Enhanced DNA Damage Repair Research Articles

New Emerging Therapeutic Strategies Based on Manipulation of the Redox Regulation Against Therapy Resistance in Cancer.

Background: Resistance to standard therapeutic methods, including chemotherapy, immunotherapy, and targeted therapy, remains a critical challenge in effective cancer treatment. Redox homeostasis modification has emerged as a promising approach to address medication resistance. Objective: This review aims to explore the mechanisms of redox alterations and signaling pathways contributing to treatment resistance in cancer. Methods: In this study, a comprehensive review of the molecular mechanisms underlying drug resistance governed by redox signaling was conducted. Emphasis was placed on understanding how tumor cells manage increased reactive oxygen species (ROS) levels through upregulated antioxidant systems, enabling resistance across multiple therapeutic pathways. Results: Key mechanisms identified include alterations in drug efflux, target modifications, metabolic changes, enhanced DNA damage repair, stemness preservation, and tumor microenvironment remodeling. These pathways collectively facilitate tumor cells' adaptive response and resistance to various cancer treatments. Conclusion: Developing a detailed understanding of the interrelationships between these redox-regulated mechanisms and therapeutic resistance holds potential to improve treatment effectiveness, offering valuable insights for both fundamental and clinical cancer research. Antioxid. Redox Signal. 00, 000-000.

Targeting the gut and tumor microbiome in cancer resistance.

Therapy resistance represents a significant challenge in oncology, occurring in various therapeutic approaches. Recently, animal models and an increasing set of clinical trials highlight the crucial impact of the gut and tumor microbiome on treatment response. The intestinal microbiome contributes to cancer initiation, progression, and formation of distant metastasis. In addition, tumor-associated microbiota is considered a critical player in influencing tumor microenvironment and regulating local immune processes. Intriguingly, numerous studies have successfully identified pathogens within the gut and tumor microbiome that might be linked to a poor response to different therapeutic modalities. The unfavorable microbial composition with the presence of specific microbes participates in cancer resistance and progression via several mechanisms, including upregulation of oncogenic pathways, macrophage polarization reprogramming, metabolism of chemotherapeutic compounds, autophagy pathway modulation, enhanced DNA damage repair, inactivation of a pro-apoptotic cascade, and bacterial secretion of extracellular vesicles, promoting the processes in the metastatic cascade. Targeted elimination of specific intratumoral bacteria appears to enhance treatment response. However, broad-spectrum antibiotic pre-treatment is mostly connected to reduced efficacy due to gut dysbiosis and lower diversity. Mounting evidence supports the potential of microbiota modulation by probiotics and fecal microbiota transplantation to improve intestinal dysbiosis and increase microbial diversity, leading to enhanced treatment efficacy while mitigating adverse effects. In this context, further research concerning the identification of clinically relevant microbiome signatures followed by microbiota-targeted strategies presents a promising approach to overcoming immunotherapy and chemotherapy resistance in refractory patients, improving their outcomes.

USP11 deubiquitinates E-cadherin and maintains the luminal fate of mammary tumor cells to suppress breast cancer

Basal-like breast cancer may originate from luminal epithelial or cancerous cells. Inadequately repaired DNA damage impairs luminal differentiation and promotes aberrant luminal to basal trans-differentiation in mammary epithelial cells (MECs). Ubiquitin-specific peptidase 11 (USP11), a deubiquitinase, plays a critical role in DNA damage repair. The role of USP11 in controlling mammary cell differentiation and tumorigenesis remains poorly understood. We generated Usp11 knockout mice and breast cancer cell lines expressing wild-type (WT) and mutant form of USP11. By using these mutant mice, cell lines, and human USP11-deficient and -proficient breast cancer tissues, we tested how USP11 controls mammary cell fate. We generated Usp11 knock-out mice and found that deletion of Usp11 reduced the expression of E-cadherin and promoted DNA damage in MECs. Overexpression of WT USP11, but not a deubiquitinase-inactive mutant form of USP11, promoted luminal differentiation, enhanced DNA damage repair, and suppressed tumorigenesis in mice. Mechanistically, we found that USP11 enhanced the protein expression of E-cadherin dependent on its deubiquitinase activity, and that USP11 deubiquitinated E-cadherin at K738. We discovered that USP11 bound to E-cadherin through its C-terminal region. In human breast cancers, expression of USP11 was positively correlated with that of E-cadherin, and high USP11 predicted better recurrence-free survival. Our findings provide compelling genetic and biochemical evidence that USP11 not only promotes DNA damage repair but also deubiquitinates E-cadherin and maintains the luminal feature of mammary tumor cells, thereby suppressing luminal breast cancer.

Identification of TAT as a Biomarker Involved in Cell Cycle and DNA Repair in Breast Cancer.

Breast cancer (BC) is the most frequently diagnosed cancer and the primary cause of cancer-related mortality in women. Treatment of triple-negative breast cancer (TNBC) remains particularly challenging due to its resistance to chemotherapy and poor prognosis. Extensive research efforts in BC screening and therapy have improved clinical outcomes for BC patients. Therefore, identifying reliable biomarkers for TNBC is of great clinical importance. Here, we found that tyrosine aminotransferase (TAT) expression was significantly reduced in BC and strongly correlated with the poor prognosis of BC patients, which distinguished BC patients from normal individuals, indicating that TAT is a valuable biomarker for early BC diagnosis. Mechanistically, we uncovered that methylation of the TAT promoter was significantly increased by DNA methyltransferase 3 (DNMT3A/3B). In addition, reduced TAT contributes to DNA replication and cell cycle activation by regulating homologous recombination repair and mismatch repair to ensure genomic stability, which may be one of the reasons for TNBC resistance to chemotherapy. Furthermore, we demonstrated that Diazinon increases TAT expression as an inhibitor of DNMT3A/3B and inhibits the growth of BC by blocking downstream pathways. Taken together, we revealed that TAT is silenced by DNMT3A/3B in BC, especially in TNBC, which promotes the proliferation of tumor cells by supporting DNA replication, activating cell cycle, and enhancing DNA damage repair. These results provide fresh insights and a theoretical foundation for the clinical diagnosis and treatment of BC.

Therapy-induced secretion of spliceosomal components mediates pro-survival crosstalk between ovarian cancer cells

Ovarian cancer often develops resistance to conventional therapies, hampering their effectiveness. Here, using ex vivo paired ovarian cancer ascites obtained before and after chemotherapy and in vitro therapy-induced secretomes, we show that molecules secreted by ovarian cancer cells upon therapy promote cisplatin resistance and enhance DNA damage repair in recipient cancer cells. Even a short-term incubation of chemonaive ovarian cancer cells with therapy-induced secretomes induces changes resembling those that are observed in chemoresistant patient-derived tumor cells after long-term therapy. Using integrative omics techniques, we find that both ex vivo and in vitro therapy-induced secretomes are enriched with spliceosomal components, which relocalize from the nucleus to the cytoplasm and subsequently into the extracellular vesicles upon treatment. We demonstrate that these molecules substantially contribute to the phenotypic effects of therapy-induced secretomes. Thus, SNU13 and SYNCRIP spliceosomal proteins promote therapy resistance, while the exogenous U12 and U6atac snRNAs stimulate tumor growth. These findings demonstrate the significance of spliceosomal network perturbation during therapy and further highlight that extracellular signaling might be a key factor contributing to the emergence of ovarian cancer therapy resistance.

HBXIP induces PARP1 via WTAP-mediated m6A modification and CEBPA-activated transcription in cisplatin resistance to hepatoma.

Poly (ADP-ribose) polymerase 1 (PARP1) is a DNA-binding protein that is involved in various biological functions, including DNA damage repair and transcription regulation. It plays a crucial role in cisplatin resistance. Nevertheless, the exact regulatory pathways governing PARP1 have not yet been fully elucidated. In this study, we present evidence suggesting that the hepatitis B X-interacting protein (HBXIP) may exert regulatory control over PARP1. HBXIP functions as a transcriptional coactivator and is positively associated with PARP1 expression in tissues obtained from hepatoma patients in clinical settings, and its high expression promotes cisplatin resistance in hepatoma. We discovered that the oncogene HBXIP increases the level of PARP1 m6A modification by upregulating the RNA methyltransferase WTAP, leading to the accumulation of the PARP1 protein. In this process, on the one hand, HBXIP jointly activates the transcription factor ETV5, promoting the activation of the WTAP promoter and further facilitating the promotion of the m6A modification of PARP1 by WTAP methyltransferase, enhancing the RNA stability of PARP1. On the other hand, HBXIP can also jointly activate the transcription factor CEBPA, enhance the activity of the PARP1 promoter, and promote the upregulation of PARP1 expression, ultimately leading to enhanced DNA damage repair capability and promoting cisplatin resistance in hepatoma. Notably, aspirin inhibits HBXIP, thereby reducing the expression of PARP1. Overall, our research revealed a novel mechanism for increasing PARP1 abundance, and aspirin therapy could overcome cisplatin resistance in hepatoma.

RUVBL1 ubiquitination by DTL promotes RUVBL1/2-β-catenin-mediated transcriptional regulation of NHEJ pathway and enhances radiation resistance in breast cancer

Radiotherapy effectiveness in breast cancer is limited by radioresistance. Nevertheless, the mechanisms behind radioresistance are not yet fully understood. RUVBL1 and RUVBL2, referred to as RUVBL1/2, are crucial AAA+ ATPases that act as co-chaperones and are connected to cancer. Our research revealed that RUVBL1, also known as pontin/TIP49, is excessively expressed in MMTV-PyMT mouse models undergoing radiotherapy, which is considered a murine spontaneous breast-tumor model. Our findings suggest that RUVBL1 enhances DNA damage repair and radioresistance in breast cancer cells both in vitro and in vivo. Mechanistically, we discovered that DTL, also known as CDT2 or DCAF2, which is a substrate adapter protein of CRL4, promotes the ubiquitination of RUVBL1 and facilitates its binding to RUVBL2 and transcription cofactor β-catenin. This interaction, in turn, attenuates its binding to acetyltransferase Tat-interacting protein 60 (TIP60), a comodulator of nuclear receptors. Subsequently, ubiquitinated RUVBL1 promotes the transcriptional regulation of RUVBL1/2-β-catenin on genes associated with the non-homologous end-joining (NHEJ) repair pathway. This process also attenuates TIP60-mediated H4K16 acetylation and the homologous recombination (HR) repair process. Expanding upon the prior study’s discoveries, we exhibited that the ubiquitination of RUVBL1 by DTL advances the interosculation of RUVBL1/2-β-catenin. And, it then regulates the transcription of NHEJ repair pathway protein. Resulting in an elevated resistance of breast cancer cells to radiation therapy. From the aforementioned, it is evident that targeting DTL-RUVBL1/2-β-catenin provides a potential radiosensitization approach when treating breast cancer.

TULP4 degrades RYBP to enhance DNA damage repair and chemosensitivity of pancreatic ductal adenocarcinoma

TULP4 degrades RYBP to enhance DNA damage repair and chemosensitivity of pancreatic ductal adenocarcinoma

Targeting the Cdc2-like kinase 2 for overcoming platinum resistance in ovarian cancer.

Platinum resistance represents a major barrier to the survival of patients with ovarian cancer (OC). Cdc2-like kinase 2 (CLK2) is a major protein kinase associated with oncogenic phenotype and development in some solid tumors. However, the exact role and underlying mechanism of CLK2 in the progression of OC is currently unknown. Using microarray gene expression profiling and immunostaining on OC tissues, we found that CLK2 was upregulated in OC tissues and was associated with a short platinum-free interval in patients. Functional assays showed that CLK2 protected OC cells from platinum-induced apoptosis and allowed tumor xenografts to be more resistant to platinum. Mechanistically, CLK2 phosphorylated breast cancer gene 1 (BRCA1) at serine 1423 (Ser1423) to enhance DNA damage repair, resulting in platinum resistance in OC cells. Meanwhile, in OC cells treated with platinum, p38 stabilized CLK2 protein through phosphorylating at threonine 343 of CLK2. Consequently, the combination of CLK2 and poly ADP-ribose polymerase inhibitors achieved synergistic lethal effect to overcome platinum resistance in patient-derived xenografts, especially those with wild-type BRCA1. These findings provide evidence for a potential strategy to overcome platinum resistance in OC patients by targeting CLK2.

Abstract 1126: Extracellular vesicle mediated radioresistance in H3K27M-diffuse midline glioma

Abstract H3K27M-Diffuse Midline Gliomas (DMGs) are a subset of uncurable malignant pediatric gliomas and the deadliest form of brain tumors in children worldwide. Radiation therapy, the current standard of care, is initially effective but all tumors become resistant within 4-6 months. H3K27M-DMGs are heterogenous, comprised of an average of 6 genetically distinct subclones. Some subclones harbor mutations in genes previously linked to radiation resistance, such as TP53. We have found subclones are also functionally distinct, with some clones harboring intrinsic radiation resistance. Extracellular signaling between clones is linked with therapy resistance and tumor progression in other tumors, and we hypothesized that radioresistant H3K27M-DMG release small extracellular vesicles (sEVs) that impact the radiosensitivity of neighboring tumor cells. We found that all patient-derived H3K27M-DMG samples examined (n=6) produced sEVs (< 220nm), indicating this is a common feature in this tumor type. We isolated sEVs from a radioresistant (RR) patient-derived H3K27M-DMG cell line and used them to treat radiosensitive (RS) DMG cells. Using flow cytometry to profile sEV uptake dynamics, we found that RR-sEVs are internalized by RS cells within 2 hours of exposure and are retained at 18 hours (p<0.001, compared to control). This uptake can be significantly abrogated by proteinase K treatment of the sEVs, (p<0.001), indicating that uptake involves sEV surface proteins. We then applied a biosensor approach to assess single-cell phenotypic changes in RS DMG after RR-sEV treatment on radiation-induced cell death, DNA damage, and cell senescence, three dynamic processes. Using a genetically encoded death indicator (GEDI), we found that RR-sEVs significantly enhanced the survival of RS cells after acute radiation exposure (p<0.001). This was due to enhanced DNA damage repair as measured by 53BP1 foci (p<0.01). Small RNA sequencing of sEV cargo demonstrated that RR-sEVs express multiple miRNAs that are involved in oncogenic signaling such as the miR-7 family, miR-1246, and miR-1290 at several log fold higher than RS-sEVs. Overall, this data reveals the first functional role for sEVs in the context of radiation induced tumor transformation in DMG. We plan to further investigate the primary route of sEV uptake and define the mechanism through which sEV cargo alters radiosensitivity. This study provides new insight into the impact of heterogeneity and sEVs in mediating radioresistance in H3K27M-DMG and may lead to the development of novel radiosensitizers, which are critically needed for all patients. Citation Format: Viral Oza, Shilpa Sampathi, Yelena Chernyavskava, Kenan Flores, Jessica Blackburn. Extracellular vesicle mediated radioresistance in H3K27M-diffuse midline glioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1126.

HIF-2α-dependent TGFBI promotes ovarian cancer chemoresistance by activating PI3K/Akt pathway to inhibit apoptosis and facilitate DNA repair process

Hypoxia-mediated chemoresistance plays a crucial role in the development of ovarian cancer (OC). However, the roles of hypoxia-related genes (HRGs) in chemoresistance and prognosis prediction and theirs underlying mechanisms remain to be further elucidated. We intended to identify and validate classifiers of hub HRGs for chemoresistance, diagnosis, prognosis as well as immune microenvironment of OC, and to explore the function of the most crucial HRG in the development of the malignant phenotypes. The RNA expression and clinical data of HRGs were systematically evaluated in OC training group. Univariate and multivariate Cox regression analysis were applied to construct hub HRGs classifiers for prognosis and diagnosis assessment. The relationship between classifiers and chemotherapy response and underlying pathways were detected by GSEA, CellMiner and CIBERSORT algorithm, respectively. OC cells were cultured under hypoxia or transfected with HIF-1α or HIF-2α plasmids, and the transcription levels of TGFBI were assessed by quantitative PCR. TGFBI was knocked down by siRNAs in OC cells, CCK8 and in vitro migration and invasion assays were performed to examine the changes in cell proliferation, motility and metastasis. The difference in TGFBI expression was examined between cisplatin-sensitive and -resistant cells, and the effects of TGFBI interference on cell apoptosis, DNA repair and key signaling molecules of cisplatin-resistant OC cells were explored. A total of 179 candidate HRGs were extracted and enrolled into univariate and multivariate Cox regression analysis. Six hub genes (TGFBI, CDKN1B, AKAP12, GPC1, TGM2 and ANGPTL4) were selected to create a HRGs prognosis classifier and four genes (TGFBI, AKAP12, GPC1 and TGM2) were selected to construct diagnosis classifiers. The HRGs prognosis classifier could precisely distinguish OC patients into high-risk and low-risk groups and estimate their clinical outcomes. Furthermore, the high-risk group had higher percentage of Macrophages M2 and exhibited higher expression of immunecheckpoints such as PD-L2. Additionally, the diagnosis classifiers could accurately distinguish OC from normal samples. TGFBI was further verified as a specific key target and demonstrated that its high expression was closely correlated with poor prognosis and chemoresistance of OC. Hypoxia upregulated the expression level of TGFBI. The hypoxia-induced factor HIF-2α but not HIF-1α could directly bind to the promoter region of TGFBI, and facilitate its transcription level. TGFBI was upregulated in cisplatin-sensitive and resistant ovarian cancer cells in a cisplatin time-dependent manner. TGFBI interference downregulated DNA repair-related markers (p-p95/NBS1, RAD51, p-DNA-PKcs, DNA Ligase IV and Artemis), apoptosis-related marker (BCL2) and PI3K/Akt pathway-related markers (PI3K-p110 and p-Akt) in cisplatin-resistant OC cells. In summary, the HRGs prognosis risk classifier could be served as a predictor for OC prognosis and efficacy evaluation. TGFBI, upregulated by HIF-2α as an HRG, promoted OC chemoresistance through activating PI3K/Akt pathway to reduce apoptosis and enhance DNA damage repair pathway.

NPAS2 dampens chemo-sensitivity of lung adenocarcinoma cells by enhancing DNA damage repair

Chemotherapeutic agents, including cisplatin, have remained a cornerstone of lung adenocarcinoma (LUAD) treatment and continue to play an essential role in clinical practice, despite remarkable progress in therapeutic strategies. Hence, a thorough comprehension of the molecular mechanisms underlying chemotherapeutic agent resistance is paramount. Our investigation centered on the potential involvement of the NPAS2 gene in LUAD, which is highly expressed in tumors and its high expression has been associated with unfavorable overall survival rates in patients. Intriguingly, we observed that the depletion of NPAS2 in LUAD cells resulted in increased susceptibility to cisplatin treatment. Furthermore, mRNA sequencing analysis revealed that NPAS2 deficiency downregulated genes crucial to DNA repair. Additionally, NPAS2 depletion significantly impairs γH2AX accumulation, a pivotal component of the DNA damage response. Further investigation demonstrates that NPAS2 plays a crucial role in DNA double-strand breakage repair via homology-directed repair (HDR). Our inquiry into the molecular mechanisms underlying NPAS2 regulation of DDR revealed that it may enhance the stability of H2AX mRNA by binding to its mRNA, thereby upregulating the DNA damage repair pathway. In-vivo experiments further confirmed the crucial role of NPAS2 in modulating the effect of cisplatin in LUAD. Taken together, our findings suggest that NPAS2 binds to and enhances the stability of H2AX mRNA, thereby decreasing the sensitivity of tumor cells to chemotherapy by augmenting DNA damage repair.

A Review: Genetic Mutations as a Key to Unlocking Drug Resistance in Cervical Cancer.

Cervical cancer is the fourth most common cancer in women. Advanced stage and metastatic disease are often associated with poor clinical outcomes. This substantiates the absolute necessity for high-throughput diagnostic and treatment platforms that are patient and tumour specific. Cervical cancer treatment constitutes multimodal intervention. Systemic treatments such as chemotherapy and/or focal radiotherapy are typically applied as neoadjuvant and/or adjuvant strategies. Cisplatin constitutes an integral part of standard cervical cancer treatment approaches. However, despite initial patient response, de novo or delayed/acquired treatment resistance is often reported, and toxicity is of concern. Chemotherapy resistance is associated with major alterations in genomic, metabolomic, epigenetic and proteomic landscapes. This results in imbalanced homeostasis associated with pro-oncogenic and proliferative survival, anti-apoptotic benefits, and enhanced DNA damage repair processes. Although significant developments in cancer diagnoses and treatment have been made over the last two decades, drug resistance remains a major obstacle to overcome.

Hsa_circ_0007919 induces LIG1 transcription by binding to FOXA1/TET1 to enhance the DNA damage response and promote gemcitabine resistance in pancreatic ductal adenocarcinoma

BackgroundCircular RNAs (circRNAs) play important roles in the occurrence and development of cancer and chemoresistance. DNA damage repair contributes to the proliferation of cancer cells and resistance to chemotherapy-induced apoptosis. However, the role of circRNAs in the regulation of DNA damage repair needs clarification.MethodsRNA sequencing analysis was applied to identify the differentially expressed circRNAs. qRT-PCR was conducted to confirm the expression of hsa_circ_0007919, and CCK-8, FCM, single-cell gel electrophoresis and IF assays were used to analyze the proliferation, apoptosis and gemcitabine (GEM) resistance of pancreatic ductal adenocarcinoma (PDAC) cells. Xenograft model and IHC experiments were conducted to confirm the effects of hsa_circ_0007919 on tumor growth and DNA damage in vivo. RNA sequencing and GSEA were applied to confirm the downstream genes and pathways of hsa_circ_0007919. FISH and nuclear-cytoplasmic RNA fractionation experiments were conducted to identify the cellular localization of hsa_circ_0007919. ChIRP, RIP, Co-IP, ChIP, MS-PCR and luciferase reporter assays were conducted to confirm the interaction among hsa_circ_0007919, FOXA1, TET1 and the LIG1 promoter.ResultsWe identified a highly expressed circRNA, hsa_circ_0007919, in GEM-resistant PDAC tissues and cells. High expression of hsa_circ_0007919 correlates with poor overall survival (OS) and disease-free survival (DFS) of PDAC patients. Hsa_circ_0007919 inhibits the DNA damage, accumulation of DNA breaks and apoptosis induced by GEM in a LIG1-dependent manner to maintain cell survival. Mechanistically, hsa_circ_0007919 recruits FOXA1 and TET1 to decrease the methylation of the LIG1 promoter and increase its transcription, further promoting base excision repair, mismatch repair and nucleotide excision repair. At last, we found that GEM enhanced the binding of QKI to the introns of hsa_circ_0007919 pre-mRNA and the splicing and circularization of this pre-mRNA to generate hsa_circ_0007919.ConclusionsHsa_circ_0007919 promotes GEM resistance by enhancing DNA damage repair in a LIG1-dependent manner to maintain cell survival. Targeting hsa_circ_0007919 and DNA damage repair pathways could be a therapeutic strategy for PDAC.

MRE11:p.K464R mutation mediates olaparib resistance by enhancing DNA damage repair in HGSOC

BackgroundAlthough the clinical application of PARP inhibitors has brought hope to ovarian cancer, the problem of its resistance has become increasingly prominent. Therefore, clinical experts have been focused on finding specific indicators and therapeutic targets that can be used for resistance monitoring of PARP inhibitors.ResultsBy cfDNA detecting during Olaparib maintenance therapy in platinum-sensitive relapsed ovarian cancer, we found the presence of MRE11:p.K464R mutation was strongly associated with acquired Olaparib resistance. Structural analysis revealed that the MRE11:p.K464R mutation is situated at a critical site where the MRE11 protein interacts with other biomolecules, leading to potential structural and functional abnormalities of MRE11 protein. Functionally, MRE11:p.K464R mutation enhanced the tolerance of Olaparib by reducing the DNA damage. Mechanistically, MRE11:p.K464R mutation improved the efficiency of DNA damage repair and induce Olaparib resistance by enhancing its binding activity with the interacting proteins (including RAD50 and RPS3). Among them, the enhanced binding of MRE11:p.K464R mutation to RAD50/RPS3 facilitated non-homologous end joining (NHEJ) repair in tumor cells, thereby expanding the scope of research into acquired resistance to PARP inhibitors.ConclusionsOur findings provide a theoretical basis for MRE11:p.K464R mutation as a specific indicator of resistance monitoring in Olaparib treatment, and the exploration of its resistance mechanism provides a novel insights for the formulation of combination ther therapies after Olaparib resistance.

Nitric Oxide Prevents Glioblastoma Stem Cells' Expansion and Induces Temozolomide Sensitization.

Glioblastoma multiforme (GBM) has high mortality and recurrence rates. Malignancy resilience is ascribed to Glioblastoma Stem Cells (GSCs), which are resistant to Temozolomide (TMZ), the gold standard for GBM post-surgical treatment. However, Nitric Oxide (NO) has demonstrated anti-cancer efficacy in GBM cells, but its potential impact on GSCs remains unexplored. Accordingly, we investigated the effects of NO, both alone and in combination with TMZ, on patient-derived GSCs. Experimentally selected concentrations of diethylenetriamine/NO adduct and TMZ were used through a time course up to 21 days of treatment, to evaluate GSC proliferation and death, functional recovery, and apoptosis. Immunofluorescence and Western blot analyses revealed treatment-induced effects in cell cycle and DNA damage occurrence and repair. Our results showed that NO impairs self-renewal, disrupts cell-cycle progression, and expands the quiescent cells' population. Consistently, NO triggered a significant but tolerated level of DNA damage, but not apoptosis. Interestingly, NO/TMZ cotreatment further inhibited cell cycle progression, augmented G0 cells, induced cell death, but also enhanced DNA damage repair activity. These findings suggest that, although NO administration does not eliminate GSCs, it stunts their proliferation, and makes cells susceptible to TMZ. The resulting cytostatic effect may potentially allow long-term control over the GSCs' subpopulation.

Emerging Role of Glioma Stem Cells in Mechanisms of Therapy Resistance.

Since their discovery at the beginning of this millennium, glioma stem cells (GSCs) have sparked extensive research and an energetic scientific debate about their contribution to glioblastoma (GBM) initiation, progression, relapse, and resistance. Different molecular subtypes of GBM coexist within the same tumor, and they display differential sensitivity to chemotherapy. GSCs contribute to tumor heterogeneity and recapitulate pathway alterations described for the three GBM subtypes found in patients. GSCs show a high degree of plasticity, allowing for interconversion between different molecular GBM subtypes, with distinct proliferative potential, and different degrees of self-renewal and differentiation. This high degree of plasticity permits adaptation to the environmental changes introduced by chemo- and radiation therapy. Evidence from mouse models indicates that GSCs repopulate brain tumors after therapeutic intervention, and due to GSC plasticity, they reconstitute heterogeneity in recurrent tumors. GSCs are also inherently resilient to standard-of-care therapy, and mechanisms of resistance include enhanced DNA damage repair, MGMT promoter demethylation, autophagy, impaired induction of apoptosis, metabolic adaptation, chemoresistance, and immune evasion. The remarkable oncogenic properties of GSCs have inspired considerable interest in better understanding GSC biology and functions, as they might represent attractive targets to advance the currently limited therapeutic options for GBM patients. This has raised expectations for the development of novel targeted therapeutic approaches, including targeting GSC plasticity, chimeric antigen receptor T (CAR T) cells, and oncolytic viruses. In this review, we focus on the role of GSCs as drivers of GBM and therapy resistance, and we discuss how insights into GSC biology and plasticity might advance GSC-directed curative approaches.

Chemo-preventive effects and antitumorigenic mechanisms of beer and nonalcoholic beer toward 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) - induced lung tumorigenesis in A/J mice

We investigated the chemopreventive effects of beer, nonalcoholic beers (NABs), and beer-components (glycine betaine (GB)) on NNK-induced lung tumorigenesis in A/J mice, and the possible mechanisms underlying the antitumorigenic effects of beer, NABs, and beer-components. Beer, NABs, and GB reduced NNK-induced lung tumorigenesis. We investigated the antimutagenicity of beer, NABs and beer-components (GB and pseudouridine (PU)) toward the mutagenicity of 1-methyl-3-nitro-1-nitrosoguanidine (MNNG) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Beer, NABs, and beer components were antimutagenic toward MNNG and NNK in the Ames test using S. typhimurium TA1535. In contrast, MNNG and NNK mutagenicity detected in S. typhimurium YG7108, a strain lacking O6-methylguanine DNA methyltransferases (ogtST and adaST) did not decrease in the presence of beer, NABs, or beer components, suggesting that they may mediate its antimutagenic effect by enhancing DNA damage repair. Phosphorylation of Akt and STAT3, with or without epidermal growth factor stimulation, in lung epithelial-like A549 cells were significantly decreased following beer, NABs, GB and PU. They targeted both the initiation and growth/progression steps of carcinogenesis, specifically via antimutagenesis, stimulation of alkyl DNA-adduct repair, and suppression of Akt- and STAT3- mediated growth signaling. GB and PU may contribute, in part, to the biological effects of beer and NABs via the suppression of Akt and STAT3 phosphorylation.

Incorporation of triapine (T) with cisplatin chemoradiation (CRT) for locally advanced cervical and vaginal cancer: Results from NRG-GY006, a phase III randomized trial.

5502 Background: Definitive cisplatin-based chemoradiation (CRT) plus brachytherapy for locally advanced cervical cancer (FIGO IB3-IVA) results in sustained survival for 60-70% of patients. Recent studies integrating anti-PD-1 checkpoint immunotherapy (CALLA, NCT03830866) or consolidation chemotherapy (OUTBACK, ACTRN12610000732088) have not demonstrated a survival benefit over CRT. Intrinsic overexpression of ribonucleotide reductase may enhance DNA damage repair due to CRT. We report on the efficacy and tolerability of adding the ribonucleotide reductase inhibitor, triapine, to CRT. Methods: NRG GY006 is a randomized, open-label phase III clinical trial. Eligible patients had FIGO 2009 locally advanced cervical (stages IB2, II, IIIB or IVA without radiographic evidence of para-aortic nodal involvement) or stages II-IV vaginal cancer. Patients were randomly assigned to receive cisplatin (40 mg/m2 weekly) with RT 45 Gy + lymph node boost alone (CRT) or CRT in combination with 15 total infusions of triapine (25 mg/m2 IV) Mon/Wed/Fri (CRT + T). Both image guided IMRT or 3D RT were allowed but needed to be specified and pass a rigorous credentialing process. All RT plans had a pre-treatment review with expert planning feedback to the sites. The primary endpoint was overall survival (OS); secondary endpoint was progression-free survival. Exploratory endpoints included rate of complete metabolic response on post treatment PET/CT imaging at 3 months and knowledge-based planning for image guided IMRT. The target sample was 450 with 127 OS events. The design was to provide 80% power to detect a 10% improvement in OS at 3 years over the control (or HR = 0.6) at 2.5% significance level including one interim futility analysis at 50% information time. Results: Between 1/15/16 and 9/22/22 448 eligible patients were randomized to CRT (n=224) or CRT+T (n=224). The database was locked on 10/18/22 with 69 deaths. Median age was 47 years (range 23-85 years). The majority had cervical cancer (93.3%) and squamous cell carcinoma (82%). 52% had FIGO stage II disease. Racial/ethnic distribution included non-Hispanic white (53.8%), Hispanic/Latina (22.5%), and black (15.2%). IMRT was used in (74.3%) and HDR brachytherapy (98.2%) of cases. No differences in Grade 3-5 toxicities were observed: CRT =52% and CRT +T= 49% with Two G5 toxicities (cardiac arrest and acidosis) in the CRT+T arm. 343 patients have completed all protocol directed therapy. With a median follow-up of 28 months (IQR 15-45 months), the median PFS and OS for both arms were not reached yet. HR for death was 1.018 (95% CI 0.634-1.635), the conditional power was 15% to detect a HR = 0.6 at 100% information time. Conclusions: The addition of triapine to CRT did not improve OS. Clinical trial information: NCT02466971 .

Characterization and mechanisms of radioresistant lung squamous cell carcinoma cell lines.

Radiotherapy is an important clinical treatment for patients with lung squamous cell carcinoma (LUSC), and resistance to radiotherapy is an important cause of recurrence and metastasis in LUSC. The aim of this study was to establish and explore the biological characteristics of radioresistant LUSC cells. The LUSC cell lines NCI-H2170 and NCI-H520 were irradiated (4 Gy × 15Fraction). Radiosensitivity, cell apoptosis, cell cycle, and DNA damage repair were measured by clonogenic survival assay, flow cytometry, immunofluorescence for γ-H2AX foci, and Comet assay, respectively. Activation of p-ATM(Ser1981), p-CHK2(Th68), p-DNA-PKcs (Ser2056), and Ku70/Ku80 was measured by western blot. Proteomics was used to explore the differential genes and enriched signaling pathways between radioresistant cell lines and parental lines. In vivo nude mouse xenograft experiments further verified the feasibility of the radioresistant LUSC cell lines. After fractionated irradiation (total dose of 60 Gy), radioresistant cells had decreased radiosensitivity, increased G0/G1 phase arrest, enhanced DNA damage repair ability, and through the ATM/CHK2 and DNA-PKcs/Ku70 pathways regulated double strands break. The upregulated differential genes in radioresistant cell lines were mainly enriched in biological pathways such as cell migration and extracellular matrix (ECM)-receptor interaction. In vivo verification of decreased radiosensitivity of radioresistant cells CONCLUSIONS: Radioresistant LUSC cell lines were established by fractional radiotherapy, which regulates IR-induced DNA damage repair through ATM/CHK2 and DNA-PKcs/Ku70. Tandem Mass Tags (TMT) quantitative proteomics found that the biological process pathway of cell migration and ECM-receptor interaction are upregulated in LUSC radioresistant cells.