Radiosensitizes Prostate Cancer Research Articles

Epigenetic regulation of TP53 is involved in prostate cancer radioresistance and DNA damage response signaling

External beam radiotherapy (RT) is a leading first-line therapy for prostate cancer (PCa), and, in recent years, significant advances have been accomplished. However, RT resistance can arise and result in long-term recurrence or disease progression in the worst-case scenario. Thus, making crucial the discovery of new targets for PCa radiosensitization. Herein, we generated a radioresistant PCa cell line, and found p53 to be highly expressed in radioresistant PCa cells, as well as in PCa patients with recurrent/disease progression submitted to RT. Mechanism dissection revealed that RT could promote p53 expression via epigenetic modulation. Specifically, a decrease of H3K27me3 occupancy at TP53 gene promoter, due to increased KDM6B activity, was observed in radioresistant PCa cells. Furthermore, p53 is essential for efficient DNA damage signaling response and cell recovery upon stress induction by prolonged fractionated irradiation. Remarkably, KDM6B inhibition by GSK-J4 significantly decreased p53 expression, consequently attenuating the radioresistant phenotype of PCa cells and hampering in vivo 3D tumor formation. Overall, this work contributes to improve the understanding of p53 as a mediator of signaling transduction in DNA damage repair, as well as the impact of epigenetic targeting for PCa radiosensitization.

Dual enhancement in the radiosensitivity of prostate cancer through nanoparticles and chemotherapeutics

BackgroundRadiotherapy (RT) is an essential component in the treatment regimens for many cancer patients. However, the dose escalation required to improve curative results is hindered due to the normal tissue toxicity that is induced. The introduction of radiosensitizers to RT treatment is an avenue that is currently being explored to overcome this issue. By introducing radiosensitizers into tumor sites, it is possible to preferentially enhance the local dose deposited. Gold nanoparticles (GNPs) are a potential candidate that have shown great promise in increasing the radiosensitivity of cancer cells through an enhancement in DNA damage. Furthermore, docetaxel (DTX) is a chemotherapeutic agent that arrests cells in the G2/M phase of the cell cycle, the phase most sensitive to radiation damage. We hypothesized that by incorporating DTX to GNP-enhanced radiotherapy treatment, we could further improve the radiosensitization experienced by cancer cells. To assess this strategy, we analyzed the radiotherapeutic effects on monolayer cell cultures in vitro, as well as on a mice prostate xenograft model in vivo while using clinically feasible concentrations for both GNPs and DTX.ResultsThe introduction of DTX to GNP-enhanced radiotherapy further increased the radiotherapeutic effects experienced by cancer cells. A 38% increase in DNA double-strand breaks was observed with the combination of GNP/DTX vs GNP alone after a dose of 2 Gy was administered. In vivo results displayed significant reduction in tumor growth over a 30-day observation period with the treatment of GNP/DTX/RT when compared to GNP/RT after a single 5 Gy dose was given to mice. The treatment strategy also resulted in 100% mice survival, which was not observed for other treatment conditions.ConclusionsIncorporating DTX to work in unison with GNPs and RT can increase the efficacy of RT treatment. Our study suggests that the treatment strategy could improve tumor control through local dose enhancement. As the concentrations used in this study are clinically feasible, there is potential for this strategy to be translated into clinical settings.

CDC20 promotes radioresistance of prostate cancer by activating Twist1 expression.

Currently, radiotherapy is one of the most attractive treatments for prostate cancer (PCa) patients. However, radioresistance remains a challenging issue and the underlying mechanism is unknown. Growing evidence has demonstrated that CDC20 (Cell division cycle protein 20) plays a pivotal role in a variety of tumors, including PCa. Here, GEPIA database mining and western blot analysis showed that higher expression of CDC20 was observed in PCa tissues and cells. We demonstrated that the expression of CDC20 was increased in PCa cells by irradiation, and knockdown of CDC20 resulted in inhibition of cell proliferation, migration, tumor formation, induced cell apoptosis and increased radiosensitivity in PCa in vitro and in vivo. Furthermore, we observed that CDC20 regulated Twist1 pathway, influencing cell proliferation and migration. These results suggest that targeting CDC20 and Twist1 may be an effective way to improve the radiosensitivity of PCa.

Circular RNA LPAR3 targets JPT1 via microRNA-513b-5p to facilitate glycolytic activation but repress prostate cancer radiosensitivity

A great many circular RNAs (circRNAs) are considered key modulators of human malignancies. However, the function of circRNA lysophosphatidic acid receptor 3 (LPAR3) in the radioresistance of prostate cancer (PCa) cells is still uncertain. circLPAR3, microRNA (miR)-329-3p, and JPT1 expression in PCa tissues and cells were detected by real-time quantitative PCR or western blot. Cell proliferation was detected by CCK-8 (cell proliferation assay) and colony formation assay, apoptosis was by flow cytometry, and migration and invasion ability were by Transwell assay. Cell glycolysis was analyzed by glucose uptake, lactate production, and ATP metabolism. Under different doses of radiation, the radiosensitivity of PCa cells was detected by colony formation assay. The relationship between circLPAR3, miR-513b-5p, and JPT1 was confirmed by dual luciferase reporter gene detection and RIP assay. The data presented that circLPAR3 and JPT1 expression was elevated in PCa, while miR-513b-5p expression was reduced. Repression of circLPAR3 depressed cell advancement, and restrained glycolysis, but enhanced the radiosensitivity of PCa cells. CircLPAR3's target miRNA was miR-513b-5p which targeted JPT1. Elevated JPT1 reversed the repressive effects of circLPAR3 knockdown or miR-513b-5p overexpression on PCa advancement, glycolysis, and radiosensitivity. In summary, the knockdown of circLPAR3 reduces glycolysis, but promotes PCa radiosensitivity via the miR-513b-5p/JPT1 axis, discovering a novel mechanism in PCa progression.

Analysis and Validation of Key Genes Related to Radiosensitivity in Prostate Cancer.

To investigate the potential relationship between differential gene expression, biological function enrichment, and disease prognosis affecting the sensitivity of prostate cancer radiotherapy by bioinformatics analysis. Retrieve and obtain data on differential gene expression of prostate cancer radiosensitivity in the GEO database (GSM3954350, GSM3954351, GSM3954352), GER2 tool to screen and analyze the differential genes, Enrichr database for enrichment analysis of GO and KEGG, use Cytoscape software builds protein-protein interaction (PPI) networks and analyzes key genes. A total of 7041 differentially expressed genes were screenedout, including 3842 high expression genes and 3199 low expressed genes. The top 20 differentially expressed genes were selected for further analysis. Their biological functions are mainly enriched in the following aspects: "Cell communication" and "Signal transduction"; cytological components are mainly located outside the cell; molecular functions are enriched in structural molecular activity, receptor binding, serine-like peptidase activity, etc. The KEGG enrichment analysis showed that the differentially expressed genes were mainly enriched in the mismatch repair pathway, non-homologous terminal binding pathway and so on. Survival analysis showed that VGF gene was associated with the prognosis of prostate cancer patients receiving radiotherapy, and high expression of VGF significantly reduced progression-free survival(PFS) in these patients(HR = 4.84, 95% CI: 1.34-17.5, P = .016). This study identified key genes associated with radiation sensitivity in prostate cancer and verified the relationship between the VGF gene and patient prognosis.

Boosted Radiation Bystander Effect of PSMA-Targeted Gold Nanoparticles in Prostate Cancer Radiosensitization.

Metal nanoparticles are effective radiosensitizers that locally enhance radiation doses in targeted cancer cells. Compared with other metal nanoparticles, gold nanoparticles (GNPs) exhibit high biocompatibility, low toxicity, and they increase secondary electron scatter. Herein, we investigated the effects of active-targeting GNPs on the radiation-induced bystander effect (RIBE) in prostate cancer cells. The impact of GNPs on the RIBE presents implications for secondary cancers or spatially fractionated radiotherapy treatments. Anti-prostate-specific membrane antigen (PSMA) antibodies were conjugated with PEGylated GNPs through EDC-NHS chemistry. The media transfer technique was performed to induce the RIBE on the non-irradiated bystander cells. This study focused on the LNCaP cell line, because it can model a wide range of stages relating to prostate cancer progression, including the transition from androgen dependence to castration resistance and bone metastasis. First, LNCaP cells were pretreated with phosphate buffered saline (PBS) or PSMA-targeted GNPs (PGNPs) for 24 h and irradiated with 160 kVp X-rays (0-8 Gy). Following that, the collected culture media were filtered (sterile 0.45 µm polyethersulfone) in order to acquire PBS- and PGNP- conditioned media (CM). Then, PBS- and PGNP-CM were transferred to the bystander cells that were loaded with/without PGNPs. MTT, γ-H2AX, clonogenic assays and reactive oxygen species assessments were performed to compare RIBE responses under different treatments. Compared with 2 Gy-PBS-CM, 8 Gy-PBS-CM demonstrated a much higher RIBE response, thus validating the dose dependence of RIBE in LNCaP cells. Compared with PBS-CM, PGNP-CM exhibited lower cell viability, higher DNA damage, and a smaller survival fraction. In the presence of PBS-CM, bystander cells loaded with PGNPs showed increased cell death compared with cells that did not have PGNPs. These results demonstrate the PGNP-boosted expression and sensitivity of RIBE in prostate cancer cells.

Synergistic Prostate Cancer Targeted Radiosensitization by Gold Nanoparticles and Histone Deacetylase Inhibitor Romidepsin

<h3>Purpose/Objective(s)</h3> Histone deacetylase inhibitors (HDACi), such as Romidepsin (FK228) have been confirmed as effective anticancer agents for liquid cancers, but systemic toxicity hinders their application in solid tumors. Gold nanoparticles (GNPs) with tumor specific ligands can be actively accumulated in the targeted tumor, elevating HDACi delivery efficiency. Moreover, GNPs demonstrate their exceptional competence in improving radiosensitization through locally enhanced radiation scatter in the tumor. In this study, we examined the synergistic consequence of prostate cancer treatment with FK228 conjugated GNPs and investigate the molecular mechanism underlying radiosensitization. <h3>Materials/Methods</h3> GNPs were thiolated with N-succinimidyl 3-(2-pyridyldithio)-propionate (SPDP). FK228 and αPSMA antibody were reduced with tris(2-carboxyethyl)-phosphine and mixed with GNPs at a 10:1 ratio, respectively. Dynamic light scattering (DLS) and enzyme linked immunosorbent assay (ELISA) confirmed conjugation, and targeting efficiency was assessed with immunofluorescence (IF) staining of GNPs. PSMA-targeted GNPs (pGNP), and pGNP+FK228 (pfGNP) were treated to LNCaP cells at varying concentrations and monitored on a real time cell analysis (RTCA) system. Western blot (WB) was performed on HDACi pathways. Finally, 2Gy at 160kVp was delivered to cells. 1hr post irradiation, cells were fixed and stained with γH2AX antibodies. Foci count and size were quantified. <h3>Results</h3> DLS showed shift in GNP hydrodynamic size from 49nm to 52nm when conjugated to αPSMA antibody or antibody and FK228. Zeta potential changed from -8mv to -14mV and -20mV in pGNP and pfGNP, respectively. ELISA revealed successful conjugation of αPSMA antibodies with ∼4 antibodies per GNP. IF demonstrated that pfGNP have three-fold higher accumulation on LNCaP cells compared to untargeted GNPs. Based on RTCA, pGNP showed cell killing starting at 1mg/mL at 24hrs, while pfGNP started cell killing at 10µg/mL, but the initiation ranged from 72hrs to 24hrs in a dose dependent manner. At non-toxic concentrations of FK228 and pfGNP, WB revealed both treatments induced a lower expression of androgen receptor and increased expression of ATF3, while pGNP did not. γH2AX assay revealed an increased formation of foci with the treatment of pGNP (158%), FK228 (125%), and pfGNP (170%). There was no statistically significant increase in the foci count between pGNP and pfGNP. However, measurements of total surface area per foci revealed a statistically significant increase in foci size from FK228 and pfGNP compared to pGNP. <h3>Conclusion</h3> FK228 and PSMA-antibodies were successfully conjugated to GNPs using SPDP chemistry. Furthermore, pfGNP demonstrated increased prostate cancer affinity and induced similar cellular signaling as free FK228. Finally, conjugation of FK228 to GNPs synergistically improved prostate cancer radiosensitization through greater induction of double stranded DNA breaks in vitro.

Quantifying Radiosensitization of PSMA-Targeted Gold Nanoparticles on Prostate Cancer Cells at Megavoltage Radiation Energies by Monte Carlo Simulation and Local Effect Model.

Active targeting gold nanoparticles (AuNPs) are a very promising avenue for cancer treatment with many publications on AuNP mediated radiosensitization at kilovoltage (kV) photon energies. However, uncertainty on the effectiveness of AuNPs under clinically relevant megavoltage (MV) radiation energies hinders the clinical translation of AuNP-assisted radiation therapy (RT) paradigm. The aim of this study was to investigate radiosensitization mediated by PSMA-targeted AuNPs irradiated by a 6 MV radiation beam at different depths to explore feasibility of AuNP-assisted prostate cancer RT under clinically relevant conditions. PSMA-targeted AuNPs (PSMA-AuNPs) were synthesized by conjugating PSMA antibodies onto PEGylated AuNPs through EDC/NHS chemistry. Confocal fluorescence microscopy was used to verify the active targeting of the developed PSMA-AuNPs. Transmission electron microscopy (TEM) was used to demonstrate the intracellular biodistribution of PSMA-AuNPs. LNCaP prostate cancer cells treated with PSMA-AuNPs were irradiated on a Varian 6 MV LINAC under varying depths (2.5 cm, 10 cm, 20 cm, 30 cm) of solid water. Clonogenic assays were carried out to determine the in vitro cell survival fractions. A Monte Carlo (MC) model developed on TOPAS platform was then employed to determine the nano-scale radial dose distribution around AuNPs, which was subsequently used to predict the radiation dose response of LNCaP cells treated with AuNPs. Two different cell models, with AuNPs located within the whole cell or only in the cytoplasm, were used to assess how the intracellular PSMA-AuNP biodistribution impacts the prostate cancer radiosensitization. Then, MC-based microdosimetry was combined with the local effect model (LEM) to calculate cell survival fraction, which was benchmarked against the in vitro clonogenic assays at different depths. In vitro clonogenic assay of LNCaP cells demonstrated the depth dependence of AuNP radiosensitization under clinical megavoltage beams, with sensitization enhancement ratio (SER) of 1.14 ± 0.03 and 1.55 ± 0.05 at 2.5 cm depth and 30 cm depth, respectively. The MC microdosimetry model showed the elevated percent of low-energy photons in the MV beams at greater depth, consequently resulting in increased dose enhancement ratio (DER) of AuNPs with depth. The AuNP-induced DER reached ~5.7 and ~8.1 at depths of 2.5 cm and 30 cm, respectively. Microdosimetry based LEM accurately predicted the cell survival under 6 MV beams at different depths, for the cell model with AuNPs placed only in the cell cytoplasm. TEM results demonstrated the distribution of PSMA-AuNPs in the cytoplasm, confirming the accuracy of MC microdosimetry based LEM with modelled AuNPs distributed within the cytoplasm. We conclude that AuNP radiosensitization can be achieved under megavoltage clinical radiotherapy energies with a dependence on tumor depth. Furthermore, the combination of Monte Carlo microdosimetry and LEM will be a valuable tool to assist with developing AuNP-aided radiotherapy paradigm and drive clinical translation.

Targeting the radiation-induced ARv7-mediated circNHS/miR-512-5p/XRCC5 signaling with Quercetin increases prostate cancer radiosensitivity

BackgroundRadiation therapy (RT) with androgen deprivation therapy (ADT) is an effective therapy to suppress the locally advanced prostate cancer (PCa). However, we unexpectedly found that RT could also induce the androgen receptor splice variant 7 (ARv7) expression to decrease the radiosensitivity.MethodsThe study was designed to target ARv7 expression with Quercetin or ARv7-shRNA that leads to enhancing and increasing the radiation sensitivity to better suppress the PCa that involved the modulation of the circNHS/miR-512-5p/XRCC5 signaling.ResultsMechanism studies revealed that RT-induced ARv7 may function via altering the circNHS/miR-512-5p/XRCC5 signaling to decrease the radiosensitivity. Results from preclinical studies using multiple in vitro cell lines and in vivo mouse models concluded that combining RT with the small molecule of Quercetin to target full-length AR and ARv7 could lead to better efficacy to suppress PCa progression.ConclusionTogether, these results suggest that ARv7 may play key roles to alter the PCa radiosensitivity, and targeting this newly identified ARv7 mediated circNHS/miR-512-5p/XRCC5 signaling with Quercetin may help physicians to develop a novel RT to better suppress the progression of PCa.

Abstract 3050: Equol as a radiosensitizer and therapeutic agent in prostate cancer

Abstract The gastrointestinal microbiome and the metabolites it can produce have been linked to response to various cancer treatments, including in prostate cancer. Equol is a microbial metabolite that is exclusively produced by the conversion of soy isoflavones in the diet by specific intestinal bacteria. Interestingly, equol has previously been shown to exhibit anti-androgen effects on prostate cells and likewise may act as a radiosensitizer. We analyzed the microbial composition of fecal samples collected from men receiving stereotactic ablative radiation (SABR) versus observation to treat oligometastatic prostate cancer as part of the ORIOLE trial and found that patients harboring equol-producing bacteria had a lower risk of disease progression. We therefore aimed to study the effect of this compound on prostate cancer cell lines in vitro. MTT assay was used to assess the effects of equol treatment on cell viability in androgen receptor (AR) positive LNCaP cells and AR null PC3 cells over time. We assessed the ability of equol to reduce AR protein levels and/or subcellular localization in LNCaP cells using immunohistochemistry. Finally, western blotting was used to assess the effects of equol treatment on prostate specific antigen (PSA) levels to assess effects on the AR signaling pathway. Cell viability was significantly decreased over time in equol treated cells, but only in prostate cancer cell lines that were AR positive. The effects of equol on LNCaP viability was abrogated in an AR knockdown LNCaP cell line. Interestingly, AR protein levels were found to be markedly decreased upon equol treatment of LNCaP cells. We likewise observed a decrease in PSA protein levels in AR positive cells after equol treatment. Our results support the notion that equol can inhibit prostate cancer growth by inhibition of the androgen receptor. We are currently investigating whether combining equol exposure with radiation treatment produces a synergistic effect on DNA damage and reduction of prostate cancer cell viability and survival in vitro. Our future studies will investigate the effects of equol and equol-producing bacteria on tumor growth in in vivo models. Citation Format: Carli B. Jones, Jonathan B. Coulter, Janielle P. Maynard, Luke A. Mummert, Ryan M. Phillips, Phuoc T. Tran, Karen S. Sfanos. Equol as a radiosensitizer and therapeutic agent in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3050.

Antagonizing Glutamine Bioavailability Promotes Radiation Sensitivity in Prostate Cancer.

Simple SummaryRadiation is the standard of care for prostate cancer, but almost half the patients develop resistant disease. It is imperative to understand the reasons behind disease progression to develop more effective strategies of treatment. We determined that glutamine is a crucial nutrient in driving prostate cancer tumors as people with more glutamine have poorer outcomes. We hypothesized that directly depriving cancer cells of this precious resource will further sensitize them to radiation. We sought to repurpose the drug L-asparaginase, which has been used extensively to treat leukemia patients, to complement radiation therapy for prostate cancer patients. This drug depletes glutamine in the blood and hinders an aspect of cell growth that makes cancer cells that are otherwise resistant vulnerable to irradiation. Ultimately, mouse models of prostate cancer given L-asparaginase in combination with irradiation were more effective at reducing tumor size than radiation alone.Nearly half of localized prostate cancer (PCa) patients given radiation therapy develop recurrence. Here, we identified glutamine as a key player in mediating the radio-sensitivity of PCa. Glutamine transporters and glutaminase are upregulated by radiation therapy of PCa cells, but respective inhibitors were ineffective in radio-sensitization. However, targeting glutamine bioavailability by L-asparaginase (L-ASP) led to a significant reduction in clonogenicity when combined with irradiation. L-ASP reduced extracellular asparagine and glutamine, but the sensitization effects were driven through its depletion of glutamine. L-ASP led to G2/M cell cycle checkpoint blockade. As evidence, there was a respective delay in DNA repair associated with RAD51 downregulation and upregulation of CHOP, contributing to radiation-induced cell death. A radio-resistant PCa cell line was developed, was found to bypass radiation-induced mitotic catastrophe, and was sensitive to L-ASP/radiation combination treatment. Previously, PCa-associated fibroblasts were reported as a glutamine source supporting tumor progression. As such, glutamine-free media were not effective in promoting radiation-induced PCa cell death when co-cultured with associated primary fibroblasts. However, the administration L-ASP catalyzed glutamine depletion with irradiated co-cultures and catalyzed tumor volume reduction in a mouse model. The clinical history of L-ASP for leukemia patients supports the viability for its repurposing as a radio-sensitizer for PCa patients.

Plasticity within Aldehyde Dehydrogenase-Positive Cells Determines Prostate Cancer Radiosensitivity.

The increase of ALDH+ cells with stem-like features in prostate xenograft tumors after local irradiation represents a putative cellular escape mechanism inducing tumor radioresistance.

MiR-223-3p targets FOXO3a to inhibit radiosensitivity in prostate cancer by activating glycolysis

AimsThe incidence and detection rate of prostate cancer in China have been increasing in recent years. Radiotherapy is the ideal treatment for non-metastatic prostate cancer (PCa), but the effectiveness of radiotherapy is greatly discounted due to radio resistance. Therefore, relieving the radiotherapy resistance of PCa is key to improve the clinical efficacy of PCA. Main methodsCell proliferation was estimated using the MTT and clone formation assays. Cell apoptosis was estimated using the Annexin V-FITC/propidium iodide (PI) staining assay. Glucose uptake and lactose and ATP production were used to detect glycolysis. Key findingsmiR-223-3p was significantly upregulated in clinically collected urine samples and PCa cells with low radiosensitivity. Enhancing miR-223-3p reduced radiosensitivity further, while inhibiting miR-223-3p improved the radiosensitivity of PC3 and LNCaP cells. Importantly, miR-223-3p regulated radiosensitivity by enhancing cell glycolysis. FOXO3a was a key target of miRNA-223-3p regulating glycolysis and radiosensitivity. Overexpression of FOXO3a abated the glycolysis level and alleviated the radioresistance caused by enhancing miR-223-3p to a certain extent. SignificanceThis is novel research on the role of miR-223-3p in promoting radiotherapy resistance of PCa cells by activating glycolysis. This approach provides a new perspective and ideas for alleviating radiotherapy resistance of PCa cells.

MSOR04 Presentation Time: 10:20 AM: Experimental Research on CD40/PI3K/AKT Signal Pathway Axis Regulated by MiR-503 and Its Biological Effects for Brachytherapy in Prostate Cancer

Purpose: Brachytherapy plays an important role in the radical treatment of prostate cancer, and its related biological effects and possible mechanisms have yet to be demonstrated. Based on the previous radiobiological study of tumor brachytherapy, this research intends to analyze the relationship between the radiosensitivity of prostate cancer and miR-503-CD40-PI3K/AKT signaling system, reveal the potential targets for improving brachytherapy sensitivity of prostate cancer.

MiR-541-3p enhances the radiosensitivity of prostate cancer cells by inhibiting HSP27 expression and downregulating \u03b2-catenin

Heat shock protein 27 (HSP27), a regulator of cell survival, can enhance the resistance of cancer cells to radiotherapy. As microRNA-541-3p (miR-541-3p) was recently predicted to be a putative upstream modulator of HSP27, the present study was designed to investigate the function and mechanism underlying how miR-541-3p modulates the radiosensitivity of prostate cancer (PCa) cells by regulating HSP27. Through quantitative PCR, miR-541-3p was determined to be poorly expressed in PCa tissues relative to normal controls, whereas its expression was enhanced after radiotherapy. Consistently, miR-541-3p expression levels in PCa cells were elevated after radiation. Cell viability and proliferation and apoptosis under radiation were subsequently evaluated in response to loss-of-function of miR-541-3p. It was found that inhibition of miR-541-3p facilitated the viability and proliferation of PCa cells and promoted their apoptosis post radiation, hence reducing the radiosensitivity of LNCaP cells. Dual-luciferase reporter assay identified that miR-541-3p negatively regulated the HSP27 mRNA expression by targeting its 3′-UTR. Meanwhile, miR-541-3p overexpression inhibited the β-catenin expression by targeting HSP27. Furthermore, HSP27 or β-catenin overexpression was noted to significantly reverse the miR-541-3p-mediated changes in the biological functions of PCa cells post radiation, suggesting that HSP27-dependent activation of β-catenin might be the mechanism responsible for the promotive effect of miR-541-3p on radiosensitivity. Collectively, this study suggests that miR-541-3p specifically inhibits the HSP27 expression and downregulates β-catenin, thereby enhancing the radiosensitivity of PCa cells. Our findings highlight the underlying mechanism of the miR-541-3p/HSP27/Wnt/β-catenin axis regarding radiotherapy for PCa.

GLS-driven glutamine catabolism contributes to prostate cancer radiosensitivity by regulating the redox state, stemness and ATG5-mediated autophagy.

Radiotherapy is one of the curative treatment options for localized prostate cancer (PCa). The curative potential of radiotherapy is mediated by irradiation-induced oxidative stress and DNA damage in tumor cells. However, PCa radiocurability can be impeded by tumor resistance mechanisms and normal tissue toxicity. Metabolic reprogramming is one of the major hallmarks of tumor progression and therapy resistance. Specific metabolic features of PCa might serve as therapeutic targets for tumor radiosensitization and as biomarkers for identifying the patients most likely to respond to radiotherapy. The study aimed to characterize a potential role of glutaminase (GLS)-driven glutamine catabolism as a prognostic biomarker and a therapeutic target for PCa radiosensitization.Methods: We analyzed primary cell cultures and radioresistant (RR) derivatives of the conventional PCa cell lines by gene expression and metabolic assays to identify the molecular traits associated with radiation resistance. Relative radiosensitivity of the cell lines and primary cell cultures were analyzed by 2-D and 3-D clonogenic analyses. Targeting of glutamine (Gln) metabolism was achieved by Gln starvation, gene knockdown, and chemical inhibition. Activation of the DNA damage response (DDR) and autophagy was assessed by gene expression, western blotting, and fluorescence microscopy. Reactive oxygen species (ROS) and the ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG) were analyzed by fluorescence and luminescence probes, respectively. Cancer stem cell (CSC) properties were investigated by sphere-forming assay, CSC marker analysis, and in vivo limiting dilution assays. Single circulating tumor cells (CTCs) isolated from the blood of PCa patients were analyzed by array comparative genome hybridization. Expression levels of the GLS1 and MYC gene in tumor tissues and amino acid concentrations in blood plasma were correlated to a progression-free survival in PCa patients.Results: Here, we found that radioresistant PCa cells and prostate CSCs have a high glutamine demand. GLS-driven catabolism of glutamine serves not only for energy production but also for the maintenance of the redox state. Consequently, glutamine depletion or inhibition of critical regulators of glutamine utilization, such as GLS and the transcription factor MYC results in PCa radiosensitization. On the contrary, we found that a combination of glutamine metabolism inhibitors with irradiation does not cause toxic effects on nonmalignant prostate cells. Glutamine catabolism contributes to the maintenance of CSCs through regulation of the alpha-ketoglutarate (α-KG)-dependent chromatin-modifying dioxygenase. The lack of glutamine results in the inhibition of CSCs with a high aldehyde dehydrogenase (ALDH) activity, decreases the frequency of the CSC populations in vivo and reduces tumor formation in xenograft mouse models. Moreover, this study shows that activation of the ATG5-mediated autophagy in response to a lack of glutamine is a tumor survival strategy to withstand radiation-mediated cell damage. In combination with autophagy inhibition, the blockade of glutamine metabolism might be a promising strategy for PCa radiosensitization. High blood levels of glutamine in PCa patients significantly correlate with a shorter prostate-specific antigen (PSA) doubling time. Furthermore, high expression of critical regulators of glutamine metabolism, GLS1 and MYC, is significantly associated with a decreased progression-free survival in PCa patients treated with radiotherapy.Conclusions: Our findings demonstrate that GLS-driven glutaminolysis is a prognostic biomarker and therapeutic target for PCa radiosensitization.

Evaluation of PSMA-Targeted Theranostic Gold Nanoparticles for Prostate Cancer Imaging and Radiosensitization

Evaluation of PSMA-Targeted Theranostic Gold Nanoparticles for Prostate Cancer Imaging and Radiosensitization

Down-regulation of lncRNA UCA1 enhances radiosensitivity in prostate cancer by suppressing EIF4G1 expression via sponging miR-331-3p

BackgroundWe aimed to explore the role of long noncoding RNA urothelial carcinoma-associated 1 (lncRNA UCA1) and its underlying mechanism in the radioresistance of prostate cancer (PCa).MethodsQRT-PCR was conducted to measure the expression of UCA1, microRNA-331-3p (miR-331-3p) and eukaryotic translation initiation factor 4 gamma 1 (EIF4G1) in PCa tissues and cells. The relative protein level was determined by western blot assay. Cell proliferation and apoptosis were detected by MTT, colony formation assay, and flow cytometry, respectively. The target interaction between miR-331-3p and UCA1 or EIF4G1 was predicted through bioinformatics analysis, and verified by dual-luciferase reporter gene assay system.ResultsThe high levels of UCA1 and EIF4G1 as well as the low level of miR-331-3p were observed in PCa tissues and cell lines. UCA1 and EIF4G1 expression were significantly upregulated by Gy radiation treatement. UCA1 or EIF4G1 knockdown repressed cell growth and enhanced cell apoptosis in 22RV1 and DU145 cells under radiation. Moreover, overexpression of EIF4G1 abolished UCA1 knockdown-induced effect on 6 Gy irradiated PCa cells. UCA1 sponged miR-331-3p to regulate EIF4G1 expression.ConclusionsLncRNA UCA1 deletion suppressed the radioresistance to PCa by suppressing EIF4G1 expression via miR-331-3p. UCA1 acted as a potential regulator of radioresistance of PCa, providing a promising therapeutic target for PCa.

Long Non-Coding RNA GAS5 Suppresses Tumor Progression and Enhances the Radiosensitivity of Prostate Cancer Through the miR-320a/RAB21 Axis.

BackgroundLong non-coding RNAs (lncRNAs) function as a class of significant mediators in prostate cancer (PCa), and this study mainly discussed the molecular mechanism of lncRNA growth arrest-specific 5 (GAS5) in PCa progression and radiosensitivity.Materials and MethodsGAS5 and microRNA-320a (miR-320a) levels were determined by quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability and migration were severally examined through 3-(4, 5-dimethylthiazol-2-y1)-2, 5-diphenyl tetrazolium bromide (MTT) and transwell assays. PCa cells were treated with X-ray irradiation. Cell survival and apoptosis rate were assayed using colony formation assay and flow cytometry, respectively. The apoptosis-related protein and Rab GTPase 21 (RAB21) protein levels were measured by Western blot. The relation between miR-320a and GAS5 or RAB21 was assessed via the dual-luciferase reporter assay. The effect of GAS5 on radiosensitivity of PCa in vivo was evaluated by xenotransplantation assay.ResultsGAS5 was down-regulated in PCa tissues and cells. GAS5 overexpression suppressed cell viability and migration while facilitated radiosensitivity of PCa cells. GAS5 was a molecular sponge of miR-320a. The effects of GAS5 up-regulation on PCa cells were accomplished by sponging miR-320a. MiR-320a targeted RAB21 and GAS5 up-regulated RAB21 expression via targeting miR-320a. RAB21 knockdown reversed the effects of miR-320a inhibition on PCa cells. GAS5 promoted the radiosensitivity of PCa by the miR-320a/RAB21 axis in vivo.ConclusionCollectively, GAS5 restrained tumor development and expedited the radiosensitivity in PCa by the miR-320a/RAB21 axis, which provided a molecular regulatory mechanism of GAS5/miR-320a/RAB21 in PCa development and radioresistance.

Second-Generation Antiandrogen Therapy Radiosensitizes Prostate Cancer Regardless of Castration State through Inhibition of DNA Double Strand Break Repair.

Simple SummaryThe combination of RT and the first generation AR blockers to improve the outcome in prostate cancer remain a matter of controversial debate in clinical trials. In the current study we aim to investigate the effect of three FDA approved second-generation antiandrogens (abiraterone acetate, apalutamide and enzalutamide), as more potent inhibitors of the AR signaling, on the cytotoxicity of RT in pre-clinical models. In vitro and ex vivo analyses revealed a strong radiosensitising effect for the second-generation antiandrogens, regardless of the castration state. The first-generation AR-blocker bicalutamide failed to show any radiosensitising effect. The radiosensitising effect of the second-generation antiandrogens was attributed to the inhibition of DSB repair. Together, we provide a proof-of-principle pre-clinical evidence to rationalize the clinical use of the second-generation antiandrogens to enhance the effect of IR as a potential strategy to improve the outcomes of PCa patients with localized disease who undergo ablative RT.(1) Background: The combination of the first-generation antiandrogens and radiotherapy (RT) has been studied extensively in the clinical setting of prostate cancer (PCa). Here, we evaluated the potential radiosensitizing effect of the second-generation antiandrogens abiraterone acetate, apalutamide and enzalutamide. (2) Methods: Cell proliferation and agarose-colony forming assay were used to measure the effect on survival. Double strand break repair efficiency was monitored using immunofluorescence staining of γH2AX/53BP1. (3) Results: We report retrospectively a minor benefit for PCa patients received first-generation androgen blockers and RT compared to patients treated with RT alone. Combining either of the second-generation antiandrogens and 2Gy suppressed cell growth and increased doubling time significantly more than 2Gy alone, in both hormone-responsive LNCaP and castration-resistant C4-2B cells. These findings were recapitulated in resistant sub-clones to (i) hormone ablation (LNCaP-abl), (ii) abiraterone acetate (LNCaP-abi), (iii) apalutamide (LNCaP-ARN509), (iv) enzalutamide (C4-2B-ENZA), and in castration-resistant 22-RV1 cells. This radiosensitization effect was not observable using the first-generation antiandrogen bicalutamide. Inhibition of DNA DSB repair was found to contribute to the radiosensitization effect of second-generation antiandrogens, as demonstrated by a significant increase in residual γH2AX and 53BP1 foci numbers at 24h post-IR. DSB repair inhibition was further demonstrated in 22 patient-derived tumor slice cultures treated with abiraterone acetate before ex-vivo irradiation with 2Gy. (4) Conclusion: Together, these data show that second-generation antiandrogens can enhance radiosensitivity in PCa through DSB repair inhibition, regardless of their hormonal status. Translated into clinical practice, our results may help to find additional strategies to improve the effectiveness of RT in localized PCa, paving the way for a clinical trial.