Predictive value of epithelial-mesenchymal-transition (EMT) signature and PARP-1 in prostate cancer radioresistance

A glimpse into cofilin-1 role in cancer therapy: A potential target to improve clinical outcomes?

Cofilin-1 (CFL1) modulates dynamic actin networks by severing and enhancing depolymerization. The upregulation of cofilin-1 expression in several cancer types is associated with tumor progression and metastasis. However, recent discoveries indicated relevant cofilin-1 functions under oxidative stress conditions, interplaying with mitochondrial dynamics, and apoptosis networks. In this scenario, these emerging roles might impact the response to clinical therapy and could be used to enhance treatment efficacy. Here, we highlight new perspectives of cofilin-1 in the therapy resistance context and discussed how cofilin-1 is involved in these events, exploring aspects of its contribution to therapeutic resistance. We also provide an analysis of CFL1 expression in several tumors predicting survival. Therefore, understanding how exactly coflin-1 plays, particularly in therapy resistance, may pave the way to the development of treatment strategies and improvement of patient survival.

High Expression of PARP1 in Tumor and Stroma Cells Predicts Different Prognosis and Platinum Resistance in Patients With Advanced Epithelial Ovarian Cancer

Objective

This study aimed to explore the roles of PARP1 mRNA and protein expression in platinum resistance and prognosis of EOC patients, and reveal the different roles of PARP1 protein in epithelial tumor and stroma cells.

Methods

The PARP1 mRNA expression of the EOC tissues was examined by RT-qPCR. The impacts of PARP1 expression on prognosis were measured by Kaplan-Meier and Cox regression. Receiver operating characteristic (ROC) curve analysis was employed for calculating the diagnostic value of PARP1 on platinum resistance. The microarray of formalin-fixed, paraffin-embedded (FFPE) tissues was processed for multiplex immunofluorescence to detect the protein levels of PARP1 and cytokeratin (CK).

Results

The PARP1mRNA expression of EOC patients was higher in the platinum-resistant group compared with the sensitive group (P<0.01). Kaplan-Meier analysis demonstrated that high PARP1 mRNA expression was associated with poor survival of EOC patients. In Cox regression analyses, high PARP1 mRNA expression independently predicted poor prognosis (P=0.001, HR=2.076, 95%CI=1.373-3.140). The area under the ROC curve of PARP1 mRNA for predicting the platinum resistance in EOC patients was 0.649, with a sensitivity of 0.607 and specificity of 0.668. Furthermore, the protein expression of PARP1 was higher in the platinum-resistant group than in the sensitive group (P<0.01) and associated with a worse prognosis. Additionally, according to CK labeling, we observed that enhanced expression of PARP1 in the CK+ region was associated with platinum resistance and lower survival, but in CK- region, it predicted a good prognosis and platinum sensitivity.

Conclusion

PARP1 may be a potential biomarker to predict platinum resistance and prognosis for EOC patients, exerting different roles on epithelial tumor and stromal cells.

Epithelial–mesenchymal transition: The history, regulatory mechanism, and cancer therapeutic opportunities

Epithelial–mesenchymal transition (EMT) is a program wherein epithelial cells lose their junctions and polarity while acquiring mesenchymal properties and invasive ability. Originally defined as an embryogenesis event, EMT has been recognized as a crucial process in tumor progression. During EMT, cell–cell junctions and cell–matrix attachments are disrupted, and the cytoskeleton is remodeled to enhance mobility of cells. This transition of phenotype is largely driven by a group of key transcription factors, typically Snail, Twist, and ZEB, through epigenetic repression of epithelial markers, transcriptional activation of matrix metalloproteinases, and reorganization of cytoskeleton. Mechanistically, EMT is orchestrated by multiple pathways, especially those involved in embryogenesis such as TGFβ, Wnt, Hedgehog, and Hippo, suggesting EMT as an intrinsic link between embryonic development and cancer progression. In addition, redox signaling has also emerged as critical EMT modulator. EMT confers cancer cells with increased metastatic potential and drug resistant capacity, which accounts for tumor recurrence in most clinic cases. Thus, targeting EMT can be a therapeutic option providing a chance of cure for cancer patients. Here, we introduce a brief history of EMT and summarize recent advances in understanding EMT mechanisms, as well as highlighting the therapeutic opportunities by targeting EMT in cancer treatment.

Transforming growth factor-beta (TGF-β) in prostate cancer: A dual function mediator?

Transforming growth factor-beta (TGF-β) is a member of a family of secreted cytokines with vital biological functions in cells. The abnormal expression of TGF-β signaling is a common finding in pathological conditions, particularly cancer. Prostate cancer (PCa) is one of the leading causes of death among men. Several genetic and epigenetic alterations can result in PCa development, and govern its progression. The present review attempts to shed some light on the role of TGF-β signaling in PCa. TGF-β signaling can either stimulate or inhibit proliferation and viability of PCa cells, depending on the context. The metastasis of PCa cells is increased by TGF-β signaling via induction of EMT and MMPs. Furthermore, TGF-β signaling can induce drug resistance of PCa cells, and can lead to immune evasion via reducing the anti-tumor activity of cytotoxic T cells and stimulating regulatory T cells. Upstream mediators such as microRNAs and lncRNAs, can regulate TGF-β signaling in PCa. Furthermore, some pharmacological compounds such as thymoquinone and valproic acid can suppress TGF-β signaling for PCa therapy. TGF-β over-expression is associated with poor prognosis in PCa patients. Furthermore, TGF-β up-regulation before prostatectomy is associated with recurrence of PCa. Overall, current review discusses role of TGF-β signaling in proliferation, metastasis and therapy response of PCa cells and in order to improve knowledge towards its regulation, upstream mediators of TGF-β such as non-coding RNAs are described. Finally, TGF-β regulation and its clinical application are discussed.

Plasticity within aldehyde dehydrogenase-positive cells determines prostate cancer radiosensitivity

Tumor heterogeneity and cellular plasticity are key determinants of tumor progression, metastatic spread and therapy response driven by the cancer stem cell (CSC) population. Within the present study, we analyzed irradiation-induced plasticity within the aldehyde dehydrogenase (ALDH)-positive population in prostate cancer (PCa). The radiosensitivity of xenograft tumors derived from ALDH+ and ALDH- cells was determined with local tumor control analyses and demonstrated different dose-response profiles, time to relapse and focal adhesion signaling. The transcriptional heterogeneity was analyzed in pools of ten DU145 and PC3 cells with multiplex gene expression analyses and illustrated a higher degree of heterogeneity within the ALDH+ population that even increases upon irradiation in comparison to ALDH- cells. Phenotypic conversion and clonal competition were analyzed with fluorescence protein-labeled cells to distinguish cellular origins in competitive 3D cultures and xenograft tumors. We found that the ALDH+ population outcompetes ALDH- cells and drives tumor growth, in particular upon irradiation. The observed dynamics of the cellular state compositions between ALDH+ and ALDH- cells in vivo before and after tumor irradiation was reproduced by a probabilistic Markov compartment model that incorporates cellular plasticity, clonal competition and phenotype-specific radiosensitivities. Transcriptional analyses indicate that the cellular conversion from ALDH- into ALDH+ cells within xenograft tumors under therapeutic pressure was partially mediated through induction of the transcriptional repressor SNAI2. In summary, irradiation-induced cellular conversion events are present in xenograft tumors derived from PCa cells and may be responsible for radiotherapy failure.

Identification of a Four-Gene-Based SERM Signature for Prognostic and Drug Sensitivity Prediction in Gastric Cancer

Background

Gastric cancer (GC) is a highly molecular heterogeneous tumor with poor prognosis. Epithelial-mesenchymal transition (EMT) process and cancer stem cells (CSCs) are reported to share common signaling pathways and cause poor prognosis in GC. Considering about the close relationship between these two processes, we aimed to establish a gene signature based on both processes to achieve better prognostic prediction in GC.

Methods

The gene signature was constructed by univariate Cox and the least absolute shrinkage and selection operator (LASSO) Cox regression analyses by using The Cancer Genome Atlas (TCGA) GC cohort. We performed enrichment analyses to explore the potential mechanisms of the gene signature. Kaplan-Meier analysis and time-dependent receiver operating characteristic (ROC) curves were implemented to assess its prognostic value in TCGA cohort. The prognostic value of gene signature on overall survival (OS), disease-free survival (DFS), and drug sensitivity was validated in different cohorts. Quantitative reverse transcription polymerase chain reaction (RT-qPCR) validation of the prognostic value of gene signature for OS and DFS prediction was performed in the Fudan cohort.

Results

A prognostic signature including SERPINE1, EDIL3, RGS4, and MATN3 (SERM signature) was constructed to predict OS, DFS, and drug sensitivity in GC. Enrichment analyses illustrated that the gene signature has tight connection with the CSC and EMT processes in GC. Patients were divided into two groups based on the risk score obtained from the formula. The Kaplan-Meier analyses indicated high-risk group yielded significantly poor prognosis compared with low-risk group. Pearson’s correlation analysis indicated that the risk score was positively correlated with carboplatin and 5-fluorouracil IC50 of GC cell lines. Multivariate Cox regression analyses showed that the gene signature was an independent prognostic factor for predicting GC patients’ OS, DFS, and susceptibility to adjuvant chemotherapy.

Conclusions

Our SERM prognostic signature is of great value for OS, DFS, and drug sensitivity prediction in GC, which may give guidance to the development of targeted therapy for CSC- and EMT-related gene in the future.

CTCF Expression and Dynamic Motif Accessibility Modulates Epithelial-Mesenchymal Gene Expression

Epithelial-mesenchymal transition (EMT) and its reversal, mesenchymal-epithelial transition (MET) drive tissue reorganization critical for early development. In carcinomas, processing through EMT, MET, or partial states promotes migration, invasion, dormancy, and metastatic colonization. As a reversible process, EMT is inherently regulated at epigenetic and epigenomic levels. To understand the epigenomic nature of reversible EMT and its partial states, we characterized chromatin accessibility dynamics, transcriptomic output, protein expression, and cellular phenotypes during stepwise reversible EMT. We find that the chromatin insulating protein machinery, including CTCF, is suppressed and re-expressed, coincident with broad alterations in chromatin accessibility, during EMT/MET, and is lower in triple-negative breast cancer cell lines with EMT features. Through an analysis of chromatin accessibility using ATAC-seq, we identify that early phases of EMT are characterized by enrichment for AP-1 family member binding motifs, but also by a diminished enrichment for CTCF binding motifs. Through a loss-of-function analysis, we demonstrate that the suppression of CTCF alters cellular plasticity, strengthening the epithelial phenotype via the upregulation of epithelial markers E-cadherin/CDH1 and downregulation of N-cadherin/CDH2. Conversely, the upregulation of CTCF leads to the upregulation of EMT gene expression and an increase in mesenchymal traits. These findings are indicative of a role of CTCF in regulating epithelial-mesenchymal plasticity and gene expression.

Epithelial-Mesenchymal Transition Signaling and Prostate Cancer Stem Cells: Emerging Biomarkers and Opportunities for Precision Therapeutics

Prostate cancers may reactivate a latent embryonic program called the epithelial-mesenchymal transition (EMT) during the development of metastatic disease. Through EMT, tumors can develop a mesenchymal phenotype similar to cancer stem cell traits that contributes to metastasis and variation in therapeutic responses. Some of the recurrent somatic mutations of prostate cancer affect EMT driver genes and effector transcription factors that induce the chromatin- and androgen-dependent epigenetic alterations that characterize castrate-resistant prostate cancer (CRPC). EMT regulators in prostate cancer comprise transcription factors (SNAI1/2, ZEB1, TWIST1, and ETS), tumor suppressor genes (RB1, PTEN, and TP53), and post-transcriptional regulators (miRNAs) that under the selective pressures of antiandrogen therapy can develop an androgen-independent metastatic phenotype. In prostate cancer mouse models of EMT, Slug expression, as well as WNT/β-Catenin and notch signaling pathways, have been shown to increase stemness potential. Recent single-cell transcriptomic studies also suggest that the stemness phenotype of advanced prostate cancer may be related to EMT. Other evidence correlates EMT and stemness with immune evasion, for example, activation of the polycomb repressor complex I, promoting EMT and stemness and cytokine secretion through RB1, TP53, and PRC1. These findings are helping clinical trials in CRPC that seek to understand how drugs and biomarkers related to the acquisition of EMT can improve drug response.

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

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

Zeb1 and SK3 Channel Are Up-Regulated in Castration-Resistant Prostate Cancer and Promote Neuroendocrine Differentiation

Simple Summary

Currently, neuroendocrine prostate cancers remain fatal, so it is crucial to better understand mechanisms of resistance to hormone therapy driving this phenotype. We have shown that Enza, a new generation hormone therapy, promotes prostate cancer cells neurodifferentiation by activating a positive feedback loop between the key transcription factor of epithelial to mesenchymal transition Zeb1 and the calcium-sensitive potassium channel SK3. These two actors are overexpressed in patients with neuroendocrine castration-resistant prostate cancer. Targeting SK3 channel by Ohmline, a synthetic ether lipid, inhibits neuroendocrine differentiation of prostate cancer cells, which opens new therapeutic prospects for neuroendocrine prostate cancers.

Abstract

Therapeutic strategies for metastatic castration-resistant prostate cancer aim to target androgen receptor signaling. Despite initial survival benefits, treatment resistance invariably occurs, leading to lethal disease. Therapies targeting the androgen receptor can induce the emergence of a neuroendocrine phenotype and reactivate embryonic programs associated with epithelial to mesenchymal transition. We recently reported that dysregulation of the calcium signal can induce the transcription factor Zeb1, a key determinant of cell plasticity during tumor progression. The aim of this study was to determine whether the androgen receptor-targeted treatment Enzalutamide could induce dysregulation of the calcium signal involved in the progression toward epithelial to mesenchymal transition and neuroendocrine differentiation, contributing to therapeutic escape. Our results show that Zeb1 and the SK3 potassium channel are overexpressed in vivo in neuroendocrine castration-resistant prostate cancer and in vitro in LNCaP cells neurodifferentiated after Enzalutamide treatment. Moreover, the neuroendocrine phenotype is associated with a deregulation of the expression of Orai calcium channels. We showed that Zeb1 and SK3 are critical drivers of neuroendocrine differentiation. Interestingly, Ohmline, an SK3 inhibitor, can prevent the expression of Zeb1 and neuroendocrine markers induced by Enzalutamide. This study offers new perspectives to increase hormone therapy efficacy and improve clinical outcomes.

Increased Extracellular Adenosine in Radiotherapy-Resistant Breast Cancer Cells Enhances Tumor Progression through A2AR-Akt-β-Catenin Signaling

Simple Summary

In our previous study, purinergic P2Y₂ receptor (P2Y₂R) activation by ATP was found to play an important role in tumor progression and metastasis by regulating various responses in cancer cells and modulating crosstalk between cancer cells and endothelial cells (ECs). Therefore, we expected that P2Y₂R would play a critical role in radioresistance and enhanced tumor progression in radioresistant triple-negative breast cancer (RT-R-TNBC). However, interestingly, P2Y₂R expression was slightly decreased in RT-R-TNBC cells, while the expression of A2AR was significantly increased both in RT-R-TNBC cells and in tumor tissues, especially triple negative breast cancer (TNBC) tissues of breast cancer (BC) patients. Thus, we aimed to investigate the role of adenosine A2A receptor (A2AR) and its signaling pathway in the progression of RT-R-TNBC. The results reveal for the first time the role of A2AR in the progression and metastasis of RT-R-BC cells and suggest that the adenosine (ADO)-activated intracellular A2AR signaling pathway is linked to the AKT-β-catenin pathway to regulate RT-R-BC cell invasiveness and metastasis.

Abstract

Recently, we found that the expressions of adenosine (ADO) receptors A2AR and A2BR and the ectonucleotidase CD73 which is needed for the conversion of adenosine triphosphate (ATP) to adenosine diphosphate (ADP) and the extracellular ADO level are increased in TNBC MDA-MB-231 cells and RT-R-MDA-MB-231 cells compared to normal cells or non-TNBC cells. The expression of A2AR, but not A2BR, is significantly upregulated in breast cancer tissues, especially TNBC tissues, compared to normal epithelial tissues. Therefore, we further investigated the role of ADO-activated A2AR and its signaling pathway in the progression of RT-R-TNBC. ADO treatment induced MDA-MB-231 cell proliferation, colony formation, and invasion, which were enhanced in RT-R-MDA-MB-231 cells in an A2AR-dependent manner. A2AR activation by ADO induced AKT phosphorylation and then β-catenin, Snail, and vimentin expression, and these effects were abolished by A2AR-siRNA transfection. In an in vivo animal study, compared to 4T1-injected mice, RT-R-4T1-injected mice exhibited significantly increased tumor growth and lung metastasis, which were decreased by A2AR-knockdown. The upregulation of phospho-AKT, β-catenin, Snail, and vimentin expression in mice injected with RT-R-4T1 cells was also attenuated in mice injected with RT-R-4T1-A2AR-shRNA cells. These results suggest that A2AR is significantly upregulated in BC tissues, especially TNBC tissues, and ADO-mediated A2AR activation is involved in RT-R-TNBC invasion and metastasis through the AKT-β-catenin pathway.

Inhibition of Delta-like Ligand 4 enhances the radiosensitivity and inhibits migration in cervical cancer via the reversion of epithelial-mesenchymal transition

Background

Concurrent chemoradiotherapy is the common first-line treatment for patients with advanced cervical cancer. However, radioresistance remains a major clinical challenge, which results in recurrence and poor survival. Many studies have shown the potential of Delta-like Ligand 4 (DLL4) as a novel prognostic biomarker and therapeutic target in many solid tumors. Previously, we have found that high DLL4 expression in tumor cells may predict the pelvic lymph node metastasis and poor prognosis in patients with cervical cancer. In our present study, we further studied the effects of DLL4 on the biological behavior and radiosensitivity of cervical cancer cells.

Methods

The expression of DLL4 and epithelial–mesenchymal transition (EMT) phenotype markers in cervical cancer cell lines or tissues were detected using Western blotting, and the expression of DLL4 mRNA in cervical cancer cell lines or tissues was detected using Quantitative real-time PCR. The effect of DLL4 on cell proliferation, migration, and radiosensitivity was evaluated using the CCK8 assay, flow cytometry, Transwell assays for cell invasion and migration, and Immunofluorescence staining in vitro.

Results

The expression of DLL4 in radiotherapy-resistant SiHa cells was significantly higher than that in radiotherapy-sensitive Me-180 cells. Furthermore, downregulation of DLL4 enhanced the radiosensitivity of SiHa and Caski cells via the inhibition of cell proliferation, promotion of radiation-induced apoptosis, and inhibition of the DNA damage repair. Moreover, downregulation of DLL4 inhibited the EMT and reduced the proliferation, invasion, and migration ability in SiHa and Caski cells. Consistent with the DLL4 expression in the cell lines, the expression of DLL4 in the tissues of the radioresistant group was also higher than that of the radiosensitive group.

Conclusions

Downregulation of DLL4 inhibited the progression and increased the radiosensitivity in cervical cancer cells by reversing EMT. These results indicated the promising prospect of DLL4 against the radioresistance and metastasis of cervical cancer and its potential as a predictive biomarker for radiosensitivity and prognosis in patients with cervical cancer patients receiving concurrent chemoradiotherapy (cCRT).

Suppression of LINC00460 mediated the sensitization of HCT116 cells to ionizing radiation by inhibiting epithelial-mesenchymal transition

Radiation resistance is the most common challenge for improving radiotherapy. The mechanisms underlying the development of radioresistance remain poorly understood. This study aims to explore the role of LINC00460 in ionizing radiation-induced radioresistance as well as the mechanisms by which LINC00460 is regulated by radiation exposure. The expression of LINC00460 was measured. Cell proliferation and colony formation were measured in HCT116 cells after treatment by radiation. The development of epithelial-mesenchymal transition (EMT) was determined with or without knockdown LINC00460 expression using western blot analysis. Transcription activity was determined using a series of LINC00460-promoter luciferase reporter gene vectors. LINC00460 expression was significantly higher in HCT116 cells, relative to other cell types, with LINC00460 expression significantly affecting HCT116 cell proliferation. Suppression of LINC00460 inhibits EMT development in HCT116 cells via regulation of ZEB1 expression. Furthermore, LINC00460 expression was induced by irradiation via the activation of c-jun transcription factor-binding element located on the LINC00460 promoter. LINC00460 was shown to play a crucial role in EMT-associated progression of colorectal cancer, indicating that LINC00460 may be an indicator or new potential therapeutic target for colorectal cancer radiosensitization.

Outcomes of Radiotherapy for Mesenchymal and Non-Mesenchymal Subtypes of Gastric Cancer

Background: The purpose of this study was to evaluate the clinical outcomes following postoperative chemotherapy (XP) versus chemoradiotherapy (XP-RT) according to mesenchymal subtype based on RNA sequencing in gastric cancer (GC) in a cohort of the Adjuvant chemoRadioTherapy In Stomach Tumor (ARTIST) trial. Methods: Of the 458 patients enrolled in the ARTIST trial, formalin-fixed, paraffin-embedded (FFPE) specimens were available from 106 (23.1%) patients for RNA analysis. The mesenchymal subtype was classified according to a previously reported 71-gene MSS/EMT signature using the NanoString assay. Results: Of the 106 patients analyzed (50 in XP arm, 56 in XP-RT arm), 36 (34.0%) patients were categorized as mesenchymal subtype by NanoString assay. Recurrence-free survival (RFS, p = 0.009, hazard ratio (HR) = 2.11, 95% confidence interval (CI): 1.21-3.70) and overall survival (OS, p = 0.003, HR = 2.28, 95% CI: 1.31-3.96) were significantly lower in the mesenchymal subtype than in the non-mesenchymal subtype. In terms of post-operative radiotherapy (RT), mesenchymal subtype was not an independent variable to predict RFS or OS regardless to the assigned arm (XP with or without RT) in this patient cohort. However, there was a trend in the adjuvant XP arm, which showed higher OS than the XP-RT arm for the mesenchymal subtype and lower OS than the XP-RT arm for the non-mesenchymal subtype. Conclusions: We could not determine any significant differences between the mesenchymal and non-mesenchymal subtypes with respect to the effects of adjuvant XP with or without RT in gastric cancer following curative surgery.

Sulfiredoxin as a Potential Therapeutic Target for Advanced and Metastatic Prostate Cancer

The incidence of prostate cancer (PCa) is increasing, and it is currently the second most frequent cause of death by cancer in men. Despite advancements in cancer therapies, new therapeutic approaches are still needed for treatment-refractory advanced metastatic PCa. Cross-species analysis presents a robust strategy for the discovery of new potential therapeutic targets. This strategy involves the integration of genomic data from genetically engineered mouse models (GEMMs) and human PCa datasets. Considering the role of antioxidant pathways in tumor initiation and progression, we searched oxidative stress-related genes for a potential therapeutic target for PCa. First, we analyzed RNA-sequencing data from Pb-Cre4; Pten^f/f mice and discovered an increase in sulfiredoxin (Srxn1) mRNA expression in high-grade prostatic intraepithelial neoplasia (PIN), well-differentiated adenocarcinoma (medium-stage tumors), and poor-differentiated adenocarcinoma (advanced-stage prostate tumors). The increase of SRXN1 protein expression was confirmed by immunohistochemistry in mouse prostate tumor paraffin samples. Analyses of human databases and prostate tissue microarrays demonstrated that SRXN1 is overexpressed in a subset of high-grade prostate tumors and correlates with aggressive PCa with worse prognosis and decreased survival. Analyses in vitro showed that SRXN1 expression is also higher in most PCa cell lines compared to normal cell lines. Furthermore, siRNA-mediated downregulation of SRXN1 led to decreased viability of PCa cells LNCaP. In conclusion, we identified the antioxidant enzyme SRXN1 as a potential therapeutic target for PCa. Our results suggest that the use of specific SRXN1 inhibitors may be an effective strategy for the adjuvant treatment of castration-resistant PCa with SRXN1 overexpression.

Controversies around epithelial-mesenchymal plasticity in cancer metastasis

Experimental evidence accumulated over decades has implicated epithelial-mesenchymal plasticity (EMP), which collectively encompasses epithelial-mesenchymal transition and the reverse process of mesenchymal-epithelial transition, in tumour metastasis, cancer stem cell generation and maintenance, and therapeutic resistance. However, the dynamic nature of EMP processes, the apparent need to reverse mesenchymal changes for the development of macrometastases and the likelihood that only minor cancer cell subpopulations exhibit EMP at any one time have made such evidence difficult to accrue in the clinical setting. In this Perspectives article, we outline the existing preclinical and clinical evidence for EMP and reflect on recent controversies, including the failure of initial lineage-tracing experiments to confirm a major role for EMP in dissemination, and discuss accumulating data suggesting that epithelial features and/or a hybrid epithelial-mesenchymal phenotype are important in metastasis. We also highlight strategies to address the complexities of therapeutically targeting the EMP process that give consideration to its spatially and temporally divergent roles in metastasis, with the view that this will yield a potent and broad class of therapeutic agents.

Multiplex profiling identifies clinically relevant signalling proteins in an isogenic prostate cancer model of radioresistance

The exact biological mechanism governing the radioresistant phenotype of prostate tumours at a high risk of recurrence despite the delivery of advanced radiotherapy protocols remains unclear. This study analysed the protein expression profiles of a previously generated isogenic 22Rv1 prostate cancer model of radioresistance using DigiWest multiplex protein profiling for a selection of 90 signalling proteins. Comparative analysis of the profiles identified a substantial change in the expression of 43 proteins. Differential PARP-1, AR, p53, Notch-3 and YB-1 protein levels were independently validated using Western Blotting. Pharmacological targeting of these proteins was associated with a mild but significant radiosensitisation effect at 4Gy. This study supports the clinical relevance of isogenic in vitro models of radioresistance and clarifies the molecular radiation response of prostate cancer cells.

Contribution of Epithelial Plasticity to Therapy Resistance

Therapy resistance is responsible for tumour recurrence and represents one of the major challenges in present oncology. Significant advances have been made in the understanding of the mechanisms underlying resistance to conventional and targeted therapies improving the clinical management of relapsed patients. Unfortunately, in too many cases, resistance reappears leading to a fatal outcome. The recent introduction of immunotherapy regimes has provided an unprecedented success in the treatment of specific cancer types; however, a good percentage of patients do not respond to immune-based treatments or ultimately become resistant. Cellular plasticity, cancer cell stemness and tumour heterogeneity have emerged as important determinants of treatment resistance. Epithelial-to-mesenchymal transition (EMT) is associated with resistance in many different cellular and preclinical models, although little evidence derives directly from clinical samples. The recognition of the presence in tumours of intermediate hybrid epithelial/mesenchymal states as the most likely manifestation of epithelial plasticity and their potential link to stemness and tumour heterogeneity, provide new clues to understanding resistance and could be exploited in the search for anti-resistance strategies. Here, recent evidence linking EMT/epithelial plasticity to resistance against conventional, targeted and immune therapy are summarized. In addition, future perspectives for related clinical approaches are also discussed.

Functional Organotypic Cultures of Prostate Tissues: A Relevant Preclinical Model that Preserves Hypoxia Sensitivity and Calcium Signaling

In prostate cancer research, there is a lack of valuable preclinical models. Tumor cell heterogeneity and sensitivity to microenvironment signals, such as hypoxia or extracellular calcium concentration, are difficult to reproduce. Here, we developed and characterized an ex vivo tissue culture model preserving these properties. Prostate tissue slices from 26 patients were maintained ex vivo under optimized culture conditions. The expression of markers associated with proliferation, androgen-receptor signaling, and hypoxia was assessed by immunostaining. A macroscope was used to achieve real-time calcium fluorescence optical imaging. Tissue morphology was maintained successfully without necrosis for 5 days. Compared with native tumors and tissue cultured with androgens, androgen deprivation in the medium led to decreased expression of both androgen receptor and its target gene products, prostate specific antigen (PSA) and ETS-related gene (ERG). Ex vivo cultured slices also were sensitive to hypoxia because carbonic anhydrase IX and zinc finger E-box binding homeobox 1 (Zeb1) protein levels increased in 1% oxygen. Exposure of slices to supraphysiological extracellular Ca²⁺ concentration induced a robust and rapid Ca²⁺ entry, with a greater response in tumor compared with nontumor tissue. This ex vivo model reproduces the morphologic and functional characteristics of human prostate cancer, including sensitivity to androgen deprivation and induced response to hypoxia and extracellular Ca²⁺. It therefore could become an attractive tool for drug response prediction studies.

EMT Markers in Locally-Advanced Prostate Cancer: Predicting Recurrence?

Background: Prostate cancer (PCa) is the second most frequent cause of cancer-related death in men worldwide. It is a heterogeneous disease at molecular and clinical levels which makes its prognosis and treatment outcome hard to predict. The epithelial-to-mesenchymal transition (EMT) marks a key step in the invasion and malignant progression of PCa. We sought to assess the co-expression of epithelial cytokeratin 8 (CK8) and mesenchymal vimentin (Vim) in locally-advanced PCa as indicators of EMT and consequently predictors of the progression status of the disease. Methods: Co-expression of CK8 and Vim was evaluated by immunofluorescence (IF) on paraffin-embedded tissue sections of 122 patients with PCa who underwent radical prostatectomies between 1998 and 2016 at the American University of Beirut Medical Center (AUBMC). EMT score was calculated accordingly and then correlated with the patients' clinicopathological parameters and PSA failure. Results: The co-expression of CK8/Vim (EMT score), was associated with increasing Gleason group. A highly significant linear association was detected wherein higher Gleason group was associated with higher mean EMT score. In addition, the median estimated biochemical recurrence-free survival for patients with < 25% EMT score was almost double that of patients with more than 25%. The validity of this score for prediction of prognosis was further demonstrated using cox regression model. Our data also confirmed that the EMT score can predict PSA failure irrespective of Gleason group, pathological stage, or surgical margins. Conclusion: This study suggests that assessment of molecular markers of EMT, particularly CK8 and Vim, in radical prostatectomy specimens, in addition to conventional clinicopathological prognostic parameters, can aid in the development of a novel system for predicting the prognosis of locally-advanced PCa.

miR-205 enhances radiation sensitivity of prostate cancer cells by impairing DNA damage repair through PKCε and ZEB1 inhibition

BACKGROUND

Radiotherapy is one of the main treatment options for non-metastatic prostate cancer (PCa). Although treatment technical optimization has greatly improved local tumor control, a considerable fraction of patients still experience relapse due to the development of resistance. Radioresistance is a complex and still poorly understood phenomenon involving the deregulation of a variety of signaling pathways as a consequence of several genetic and epigenetic abnormalities. In this context, cumulative evidence supports a functional role of microRNAs in affecting radioresistance, suggesting the modulation of their expression as a novel radiosensitizing approach. Here, we investigated for the first time the ability of miR-205 to enhance the radiation response of PCa models.

METHODS

miR-205 reconstitution by a miRNA mimic in PCa cell lines (DU145 and PC-3) was used to elucidate miR-205 biological role. Radiation response in miRNA-reconstituted and control cells was assessed by clonogenic assay, immunofluorescence-based detection of nuclear γ-H2AX foci and comet assay. RNAi was used to silence the miRNA targets PKCε or ZEB1. In addition, target-protection experiments were carried out using a custom oligonucleotide designed to physically disrupt the pairing between the miR-205 and PKCε. For in vivo experiments, xenografts generated in SCID mice by implanting DU145 cells stably expressing miR-205 were exposed to 5-Gy single dose irradiation using an image-guided animal micro-irradiator.

RESULTS

miR-205 reconstitution was able to significantly enhance the radiation response of prostate cancer cell lines and xenografts through the impairment of radiation-induced DNA damage repair, as a consequence of PKCε and ZEB1 inhibition. Indeed, phenocopy experiments based on knock-down of either PKCε or ZEB1 reproduced miR-205 radiosensitizing effect, hence confirming a functional role of both targets in the process. At the molecular level, miR-205-induced suppression of PKCε counteracted radioresistance through the impairment of EGFR nuclear translocation and the consequent DNA-PK activation. Consistently, disruption of miR-205-PKCε 3'UTR pairing almost completely abrogated the radiosensitizing effect.

CONCLUSIONS

Our results uncovered the molecular and cellular mechanisms underlying the radiosensitizing effect of miR-205. These findings support the clinical interest in developing a novel therapeutic approach based on miR-205 reconstitution to increase PCa response to radiotherapy.

Inhibition of LOXL2 Enhances the Radiosensitivity of Castration-Resistant Prostate Cancer Cells Associated with the Reversal of the EMT Process

INTRODUCTION

Radiotherapy is the mainstay in the treatment of prostate cancer. However, significant radioresistance of castration-resistant prostate cancer (CRPC) cells constitutes a main obstacle in the treatment of this disease. By using bioinformatic data mining methods, LOXL2 was found to be upregulated in both androgen-independent prostate cancer cell lines and radioresistant tumor samples collected from patients with prostate cancer. We speculate that LOXL2 may play an important role in the radioresistance of CRPC cells.

METHODS

The effect of LOXL2 knockdown on the radiosensitivity of androgen-independent prostate cancer cells lines was measured by the clonogenic assay and xenograft tumor experiments under in vitro and in vivo conditions, respectively. In studies on the mechanism, we focused on the EMT phenotype changes and cell apoptosis changes induced by LOXL2 knockdown in DU145 cells. The protein levels of three EMT biomarkers, namely, E-cadherin, vimentin, and N-cadherin, were measured by western blotting and immunohistochemical staining. Cell apoptosis after irradiation was measured by flow cytometry and caspase-3 activity assay. Salvage experiment was also conducted to confirm the possible role of EMT in the radiosensitization effect of LOXL2 knockdown in CRPC cells.

RESULTS

LOXL2 knockdown in CRPC cells enhanced cellular radiosensitivity under both in vitro and in vivo conditions. A significant reversal of EMT was observed in LOXL2-silenced DU145 cells. Cell apoptosis after irradiation was significantly enhanced by LOXL2 knockdown in DU145 cells. Results from the salvage experiment confirmed the key role of EMT process reversal in the radiosensitization effect of LOXL2 knockdown in DU145 cells.

CONCLUSIONS

LOXL2 plays an important role in the development of cellular radioresistance in CRPC cells. Targeting LOXL2 may be a rational avenue to overcome radioresistance in CRPC cells. A LOXL2-targeting strategy for CRPC treatment warrants detailed investigation in the future.

Technical Feasibility of Tissue Microarray (TMA) Analysis of Tumor-Associated Immune Response in Prostate Cancer

Introduction: The androgen receptor (AR) regulates immune-related epithelial-to-mesenchymal transition (EMT), and prostate cancer (PCa) metastasis. Primary tumor-infiltrating lymphocytes (TILs) [CD3⁺, CD4⁺, and CD8⁺ TILs] are potential prognostic indicators in PCa, and variations may contribute to racial disparities in tumor biology and PCa outcomes.

Aim: To assess the technical feasibility of tumor microarray (TMA)-based methods to perform multi-marker TIL profiling in primary resected PCa.

Methods: Paraffin-embedded tissue cores of histopathologically-confirmed primary PCa (n = 40; 1 TMA tissue specimen loss) were arrayed in triplicate on TMAs. Expression profiles of AR, CD3⁺, CD4⁺, and CD8⁺ TILs in normal prostate, and the center and periphery of both the tumor-dominant nodule and highest Gleason grade were detected by IHC and associated with clinical and pathological data using standard statistical methodology. An independent pathologist, blinded to the clinical data, scored all samples (percent and intensity of positive cells).

Results: TMAs were constructed from 21 (53.8%) Black and 18 (46.2%) White males with completely-resected, primarily pT2 stage PCa [pT2a (n = 3; 7.7%); pT2b (n = 2; 5.1%); pT2c (n = 27; 69.2%); pT3a (n = 5; 12.8%); mean pre-op PSA = 8.17 ng/ml]. The CD3, CD4, CD8, and CD8/CD3 cellular protein expression differed from normal in the periphery of the dominant nodule, the center of the highest Gleason grade, and the periphery of the highest Gleason grade (P < 0.05). Correlations between TIL expression in the center and periphery of the dominant nodule, with corresponding center and periphery of the highest Gleason grade, respectively, were robust, and the magnitude of these correlations differed markedly by race (P < 0.05).

Conclusions: Multi-marker (AR, CD3, CD4, CD8) profiling with IHC analysis of TMAs consisting of primary, non-metastatic resected prostate cancer is technically feasible in this pilot study. Future studies will evaluate primary tumor immunoscore using semi-quantitative, IHC-based methodology to assess differences in the spectrum, quantity, and/or localization of TILs, and to gain insights into racial disparities in PCa tumor biology and clinical outcomes.

Clair DK, Kyprianou N. Profiles of Radioresistance Mechanisms in Prostate Cancer

Radiation therapy (RT) is commonly used for the treatment of localized prostate cancer (PCa). However, cancer cells often develop resistance to radiation through unknown mechanisms and pose an intractable challenge. Radiation resistance is highly unpredictable, rendering the treatment less effective in many patients and frequently causing metastasis and cancer recurrence. Understanding the molecular events that cause radioresistance in PCa will enable us to develop adjuvant treatments for enhancing the efficacy of RT. Radioresistant PCa depends on the elevated DNA repair system and the intracellular levels of reactive oxygen species (ROS) to proliferate, self-renew, and scavenge anti-cancer regimens, whereas the elevated heat shock protein 90 (HSP90) and the epithelial-mesenchymal transition (EMT) enable radioresistant PCa cells to metastasize after exposure to radiation. The up-regulation of the DNA repairing system, ROS, HSP90, and EMT effectors has been studied extensively, but not targeted by adjuvant therapy of radioresistant PCa. Here, we emphasize the effects of ionizing radiation and the mechanisms driving the emergence of radioresistant PCa. We also address the markers of radioresistance, the gene signatures for the predictive response to radiotherapy, and novel therapeutic platforms for targeting radioresistant PCa. This review provides significant insights into enhancing the current knowledge and the understanding toward optimization of these markers for the treatment of radioresistant PCa.