Resistance to DNA-damaging treatment in non-small cell lung cancer tumor-initiating cells involves reduced DNA-PK/ATM activation and diminished cell cycle arrest

SND1 Promotes Radioresistance in Cervical Cancer Cells by Targeting the DNA Damage Response

Background: Radiotherapy is one of the most effective therapeutic strategies for cervical cancer patients, although radioresistance-mediated residual and recurrent tumors are the main cause of treatment failure. However, the mechanism of tumor radioresistance is still elusive. DNA damage response pathways are key determinants of radioresistance. The purpose of this study was to investigate the role and mechanism of SND1 in radioresistance of cervical cancer. Methods: A stable HeLa cell line with SND1 knockout (HeLa-KO) was generated through a modified CRISPR/Cas9 double-nicking gene editing system. The stable CaSki cell lines with SND1 knockdown (CaSki-Ctrl, CaSki-SND1-sh-1, CaSki-SND1-sh-2) were constructed through lentivirus transfection with the pSil-SND1-sh-1 and pSil-SND1-sh-2 plasmids. Results: It was observed that SND1 deficiency significantly increased the radiosensitivity of cervical cancer cells. It was also found that silencing SND1 promotes radiation-induced apoptosis. Significantly, the cells with a loss of SND1 function exhibited inefficient ataxia telangiectasia mutated pathway activation, subsequently impairing DNA repair and G2/M checkpoint arrest. In addition, threonine 103 is an important phosphorylation site of SND1 under DNA damaging stress. Conclusion: Collectively, the results of this study reveal a potent radiosensitizing effect of silencing SND1 or T103 mutation on cervical cancer cells, providing novel insights into potential therapeutic strategies for cervical cancer treatment.

AutoCancer as an automated multimodal framework for early cancer detection

Current studies in early cancer detection based on liquid biopsy data often rely on off-the-shelf models and face challenges with heterogeneous data, as well as manually designed data preprocessing pipelines with different parameter settings. To address those challenges, we present AutoCancer, an automated, multimodal, and interpretable transformer-based framework. This framework integrates feature selection, neural architecture search, and hyperparameter optimization into a unified optimization problem with Bayesian optimization. Comprehensive experiments demonstrate that AutoCancer achieves accurate performance in specific cancer types and pan-cancer analysis, outperforming existing methods across three cohorts. We further demonstrated the interpretability of AutoCancer by identifying key gene mutations associated with non-small cell lung cancer to pinpoint crucial factors at different stages and subtypes. The robustness of AutoCancer, coupled with its strong interpretability, underscores its potential for clinical applications in early cancer detection.

Nanomedicine Combats Drug Resistance in Lung Cancer

Lung cancer is the second most prevalent cancer and the leading cause of cancer-related death worldwide. Surgery, chemotherapy, molecular targeted therapy, immunotherapy, and radiotherapy are currently available as treatment methods. However, drug resistance is a significant factor in the failure of lung cancer treatments. Novel therapeutics have been exploited to address complicated resistance mechanisms of lung cancer and the advancement of nanomedicine is extremely promising in terms of overcoming drug resistance. Nanomedicine equipped with multifunctional and tunable physiochemical properties in alignment with tumor genetic profiles can achieve precise, safe, and effective treatment while minimizing or eradicating drug resistance in cancer. Here, this work reviews the discovered resistance mechanisms for lung cancer chemotherapy, molecular targeted therapy, immunotherapy, and radiotherapy, and outlines novel strategies for the development of nanomedicine against drug resistance. This work focuses on engineering design, customized delivery, current challenges, and clinical translation of nanomedicine in the application of resistant lung cancer.

Mechanistic insights from high resolution DNA damage analysis to understand mixed radiation exposure

Cells exposed to densely ionising high and scattered low linear energy transfer (LET) radiation (50 % dose of each) react more strongly than to the same dose of each separately. The relationship between DNA double strand break location inside the nucleus and chromatin structure was evaluated, using high-resolution transmission electron microscopy (TEM) in breast cancer MDA-MB-231 cells at 30 min post 5 Gy. Additionally, response to high and/or low LET radiation was assessed using single (1 ×1.5 Gy) versus fractionated dose delivery (5 ×0.3 Gy). By TEM analysis, the highest total number of γH2AX nanobeads were found in cells irradiated with alpha radiation just prior to gamma radiation (called mixed beam), followed by alpha, then gamma radiation. γH2AX foci induced by mixed beam radiation tended to be surrounded by open chromatin (lighter TEM regions), yet foci containing the highest number of beads, i.e. larger foci representing complex damage, remained in the heterochromatic areas. The γH2AX large focus area was also greater in mixed beam-treated cells when analysed by immunofluorescence. Fractionated mixed beams given daily induced the strongest reduction in cell viability and colony formation in MDA-MB-231 and osteosarcoma U2OS cells compared to the other radiation qualities, as well as versus acute exposure. This may partially be explained by recurring low LET oxidative DNA damage by every fraction together with a delay in recompaction of chromatin after high LET, demonstrated by low levels of heterochromatin marker H3K9me3 at 2 h after the last mixed beam fraction in MDA-MB-231. In conclusion, early differences in response to complex DNA damage may lead to a stronger cell kill induced by fractionated exposure, which suggest a therapeutic potential of combined high and low LET irradiation.

3D Cell Models in Radiobiology: Improving the Predictive Value of In Vitro Research

Cancer is intrinsically complex, comprising both heterogeneous cellular composition and extracellular matrix. In vitro cancer research models have been widely used in the past to model and study cancer. Although two-dimensional (2D) cell culture models have traditionally been used for cancer research, they have many limitations, such as the disturbance of interactions between cellular and extracellular environments and changes in cell morphology, polarity, division mechanism, differentiation and cell motion. Moreover, 2D cell models are usually monotypic. This implies that 2D tumor models are ineffective at accurately recapitulating complex aspects of tumor cell growth, as well as their radiation responses. Over the past decade there has been significant uptake of three-dimensional (3D) in vitro models by cancer researchers, highlighting a complementary model for studies of radiation effects on tumors, especially in conjunction with chemotherapy. The introduction of 3D cell culture approaches aims to model in vivo tissue interactions with radiation by positioning itself halfway between 2D cell and animal models, and thus opening up new possibilities in the study of radiation response mechanisms of healthy and tumor tissues.

Aucubin enhances the antitumor activity of cisplatin through the inhibition of PD-L1 expression in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a leading cause of cancer-associated mortality in the world. However, the anticancer effects of aucubin against HCC have yet to be reported. Cisplatin often decreased CD8⁺ tumor-infiltrating lymphocytes in the tumor microenvironment through increasing programmed death-ligand 1 (PD-L1) expression, which seriously affected the prognostic effect of cisplatin in the treatment of patients with HCC. Therefore, it is necessary to identify a novel therapeutic avenue to increase the sensitivity of cisplatin against HCC.

PURPOSE

This study aims to evaluate the anti-tumor effect of aucubin on HCC, and also to reveal the synergistic effects and mechanism of aucubin and cisplatin against HCC.

STUDY DESIGN AND METHODS

An H22 xenograft mouse model was established for the in vivo experiments. Cancer cell proliferation was detected by MTT assay. RT-qPCR was performed to analyze CD274 mRNA expression in vitro. Western blotting was employed to determine the expression levels of the PD-L1, p-Akt, Akt, p-β-catenin, and β-catenin in vitro. Immunofluorescence was carried out to examine β-catenin nuclear accumulation in HCC cells. Immunohistochemistry was used to detect tumoral PD-L1 and CD8α expression in xenograft mouse model.

RESULTS

Aucubin inhibits tumor growth in a xenograft HCC mouse model, but did not affect HCC cell viability in vitro. Aucubin treatment significantly inhibited PD-L1 expression through inactivating Akt/β-catenin signaling pathway in HCC cells. Overexpression of PD-L1 dramatically reversed aucubin-mediated tumoral CD8⁺ T cell infiltration and alleviated the antitumor activity of aucubin in xenograft mouse model. Moreover, Cisplatin could induce the expression of PD-L1 through the activation of the Akt/β-catenin signaling pathway in HCC cells, which can be blocked by aucubin in vitro. In xenograft mouse model, cisplatin treatment induced PD-L1 expression and alleviated the infiltration of CD8⁺ T lymphocytes in the tumor microenvironment. Aucubin not only abrogated cisplatin-induced PD-L1 expression but also enhanced the antitumor efficacy of cisplatin in a mouse xenograft model of HCC.

CONCLUSION

Aucubin exerts antitumor activity against HCC and also enhances the antitumor activity of cisplatin by suppressing the Akt/β-catenin/PD-L1 axis.

Resveratrol suppresses lung cancer by targeting cancer stem-like cells and regulating tumor microenvironment

Increasing evidence indicate that cancer stem cells (CSCs) are the key driver of tumor initiation and recurrence. The cellular and soluble components of the tumor microenvironment (TME) impact on cancer initiation and progression, such as cytokines and chemokines. Thus, targeting CSCs and TME is a novel anti-cancer approach. Resveratrol (RES), a bioactive phytochemical extracted from various plants, exhibits tumor-suppressing activities in lung cancer, yet the mechanism remains poorly understood. Our data showed that the expression level of IL-6 was positively correlated with the presence of lung cancer stem-like cells (LCSCs) in human lung cancer tissues. In vitro results showed that IL-6 was highly elevated in lung cancer sphere-forming cells and could enhance the stemness of LCSCs, including tumor sphere formation ability, the percentage of CD133 positive cells, and the expression of LCSC specific markers (CD133, ALDH1A1 and Nanog). Simultaneously, our results confirmed that RES effectively inhibited LCSC properties, downregulated Wnt/β-catenin signaling and reduced IL-6 level in vitro and in vivo. Furthermore, we found RES treatment attenuated the activation of Wnt/β-catenin signaling by LiCl (GSK3β agonist). IL-6-promoted LCSC properties and Wnt/β-catenin signaling was also reversed by RES. Taken together, these data illustrated that RES inhibited lung cancer by targeting LCSCs and IL-6 in TME. The novel findings from this study provided evidence that RES exhibited multi-target effects on suppression of lung cancer and could be a novel potent cancer-preventive compound.

Clinical Radiobiology for Radiation Oncology

This chapter is focused on radiobiological aspects at the molecular, cellular, and tissue level which are relevant for the clinical use of ionizing radiation (IR) in cancer therapy. For radiation oncology, it is critical to find a balance, i.e., the therapeutic window, between the probability of tumor control and the probability of side effects caused by radiation injury to the healthy tissues and organs. An overview is given about modern precision radiotherapy (RT) techniques, which allow optimal sparing of healthy tissues. Biological factors determining the width of the therapeutic window are explained. The role of the six typical radiobiological phenomena determining the response of both malignant and normal tissues in the clinic, the 6R’s, which are Reoxygenation, Redistribution, Repopulation, Repair, Radiosensitivity, and Reactivation of the immune system, is discussed. Information is provided on tumor characteristics, for example, tumor type, growth kinetics, hypoxia, aberrant molecular signaling pathways, cancer stem cells and their impact on the response to RT. The role of the tumor microenvironment and microbiota is described and the effects of radiation on the immune system including the abscopal effect phenomenon are outlined. A summary is given on tumor diagnosis, response prediction via biomarkers, genetics, and radiomics, and ways to selectively enhance the RT response in tumors. Furthermore, we describe acute and late normal tissue reactions following exposure to radiation: cellular aspects, tissue kinetics, latency periods, permanent or transient injury, and histopathology. Details are also given on the differential effect on tumor and late responding healthy tissues following fractionated and low dose rate irradiation as well as the effect of whole-body exposure.

Isothiocyanates (ITCs) 1-(Isothiocyanatomethyl)-4-phenylbenzene and 1-Isothiocyanato-3,5-bis(trifluoromethyl)benzene—Aldehyde Dehydrogenase (ALDH) Inhibitors, Decreases Cisplatin Tolerance and Migratory Ability of NSCLC

One of the main treatment modalities for non-small-cell lung cancer (NSCLC) is cisplatin-based chemotherapy. However, the acquisition of cisplatin resistance remains a major problem. Existing chemotherapy regimens are often ineffective against cancer cells expressing aldehyde dehydrogenase (ALDH). As such, there is an urgent need for therapies targeting ALDH-positive cancer cells. The present study compares the anticancer properties of 36 structurally diverse isothiocyanates (ITCs) against NSCLC cells with the ALDH inhibitor disulfiram (DSF). Their potential affinity to ALDH isoforms and ABC proteins was assessed using AutoDockTools, allowing for selection of three compounds presenting the strongest affinity to all tested proteins. The selected ITCs had no impact on NSCLC cell viability (at tested concentrations), but significantly decreased the cisplatin tolerance of cisplatin-resistant variant of A549 (A549CisR) and advanced (stage 4) NSCLC cell line H1581. Furthermore, long-term supplementation with ITC 1-(isothiocyanatomethyl)-4-phenylbenzene reverses the EMT phenotype and migratory potential of A549CisR to the level presented by parental A549 cells, increasing E-Cadherin expression, followed by decreased expression of ABCC1 and ALDH3A1. Our data indicates that the ALDH inhibitors DSF and ITCs are potential adjuvants of cisplatin chemotherapy.

Efficient DNA Repair Mitigates Replication Stress Resulting in Less Immunogenic Cytosolic DNA in Radioresistant Breast Cancer Stem Cells

Cancer stem cells (CSCs) are a major cause of tumor therapy failure. This is mainly attributed to increased DNA repair capacity and immune escape. Recent studies have shown that functional DNA repair via homologous recombination (HR) prevents radiation-induced accumulation of DNA in the cytoplasm, thereby inhibiting the intracellular immune response. However, it is unclear whether CSCs can suppress radiation-induced cytoplasmic dsDNA formation. Here, we show that the increased radioresistance of ALDH1-positive breast cancer stem cells (BCSCs) in S phase is mediated by both enhanced DNA double-strand break repair and improved replication fork protection due to HR. Both HR-mediated processes lead to suppression of radiation-induced replication stress and consequently reduction of cytoplasmic dsDNA. The amount of cytoplasmic dsDNA correlated significantly with BCSC content (p=0.0002). This clearly indicates that HR-dependent avoidance of radiation-induced replication stress mediates radioresistance and contributes to its immune evasion. Consistent with this, enhancement of replication stress by inhibition of ataxia telangiectasia and RAD3 related (ATR) resulted in significant radiosensitization (SER37 increase 1.7-2.8 Gy, p<0.0001). Therefore, disruption of HR-mediated processes, particularly in replication, opens a CSC-specific radiosensitization option by enhancing their intracellular immune response.

The Cationic Amphiphilic Drug Hexamethylene Amiloride Eradicates Bulk Breast Cancer Cells and Therapy-Resistant Subpopulations with Similar Efficiencies

The resistance of cancer cell subpopulations, including cancer stem cell (CSC) populations, to apoptosis-inducing chemotherapeutic agents is a key barrier to improved outcomes for cancer patients. The cationic amphiphilic drug hexamethylene amiloride (HMA) has been previously demonstrated to efficiently kill bulk breast cancer cells independent of tumor subtype or species but acts poorly toward non-transformed cells derived from multiple tissues. Here, we demonstrate that HMA is similarly cytotoxic toward breast CSC-related subpopulations that are resistant to conventional chemotherapeutic agents, but poorly cytotoxic toward normal mammary stem cells. HMA inhibits the sphere-forming capacity of FACS-sorted human and mouse mammary CSC-related cells in vitro, specifically kills tumor but not normal mammary organoids ex vivo, and inhibits metastatic outgrowth in vivo, consistent with CSC suppression. Moreover, HMA inhibits viability and sphere formation by lung, colon, pancreatic, brain, liver, prostate, and bladder tumor cell lines, suggesting that its effects may be applicable to multiple malignancies. Our observations expose a key vulnerability intrinsic to cancer stem cells and point to novel strategies for the exploitation of cationic amphiphilic drugs in cancer treatment.

Novel Aurora A Kinase Inhibitor Fangchinoline Enhances Cisplatin-DNA Adducts and Cisplatin Therapeutic Efficacy in OVCAR-3 Ovarian Cancer Cells-Derived Xenograft Model

Aurora A kinase (Aurora A) is a serine/threonine kinase regulating control of multiple events during cell-cycle progression. Playing roles in promoting proliferation and inhibiting cell death in cancer cells leads Aurora A to become a target for cancer therapy. It is overexpressed and associated with a poor prognosis in ovarian cancer. Improving cisplatin therapy outcomes remains an important issue for advanced-stage ovarian cancer treatment, and Aurora A inhibitors may improve it. In the present study, we identified natural compounds with higher docking scores than the known Aurora A ligand through structure-based virtual screening, including the natural compound fangchinoline, which has been associated with anticancer activities but not yet investigated in ovarian cancer. The binding and inhibition of Aurora A by fangchinoline were verified using cellular thermal shift and enzyme activity assays. Fangchinoline reduced viability and proliferation in ovarian cancer cell lines. Combination fangchinoline and cisplatin treatment enhanced cisplatin-DNA adduct levels, and the combination index revealed synergistic effects on cell viability. An in vivo study showed that fangchinoline significantly enhanced cisplatin therapeutic effects in OVCAR-3 ovarian cancer-bearing mice. Fangchinoline may inhibit tumor growth and enhance cisplatin therapy in ovarian cancer. This study reveals a novel Aurora A inhibitor, fangchinoline, as a potentially viable adjuvant for ovarian cancer therapy.

Novel coumarin derivatives containing a triazole moiety: A study on synthesis, cytotoxicity, membrane dysfunction, apoptosis, cell cycle, and antiangiogenic studies

BACKGROUND

Coumarin is a functional compound with a pronounced wide range of biological activities and has recently been shown to have anticancer effects on various human cancer cells. Cisplatin is widely used in treating many cancers, but its effectiveness is limited due to acquired resistance and dose-related side effects.

OBJECTIVE

This study aimed to reveal the chemosensitizing ability of novel synthesized coumarin-triazole hybrid compounds (3a-f) compared to the cisplatin in A549, MCF-7, and HeLa cancer cells.

METHODS

Cytotoxicity was determined by MTT assay. Lactate dehydrogenase (LDH), antioxidant/oxidant status, DNA fragmentation were determined spectrophotometrically using commercial kits. Muse™ Cell Analyzer was used to assess cell cycle progression. Pro/anti-apoptotic gene expressions were determined by Real-Time qPCR. The antiangiogenic activity was determined by VEGF expression and Hen's chorioallantoic membrane model.

RESULTS

Compounds 3c, -d, -e, and -f potentiated the cisplatin-induced cytotoxicity through the increased LDH release and DNA fragmentation, induced G2/M cell cycle arrest, overproduction of oxidative stress, and decrease of cellular antioxidant levels. These compounds combined with cisplatin caused upregulation in the pro-apoptotic Bax, Bıd, caspase-3, caspase-8, caspase-9, Fas, and p53 gene expressions while downregulating anti-apoptotic DFFA, NFkB1, and Bcl2 gene expressions. These combinations caused vascular loss and a reduction in VEGF expression.

CONCLUSION

These results suggest that a combinational regimen of coumarin compounds with cisplatin could be enhancing the effect of cisplatin in A549 cells. Besides, considering compounds have relatively low toxicity in normal cells, they decrease the dose requirement of cisplatin in cancer treatments.

Beyond the Double-Strand Breaks: The Role of DNA Repair Proteins in Cancer Stem-Cell Regulation

Simple Summary

Cancer stem cells (CSCs) are a tumor cell population maintaining tumor growth and promoting tumor relapse if not wholly eradicated during treatment. CSCs are often equipped with molecular mechanisms making them resistant to conventional anti-cancer therapies whose curative potential depends on DNA damage-induced cell death. An elevated expression of some key DNA repair proteins is one of such defense mechanisms. However, new research reveals that the role of critical DNA repair proteins is extending far beyond the DNA repair mechanisms. This review discusses the diverse biological functions of DNA repair proteins in CSC maintenance and the adaptation to replication and oxidative stress, anti-cancer immune response, epigenetic reprogramming, and intracellular signaling mechanisms. It also provides an overview of their potential therapeutic targeting.

Abstract

Cancer stem cells (CSCs) are pluripotent and highly tumorigenic cells that can re-populate a tumor and cause relapses even after initially successful therapy. As with tissue stem cells, CSCs possess enhanced DNA repair mechanisms. An active DNA damage response alleviates the increased oxidative and replicative stress and leads to therapy resistance. On the other hand, mutations in DNA repair genes cause genomic instability, therefore driving tumor evolution and developing highly aggressive CSC phenotypes. However, the role of DNA repair proteins in CSCs extends beyond the level of DNA damage. In recent years, more and more studies have reported the unexpected role of DNA repair proteins in the regulation of transcription, CSC signaling pathways, intracellular levels of reactive oxygen species (ROS), and epithelial–mesenchymal transition (EMT). Moreover, DNA damage signaling plays an essential role in the immune response towards tumor cells. Due to its high importance for the CSC phenotype and treatment resistance, the DNA damage response is a promising target for individualized therapies. Furthermore, understanding the dependence of CSC on DNA repair pathways can be therapeutically exploited to induce synthetic lethality and sensitize CSCs to anti-cancer therapies. This review discusses the different roles of DNA repair proteins in CSC maintenance and their potential as therapeutic targets.

Natural anthraquinone compound emodin as a novel inhibitor of aurora A kinase: A pilot study

Aurora kinase A (AURKA) carries out an essential role in proliferation and involves in cisplatin resistance in various cancer cells. Overexpression of AURKA is associated with the poor prognosis of cancer patients. Thus, AURKA has been considered as a target for cancer therapy. Developing AURKA inhibitors became an important issue in cancer therapy. A natural compound emodin mainly extracted from rhubarbs possesses anti-cancer properties. However, the effect of emodin on AURKA has never been investigated. In the present study, molecular docking analysis indicated that emodin interacts with AURKA protein active site. We also found nine emodin analogues from Key Organic database by using ChemBioFinder software. Among that, one analogue 8L-902 showed a similar anti-cancer effect as emodin. The bindings of emodin and 8L-902 on AURKA protein were confirmed by cellular thermal shift assay. Furthermore, emodin inhibited the AURKA kinase activity in vitro and enhanced the cisplatin-DNA adduct level in a resistant ovarian cancer cell line. It seems that emodin may have the potential to inhibit cancer cell growth and enhance cisplatin therapy in cancer with resistance. Collectively, our finding reveals a novel AURKA inhibitor, emodin, which may be vulnerable to ovarian cancer therapy in the future.

Ampelopsin Suppresses Stem Cell Properties Accompanied by Attenuation of Oxidative Phosphorylation in Chemo- and Radio-Resistant MDA-MB-231 Breast Cancer Cells

Ampelopsin, also known as dihydromyricetin, is a commonly found flavonoid in medicinal plants. The cancer stem cell (CSC) population is a promising target for triple-negative breast cancer (TNBC). In this study, flavonoid screening was performed in the established MDA-MB-231/IR cell line, which is enriched in CSCs. Ampelopsin suppressed the proliferation and colony formation of stem cell-rich MDA-MB-231/IR, while inducing their apoptosis. Importantly, ampelopsin displayed an inhibitory impact on the stemness features of MDA-MB-231/IR cells, demonstrated by decreases in mammosphere formation, the CD44⁺/CD24^-/low population, aldehyde dehydrogenase activity, and the levels of stem cell markers (e.g., CD44, MRP1, β-catenin, and KLF4). Ampelopsin also suppressed the epithelial-mesenchymal transition, as evidenced by decreases in migration, invasion capacity, and mesenchymal markers, as well as an increase in the epithelial marker E-cadherin. Moreover, ampelopsin significantly impaired oxidative phosphorylation by reducing the oxygen consumption rate and adenosine triphosphate production in MDA-MB-231/IR cells. Notably, ampelopsin treatment significantly reduced the levels of the phosphorylated forms of IκBα and NF-κB p65, as well as the levels of tumor necrosis factor (TNF)-α-stimulated phosphorylation of IκBα and NF-κB p65. These results demonstrated that ampelopsin prevents the TNF-α/NF-κB signaling axis in breast CSCs.

A high-throughput screen identifies inhibitors of lung cancer stem cells

Metastasis is the main cause of cancer morbidity and mortality. Cancer stem cells (CSCs) are a rare subpopulation of cancer cells that can drive metastasis. The identification of CSC inhibitors and CSC-related genes is an alluring strategy for suppressing metastasis. Here, we established a simple and repeatable high-throughput CSC inhibitor screening platform that combined tumor sphere formation assays and cell viability assays. Human lung cancer cells were cocultured with 1280 pharmacologically active compounds (FDA-approved). Fifty-four candidate compounds obtained from our screening system completely or partially inhibited tumor sphere formation. A total of 5 of these 54 compounds (prochlorperazine dimaleate, thioridazine hydrochloride, ciproxifan hydrochloride, Ro 25-6981 hydrochloride, and AMN 082) completely inhibited the self-renewal of CSCs without cytotoxicity in vitro via their targets and suppressed lung cancer metastasis in vivo, suggesting that our screening platform is selective and reliable. DRD2, HRH3, and GRIN2B exhibited potent genes promoting CSCs in vitro experiments and clinical datasets. Further validation of the top hit (DRD2) and previously published studies demonstrate that our screening platform is a useful tool for CSC inhibitor and CSC-related gene screening.

Metformin impairs cisplatin resistance effects in A549 lung cancer cells through mTOR signaling and other metabolic pathways

Lung cancer is the leading cause of cancer‑associated death worldwide and exhibits intrinsic and acquired therapeutic resistance to cisplatin (CIS). The present study investigated the role of mTOR signaling and other signaling pathways after metformin (MET) treatment in control and cisplatin‑resistant A549 cells, mapping pathways and possible targets involved in CIS sensitivity. MTT, flow cytometry, clonogenic assay, western blotting, proteomic analysis using the Stable Isotope Labeling by Amino acids in Cell culture (SILAC) approach and reverse transcription‑quantitative PCR were performed. The results revealed that CIS treatment induced mTOR signaling pathway overactivation, and the mTOR status was restored by MET. MET and the mTOR inhibitor rapamycin (RAPA) decreased the viability in control and resistant cells, and decreased the cell size increase induced by CIS. In control cells, MET and RAPA decreased colony formation after 72 h and decreased IC₅₀ values, potentiating the effects of CIS. Proteomics analysis revealed important pathways regulated by MET, including transcription, RNA processing and IL‑12‑mediated signaling. In CIS‑resistant cells, MET regulated the apoptotic process, oxidative stress and G₂/M transition. Annexin 4 (ANXA4) and superoxide dismutase 2 (SOD2), involved in apoptosis and oxidative stress, respectively, were chosen to validate the SILAC analysis and may represent potential therapeutic targets for lung cancer treatment. In conclusion, the chemosensitizing and antiproliferative effects of MET were associated with mTOR signaling and with potential novel targets, such as ANXA4 and SOD2, in human lung cancer cells.

Effect of Menadione and Combination of Gemcitabine and Cisplatin on Cancer Stem Cells in Human Non-small Cell Lung Cancer (NSCLC) Cell Line A549

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer. Chemotherapy-induced adverse effects and resistance of NSCLC to conventional drugs reduce the efficacy of current therapies. Tumors contain a small population of cancer stem cells (CSCs) that play a critical role in tumor initiation, maintenance, and drug resistance that finally lead to cancer recurrence. Therefore, CSC-targeting therapies can offer the best hope for developing curative cancer therapies. Vitamins have a high potential for cancer prevention and treatment. Vitamins also ameliorate the side effects which occur in chemo-radio therapy. Menadione (2-methyl-1,4-naphthoquinone/vitamin-K3) is a synthetic form of vitamin K that indicated antitumor activities. The purpose of this study was to evaluate the anti-CSCs effect of menadione and combination of cisplatin and gemcitabine as a first-line treatment in patients with NSCLC on the NSCLC cell line A549. MTT results displayed decreased cell survival after treatment with cisplatin/gemcitabine for 48 h treatment (IC₅₀ values 0.25 µM for cisplatin and 5 µM for gemcitabine). Menadione also inhibited the cell growth in A549 cells (IC₅₀: 16 µM). Quantitative RT-PCR showed significant downregulation of CSC markers (Oct4, Nanog, Sox2, Aldh1, Abcb1, CD44, and CD133) and Snail, epithelial-mesenchymal transition marker, after treatment with menadione and cisplatin/gemcitabine. Flow cytometry showed CD44-positive cells that constitute a high percentage (70%) of A549 cells reduced significantly after treatment with cisplatin/gemcitabine or menadione. However, A549 cells did not show a significant population positive for CD133 and ABCB1 (less than 0.05%), and these fractions did not change after treatment with two agents.

Arsenic trioxide inhibits the growth of cancer stem cells derived from small cell lung cancer by downregulating stem cell-maintenance factors and inducing apoptosis via the Hedgehog signaling blockade

Background

Small cell lung cancer (SCLC) is the most deadly and aggressive type of primary lung cancer, with the 5-year survival rate lower than 5%. The FDA has approved arsenic trioxide (As₂O₃) for acute promyelocytic leukemia (APL) treatment. However, its role in SCLC-derived cancer stem cells (CSCs) remains largely unknown.

Methods

CSCs were enriched from SCLC cell lines by culturing them as spheres in conditioned serum-free medium. Then, qPCR, western blot, serial passage, limiting dilution, Transwell, and tumorigenesis assay were performed to verify the cells' stem phenotypic characteristics. Anticancer efficiency of As₂O₃ was assessed in these cells using CCK8, colony formation, sphere formation, flow cytometry, qPCR, western blot analysis in vitro, and tumor growth curve, immunofluorescence, and TUNEL staining analyses in vivo.

Results

The fifth-passage SCLC spheres showed a potent self-renewal capacity, higher clonal formation efficiency (CFE), SOX2, c-Myc, NANOG, and OCT4 levels, and invasion ability, and stronger tumorigenesis capacity than the parental SCLC cells, indicating that the SCLC sphere cells displayed CSC features. As₂O₃ inhibited the proliferation, clonality and sphere forming ability of SCLC-derived CSCs and suppressed the tumor growth of CSCs-derived xenograft tumors. As₂O₃ induced apoptosis and downregulation of SOX2 and c-Myc in vitro and in xenografts. Besides, SOX2 knockdown suppressed SCLC-derived CSCs to self-renew and induced apoptosis. Mechanistically, expression of GLI1 (a key transcription factor of Hedgehog pathway) and its downstream genes increased in SCLC-derived CSCs, compared to the parental cells. As₂O₃ dramatically downregulated GLI1 and its downstream genes in vitro and in vivo. The GLI inhibitor (GANT-61) recapitulated and enhanced the effects of As₂O₃ on SCLC-derived CSCs, including growth suppression, apoptosis induction, and GLI1, SOX2 and c-Myc downregulation.

Conclusions

Altogether, As₂O₃ effectively suppressed SCLC-derived CSCs growth by downregulating stem cell-maintenance factors and inducing apoptosis. These effects are mediated at least partly via the Hedgehog signaling blockade.

DNA-PK in human malignant disorders: Mechanisms and implications for pharmacological interventions

The DNA-PK holoenzyme is a fundamental element of the DNA damage response machinery (DDR), which is responsible for cellular genomic stability. Consequently, and predictably, over the last decades since its identification and characterization, numerous pre-clinical and clinical studies reported observations correlating aberrant DNA-PK status and activity with cancer onset, progression and responses to therapeutic modalities. Notably, various studies have established in recent years the role of DNA-PK outside the DDR network, corroborating its role as a pleiotropic complex involved in transcriptional programs that operate biologic processes as epithelial to mesenchymal transition (EMT), hypoxia, metabolism, nuclear receptors signaling and inflammatory responses. In particular tumor entities as prostate cancer, immense research efforts assisted mapping and describing the overall signaling networks regulated by DNA-PK that control metastasis and tumor progression. Correspondingly, DNA-PK emerges as an obvious therapeutic target in cancer and data pertaining to various pharmacological approaches have been published, largely in context of combination with DNA-damaging agents (DDAs) that act by inflicting DNA double strand breaks (DSBs). Currently, new generation inhibitors are tested in clinical trials. Several excellent reviews have been published in recent years covering the biology of DNA-PK and its role in cancer. In the current article we are aiming to systematically describe the main findings on DNA-PK signaling in major cancer types, focusing on both preclinical and clinical reports and present a detailed current status of the DNA-PK inhibitors repertoire.

Targeting lipid droplet lysophosphatidylcholine for cisplatin chemotherapy

This study aims to explore lipidic mechanism towards low‐density lipoprotein receptor (LDLR)‐mediated platinum chemotherapy resistance. By using the lipid profiling technology, LDLR knockdown was found to increase lysosomal lipids and decrease membranous lipid levels in EOC cells. LDLR knockdown also down‐regulated ether‐linked phosphatidylethanolamine (PE‐O, lysosomes or peroxisomes) and up‐regulated lysophosphatidylcholine [LPC, lipid droplet (LD)]. This implies that the manner of using Lands cycle (conversion of lysophospholipids) for LDs might affect cisplatin sensitivity. The bioinformatics analyses illustrated that LDLR‐related lipid entry into LD, rather than an endogenous lipid resource (eg Kennedy pathway), controls the EOC prognosis of platinum chemotherapy patients. Moreover, LDLR knockdown increased the number of platinum‐DNA adducts and reduced the LD platinum amount. By using a manufactured LPC‐liposome‐cisplatin (LLC) drug, the number of platinum‐DNA adducts increased significantly in LLC‐treated insensitive cells. Moreover, the cisplatin content in LDs increased upon LLC treatment. Furthermore, lipid profiles of 22 carcinoma cells with differential cisplatin sensitivity (9 sensitive vs 13 insensitive) were acquired. These profiles revealed low storage lipid levels in insensitive cells. This result recommends that LD lipidome might be a common pathway in multiple cancers for platinum sensitivity in EOC. Finally, LLC suppressed both cisplatin‐insensitive human carcinoma cell training and testing sets. Thus, LDLR‐platinum insensitivity can be due to a defective Lands cycle that hinders LPC production in LDs. Using lipidome assessment with the newly formulated LLC can be a promising cancer chemotherapy method.

Alpha Radiation as a Way to Target Heterochromatic and Gamma Radiation-Exposed Breast Cancer Cells

Compact chromatin is linked to a poor tumour prognosis and resistance to radiotherapy from photons. We investigated DNA damage induction and repair in the context of chromatin structure for densely ionising alpha radiation as well as its therapeutic potential. Chromatin opening by histone deacetylase inhibitor trichostatin A (TSA) pretreatment reduced clonogenic survival and increased γH2AX foci in MDA-MB-231 cells, indicative of increased damage induction by free radicals using gamma radiation. In contrast, TSA pretreatment tended to improve survival after alpha radiation while γH2AX foci were similar or lower; therefore, an increased DNA repair is suggested due to increased access of repair proteins. MDA-MB-231 cells exposed to fractionated gamma radiation (2 Gy × 6) expressed high levels of stem cell markers, elevated heterochromatin H3K9me3 marker, and a trend towards reduced clonogenic survival in response to alpha radiation. There was a higher level of H3K9me3 at baseline, and the ratio of DNA damage induced by alpha vs. gamma radiation was higher in the aggressive MDA-MB-231 cells compared to hormone receptor-positive MCF7 cells. We demonstrate that heterochromatin structure and stemness properties are induced by fractionated radiation exposure. Gamma radiation-exposed cells may be targeted using alpha radiation, and we provide a mechanistic basis for the involvement of chromatin in these effects.

NVP-BSK805, an Inhibitor of JAK2 Kinase, Significantly Enhances the Radiosensitivity of Esophageal Squamous Cell Carcinoma in vitro and in vivo

Purpose

Radiotherapy is one major curative treatment modality for esophageal squamous cell carcinoma (ESCC) patients. This study aimed to find out small-molecular kinase inhibitors, which can significantly enhance the radiosensitivity of ESCC in vitro and in vivo.

Materials and Methods

Ninety-three kinase inhibitors were tested for their radiosensitizing effect in ESCC cells through high-content screening. The radiosensitizing effect of kinase inhibitors was investigated in vitro by detection of DNA double-strand breaks (DSBs) and clonogenic survival assay. By the establishment of xenograft tumor models in BALB/c nude mice, the radiosensitizing effect of kinase inhibitors was investigated in vivo.

Results

Among the 93 kinase inhibitors tested, we found NVP-BSK805, an inhibitor of JAK2 kinase, significantly radiosensitized ESCC cells through enhancing DSBs, inhibiting DNA damage repair and arresting cell cycle in G2/M or G0/G1 phase. After treatment with NVP-BSK805, ESCC cells showed decreased clonogenic survival and delayed tumor growth in vivo. JAK2 kinase was highly expressed in tumor tissues of ESCC patients, while rarely expressed in matched normal esophageal epithelial tissues. Survival analysis revealed JAK2 kinase as a prognostic factor of ESCC patients treated with chemoradiotherapy.

Conclusion

Our study discovered JAK2 kinase as an attractive target to enhance the radiosensitivity of ESCC cells in vitro and in vivo.

Role of Rad51 and DNA repair in cancer: A molecular perspective

The maintenance of genome integrity is essential for any organism survival and for the inheritance of traits to offspring. To the purpose, cells have developed a complex DNA repair system to defend the genetic information against both endogenous and exogenous sources of damage. Accordingly, multiple repair pathways can be aroused from the diverse forms of DNA lesions, which can be effective per se or via crosstalk with others to complete the whole DNA repair process. Deficiencies in DNA healing resulting in faulty repair and/or prolonged DNA damage can lead to genes mutations, chromosome rearrangements, genomic instability, and finally carcinogenesis and/or cancer progression. Although it might seem paradoxical, at the same time such defects in DNA repair pathways may have therapeutic implications for potential clinical practice. Here we provide an overview of the main DNA repair pathways, with special focus on the role played by homologous repair and the RAD51 recombinase protein in the cellular DNA damage response. We next discuss the recombinase structure and function per se and in combination with all its principal mediators and regulators. Finally, we conclude with an analysis of the manifold roles that RAD51 plays in carcinogenesis, cancer progression and anticancer drug resistance, and conclude this work with a survey of the most promising therapeutic strategies aimed at targeting RAD51 in experimental oncology.

DNA damage response and resistance of cancer stem cells

The cancer stem cell (CSC) model defines tumors as hierarchically organized entities, containing a small population of tumorigenic CSC, or tumour-initiating cells, placed at the apex of this hierarchy. These cells may share common qualities with chemo- and radio-resistant cancer cells and contribute to self-renewal activities resulting in tumour formation, maintenance, growth and metastasis. Yet, it remains obscure what self-defense mechanisms are utilized by these cells against the chemotherapeutic drugs or radiotherapy. Recently, attention has been focused on the pivotal role of the DNA damage response (DDR) in tumorigenesis. In line with this note, an increased DDR that prevents CSC and chemoresistant cells from genotoxic pressure of chemotherapeutic drugs or radiation may be responsible for cancer metastasis. In this review, we focus on the current knowledge concerning the role of DDR in CSC and resistant cancer cells and describe the existing opportunities of re-sensitizing such cells to modulate therapeutic treatment effects.

Cisplatin-resistant A549 non-small cell lung cancer cells can be identified by increased mitochondrial mass and are sensitive to pemetrexed treatment

Background

Cisplatin plus pemetrexed combination therapy is considered the standard treatment for patients with advanced, non-squamous, non-small-cell lung cancer (NSCLC). However, advanced NSCLC has a 5-year survival rate of below 10%, which is mainly due to therapy resistance. We previously showed that the NSCLC cell line A549 harbors different subpopulations including a mesenchymal-like subpopulation characterized by increased chemo- and radiotherapy resistance. Recently, therapy resistance in hematological and solid tumors has been associated with increased mitochondrial activity. Thus, the aim of this study was to investigate the role of the mitochondrial activity in NSCLC chemotherapy resistance.

Methods

Based on MitoTracker staining, subpopulations characterized by the highest 10% (Mito-High) or lowest 10% (Mito-Low) mitochondrial mass content were sorted by FACS (Fluorescence-Activated Cell Sorting) from paraclonal cultures of the NSCLC A549 cell line . Mitochondrial DNA copy numbers were quantified by real-time PCR whereas basal cellular respiration was measured by high-resolution respirometry. Cisplatin and pemetrexed response were quantified by proliferation and colony formation assay.

Results

Pemetrexed treatment of parental A549 cells increased mitochondrial mass over time. FACS-sorted paraclonal Mito-High cells featured increased mitochondrial mass and mitochondrial DNA copy number compared to the Mito-Low cells. Paraclonal Mito-High cells featured an increased proliferation rate and were significantly more resistant to cisplatin treatment than Mito-Low cells. Interestingly, cisplatin-resistant, paraclonal Mito-High cells were significantly more sensitive to pemetrexed treatment than Mito-Low cells. We provide a working model explaining the molecular mechanism underlying the increased cisplatin- and decreased pemetrexed resistance of a distinct subpopulation characterized by high mitochondrial mass.

Conclusions

This study revealed that cisplatin resistant A549 lung cancer cells can be identified by their increased levels of mitochondrial mass. However, Mito-High cells feature an increased sensitivity to pemetrexed treatment. Thus, pemetrexed and cisplatin target reciprocal lung cancer subpopulations, which could explain the increased efficacy of the combination therapy in the clinical setting.

Cancer Stem Cells and Radioresistance: DNA Repair and Beyond

The current preclinical and clinical findings demonstrate that, in addition to the conventional clinical and pathological indicators that have a prognostic value in radiation oncology, the number of cancer stem cells (CSCs) and their inherent radioresistance are important parameters for local control after radiotherapy. In this review, we discuss the molecular mechanisms of CSC radioresistance attributable to DNA repair mechanisms and the development of CSC-targeted therapies for tumor radiosensitization. We also discuss the current challenges in preclinical and translational CSC research including the high inter- and intratumoral heterogeneity, plasticity of CSCs, and microenvironment-stimulated tumor cell reprogramming.

Cancer Stem Cells from Tumor Cell Lines Activate the DNA Damage Response Pathway after Ionizing Radiation More Efficiently Than Noncancer Stem Cells

Recently, a subpopulation of tumor cells, called cancer stem cells (CSC), has been characterized, and these have emerged as a major topic in cancer research. CSC are proposed to repair DNA damage more efficiently than the rest of tumor cells, resisting chemotherapy or radiotherapy and causing clinical recurrence and metastasis. We aimed to determine the molecular basis of radioresistance and first compared the response to ionizing radiation (IR) between cancer stem cell-enriched cultures grown as spheres and conventional tumor cell line cultures grown as monolayer, from HeLa and MCF-7 cancer cell lines. To verify that our sphere cultures were enriched in CSC, we evaluated the double staining of CD49f and ALDH activity for HeLa cells by flow cytometry. We then evaluated whether differences could exist in sensor elements in the DNA damage response pathway among these cultures. We found that CSC cultures showed less sensitivity to radiation than conventional tumor cell line cultures. We observed a higher baseline expression of activated response sensor proteins of DNA damage, such as ATM, H2A.X, and PARP1, in untreated CSC cultures. These findings provide the first evidence, to our knowledge, that DNA damage response sensor proteins are present and preferentially activated in CSC, as opposed to the bulk of cells in monolayer cultures. Likewise, they provide the basis for biological differences in response to IR between CSC and other tumor cell populations. Understanding the DNA damage response pathway may provide therapeutic targets to sensitize CSC to cytotoxic therapies to improve current cancer treatments.

Freeware tool for analysing numbers and sizes of cell colonies

The clonogenic cell survival assay is a basic method to study the cytotoxic effect of radiation and chemical toxins. In large experimental setups, counting of colonies by eye is tiresome and prone to bias. Moreover, it is often interesting to quantify the size of individual colonies. Such analyses are largely facilitated by computerised image analysis systems. Although a number of such systems exist, they all focus on enumerating colonies and not on analysing the colony size. We have developed a new software package for both counting colonies and plotting their size distributions. The software called count and Plot HIstograms of Colony Size (countPHICS) consists of two parts: (1) a macro written for ImageJ which analyses computerised images of cell culture dishes or 6-well plates, counts colonies, estimates their size and saves the results in a text file; (2) a program written with QT Creator which reads the text file, plots histograms of colony size distribution and fits the best function. The full program is freely available at: http://www.fuw.edu.pl/~bbrzozow/FizMed/countPHICS.html . In conclusion, our new publically available software will facilitate colony counting and provide additional information on the colony growth rate, which is relevant especially for radiosensitisation studies.

Nanomedicine-Assisted Combination Therapy of NSCLC: New Platinum-Based Anticancer Drug Synergizes the Therapeutic Efficacy of Ganetespib

Purpose: K-RAS is the most common mutated oncogene associated with Non-Small-Cell Lung Cancer (NSCLC). So far, there are no promising chemotherapies for the direct inhibition of K-RAS, and considered to be undruggable. In this work, we have introduced a new platinum-based cyanoximate complex, Pt(MCO)2, as an anti-cancer drug to enhance the therapeutic efficacy of Hsp90 inhibitor drug, ganetespib for the combination therapy of NSCLC. Methods: We have synthesized polyacrylic acid (PAA)-coated magnetic nanoparticles (MNPs) and used as drug delivery system. These MNPs were decorated with folic acid in order to target folate receptor-expressing NSCLC. The individual and combination of drugs as well as an optical dye DiI were co-encapsulated successfully inside the PAA-coating of MNPs to evaluate synergistic treatment option for NSCLC. The magnetic resonance (MR) and optical imaging modalities assisted for the monitoring drug loading and NSCLC treatment. Results: To evaluate the therapeutic efficacy of these customized MNPs, various cell-based assays including cell viability, apoptosis and necrosis, cell migration, comet and ROS experiments were performed. Results showed minimal toxicity for functional MNPs with no therapeutic drug and more than 60% cell death within 48 h of treatment, when single drug was encapsulated. Importantly, more than 90% cells were dead when both drugs were delivered. Overall, the results indicated that the Pt(MCO)2 drug enhances the therapeutic efficacy of ganetespib by more than 30% toxicity towards the targeted treatment of NSCLC, while showed minimal toxicity to the normal healthy tissues. Conclusion: We successfully developed new dual-modal magnetic nanomedicines for the rapid and controlled release of combination of drugs for the effective treatment of NSCLC. The MR and fluorescence modalities help monitoring the delivery of drugs, where the new platinum-based drug Pt(MCO)2 synergizes the therapeutic efficacy of ganetespib.

DNA repair as an emerging target for COPD-lung cancer overlap

Cigarette smoking is the leading cause of lung cancer and chronic obstructive pulmonary disease (COPD). Many of the detrimental effects of cigarette smoke have been attributed to the development of DNA damage, either directly from chemicals contained in cigarette smoke or as a product of cigarette smoke-induced inflammation and oxidative stress. In this review, we discuss the environmental, epidemiological, and physiological links between COPD and lung cancer and the likely role of DNA damage and repair in COPD and lung cancer development. We explore alterations in DNA damage repair by DNA repair proteins and pathways. We discuss emerging data supporting a key role for the DNA repair protein, xeroderma pigmentosum group C (XPC), in cigarette smoke-induced COPD and early lung cancer development. Understanding the interplay between cigarette smoke, DNA damage repair, COPD, and lung cancer may lead to prognostic tools and new, potentially targetable, pathways for lung cancer prevention and treatment.

Tumor Initiation Capacity and Therapy Resistance Are Differential Features of EMT-Related Subpopulations in the NSCLC Cell Line A549

Cell lines are essential tools to standardize and compare experimental findings in basic and translational cancer research. The current dogma states that cancer stem cells feature an increased tumor initiation capacity and are also chemoresistant. Here, we identified and comprehensively characterized three morphologically distinct cellular subtypes in the non–small cell lung cancer cell line A549 and challenge the current cancer stem cell dogma. Subtype-specific cellular morphology is maintained during short-term culturing, resulting in the formation of holoclonal, meroclonal, and paraclonal colonies. A549 holoclone cells were characterized by an epithelial and stem-like phenotype, paraclone cells featured a mesenchymal phenotype, whereas meroclone cells were phenotypically intermediate. Cell-surface marker expression of subpopulations changed over time, indicating an active epithelial-to-mesenchymal transition (EMT), in vitro and in vivo. EMT has been associated with the overexpression of the immunomodulators PD-L1 and PD-L2, which were 37- and 235-fold overexpressed in para- versus holoclone cells, respectively. We found that DNA methylation is involved in epigenetic regulation of marker expression. Holoclone cells were extremely sensitive to cisplatin and radiotherapy in vitro, whereas paraclone cells were highly resistant. However, inhibition of the receptor tyrosine kinase AXL, whose expression is associated with an EMT, specifically targeted the otherwise highly resistant paraclone cells. Xenograft tumor formation capacity was 24- and 269-fold higher in holo- than mero- and paraclone cells, respectively. Our results show that A549 subpopulations might serve as a unique system to explore the network of stemness, cellular plasticity, tumor initiation capacity, invasive and metastatic potential, and chemo/radiotherapy resistance.

Calcium channel α2δ1 subunit (CACNA2D1) enhances radioresistance in cancer stem-like cells in non-small cell lung cancer cell lines

Purpose

Radiotherapy is a major treatment method for patients with non-small cell lung cancer (NSCLC). However, the presence of radioresistant cancer stem cells (CSCs) may be associated with disease relapse or a poor outcome after radiotherapy. Voltage-gated calcium channel α2δ1 subunit (encoded by the gene CACNA2D1) isoform 5 is a marker of CSCs in hepatocellular carcinoma. This study aimed to investigate the radiosensitivity of α2δ1-high cells in NSCLC cell lines.

Materials and methods

NSCLC cell lines A549, H1975, H1299, and PC9 were used. CACNA2D1-knockdown and CACNA2D1-overexpressing cell lines were established by lentiviral infection. Colony formation assay was performed to determine radiosensitivity. Sphere formation assay in serum-free medium was performed to evaluate self-renewal capacity. Proteins associated with DNA damage repair were analyzed by immunofluorescence or Western blot. The monoclonal antibody of α2δ1 was applied alone or in combination with radiation either in vitro or in vivo to determine the anti-tumor effect of the antibody.

Results

α2δ1-high cells showed greater sphere-forming efficiency than α2δ1-low cells and were relatively resistant to radiation. CACNA2D1 knockdown in A549 cells enhanced radiosensitivity, whereas CACNA2D1 overexpression in PC9 and H1975 cells reduced radiosensitivity, suggesting that α2δ1 imparted radioresistance to NSCLC cells. Analysis of proteins involved in DNA damage repair suggested that α2δ1 enhanced the efficiency of DNA damage repair. The monoclonal antibody of α2δ1 had a synergistic effect with that of radiation to block the self-renewal of α2δ1-high cells and enhanced the radiosensitivity of α2δ1-positive cells in colony formation assays. The combination of the α2δ1 antibody with radiation repressed A549 xenograft growth in vivo.

Conclusion

α2δ1 enhances radioresistance in cancer stem-like cells in NSCLC. The α2δ1 monoclonal antibody sensitizes α2δ1-high cells to radiation, suggesting that the antibody may be used to improve the treatment outcome when combined with radiation in NSCLC.

MicroRNA-122 negatively associates with peroxiredoxin-II expression in human gefitinib-resistant lung cancer stem cells

Previously, we demonstrated that Prx II is important for survival of the gefitinib-resistant A549 (A549/GR) cell line, an NSCLC cell line derived by repeated exposure to gefitinib. Therefore, in this study, we used A549/GR cells to investigate the role of Prx II in GR NSCLC stemness. Initially, to explore the stemness characteristics and investigate the association of Prx II with those stemness characteristics, we successfully isolated a stem cell-like population from A549/GR cells. A549/GR CD133⁺ cells possessed important cancer stemness characteristics, including the abilities to undergo metastasis, angiogenesis, self-renewal, and to express stemness genes and epithelial–mesenchymal transition (EMT) markers. However, those characteristics were abolished by knocking down Prx II expression. MicroRNA 122 (miR-122) targets Prx II in A549/GR cancer stem cells (CSCs), thereby inhibiting the stemness characteristics in vitro and in vivo. Next, we investigate whether miR-122 overexpression was associated with Prx II expression and Prx-II-induced stemness characteristics, we transfected miR-122 into A549/GR CSCs. MiR-122 inhibited A549/GR stemness by downregulating the Hedgehog, Notch, and Wnt/β-catenin pathways. Taken together, our data suggest that Prx II promotes A549/GR stemness, and that targeting Prx II and miR-122 is a potentially viable strategy for anti-cancer-stem cell therapy in GR NSCLCs.

SOX2, a stemness gene, induces progression of NSCLC A549 cells toward anchorage-independent growth and chemoresistance to vinblastine

Background

Non-small cell lung cancer (NSCLC) is difficult to treat successfully. This intractability is mainly due to the cancer progressing through invasion, metastasis, chemotherapeutic resistance and relapse. Stemness has been linked to the various steps of cancer progression in a variety of tumors, yet little is known regarding its role in NSCLC.

Purpose

In this study, we sought to determine the role of SOX2, a master regulator of pluripotency, in the growth of extracellular matrix (ECM)-detached cells during cancer progression.

Methods

We established a three-dimensional (3D) Poly-2-hydroxyethyl methacrylate (poly-HEMA) culture of lung adenocarcinoma (LUAD) A549 cells as an ECM-detached cell growth model and examined the role of stemness genes using siRNA and small molecule inhibitor in comparison to standard two dimensional (2D) culture.

Results

In poly-HEMA culture, A549 cells formed substratum-detached spheroids with characteristics of intermediate epithelial to mesenchymal transition (EMT) and exhibited greater expression of SOX2 than did control 2D cells. Knockdown of SOX2 markedly suppressed the growth of A549 cell aggregates in poly-HEMA culture conditions and furthermore increased their sensitivity to the anticancer drug vinblastine with concomitant downregulation of the activity of the anti-apoptotic AKT kinase. Interestingly, a small molecule, RepSox, which replaces SOX2, stimulated A549 cell growth in poly-HEMA 3D culture condition.

Conclusion

Our findings strongly indicate that SOX2 contributes to anchorage-independent growth and chemoresistance via its downstream signaling mediator AKT kinase during the disease progression of NSCLC. SOX2 may therefore be an invaluable therapeutic target of NSCLC.

Replication stress response in cancer stem cells as a target for chemotherapy

Cancer stem cells (CSCs) are subpopulations of multipotent stem cells (SCs) responsible for the initiation, long-term clonal maintenance, growth and spreading of most human neoplasms. Reportedly, CSCs share a very robust DNA damage response (DDR) with embryonic and adult SCs, which allows them to survive endogenous and exogenous genotoxins. A range of experimental evidence indicates that CSCs have high but heterogeneous levels of replication stress (RS), arising from, and being boosted by, endogenous causes, such as specific genetic backgrounds (e.g., p53 deficiency) and/or aberrant karyotypes (e.g., supernumerary chromosomes). A multipronged RS response (RSR) is put in place by CSCs to limit and ensure tolerability to RS. The characteristics of such dedicated cascade have two opposite consequences, both relevant for cancer therapy. On the one hand, RSR efficiency often increases the reliance of CSCs on specific DDR components. On the other hand, the functional redundancy of pathways of the RSR can paradoxically promote the acquisition of resistance to RS- and/or DNA damage-inducing agents. Here, we provide an overview of the molecular mechanisms of the RSR in cancer cells and CSCs, focusing on the role of CHK1 and some emerging players, such as PARP1 and components of the homologous recombination repair, whose targeting can represent a long-term effective anti-CSC strategy.

KAP1 inhibits the Raf-MEK-ERK pathway to promote tumorigenesis in A549 lung cancer cells

Aberrant activation of the Raf-MEK-ERK pathway has frequently been associated with various cancers, especially lung cancer. However, the key regulators of this pathway are largely unknown. Using functional proteomics screening, we found that KAP1 interacts with c-Raf. Knocking out KAP1 decreased c-Raf phosphorylation at serine 259 and increased its phosphorylation at serine 338, which activated MEK and ERK. We detected higher KAP1 expression in lung cancer tissues than in normal peri-tumoral tissues. KAP1 knockdown arrested A549 lung cancer cells in the G0/G1 phase of the cell cycle and attenuated cell growth, metastasis, the epithelial-mesenchymal transition, angiogenesis, stemness, and colony formation. Furthermore, knocking out KAP1 remarkably increased the susceptibility of A549 cells to the anti-cancer drug 5-Fluorouracil, which correlated with increasing ERK phosphorylation. In vivo xenograft experiments suggested that KAP1 deficiency significantly decreases the tumorigenicity of A549 cells. Taken together, our findings indicate that KAP1 acts as a key module in the c-Raf-interactome complex and regulates lung cancer development through the Raf-MEK-ERK pathway. Therefore, KAP1 may represent a potential diagnosis biomarker and new treatment target for lung cancer.

Inhibiting polo-like kinase 1 enhances radiosensitization via modulating DNA repair proteins in non-small-cell lung cancer

To assure faithful chromosome segregation, cells make use of the spindle assembly checkpoint, which can be activated in aneuploid cancer cells. In this study, the efficacies of inhibiting polo-like kinase 1 (PLK1) on the radiosensitization of non-small-cell lung cancer (NSCLC) cells were studied. Clonogenic survival assay was performed to identify the effects of the PLK1 inhibitor on radiosensitivity within NSCLC cells. Mitotic catastrophe assessment was used to measure the cell death and histone H2AX protein (γH2AX) foci were utilized to assess the DNA double-strand breaks (DSB). The transcriptome was analyzed via unbiased profiling of microarray expression. The results showed that the postradiation mitotic catastrophe induction and the DSB repair were induced by PLK1 inhibitor BI-6727, leading to an increase in the radiosensitivity of NSCLC cells. BI-6727 in combination with radiation significantly induced the delayed tumor growth. PLK1-silenced NSCLC cells showed an altered mRNA and protein expression related to DNA damaging, replication, and repairing, including the DNA-dependent protein kinase (DNAPK) and topoisomerase II alpha (TOPO2A). Furthermore, inhibition of PLK1 blocked 2 important DNA repair pathways. To summarize, our study showed PLK1 kinase as an option in the therapy of NSCLC.

Hypothermia modulates the DNA damage response to ionizing radiation in human peripheral blood lymphocytes

PURPOSE

Low temperature at exposure has been shown to act in a radioprotective manner at the level of cytogenetic damage. It was suggested to be due to an effective transformation of DNA damage to chromosomal damage at low temperature. The purpose of the study was to analyze the kinetics of aberration formation during the first hours after exposing human peripheral blood lymphocytes to ionizing radiation at 0.8 °C and 37 °C.

MATERIALS AND METHODS

To this end, we applied the technique of premature chromosome condensation. In addition, DNA damage response was analyzed by measuring the levels of phosphorylated DNA damage responsive proteins ATM, DNA-PK and p53 and mRNA levels of the radiation-responsive genes BBC3, FDXR, GADD45A, XPC, MDM2 and CDKN1A.

RESULTS

A consistently lower frequency of chromosomal breaks was observed in cells exposed at 0.8 °C as compared to 37 °C already after 30 minutes postexposure. This effect was accompanied by elevated levels of phosphorylated ATM and DNA-PK proteins and a reduced immediate level of phosphorylated p53 and of the responsive genes.

CONCLUSIONS

Low temperature at exposure appears to promote DNA repair leading to reduced transformation of DNA damage to chromosomal aberrations.

Reactive Oxygen Species-Mediated Autophagy Defines the Fate of Cancer Stem Cells

Significance: A fraction of tumorigenic cells, also known as tumor initiating or cancer stem cells (CSCs), is thought to drive tumor growth, metastasis, and chemoresistance. However, little is known regarding mechanisms that convey relevant pathways contributing to their self-renewal, proliferation, and differentiation abilities. Recent Advances: Recent works on CSCs provide evidence on the role of redox disruption and regulation of autophagic flux. This has been linked to increased DNA repair capacity and chemoresistance. Critical Issues: The current review summarizes the most recent studies assessing the role of redox homeostasis, autophagy, and chemoresistance in CSCs, including some novel findings on microRNAs and their role in horizontal transfer within cancer cell populations. Future Directions: Rational anticancer therapy and prevention should rely on the fact that cancer is a redox disease with the CSCs being the apex modulated by redox-mediated autophagy. Antioxid. Redox Signal. 28, 1066-1079.

Ecto-5'-nucleotidase (CD73) is a biomarker for clear cell renal carcinoma stem-like cells

Identification of a specific biomarker for cancer stem cells (CSCs) is of potential applications in the development of effective therapeutic strategies for renal cell carcinoma (RCC). In this study, both the RCC cell line 786-O and surgically removed clear cell RCC (ccRCC) tissues were implemented to grew as spheroids in serum-free medium supplemented with mitogens. This subpopulation possessed key characteristics defining CSCs. We also identified that surgically removed ccRCC tissues were heterogenic and there was a subpopulation of cells that was highly stained with rhodamine-123. Based on membrane-proteomic analyses, CD73 was identified as a candidate biomarker. We further found that CD73high cells were highly tumorigenic. As few as 100 CD73high cells were capable of forming xenograft tumors in non obese diabetic/severe combined immunodeficiency disease mice, whereas 1 × 105 CD73low cells did not initiate tumor formation. During successive culture, the CD73high population regenerated both CD73high and CD73low cells, whereas the CD73low population remained low expression level of CD73. Furthermore, the CD73high cells were more resistant to radiation and DNA-damaging agents than the CD73low cells, and expressed a panel of 'stemness' genes at a higher level than the CD73low cells. These findings suggest that a high level of CD73 expression is a bona fide biomarker of ccRCC stem-like cells. Future research will aim at the elucidation of the underlying mechanisms of CD73 in RCC development and the distinct aspects of ccRCC stem-like cells from other tumor types.

Effects of Aptamer to U87-EGFRvIII Cells on the Proliferation, Radiosensitivity, and Radiotherapy of Glioblastoma Cells

Glioblastoma multiforme (GBM) is the most prevalent and lethal malignant intracranial tumor in the brain, with very poor prognosis and survival. The epidermal growth factor receptor variant III (EGFRvIII) contributes to increased oncogenicity that does not occur through binding EGFR ligands and instead occurs through constitutive activation, which enhances glioma tumorigenicity and resistance to targeted therapy. Aptamers are nucleic acids with high affinity and specificity to targets selected by systematic evolution of ligands by exponential enrichment (SELEX), and are usually developed as antagonists of disease-associated factors. Herein, we generated a DNA aptamer U2, targeting U87-EGFRvIII cells, and demonstrated that U2 alters the U87-EGFRvIII cell growth, radiosensitivity, and radiotherapy of glioblastoma cells. We detected U2 and U87-EGFRvIII cells by flow cytometry and confocal microscopy to explore the binding ability of U2 to U87-EGFRvIII cells. Then, we found that aptamer U2 inhibits the proliferation, migration, invasion, and downstream signaling of U87-EGFRvIII cells. Moreover, the U2 aptamer can increase the radiosensitivity of U87-EGFRvIII in vitro and has a better antitumor effect on 188Re-U2 in vivo. Therefore, the results revealed the promising potential of the U2 aptamer to be a new type of drug candidate and aptamer-targeted drug delivery system for glioblastoma therapy.

Targeting hyperactivated DNA-PKcs by KU0060648 inhibits glioma progression and enhances temozolomide therapy via suppression of AKT signaling

The overall survival remains undesirable in clinical glioma treatment. Inhibition of DNA-PKcs activity by its inhibitors suppresses tumor growth and enhances chemosensitivity of several tumors to chemotherapy. However, whether DNA-PKcs could be a potential target in glioma therapy remains unknown. In this study, we reported that the hyperactivated DNA-PKcs was profoundly correlated with glioma malignancy and observe a significant association between DNA-PKcs activation and survival of the glioma patients. Our data also found that inhibition of DNA-PKcs by its inhibitor KU0060648 sensitized glioma cells to TMZ in vitro. Specifically, we demonstrated that KU0060648 interrupted the formation of DNA-PKcs/AKT complex, leading to suppression of AKT signaling and resultantly enhanced TMZ efficacy. Combination of KU0060648 and TMZ substantially inhibited downstream effectors of AKT. The in vivo results were similar to those obtained in vitro. In conclusion, this study indicated that inhibition of DNA-PKcs activity could suppress glioma malignancies and increase TMZ efficacy, which was mainly through regulation of the of AKT signaling. Therefore, DNA-PKcs/AKT axis may be a promising target for improving current glioma therapy.

Studies of lncRNAs in DNA double strand break repair: what is new?

The ‘junk DNA’ that has haunted human genetics for a long time now turns out to hold enormous hidden treasures. As species had their genomes and transcriptomes sequenced, there are an overwhelming number of lncRNA transcripts being reported, however, less than 100 of them have been functionally characterized. DNA damage is recognized and quickly repaired by the cell, with increased expression of numerous genes involved in DNA repair. Most of the time the studies have focused only on proteins involved in these signaling pathways. However, recent studies have implied that lncRNAs can be broadly induced by DNA damage and regulate DNA repair processes by various mechanisms. In this paper, we focus on recent advances in the identification and functional characterization of novel lncRNAs participating in DNA double strand break repair.

Analysis of Chromatin Opening in Heterochromatic Non-Small Cell Lung Cancer Tumor-Initiating Cells in Relation to DNA-Damaging Antitumor Treatment

PURPOSE

We previously reported that sphere-forming non-small cell lung cancer (NSCLC) tumor-initiating cells (TICs) have an altered activation of DNA damage response- and repair proteins and are refractory to DNA-damaging treatments. We analyzed whether chromatin organization plays a role in the observed refractoriness.

METHODS AND MATERIALS

Bulk cells and TICs from the NSCLC H23 and H1299 cell lines were examined using cell viability, clonogenic survival, Western blot, short interfering RNA analysis, and micronucleus assay.

RESULTS

NSCLC TICs displayed elevated heterochromatin markers trimethylated lysine 9 of histone H3 and heterochromatin protein 1γ relative to bulk cells and reduced cell viability upon histone deacetylase inhibition (HDACi). Vorinostat and trichostatin A increased the euchromatin markers acetylated lysine 9/14 of histone H3 and lysine 8 of histone H4, and HDACi pretreatment increased the phosphorylation of the DNA damage response proteins ataxia telangiectasia mutated and DNA-dependent protein kinase, catalytic subunit, upon irradiation in TICs. HDACi sensitized TICs to cisplatin and to some extent to ionizing irradiation. The protectiveness of a dense chromatin structure was indicated by an enhanced frequency of micronuclei in TICs following irradiation, after knockdown of heterochromatin protein 1γ.

CONCLUSIONS

Although confirmatory studies in additional NSCLC model systems and with respect to analyses of other DNA damage response proteins are needed, our data point toward a heterochromatic structure of NSCLC TICs, such that HDACi can sensitize TICs to DNA damage.

Identification of Novel Bisbenzimidazole Derivatives as Anticancer Vacuolar (H⁺)-ATPase Inhibitors

The vacuolar (H⁺)-ATPases (V-ATPases) are a family of ATP-driven proton pumps and they have been associated with cancer invasion, metastasis, and drug resistance. Despite the clear involvement of V-ATPases in cancer, the therapeutic use of V-ATPase-targeting small molecules has not reached human clinical trials to date. Thus, V-ATPases are emerging as important targets for the identification of potential novel therapeutic agents. We identified a bisbenzimidazole derivative (V) as an initial hit from a similarity search using four known V-ATPase inhibitors (I–IV). Based on the initial hit (V), we designed and synthesized a focused set of novel bisbenzimidazole analogs (2a–e). All newly prepared compounds have been screened for selected human breast cancer (MDA-MB-468, MDA-MB-231, and MCF7) and ovarian cancer (A2780, Cis-A2780, and PA-1) cell lines, along with the normal breast epithelial cell line, MCF10A. The bisbenzimidazole derivative (2e) is active against all cell lines tested. Remarkably, it demonstrated high cytotoxicity against the triple-negative breast cancer (TNBC) cell line, MDA-MB-468 (IC₅₀ = 0.04 ± 0.02 μM). Additionally, it has been shown to inhibit the V-ATPase pump that is mainly responsible for acidification. To the best of our knowledge the bisbenzimidazole pharmacophore has been identified as the first V-ATPase inhibitor in its class. These results strongly suggest that the compound 2e could be further developed as a potential anticancer V-ATPase inhibitor for breast cancer treatment.

Correlation of cancer stem cell markers and immune cell markers in resected non-small cell lung cancer

Background: Recent studies confirmed that immunotherapy showed prominent efficacy in non-small cell lung cancer (NSCLC). Cancer stem cells/cancer initiating cells are resistant to anticancer treatment. The purpose of the study was to analyze the correlation of cancer stem cells/cancer initiating cells and tumor-infiltrating immune cells in NSCLC.

Methods: CD133, octamer 4 (OCT-4), CD8, CD56, human leukocyte antigen (HLA) class I and programmed death ligand-1 (PD-L1) were assessed in 172 resected NSCLC samples. The staining was analyzed and scored by the pathologist who was blinded to the clinical pathological data of the patients.

Results: High CD8+ T cell infiltration was correlated significantly with squamous cell carcinoma histology (p=0.008). High PD-L1 expression (≥10%) was associated with high tumor status (p=0.043). Pearson's correlation test showed that CD56+ cells were negatively correlated with CD133 expression (r=-0.361, p<0.001) and weakly correlated with negative OCT-4 expression (r=-0.180, p=0.018). There was a strong positive correlation between CD8 and HLA class I (r=0.573, p<0.001). In the survival analysis, high CD8+ T cell infiltration is an independent predictor of improved disease-free survival and overall survival. Patients with low CD133 expression and high CD56 expression had a longer overall survival than those with high CD133 expression and/or low CD56 expression (p=0.013).

Conclusion: There is a negative correlation between CD56+ cells and cancer stem cell markers. This correlation may confirm the possibility that natural killer cells can target CD133+ cancer stem cells/cancer initiating cells in non-small cell lung cancer.

Cisplatin resistance in non-small cell lung cancer cells is associated with an abrogation of cisplatin-induced G2/M cell cycle arrest

The efficacy of cisplatin-based chemotherapy in cancer is limited by the occurrence of innate and acquired drug resistance. In order to better understand the mechanisms underlying acquired cisplatin resistance, we have compared the adenocarcinoma-derived non-small cell lung cancer (NSCLC) cell line A549 and its cisplatin-resistant sub-line A549^rCDDP²⁰⁰⁰ with regard to cisplatin resistance mechanisms including cellular platinum accumulation, DNA-adduct formation, cell cycle alterations, apoptosis induction and activation of key players of DNA damage response. In A549^rCDDP²⁰⁰⁰ cells, a cisplatin-induced G₂/M cell cycle arrest was lacking and apoptosis was reduced compared to A549 cells, although equitoxic cisplatin concentrations resulted in comparable platinum-DNA adduct levels. These differences were accompanied by changes in the expression of proteins involved in DNA damage response. In A549 cells, cisplatin exposure led to a significantly higher expression of genes coding for proteins mediating G₂/M arrest and apoptosis (mouse double minute 2 homolog (MDM2), xeroderma pigmentosum complementation group C (XPC), stress inducible protein (SIP) and p21) compared to resistant cells. This was underlined by significantly higher protein levels of phosphorylated Ataxia telangiectasia mutated (pAtm) and p53 in A549 cells compared to their respective untreated control. The results were compiled in a preliminary model of resistance-associated signaling alterations. In conclusion, these findings suggest that acquired resistance of NSCLC cells against cisplatin is the consequence of altered signaling leading to reduced G₂/M cell cycle arrest and apoptosis.