The role of epithelial-mesenchymal transition in regulating radioresistance

Advances in Therapy for Urothelial and Non-Urothelial Subtype Histologies of Advanced Bladder Cancer: From Etiology to Current Development

Urothelial carcinoma (UC) is the most common histological subtype of bladder tumors; however, bladder cancer represents a heterogeneous group of diseases with at least 40 distinct histological subtypes. Among these, the 2022 World Health Organization classification of urinary tract tumors identifies a range of less common subtypes of invasive UC, formerly known as variants, which are considered high-grade tumors, including squamous cell, small-cell, sarcomatoid urothelial, micropapillary, plasmacytoid, and urachal carcinomas, and adenocarcinoma. Their accurate histological diagnosis is critical for risk stratification and therapeutic decision-making, as most subtype histologies are associated with poorer outcomes than conventional UC. Despite the importance of a precise diagnosis, high-quality evidence on optimal treatments for subtype histologies remains limited owing to their rarity. In particular, neoadjuvant and adjuvant chemotherapy have not been well characterized, and prospective data are scarce. For advanced-stage diseases, clinical trial participation is strongly recommended to address the lack of robust evidence. Advances in molecular pathology and the development of targeted therapies and immunotherapies have reshaped our understanding and classification of bladder cancer subtypes, spurring efforts to identify predictive biomarkers to guide personalized treatment strategies. Nevertheless, the management of rare bladder cancer subgroups remains challenging because they are frequently excluded from clinical trials. For localized disease, curative options such as surgical resection or radiotherapy are available; however, treatment options become more limited in recurrence or metastasis, where systemic therapy is primarily used to control disease progression and palliate symptoms. Herein, we present recent advances in the management of urothelial and non-urothelial bladder cancer subtypes and also explore the current evidence guiding their treatment and emphasize the challenges and perspectives of future therapeutic strategies.

Role of Non-coding RNAs on the Radiotherapy Sensitivity and Resistance in Cancer Cells

Radiotherapy (RT) is an integral part of treatment management in cancer patients. However, one of the limitations of this treatment method is the resistance of cancer cells to radiotherapy. These restrictions necessitate the introduction of modalities for the radiosensitization of cancer cells. It has been shown that Noncoding RNAs (ncRNAs), along with modifiers, can act as radiosensitivity and radioresistant regulators in a variety of cancers by affecting double strand break (DSB), wnt signaling, glycolysis, irradiation induced apoptosis, ferroptosis and cell autophagy. This review will provide an overview of the latest research on the roles and regulatory mechanisms of ncRNA after RT in in vitro and preclinical researches.

Anti-Inflammatory and Anticancer Effects of Kaurenoic Acid in Overcoming Radioresistance in Breast Cancer Radiotherapy

Background/Objectives: Peroxisome proliferator-activated receptor γ (PPARγ) plays a key role in mediating anti-inflammatory and anticancer effects in the tumor microenvironment. Kaurenoic acid (KA), a diterpene compound isolated from Sphagneticola trilobata (L.) Pruski, has been demonstrated to exert anti-inflammatory, anticancer, and antihuman immunodeficiency virus effects. Methods: In this study, we identified KA as a novel activator of PPARγ with potent anti-inflammatory and antitumor effects both in vitro and in vivo. Given the potential of PPARγ regulators in overcoming radioresistance and chemoresistance in cancer therapies, we hypothesized that KA may enhance the efficacy of breast cancer radiotherapy. Results: In a lipopolysaccharide (LPS)-induced mouse inflammation model, KA treatment reduced the levels of pro-inflammatory cytokines, including COX-2, IL-6, IL-1β, and TNFα. In a xenograft mouse mode of breast cancer, KA treatment inhibited tumor growth. Specifically, KA treatment enhanced caspase-3 activity and cytotoxicity against MDA-MB-231 and MCF-7 breast cancer cells. When KA was co-treated with a caspase inhibitor, Z-VAD-FMK, caspase-dependent apoptosis was suppressed in these cells. KA was found to induce the generation of cytosolic calcium ions (Ca2+) and reactive oxygen species (ROS), triggering endoplasmic reticulum (ER) stress via the PERK-ATF4-CHOP axis. Hence, the ER stressor thapsigargin (TG) synergized with KA treatment to enhance apoptosis in these cells, while the loss of the PERK or CHOP function inhibited this phenomenon. KA treatment was shown to induce oxidative stress via the NADPH oxidase 4 (NOX4) and stimulate ROS production. Specifically, NOX4 knockdown (KD) and antioxidant treatment (N-acetyl cysteine or diphenyleneiodonium) suppressed such ER stress-mediated apoptosis by inhibiting KA-enhanced caspase-3 activity, cytotoxicity, and intracellular ROS production in the treated cells. In radioresistant MDA-MB-231R and MCF-7R cells, KA combined with 2 Gy radiation overcame radioresistance by upregulating PPARγ and modulating epithelial-mesenchymal transition (EMT) markers, such as E-cadherin, N-cadherin, and vimentin. In PPARγ KD MDA-MB-231R and MCF-7R cells, this phenomenon was inhibited due to reduced PPARγ and NOX4 expression. Conclusions: In conclusion, these findings demonstrated KA as a novel PPARγ regulator with promising potential to enhance the efficacy of breast cancer radiotherapy.

A novel high-risk model identified by epithelial-mesenchymal transition predicts prognosis and radioresistance in rectal cancer

Many studies have shown that tumor cells that survive radiotherapy are more likely to metastasize, but the underlying mechanism remains unclear. Here we aimed to identify epithelial-mesenchymal transition (EMT)-related key genes, which associated with prognosis and radiosensitivity in rectal cancer. First, we obtained differentially expressed genes by analyzing the RNA expression profiles of rectal cancer retrieved from The Cancer Genome Atlas database, EMT-related genes, and radiotherapy-related databases, respectively. Then, Lasso and Cox regression analyses were used to establish an EMT-related prognosis model (EMTPM) based on the identified independent protective factor Fibulin5 (FBLN5) and independent risk gene EHMT2. The high-EMTPM group exhibited significantly poorer prognosis. Then, we evaluated the signature in an external clinical validation cohort. Through in vivo experiments, we further demonstrated that EMTPM effectively distinguishes radioresistant from radiosensitive patients with rectal cancer. Moreover, individuals in the high-EMTPM group showed increased expression of immune checkpoints compared to their counterparts. Finally, pan-cancer analysis of the EMTPM model also indicated its potential for predicting the prognosis of lung squamous cell carcinoma and breast cancer patients undergoing radiotherapy. In summary, we established a novel predictive model for rectal cancer prognosis and radioresistance based on FBLN5 and EHMT2 expressions, and suggested that immune microenvironment may be involved in the process of radioresistance. This predictive model could be used to select management strategies for rectal cancer.

PP2A B55α inhibits epithelial-mesenchymal transition via regulation of Slug expression in non-small cell lung cancer

PP2A B55α, encoded by PPP2R2A, acts as a regulatory subunit of the serine/threonine phosphatase PP2A. Despite a frequent loss of heterozygosity of PPP2R2A in cases of non-small cell lung cancer (NSCLC), research on PP2A B55α's functions remains limited and controversial. To investigate the biological roles of PP2A B55α, we conducted bulk RNA-sequencing to assess the impact of PPP2R2A knockdown using two shRNAs in a NSCLC cell line. Gene set enrichment analysis (GSEA) of the RNA-sequencing data revealed significant enrichment of the epithelial-mesenchymal transition (EMT) pathway, with SNAI2 (the gene encoding Slug) emerging as one of the top candidates. Our findings demonstrate that PP2A B55α suppresses EMT, as PPP2R2A deficiency through knockdown or homozygous or hemizygous depletion promotes EMT and metastatic behavior in NSCLC cells, as evidenced by changes in EMT biomarkers, invasion and migration abilities, as well as metastasis in a tail vein assay. Mechanistically, PP2A B55α inhibits EMT by downregulating SNAI2 expression via the GSK3β-β-catenin pathway. Importantly, PPP2R2A deficiency also slows cell proliferation by disrupting DNA replication, particularly in PPP2R2A-/- cells. Furthermore, PPP2R2A deficiency, especially PPP2R2A-/- cells, leads to an increase in the cancer stem cell population, which correlates with enhanced resistance to chemotherapy. Overall, the decrease in PP2A B55α levels due to hemizygous/homozygous depletion heightens EMT and the metastatic or stemness/drug resistance potential of NSCLC cells despite their proliferation disadvantage. Our study highlights the significance of PP2A B55α in EMT and metastasis and suggests that targeting EMT/stemness could be a potential therapeutic strategy for treating PPP2R2A-deficient NSCLC.

MicroRNAs targeted mTOR as therapeutic agents to improve radiotherapy outcome

MicroRNAs (miRNAs) are small RNA molecules that regulate genes and are involved in various biological processes, including cancer development. Researchers have been exploring the potential of miRNAs as therapeutic agents in cancer treatment. Specifically, targeting the mammalian target of the rapamycin (mTOR) pathway with miRNAs has shown promise in improving the effectiveness of radiotherapy (RT), a common cancer treatment. This review provides an overview of the current understanding of miRNAs targeting mTOR as therapeutic agents to enhance RT outcomes in cancer patients. It emphasizes the importance of understanding the specific miRNAs that target mTOR and their impact on radiosensitivity for personalized cancer treatment approaches. The review also discusses the role of mTOR in cell homeostasis, cell proliferation, and immune response, as well as its association with oncogenesis. It highlights the different ways in which miRNAs can potentially affect the mTOR pathway and their implications in immune-related diseases. Preclinical findings suggest that combining mTOR modulators with RT can inhibit tumor growth through anti-angiogenic and anti-vascular effects, but further research and clinical trials are needed to validate the efficacy and safety of using miRNAs targeting mTOR as therapeutic agents in combination with RT. Overall, this review provides a comprehensive understanding of the potential of miRNAs targeting mTOR to enhance RT efficacy in cancer treatment and emphasizes the need for further research to translate these findings into improved clinical outcomes.

Mechanisms of traditional Chinese medicine overcoming of radiotherapy resistance in breast cancer

Breast cancer stands as the most prevalent malignancy among women, with radiotherapy serving as a primary treatment modality. Despite radiotherapy, a subset of breast cancer patients experiences local recurrence, attributed to the intrinsic resistance of tumors to radiation. Therefore, there is a compelling need to explore novel approaches that can enhance cytotoxic effects through alternative mechanisms. Traditional Chinese Medicine (TCM) and its active constituents exhibit diverse pharmacological actions, including anti-tumor effects, offering extensive possibilities to identify effective components capable of overcoming radiotherapy resistance. This review delineates the mechanisms underlying radiotherapy resistance in breast cancer, along with potential candidate Chinese herbal medicines that may sensitize breast cancer cells to radiotherapy. The exploration of such herbal interventions holds promise for improving therapeutic outcomes in the context of breast cancer radiotherapy resistance.

The importance of integrated therapies on cancer: Silibinin, an old and new molecule

In the landscape of cancer treatments, the efficacy of coadjuvant molecules remains a focus of attention for clinical research with the aim of reducing toxicity and achieving better outcomes. Most of the pathogenetic processes causing tumour development, neoplastic progression, ageing, and increased toxicity involve inflammation. Inflammatory mechanisms can progress through a variety of molecular patterns. As is well known, the ageing process is determined by pathological pathways very similar and often parallel to those that cause cancer development. Among these complex mechanisms, inflammation is currently much studied and is often referred to in the geriatric field as 'inflammaging'. In this context, treatments active in the management of inflammatory mechanisms could play a role as adjuvants to standard therapies. Among these emerging molecules, Silibinin has demonstrated its anti-inflammatory properties in different neoplastic types, also in combination with chemotherapeutic agents. Moreover, this molecule could represent a breakthrough in the management of age-related processes. Thus, Silibinin could be a valuable adjuvant to reduce drug-related toxicity and increase therapeutic potential. For this reason, the main aim of this review is to collect and analyse data presented in the literature on the use of Silibinin, to better understand the mechanisms of the functioning of this molecule and its possible therapeutic role.

High core 1β1,3-galactosyltransferase 1 expression is associated with poor prognosis and promotes cellular radioresistance in lung adenocarcinoma

PURPOSE

Core 1β1,3-galactosyltransferase 1 (C1GALT1) exhibits elevated expression in multiple cancers. The present study aimed to elucidate the clinical significance of C1GALT1 aberrant expression and its impact on radiosensitivity in lung adenocarcinoma (LUAD).

METHODS

The C1GALT1 expression and its clinical relevance were investigated through public databases and LUAD tissue microarray analyses. A549 and H1299 cells with either C1GALT1 knockdown or overexpression were further assessed through colony formation, gamma-H2A histone family member X immunofluorescence, 5-ethynyl-2'-deoxyuridine incorporation, and flow cytometry assays. Bioinformatics analysis was used to explore single cell sequencing data, revealing the influence of C1GALT1 on cancer-associated cellular states. Vimentin, N-cadherin, and E-cadherin protein levels were measured through western blotting.

RESULTS

The expression of C1GALT1 was significantly higher in LUAD tissues than in adjacent non-tumor tissues both at mRNA and protein level. High expression of C1GALT1 was correlated with lymph node metastasis, advanced T stage, and poor survival, and was an independent risk factor for overall survival. Radiation notably upregulated C1GALT1 expression in A549 and H1299 cells, while radiosensitivity was increased following C1GALT1 knockdown and decreased following overexpression. Experiment results showed that overexpression of C1GALT1 conferred radioresistance, promoting DNA repair, cell proliferation, and G2/M phase arrest, while inhibiting apoptosis and decreasing E-cadherin expression, alongside upregulating vimentin and N-cadherin in A549 and H1299 cells. Conversely, C1GALT1 knockdown had opposing effects.

CONCLUSION

Elevated C1GALT1 expression in LUAD is associated with an unfavorable prognosis and contributes to increased radioresistance potentially by affecting DNA repair, cell proliferation, cell cycle regulation, and epithelial-mesenchymal transition (EMT).

Revolutionizing pediatric neuroblastoma treatment: unraveling new molecular targets for precision interventions

Neuroblastoma (NB) is the most frequent solid tumor in pediatric cases, contributing to around 15% of childhood cancer-related deaths. The wide-ranging genetic, morphological, and clinical diversity within NB complicates the success of current treatment methods. Acquiring an in-depth understanding of genetic alterations implicated in the development of NB is essential for creating safer and more efficient therapies for this severe condition. Several molecular signatures are being studied as potential targets for developing new treatments for NB patients. In this article, we have examined the molecular factors and genetic irregularities, including those within insulin gene enhancer binding protein 1 (ISL1), dihydropyrimidinase-like 3 (DPYSL3), receptor tyrosine kinase-like orphan receptor 1 (ROR1) and murine double minute 2-tumor protein 53 (MDM2-P53) that play an essential role in the development of NB. A thorough summary of the molecular targeted treatments currently being studied in pre-clinical and clinical trials has been described. Recent studies of immunotherapeutic agents used in NB are also studied in this article. Moreover, we explore potential future directions to discover new targets and treatments to enhance existing therapies and ultimately improve treatment outcomes and survival rates for NB patients.

RGMb impacts partial epithelial-mesenchymal transition and BMP2-Induced ID mRNA expression independent of PD-L2 in nonsmall cell lung cancer cells

PD-1/PD-ligand-axis immunotherapy-mediated activation of T-cells for cancer cell elimination is a promising treatment of nonsmall cell lung cancer (NSCLC). However, the effect of immunotherapy on intracellular signaling pathways in cancer cells still needs further delineation. Repulsive Guidance Molecule b (RGMb), a regulator of Bone Morphogenetic Proteins (BMPs) signaling, interacts with the PD-ligand, PD-L2, at cancer cell membranes. Accordingly, a clarification of the functions of RGMb and its relation to PD-L2 might provide insight into NSCLC cell signaling responses to PD-1/PD-ligand-axis immunotherapy. In this study, the functions of RGMb and PD-L2 were examined using the two NSCLC cell lines HCC827 and A549. CRISPR/Cas9 was used to decrease the expression of RGMb and PD-L2, while lentiviral vectors were used to increase their expression. Downstream effects were examined by RT-qPCR and immunoassays. Ectopic expression of RGMb impacted BMP2-induced expression of ID1 and ID2 messenger RNA (mRNA) independently of PD-L2, while RGMb depletion by CRISPR/Cas9 did not affect the BMP2-mediated induction of ID1, ID2, and ID3 mRNA. However, depletion of RGMb resulted in a partial epithelial-mesenchymal transition (EMT) gene expression profile in HCC827 cells, which was not mimicked by PD-L2 depletion. The results show that RGMb is a coregulator of BMP signaling and hence, ID mRNA expression and that RGMb can control the EMT balance in NSCLC cells. However, RGMb appears to exert these functions independently of PD-L2, and accordingly, the PD-1/PD-ligand axis for immune surveillance in NSCLC cells.

Mitochondrial metabolism: a predictive biomarker of radiotherapy efficacy and toxicity

INTRODUCTION

Radiotherapy is a mainstay of cancer treatment. Clinical studies revealed a heterogenous response to radiotherapy, from a complete response to even disease progression. To that end, finding the relative prognostic factors of disease outcomes and predictive factors of treatment efficacy and toxicity is essential. It has been demonstrated that radiation response depends on DNA damage response, cell cycle phase, oxygen concentration, and growth rate. Emerging evidence suggests that altered mitochondrial metabolism is associated with radioresistance.

METHODS

This article provides a comprehensive evaluation of the role of mitochondria in radiotherapy efficacy and toxicity. In addition, it demonstrates how mitochondria might be involved in the famous 6Rs of radiobiology.

RESULTS

In terms of this idea, decreasing the mitochondrial metabolism of cancer cells may increase radiation response, and enhancing the mitochondrial metabolism of normal cells may reduce radiation toxicity. Enhancing the normal cells (including immune cells) mitochondrial metabolism can potentially improve the tumor response by enhancing immune reactivation. Future studies are invited to examine the impacts of mitochondrial metabolism on radiation efficacy and toxicity. Improving radiotherapy response with diminishing cancer cells' mitochondrial metabolism, and reducing radiotherapy toxicity with enhancing normal cells' mitochondrial metabolism.

MAPK11 (p38β) is a major determinant of cellular radiosensitivity by controlling ionizing radiation-associated senescence: An in vitro study

Background and purpose

MAPKs are among the most relevant signalling pathways involved in coordinating cell responses to different stimuli. This group includes p38MAPKs, constituted by 4 different proteins with a high sequence homology: MAPK14 (p38α), MAPK11 (p38β), MAPK12 (p38γ) and MAPK13 (p38δ). Despite their high similarity, each member shows unique expression patterns and even exclusive functions. Thus, analysing protein-specific functions of MAPK members is necessary to unequivocally uncover the roles of this signalling pathway. Here, we investigate the possible role of MAPK11 in the cell response to ionizing radiation (IR).

Materials and methods

We developed MAPK11/14 knockdown through shRNA and CRISPR interference gene perturbation approaches and analysed the downstream effects on cell responses to ionizing radiation in A549, HCT-116 and MCF-7 cancer cell lines. Specifically, we assessed IR toxicity by clonogenic assays; DNA damage response activity by immunocytochemistry; apoptosis and cell cycle by flow cytometry (Annexin V and propidium iodide, respectively); DNA repair by comet assay; and senescence induction by both X-Gal staining and gene expression of senescence-associated genes by RT-qPCR.

Results

Our findings demonstrate a critical role of MAPK11 in the cellular response to IR by controlling the associated senescent phenotype, and without observable effects on DNA damage response, apoptosis, cell cycle or DNA damage repair.

Conclusion

Our results highlight MAPK11 as a novel mediator of the cellular response to ionizing radiation through the control exerted onto IR-associated senescence.

Ribosome biosynthesis and Hedgehog activity are cooperative actionable signaling mechanisms in breast cancer following radiotherapy

Hyperactivated ribosome biosynthesis is attributed to a need for elevated protein synthesis that accommodates cell growth and division, and is characterized by nucleomorphometric alterations and increased nucleolar counts. Ribosome biogenesis is challenged when DNA-damaging treatments such as radiotherapy are utilized. Tumor cells that survive radiotherapy form the basis of recurrence, tumor progression, and metastasis. In order to survive and become metabolically revitalized, tumor cells need to reactivate RNA Polymerase I (RNA Pol I) to synthesize ribosomal RNA, an integral component of ribosomes. In this study, we showed that following radiation therapy, tumor cells from breast cancer patients demonstrate activation of a ribosome biosynthesis signature concurrent with enrichment of a signature of Hedgehog (Hh) activity. We hypothesized that GLI1 activates RNA Pol I in response to irradiation and licenses the emergence of a radioresistant tumor population. Our work establishes a novel role for GLI1 in orchestrating RNA Pol I activity in irradiated breast cancer cells. Furthermore, we present evidence that in these irradiated tumor cells, Treacle ribosome biogenesis factor 1 (TCOF1), a nucleolar protein that is important in ribosome biogenesis, facilitates nucleolar translocation of GLI1. Inhibiting Hh activity and RNA Pol I activity disabled the outgrowth of breast cancer cells in the lungs. As such, ribosome biosynthesis and Hh activity present as actionable signaling mechanisms to enhance the effectiveness of radiotherapy.

Harnessing function of EMT in hepatocellular carcinoma: From biological view to nanotechnological standpoint

Management of cancer metastasis has been associated with remarkable reduction in progression of cancer cells and improving survival rate of patients. Since 90% of mortality are due to cancer metastasis, its suppression can improve ability in cancer fighting. The EMT has been an underlying cause in increasing cancer migration and it is followed by mesenchymal transformation of epithelial cells. HCC is the predominant kind of liver tumor threatening life of many people around the world with poor prognosis. Increasing patient prognosis can be obtained via inhibiting tumor metastasis. HCC metastasis modulation by EMT and HCC therapy by nanoparticles are discussed here. First of all, EMT happens during progression and advanced stages of HCC and therefore, its inhibition can reduce tumor malignancy. Moreover, anti-cancer compounds including all-trans retinoic acid and plumbaging, among others, have been considered as inhibitors of EMT. The EMT association with chemoresistance has been evaluated. Moreover, ZEB1/2, TGF-β, Snail and Twist are EMT modulators in HCC and enhancing cancer invasion. Therefore, EMT mechanism and related molecular mechanisms in HCC are evaluated. The treatment of HCC has not been only emphasized on targeting molecular pathways with pharmacological compounds and since drugs have low bioavailability, their targeted delivery by nanoparticles promotes HCC elimination. Moreover, nanoparticle-mediated phototherapy impairs tumorigenesis in HCC by triggering cell death. Metastasis of HCC and even EMT mechanism can be suppressed by cargo-loaded nanoparticles.

Molecular mechanisms of tumor resistance to radiotherapy

BACKGROUND

Cancer is the most prevalent cause of death globally, and radiotherapy is considered the standard of care for most solid tumors, including lung, breast, esophageal, and colorectal cancers and glioblastoma. Resistance to radiation can lead to local treatment failure and even cancer recurrence.

MAIN BODY

In this review, we have extensively discussed several crucial aspects that cause resistance of cancer to radiation therapy, including radiation-induced DNA damage repair, cell cycle arrest, apoptosis escape, abundance of cancer stem cells, modification of cancer cells and their microenvironment, presence of exosomal and non-coding RNA, metabolic reprogramming, and ferroptosis. We aim to focus on the molecular mechanisms of cancer radiotherapy resistance in relation to these aspects and to discuss possible targets to improve treatment outcomes.

CONCLUSIONS

Studying the molecular mechanisms responsible for radiotherapy resistance and its interactions with the tumor environment will help improve cancer responses to radiotherapy. Our review provides a foundation to identify and overcome the obstacles to effective radiotherapy.

Adaptive c-Met-PLXDC2 Signaling Axis Mediates Cancer Stem Cell Plasticity to Confer Radioresistance-associated Aggressiveness in Head and Neck Cancer

Radiotherapy plays an essential role in the treatment of head and neck squamous cell carcinoma (HNSCC), yet radioresistance remains a major barrier to therapeutic efficacy. A better understanding of the predominant pathways determining radiotherapy response could help develop mechanism-informed therapies to improve cancer management. Here we report that radioresistant HNSCC cells exhibit increased tumor aggressiveness. Using unbiased proteome profiler antibody arrays, we identify that upregulation of c-Met phosphorylation is one of the critical mechanisms for radioresistance in HNSCC cells. We further uncover that radioresistance-associated HNSCC aggressiveness is effectively exacerbated by c-Met but is suppressed by its genetic knockdown and pharmacologic inactivation. Mechanistically, the resulting upregulation of c-Met promotes elevated expression of plexin domain containing 2 (PLXDC2) through activating ERK1/2-ELK1 signaling, which in turn modulates cancer cell plasticity by epithelial-mesenchymal transition (EMT) induction and enrichment of the cancer stem cell (CSC) subpopulation, leading to resistance of HNSCC cells to radiotherapy. Depletion of PLXDC2 overcomes c-Met-mediated radioresistance through reversing the EMT progress and blunting the self-renewal capacity of CSCs. Therapeutically, the addition of SU11274, a selective and potent c-Met inhibitor, to radiation induces tumor shrinkage and limits tumor metastasis to lymph nodes in an orthotopic mouse model. Collectively, these significant findings not only demonstrate a novel mechanism underpinning radioresistance-associated aggressiveness but also provide a possible therapeutic strategy to target radioresistance in patients with HNSCC.

Significance

This work provides novel insights into c-Met-PLXDC2 signaling in radioresistance-associated aggressiveness and suggests a new mechanism-informed therapeutic strategy to overcome failure of radiotherapy in patients with HNSCC.

The role of EphA2 in ADAM17- and ionizing radiation-enhanced lung cancer cell migration

Purpose

Ionizing radiation (IR) enhances the migratory capacity of cancer cells. Here we investigate in non-small-cell-lung-cancer (NSCLC) cells a novel link between IR-enhanced ADAM17 activity and the non-canonical pathway of EphA2 in the cellular stress response to irradiation.

Methods

Cancer cell migration in dependence of IR, EphA2, and paracrine signaling mediated by ADAM17 was determined using transwell migration assays. Changes of EphA2 pS897 and mRNA expression levels upon different ADAM17-directed treatment strategies, including the small molecular inhibitor TMI-005, the monoclonal antibody MEDI3622, and shRNAs, were mechanistically investigated. ADAM17-mediated release and cleavage of the EphA2 ligand ephrin-A1 was measured using ELISA and an acellular cleavage assay.

Results

Irradiation with 5 Gy enhanced tumor cell migration of NSCLC NCI-H358 cells in dependence of EphA2. At the same time, IR increased growth factor-induced EphA2 S897 phosphorylation via auto- and paracrine signaling. Genetic and pharmaceutical downregulation of ADAM17 activity abrogated growth factor (e.g. amphiregulin) release, which reduced MAPK pathway-mediated EphA2 S897 phosphorylation in an auto- and paracrine way (non-canonical EphA2-pathway) in NCI-H358 and A549 cells. These signaling processes were associated with reduced cell migration towards conditioned media derived from ADAM17-deficient cells. Interestingly, ADAM17 inhibition with the small molecular inhibitor TMI-005 led to the internalization and proteasomal degradation of EphA2, which was rescued by amphiregulin or MG-132 treatment. In addition, ADAM17 inhibition also abrogated ephrin-A1 cleavage and thereby interfered with the canonical EphA2-pathway.

Conclusion

We identified ADAM17 and the receptor tyrosine kinase EphA2 as two important drivers for (IR-) induced NSCLC cell migration and described a unique interrelation between ADAM17 and EphA2. We demonstrated that ADAM17 influences both, EphA2 (pS897) and its GPI-anchored ligand ephrin-A1. Using different cellular and molecular readouts, we generated a comprehensive picture of how ADAM17 and IR influence the EphA2 canonical and non-canonical pathway in NSCLC cells.

Lenvatinib Synergistically Promotes Radiation Therapy in Hepatocellular Carcinoma by Inhibiting Src/STAT3/NF-κB-Mediated Epithelial-Mesenchymal Transition and Metastasis

PURPOSE

This study suggested that lenvatinib may incapacitate hepatocellular carcinoma (HCC) to radiation treatment by abrogating radiation-induced Src/signal transducer and the activator of transcription 3 signaling (STAT3)/nuclear factor-κB (NF-κB) to escalate radiation-induced extrinsic and intrinsic apoptosis. These findings uncover the role of targeting Src and its arbitrating epithelial-mesenchymal transition (EMT), which could increase the anti-HCC efficacy of radiation therapy (RT). Lenvatinib and sorafenib are multikinase inhibitors used to treat HCC. Lenvatinib is noninferior to sorafenib in the therapeutic response in HCC. However, whether lenvatinib intensifies the anti-HCC efficacy of RT is ambiguous. Several oncogenic kinases and transcription factors, such as Src, STAT3, and NF-κB, enhance the radiosensitivity of cancers. Therefore, we aimed to investigate the roles of the Src/STAT3/NF-κB axis in HCC after RT treatment and assessed whether targeting Src by lenvatinib may enhance the effectiveness of RT.

METHODS AND MATERIALS

Hep3B, Huh7, HepG2, and SK-Hep1 HCC cells and 2 types of animal models were used to identify the efficacy of RT combined with lenvatinib. Cellular toxicity, apoptosis, DNA damage, EMT/metastasis regulation, and treatment efficacy were validated by colony formation, flow cytometry, Western blotting, and in vivo experiments, respectively. Knockdown of Src by siRNA was also used to validate the role of Src in RT treatment.

RESULTS

Silencing Src reduced STAT3/NF-κB signaling and sensitized HCC to radiation. Lenvatinib reversed radiation-elicited Src/STAT3/NF-κB signaling while enhancing the anti-HCC efficacy of radiation. Both lenvatinib and siSrc promoted the radiation effect of cell proliferation on suppression, inhibition of the invasion ability, and induction of apoptosis in HCC. Lenvatinib also alleviated radiation-triggered oncogenic and EMT-related protein expression.

CONCLUSIONS

Our findings uncovered the role of the Src/STAT3/NF-κB regulatory axis in response to radiation-induced toxicity and confirmed Src as the key regulatory molecule for radiosensitization of HCC evoked by lenvatinib.

Acquired radioresistance in EMT6 mouse mammary carcinoma cell line is mediated by CTLA-4 and PD-1 through JAK/STAT/PI3K pathway

Cancer recurrence is often associated with the acquisition of radioresistance by cancer tissues due to failure in radiotherapy. The underlying mechanism leading to the development of acquired radioresistance in the EMT6 mouse mammary carcinoma cell line and the potential pathway involved was investigated by comparing differential gene expressions between parental and acquired radioresistance cells. EMT6 cell line was exposed to 2 Gy/per cycle of gamma-ray and the survival fraction between EMT6-treated and parental cells was compared. EMT6RR_MJI (acquired radioresistance) cells was developed after 8 cycles of fractionated irradiation. The development of EMT6RR_MJI cells was confirmed with further irradiation at different doses of gamma-ray, and both the survival fraction and migration rates were measured. Higher survival fraction and migration rates were obtained in EMT6RR_MJI cells after exposure to 4 Gy and 8 Gy gamma-ray irradiations compared to their parental cells. Gene expression between EMT6RR_MJI and parental cells was compared, and 16 genes identified to possess more than tenfold changes were selected and validated using RT-PCR. Out of these genes, 5 were significantly up-regulated i.e., IL-6, PDL-1, AXL, GAS6 and APCDD1. Based on pathway analysis software, the development of acquired radioresistance in EMT6RR_MJI was hypothesized through JAK/STAT/PI3K pathway. Presently, CTLA-4 and PD-1 were determined to be associated with JAK/STAT/PI3K pathway, where both their expressions were significantly increased in EMT6RR_MJI compared to parental cells in the 1st, 4th and 8th cycle of radiation. As a conclusion, the current findings provided a mechanistic platform for the development of acquired radioresistance in EMT6RR_MJI through overexpression of CTLA-4 and PD-1, and novel knowledge on therapeutic targets for recurrent radioresistant cancers.

Depletion of SOD2 enhances nasopharyngeal carcinoma cell radiosensitivity via ferroptosis induction modulated by DHODH inhibition

BACKGROUND

Recurrence due to the development of radioresistance remains a major challenge in the clinical management of nasopharyngeal carcinoma. The objective of this study was to increase the sensitivity of nasopharyngeal carcinoma cells to ionizing radiation by enhancing oxidative stress and ferroptosis caused by disrupting the mitochondrial anti-oxidant enzyme system.

METHODS

Oxidative stress cell model was constructed by SOD2 knockdown using shRNA. The expression and activity of DHODH was suppressed by siRNA and brequinar in SOD2 depleted cells. Protein levels were determined by western blotting and ferroptosis was assessed by C11 BODIPY and malondialdehyde assay. Cell viability was evaluated using CCK-8 assay while radiotoxicity was assessed by colony formation assay. Cellular ATP level was determined by ATP assay kits, ROS was determined by DCFD and DHE, while mitochondrial oxygen consumption was determined by seahorse assay. Data were analyzed by two-tailed independent t-test.

RESULTS

Radiation upregulated SOD2 expression and SOD2 depletion increased cellular O2.-, malondialdehyde, and the fluorescence intensity of oxidized C11 BODIPY. It also resulted in mitochondrial damage. Its depletion decreased colony formation both under ionizing and non-ionizing radiation conditions. The ferroptosis inhibitor, deferoxamine, rescued cell viability and colony formation in SOD2 depleted cells. Cellular level of malondialdehyde, fluorescence intensity of oxidized C11 BODIPY, O2.- level, ATP, and mitochondrial oxygen consumption decreased following DHODH inhibition in SOD2 depleted cells. Cell viability and colony formation was rescued by DHODH inhibition in SOD2 depleted cells.

CONCLUSION

Inducing oxidative stress by SOD2 inhibition sensitized nasopharyngeal carcinoma cells to ionizing radiation via ferroptosis induction. This was found to be dependent on DHODH activity. This suggests that DHODH inhibitors should be used with caution during radiotherapy in nasopharyngeal carcinoma patients.

Effect of Shengmai Yin on Epithelial-Mesenchymal Transition of Nasopharyngeal Carcinoma Radioresistant Cells

OBJECTIVE

To investigate the mechanism by which Chinese medicine Shengmai Yin (SMY) reverses epithelial-mesenchymal transition (EMT) through lipocalin-2 (LCN2) in nasopharyngeal carcinoma (NPC) cells CNE-2R.

METHODS

Morphological changes in EMT in CNE-2R cells were observed under a microscope, and the expressions of EMT markers were detected using quantitative real-time PCR (RT-qPCR) and Western blot assays. Through the Gene Expression Omnibus dataset and text mining, LCN2 was found to be highly related to radiation resistance and EMT in NPC. The expressions of LCN2 and EMT markers following SMY treatment (50 and 100 µ g/mL) were detected by RT-qPCR and Western blot assays in vitro. Cell proliferation, migration, and invasion abilities were measured using colony formation, wound healing, and transwell invasion assays, respectively. The inhibitory effect of SMY in vivo was determined by observing a zebrafish xenograft model with a fluorescent label.

RESULTS

The CNE-2R cells showed EMT transition and high expression of LCN2, and the use of SMY (5, 10 and 20 µ g/mL) reduced the expression of LCN2 and reversed the EMT in the CNE-2R cells. Compared to that of the CNE-2R group, the proliferation, migration, and invasion abilities of SMY high-concentration group were weakened (P<0.05). Moreover, SMY mediated tumor growth and metastasis in a dose-dependent manner in a zebrafish xenograft model, which was consistent with the in vitro results.

CONCLUSIONS

SMY can reverse the EMT process of CNE-2R cells, which may be related to its inhibition of LCN2 expression. Therefore, LCN2 may be a potential diagnostic marker and therapeutic target in patients with NPC.

The Promising Therapeutic Approaches for Radiation-Induced Pulmonary Fibrosis: Targeting Radiation-Induced Mesenchymal Transition of Alveolar Type II Epithelial Cells

Radiation-induced pulmonary fibrosis (RIPF) is a common consequence of radiation for thoracic tumors, and is accompanied by gradual and irreversible organ failure. This severely reduces the survival rate of cancer patients, due to the serious side effects and lack of clinically effective drugs and methods. Radiation-induced pulmonary fibrosis is a dynamic process involving many complicated and varied mechanisms, of which alveolar type II epithelial (AT2) cells are one of the primary target cells, and the epithelial-mesenchymal transition (EMT) of AT2 cells is very relevant in the clinical search for effective targets. Therefore, this review summarizes several important signaling pathways that can induce EMT in AT2 cells, and searches for molecular targets with potential effects on RIPF among them, in order to provide effective therapeutic tools for the clinical prevention and treatment of RIPF.

An overview of the intracellular localization of high-Z nanoradiosensitizers

Radiation therapy (RT) is a method commonly used for cancer treatment worldwide. Commonly, RT utilizes two routes for combating cancers: 1) high-energy radiation to generate toxic reactive oxygen species (ROS) (through the dissociation of water molecules) for damaging the deoxyribonucleic acid (DNA) inside the nucleus 2) direct degradation of the DNA. However, cancer cells have mechanisms to survive under intense RT, which can considerably decrease its therapeutic efficacy. Excessive radiation energy damages healthy tissues, and hence, low doses are applied for cancer treatment. Additionally, different radiosensitizers were used to sensitize cancer cells towards RT through individual mechanisms. Following this route, nanoparticle-based radiosensitizers (herein called nanoradiosensitizers) have recently gained attention owing to their ability to produce massive electrons which leads to the production of a huge amount of ROS. The success of the nanoradiosensitizer effect is closely correlated to its interaction with cells and its localization within the cells. In other words, tumor treatment is affected from the chain of events which is started from cell-nanoparticle interaction followed by the nanoparticles direction and homing inside the cell. Therefore, passive or active targeting of the nanoradiosensitizers in the subcellular level and the cell-nano interaction would determine the efficacy of the radiation therapy. The importance of the nanoradiosensitizer's targeting is increased while the organelles beyond nucleus are recently recognized as the mediators of the cancer cell death or resistance under RT. In this review, the principals of cell-nanomaterial interactions and which dominate nanoradiosensitizer efficiency in cancer therapy, are thoroughly discussed.

Vimentin and tumor-stroma ratio for neoadjuvant chemoradiotherapy response prediction in locally advanced rectal cancer

Vimentin expression in tumor tissues and the tumor-stroma ratio (TSR) have been demonstrated as strong prognostic factors for cancer patients, but whether they are predictive markers of neoadjuvant chemoradiotherapy (nCRT) outcome in locally advanced rectal cancer (LARC) patients is poorly understood. This study aimed to explore the predictive significance of vimentin and TSR combined for nCRT response in LARC patients. Imaging mass cytometry (IMC) was performed to determine the association of vimentin and TSR with nCRT response in six LARC patients [three achieved pathological complete response (pCR), three did not]. Immunohistochemistry (IHC) for vimentin and TSR on biopsy tissues before nCRT and logistic regression analysis were performed to further evaluate their predictive value for treatment responses in a larger patient cohort. A trend of decreased vimentin expression and increased TSR in the pCR group was revealed by IMC. In the validation group, vimentin [odds ratio (OR) 0.260, 95% confidence interval (CI) 0.102-0.602, p = 0.002] and TSR (OR 4.971, 95% CI 1.933-15.431, p = 0.002) were associated with pCR by univariate analysis. Patients in the vimentin-low/TSR-low or vimentin-high/TSR-high (OR 5.211, 95% CI 1.248-35.582, p = 0.042) and vimentin-low/TSR-high groups (OR 11.846, 95% CI 3.197-77.079, p = 0.001) had significantly higher odds of pCR. By multivariate analysis, only the combination of vimentin and TSR was an independent predictor for nCRT response (OR 9.324, 95% CI 2.290-63.623, p = 0.006). Our study suggested that the combined assessment of vimentin and TSR can provide additive significance and may be a promising indicator of nCRT response in LARC patients.

C10orf55, CASC2, and SFTA1P lncRNAs Are Potential Biomarkers to Assess Radiation Therapy Response in Head and Neck Cancers

Long non-coding RNAs have proven to be important molecules in carcinogenesis. Due to little knowledge about them, the molecular mechanisms of tumorigenesis are still being explored. The aim of this work was to study the effect of ionizing radiation on the expression of lncRNAs in head and neck squamous cell carcinoma (HNSCC) in patients responding and non-responding to radiotherapy. The experimental model was created using a group of patients with response (RG, n = 75) and no response (NRG, n = 75) to radiotherapy based on the cancer genome atlas (TCGA) data. Using the in silico model, statistically significant lncRNAs were defined and further validated on six HNSCC cell lines irradiated at three different doses. Based on the TCGA model, C10orf55, C3orf35, C5orf38, CASC2, MEG3, MYCNOS, SFTA1P, SNHG3, and TMEM105, with the altered expression between the RG and NRG were observed. Analysis of pathways and immune profile indicated that these lncRNAs were associated with changes in processes, such as epithelial-to-mesenchymal transition, regulation of spindle division, and the p53 pathway, and differences in immune cells score and lymphocyte infiltration signature score. However, only C10orf55, CASC2, and SFTA1P presented statistically altered expression after irradiation in the in vitro model. In conclusion, the expression of lncRNAs is affected by ionization radiation in HNSCC, and these lncRNAs are associated with pathways, which are important for radiation response and immune response. Potentially presented lncRNAs could be used as biomarkers for personalized radiotherapy in the future. However, these results need to be verified based on an in vitro experimental model to show a direct net of interactions.

Current Landscape of Therapeutic Resistance in Lung Cancer and Promising Strategies to Overcome Resistance

Lung cancer is one of the leading causes of cancer-related deaths worldwide with a 5-year survival rate of less than 18%. Current treatment modalities include surgery, chemotherapy, radiation therapy, targeted therapy, and immunotherapy. Despite advances in therapeutic options, resistance to therapy remains a major obstacle to the effectiveness of long-term treatment, eventually leading to therapeutic insensitivity, poor progression-free survival, and disease relapse. Resistance mechanisms stem from genetic mutations and/or epigenetic changes, unregulated drug efflux, tumor hypoxia, alterations in the tumor microenvironment, and several other cellular and molecular alterations. A better understanding of these mechanisms is crucial for targeting factors involved in therapeutic resistance, establishing novel antitumor targets, and developing therapeutic strategies to resensitize cancer cells towards treatment. In this review, we summarize diverse mechanisms driving resistance to chemotherapy, radiotherapy, targeted therapy, and immunotherapy, and promising strategies to help overcome this therapeutic resistance.

GDF15 Contributes to Radioresistance by Mediating the EMT and Stemness of Breast Cancer Cells

Radiotherapy is one of the conventional methods for the clinical treatment of breast cancer. However, radioresistance has an adverse effect on the prognosis of breast cancer patients after radiotherapy. In this study, using bioinformatic analysis of GSE59732 and GSE59733 datasets in the Gene Expression Omnibus (GEO) database together with the prognosis database of breast cancer patients after radiotherapy, the GDF15 gene was screened out to be related to the poor prognosis of breast cancer after radiotherapy. Compared with radiosensitive parental breast cancer cells, breast cancer cells with acquired radioresistance exhibited a high level of GDF15 expression and enhanced epithelial-to-mesenchymal transition (EMT) properties of migration and invasion, as well as obvious stem-like traits, including the increases of mammosphere formation ability, the proportion of stem cells (CD44⁺ CD24^- cells), and the expressions of stem cell-related markers (SOX2, NANOG). Moreover, knockdown of GDF15 sensitized the radioresistance cells to irradiation and significantly inhibited their EMT and stem-like traits, indicating that GDF15 promoted the radioresistance of breast cancer by enhancing the properties of EMT and stemness. Conclusively, GDF15 may be applicable as a novel prognosis-related biomarker and a potential therapeutic target for breast cancer radiotherapy.

Non-tumorigenic epithelial breast cells and ionizing radiation cooperate in the enhancement of mesenchymal traits in tumorigenic breast cancer cells

AIMS

Radioresistance and recurrences are crucial hindrances in cancer radiotherapy. Fractionated irradiation can elicit a mesenchymal phenotype in irradiated surviving cells and a deep connection exists between epithelial mesenchymal transition, radioresistance, and metastasis. The aim of this study was to analyze the effect of the secretoma of irradiated non-tumorigenic mammary epithelial cells on surviving irradiated breast tumor cells regarding the gain of mesenchymal traits and migratory ability.

MAIN METHODS

MDA-MB-231 and MCF-7 breast cancer cells, irradiated or not, were incubated with conditioned media from MCF-10A non-tumorigenic epithelial breast cells, irradiated or not. After five days, we evaluated the expression and localization of epithelial and mesenchymal markers (by western blot and indirect immunofluorescence), cell migration (using transwells) and metalloproteinases activity (by zymography). We also assessed TGF-β1 content in conditioned media by immunoblot, and the effect of A83-01 (a selective inhibitor of TGF-β receptor I) and PP2 (a Src-family tyrosine kinase inhibitor) on nuclear Slug and cell migration.

KEY FINDINGS

Conditioned media from MCF-10A cells caused phenotypic changes in breast tumor cells with attainment or enhancement of mesenchymal traits mediated at least in part by the activation of the TGF-β type I receptor and a signaling pathway involving Src activation/phosphorylation. The effects were more pronounced mostly in irradiated tumor cells treated with conditioned media from irradiated MCF-10A.

SIGNIFICANCE

Our results suggest that non-tumorigenic epithelial mammary cells included in the irradiation field could affect the response to irradiation of post-surgery residual cancer cells enhancing EMT progression and thus modifying radiotherapy efficacy.

Epithelial-Mesenchymal Transition-Mediated Tumor Therapeutic Resistance

Cancer is one of the world’s most burdensome diseases, with increasing prevalence and a high mortality rate threat. Tumor recurrence and metastasis due to treatment resistance are two of the primary reasons that cancers have been so difficult to treat. The epithelial–mesenchymal transition (EMT) is essential for tumor drug resistance. EMT causes tumor cells to produce mesenchymal stem cells and quickly adapt to various injuries, showing a treatment-resistant phenotype. In addition, multiple signaling pathways and regulatory mechanisms are involved in the EMT, resulting in resistance to treatment and hard eradication of the tumors. The purpose of this study is to review the link between EMT, therapeutic resistance, and the molecular process, and to offer a theoretical framework for EMT-based tumor-sensitization therapy.

Inhibition of PDK1 enhances radiosensitivity and reverses epithelial-mesenchymal transition in nasopharyngeal carcinoma

BACKGROUND

Radioresistance challenges the clinical outcomes of nasopharyngeal carcinoma (NPC). The 3-phosphoinositide-dependent protein kinase 1 (PDK1) is a crucial kinase of PI3K/AKT signaling pathway which has been implicated in the process of radioresistance. However, the role of PDK1 in NPC remains largely unclear.

METHODS

The expression of PDK1 was determined by immunohistochemistry and Western blot. The effects of RNA interference and pharmacologic inhibitor of PDK1 in combination with irradiation were investigated.

RESULTS

Overexpression of PDK1 was correlated with poor prognosis in patients with NPC. PDK1 depletion enhanced radiosensitivity of NPC cells both in vitro and in vivo. Additionally, a specific PDK1 inhibitor also had the potential to enhance radiosensitivity in radioresistant NPC cells. Mechanistically, PDK1 depletion inhibited various targets of AKT including mTOR and GSK-3β and reversed the epithelial-mesenchymal transition.

CONCLUSIONS

These findings indicated that PDK1 might be a potential target for NPC.

Role of vitamin D3 in tumor aggressiveness and radiation response for hepatocellular carcinoma

Locoregional control is a significant prognostic factor for hepatocellular carcinoma (HCC). Historically, the use of radiotherapy (RT) for HCC was limited owing to the low radiotolerance of the liver and the need for high RT doses for disease control. We aimed to examine if 1α,25-dihydroxyvitamin D3 (calcitriol) has a role in the tumor inhibition and the radiation response of HCC in vitro and in vivo, and explore the underlying mechanisms. The human and murine liver cancer cell lines were selected for cellular and animal experiments to investigate the changes in tumor characteristics and the radiation response after calcitriol supplementation. The effects induced by calcitriol supplementation on interleukin-6 (IL-6) signaling and the tumor immune microenvironment following RT were also examined. Our data revealed that calcitriol supplementation attenuated tumor aggressive behavior, decrease IL-6 expression, and augmented radiation-induced tumor inhibition. The biological changes following calcitriol treatment included suppressed epithelial-mesenchymal transition, attenuated cancer stem cell-like properties and increased radiation-induced reactive oxygen species and cell death in vitro. Regarding immune microenvironment, calcitriol attenuated the recruitment of myeloid-derived suppressor cell (MDSC) recruitment and increased the infiltration of cytotoxic T cells in tumor following RT. Furthermore, When the primary liver tumor was irradiated with larger dose per fraction, calcitriol induced a smaller size of synchronous unirradiated tumor in mice, which linked with attenuated IL-6 signaling and MDSC recruitment. In conclusion, calcitriol treatment reduced tumor aggressiveness and enhanced the radiation response. The inhibited IL-6 signaling and subsequently enhanced antitumor immunity might be responsible to augment radiation-induced tumoricidal effect induced by calcitriol. Based on our results, we suggest that calcitriol could exert the antitumor and radiosensitization effects for HCC, especially for multifocal tumors.

Role of H2A.Z.1 in epithelial-mesenchymal transition and radiation resistance of lung adenocarcinoma in vitro

Radiation resistance reduces patient survival and is an important challenge in treating lung adenocarcinoma (LUAD). Previous studies have shown that histone H2A variants can affect the radiosensitivity of tumors; however, the main role of histone H2A variants in LUAD remains unclear. Using the TCGA database, we found that histone H2A variant H2A.Z.1 is positively associated with the progression and poor prognosis of LUAD. Colony formation, scratch wound-healing, and transwell assays as well as Western blot were performed to assess the role of H2A.Z.1 in vitro. Results suggested that H2A.Z.1 promoted cell migration and invasion, epithelial-mesenchymal transition, stemness, and radiation resistance in LUAD cells. Targeting H2A.Z.1 in combination with radiation therapy could be a potential therapeutic approach for radiation resistant LUAD.

Targeting Epithelial-to-Mesenchymal Transition in Radioresistance: Crosslinked Mechanisms and Strategies

Radiotherapy exerts a crucial role in curing cancer, however, its treatment efficiency is mostly limited due to the presence of radioresistance. Epithelial-to-mesenchymal transition (EMT) is a biological process that endows the cancer cells with invasive and metastatic properties, as well as radioresistance. Many potential mechanisms of EMT-related radioresistance being reported have broaden our cognition, and hint us the importance of an overall understanding of the relationship between EMT and radioresistance. This review focuses on the recent progresses involved in EMT-related mechanisms in regulating radioresistance, irradiation-mediated EMT program, and the intervention strategies to increase tumor radiosensitivity, in order to improve radiotherapy efficiency and clinical outcomes of cancer patients.

A Century of Fractionated Radiotherapy: How Mathematical Oncology Can Break the Rules

Radiotherapy is involved in 50% of all cancer treatments and 40% of cancer cures. Most of these treatments are delivered in fractions of equal doses of radiation (Fractional Equivalent Dosing (FED)) in days to weeks. This treatment paradigm has remained unchanged in the past century and does not account for the development of radioresistance during treatment. Even if under-optimized, deviating from a century of successful therapy delivered in FED can be difficult. One way of exploring the infinite space of fraction size and scheduling to identify optimal fractionation schedules is through mathematical oncology simulations that allow for in silico evaluation. This review article explores the evidence that current fractionation promotes the development of radioresistance, summarizes mathematical solutions to account for radioresistance, both in the curative and non-curative setting, and reviews current clinical data investigating non-FED fractionated radiotherapy.

Research Progress of Epithelial-mesenchymal Transition Treatment and Drug Resistance in Colorectal Cancer

Colorectal cancer (CRC) is one of the most common malignancies in the world that seriously affects human health. Activation of epithelial-mesenchymal transition (EMT) is a physiological phenomenon during embryonic development that is essential for cell metastasis. EMT participates in various biological processes associated with trauma repair, organ fibrosis, migration, metastasis, and infiltration of tumor cells. EMT is a new therapeutic target for CRC; however, some patients with CRC develop resistance to some drugs due to EMT. This review focuses specifically on the status of treatments that target the EMT process and its role in the therapeutic resistance observed in patients with CRC.

Mutation Analysis of Radioresistant Early-Stage Cervical Cancer

Radiotherapy is a definitive treatment for early-stage cervical cancer; however, a subset of this disease recurs locally, necessitating establishment of predictive biomarkers and treatment strategies. To address this issue, we performed gene panel-based sequencing of 18 stage IB cervical cancers treated with definitive radiotherapy, including two cases of local recurrence, followed by in vitro and in silico analyses. Simultaneous mutations in KRAS and SMAD4 (KRASmt/SMAD4mt) were detected only in a local recurrence case, indicating potential association of this mutation signature with radioresistance. In isogenic cell-based experiments, a combination of activating KRAS mutation and SMAD4 deficiency led to X-ray resistance, whereas either of these factors alone did not. Analysis of genomic data from 55,308 cancers showed a significant trend toward co-occurrence of mutations in KRAS and SMAD4. Gene Set Enrichment Analysis of the Cancer Cell Line Encyclopedia dataset suggested upregulation of the pathways involved in epithelial mesenchymal transition and inflammatory responses in KRASmt/SMAD4mt cancer cells. Notably, irradiation with therapeutic carbon ions led to robust killing of X-ray-resistant KRASmt/SMAD4mt cancer cells. These data indicate that the KRASmt/SMAD4mt signature is a potential predictor of radioresistance, and that carbon ion radiotherapy is a potential option to treat early-stage cervical cancers with the KRASmt/SMAD4mt signature.

LASP1 Induces Epithelial-Mesenchymal Transition in Lung Cancer through the TGF-β1/Smad/Snail Pathway

Background. LIM and SH3 domain protein 1 (LASP1), highly expressed in a variety of tumors, is considered as a novel tumor metastasis biomarker. However, it is unknown which signaling pathway works and how the signal transduces into cell nucleus to drive tumor progression by LASP1. The aim of this study is to explore the essential role of LASP1 in TGF-β1-induced epithelial-mesenchymal transition (EMT) in lung cancer cells. Methods. The gene and protein levels of LASP-1 were successfully silenced or overexpressed by LASP-1 shRNA lentivirus or pcDNA in TGF-β1-treated lung cancer cell lines, respectively. Then, the cells were developed EMT by TGF-β1. The cell abilities of invasion, migration, and proliferation were measured using Transwell invasion assay, wound healing assay, and MTT assay, respectively. Western blotting was used to observe the protein levels of EMT-associated molecules, including N-cadherin, vimentin, and E-cadherin, and the key molecules in the TGF-β1/Smad/Snail signaling pathway, including pSmad2 and Smad2, pSmad3 and Smad3, and Smad7 in cell lysates, as well as Snail1, pSmad2, and pSmad3 in the nucleus. Results. TGF-β1 induced higher LASP1 expression. LASP1 silence and overexpression blunted or promoted cell invasion, migration, and proliferation upon TGF-β1 stimulation. LASP1 also regulated the expression of vimentin, N-cadherin, and E-cadherin in TGF-β1-treated cells. Activity of key Smad proteins (pSmad2 and pSmad3) and protein level of Smad7 were markedly regulated through LASP1. Furthermore, LASP1 affected the nuclear localizations of pSmad2, pSmad3, and Snail1. Conclusion. This study reveals that LASP1 regulates the TGF-β1/Smad/Snail signaling pathway and EMT markers and features, involving in key signal molecules and their nuclear levels. Therefore, LASP1 might be a drug target in lung cancer.

EGFR-mediated Rad51 expression potentiates intrinsic resistance in prostate cancer via EMT and DNA repair pathways

AIM

To study the role of EGFR signaling in regulation of intrinsic resistance in prostate cancer.

MATERIALS AND METHODS

Radioresistant prostate carcinoma DU145 and PC-3 cells were used to study the effect of shRNA-mediated knockdown of EGFR on intrinsic radioresistance mechanisms. Semi-quantitative PCR, western blotting, growth kinetics, colony formation, transwell migration, invasion and trypan blue assays along with inhibitors erlotinib, NU7441, B02, PD98059 and LY294002 were used.

KEY FINDINGS

EGFR knock-down induced morphological alterations along with reduction in clonogenic potential and cell proliferation in DU145 cells. Migratory potential of prostate cancer cells were reduced concomitant with upregulation of epithelial marker, E-cadherin and decreased expression of mesenchymal markers, vimentin and snail. Further, EGFR knock-down decreased the expression of Rad51 and DNA-PK at mRNA as well as protein levels. Likewise, erlotinib, an EGFR inhibitor, and NU7441, a DNA-PK inhibitor increased the expression of E-cadherin and decreased the level of vimentin. Both these inhibitors also decreased the levels of DNA damage regulatory protein Rad51. Further, Rad51 inhibitor, B02, inhibited the clonogenic potential, cell migration and reduced the expression of vimentin, Ku70 and Ku80, and also, B02 radiosensitized DU145 cells. EGFR-regulated expression of Rad51 was found to be mediated via PI3K/Akt and Erk1/2 pathways.

SIGNIFICANCE

EGFR was found to regulate DNA damage repair, survival and EMT responses in prostate cancer cells through transcriptional regulation of Rad51. A novel role of EGFR-Erk1/2/Akt-Rad51 axis through modulation of EMT and DNA repair pathways in prostate cancer resistance mechanisms is suggested.

Radioresistance of Human Cancers: Clinical Implications of Genetic Expression Signatures

Although radiotherapy is given to more than 50% of cancer patients, little progress has been made in identifying optimal radiotherapy - drug combinations to improve treatment efficacy. Using molecular data from The Cancer Genome Atlas (TCGA), we extracted a total of 1016 cancer patients that received radiotherapy. The patients were diagnosed with head-and-neck (HNSC - 294 patients), cervical (CESC - 166 patients) and breast (BRCA - 549 patients) cancer. We analyzed mRNA expression patterns of 50 hallmark gene sets of the MSigDB collection, which we divided in eight categories based on a shared biological or functional process. Tumor samples were split into upregulated, neutral or downregulated mRNA expression for all gene sets using a gene set analysis (GSEA) pre-ranked analysis and assessed for their clinical relevance. We found a prognostic association between three of the eight gene set categories (Radiobiological, Metabolism and Proliferation) and overall survival in all three cancer types. Furthermore, multiple single associations were revealed in the other categories considered. To the best of our knowledge, our study is the first report suggesting clinical relevance of molecular characterization based on hallmark gene sets to refine radiation strategies.

Epithelial-to-Mesenchymal Transition-Derived Heterogeneity in Head and Neck Squamous Cell Carcinomas

Simple Summary

Head and neck squamous cell carcinomas (HNSCC) are common malignancies with considerable morbidity and a high death toll worldwide. Resistance towards multi-modal therapy modalities composed of surgery, irradiation, chemo- and immunotherapy represents a major obstacle in the efficient treatment of HNSCC patients. Patients frequently show nodal metastases at the time of diagnosis and endure early relapses, oftentimes in the form of local recurrences. Differentiation programs such as the epithelial-to-mesenchymal transition (EMT) allow individual tumor cells to adopt cellular functions that are central to the development of metastases and treatment resistance. In the present review article, the molecular basis and regulation of EMT and its impact on the progression of HNSCC will be addressed.

Abstract

Head and neck squamous cell carcinomas (HNSCC) are common tumors with a poor overall prognosis. Poor survival is resulting from limited response to multi-modal therapy, high incidence of metastasis, and local recurrence. Treatment includes surgery, radio(chemo)therapy, and targeted therapy specific for EGFR and immune checkpoint inhibition. The understanding of the molecular basis for the poor outcome of HNSCC was improved using multi-OMICs approaches, which revealed a strong degree of inter- and intratumor heterogeneity (ITH) at the level of DNA mutations, transcriptome, and (phospho)proteome. Single-cell RNA-sequencing (scRNA-seq) identified RNA-expression signatures related to cell cycle, cell stress, hypoxia, epithelial differentiation, and a partial epithelial-to-mesenchymal transition (pEMT). The latter signature was correlated to nodal involvement and adverse clinical features. Mechanistically, shifts towards a mesenchymal phenotype equips tumor cells with migratory and invasive capacities and with an enhanced resistance to standard therapy. Hence, gradual variations of EMT as observed in HNSCC represent a potent driver of tumor progression that could open new paths to improve the stratification of patients and to innovate approaches to break therapy resistance. These aspects of molecular heterogeneity will be discussed in the present review.

Radiation-Induced Fibrotic Tumor Microenvironment Regulates Anti-Tumor Immune Response

Simple Summary

Radiation therapy can modulate anti-tumor immune responses. In this study, we investigated the relationship between the anti-tumor immune response and tumor fibrosis after X-ray or neutron radiation therapy. Neutron radiation therapy resulted in lesser fibrosis and greater anti-tumor immunity compared to X-ray irradiation. Radiation therapy-induced fibrotic changes within the tumor environment and tumor regrowth were suppressed by specifically deleting Trp53 in endothelial cells. In particular, the upregulation of PD-L1 expression after X-ray radiation therapy was significantly suppressed via EC-Trp53 deletion. Understanding the effects of different radiation therapy types on the tumor microenvironment provides strategies for enhancing the efficacy of combined radio- and immunotherapy.

Abstract

High linear energy transfer (LET) radiation, such as neutron radiation, is considered more effective for the treatment of cancer than low LET radiation, such as X-rays. We previously reported that X-ray irradiation induced endothelial-to-mesenchymal transition (EndMT) and profibrotic changes, which contributed to the radioresistance of tumors. However, this effect was attenuated in tumors of endothelial-specific Trp53-knockout mice. Herein, we report that compared to X-ray irradiation, neutron radiation therapy reduced collagen deposition and suppressed EndMT in tumors. In addition to the fewer fibrotic changes, more cluster of differentiation (CD8)-positive cytotoxic T cells were observed in neutron-irradiated regrowing tumors than in X-ray-irradiated tumors. Furthermore, lower programmed death-ligand 1 (PD-L1) expression was noted in the former. Endothelial-specific Trp53 deletion suppressed fibrotic changes within the tumor environment following both X-ray and neutron radiation therapy. In particular, the upregulation in PD-L1 expression after X-ray radiation therapy was significantly dampened. Our findings suggest that compared to low LET radiation therapy, high LET radiation therapy can efficiently suppress profibrotic changes and enhance the anti-tumor immune response, resulting in delayed tumor regrowth.

TGF-beta signaling in cancer radiotherapy

Transforming growth factor beta (TGF-β) plays key roles in regulating cellular proliferation and maintaining tissue homeostasis. TGF-β exerts tumor-suppressive effects in the early stages of carcinogenesis, but it also plays tumor-promoting roles in established tumors. Additionally, it plays a critical role in cancer radiotherapy. TGF-β expression or activation increases in irradiated tissues, and studies have shown that TGF-β plays dual roles in cancer radiosensitivity and is involved in ionizing radiation-induced fibrosis in different tumor microenvironments (TMEs). Furthermore, TGF-β promotes radioresistance by inducing the epithelial-mesenchymal transition (EMT), cancer stem cells (CSCs) and cancer-associated fibroblasts (CAFs), suppresses the immune system and facilitates cancer resistance. In particular, the links between TGF-β and the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) axis play a critical role in cancer therapeutic resistance. Growing evidence has shown that TGF-β acts as a radiation protection agent, leading to heightened interest in using TGF-β as a therapeutic target. The future of anti-TGF-β signaling therapy for numerous diseases appears bright, and the outlook for the use of TGF-β inhibitors in cancer radiotherapy as TME-targeting agents is promising.

MiR-155 Inhibitor-Laden Exosomes Reverse Resistance to Cisplatin in a 3D Tumor Spheroid and Xenograft Model of Oral Cancer

Cisplatin resistance is one of the major concerns in the treatment of oral squamous cell carcinoma (OSCC). Accumulating evidence suggests microRNA (miRNA) dysregulation as one of the mediators of chemoresistance. Toward this, our previous study revealed the role of exosomal microRNA-155 (miR-155) in cisplatin resistance via downregulation of FOXO3a, a direct target of miR-155, and induction of epithelial-to-mesenchymal transition in OSCC. In the present study, we demonstrate the therapeutic potential of miR-155 inhibitor-laden exosomes in the sensitization of a cisplatin-resistant (cis^Res) OSCC 3D tumor spheroid and xenograft mouse model. The cis^Res OSSC 3D tumor spheroid model recapitulated the hallmarks of solid tumors such as enhanced hypoxia, reactive oxygen species, and secretory vascular endothelial growth factor. Further treatment with miR-155 inhibitor-loaded exosomes showed the upregulation of FOXO3a and induction of the mesenchymal-to-epithelial transition with improved sensitization to cisplatin in cis^Res tumor spheroids and xenograft mouse model. Moreover, the exosomal miR-155 inhibitor suppressed the stem-cell-like property as well as drug efflux transporter protein expression in cisplatin-resistant tumors. Taken together, our findings, for the first time, established that the miR-155 inhibitor-loaded exosomes reverse chemoresistance in oral cancer, thereby providing an alternative therapeutic strategy for the management of refractory oral cancer patients.

G protein-coupled estrogen receptor 1 inhibits the epithelial-mesenchymal transition of goat mammary epithelial cells via NF-κB signalling pathway

Mastitis is one of the most frequent clinical diseases in dairy animals. Epithelial cells undergoing epithelial-mesenchymal transition (EMT) promote the process of mastitis. Oestrogen deficiency is disadvantaged of many tissue inflammation and regeneration, while exogenous oestrogen treatment can reverse these effects. G protein-coupled estrogen receptor 1 (GPER1) is a membrane estrogen receptor. However, the potential effects of oestrogen via GPER1 on EMT in goat mammary epithelial cells (GMECs) are still unclear. Here, this study discovered that the activation of GPER1 by oestrogen could inhibit the EMT in GMECs via NF-κB signalling pathway. The activation of GPER1 by oestrogen inhibited the EMT accompanied by upregulation of E-cadherin and downregulation of N-cadherin and vimentin. Meanwhile, mRNA expression of transcription factors including Snail1 and ZEB1 was decreased. Further, like to oestrogen, GPER1 agonist G1 repressed the EMT progression. Conversely, GPER1 antagonist G15 reversed all these features induced by oestrogen. What's more, GPER1 silencing with shRNA promoted GMECs undergoing EMT. Additionally, oestrogen increased the phosphorylation of Erk1/2, which then decreased the phosphorylation and nuclear translocation of NF-κB, inhibiting the NF-κB signalling pathway activity. Taken, GPER1 may act as a suppressor through the regulation of EMT to prevent the development of mastitis.

miR-221-3p and miR-222-3p regulate the SOCS3/STAT3 signaling pathway to downregulate the expression of NIS and reduce radiosensitivity in thyroid cancer

The expression levels of microRNA (miR)-221-3p and miR-222-3p in thyroid cancer have been found to be upregulated compared with those in normal tissues. The present study aimed to determine the effects and potential underlying mechanisms of miR-221-3p and miR-222-3p on the regulation of radioactive iodine (131I) uptake and radiosensitivity of thyroid cancer cells. The potential regulatory target genes of miR-221-3p and miR-222-3p were predicted by bioinformatics analysis, and reverse transcription-quantitative polymerase chain reaction was used to verify miR-221-3p, miR-222-3p and target gene expression levels in thyroid cancer tissues and cell lines. Overexpression of miR-221-3p or miR-222-3p in cell models was performed using lentivirus infection. Knockdown of miR-221-3p and miR-222-3p in cells was achieved using oligonucleotide inhibitor transfection. Western blotting was used to analyze the expression levels of target proteins. In addition, the effects of miR-221-3p and miR-222-3p on the radiosensitivity of thyroid cancer cells were verified using a colony formation assay. The results of the present study revealed that the expression levels of miR-221-3p and miR-222-3p were significantly upregulated, while the expression levels of suppressor of cytokine signaling 3 (SOCS3) were downregulated in thyroid cancer tissues. Furthermore, miR-221-3p and miR-222-3p overexpression downregulated the expression levels of SOCS3, E-cadherin and solute carrier family 5 member 5 (NIS), and upregulated the expression levels of phosphorylated STAT3 and vimentin. Following the overexpression of miR-221-3p or miR-222-3p in the FTC133 and TPC1 cell lines, their radiosensitivity was suppressed. In conclusion, the findings of the present study suggested that miR-221-3p and miR-222-3p may downregulate the expression levels of NIS and promote radioresistance. The potential mechanism was hypothesized to be associated with the miR-221-3p and miR-222-3p targeting of the SOCS3 gene, which may subsequently activate the STAT3 signaling pathway.

Effect of 1α,25-Dihydroxyvitamin D3 on the Radiation Response in Prostate Cancer: Association With IL-6 Signaling

Radiotherapy (RT) is the main treatment modality for prostate cancer (PCa). This study investigated the role of IL-6 in biological sequelae following irradiation and highlighted the effects of 1α,25-dihydroxyvitamin D3 (calcitriol) on the radiation response of PCa and its relationship with IL-6 signaling. Human and murine PCa cell lines were used to examine the response to irradiation in vitro and in vivo. The relationship of IL-6 expression with clinicopathologic characteristics in 104 PCa patients treated with definite RT was also examined. We also investigated the changes in radiation response after calcitriol supplementation and the relationship between calcitriol and IL-6 signaling by conducting cellular and animal experiments. Based on clinical samples, the positivity of IL-6 staining is a significant predictor of biochemical failure-free survival for PCa patients treated with definite RT. Data from preclinical models showed that inhibition of IL-6 increased the response of PCa to radiation, which was associated with increased oxidative DNA damage, attenuated EMT and MDSC recruitment, and decreased tumor regrowth. Moreover, increased vitamin D₃ levels by calcitriol supplementation or induction by UVB-radiation was associated with inhibited IL-6 signaling and increased the response to irradiation observed in animal models. These data demonstrate that IL-6 play a critical role in the radiation response of PCa, which involved tumor cell killing and altering the tumor microenvironment. Directly targeting IL-6 signaling or vitamin D₃ supplement with oral or light treatment could be a promising strategy to increase the response of PCa to radiation.

Tumor resistance to radiotherapy is triggered by an ATM/TAK1-dependent-increased expression of the cellular prion protein

In solid cancers, high expression of the cellular prion protein (PrPC) is associated with stemness, invasiveness, and resistance to chemotherapy, but the role of PrPC in tumor response to radiotherapy is unknown. Here, we show that, in neuroblastoma, breast, and colorectal cancer cell lines, PrPC expression is increased after ionizing radiation (IR) and that PrPC deficiency increases radiation sensitivity and decreases radiation-induced radioresistance in tumor cells. In neuroblastoma cells, IR activates ATM that triggers TAK1-dependent phosphorylation of JNK and subsequent activation of the AP-1 transcription factor that ultimately increases PRNP promoter transcriptional activity through an AP-1 binding site in the PRNP promoter. Importantly, we show that this ATM-TAK1-PrPC pathway mediated radioresistance is activated in all tumor cell lines studied and that pharmacological inhibition of TAK1 activity recapitulates the effects of PrPC deficiency. Altogether, these results unveil how tumor cells activate PRNP to acquire resistance to radiotherapy and might have implications for therapeutic targeting of solid tumors radioresistance.