Therapeutic Potential of the miRNA-ATM Axis in the Management of Tumor Radioresistance

Targeting the ATM pathway in cancer: Opportunities, challenges and personalized therapeutic strategies

Ataxia telangiectasia mutated (ATM) kinase plays a pivotal role in orchestrating the DNA damage response, maintaining genomic stability, and regulating various cellular processes. This review provides a comprehensive analysis of ATM's structure, activation mechanisms, and various functions in cancer development, progression, and treatment. I discuss ATM's dual nature as both a tumor suppressor and potential promoter of cancer cell survival in certain contexts. The article explores the complex signaling pathways mediated by ATM, its interactions with other DNA repair mechanisms, and its influence on cell cycle checkpoints, apoptosis, and metabolism. I examine the clinical implications of ATM alterations, including their impact on cancer predisposition, prognosis, and treatment response. The review highlights recent advances in ATM-targeted therapies, discussing ongoing clinical trials of ATM inhibitors and their potential in combination with other treatment modalities. I also address the challenges in developing effective biomarkers for ATM activity and patient selection strategies for personalized cancer therapy. Finally, I outline future research directions, emphasizing the need for refined biomarker development, optimized combination therapies, and strategies to overcome potential resistance mechanisms. This comprehensive overview underscores the critical importance of ATM in cancer biology and its emerging potential as a therapeutic target in precision oncology.

Molecular signaling and clinical implications in the human aging-cancer cycle

It is well documented that aging is associated with cancer, and likewise, cancer survivors display accelerated aging. As the number of aging individuals and cancer survivors continues to grow, it raises additional concerns across society. Therefore, unraveling the molecular mechanisms of aging in tissues is essential to developing effective therapies to fight the aging and cancer diseases in cancer survivors and cancer patients. Indeed, cellular senescence is a critical response, or a natural barrier to suppress the transition of normal cells into cancer cells, however, hypoxia which is physiologically required to maintain the stem cell niche, is increased by aging and inhibits senescence in tissues. Interestingly, oxygen restriction or hypoxia increases longevity and slows the aging process in humans, but hypoxia can also drive angiogenesis to facilitate cancer progression. In addition, cancer treatment is considered as one of the major reasons that drive cellular senescence, subsequently followed by accelerated aging. Several clinical trials have recently evaluated inhibitors to eliminate senescent cells. However, some mechanisms of aging typically can also retard cancer cell growth and progression, which might require careful strategy for better clinical outcomes. Here we describe the molecular regulation of aging and cancer in crosstalk with DNA damage and hypoxia signaling pathways in cancer patients and cancer survivors. We also update several therapeutic strategies that might be critical in reversing the cancer treatment-associated aging process.

Radio-miRs: a comprehensive view of radioresistance-related microRNAs

Radiotherapy is a key treatment option for a wide variety of human tumors, employed either alone or alongside with other therapeutic interventions. Radiotherapy uses high-energy particles to destroy tumor cells, blocking their ability to divide and proliferate. The effectiveness of radiotherapy is due to genetic and epigenetic factors that determine how tumor cells respond to ionizing radiation. These factors contribute to the establishment of resistance to radiotherapy, which increases the risk of poor clinical prognosis of patients. Although the mechanisms by which tumor cells induce radioresistance are unclear, evidence points out several contributing factors including the overexpression of DNA repair systems, increased levels of reactive oxygen species, alterations in the tumor microenvironment, and enrichment of cancer stem cell populations. In this context, dysregulation of microRNAs or miRNAs, critical regulators of gene expression, may influence how tumors respond to radiation. There is increasing evidence that miRNAs may act as sensitizers or enhancers of radioresistance, regulating key processes such as the DNA damage response and the cell death signaling pathway. Furthermore, expression and activity of miRNAs have shown informative value in overcoming radiotherapy and long-term radiotoxicity, revealing their potential as biomarkers. In this review, we will discuss the molecular mechanisms associated with the response to radiotherapy and highlight the central role of miRNAs in regulating the molecular mechanisms responsible for cellular radioresistance. We will also review radio-miRs, radiotherapy-related miRNAs, either as sensitizers or enhancers of radioresistance that hold promise as biomarkers or pharmacological targets to sensitize radioresistant cells.

Advances in molecular targeted therapies to increase efficacy of (chemo)radiation therapy

Recent advances in understanding the tumor's biology in line with a constantly growing number of innovative technologies have prompted characterization of patients' individual malignancies and may display a prerequisite to treat cancer at its patient individual tumor vulnerability. In recent decades, radiation- induced signaling and tumor promoting local events for radiation sensitization were explored in detail, resulting the development of novel molecular targets. A multitude of pharmacological, genetic, and immunological principles, including small molecule- and antibody-based targeted strategies, have been developed that are suitable for combined concepts with radiation (RT) or chemoradiation therapy (CRT). Despite a plethora of promising experimental and preclinical findings, however, so far, only a very limited number of clinical trials have demonstrated a better outcome and/or patient benefit when RT or CRT are combined with targeted agents. The current review aims to summarize recent progress in molecular therapies targeting oncogenic drivers, DNA damage and cell cycle response, apoptosis signaling pathways, cell adhesion molecules, hypoxia, and the tumor microenvironment to impact therapy refractoriness and to boost radiation response. In addition, we will discuss recent advances in nanotechnology, e.g., RNA technologies and protein-degrading proteolysis-targeting chimeras (PROTACs) that may open new and innovative ways to benefit from molecular-targeted therapy approaches with improved efficacy.

Serum miRNA-based signature indicates radiation exposure and dose in humans: A multicenter diagnostic biomarker study

PURPOSE

Mouse and non-human primate models showed that serum miRNAs may be used to predict the biological impact of radiation doses. We hypothesized that these results can be translated to humans treated with total body irradiation (TBI), and that miRNAs may be used as clinically feasible biodosimeters.

METHODS

To test this hypothesis, serial serum samples were obtained from 25 patients (pediatric and adults) who underwent allogeneic stem-cell transplantation and profiled for miRNA expression using next-generation sequencing. miRNAs with diagnostic potential were quantified with qPCR and used to build logistic regression models with lasso penalty to reduce overfitting, identifying samples drawn from patients who underwent total body irradiation to a potentially lethal dose.

RESULTS

Differential expression results were consistent with previous studies in mice and non-human primates. miRNAs with detectable expression in this and two prior animal sets allowed for distinction of the irradiated from non-irradiated samples in mice, macaques and humans, validating the miRNAs as radiation-responsive through evolutionarily conserved transcriptional regulation mechanisms. Finally, we created a model based on the expression of miR-150-5p, miR-30b-5p and miR-320c normalized to two references and adjusted for patient age with an AUC of 0.9 (95%CI:0.83-0.97) for identifying samples drawn after irradiation; a separate model differentiating between high and low radiation dose achieved AUC of 0.85 (95%CI: 0.74-0.96).

CONCLUSIONS

We conclude that serum miRNAs reflect radiation exposure and dose for humans undergoing TBI and may be used as functional biodosimeters for precise identification of people exposed to clinically significant radiation doses.

Profiling ATM regulated genes in Drosophila at physiological condition and after ionizing radiation

Background

ATM (ataxia-telangiectasia mutated) protein kinase is highly conserved in metazoan, and plays a critical role at DNA damage response, oxidative stress, metabolic stress, immunity, RNA biogenesis etc. Systemic profiling of ATM regulated genes, including protein-coding genes, miRNAs, and long non-coding RNAs, will greatly improve our understanding of ATM functions and its regulation. 

Results

1) differentially expressed protein-coding genes, miRNAs, and long non-coding RNAs in atm mutated flies were identified at physiological condition and after X-ray irradiation. 2) functions of differentially expressed genes in atm mutated flies, regardless of protein-coding genes or non-coding RNAs, are closely related with metabolic process, immune response, DNA damage response or oxidative stress. 3) these phenomena are persistent after irradiation. 4) there is a cross-talk regulation towards miRNAs by ATM, E2f1, and p53 during development and after irradiation. 5) knock-out flies or knock-down flies of most irradiation-induced miRNAs were sensitive to ionizing radiation.

Conclusions

We provide a valuable resource of protein-coding genes, miRNAs, and long non-coding RNAs, for understanding ATM functions and regulations. Our work provides the new evidence of inter-dependence among ATM-E2F1-p53 for the regulation of miRNAs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41065-022-00254-9.

Non-coding RNAs and epithelial mesenchymal transition in cancer: molecular mechanisms and clinical implications

Epithelial-mesenchymal transition (EMT) is a fundamental process for embryonic development during which epithelial cells acquire mesenchymal characteristics, and the underlying mechanisms confer malignant features to carcinoma cells such as dissemination throughout the organism and resistance to anticancer treatments. During the past decades, an entire class of molecules, called non-coding RNA (ncRNA), has been characterized as a key regulator of almost every cellular process, including EMT. Like protein-coding genes, ncRNAs can be deregulated in cancer, acting as oncogenes or tumor suppressors. The various forms of ncRNAs, including microRNAs, PIWI-interacting RNAs, small nucleolar RNAs, transfer RNA-derived RNA fragments, long non-coding RNAs, and circular RNAs can orchestrate the complex regulatory networks of EMT at multiple levels. Understanding the molecular mechanism underlying ncRNAs in EMT can provide fundamental insights into cancer metastasis and may lead to novel therapeutic approaches. In this review, we describe recent advances in the understanding of ncRNAs in EMT and provide an overview of recent ncRNA applications in the clinic.

Discrimination between Cancer Cells and DNA-Damaged Cells: Pre-miRNA Region Recognition Based on Hyperbranched Hybrid Chain Reaction Amplification for Simultaneous Sensitive Detection and Imaging of miRNA and Pre-miRNA

Herein, a novel region recognition of precursor microRNA (Pre-miRNA) based on hyperbranched hybrid chain reaction (HB-HCR) amplification was constructed to effectively eliminate the interference of Pre-miRNA to the mature microRNA (miRNA) by establishing the linear mapping relation between the two fluorescence signals produced by the miRNA sequence in the Pre-miRNA and Pre-miRNA residues to first realize simultaneous sensitive detection of Pre-miRNA and miRNA as well as highly sensitive imaging of intracellular Pre-miRNA and miRNA, which solves one main challenge of in vitro tumor disease diagnostics: inaccurate detection of tumor-induced miRNA changes. Impressively, this strategy easily distinguishes cancer cells from normal cells and DNA-damaged cells by the difference in miRNA and Pre-miRNA expression, which provides an innovative approach for accurate clinical diagnosis of cancer and precise treatment of prognosis.

Cell Fate following Irradiation of MDA-MB-231 and MCF-7 Breast Cancer Cells Pre-Exposed to the Tetrahydroisoquinoline Sulfamate Microtubule Disruptor STX3451

A tetrahydroisoquinoline (THIQ) core is able to mimic the A and B rings of 2-methoxyestradiol (2ME2), an endogenous estrogen metabolite that demonstrates promising anticancer properties primarily by disrupting microtubule dynamic instability parameters, but has very poor pharmaceutical properties that can be improved by sulfamoylation. The non-steroidal THIQ-based microtubule disruptor 2-(3-bromo-4,5-dimethoxybenzyl)-7-methoxy-6-sulfamoyloxy-1,2,3,4-tetrahydroisoquinoline (STX3451), with enhanced pharmacokinetic and pharmacodynamic profiles, was explored for the first time in radiation biology. We investigated whether 24 h pre-treatment with STX3451 could pre-sensitize MCF-7 and MDA-MB-231 breast cancer cells to radiation. This regimen showed a clear increase in cytotoxicity compared to the individual modalities, results that were contiguous in spectrophotometric analysis, flow cytometric quantification of apoptosis induction, clonogenic studies and microscopy techniques. Drug pre-treatment increased radiation-induced DNA damage, with statistically more double-strand (ds) DNA breaks demonstrated. The latter could be due to the induction of a radiation-sensitive metaphase block or the increased levels of reactive oxygen species, both evident after compound exposure. STX3451 pre-exposure may also delay DNA repair mechanisms, as the DNA damage response element ataxia telangiectasia mutated (ATM) was depressed. These in vitro findings may translate into in vivo models, with the ultimate aim of reducing both radiation and drug doses for maximal clinical effect with minimal adverse effects.

MicroRNAs in Leukemias: A Clinically Annotated Compendium

Leukemias are a group of malignancies of the blood and bone marrow. Multiple types of leukemia are known, however reliable treatments have not been developed for most leukemia types. Furthermore, even relatively reliable treatments can result in relapses. MicroRNAs (miRNAs) are a class of short, noncoding RNAs responsible for epigenetic regulation of gene expression and have been proposed as a source of potential novel therapeutic targets for leukemias. In order to identify central miRNAs for leukemia, we conducted data synthesis using two databases: miRTarBase and DISNOR. A total of 137 unique miRNAs associated with 16 types of leukemia were retrieved from miRTarBase and 86 protein-coding genes associated with leukemia were retrieved from the DISNOR database. Based on these data, we formed a visual network of 248 miRNA-target interactions (MTI) between leukemia-associated genes and miRNAs associated with ≥4 leukemia types. We then manually reviewed the literature describing these 248 MTIs for interactions identified in leukemia studies. This manually curated data was then used to visualize a network of 64 MTIs identified in leukemia patients, cell lines and animal models. We also formed a visual network of miRNA-leukemia associations. Finally, we compiled leukemia clinical trials from the ClinicalTrials database. miRNAs with the highest number of MTIs were miR-125b-5p, miR-155-5p, miR-181a-5p and miR-19a-3p, while target genes with the highest number of MTIs were TP53, BCL2, KIT, ATM, RUNX1 and ABL1. The analysis of 248 MTIs revealed a large, highly interconnected network. Additionally, a large MTI subnetwork was present in the network visualized from manually reviewed data. The interconnectedness of the MTI subnetwork suggests that certain miRNAs represent central disease molecules for multiple leukemia types. Additional studies on miRNAs, their target genes and associated biological pathways are required to elucidate the therapeutic potential of miRNAs in leukemia.

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

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

ATM: Main Features, Signaling Pathways, and Its Diverse Roles in DNA Damage Response, Tumor Suppression, and Cancer Development

ATM is among of the most critical initiators and coordinators of the DNA-damage response. ATM canonical and non-canonical signaling pathways involve hundreds of downstream targets that control many important cellular processes such as DNA damage repair, apoptosis, cell cycle arrest, metabolism, proliferation, oxidative sensing, among others. Of note, ATM is often considered a major tumor suppressor because of its ability to induce apoptosis and cell cycle arrest. However, in some advanced stage tumor cells, ATM signaling is increased and confers remarkable advantages for cancer cell survival, resistance to radiation and chemotherapy, biosynthesis, proliferation, and metastasis. This review focuses on addressing major characteristics, signaling pathways and especially the diverse roles of ATM in cellular homeostasis and cancer development.

Non-Genomic Actions of Estrogens on the DNA Repair Pathways Are Associated With Chemotherapy Resistance in Breast Cancer

Estrogens have been implicated in the etiology of breast cancer for a long time. It has been stated that long-term exposure to estrogens is associated with a higher incidence of breast cancer, since estradiol (E₂) stimulates breast cell growth; however, its effect on DNA damage/repair is only starting to be investigated. Recent studies have documented that estrogens are able to modify the DNA damage response (DDR) and DNA repair mechanisms. On the other hand, it has been proposed that DDR machinery can be altered by estrogen signaling pathways, that can be related to cancer progression and chemoresistance. We have demonstrated that E₂ promotes c-Src activation and breast cancer cell motility, through a non-genomic pathway. This review discusses scientific evidence supporting this non-genomic mechanism where estrogen modifies the DNA repair pathways, and its relationship to potential causes of chemoresistance.

Hypoxia-Induced Cancer Cell Responses Driving Radioresistance of Hypoxic Tumors: Approaches to Targeting and Radiosensitizing

Simple Summary

Some regions of aggressive malignancies experience hypoxia due to inadequate blood supply. Cancer cells adapting to hypoxic conditions somehow become more resistant to radiation exposure and this decreases the efficacy of radiotherapy toward hypoxic tumors. The present review article helps clarify two intriguing points: why hypoxia-adapted cancer cells turn out radioresistant and how they can be rendered more radiosensitive. The critical molecular targets associated with intratumoral hypoxia and various approaches are here discussed which may be used for sensitizing hypoxic tumors to radiotherapy.

Abstract

Within aggressive malignancies, there usually are the “hypoxic zones”—poorly vascularized regions where tumor cells undergo oxygen deficiency through inadequate blood supply. Besides, hypoxia may arise in tumors as a result of antiangiogenic therapy or transarterial embolization. Adapting to hypoxia, tumor cells acquire a hypoxia-resistant phenotype with the characteristic alterations in signaling, gene expression and metabolism. Both the lack of oxygen by itself and the hypoxia-responsive phenotypic modulations render tumor cells more radioresistant, so that hypoxic tumors are a serious challenge for radiotherapy. An understanding of causes of the radioresistance of hypoxic tumors would help to develop novel ways for overcoming this challenge. Molecular targets for and various approaches to radiosensitizing hypoxic tumors are considered in the present review. It is here analyzed how the hypoxia-induced cellular responses involving hypoxia-inducible factor-1, heat shock transcription factor 1, heat shock proteins, glucose-regulated proteins, epigenetic regulators, autophagy, energy metabolism reprogramming, epithelial–mesenchymal transition and exosome generation contribute to the radioresistance of hypoxic tumors or may be inhibited for attenuating this radioresistance. The pretreatments with a multitarget inhibition of the cancer cell adaptation to hypoxia seem to be a promising approach to sensitizing hypoxic carcinomas, gliomas, lymphomas, sarcomas to radiotherapy and, also, liver tumors to radioembolization.

MicroRNAs in Platelets: Should I Stay or Should I Go?

In this chapter, we discuss different topics always using the microRNA as the guiding thread of the review. MicroRNAs, member of small noncoding RNAs family, are an important element involved in gene expression. We cover different issues such as their importance in the differentiation and maturation of megakaryocytes (megakaryopoiesis), as well as the role in platelets formation (thrombopoiesis) focusing on the described relationship between miRNA and critical myeloid lineage transcription factors such as RUNX1, chemokines receptors as CRCX4, or central hormones in platelet homeostasis like TPO, as well as its receptor (MPL) and the TPO signal transduction pathway, that is JAK/STAT. In addition to platelet biogenesis, we review the microRNA participation in platelets physiology and function. This review also introduces the use of miRNAs as biomarkers of platelet function since the detection of pathogenic situations or response to therapy using these noncoding RNAs is getting increasing interest in disease management. Finally, this chapter describes the participation of platelets in cellular interplay, since extracellular vesicles have been demonstrated to have the ability to deliver microRNAs to others cells, modulating their function through intercellular communication, redefining the extracellular vesicles from the so-called “platelet dust” to become mediators of intercellular communication.

Jack of all trades? The versatility of RNA in DNA double-strand break repair

The mechanisms by which RNA acts in the DNA damage response (DDR), specifically in the repair of DNA double-strand breaks (DSBs), are emerging as multifaceted and complex. Different RNA species, including but not limited to; microRNA (miRNA), long non-coding RNA (lncRNA), RNA:DNA hybrid structures, the recently identified damage-induced lncRNA (dilncRNA), damage-responsive transcripts (DARTs), and DNA damage-dependent small RNAs (DDRNAs), have been shown to play integral roles in the DSB response. The diverse properties of these RNAs, such as sequence, structure, and binding partners, enable them to fulfil a variety of functions in different cellular contexts. Additionally, RNA can be modified post-transcriptionally, a process which is regulated in response to cellular stressors such as DNA damage. Many of these mechanisms are not yet understood and the literature contradictory, reflecting the complexity and expansive nature of the roles of RNA in the DDR. However, it is clear that RNA is pivotal in ensuring the maintenance of genome integrity. In this review, we will discuss and summarise recent evidence which highlights the roles of these various RNAs in preserving genomic integrity, with a particular focus on the emerging role of RNA in the DSB repair response.

Human CtIP: A 'double agent' in DNA repair and tumorigenesis

Human CtIP was originally identified as an interactor of the retinoblastoma protein and BRCA1, two bona fide tumour suppressors frequently mutated in cancer. CtIP is renowned for its role in the resection of DNA double-strand breaks (DSBs) during homologous recombination, a largely error-free DNA repair pathway crucial in maintaining genome integrity. However, CtIP-dependent DNA end resection is equally accountable for alternative end-joining, a mutagenic DSB repair mechanism implicated in oncogenic chromosomal translocations. In addition, CtIP contributes to transcriptional regulation of G1/S transition, DNA damage checkpoint signalling, and replication fork protection pathways. In this review, we present a perspective on the current state of knowledge regarding the tumour-suppressive and oncogenic properties of CtIP and provide an overview of their relevance for cancer development, progression, and therapy.

Fractionated radiation promotes proliferation and radioresistance in bystander A549 cells but not in bystander HT29 cells

AIMS

Recent studies suggest that direct exposure of cells to fractionated radiotherapy might induce radioresistance. However, the effects of fractionated radiotherapy on the non-irradiated bystander cells remain unclear. We hypothesized that fractionated radiotherapy could enhance radioresistance and proliferation of bystander cells.

MAIN METHODS

Human tumor cell lines, including A549 and HT29 were irradiated (2 Gy per day). The irradiated cells (either A549 or HT29) were co-cultured with non-irradiated cells of the same line using transwell co-culture system. Tumor cell proliferation, radioresistance and apoptosis were measured using MTT assay, clonogenic survival assay and Annexin-V in bystander cells, respectively. In addition, activation of Chk1 (Ser 317), Chk2 (Thr 68) and Akt (Ser473) were measured via western blot.

KEY FINDINGS

Irradiated HT29 cells induced conventional bystander effects detected as modulation of clonogenic survival parameters (decreased area under curve, D₁₀ and ED₅₀ and increased α) and proliferation in recipient neighbors. While, irradiated A549 cells significantly enhanced the radioresistance and proliferation of bystander cells. These changes were accompanied with enhanced activation of Chk1, Chk2 and Akt in non-irradiated bystander A549 cells. Moreover, both bystander effects (damaging and protective) were mediated through secreted factors.

SIGNIFICANCE

These findings suggest that fractionated radiotherapy could promote proliferation and radioresistance of bystander cells probably through survival and proliferation pathways.

microRNAs Shape Myeloid Cell-Mediated Resistance to Cancer Immunotherapy

Immunotherapy with immune checkpoint inhibitors can achieve long-term tumor control in subsets of patients. However, its effect can be blunted by myeloid-induced resistance mechanisms. Myeloid cells are highly plastic and physiologically devoted to wound healing and to immune homeostasis maintenance. In cancer, their physiological activities can be modulated, leading to an expansion of pro-inflammatory and immunosuppressive cells, the myeloid-derived suppressor cells (MDSCs), with detrimental consequences. The involvement of MDSCs in tumor development and progression has been widely investigated and MDSC-induced immunosuppression is acknowledged as a mechanism hindering effective immune checkpoint blockade. Small non-coding RNA molecules, the microRNAs (miRs), contribute to myeloid cell regulation at different levels, comprising metabolism and function, as well as their skewing to a MDSC phenotype. miR expression can be indirectly induced by cancer-derived factors or through direct miR import via extracellular vesicles. Due to their structural stability and their presence in body fluids miRs represent promising predictive biomarkers of resistance, as we recently found by investigating plasma samples of melanoma patients undergoing immune checkpoint blockade. Dissection of the miR-driven involved mechanisms would pave the way for the identification of new druggable targets. Here, we discuss the role of these miRs in shaping myeloid resistance to immunotherapy with a special focus on immunosuppression and immune escape.

CSC Radioresistance: A Therapeutic Challenge to Improve Radiotherapy Effectiveness in Cancer

Radiotherapy (RT) is a modality of oncologic treatment that can be used to treat approximately 50% of all cancer patients either alone or in combination with other treatment modalities such as surgery, chemotherapy, immunotherapy, and therapeutic targeting. Despite the technological advances in RT, which allow a more precise delivery of radiation while progressively minimizing the impact on normal tissues, issues like radioresistance and tumor recurrence remain important challenges. Tumor heterogeneity is responsible for the variation in the radiation response of the different tumor subpopulations. A main factor related to radioresistance is the presence of cancer stem cells (CSC) inside tumors, which are responsible for metastases, relapses, RT failure, and a poor prognosis in cancer patients. The plasticity of CSCs, a process highly dependent on the epithelial–mesenchymal transition (EMT) and associated to cell dedifferentiation, complicates the identification and eradication of CSCs and it might be involved in disease relapse and progression after irradiation. The tumor microenvironment and the interactions of CSCs with their niches also play an important role in the response to RT. This review provides a deep insight into the characteristics and radioresistance mechanisms of CSCs and into the role of CSCs and tumor microenvironment in both the primary tumor and metastasis in response to radiation, and the radiobiological principles related to the CSC response to RT. Finally, we summarize the major advances and clinical trials on the development of CSC-based therapies combined with RT to overcome radioresistance. A better understanding of the potential therapeutic targets for CSC radiosensitization will provide safer and more efficient combination strategies, which in turn will improve the live expectancy and curability of cancer patients.

TGF-β and WNT signaling pathways in cardiac fibrosis: non-coding RNAs come into focus

Cardiac fibrosis describes the inappropriate proliferation of cardiac fibroblasts (CFs), leading to accumulation of extracellular matrix (ECM) proteins in the cardiac muscle, which is found in many pathophysiological heart conditions. A range of molecular components and cellular pathways, have been implicated in its pathogenesis. In this review, we focus on the TGF-β and WNT signaling pathways, and their mutual interaction, which have emerged as important factors involved in cardiac pathophysiology. The molecular and cellular processes involved in the initiation and progression of cardiac fibrosis are summarized. We focus on TGF-β and WNT signaling in cardiac fibrosis, ECM production, and myofibroblast transformation. Non-coding RNAs (ncRNAs) are one of the main players in the regulation of multiple pathways and cellular processes. MicroRNAs, long non-coding RNAs, and circular long non-coding RNAs can all interact with the TGF-β/WNT signaling axis to affect cardiac fibrosis. A better understanding of these processes may lead to new approaches for diagnosis and treatment of many cardiac conditions. Video Abstract.

Elevated Levels of circRUNX1 in Colorectal Cancer Promote Cell Growth and Metastasis via miR-145-5p/IGF1 Signalling

Background

Emerging evidence suggests that circular RNAs (circRNAs) are vital regulators in a range of cancers. “miRNA sponge” is the most reported role played by circRNAs in many tumors. The insulin-like growth factor (IGF) 1 pathway plays a key role in the development and progression of many cancers, including colorectal cancer (CRC). The aim of the study is to establish the potential clinical value and driving molecular mechanisms of circRNAs in CRC.

Materials and Methods

Real-time quantitative RT-PCR (qRT-PCR) was performed to measure the circRUNX1 expression in 52 tissue samples from CRC patients. We verified the tumor promotor role of circRUNX1 in cell-based in vitro and in vivo assays. Human growth factor array was used to identify circRUNX1-regulated signaling pathways. We then used a double luciferase reporter assay and RNA fluorescence in situ hybridization to identify the downstream miR-145-5p of circRUNX1. Furthermore, we performed Western blotting and biological function assays to demonstrate if the circRUNX1/miR-145-5p/IGF1 axis is responsible for the proliferation of CRC cells and promotes CRC development.

Results

By performing qRT-PCR from CRC tissues and paired adjacent normal mucosa tissues, we identified that circRUNX1 expression was significantly upregulated in CRC tissues and positively related with lymph node metastasis, distant metastasis and advanced tumor-node-metastasis tumor stage in patients. Functionally, circRUNX1 knockdown inhibited cell proliferation and migration and promoted apoptosis, whereas its overexpression exerted opposite effects. In vivo, circRUNX1 promoted tumor growth and metastasis. Mechanically, circRUNX1 shared miRNA response elements with IGF1. circRUNX1 competitively bound to miR-145-5p and prevented miR-145-5p from decreasing the expression of IGF1, which facilitated tumor growth.

Conclusion

Our studies verified that circRUNX1 functions as a tumor promotor in CRC cells by targeting the miR-145-5p/IGF1 signaling pathway and may have potential use as a prognostic indicator and therapeutic target in CRC patients.

Integrative data modeling from lung and lymphatic cancer predicts functional roles for miR-34a and miR-16 in cell fate regulation

MiR-34a and miR-16 coordinately control cell cycle checkpoint in non-small cell lung cancer (NSCLC) cells. In cutaneous T-cell lymphoma (CTCL) cells miR-16 regulates a switch between apoptosis and senescence, however the role of miR-34a in this process is unclear. Both miRNAs share many common targets and experimental evidences suggest that they synergistically control the cell-fate regulation of NSCLC. In this work we investigate whether the coordinate action between miR-34a and miR-16 can explain experimental results in multiple cell lines of NSCLC and CTCL. For that we propose a Boolean model of the G1/S checkpoint regulation contemplating the regulatory influences of both miRNAs. Model validation was performed by comparisons with experimental information from the following cell lines: A549, H460, H1299, MyLa and MJ presenting excellent agreement. The model integrates in a single logical framework the mechanisms responsible for cell fate decision in NSCLC and CTCL cells. From the model analysis we suggest that miR-34a is the main controller of miR-16 activity in these cells. The model also allows to investigate perturbations of single or more molecules with the purpose to intervene in cell fate mechanisms of NSCLC and CTCL cells.