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

Understanding the Radiobiology of Vestibular Schwannomas to Overcome Radiation Resistance

Vestibular schwannomas (VS) are benign tumors arising from cranial nerve VIII that account for 8-10% of all intracranial tumors and are the most common tumors of the cerebellopontine angle. These tumors are typically managed with observation, radiation therapy, or microsurgical resection. Of the VS that are irradiated, there is a subset of tumors that are radioresistant and continue to grow; the mechanisms behind this phenomenon are not fully understood. In this review, the authors summarize how radiation causes cellular and DNA injury that can activate (1) checkpoints in the cell cycle to initiate cell cycle arrest and DNA repair and (2) key events that lead to cell death. In addition, we discuss the current knowledge of VS radiobiology and how it may contribute to clinical outcomes. A better understanding of VS radiobiology can help optimize existing treatment protocols and lead to new therapies to overcome radioresistance.

Cytotoxic T cells are able to efficiently eliminate cancer cells by additive cytotoxicity

Lethal hit delivery by cytotoxic T lymphocytes (CTL) towards B lymphoma cells occurs as a binary, "yes/no" process. In non-hematologic solid tumors, however, CTL often fail to kill target cells during 1:1 conjugation. Here we describe a mechanism of "additive cytotoxicity" by which time-dependent integration of sublethal damage events, delivered by multiple CTL transiting between individual tumor cells, mediates effective elimination. Reversible sublethal damage includes perforin-dependent membrane pore formation, nuclear envelope rupture and DNA damage. Statistical modeling reveals that 3 serial hits delivered with decay intervals below 50 min discriminate between tumor cell death or survival after recovery. In live melanoma lesions in vivo, sublethal multi-hit delivery is most effective in interstitial tissue where high CTL densities and swarming support frequent serial CTL-tumor cell encounters. This identifies CTL-mediated cytotoxicity by multi-hit delivery as an incremental and tunable process, whereby accelerating damage magnitude and frequency may improve immune efficacy.

Molecular mechanisms of chemo- and radiotherapy resistance and the potential implications for cancer treatment

Cancer is a leading cause of death worldwide. Surgery is the primary treatment approach for cancer, but the survival rate is very low due to the rapid progression of the disease and presence of local and distant metastasis at diagnosis. Adjuvant chemotherapy and radiotherapy are important components of the multidisciplinary approaches for cancer treatment. However, resistance to radiotherapy and chemotherapy may result in treatment failure or even cancer recurrence. Radioresistance in cancer is often caused by the repair response to radiation-induced DNA damage, cell cycle dysregulation, cancer stem cells (CSCs) resilience, and epithelial-mesenchymal transition (EMT). Understanding the molecular alterations that lead to radioresistance may provide new diagnostic markers and therapeutic targets to improve radiotherapy efficacy. Patients who develop resistance to chemotherapy drugs cannot benefit from the cytotoxicity induced by the prescribed drug and will likely have a poor outcome with these treatments. Chemotherapy often shows a low response rate due to various drug resistance mechanisms. This review focuses on the molecular mechanisms of radioresistance and chemoresistance in cancer and discusses recent developments in therapeutic strategies targeting chemoradiotherapy resistance to improve treatment outcomes.

VAV2 is required for DNA repair and implicated in cancer radiotherapy resistance

Radiotherapy remains the mainstay for treatment of various types of human cancer; however, the clinical efficacy is often limited by radioresistance, in which the underlying mechanism is largely unknown. Here, using esophageal squamous cell carcinoma (ESCC) as a model, we demonstrate that guanine nucleotide exchange factor 2 (VAV2), which is overexpressed in most human cancers, plays an important role in primary and secondary radioresistance. We have discovered for the first time that VAV2 is required for the Ku70/Ku80 complex formation and participates in non-homologous end joining repair of DNA damages caused by ionizing radiation. We show that VAV2 overexpression substantially upregulates signal transducer and activator of transcription 1 (STAT1) and the STAT1 inhibitor Fludarabine can significantly promote the sensitivity of radioresistant patient-derived ESCC xenografts in vivo in mice to radiotherapy. These results shed new light on the mechanism of cancer radioresistance, which may be important for improving clinical radiotherapy.

Anticarin β Inhibits Human Glioma Progression by Suppressing Cancer Stemness via STAT3

Glioma is the most common form of malignant brain cancer. It is very difficult to cure malignant glioma because of the presence of glioma stem cells, which are a barrier to cure, have high tumorigenesis, associated with drug resistance, and responsible for relapse by regulating stemness genes. In this study, our results demonstrated that anticarin β, a natural compound from Antiaris toxicaria, can effectively and selectively suppress proliferation and cause apoptosis in glioma cells, which has an IC₅₀ that is 100 times lower than that in mouse normal neural stem cells. Importantly, cell sphere formation assay and real time-quantitative analysis reveal that anticarin β inhibits cancer stemness by modulating related stemness gene expression. Additionally, anticarin β induces DNA damage to regulate the oncogene expression of signal transducer and activator of transcription 3 (STAT3), Akt, mitogen-activated protein kinases (MAPKs), and eventually leading to apoptosis. Furthermore, anticarin β effectively inhibits glioma growth and prolongs the lifts pan of tumor-bearing mice without systemic toxicity in the orthotopic xenograft mice model. These results suggest that anticarin β is a promising candidate inhibitor for malignant glioma.

Bioinformatics analysis of the prognostic value of NEK8 and its effects on immune cell infiltration in glioma

Glioma is the most common malignancy of the nervous system with high rates of recurrence and mortality, even after surgery. The 5‐year survival rate is only about 5%. NEK8 is involved in multiple biological processes in a variety of cancers; however, its role in glioma is still not clear. In the current study, we evaluated the prognostic value of NEK8, as well as its role in the pathogenesis of glioma. Using a bioinformatics approach and RNA‐seq data from public databases, we found that NEK8 expression is elevated in glioma tissues; we further verified this result by RT‐PCR, Western blotting and immunochemistry using clinical samples. Functional enrichment analyses of genes with correlated expression indicated that elevated NEK8 expression is associated with increased immune cell infiltration in glioma and may affect the tumour microenvironment via the regulation of DNA damage/repair. Survival analyses revealed that high levels of NEK8 are associated with a poorer prognosis; higher WHO grade, IDH status, 1p/19q codeletion, age and NEK8 were identified as an independent prognostic factor. These findings support the crucial role of NEK8 in the progression of glioma via effects on immune cell infiltration and suggest that it is a new prognostic biomarker.

First transcriptome profiling of D. melanogaster after development in a deep underground low radiation background laboratory

Natural background radiation is a permanent multicomponent factor. It has an influence on biological organisms, but effects of its deprivation still remain unclear. The aim of our work was to study for the first time responses of D. melanogaster to conditions of the Deep Underground Low-Background Laboratory DULB-4900 (BNO, INR, RAS, Russia) at the transcriptome level by RNA-seq profiling. Overall 77 transcripts demonstrated differential abundance between flies exposed to low and natural background radiation. Enriched biological process functional categories were established for all genes with differential expression. The results showed down-regulation of primary metabolic processes and up-regulation of both the immune system process and the response to stimuli. The comparative analysis of our data and publicly available transcriptome data on D. melanogaster exposed to low and high doses of ionizing radiation did not reveal common DEGs in them. We hypothesize that the observed changes in gene expression can be explained by the influence of the underground conditions in DULB-4900, in particular, by the lack of stimuli. Thus, our study challenges the validity of the LNT model for the region of background radiation doses below a certain level (~16.4 nGy h-1) and the presence of a dose threshold for D. melanogaster.

Multiplexed bioluminescence-mediated tracking of DNA double-strand break repairs in vitro and in vivo

The dynamics of DNA double-strand break (DSB) repairs including homology-directed repair and nonhomologous end joining play an important role in diseases and therapies. However, investigating DSB repair is typically a low-throughput and cross-sectional process, requiring disruption of cells and organisms for subsequent nuclease-, sequencing- or reporter-based assays. In this protocol, we provide instructions for establishing a bioluminescent repair reporter system using engineered Gaussia and Vargula luciferases for noninvasive tracking of homology-directed repair and nonhomologous end joining, respectively, induced by SceI meganuclease, SpCas9 or SpCas9 D10A nickase-mediated editing. We also describe complementation with orthogonal DSB repair assays and omics analyses to validate the reporter readouts. The bioluminescent repair reporter system provides longitudinal and rapid readout (~seconds per sample) to accurately and efficiently measure the efficacy of genome-editing tools and small-molecule modulators on DSB repair. This protocol takes ~2-4 weeks to establish, and as little as 2 h to complete the assay. The entire bioluminescent repair reporter procedure can be performed by one person with standard molecular biology expertise and equipment. However, orthogonal DNA repair assays would require a specialized facility that performs Sanger sequencing or next-generation sequencing.

Proteins from the DNA Damage Response: Regulation, Dysfunction, and Anticancer Strategies

Cells respond to genotoxic stress through a series of complex protein pathways called DNA damage response (DDR). These monitoring mechanisms ensure the maintenance and the transfer of a correct genome to daughter cells through a selection of DNA repair, cell cycle regulation, and programmed cell death processes. Canonical or non-canonical DDRs are highly organized and controlled to play crucial roles in genome stability and diversity. When altered or mutated, the proteins in these complex networks lead to many diseases that share common features, and to tumor formation. In recent years, technological advances have made it possible to benefit from the principles and mechanisms of DDR to target and eliminate cancer cells. These new types of treatments are adapted to the different types of tumor sensitivity and could benefit from a combination of therapies to ensure maximal efficiency.

Autophosphorylation and Self-Activation of DNA-Dependent Protein Kinase

The DNA-dependent protein kinase catalytic subunit (DNA-PKcs), a member of the phosphatidylinositol 3-kinase-related kinase family, phosphorylates serine and threonine residues of substrate proteins in the presence of the Ku complex and double-stranded DNA. Although it has been established that DNA-PKcs is involved in non-homologous end-joining, a DNA double-strand break repair pathway, the mechanisms underlying DNA-PKcs activation are not fully understood. Nevertheless, the findings of numerous in vitro and in vivo studies have indicated that DNA-PKcs contains two autophosphorylation clusters, PQR and ABCDE, as well as several autophosphorylation sites and conformational changes associated with autophosphorylation of DNA-PKcs are important for self-activation. Consistent with these features, an analysis of transgenic mice has shown that the phenotypes of DNA-PKcs autophosphorylation mutations are significantly different from those of DNA-PKcs kinase-dead mutations, thereby indicating the importance of DNA-PKcs autophosphorylation in differentiation and development. Furthermore, there has been notable progress in the high-resolution analysis of the conformation of DNA-PKcs, which has enabled us to gain a visual insight into the steps leading to DNA-PKcs activation. This review summarizes the current progress in the activation of DNA-PKcs, focusing in particular on autophosphorylation of this kinase.

DNA damage repair: historical perspectives, mechanistic pathways and clinical translation for targeted cancer therapy

Genomic instability is the hallmark of various cancers with the increasing accumulation of DNA damage. The application of radiotherapy and chemotherapy in cancer treatment is typically based on this property of cancers. However, the adverse effects including normal tissues injury are also accompanied by the radiotherapy and chemotherapy. Targeted cancer therapy has the potential to suppress cancer cells' DNA damage response through tailoring therapy to cancer patients lacking specific DNA damage response functions. Obviously, understanding the broader role of DNA damage repair in cancers has became a basic and attractive strategy for targeted cancer therapy, in particular, raising novel hypothesis or theory in this field on the basis of previous scientists' findings would be important for future promising druggable emerging targets. In this review, we first illustrate the timeline steps for the understanding the roles of DNA damage repair in the promotion of cancer and cancer therapy developed, then we summarize the mechanisms regarding DNA damage repair associated with targeted cancer therapy, highlighting the specific proteins behind targeting DNA damage repair that initiate functioning abnormally duo to extrinsic harm by environmental DNA damage factors, also, the DNA damage baseline drift leads to the harmful intrinsic targeted cancer therapy. In addition, clinical therapeutic drugs for DNA damage and repair including therapeutic effects, as well as the strategy and scheme of relative clinical trials were intensive discussed. Based on this background, we suggest two hypotheses, namely "environmental gear selection" to describe DNA damage repair pathway evolution, and "DNA damage baseline drift", which may play a magnified role in mediating repair during cancer treatment. This two new hypothesis would shed new light on targeted cancer therapy, provide a much better or more comprehensive holistic view and also promote the development of new research direction and new overcoming strategies for patients.

Intersection of Two Checkpoints: Could Inhibiting the DNA Damage Response Checkpoint Rescue Immune Checkpoint-Refractory Cancer?

Metastatic cancers resistant to immunotherapy require novel management strategies. DNA damage response (DDR) proteins, including ATR (ataxia telangiectasia and Rad3-related), ATM (ataxia telangiectasia mutated) and DNA-PK (DNA-dependent protein kinase), have been promising therapeutic targets for decades. Specific, potent DDR inhibitors (DDRi) recently entered clinical trials. Surprisingly, preclinical studies have now indicated that DDRi may stimulate anti-tumor immunity to augment immunotherapy. The mechanisms governing how DDRi could promote anti-tumor immunity are not well understood; however, early evidence suggests that they can potentiate immunogenic cell death to recruit and activate antigen-presenting cells to prime an adaptive immune response. Merkel cell carcinoma (MCC) is well suited to test these concepts. It is inherently immunogenic as ~50% of patients with advanced MCC persistently benefit from immunotherapy, making MCC one of the most responsive solid tumors. As is typical of neuroendocrine cancers, dysfunction of p53 and Rb with upregulation of Myc leads to the very rapid growth of MCC. This suggests high replication stress and susceptibility to DDRi and DNA-damaging agents. Indeed, MCC tumors are particularly radiosensitive. Given its inherent immunogenicity, cell cycle checkpoint deficiencies and sensitivity to DNA damage, MCC may be ideal for testing whether targeting the intersection of the DDR checkpoint and the immune checkpoint could help patients with immunotherapy-refractory cancers.

Insight into the Web of Stress Responses Triggered at Gene Expression Level by Porphyrin-PDT in HT29 Human Colon Carcinoma Cells

Photodynamic therapy (PDT), a highly targeted therapy with acceptable side effects, has emerged as a promising therapeutic option in oncologic pathology. One of the issues that needs to be addressed is related to the complex network of cellular responses developed by tumor cells in response to PDT. In this context, this study aims to characterize in vitro the stressors and the corresponding cellular responses triggered by PDT in the human colon carcinoma HT29 cell line, using a new asymmetric porphyrin derivative (P2.2) as a photosensitizer. Besides investigating the ability of P2.2-PDT to reduce the number of viable tumor cells at various P2.2 concentrations and fluences of the activating light, we assessed, using qRT-PCR, the expression levels of 84 genes critically involved in the stress response of PDT-treated cells. Results showed a fluence-dependent decrease of viable tumor cells at 24 h post-PDT, with few cells that seem to escape from PDT. We highlighted following P2.2-PDT the concomitant activation of particular cellular responses to oxidative stress, hypoxia, DNA damage and unfolded protein responses and inflammation. A web of inter-connected stressors was induced by P2.2-PDT, which underlies cell death but also elicits protective mechanisms that may delay tumor cell death or even defend these cells against the deleterious effects of PDT.

Genotoxic therapy and resistance mechanism in gliomas

Glioma is one of the most common and lethal brain tumors. Surgical resection followed by radiotherapy plus chemotherapy is the current standard of care for patients with glioma. The existence of resistance to genotoxic therapy, as well as the nature of tumor heterogeneity greatly limits the efficacy of glioma therapy. DNA damage repair pathways play essential roles in many aspects of glioma biology such as cancer progression, therapy resistance, and tumor relapse. O6-methylguanine-DNA methyltransferase (MGMT) repairs the cytotoxic DNA lesion generated by temozolomide (TMZ), considered as the main mechanism of drug resistance. In addition, mismatch repair, base excision repair, and homologous recombination DNA repair also play pivotal roles in treatment resistance as well. Furthermore, cellular mechanisms, such as cancer stem cells, evasion from apoptosis, and metabolic reprogramming, also contribute to TMZ resistance in gliomas. Investigations over the past two decades have revealed comprehensive mechanisms of glioma therapy resistance, which has led to the development of novel therapeutic strategies and targeting molecules.

Kinase Inhibitors of DNA-PK, ATM and ATR in Combination with Ionizing Radiation Can Increase Tumor Cell Death in HNSCC Cells While Sparing Normal Tissue Cells

(1) Kinase inhibitors (KI) targeting components of the DNA damage repair pathway are a promising new type of drug. Combining them with ionizing radiation therapy (IR), which is commonly used for treatment of head and neck tumors, could improve tumor control, but could also increase negative side effects on surrounding normal tissue. (2) The effect of KI of the DDR (ATMi: AZD0156; ATRi: VE-822, dual DNA-PKi/mTORi: CC-115) in combination with IR on HPV-positive and HPV-negative HNSCC and healthy skin cells was analyzed. Cell death and cell cycle arrest were determined using flow cytometry. Additionally, clonogenic survival and migration were analyzed. (3) Studied HNSCC cell lines reacted differently to DDRi. An increase in cell death for all of the malignant cells could be observed when combining IR and KI. Healthy fibroblasts were not affected by simultaneous treatment. Migration was partially impaired. Influence on the cell cycle varied between the cell lines and inhibitors; (4) In conclusion, a combination of DDRi with IR could be feasible for patients with HNSCC. Side effects on healthy cells are expected to be limited to normal radiation-induced response. Formation of metastases could be decreased because cell migration is impaired partially. The treatment outcome for HPV-negative tumors tends to be improved by combined treatment.

High Expression of Cancer-IgG Is Associated With Poor Prognosis and Radioresistance via PI3K/AKT/DNA-PKcs Pathway Regulation in Lung Adenocarcinoma

Background

Lung adenocarcinoma (LUAD) is the dominant type of lung neoplasms, and radiotherapy is its mainstay treatment, yet poor prognosis caused by radioresistance remains problematic. Cancer-derived immunoglobulin G (cancer-IgG) has been detected in multiple cancers and plays important roles in carcinogenesis. This study aimed to demonstrate that cancer-IgG is associated with poor prognosis of LUAD and to identify its role in radioresistance.

Methods

Cancer-IgG expression was detected by immunohistochemistry from 56 patients with stage III LUAD and by western blot and immunofluorescence in LUAD cell lines and in a human bronchial epithelial cell line. The effects of cancer-IgG silencing on the proliferation and apoptosis of PC9 and H292 cells were evaluated by plate cloning and apoptosis assay; the effects of cancer-IgG silencing on DNA damage repair ability and radiosensitivity were evaluated by colony-forming assay, γH2AX immunofluorescence, and neutral comet assay. Finally, we used the protein phosphorylation microarray and western blot to explore mechanisms involving cancer-IgG that increased radioresistance.

Results

Cancer-IgG is widely expressed in stage III LUAD, and the overall survival and disease-free survival of patients with positive expression are notably lower than those of patients with negative expression, indicating the associations between cancer-IgG and poor prognosis as well as radioresistance. The expression of cancer-IgG in the four LUAD cell lines was located mainly on the cell membrane and cytoplasm and not in the normal lung epithelial cell. Knockdown of cancer-IgG in PC9 and H292 cells resulted in increased apoptosis and negatively affected cancer cell proliferation. After irradiation, silencing of cancer-IgG showed a decrease in colonies as well as increases in the Olive tail moment and γH2AX foci in nucleus, indicating that the knockdown of cancer-IgG resulted in a decrease in the damage repair ability of DNA double-strand breaks in LUAD cells and an enhanced radiosensitivity. The expression of p-AKT, p-GSK3β, and p-DNA-PKcs decreased in the knockdown group after radiotherapy, suggesting that cancer-IgG could affect radiotherapy resistance by mediating double-strand breaks damage repair in LUAD cells through the PI3K/AKT/DNA-PKcs pathway.

Conclusions

This study revealed that cancer-IgG regulates PI3K/AKT/DNA-PKcs signaling pathways to affect radioresistance of LUAD and associated with poor prognosis.

Current Implications of microRNAs in Genome Stability and Stress Responses of Ovarian Cancer

Genomic alterations and aberrant DNA damage signaling are hallmarks of ovarian cancer (OC), the leading cause of mortality among gynecological cancers worldwide. Owing to the lack of specific symptoms and late-stage diagnosis, survival chances of patients are significantly reduced. Poly (ADP-ribose) polymerase (PARP) inhibitors and replication stress response inhibitors present attractive therapeutic strategies for OC. Recent research has focused on ovarian cancer-associated microRNAs (miRNAs) that play significant regulatory roles in various cellular processes. While miRNAs have been shown to participate in regulation of tumorigenesis and drug responses through modulating the DNA damage response (DDR), little is known about their potential influence on sensitivity to chemotherapy. The main objective of this review is to summarize recent findings on the utility of miRNAs as cancer biomarkers, in particular, ovarian cancer, and their regulation of DDR or modified replication stress response proteins. We further discuss the suppressive and promotional effects of various miRNAs on ovarian cancer and their participation in cell cycle disturbance, response to DNA damage, and therapeutic functions in multiple cancer types, with particular focus on ovarian cancer. Improved understanding of the mechanisms by which miRNAs regulate drug resistance should facilitate the development of effective combination therapies for ovarian cancer.

Challenges with Methods for Detecting and Studying the Transcription Factor Nuclear Factor Kappa B (NF-κB) in the Central Nervous System

The transcription factor nuclear factor kappa B (NF-κB) is highly expressed in almost all types of cells. NF-κB is involved in many complex biological processes, in particular in immunity. The activation of the NF-κB signaling pathways is also associated with cancer, diabetes, neurological disorders and even memory. Hence, NF-κB is a central factor for understanding not only fundamental biological presence but also pathogenesis, and has been the subject of intense study in these contexts. Under healthy physiological conditions, the NF-κB pathway promotes synapse growth and synaptic plasticity in neurons, while in glia, NF-κB signaling can promote pro-inflammatory responses to injury. In addition, NF-κB promotes the maintenance and maturation of B cells regulating gene expression in a majority of diverse signaling pathways. Given this, the protein plays a predominant role in activating the mammalian immune system, where NF-κB-regulated gene expression targets processes of inflammation and host defense. Thus, an understanding of the methodological issues around its detection for localization, quantification, and mechanistic insights should have a broad interest across the molecular neuroscience community. In this review, we summarize the available methods for the proper detection and analysis of NF-κB among various brain tissues, cell types, and subcellular compartments, using both qualitative and quantitative methods. We also summarize the flexibility and performance of these experimental methods for the detection of the protein, accurate quantification in different samples, and the experimental challenges in this regard, as well as suggestions to overcome common challenges.

G2/M Checkpoint Abrogation With Selective Inhibitors Results in Increased Chromatid Breaks and Radiosensitization of 82-6 hTERT and RPE Human Cells

While technological advances in radiation oncology have led to a more precise delivery of radiation dose and a decreased risk of side effects, there is still a need to better understand the mechanisms underlying DNA damage response (DDR) at the DNA and cytogenetic levels, and to overcome tumor resistance. To maintain genomic stability, cells have developed sophisticated signaling pathways enabling cell cycle arrest to facilitate DNA repair via the DDR-related kinases and their downstream targets, so that DNA damage or DNA replication stress induced by genotoxic therapies can be resolved. ATM, ATR, and Chk1 kinases are key mediators in DDR activation and crucial factors in treatment resistance. It is of importance, therefore, as an alternative to the conventional clonogenic assay, to establish a cytogenetic assay enabling reliable and time-efficient results in evaluating the potency of DDR inhibitors for radiosensitization. Toward this goal, the present study aims at the development and optimization of a chromosomal radiosensitivity assay using the DDR and G2-checkpoint inhibitors as a novel modification compared to the classical G2-assay. Also, it aims at investigating the strengths of this assay for rapid radiosensitivity assessments in cultured cells, and potentially, in tumor cells obtained from biopsies. Specifically, exponentially growing RPE and 82-6 hTERT human cells are irradiated during the G2/M-phase transition in the presence or absence of Caffeine, VE-821, and UCN-1 inhibitors of ATM/ATR, ATR, and Chk1, respectively, and the induced chromatid breaks are used to evaluate cell radiosensitivity and their potency for radiosensitization. The increased yield of chromatid breaks in the presence of DDR inhibitors, which underpins radiosensitization, is similar to that observed in cells from highly radiosensitive AT-patients, and is considered here as 100% radiosensitive internal control. The results highlight the potential of our modified G2-assay using VE-821 to evaluate cell radiosensitivity, the efficacy of DDR inhibitors in radiosensitization, and reinforce the concept that ATM, ATR, and Chk1 represent attractive anticancer drug targets in radiation oncology.

HPV Status and Individual Characteristics of Human Papillomavirus Infection as Predictors for Clinical Outcome of Locally Advanced Cervical Cancer

This study is aimed at searching for an informative predictor of the clinical outcome of cervical cancer (CC) patients. The study included 135 patients with locally advanced cervical cancer (FIGO stage II-III) associated with human papillomavirus (HPV) 16/18 types or negative status of HPV infection. Using logistic regression, we analyzed the influence of the treatment method, clinical and morphological characteristics, and the molecular genetic parameters of HPV on the disease free survival (DFS) of patients treated with radiotherapy or chemoradiotherapy. Multivariate analysis revealed three factors that have prognostic significance for DFS, i.e., HPV-related biomarker (HPV-negativity or HPV DNA integration into the cell genome) (OR = 9.67, p = 1.2 × 10^-4), stage of the disease (OR = 4.69, p = 0.001) and age (OR = 0.61, p = 0.025). The predictive model has a high statistical significance (p = 5.0 × 10^-8; Nagelkirk's R² = 0.336), as well as sensitivity (Se = 0.74) and specificity (Sp = 0.75). Thus, simultaneous accounting for the clinical and molecular genetic predictors (stage of the disease, patient age and HPV-related biomarker) makes it possible to effectively differentiate patients with prognostically favorable and unfavorable outcome of the disease.

MRE11 as a molecular signature and therapeutic target for cancer treatment with radiotherapy

MRE11, the core of the MRE11/RAD50/NBS1 complex, is one of key DNA damage response proteins. Increasing evidence suggests that its expression in cancer cells is critical to developing radioresistance; as such, MRE11 is an emerging marker for targeted radiosensitization strategies. Elevated MRE11 in tumor tissues has been associated with poor survival in patients undergoing radiotherapy, although in some cancer types, the opposite has been noted. The recent discovery of ionizing radiation-induced truncation of MRE11, which decreases its efficacy, may explain some of these paradoxical findings. The progress of research on the biological modulation of MRE11 expression is also discussed, with the potential application of small molecule or large molecule inhibitors of MRE11 for enhancing radiosensitivity. Current research has further highlighted both nuclease and non-nuclease activities of MRE11 in cancer cells treated with ionizing radiation, and differentiation between these is essential to verify the targeting effects of radiosensitizing agents. These updates clarify our understanding of how MRE11 expression may be utilized in future stratification of cancer patients for radiotherapy, and how it may be leveraged in shaping novel radiosensitization strategies.

The lipid peroxidation derived DNA adduct γ-OHPdG levels in paraneoplastic liver tissues predict postoperative outcomes of hepatoma

Chronic necroinflammation in liver induces lipid peroxidation and oxidative stress, which contributes to hepatocellular carcinoma (HCC) development. Gamma-hydroxy-1, N2-propanodeoxyguanosine (γ-OHPdG), a promutagenic DNA adduct, is derived from lipid peroxidation. Little is known about the clinical roles of γ-OHPdG in relationship to HCC progression. Here, we showed that γ-OHPdG levels were highly expressed in the cancerous HCC tissues (P = 0.020, compared to those in noncancerous parts). Postoperative outcome analysis revealed that higher γ-OHPdG expression in the paraneoplastic noncancerous tissues was independently associated with shorter distant metastasis-free survival (P = 0.020). In subgroup analysis, higher γ-OHPdG expression in the noncancerous tissues in hepatitis B related HCC subgroup was associated with shorter overall survival (P = 0.016) and distant metastasis-free survival (P = 0.006). However, in patient subgroups including non-cirrhosis, bilirubin < 1.2 mg/dL, alanine transaminase < 41 U/L, or aspartate transaminase < 31 U/L, higher γ-OHPdG expression in the cancerous tissues was associated with longer overall survival (P < 0.03 for all). In vitro experiments showed that cell viability was suppressed upon hydrogen peroxide treatment in liver cancer cell lines. In conclusion, lipid peroxidation derived marker, γ-OHPdG, in the paraneoplastic noncancerous and cancerous liver tissues predicted postoperative outcomes in HCC patients.

Inhibition of Crandell-Rees Feline Kidney cell proliferation by X-ray-induced senescence

Radioresistance and radiotoxicity have been reported following cancer treatments in felines. Optimizing radiation doses to induce cytotoxic effects to only cancer cells and not normal cells is critical in achieving effective radiation therapy; however, the mechanisms of radiation resistance, radiotoxicity, and DNA damage response (DDR) in feline cells have not yet been elucidated. A DNA double-strand break (DSB) is the most toxic type of DNA damage induced by X-rays and heavy ion beams used in treating cancers. Crandell-Rees Feline Kidney (CRFK) cells is one of the most widely used cat cells in life science research. Here, we report that DSB-triggered senescence induced by X-rays is important in inhibiting the proliferation of CRFK cells. We demonstrated through cell proliferation assay that X-rays at doses 2 Gy and 10 Gy are toxic to CRFK cells that irradiating CRFK cells inhibits their proliferation. In X-irradiated CRFK cells, a dose-dependent increase in DSB-triggered senescence was detected according to morphological changes and using senescence-associated β galactosidase staining assay. Moreover, our data indicated that in CRFK cells, the major DDR pathway, which involves the phosphorylation of H2AX at Ser139, was normally activated by ATM kinases. Our findings are useful in the understanding of X-rays-induced cellular senescence and in elucidating biological effects of radiation, e.g., toxicity, in feline cells. Furthermore, our findings suggest that the CRFK cell line is an excellent matrix for elucidating radioresistance and radiotoxicity in cat cells.

Inhibition of DNA damage response pathway using combination of DDR pathway inhibitors and radiation in treatment of acute lymphoblastic leukemia cells

An alarming increase in acute lymphoblastic leukemia cases among children and adults has attracted the attention of researchers to discover new therapeutic strategies with a better prognosis. In cancer cells, the DNA damage response (DDR) pathway elements have been recognized to protect tumor cells from various stresses and cause tumor progression; targeting these DDR members is an attractive strategy for treatment of cancers. The inhibition of the DDR pathway in cancer cells for the treatment of cancers has recently been introduced. Hence, effective treatment strategies are needed for this purpose. Chemotherapy in combination with radiotherapy is considered a potential therapeutic strategy for acute leukemia. This review aims to assess the synergistic effects of these inhibitors with irradiation for the treatment of leukemia.

Polybrominated diphenyl ethers quinone exhibits neurotoxicity by inducing DNA damage, cell cycle arrest, apoptosis and p53-driven adaptive response in microglia BV2 cells

Polybrominated diphenyl ethers (PBDEs) are world-wide used flame retardants before they were listed as Persistent Organic Pollutants (POPs) by the Stockholm Convention. Previously, our studies indicated that a quinone type of PBDE metabolite (PBDEQ) exposure was linked with neurotoxicity via excess free radical formation and oxidative stress. However, it is current unknown the effect of PBDEQ on genetic biomacromolecules DNA and corresponding biological consequences in neurological cells. Here, by employing phosphorylated histone H2AX in Serine 139 (γ-H2AX) and comet assay in microglia BV2 cells, our data suggested PBDEQ could triggered DNA damage. Furthermore, PBDEQ exposure led to the caspase 3-dependent cell apoptosis. Moreover, PBDEQ induced G2/M-phase cell arrest in a p53-dependent manner. Notably, p53 activation coordinated cell cycle progression, alleviated DNA damage and ultimately mitigated apoptosis in BV2 cells. Finally, antioxidant N-acetyl-l-cysteine (NAC) inhibited p53 activation upon PBDEQ exposure, and then ameliorated PBDEQ-induced DNA damage, cell cycle arrest and apoptosis, which illustrated that PBDEQ-induced DNA damage and p53 activation were mediated by reactive oxygen species (ROS). Together, the current findings unveil the fundamental toxicological mechanisms of PBDEQ, which propose a potential therapeutic strategy against the adverse effect caused by PBDE exposure.

Effect of Piperine in Combination with Gamma Radiation on A549 Cells

Background Lung cancer is a major constrain that increases mortality globally. Radiotherapy is one of the treatment modalities against lung cancer. A high dose of targeted radiation is required to achieve the treatment efficacy of cell killing. After radiotherapy, eventual tumor progression and therapy resistance are still a consequence of patient who undertakes nonsurgical radiation therapy. Piperine, a plant alkaloid, has been known to enhance the action of the anticancer drugs in various drug-resistant cancer cells. The aim of the current in vitro study was to study the effect of piperine on radiosensitizing property against A549 cells.

Methods In vitro radiosensitizing activity of piperine was elucidated on A549 cells using MTT (3-(4, 5-dimethylthiazol-2-yl)-25-diphenyltetrazolium bromide) assay. CompuSyn analysis was used to compute the combination index values to analyze the combinatory effect of piperine and radiation

Results and Conclusion We observed that piperine increased tumor cell killing in combination with the γ-radiation in vitro. However, further studies are warranted to understand the molecular mechanism of the radiosensitizing action of piperine.

In Vitro and In Vivo Comparison of 3,2-HOPO Versus Deferoxamine-Based Chelation of Zirconium-89 to the Antimesothelin Antibody Anetumab

Introduction: [²²⁷Th]Th-3,2-HOPO-MSLN-mAb, a mesothelin (MSLN)-targeted thorium-227 therapeutic conjugate, is currently in phase I clinical trial; however, direct PET imaging using this conjugate is technically challenging. Thus, using the same MSLN antibody, we synthesized 3,2-HOPO and deferoxamine (DFO)-based zirconium-89 antibody conjugates, [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb and [⁸⁹Zr]Zr-DFO-MSLN-mAb, respectively, and compared them in vitro and in vivo.

Methods: [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb and [⁸⁹Zr]Zr-DFO-MSLN-mAb were evaluated in vitro to determine binding affinity and immunoreactivity in HT29-MSLN and PDX (NCI-Meso16, NCI-Meso21) cells. For both the zirconium-89 conjugates, in vivo studies (biodistribution/imaging) were performed at days 1, 3, and 6, from which tissue uptake was determined.

Results: Both the conjugates demonstrated a low nanomolar binding affinity for MSLN and >95% immunoreactivity. In all the three tumor types, biodistribution of [⁸⁹Zr]Zr-DFO-MSLN-mAb resulted in higher tumor uptake(15.88-28-33%ID/g) at all time points compared with [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb(7–13.07%ID/g). [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb femur uptake was always higher than [⁸⁹Zr]Zr-DFO-MSLN-mAb, and imaging results concurred with the biodistribution studies.

Conclusions: Even though the conjugates exhibited a high binding affinity for MSLN, [⁸⁹Zr]Zr-DFO-MSLN-mAb showed a higher tumor and lower femur uptake than [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb. Nevertheless, [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb could be used to study organ distribution and lesion uptake with the caveat of detecting MSLN-positive bone lesions. Clinical trial (NCT03507452).

Veliparib Is an Effective Radiosensitizing Agent in a Preclinical Model of Medulloblastoma

Medulloblastoma is the most common malignant childhood brain tumor, and 5-year overall survival rates are as low as 40% depending on molecular subtype, with new therapies critically important. As radiotherapy and chemotherapy act through the induction of DNA damage, the sensitization of cancer cells through the inhibition of DNA damage repair pathways is a potential therapeutic strategy. The poly-(ADP-ribose) polymerase (PARP) inhibitor veliparib was assessed for its ability to augment the cellular response to radiation-induced DNA damage in human medulloblastoma cells. DNA repair following irradiation was assessed using the alkaline comet assay, with veliparib inhibiting the rate of DNA repair. Veliparib treatment also increased the number of γH2AX foci in cells treated with radiation, and analysis of downstream pathways indicated persistent activation of the DNA damage response pathway. Clonogenicity assays demonstrated that veliparib effectively inhibited the colony-forming capacity of medulloblastoma cells, both as a single agent and in combination with irradiation. These data were then validated in vivo using an orthotopic implant model of medulloblastoma. Mice harboring intracranial D425 medulloblastoma xenografts were treated with vehicle, veliparib, 18 Gy multifractionated craniospinal irradiation (CSI), or veliparib combined with 18 Gy CSI. Animals treated with combination therapy exhibited reduced tumor growth rates concomitant with increased intra-tumoral apoptosis observed by immunohistochemistry. Kaplan–Meier analyses revealed a statistically significant increase in survival with combination therapy compared to CSI alone. In summary, PARP inhibition enhanced radiation-induced cytotoxicity of medulloblastoma cells; thus, veliparib or other brain-penetrant PARP inhibitors are potential radiosensitizing agents for the treatment of medulloblastoma.

The Chemistry of Reactive Oxygen Species (ROS) Revisited: Outlining Their Role in Biological Macromolecules (DNA, Lipids and Proteins) and Induced Pathologies

Living species are continuously subjected to all extrinsic forms of reactive oxidants and others that are produced endogenously. There is extensive literature on the generation and effects of reactive oxygen species (ROS) in biological processes, both in terms of alteration and their role in cellular signaling and regulatory pathways. Cells produce ROS as a controlled physiological process, but increasing ROS becomes pathological and leads to oxidative stress and disease. The induction of oxidative stress is an imbalance between the production of radical species and the antioxidant defense systems, which can cause damage to cellular biomolecules, including lipids, proteins and DNA. Cellular and biochemical experiments have been complemented in various ways to explain the biological chemistry of ROS oxidants. However, it is often unclear how this translates into chemical reactions involving redox changes. This review addresses this question and includes a robust mechanistic explanation of the chemical reactions of ROS and oxidative stress.

TSL-1502, a glucuronide prodrug of a poly (ADP-ribose) polymerase (PARP) inhibitor, exhibits potent anti-tumor activity in preclinical models

Poly (ADP-ribose) polymerase (PARP) enzymes play an important role in the cellular response to DNA damage and the inhibition of PARP causes synthetic lethality in homologous recombination (HR)-deficient cancer. Multiple PARP inhibitors have been developed and have shown remarkable clinical benefits. However, treatment-related toxicities, especially the hematologic toxicities, are common and restrict the clinical applications of PARP inhibitors. In this study, we designed the first glucuronide prodrug of PARP inhibitor, TSL-1502, based on a novel and highly potent PARP inhibitor TSL-1502M. TSL-1502M exhibited promising inhibitory activity on PARP1/2, significantly induced DNA double strand breaks, G2/M arrest and apoptosis in HR-deficient cells, selectively inhibited the proliferation of HR-deficient cancer cells and sensitized both HR-deficient and HR-proficient cancer cells to conventional chemotherapy. Notably, TSL-1502M was superior to olaparib, the first-in-class PARP inhibitor, in all these processes. TSL-1502 had no inhibitory effects on PARP1/2 itself, but could selectively liberate the active drug TSL-1502M in tumor after administration in nude mice. Moreover, TSL-1502 elicited significant more potent inhibitory effects than olaparib in HR-deficient tumors, and sensitized chemotherapy in both HR-deficient and HR-proficient tumors. No severe toxicities were caused by TSL-1502 in this study. Based on the encouraging preclinical antitumor activity and the selective decomposition characteristic of TSL-1502, a clinical phase I study was initiated in China, and an Investigational New Drug (IND) was granted by the US FDA. TSL-1502 could represent a new potential therapeutic choice of PARP inhibitors.

Excision repair cross-complementing group 2 upregulation is a potential predictive biomarker for oral squamous cell carcinoma recurrence

Oral cancer is the fourth most common type of cancer among males in Taiwan, and the prognosis for patients with advanced-stage oral squamous cell carcinoma (OSCC) remains poor. The present study investigated the prognostic value of three DNA repair genes, namely excision repair cross-complementing group 1 (ERCC1), ERCC2 and X-ray repair cross-complementing group 1 (XRCC1) in OSCC. The protein expression levels of XRCC1, ERCC1 and ERCC2 in oral cell lines were analyzed via western blotting and immunohistochemistry using samples from 98 patients with biopsy-proven OSCC, while the χ² test was used to analyze the clinicopathological association. Kaplan-Meier estimates were used to determine the prognostic value of XRCC1, ERCC1 and ERCC2 for overall survival, and the log-rank test was used to evaluate the significance of differences. Multivariate analysis revealed a positive association between ERCC2 expression and OSCC recurrence (19.64-fold; 95% CI, 5.00-77.1; P<0.001). In addition, the high protein expression levels of XRCC1, ERCC1 and ERCC2 were associated with poor disease-free and overall survival rates. Therefore, the present study suggested that high ERCC2 expression may be a risk factor for OSCC recurrence.

countfitteR: efficient selection of count distributions to assess DNA damage

Background

DNA double-strand breaks can be counted as discrete foci by imaging techniques. In personalized medicine and pharmacology, the analysis of counting data is relevant for numerous applications, e.g., for cancer and aging research and the evaluation of drug efficacy. By default, it is assumed to follow the Poisson distribution. This assumption, however, may lead to biased results and faulty conclusions in datasets with excess zero values (zero-inflation), a variance larger than the mean (overdispersion), or both. In such cases, the assumption of a Poisson distribution would skew the estimation of mean and variance, and other models like the negative binomial (NB), zero-inflated Poisson or zero-inflated NB distributions should be employed. The model chosen has an influence on the parameter estimation (mean value and confidence interval). Yet the choice of the suitable distribution model is not trivial.

Methods

To support, simplify and objectify this process, we have developed the countfitteR software as an R package. We used a Bayesian approach for distribution model selection and the shiny web application framework for interactive data analysis.

Results

We show the application of our software based on examples of DNA double-strand break count data from phenotypic imaging by multiplex fluorescence microscopy. In analyzing numerous datasets of molecular pharmacological markers (phosphorylated histone H2AX and p53 binding protein), countfitteR demonstrated an equal or superior statistical performance compared to the usually employed two-step procedure, with an overall power of up to 98%. In addition, it still gave information in cases with no result at all from the two-step procedure. In our data sample we found that the NB distribution was the most frequent, with the Poisson distribution taking second place.

Conclusions

countfitteR can perform an automated distribution model selection and thus support the data analysis and lead to objective statistically verifiable estimated values. Originally designed for the analysis of foci in biomedical image data, countfitteR can be used in a variety of areas where non-Poisson distributed counting data is prevalent.

X-ray Ptychography Imaging of Human Chromosomes After Low-dose Irradiation

Studies of the structural and functional role of chromosomes in cytogenetics have spanned more than 10 decades. In this work, we take advantage of the coherent X-rays available at the latest synchrotron sources to extract the individual masses of all 46 chromosomes of metaphase human B and T cells using hard X-ray ptychography. We have produced ‘X-ray karyotypes’ of both heavy metal–stained and unstained spreads to determine the gain or loss of genetic material upon low-level X-ray irradiation doses due to radiation damage. The experiments were performed at the I-13 beamline, Diamond Light Source, Didcot, UK, using the phase-sensitive X-ray ptychography method.

Blocking DNA Damage Repair May Be Involved in Stattic (STAT3 Inhibitor)-Induced FLT3-ITD AML Cell Apoptosis

The FMS-like tyrosine kinase 3 (FLT3)- internal tandem duplication (ITD) mutation can be found in approximately 25% of all acute myeloid leukemia (AML) cases and is associated with a poor prognosis. The main treatment for FLT3-ITD-positive AML patients includes genotoxic therapy and FLT3 inhibitors, which are rarely curative. Inhibiting STAT3 activity can improve the sensitivity of solid tumor cells to radiotherapy and chemotherapy. This study aimed to explore whether Stattic (a STAT3 inhibitor) affects FLT3-ITD AML cells and the underlying mechanism. Stattic can inhibit the proliferation, promote apoptosis, arrest cell cycle at G0/G1, and suppress DNA damage repair in MV4-11cells. During the process, through mRNA sequencing, we found that DNA damage repair-related mRNA are also altered during the process. In summary, the mechanism by which Stattic induces apoptosis in MV4-11cells may involve blocking DNA damage repair machineries.

Paving the way for small-molecule drug discovery

Small-molecule drugs are organic compounds affecting molecular pathways by targeting important proteins, which have a low molecular weight, making them penetrate cells easily. Small-molecule drugs can be developed from leads derived from rational drug design or isolated from natural resources. As commonly used medications, small-molecule drugs can be taken orally, which enter cells to act on intracellular targets. These characteristics make small-molecule drugs promising candidates for drug development, and they are increasingly favored in the pharmaceutical market. Despite the advancements in molecular genetics and effective new processes in drug development, the drugs currently used in clinical practice are inadequate due to their poor efficacy or severe side effects. Therefore, developing new safe and efficient drugs is a top priority for disease control and curing.

RRM2B Is Frequently Amplified Across Multiple Tumor Types: Implications for DNA Repair, Cellular Survival, and Cancer Therapy

RRM2B plays a crucial role in DNA replication, repair and oxidative stress. While germline RRM2B mutations have been implicated in mitochondrial disorders, its relevance to cancer has not been established. Here, using TCGA studies, we investigated RRM2B alterations in cancer. We found that RRM2B is highly amplified in multiple tumor types, particularly in MYC-amplified tumors, and is associated with increased RRM2B mRNA expression. We also observed that the chromosomal region 8q22.3–8q24, is amplified in multiple tumors, and includes RRM2B, MYC along with several other cancer-associated genes. An analysis of genes within this 8q-amplicon showed that cancers that have both RRM2B-amplified along with MYC have a distinct pattern of amplification compared to cancers that are unaltered or those that have amplifications in RRM2B or MYC only. Investigation of curated biological interactions revealed that gene products of the amplified 8q22.3–8q24 region have important roles in DNA repair, DNA damage response, oxygen sensing, and apoptosis pathways and interact functionally. Notably, RRM2B-amplified cancers are characterized by mutation signatures of defective DNA repair and oxidative stress, and at least RRM2B-amplified breast cancers are associated with poor clinical outcome. These data suggest alterations in RR2MB and possibly the interacting 8q-proteins could have a profound effect on regulatory pathways such as DNA repair and cellular survival, highlighting therapeutic opportunities in these cancers.

LINCS gene expression signature analysis revealed bosutinib as a radiosensitizer of breast cancer cells by targeting eIF4G1

Radioresistance is the predominant cause for radiotherapy failure and disease progression, resulting in increased breast cancer‑associated mortality. Using gene expression signature analysis of the Library of Integrated Network‑Based Cellular Signatures (LINCS) and Gene Expression Omnibus (GEO), the aim of the present study was to systematically identify potential candidate radiosensitizers from known drugs. The similarity of integrated gene expression signatures between irradiated eukaryotic translation initiation factor 4 γ 1 (eIF4G1)‑silenced breast cancer cells and known drugs was measured using enrichment scores (ES). Drugs with positive ES were selected as potential radiosensitizers. The radiosensitizing effects of the candidate drugs were analyzed in breast cancer cell lines (MCF‑7, MX‑1 and MDA‑MB‑231) using CCK‑8 and colony formation assays following exposure to ionizing radiation. Cell apoptosis was measured using flow cytometry. The expression levels of eIF4G1 and DNA damage response (DDR) proteins were analyzed by western blotting. Bosutinib was identified as a promising radiosensitizer, as its administration markedly reduced the dosage required both for the drug and for ionizing radiation, which may be associated with fewer treatment‑associated adverse reactions. Moreover, combined treatment of ionizing radiation and bosutinib significantly increased cell killing in all three cell lines, compared with ionizing radiation or bosutinib alone. Among the three cell lines, MX‑1 cells were identified as the most sensitive to both ionizing radiation and bosutinib. Bosutinib markedly downregulated the expression of eIF4G1 in a dose‑dependent manner and also reduced the expression of DDR proteins (including ATM, XRCC4, ATRIP, and GADD45A). Moreover, eIF4G1 was identified as a key target of bosutinib that may regulate DNA damage induced by ionizing radiation. Thus, bosutinib may serve as a potential candidate radiosensitizer for breast cancer therapy.

In vitro biomimetic models for glioblastoma-a promising tool for drug response studies

The poor response of glioblastoma to current treatment protocols is a consequence of its intrinsic drug resistance. Resistance to chemotherapy is primarily associated with considerable cellular heterogeneity, and plasticity of glioblastoma cells, alterations in gene expression, presence of specific tumor microenvironment conditions and blood-brain barrier. In an attempt to successfully overcome chemoresistance and better understand the biological behavior of glioblastoma, numerous tri-dimensional (3D) biomimetic models were developed in the past decade. These novel advanced models are able to better recapitulate the spatial organization of glioblastoma in a real time, therefore providing more realistic and reliable evidence to the response of glioblastoma to therapy. Moreover, these models enable the fine-tuning of different tumor microenvironment conditions and facilitate studies on the effects of the tumor microenvironment on glioblastoma chemoresistance. This review outlines current knowledge on the essence of glioblastoma chemoresistance and describes the progress achieved by 3D biomimetic models. Moreover, comprehensive literature assessment regarding the influence of 3D culturing and microenvironment mimicking on glioblastoma gene expression and biological behavior is also provided. The contribution of the blood-brain barrier as well as the blood-tumor barrier to glioblastoma chemoresistance is also reviewed from the perspective of 3D biomimetic models. Finally, the role of mathematical models in predicting 3D glioblastoma behavior and drug response is elaborated. In the future, technological innovations along with mathematical simulations should create reliable 3D biomimetic systems for glioblastoma research that should facilitate the identification and possibly application in preclinical drug testing and precision medicine.

Fighting Drug Resistance through the Targeting of Drug-Tolerant Persister Cells

Designing specific therapies for drug-resistant cancers is arguably the ultimate challenge in cancer therapy. While much emphasis has been put on the study of genetic alterations that give rise to drug resistance, much less is known about the non-genetic adaptation mechanisms that operate during the early stages of drug resistance development. Drug-tolerant persister cells have been suggested to be key players in this process. These cells are thought to have undergone non-genetic adaptations that enable survival in the presence of a drug, from which full-blown resistant cells may emerge. Such initial adaptations often involve engagement of stress response programs to maintain cancer cell viability. In this review, we discuss the nature of drug-tolerant cancer phenotypes, as well as the non-genetic adaptations involved. We also discuss how malignant cells employ homeostatic stress response pathways to mitigate the intrinsic costs of such adaptations. Lastly, we discuss which vulnerabilities are introduced by these adaptations and how these might be exploited therapeutically.

Small molecule DNA-PK inhibitors as potential cancer therapy: a patent review (2010-present)

Introduction: DNA-dependent protein kinase (DNA-PK) plays a crucial role in the repair of DSBs via non-homologous end joining (NHEJ). Several DNA-PK inhibitors are being investigated for potential anticancer treatment in clinical trials.Area covered: This review aims to give an overview of patents published since 2010 by analyzing the patent space and structure features of scaffolds used in those patents. It also discusses the recent clinical developments and provides perspectives on future challenges and directions in this field.Expert opinion: As a key component of the DNA damage response (DDR) pathway, DNA-PK appears to be a viable drug target for anticancer therapy. The clinical investigation of a DNA-PK inhibitor employs both a monotherapy and a combination strategy. In the combination strategy, a DNA-PK inhibitor is typically combined with a DSB inducer, radiation, a chemotherapy agent, or a PARP inhibitor, etc. Patent analyses suggest that diverse structures comprising different scaffolds from mono-heteroaryl to bicyclic heteroaryl to tricyclic heteroaryl are capable to achieve good DNA-PK inhibitory activity and good DNA-PK selectivity over other closely related enzymes. Several DNA-PK inhibitors are currently being evaluated in clinics, with the hope to get approval in the near future.

Effect of ATR Inhibition in RT Response of HPV-Negative and HPV-Positive Head and Neck Cancers

Radiotherapy (RT) has a central role in head and neck squamous cell carcinoma (HNSCC) treatment. Targeted therapies modulating DNA damage response (DDR) and more specific cell cycle checkpoints can improve the radiotherapeutic response. Here, we assessed the influence of ataxia-telangiectasia mutated and Rad3-related (ATR) inhibition with the ATR inhibitor AZD6738 on RT response in both human papillomavirus (HPV)-negative and HPV-positive HNSCC. We found that ATR inhibition enhanced RT response in HPV-negative and HPV-positive cell lines independent of HPV status. The radiosensitizing effect of AZD6738 was correlated with checkpoint kinase 1 (CHK1)-mediated abrogation of G2/M-arrest. This resulted in the inhibition of RT-induced DNA repair and in an increase in the percentage of micronucleated cells. We validated the enhanced RT response in HPV-negative and HPV-positive xenograft models. These data demonstrate the potential use of ATR inhibition in combination with RT as a treatment option for both HPV-negative and HPV-positive HNSCC patients.

Landscape of extracellular vesicles in the tumour microenvironment: Interactions with stromal cells and with non-cell components, and impacts on metabolic reprogramming, horizontal transfer of neoplastic traits, and the emergence of therapeutic resistance

Extracellular vesicles (EVs) are increasingly recognised as a pivotal player in cell-cell communication, an attribute of EVs that derives from their ability to transport bioactive cargoes between cells, resulting in complex intercellular signalling mediated by EVs, which occurs under both physiological and pathological conditions. In the context of cancer, recent studies have demonstrated the versatile and crucial roles of EVs in the tumour microenvironment (TME). Here, we revisit EV biology, and focus on EV-mediated interactions between cancer cells and stromal cells, including fibroblasts, immune cells, endothelial cells and neurons. In addition, we focus on recent reports indicating interactions between EVs and non-cell constituents within the TME, including the extracellular matrix. We also review and summarise the intricate cancer-associated network modulated by EVs, which promotes metabolic reprogramming, horizontal transfer of neoplastic traits, and therapeutic resistance in the TME. We aim to provide a comprehensive and updated landscape of EVs in the TME, focusing on oncogenesis, cancer progression and therapeutic resistance, together with our future perspectives on the field.

The DNA damage inducible lncRNA SCAT7 regulates genomic integrity and topoisomerase 1 turnover in lung adenocarcinoma

Despite the rapid improvements in unveiling the importance of lncRNAs in all aspects of cancer biology, there is still a void in mechanistic understanding of their role in the DNA damage response. Here we explored the potential role of the oncogenic lncRNA SCAT7 (ELF3-AS1) in the maintenance of genome integrity. We show that SCAT7 is upregulated in response to DNA-damaging drugs like cisplatin and camptothecin, where SCAT7 expression is required to promote cell survival. SCAT7 silencing leads to decreased proliferation of cisplatin-resistant cells in vitro and in vivo through interfering with cell cycle checkpoints and DNA repair molecular pathways. SCAT7 regulates ATR signaling, promoting homologous recombination. Importantly, SCAT7 also takes part in proteasome-mediated topoisomerase I (TOP1) degradation, and its depletion causes an accumulation of TOP1–cc structures responsible for the high levels of intrinsic DNA damage. Thus, our data demonstrate that SCAT7 is an important constituent of the DNA damage response pathway and serves as a potential therapeutic target for hard-to-treat drug resistant cancers.

Oxygen-Enriched Metal-Phenolic X-Ray Nanoprocessor for Cancer Radio-Radiodynamic Therapy in Combination with Checkpoint Blockade Immunotherapy

Radiotherapy (RT) based on DNA damage and reactive oxygen species (ROS) generation has been clinically validated in various types of cancer. However, high dose-dependent induced toxicity to tissues, non-selectivity, and radioresistance greatly limit the application of RT. Herein, an oxygen-enriched X-ray nanoprocessor Hb@Hf-Ce6 nanoparticle is developed for improving the therapeutic effect of RT-radiodynamic therapy (RDT), enhancing modulation of hypoxia tumor microenvironment (TME) and promoting antitumor immune response in combination with programmed cell death protein 1 (PD-1) immune checkpoint blockade. All functional molecules are integrated into the nanoparticle based on metal-phenolic coordination, wherein one high-Z radiosensitizer (hafnium, Hf) coordinated with chlorin e6 (Ce6) modified polyphenols and a promising oxygen carrier (hemoglobin, Hb) is encapsulated for modulation of oxygen balance in the hypoxia TME. Specifically, under single X-ray irradiation, radioluminescence excited by Hf can activate photosensitizer Ce6 for ROS generation by RDT. Therefore, this combinatory strategy induces comprehensive antitumor immune response for cancer eradication and metastasis inhibition. This work presents a multifunctional metal-phenolic nanoplatform for efficient X-ray mediated RT-RDT in combination with immunotherapy and may provide a new therapeutic option for cancer treatment.

Radiation and Immunotherapy in Upper Gastrointestinal Cancers: The Current State of Play

Radiotherapy remains one of the contemporary cornerstones of cancer treatment in the neoadjuvant, curative, adjuvant and palliative settings, either in isolation or as a multimodal approach. Moreover, recent advances in targeted immune checkpoint therapy have firmly established immunotherapy as the fourth pillar in cancer therapy alongside surgery, chemotherapy and notably radiotherapy. There is emerging evidence to suggest both radioresistance and reduced efficacy of immune checkpoint blockade (ICB) are potentiated by the tumour microenvironment (TME) and in fact modulating aspects of this immunosuppressive milieu is instrumental to unlocking anti-tumour immunity. The response rates of Upper Gastrointestinal (UGI) malignancies to ICB remains modest at 10–15%, compared to melanoma at 20–40%. Harnessing the effects of radiotherapy through remodelling of the TME using ICB as a radiosensitisor is an avenue showing promise. Here we explore the rationale behind combining radiotherapy with ICB, as a symbiotic relationship in shifting the balance in favour of anti-tumour immunity. We discuss the effects of radiotherapy on immunogenic cell death, the concept of the abscopal effect, the importance of the cGAS STING pathway, and their relevance in the context of the tumour microenvironment. Furthermore, dosing and timing of radiotherapy and ICB is now being evaluated for its synergistic effects on host tumour immunity, and we review the ongoing efforts and current available literature for single agent and dual agent ICB in combination multimodal therapy for both locally advanced operable and metastatic disease of the upper gastrointestinal tract.

Transcriptome profiling of cells exposed to particular and intense electromagnetic radiation emitted by the "SG-III" prototype laser facility

The experiment of inertial confinement fusion by the "ShengGuang (SG)-III" prototype laser facility is a transient and extreme reaction process within several nanoseconds, which could form a very complicated and intense electromagnetic field around the target chamber of the facility and may lead to harmful effect on people around. In particular, the biological effects arising from such specific environment field could hardly be ignored and have never been investigated yet, and thus, we reported on the investigation of the biological effects of radiation on HaCat cells and PC12 cells to preliminarily assess the biological safety of the target range of the "SG-III" prototype laser facility. The viability revealed that the damage of cells was dose-dependent. Then we compared the transcriptomes of exposed and unexposed PC12 cells by RNA-Seq analysis based on Illumina Novaseq 6000 platform and found that most significantly differentially expressed genes with corresponding Gene Ontology terms and pathways were strongly involved in proliferation, transformation, necrosis, inflammation response, apoptosis and DNA damage. Furthermore, we find increase in the levels of several proteins responsible for cell-cycle regulation and tumor suppression, suggesting that pathways or mechanisms regarding DNA damage repair was are quickly activated. It was found that "SG-III" prototype radiation could induce DNA damage and promote apoptotic necrosis.

Targeting DNA Repair and Chromatin Crosstalk in Cancer Therapy

Simple Summary

Targeting aberrant DNA repair in cancers in addition to transcription and replication is an area of interest for cancer researchers. Inhibition of DNA repair selectively in cancer cells leads to cytotoxic or cytostatic effects and overcomes survival advantages imparted by chromosomal translocations or mutations. In this review, we highlight the relevance of DNA repair-linked events in developmental diseases and cancers and also discuss mechanisms to overcome these events that participate in different cellular processes.

Abstract

Aberrant DNA repair pathways that underlie developmental diseases and cancers are potential targets for therapeutic intervention. Targeting DNA repair signal effectors, modulators and checkpoint proteins, and utilizing the synthetic lethality phenomena has led to seminal discoveries. Efforts to efficiently translate the basic findings to the clinic are currently underway. Chromatin modulation is an integral part of DNA repair cascades and an emerging field of investigation. Here, we discuss some of the key advancements made in DNA repair-based therapeutics and what is known regarding crosstalk between chromatin and repair pathways during various cellular processes, with an emphasis on cancer.

Radiation Response in the Tumour Microenvironment: Predictive Biomarkers and Future Perspectives

Radiotherapy (RT) is a primary treatment modality for a number of cancers, offering potentially curative outcomes. Despite its success, tumour cells can become resistant to RT, leading to disease recurrence. Components of the tumour microenvironment (TME) likely play an integral role in managing RT success or failure including infiltrating immune cells, the tumour vasculature and stroma. Furthermore, genomic profiling of the TME could identify predictive biomarkers or gene signatures indicative of RT response. In this review, we will discuss proposed mechanisms of radioresistance within the TME, biomarkers that may predict RT outcomes, and future perspectives on radiation treatment in the era of personalised medicine.

The p53/RMRP/miR122 signaling loop promotes epithelial-mesenchymal transition during the development of silica-induced lung fibrosis by activating the notch pathway

BACKGROUND

Understanding the roles of long noncoding RNAs (lncRNAs) in EMT would help with establishing novel avenues for further uncovering the mechanisms of lung fibrosis and identifying preventative and therapeutic targets. This study aimed to identify silica-induced specific lncRNAs and investigate the feedback loop regulation among their upstream and downstream genes.

METHODS AND MATERIALS

A microarray assay, quantitative real-time polymerase chain reaction and Western blot analysis dual-luciferase reporter gene activity and chromatin immunoprecipitation assays were used. Moreover, a silica-induced lung fibrosis mouse model was used to verify the roles of the lncRNAs.

RESULTS

Following silica exposure, both RNA component of mitochondrial RNA processing endoribonuclease (RMRP) and p53 were significantly upregulated during the EMT. The upregulation of p53 upon silica exposure activated RMRP expression, which promoted the EMT. When RMRP is overexpressed, additional RMRP acts as a sponge to bind to miR122, thus decreasing miR122 levels. Using microarrays, miR122 was identified as a potential upstream regulator of p53. This relationship was also verified using the dual-luciferase reporter gene. Hence, decreased miR122 levels result in an increase in p53 activity. More importantly, RMRP promotes the transcription of Notch 1, which, in turn, results in Notch pathway activation. We show that the p53/RMRP/miR122 pathway creates a positive feedback loop that promotes EMT progress by activating the Notch signaling pathway.

CONCLUSION

Our data indicated that p53/RMRP/miR122 feedback loop might contribute to the EMT development by activating Notch pathway, which provides new sight into understanding of the complex network regulating silica-induced lung fibrosis.