotherapy and RT. The catalytic subunit of DNA-dependent protein kinase, in a complex with Ku80 and Ku70, is a pivotal regulator of the DDR, and peposertib is a potent inhibitor of this catalytic subunit. The characterization of central nervous system (CNS) distributional kinetics of peposertib is critical in establishing a therapeutic index in the setting of brain metastases. Our studies demonstrate that the delivery of peposertib is severely restricted into the CNS as opposed to peripheral organs, by active efflux at the blood-brain barrier (BBB). Peposertib has a low free fraction in the brain and spinal cord, further reducing the active concentration, and distributes to the same degree within different anatomic regions of the brain. However, peposertib is heterogeneously distributed within the metastatic tumor, where its concentration is highest within the tumor core (with disrupted BBB) and substantially lower within the invasive tumor rim (with a relatively intact BBB) and surrounding normal brain. These findings are critical in guiding the potential clinical deployment of peposertib as a radiosensitizing agent for the safe and effective treatment of brain metastases. SIGNIFICANCE STATEMENT: Effective radiosensitization of brain metastases while avoiding toxicity to the surrounding brain is critical in the development of novel radiosensitizers. The central nervous system distribution of peposertib, a potent catalytic subunit of DNA-dependent protein kinase inhibitor, is restricted by active efflux in the normal blood-brain barrier (BBB) but can reach significant concentrations in the tumor core. This finding suggests that peposertib may be an effective radiosensitizer for intracranial tumors with an open BBB, while limited distribution into normal brain will decrease the risk of enhanced radiation injury.

Effective Radiosensitization of Bladder Cancer Cells by Pharmacological Inhibition of DNA-PK and ATR

This study aims at analyzing the impact of the pharmacological inhibition of DNA damage response (DDR) targets (DNA-PK and ATR) on radiosensitization of bladder cancer cell lines of different molecular/histological subtypes. Applying DNA-PK (AZD7648) and ATR (Ceralasertib) inhibitors on SCaBER, J82 and VMCUB-1 bladder cancer cell lines, we revealed sensitization upon ionizing radiation (IR), i.e., the IC50 for each drug shifted to a lower drug concentration with increased IR doses. In line with this, drug exposure retarded DNA repair after IR-induced DNA damage visualized by a neutral comet assay. Western blot analyses confirmed specific inhibition of targeted DDR pathways in the analyzed bladder cancer cell lines, i.e., drugs blocked DNA-PK phosphorylation at Ser2056 and the ATR downstream mediator CHK1 at Ser317. Interestingly, clonogenic survival assays indicated a cell-line-dependent synergism of combined DDR inhibition upon IR. Calculating combined index (CI) values, with and without IR, according to the Chou–Talalay method, confirmed drug- and IR-dose-specific synergistic CI values. Thus, we provide functional evidence that DNA-PK and ATR inhibitors specifically target corresponding DDR pathways retarding the DNA repair process at nano-molar concentrations. This, in turn, leads to a strong radiosensitizing effect and impairs the survival of bladder cancer cells.

Nanomaterials Based on Functional Polymers for Sensitizing Cancer Radiotherapy

Despite being the mainstay treatment for many types of cancer in clinic, radiotherapy is undertaking great challenges in overcoming a series of limitations. Radiosensitizers are promising agents capable of depositing irradiation energy and generating free radicals to enhance the radiosensitivity of tumor cells. Combining radiosensitizers with functional polymer-based nanomaterials holds great potential to improve biodistribution, circulation time, and stability in vivo. The derived polymeric nano-radiosensitizers can significantly improve the efficiency of tumor targeting and radiotherapy, and reduce the side effect to healthy tissues. In this review, we provide an overview of functional polymer-based nanomaterials for radiosensitization in recent years. Particular emphases are given to the action mechanisms, drug loading methods, targeting efficiencies, the impact on therapeutic effects and biocompatibility of various radiosensitizing polymers, which are classified as polymeric micelles, dendrimers, polymeric nanospheres, nanoscale coordination polymers, polymersomes, and nanogels. The challenges and outlooks of polymeric nano-radiosensitizers are also discussed. This article is protected by copyright. All rights reserved.

Nucleic Acid Sensing Pathways in DNA Repair Targeted Cancer Therapy

The repair of DNA damage is a complex process, which helps to maintain genome fidelity, and the ability of cancer cells to repair therapeutically DNA damage induced by clinical treatments will affect the therapeutic efficacy. In the past decade, great success has been achieved by targeting the DNA repair network in tumors. Recent studies suggest that DNA damage impacts cellular innate and adaptive immune responses through nucleic acid-sensing pathways, which play essential roles in the efficacy of DNA repair targeted therapy. In this review, we summarize the current understanding of the molecular mechanism of innate immune response triggered by DNA damage through nucleic acid-sensing pathways, including DNA sensing via the cyclic GMP-AMP synthase (cGAS), Toll-like receptor 9 (TLR9), absent in melanoma 2 (AIM2), DNA-dependent protein kinase (DNA-PK), and Mre11-Rad50-Nbs1 complex (MRN) complex, and RNA sensing via the TLR3/7/8 and retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs). Furthermore, we will focus on the recent developments in the impacts of nucleic acid-sensing pathways on the DNA damage response (DDR). Elucidating the DDR-immune response interplay will be critical to harness immunomodulatory effects to improve the efficacy of antitumor immunity therapeutic strategies and build future therapeutic approaches.

MRNIP condensates promote DNA double-strand break sensing and end resection

The rapid recognition of DNA double-strand breaks (DSBs) by the MRE11/RAD50/NBS1 (MRN) complex is critical for the initiation of DNA damage response and DSB end resection. Here, we show that MRN complex interacting protein (MRNIP) forms liquid-like condensates to promote homologous recombination-mediated DSB repair. The intrinsically disordered region is essential for MRNIP condensate formation. Mechanically, the MRN complex is compartmentalized and concentrated into MRNIP condensates in the nucleus. After DSB formation, MRNIP condensates move to the damaged DNA rapidly to accelerate the binding of DSB by the concentrated MRN complex, therefore inducing the autophosphorylation of ATM and subsequent activation of DNA damage response signaling. Meanwhile, MRNIP condensates-enhanced MRN complex loading further promotes DSB end resection. In addition, data from xenograft models and clinical samples confirm a correlation between MRNIP and radioresistance. Together, these results reveal an important role of MRNIP phase separation in DSB response and the MRN complex-mediated DSB end resection.

The MRN complex is a critical sensor and processor of DNA double-strand breaks (DSBs). Here, the authors show that MRNIP forms liquid-like condensates to accelerate the MRN-mediated sensing and end resection of DSB, thereby promoting DSB repair.

Different Mechanisms of DNA Radiosensitization by 8-Bromoadenosine and 2'-Deoxy-2'-fluorocytidine Observed on DNA Origami Nanoframe Supports

DNA origami nanoframes with two parallel DNA sequences are used to evaluate the effect of nucleoside substituents on radiation-induced DNA damage. Double strand breaks (DSB) of DNA are counted using atomic force microscopy (AFM), and total number of lesions is evaluated using real-time polymerase chain reaction (RT-PCR). Enhanced AT or GC content does not increase the number of DNA strand breaks. Incorporation of 8-bromoadenosine results in the highest enhancement in total number of lesions; however, the highest enhancement in DSB is observed for 2'-deoxy-2'-fluorocytidine, indicating different mechanisms of radiosensitization by nucleoside analogues with the halogen substituent on base or sugar moieties, respectively. "Bystander" effects are observed, when the number of DSB in a sequence is enhanced by a substituent in the parallel DNA sequence. The present approach eliminates limitations of previously developed methods and motivates detailed studies of poorly understood conformation or bystander effects in radiation induced damage to DNA.

DNA damage and metabolic mechanisms of cancer drug resistance

Cancer drug resistance is one of the main barriers to overcome to ensure durable treatment responses. While many pivotal advances have been made in first combination therapies, then targeted therapies, and now broadening out to immunomodulatory drugs or metabolic targeting compounds, drug resistance is still ultimately universally fatal. In this brief review, we will discuss different strategies that have been used to fight drug resistance from synthetic lethality to tumor microenvironment modulation, focusing on the DNA damage response and tumor metabolism both within tumor cells and their surrounding microenvironment. In this way, with a better understanding of both targetable mutations in combination with the metabolism, smarter drugs may be designed to combat cancer drug resistance.

The paradigm of drug resistance in cancer: an epigenetic perspective

Innate and acquired resistance towards the conventional therapeutic regimen imposes a significant challenge for the successful management of cancer for decades. In patients with advanced carcinomas, acquisition of drug resistance often leads to tumor recurrence and poor prognosis after the first therapeutic cycle. In this context, cancer stem cells (CSCs) are considered as the prime drivers of therapy resistance in cancer due to their 'non-targetable' nature. Drug resistance in cancer is immensely influenced by different properties of CSCs such as epithelial-to-mesenchymal transition (EMT), a profound expression of drug efflux pump genes, detoxification genes, quiescence, and evasion of apoptosis, has been highlighted in this review article. The crucial epigenetic alterations that are intricately associated with regulating different mechanisms of drug resistance, have been discussed thoroughly. Additionally, special attention is drawn towards the epigenetic mechanisms behind the interaction between the cancer cells and their microenvironment which assists in tumor progression and therapy resistance. Finally, we have provided a cumulative overview of the alternative treatment strategies and epigenome-modifying therapies that show the potential of sensitizing the resistant cells towards the conventional treatment strategies. Thus, this review summarizes the epigenetic and molecular background behind therapy resistance, the prime hindrance of present day anti-cancer therapies, and provides an account of the novel complementary epi-drug-based therapeutic strategies to combat drug resistance.

PTEN mutant non-small cell lung cancer require ATM to suppress pro-apoptotic signalling and evade radiotherapy

Background

Despite advances in treatment of patients with non-small cell lung cancer, carriers of certain genetic alterations are prone to failure. One such factor frequently mutated, is the tumor suppressor PTEN. These tumors are supposed to be more resistant to radiation, chemo- and immunotherapy.

Results

We demonstrate that loss of PTEN led to altered expression of transcriptional programs which directly regulate therapy resistance, resulting in establishment of radiation resistance. While PTEN-deficient tumor cells were not dependent on DNA-PK for IR resistance nor activated ATR during IR, they showed a significant dependence for the DNA damage kinase ATM. Pharmacologic inhibition of ATM, via KU-60019 and AZD1390 at non-toxic doses, restored and even synergized with IR in PTEN-deficient human and murine NSCLC cells as well in a multicellular organotypic ex vivo tumor model.

Conclusion

PTEN tumors are addicted to ATM to detect and repair radiation induced DNA damage. This creates an exploitable bottleneck. At least in cellulo and ex vivo we show that low concentration of ATM inhibitor is able to synergise with IR to treat PTEN-deficient tumors in genetically well-defined IR resistant lung cancer models.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00778-7.

DNA Damage Response Inhibitors in Cholangiocarcinoma: Current Progress and Perspectives

Cholangiocarcinoma (CCA) is a poorly treatable type of cancer and its incidence is dramatically increasing. The lack of understanding of the biology of this tumor has slowed down the identification of novel targets and the development of effective treatments. Based on next generation sequencing profiling, alterations in DNA damage response (DDR)-related genes are paving the way for DDR-targeting strategies in CCA. Based on the notion of synthetic lethality, several DDR-inhibitors (DDRi) have been developed with the aim of accumulating enough DNA damage to induce cell death in tumor cells. Observing that DDRi alone could be insufficient for clinical use in CCA patients, the combination of DNA-damaging regimens with targeted approaches has started to be considered, as evidenced by many emerging clinical trials. Hence, novel therapeutic strategies combining DDRi with patient-specific targeted drugs could be the next level for treating cholangiocarcinoma.

Beyond BRCA: The Emerging Significance of DNA Damage Response and Personalized Treatment in Pancreatic and Prostate Cancer Patients

The BRCA1/2 germline and/or somatic pathogenic variants (PVs) are key players in the hereditary predisposition and therapeutic response for breast, ovarian and, more recently, pancreatic and prostate cancers. Aberrations in other genes involved in homologous recombination and DNA damage response (DDR) pathways are being investigated as promising targets in ongoing clinical trials. However, DDR genes are not routinely tested worldwide. Due to heterogeneity in cohort selection and dissimilar sequencing approaches across studies, neither the burden of PVs in DDR genes nor the prevalence of PVs in genes in common among pancreatic and prostate cancer can be easily quantified. We aim to contextualize these genes, altered in both pancreatic and prostate cancers, in the DDR process, to summarize their hereditary and somatic burden in different studies and harness their deficiency for cancer treatments in the context of currently ongoing clinical trials. We conclude that the inclusion of DDR genes, other than BRCA1/2, shared by both cancers considerably increases the detection rate of potentially actionable variants, which are triplicated in pancreatic and almost doubled in prostate cancer. Thus, DDR alterations are suitable targets for drug development and to improve the outcome in both pancreatic and prostate cancer patients. Importantly, this will increase the detection of germline pathogenic variants, thereby patient referral to genetic counseling.

Direct ionizing radiation and bystander effect in mouse mesenchymal stem cells

Purpose: This study aimed to evaluate the radiation-induced direct and bystander (BYS) responses of mesenchymal stem cells (MSCs) and to characterize these cells radiobiologically.Methods and materials: MSCs were irradiated (IR) and parameters related to DNA damage and cellular signaling were verified in a dose range from 0.5 to 15 Gy; also a transwell insert co-culture system was used to study medium-mediated BYS effects.Results: The main effects on directly IR cells were seen at doses higher than 6 Gy: induction of cell death, cell cycle arrest, upregulation of p21, and alteration of redox status. Irrespective of a specific dose, induction of micronuclei formation, H2AX phosphorylation, and decreased Akt expression also occurred. Thus, mTOR expression, cell senescence, nitric oxide generation, and calcium levels, in general were not significantly modulated by radiation. Data from the linear-quadratic model showed a high alpha/beta ratio, which is consistent with a more exponential survival curve. BYS effects from the unirradiated MSCs placed into companion wells with the directly IR cells, were not observed.Conclusions: The results can be interpreted as a positive outcome, meaning that the radiation damage is restricted to the directed IR MSCs not leading to off-target cell responses.

Inflammation: A New Look at an Old Problem

Pro-inflammatory stress is inherent in any cells that are subject to damage or threat of damage. It is defined by a number of universal components, including oxidative stress, cellular response to DNA damage, unfolded protein response to mitochondrial and endoplasmic reticulum stress, changes in autophagy, inflammasome formation, non-coding RNA response, formation of an inducible network of signaling pathways, and epigenetic changes. The presence of an inducible receptor and secretory phenotype in many cells is the cause of tissue pro-inflammatory stress. The key phenomenon determining the occurrence of a classical inflammatory focus is the microvascular inflammatory response (exudation, leukocyte migration to the alteration zone). This same reaction at the systemic level leads to the development of life-critical systemic inflammation. From this standpoint, we can characterize the common mechanisms of pathologies that differ in their clinical appearance. The division of inflammation into alternative variants has deep evolutionary roots. Evolutionary aspects of inflammation are also described in the review. The aim of the review is to provide theoretical arguments for the need for an up-to-date theory of the relationship between key human pathological processes based on the integrative role of the molecular mechanisms of cellular and tissue pro-inflammatory stress.

Integrative analysis of therapy resistance and transcriptomic profiling data in glioblastoma cells identifies sensitization vulnerabilities for combined modality radiochemotherapy

Background

Inherent resistance to radio/chemotherapy is one of the major reasons for early recurrence, treatment failure, and dismal prognosis of glioblastoma. Thus, the identification of resistance driving regulators as prognostic and/or predictive markers as well as potential vulnerabilities for combined modality treatment approaches is of pivotal importance.

Methods

We performed an integrative analysis of treatment resistance and DNA damage response regulator expression in a panel of human glioblastoma cell lines. mRNA expression levels of 38 DNA damage response regulators were analyzed by qRT-PCR. Inherent resistance to radiotherapy (single-shot and fractionated mode) and/or temozolomide treatment was assessed by clonogenic survival assays. Resistance scores were extracted by dimensionality reduction and subjected to correlation analyses with the mRNA expression data. Top-hit candidates with positive correlation coefficients were validated by pharmacological inhibition in clonogenic survival assays and DNA repair analyses via residual γH2AX/53BP1-foci staining.

Results

Inherent resistance to single-shot and similarly also to fractionated radiotherapy showed strong positive correlations with mRNA expression levels of known vulnerabilities of GBM, including PARP1, NBN, and BLM, as well as ATR and LIG4—two so far underestimated targets. Inhibition of ATR by AZD-6738 resulted in robust and dose-dependent radiosensitization of glioblastoma cells, whereas LIG4 inhibition by L189 had no noticeable impact. Resistance against temozolomide showed strong positive correlation with mRNA expression levels of MGMT as to be expected. Interestingly, it also correlated with mRNA expression levels of ATM, suggesting a potential role of ATM in the context of temozolomide resistance in glioblastoma cells. ATM inhibition exhibited slight sensitization effects towards temozolomide treatment in MGMT low expressing glioblastoma cells, thus encouraging further characterization.

Conclusions

Here, we describe a systematic approach integrating clonogenic survival data with mRNA expression data of DNA damage response regulators in human glioblastoma cell lines to identify markers of inherent therapy resistance and potential vulnerabilities for targeted sensitization. Our results provide proof-of-concept for the feasibility of this approach, including its limitations. We consider this strategy to be adaptable to other cancer entities as well as other molecular data qualities, and its upscaling potential in terms of model systems and observational data levels deserves further investigation.

PCW-1001, a Novel Pyrazole Derivative, Exerts Antitumor and Radio-Sensitizing Activities in Breast Cancer

As pyrazole and its derivatives have a wide range of biological activities, including anticancer activity, the design of novel pyrazole derivatives has emerged as an important research field. This study describes a novel pyrazole derivative that exerts antitumor and radiosensitizing activities in breast cancer both in vitro and in vivo. We synthesized a novel pyrazole compound N,N-dimethyl-N’-(3-(1-(4-(trifluoromethyl)phenyl)-1H-pyrazol-4-yl)phenyl)azanesulfonamide (PCW-1001) and showed that it inhibited several oncogenic properties of breast cancer both in vitro and in vivo. PCW-1001 induced apoptosis in several breast cancer cell lines. Transcriptome analysis of PCW-1001-treated cells showed that it regulates genes involved in the DNA damage response, suggesting its potential use in radiotherapy. Indeed, PCW-1001 enhanced the radiation sensitivity of breast cancer cells by modulating the expression of DNA damage response genes. Therefore, our data describe a novel pyrazole compound, PCW-1001, with antitumor and radiosensitizer activities in breast cancer.

Carbon Ion Induces Cell Death and G2/M Arrest Through pRb/E2F1Chk2/Cdc2 Signaling Pathway in X-ray Resistant B16F10 Melanoma Cells

To explore the effect of high-LET carbon ion (C-ion) radiation on malignant melanoma, we systematically compared the radiobiological effects of C-ion with that of X-rays in B16F10 melanoma cells. Results showed that C-ion radiation statistically inhibited clonogenic survival capacity of B16F10 melanoma cells. The RBE was 3.7 at D10 levels, meaning 1.0 Gy C-ion should cause the same biological effect as ≥ 3.0 Gy X-rays. In addition, we also observed a stronger proliferation-inhibiting and higher ratio of cell apoptosis and necrosis in B16F10 cells treated with C-ion than X-rays. Moreover, C-ion radiation exhibited stronger and long-lasting G2/M arrest than X-rays. As an underlying mechanism, we speculated that C-ion radiation-induced G2/M block through activating pRb/E2F1/Chk2 pathway. With these results, we highlighted the potential of C-ion in treatment of cutaneous melanoma. Further, in vitro experiments as well as clinical trials are needed to further evaluate the effect of carbon ion radiotherapy in melanoma.