Improving Taxane-Based Chemotherapy in Castration-Resistant Prostate Cancer

PAF1-mediated transcriptional reprogramming confers docetaxel resistance in advanced prostate cancer

Advanced prostate cancer (PCa) remains a significant clinical challenge, and docetaxel plays a significant role in disease management. Despite the efficacy of docetaxel as a first-line chemotherapy, resistance often develops. We developed three clinically relevant in vitro PCa cell models and transcriptomic analysis identified that the Paf1/RNA polymerase II complex component (PAF1)-associated pluripotent-transcription factor (TF), SOX2, plays a crucial role in docetaxel resistance. The cancer stem cell (CSC) transcriptional master regulator PAF1 is significantly higher in PCa cell lines, tumor tissues, and docetaxel resistant (DR) PCa cells than in age-matched control cells. To determine the molecular underlying and functional characteristics of PAF1 in resistance mechanisms, we performed coimmunoprecipitation, embryonic stem cell network proteins, in vitro tumor-initiating ability, and 3D multicellular organoid growth using PAF1 knockdown cells. Tet-inducible PAF1 depletion reduced the drug-efflux phenotype, tumor-initiating frequencies, and three-dimensional organoid growth of the docetaxel-resistant PCa cell lines. Functional studies also showed restoration of docetaxel sensitivity in a 3D tumorsphere model upon PAF1 depletion. PAF1 depletion was also associated with decreased pluripotent TFs and other CSC markers. This study provides a novel regulatory mechanism of docetaxel resistance in PCa through PAF1.

Docetaxel-Induced Cell Death Is Regulated by a Fatty Acid-Binding Protein 12-Slug-Survivin Pathway in Prostate Cancer Cells

Chemotherapy is an important treatment option for advanced prostate cancer, especially for metastatic prostate cancer (PCa). Resistance to first-line chemotherapeutic drugs such as docetaxel often accompanies prostate cancer progression. Attempts to overcome resistance to docetaxel by combining docetaxel with other biological agents have been mostly unsuccessful. A better understanding of the mechanisms underlying docetaxel resistance may provide new avenues for the treatment of advanced PCa. We have previously found that the fatty acid-binding protein 12 (FABP12)-PPARγ pathway modulates lipid-related bioenergetics and PCa metastatic transformation through induction of Slug, a master driver of epithelial-to-mesenchymal transition (EMT). Here, we report that the FABP12-Slug axis also underlies chemoresistance in PCa cells. Cell sensitivity to docetaxel is markedly suppressed in FABP12-expressing cells, along with induction of Survivin, a typical apoptosis inhibitor, and inhibition of cleaved PARP, a hallmark of programmed cell death. Importantly, Slug depletion down-regulates Survivin and restores cell sensitivity to docetaxel in FABP12-expressing cells. Finally, we also show that high levels of Survivin are associated with poor prognosis in PCa patients, with FABP12 status determining its prognostic significance. Our research identifies a FABP12-Slug-Survivin pathway driving docetaxel resistance in PCa cells, suggesting that targeting FABP12 may be a precision approach to improve chemodrug efficacy and curb metastatic progression in PCa.

Targeting heme degradation pathway augments prostate cancer cell sensitivity to docetaxel-induced apoptosis and attenuates migration

Introduction

Chemotherapy, notably docetaxel (Doc), stands as the primary treatment for castration-resistant prostate cancer (CRPC). However, its efficacy is hindered by side effects and chemoresistance. Hypoxia in prostate cancer (PC) correlates with chemoresistance to Doc-induced apoptosis via Heme Oxygenase-1 (HO-1) modulation, a key enzyme in heme metabolism. This study investigated targeting heme degradation pathway via HO-1 inhibition to potentiate the therapeutic efficacy of Doc in PC.

Methods

Utilizing diverse PC cell lines, we evaluated HO-1 inhibition alone and with Doc on viability, apoptosis, migration, and epithelial- to- mesenchymal transition (EMT) markers and elucidated the underlying mechanisms.

Results

HO-1 inhibition significantly reduced PC cell viability under hypoxic and normoxic conditions, enhancing Doc-induced apoptosis through interconnected mechanisms, including elevated reactive oxygen species (ROS) levels, glutathione cycle disruption, and modulation of Signal Transducer and Activator of Transcription 1 (STAT1) pathway. The interplay between STAT1 and HO-1 suggests its reliance on HO-1 activation. Additionally, a decrease in cell migration and downregulation of EMT markers (vimentin and snail) were observed, indicating attenuation of mesenchymal phenotype.

Discussion

In conclusion, the combination of HO-1 inhibition with Doc holds promise for improving therapeutic outcomes and advancing clinical management in PC.

Tumor mitochondrial oxidative phosphorylation stimulated by the nuclear receptor RORγ represents an effective therapeutic opportunity in osteosarcoma

Osteosarcoma (OS) is the most common malignant bone tumor with a poor prognosis. Here, we show that the nuclear receptor RORγ may serve as a potential therapeutic target in OS. OS exhibits a hyperactivated oxidative phosphorylation (OXPHOS) program, which fuels the carbon source to promote tumor progression. We found that RORγ is overexpressed in OS tumors and is linked to hyperactivated OXPHOS. RORγ induces the expression of PGC-1β and physically interacts with it to activate the OXPHOS program by upregulating the expression of respiratory chain component genes. Inhibition of RORγ strongly inhibits OXPHOS activation, downregulates mitochondrial functions, and increases ROS production, which results in OS cell apoptosis and ferroptosis. RORγ inverse agonists strongly suppressed OS tumor growth and progression and sensitized OS tumors to chemotherapy. Taken together, our results indicate that RORγ is a critical regulator of the OXPHOS program in OS and provides an effective therapeutic strategy for this deadly disease.

Combined in vitro/in vivo genome-wide CRISPR screens in triple negative breast cancer identify cancer stemness regulators in paclitaxel resistance

Triple negative breast cancer (TNBC) is defined as lacking the expressions of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). TNBC patients exhibit relatively poor clinical outcomes due to lack of molecular markers for targeted therapies. As such chemotherapy often remains the only systemic treatment option for these patients. While chemotherapy can initially help shrink TNBC tumor size, patients eventually develop resistance to drug, leading to tumor recurrence. We report a combined in vitro/in vivo genome-wide CRISPR synthetic lethality screening approach in a relevant TNBC cell line model to identify several targets responsible for the chemotherapy drug, paclitaxel resistance. Computational analysis integrating in vitro and in vivo data identified a set of genes, for which specific loss-of-function deletion enhanced paclitaxel resistance in TNBC. We found that several of these genes (ATP8B3, FOXR2, FRG2, HIST1H4A) act as cancer stemness negative regulators. Finally, using in vivo orthotopic transplantation TNBC models we showed that FRG2 gene deletion reduced paclitaxel efficacy and promoted tumor metastasis, while increasing FRG2 expression by means of CRISPR activation efficiently sensitized TNBC tumors to paclitaxel treatment and inhibited their metastatic abilities. In summary, the combined in vitro/in vivo genome-wide CRISPR screening approach proved effective as a tool to identify novel regulators of paclitaxel resistance/sensitivity and highlight the FRG2 gene as a potential therapeutical target overcoming paclitaxel resistance in TNBC.

Current development of cabazitaxel drug delivery systems

The second-generation taxane cabazitaxel has been clinically approved for the treatment of metastatic castration-resistant prostate cancer after docetaxel failure. Compared with the first-generation taxanes paclitaxel and docetaxel, cabazitaxel has potent anticancer activity and is less prone to drug resistance due to its lower affinity for the P-gp efflux pump. The relatively high hydrophobicity of cabazitaxel and the poor aqueous colloidal stability of the commercial formulation, following its preparation for injection, presents opportunities for new cabazitaxel formulations with improved features. This review provides an overview of cabazitaxel drug formulations and hydrophobic taxane drug delivery systems in general, and particularly focuses on emerging cabazitaxel delivery systems discovered in the past 5 years. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Nanoalbumin-prodrug conjugates prepared via a thiolation-and-conjugation method improve cancer chemotherapy and immune checkpoint blockade therapy by promoting CD8+ T-cell infiltration

Protein-drug conjugates are emerging tools to combat cancers. Here, we adopted an indirect thiolation-and-conjugation method as a general strategy to prepare protein-drug conjugates. We found for the first time that this method led to the formation of nanometric conjugates, probably due to the formation of intermolecular disulfide bonds, which facilitated enhanced uptake by cancer cells. As a proof-of-concept application in cancer therapy, a nanometric albumin-doxorubicin prodrug conjugate (NanoAlb-proDOX) was prepared. The nanometric size promoted its uptake by cancer cells, and the prodrug characteristic defined its selective cytotoxicity toward cancer cells in vitro and reduced side effects in vivo. In multiple tumor xenograft models, nanometric NanoAlb-proDOX showed superior antitumor activity and synergy with immune checkpoint blockade, probably due to the synergistically enhanced tumor CD8+ T-cell infiltration and activation. Hence, the thiolation-and-conjugation strategy may serve as a generally applicable method for preparing drug conjugates, and the proof-of-concept nanometric albumin-doxorubicin conjugate may be a good choice for antitumor therapy with the ability to co-stimulate the efficacy of immune checkpoint blockade.

An in vitro redox adaptation model for metastatic prostate cancer: Establishing, characterizing, and Cabazitaxel response evaluating

Little is known about the redox-adapted cancer cells for understanding their pharmacologically targetable features and chemotherapeutic responses. Thus, we presented the first in vitro redox adaptation model for metastatic prostate cancer (mPC), LNCaP-HPR, with enhanced oxidative stress resistance accompanying poor Cabazitaxel response. After establishing, the cells were characterized by comparing the viability, death, oxidative stress, total GSH levels, and the mRNA and protein levels of the redox-sensitive transcription factors responsible for the adaptation, Nrf-2, NF-κB, and HIF-1α. Then, the apoptotic effect of Cabazitaxel was evaluated in LNCaP mPC, LNCaP-HPR, and C4-2 metastatic castration-resistant (mCRPC) cells. In response to H₂ O₂ , viability, oxidative stress, and the total GSH levels of LNCaP-HPR cells have confirmed the oxidative stress resistance. Nrf-2, NF-κB, and HIF-1α were upregulated in LNCaP-HPR cells, not in LNCaP, confirming that resistant cells were much less affected by exogenous oxidative stress. Unlike LNCaP, LNCaP-HPR cells were less sensitive to Cabazitaxel, as closer to the response of C4-2 mCRPC cells, indicating that redox adaptation decreased Cabazitaxel response. This is the first evaluated association between redox adaptation and poor Cabazitaxel response, suggesting that in vitro Cabazitaxel efficiency is affected by PC cells' endogenous oxidative stress tolerance. This article is protected by copyright. All rights reserved.

Anemoside B4 sensitizes human colorectal cancer to fluorouracil-based chemotherapy through src-mediated cell apoptosis

Currently, 5-Fluorouracil (5-FU) based chemotherapy is the primary option for colorectal cancer after surgery, whereas chemotherapy resistance related mortality is observed in a large proportion of patients. Anemoside B4 (AB4) is a triterpene saponin, which exhibits a considerable activity in oncotherapy. In this study, we explored the efficacy of AB4 in FU-based chemotherapy in colorectal cancer cells and the underlying molecular mechanisms. Our results indicated a significant synergistic activity of AB4 in 5-FU treated colorectal cancer cells. Furthermore, AB4 treatment eliminated colorectal cancer stem cells by promoting apoptotic cell death in 5-FU resistant colorectal cancer cells. Mechanically, AB4 activated caspase-9 pathway in 5-FU resistant colorectal cancer cells. Elevated Src activity induced cell apoptosis and cancer stem cells elimination effects in AB4 treated colorectal cancer cells. In conclusion, AB4 showed promising sensitization effect in the FU-based chemotherapy of colorectal cancer. Our study may pave a way to ameliorate FU-based chemotherapeutic efficiency in colorectal cancer.

Ceramide Regulates Anti-Tumor Mechanisms of Erianin in Androgen-Sensitive and Castration-Resistant Prostate Cancers

Prostate cancer is the second most prevalent malignancy worldwide. In the early stages, the development of prostate cancer is dependent on androgens. Over time with androgen deprivation therapy, 20% of prostate cancers progress to a castration-resistant form. Novel treatments for prostate cancers are still urgently needed. Erianin is a plant-derived bibenzyl compound. We report herein that erianin exhibits anti-tumor effects in androgen-sensitive and castration-resistant prostate cancer cells through different mechanisms. Erianin induces endoplasmic reticulum stress-associated apoptosis in androgen-sensitive prostate cancer cells. It also triggers pro-survival autophagic responses, as inhibition of autophagy predisposes to apoptosis. In contrast, erianin fails to induce apoptosis in castration-resistant prostate cancer cells. Instead, it results in cell cycle arrest at the M phase. Mechanistically, C16 ceramide dictates differential responses of androgen-sensitive and castration-resistant prostate cancer cells to erianin. Erianin elevates C16 ceramide level in androgen-sensitive but not castration-resistant prostate cancer cells. Overexpression of ceramide synthase 5 that specifically produces C16 ceramide enables erianin to induce apoptosis in castration-resistant prostate cancer cells. Our study provides both experimental evidence and mechanistic data showing that erianin is a potential treatment option for prostate cancers.

Role of noncoding RNA in drug resistance of prostate cancer

Prostate cancer is one of the most prevalent forms of cancer around the world. Androgen-deprivation treatment and chemotherapy are the curative approaches used to suppress prostate cancer progression. However, drug resistance is extensively and hard to overcome even though remarkable progress has been made in recent decades. Noncoding RNAs, such as miRNAs, lncRNAs, and circRNAs, are a group of cellular RNAs which participate in various cellular processes and diseases. Recently, accumulating evidence has highlighted the vital role of non-coding RNA in the development of drug resistance in prostate cancer. In this review, we summarize the important roles of these three classes of noncoding RNA in drug resistance and the potential therapeutic applications in this disease.

Recent progress in nanoformulations of cabazitaxel

The antitumor efficacy of various paclitaxel (PTX) and docetaxel (DTX) formulations in clinical applications is seriously affected by drug resistance. Cabazitaxel, a second-generation taxane, exhibits greater anticancer activity than paclitaxel and docetaxel and has low affinity for the P-glycoprotein (P-gp) efflux pump because of its structure. Therefore, cabazitaxel has the potential to overcome taxane resistance. However, owing to the high systemic toxicity and hydrophobicity of cabazitaxel and the instability of its commercial preparation, Jevtana®, the clinical use of cabazitaxel is restricted to patients with metastatic castration-resistant prostate cancer (mCRPC) who show progression after docetaxel-based chemotherapy. Nanomedicine is expected to overcome the limitations associated with cabazitaxel application and surmount taxane resistance. This review outlines the drug delivery systems of cabazitaxel published in recent years, summarizes the challenges faced in the development of cabazitaxel nanoformulations, and proposes strategies to overcome these challenges.

Peritumoral Delivery of Docetaxel-TIPS Microparticles for Prostate Cancer Adjuvant Therapy

Recurrence of prostate cancer after radical prostatectomy is a consequence of incomplete tumor resection. Systemic chemotherapy after surgery is associated with significant toxicity. Improved delivery methods for toxic drugs capable of targeting positive resection margins can reduce tumor recurrence and avoid their known toxicity. This study evaluates the effectiveness and toxicity of docetaxel (DTX) release from highly porous biodegradable microparticles intended for delivery into the tissue cavity created during radical prostatectomy to target residual tumor cells. The microparticles, composed of poly(dl-lactide-co-glycolide) (PLGA), are processed using thermally induced phase separation (TIPS) and loaded with DTX via antisolvent precipitation. Sustained drug release and effective toxicity in vitro are observed against PC3 human prostate cells. Peritumoral injection in a PC3 xenograft tumor model results in tumor growth inhibition equivalent to that achieved with intravenous delivery of DTX. Unlike intravenous delivery of DTX, implantation of DTX-TIPS microparticles is not accompanied by toxicity or elevated systemic levels of DTX in organ tissues or plasma. DTX-TIPS microparticles provide localized and sustained release of nontoxic therapeutic amounts of DTX. This may offer novel therapeutic strategies for improving management of patients with clinically localized high-risk disease requiring radical prostatectomy and other solid cancers at high risk of positive resection margins.

Recent Advances and Implication of Bioengineered Nanomaterials in Cancer Theranostics

Cancer is one of the most common causes of death and affects millions of lives every year. In addition to non-infectious carcinogens, infectious agents contribute significantly to increased incidence of several cancers. Several therapeutic techniques have been used for the treatment of such cancers. Recently, nanotechnology has emerged to advance the diagnosis, imaging, and therapeutics of various cancer types. Nanomaterials have multiple advantages over other materials due to their small size and high surface area, which allow retention and controlled drug release to improve the anti-cancer property. Most cancer therapies have been known to damage healthy cells due to poor specificity, which can be avoided by using nanosized particles. Nanomaterials can be combined with various types of biomaterials to make it less toxic and improve its biocompatibility. Based on these properties, several nanomaterials have been developed which possess excellent anti-cancer efficacy potential and improved diagnosis. This review presents the latest update on novel nanomaterials used to improve the diagnostic and therapeutic of pathogen-associated and non-pathogenic cancers. We further highlighted mechanistic insights into their mode of action, improved features, and limitations.

Taxanes in cancer treatment: Activity, chemoresistance and its overcoming

Since 1984, when paclitaxel was approved by the FDA for the treatment of advanced ovarian carcinoma, taxanes have been widely used as microtubule-targeting antitumor agents. However, their historic classification as antimitotics does not describe all their functions. Indeed, taxanes act in a complex manner, altering multiple cellular oncogenic processes including mitosis, angiogenesis, apoptosis, inflammatory response, and ROS production. On the one hand, identification of the diverse effects of taxanes on oncogenic signaling pathways provides opportunities to apply these cytotoxic drugs in a more rational manner. On the other hand, this may facilitate the development of novel treatment modalities to surmount anticancer drug resistance. In the latter respect, chemoresistance remains a major impediment which limits the efficacy of antitumor chemotherapy. Taxanes have shown impact on key molecular mechanisms including disruption of mitotic spindle, mitosis slippage and inhibition of angiogenesis. Furthermore, there is an emerging contribution of cellular processes including autophagy, oxidative stress, epigenetic alterations and microRNAs deregulation to the acquisition of taxane resistance. Hence, these two lines of findings are currently promoting a more rational and efficacious taxane application as well as development of novel molecular strategies to enhance the efficacy of taxane-based cancer treatment while overcoming drug resistance. This review provides a general and comprehensive picture on the use of taxanes in cancer treatment. In particular, we describe the history of application of taxanes in anticancer therapeutics, the synthesis of the different drugs belonging to this class of cytotoxic compounds, their features and the differences between them. We further dissect the molecular mechanisms of action of taxanes and the molecular basis underlying the onset of taxane resistance. We further delineate the possible modalities to overcome chemoresistance to taxanes, such as increasing drug solubility, delivery and pharmacokinetics, overcoming microtubule alterations or mitotic slippage, inhibiting drug efflux pumps or drug metabolism, targeting redox metabolism, immune response, and other cellular functions.

Silica-Based Nanoparticles as Drug Delivery Vehicles for Prostate Cancer Treatment

Prostate cancer (PCa) is one of the most commonly diagnosed cancers and is the fifth common cause of cancer-related mortality in men. Current methods for PCa treatment are insufficient owing to the challenges related to the non-specificity, instability and side effects caused by the drugs and therapy agents. These drawbacks can be mitigated by the design of a suitable drug delivery system that can ensure targeted delivery and minimise side effects. Silica based nanoparticles (SBNPs) have emerged as one of the most versatile materials for drug delivery due to their tunable porosities, high surface area and tremendous capacity to load various sizes and chemistry of drugs. This review gives a brief overview of the diagnosis and current treatment strategies for PCa outlining their existing challenges. It critically analyzes the design, development and application of pure, modified and hybrid SBNPs based drug delivery systems in the treatment of PCa, their advantages and limitations.

Microfluidic Manufacturing of Multitargeted PLGA/PEG Nanoparticles for Delivery of Taxane Chemotherapeutics

Taxane chemotherapeutics have played a key role in the treatment of various types of cancer throughout the past years. However, the drawbacks inherent to the pharmaceutical formulation of taxanes are still a reality and mainly due to the low aqueous solubility of these medicines, as well as to the nontargeted therapy and consequent side effects. Nanoparticles (NPs) of poly(lactic-co-glycolic acid) (PLGA) and polyethylene glycol (PEG) have sparked broad interest in this field and demonstrated capacity of improving taxanes' formulation. If, in one hand, the PLGA core of these NPs is able to solubilize drugs, on the other hand, the PEG shell promotes immune escape and presents chemical end groups for the attachment of targeting ligands. Advances in the design of these nanosystems resulted in the development of multitargeted PLGA/PEG NPs achieved by dual-ligand functionalization. The multitargeting offers a promising alternative to the delivery of taxanes across successive cell types or compartments and to the synergetic exploitation of more than one transporter on the cell surface. Besides the upgrade in the design of multitargeted PLGA/PEG NPs, their manufacturing has also evolved from bulk assembly to continuous-flow, high-throughput technologies such as microfluidics. This technology relies on microchannel platforms described to enable the production of large-scale batches of NPs in a better time-saving manner, with higher drug loading, reproducibility, and lower polydispersity. Herein, a detailed microfluidic method for the preparation of multitargeted, taxane-loaded PLGA/PEG NPs is described. Focus is given to the setting up of the microfluidic system and conditions required to manufacture these NPs by using polymers of PLGA and PEG previously elsewhere functionalized with two generic targeting ligands.

Prostate Cancer Metastases Are Strongly Inhibited by Agonistic Epha2 Ligands in an Orthotopic Mouse Model

Simple Summary

We demonstrate that pro-oncogenic EphA2 (ephrin type-A receptor 2) expression is activated in aggressive prostate cancers, and in mouse models of prostate cancers that are treated with enzalutamide. We also demonstrate in mouse models, that agonistic EphA2 targeting agents are very effective in suppressing cell migration and tumor metastases, hence anticipating the possible use of such agents in innovative anti-metastatic therapeutic modalities.

Abstract

The EphA2 tyrosine kinase receptor is highly expressed in several types of solid tumors. In our recent studies, we targeted EphA2 in pancreatic cancer with agonistic agents and demonstrated that suppression of EphA2 significantly reduced cancer-cell migration in cell-based assays. In the present study, we focused on targeting EphA2 in prostate cancer. While not all prostate cancers express EphA2, we showed that enzalutamide induced EphA2 expression in prostate cancer cells and in a patient-derived xenograft (PDX) animal model, which provides further impetus to target EphA2 in prostate cancer. Western blot studies showed that agonistic dimeric synthetic (135H12) and natural (ephrinA1-Fc) ligands effectively degraded EphA2 receptor in the prostate cancer cell line PC-3. The agents also delayed cell migration of prostate cancer (PC-3) cells, while an in vivo PC-3 orthotopic metastatic nude-mouse model also revealed that administration of ephrinA1-Fc or 135H12 strongly reduced metastases. The present study further validates EphA2 as an important target in metastatic prostate cancer treatment. Our results should incentivize further efforts aimed at developing potent and effective EphA2 synthetic agonistic agents for the treatment of EphA2-driven aggressive metastatic tumors including prostate, pancreatic, and breast cancer.

Molecular mechanisms of docetaxel resistance in prostate cancer

Docetaxel (DTX) chemotherapy offers excellent initial response and confers significant survival benefit in patients with castration-resistant prostate cancer (CRPC). However, the clinical utility of DTX is compromised when primary and acquired resistance are encountered. Therefore, a more thorough understanding of DTX resistance mechanisms may potentially improve survival in patients with CRPC. This review focuses on DTX and discusses its mechanisms of resistance. We outline the involvement of tubulin alterations, androgen receptor (AR) signaling/AR variants, ERG rearrangements, drug efflux/influx, cancer stem cells, centrosome clustering, and phosphoinositide 3-kinase/AKT signaling in mediating DTX resistance. Furthermore, potential biomarkers for DTX treatment and therapeutic strategies to circumvent DTX resistance are reviewed.

The Wnt non-canonical signaling modulates cabazitaxel sensitivity in prostate cancer cells

Background

Despite new drugs, metastatic prostate cancer remains fatal. Growing interest in the latest approved cabazitaxel taxane drug has markedly increased due to the survival benefits conferred when used at an earlier stage of the disease, its promising new therapeutic combination and formulation, and its differential toxicity. Still cabazitaxel’s mechanisms of resistance are poorly characterized. The goal of this study was thus to generate a new model of acquired resistance against cabazitaxel in order to unravel cabazitaxel’s resistance mechanisms.

Methods

Du145 cells were cultured with increasing concentrations of cabazitaxel, docetaxel/ taxane control or placebo/age-matched control. Once resistance was reached, Epithelial-to-Mesenchymal Translation (EMT) was tested by cell morphology, cell migration, and E/M markers expression profile. Cell transcriptomics were determined by RNA sequencing; related pathways were identified using IPA, PANTHER or KEGG software. The Wnt pathway was analyzed by western blotting, pharmacological and knock-down studies.

Results

While age-matched Du145 cells were sensitive to both taxane drugs, docetaxel-resistant cells were only resistant to docetaxel and cabazitaxel-resistant cells showed a partial cross-resistance to both drugs concomitant to EMT. Using RNA-sequencing, the Wnt non-canonical pathway was identified as exclusively activated in cabazitaxel resistant cells while the Wnt canonical pathway was restricted to docetaxel-resistant cells. Cabazitaxel-resistant cells showed a minimal crossover in the Wnt-pathway-related genes linked to docetaxel resistance validating our unique model of acquired resistance to cabazitaxel. Pharmacological and western blot studies confirmed these findings and suggest the implication of the Tyrosine kinase Ror2 receptor in cabazitaxel resistant cells. Variation in Ror2 expression level altered the sensitivity of prostate cancer cells to both drugs identifying a possible new target for taxane resistance.

Conclusion

Our study represents the first demonstration that while Wnt pathway seems to play an important role in taxanes resistance, Wnt effectors responsible for taxane specificity remain un-identified prompting the need for more studies.

Enhanced docetaxel delivery using sterically stabilized RIPL peptide-conjugated nanostructured lipid carriers: In vitro and in vivo antitumor efficacy against SKOV3 ovarian cancer cells

Docetaxel (DTX) has poor solubility, low specificity, and severe side effects. For efficient targeting of DTX to hepsin-overexpressing SKOV3 ovarian cancer cells, PEGylated and RIPL peptide (IPLVVPLRRRRRRRRC)-conjugated nanostructured lipid carriers (PEG-RIPL-NLCs) were examined for in vitro and in vivo antitumor efficacy. DTX-loaded plain NLCs (DTX-pNLCs), RIPL-NLCs (DTX-RIPL-NLCs), and PEG-RIPL-NLCs (DTX-PEG-RIPL-NLCs) were prepared using a solvent emulsification-evaporation technique. DTX was successfully loaded with high encapsulation efficiency (>93%), and all NLCs showed homogeneous dispersion with zeta potentials varying from -17 to 15 mV. Drug release was biphasic: initial rapid release, then gradual release. In vitro cytotoxicity was time- and dose-dependent: DTX-RIPL-NLCs and DTX-PEG-RIPL-NLCs exhibited greater cytotoxicity, enhanced cell apoptosis owing to the cell cycle arrest in the G2/M phase, and increased activation of the mitochondria-related intrinsic apoptosis pathway compared to DTX-pNLCs. Pharmacokinetic experiments in male Sprague-Dawley rats revealed that DTX-PEG-RIPL-NLCs increased the mean residence time of DTX but reduced total body clearance and volume of distribution. In a SKOV3-bearing xenograft Balb/c athymic mouse model, DTX-PEG-RIPL-NLCs suppressed tumors, evidenced by tumor volume change and histopathological examination. Thus, we conclude that PEG-RIPL-NLCs have an advantage of high payload of poorly water-soluble drugs and are a good candidate for drug targeting to SKOV3-derived ovarian cancer.

Therapeutic Targeting of MDR1 Expression by RORγ Antagonists Resensitizes Cross-Resistant CRPC to Taxane via Coordinated Induction of Cell Death Programs

Overexpression of ATP-binding cassette subfamily B member 1 (ABCB1)-encoded multidrug resistance protein 1 (MDR1) constitutes a major mechanism of cancer drug resistance including docetaxel (DTX) and cabazitaxel (CTX) resistance in castration-resistant prostate cancer (CRPC). However, no therapeutics that targets MDR1 is available at clinic for taxane sensitization. We report here that retinoic acid receptor-related orphan receptor γ (RORγ), a nuclear receptor family member, unexpectedly mediates MDR1/ABCB1 overexpression. RORγ plays an important role in controlling the functions of subsets of immune cells and has been an attractive target for autoimmune diseases. We found that its small-molecule antagonists are efficacious in resensitizing DTX and CTX cross-resistant CRPC cells and tumors to taxanes in both androgen receptor-positive and -negative models. Our mechanistic analyses revealed that combined treatment with RORγ antagonists and taxane elicited a robust synergy in killing the resistant cells, which involves a coordinated alteration of p53, Myc, and E2F-controlled programs critical for both intrinsic and extrinsic apoptosis, survival, and cell growth. Our results suggest that targeting RORγ with small-molecule inhibitors is a novel strategy for chemotherapy resensitization in tumors with MDR1 overexpression.

Downregulation of class II phosphoinositide 3-kinase PI3K-C2β delays cell division and potentiates the effect of docetaxel on cancer cell growth

Background

Alteration of signalling pathways regulating cell cycle progression is a common feature of cancer cells. Several drugs targeting distinct phases of the cell cycle have been developed but the inability of many of them to discriminate between normal and cancer cells has strongly limited their clinical potential because of their reduced efficacy at the concentrations used to limit adverse side effects. Mechanisms of resistance have also been described, further affecting their efficacy. Identification of novel targets that can potentiate the effect of these drugs or overcome drug resistance can provide a useful strategy to exploit the anti-cancer properties of these agents to their fullest.

Methods

The class II PI3K isoform PI3K-C2β was downregulated in prostate cancer PC3 cells and cervical cancer HeLa cells using selective siRNAs and the effect on cell growth was determined in the absence or presence of the microtubule-stabilizing agent/anti-cancer drug docetaxel. Mitosis progression was monitored by time-lapse microscopy. Clonogenic assays were performed to determine the ability of PC3 and HeLa cells to form colonies upon PI3K-C2β downregulation in the absence or presence of docetaxel. Cell multi-nucleation was assessed by immunofluorescence. Tumour growth in vivo was assessed using a xenograft model of PC3 cells upon PI3K-C2β downregulation and in combination with docetaxel.

Results

Downregulation of PI3K-C2β delays mitosis progression in PC3 and HeLa cells, resulting in reduced ability to form colonies in clonogenic assays in vitro. Compared to control cells, PC3 cells lacking PI3K-C2β form smaller and more compact colonies in vitro and they form tumours more slowly in vivo in the first weeks after cells implant. Stable and transient PI3K-C2β downregulation potentiates the effect of low concentrations of docetaxel on cancer cell growth. Combination of PI3K-C2β downregulation and docetaxel almost completely prevents colonies formation in clonogenic assays in vitro and strongly inhibits tumour growth in vivo.

Conclusions

These data reveal a novel role for the class II PI3K PI3K-C2β during mitosis progression. Furthermore, data indicate that blockade of PI3K-C2β might represent a novel strategy to potentiate the effect of docetaxel on cancer cell growth.

The androgen receptor antagonist enzalutamide induces apoptosis, dysregulates the heat shock protein system, and diminishes the androgen receptor and estrogen receptor β1 expression in prostate cancer cells

Enzalutamide's accepted mode of action is by targeting the androgen receptor's (AR) activity. In clinical practice, enzalutamide demonstrates a good benefit-risk profile for the treatment of advanced prostate cancer (PC), even after poor response to standard antihormonal treatment. However, since both, well-established antiandrogens and enzalutamide, target AR functionality, we hypothesized that additional unknown mechanisms might be responsible for enzalutamide's superior anticancer activity. In the current study, PC cells were incubated with enzalutamide and enzalutamide-dependent modulation of apoptotic mechanisms were assessed via Western blot analysis, TDT-mediated dUTP-biotin nick end-labeling assay, and nuclear morphology assay. Alterations of heat shock protein (HSP), AR, and estrogen receptor (ER) expression were examined by Western blot analysis. Enzalutamide attenuated the proliferation of PC cells in a time- and dose-dependent manner. In the presence of enzalutamide, apoptosis occurred which was shown by increased BAX expression, decreased Bcl-2 expression, nuclear pyknosis, and genomic DNA fragmentation. Moreover, enzalutamide inhibited the expression of HSPs primarily involved in steroid receptor stabilization and suppressed AR and ERβ1 expression. This study demonstrates for the first time that enzalutamide treatment of PC cells triggers varying molecular mechanisms resulting in antiproliferative effects of the drug. In addition to the well-characterized antagonistic inhibition of AR functionality, we have shown that enzalutamide also affects the intracellular synthesis of steroid receptor-associated HSPs, thereby diminishing the expression of AR and ERβ1 proteins and inducing apoptotic pathways. According to an indirect attenuation of HSP-associated factors such as steroid receptors, endometrial carcinoma, uterine leiomyosarcoma, and mamma carcinoma cells also demonstrated inhibited cell growth in the presence of enzalutamide. Our data, therefore, suggest that enzalutamide's high efficacy is at least partially independent of AR and p53 protein expression, which are frequently lost in advanced PC.

Cotargeting Plk1 and androgen receptor enhances the therapeutic sensitivity of paclitaxel-resistant prostate cancer

Backgrounds:

Despite the clinical success of taxanes, they still have limitations, such as chemoresistance. To overcome the limitations of paclitaxel, genetic alterations and targeting effects of altered genes were observed in paclitaxel-resistant cancer. Because paclitaxel-resistant cancer shows high levels of Plk1, a promising target in chemotherapy, the effectiveness of Plk1 inhibitors in paclitaxel-resistant cancer cells has been investigated.

Methods:

Paclitaxel-resistant cancer cells were developed by exposure of stepwise escalating levels of paclitaxel. Genetic alterations were detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunoblotting. Using a cell viability assay, combined targeting effects for Plk1 and androgen receptor (AR) were determined. Clinical data were analyzed to understand the relationship between Plk1 and AR in prostate cancer patients.

Results:

Treatment with Plk1 inhibitors markedly reduced the expression of MDR1, MRP1, and Plk1 in the paclitaxel-resistant cancer. Among Plk1 inhibitors, genistein, recently found as a direct Plk1 inhibitor, tended to be more effective in the paclitaxel-resistant prostate cancer than the parental cancer cells, which was related to the suppression of the AR, as well as inhibition of Plk1 activity. A combination of Plk1 inhibitors and AR antagonist bicalutamide exhibited a synergistic effect in LNCaP^TXR, as well as LNCaP cells, by inhibiting Plk1 and AR. Analysis of clinical data provides evidence for the relevance between Plk1 and AR in prostate cancer patients, showing that Plk1 and AR are strong predictors of poor survival rates.

Conclusions:

We suggest that cotargeting Plk1 and AR would be effective in advanced chemoresistant prostate cancer cells to overcome the limitations associated with paclitaxel.

Effects of Black Raspberries and Their Ellagic Acid and Anthocyanin Constituents on Taxane Chemotherapy of Castration-Resistant Prostate Cancer Cells

Cancer patients often use dietary supplements while on therapy, but little is known about interactions of supplements with cancer chemotherapy. Black raspberries (BRB) have anti-cancer effects, but have not been evaluated for interference with chemotherapy for castrate-resistant prostate cancer (CRPC). Here we studied whether BRB and some of their constituents interact with docetaxel and cabazitaxel on CRPC cells in culture and implanted into nude mice. Ellagic acid increased, but BRB extract inhibited, microtubule assembly. Ellagic acid decreased tubulin polymerization by cabazitaxel and bound to tubulin. Ellagic acid, its metabolite urolithin A, BRB extract, and the anthocyanin metabolite protocatechuic acid (PCA) did not alter cytotoxicity of taxanes. Ellagic acid inhibited drug efflux in CRPC cells, but BRB extract and PCA did not. None of these compounds altered CYP3A4 activity. Although dietary ellagic acid did not alter the tumor growth inhibition by docetaxel of xenografted 22Rv1 cells, ellagic acid has the potential to interfere with taxane chemotherapy by reducing tubulin polymerization while inhibiting P-glycoprotein drug efflux. These data are cause for concern of consuming ellagic acid during treatment for CRPC and indicate need for further research, but BRB consumption appears safe.

Combination of the natural product capsaicin and docetaxel synergistically kills human prostate cancer cells through the metabolic regulator AMP-activated kinase

Background

Current chemotherapy for castration-resistant prostate cancer is established on taxane-based compounds like docetaxel. However, eventually, the development of toxic side effects and resistance limits the therapeutic benefit being the major concern in the treatment of prostate cancer. Combination therapies in many cases, enhance drug efficacy and delay the appearance of undesired effects, representing an important option for the treatment of castration-resistant prostate cancer. In this study, we tested the efficacy of the combination of docetaxel and capsaicin, the pungent ingredient of hot chili peppers, on prostate cancer cells proliferation.

Methods

Prostate cancer LNCaP and PC3 cell lines were used in this study. Levels of total and phosphorylated forms of Akt, mTOR, S6, LKB1, AMPK and ACC were determined by Western blot. AMPK, LKB1 and Akt knock down was performed by siRNA. PTEN was overexpressed by transient transfection with plasmids. Xenograft prostate tumors were induced in nude mice and treatments (docetaxel and capsaicin) were administered intraperitoneally. Statistical analyses were performed with GraphPad software. Combination index was calculated with Compusyn software.

Results

Docetaxel and capsaicin synergistically inhibited the growth of LNCaP and PC3 cells, with a combination index lower than 1 for most of the combinations tested. Co-treatment with docetaxel and capsaicin notably decreased Akt and its downstream targets mTOR and S6 phosphorylation. Overexpression of PTEN phosphatase abrogated the synergistic antiproliferative effect of docetaxel and capsaicin. The combined treatment also increased the phosphorylation of AMP-activated kinase (AMPK) and the phosphorylation of its substrate ACC. In addition, pharmacological inhibition of AMPK with dorsomorphin (compound C) as well as knock down by siRNA of AMPK or its upstream kinase LKB1, abolished the synergy of docetaxel and capsaicin. Mechanistically, we showed that the synergistic anti-proliferative effect may be attributed to two independent effects: Inhibition of the PI3K/Akt/mTOR signaling pathway by one side, and AMPK activation by the other. In vivo experiments confirmed the synergistic effects of docetaxel and capsaicin in reducing the tumor growth of PC3 cells.

Conclusion

Combination of docetaxel and capsaicin represents a therapeutically relevant approach for the treatment of Prostate Cancer.

KIFC1 Inhibitor CW069 Induces Apoptosis and Reverses Resistance to Docetaxel in Prostate Cancer

Kinesin family member C1 (KIFC1) is a minus end-directed motor protein that plays an essential role in centrosome clustering. Previously, we reported that KIFC1 is involved in cancer progression in prostate cancer (PCa). We designed this study to assess the involvement of KIFC1 in docetaxel (DTX) resistance in PCa and examined the effect of KIFC1 on DTX resistance. We also analyzed the possible role of a KIFC1 inhibitor (CW069) in PCa. We used DTX-resistant PCa cell lines in DU145 and C4-2 cells to analyze the effect of KIFC1 on DTX resistance in PCa. Western blotting showed that KIFC1 expression was higher in the DTX-resistant cell lines than in the parental cell lines. Downregulation of KIFC1 re-sensitized the DTX-resistant cell lines to DTX treatment. CW069 treatment suppressed cell viability in both parental and DTX-resistant cell lines. DTX alone had little effect on cell viability in the DTX-resistant cells. However, the combination of DTX and CW069 significantly reduced cell viability in the DTX-resistant cells, indicating that CW069 re-sensitized the DTX-resistant cell lines to DTX treatment. These results suggest that a combination of CW069 and DTX could be a potential strategy to overcome DTX resistance.

Lack of combination effects of soy isoflavones and taxane chemotherapy of castration-resistant prostate cancer

BACKGROUND

Patients with cancer, including prostate cancer, often use dietary supplements, such as soy or isoflavones, before, during, or after therapy. There is little information about possible interactions between supplements and cancer chemotherapy. There are some reports suggesting enhancement by genistein of taxane chemotherapy for castrate-resistant prostate cancer (CRPC).

METHODS

We investigated whether physiologically attainable concentrations of soy isoflavones (≤10 μM) interact with taxanes on growth inhibition of CRPC cells in vitro and in vivo in nude mice exposed via the diet, on microtubule disassembly in vitro, and on P-glycoprotein-mediated drug efflux in 22Rv1 cells and CYP3A4 activity in microsomes.

RESULTS

Genistein, daidzein, and equol did not affect growth of VCaP, 22Rv1, C4-2, and PC-3 CRPC cells or growth inhibition of these cells by docetaxel and cabazitaxel. These isoflavones did not inhibit microtubule disassembly in vitro or inhibit the microtubule effects of taxanes and genistein did not bind substantially to microtubules. Genistein considerably inhibited P-glycoprotein-mediated drug efflux in 22Rv1 cells and CYP3A4 activity in microsomes. However, dietary supplementation with genistein at 250 and 500 ppm did not affect the tumor growth inhibiting effect of docetaxel on 22Rv1 cells xenografted in nude mice.

CONCLUSIONS

Our results with relevant cell models and clinically achievable concentrations of soy isoflavones do not support the notion that genistein or other soy isoflavones can enhance the effects of taxane chemotherapy in CRPC cell and xenograft models. Yet, the inhibitory effects of genistein on drug efflux in 22Rv1 cells and on microsomal CYP3A4 activity raise the possibility that genistein can affect taxane effects on CRPC cells in other circumstances than those we studied, which merits further research.

RNA sequencing reveals upregulation of a transcriptomic program associated with stemness in metastatic prostate cancer cells selected for taxane resistance

Patients with metastatic castration-resistant prostate cancer (mCRPC) develop resistance to conventional therapies including docetaxel (DTX). Identifying molecular pathways underlying DTX resistance is critical for developing novel combinatorial therapies to prevent or reverse this resistance. To identify transcriptomic signatures associated with acquisition of chemoresistance we profiled gene expression in DTX-sensitive and -resistant mCRPC cells using RNA sequencing (RNA-seq). PC3 and DU145 cells were selected for DTX resistance and this phenotype was validated by immunoblotting using DTX resistance markers (e.g. clusterin, ABCB1/P-gp, and LEDGF/p75). Overlapping genes differentially regulated in the DTX-sensitive and -resistant cells were ranked by Gene Set Enrichment Analysis (GSEA) and validated to correlate transcript with protein expression. GSEA revealed that genes associated with cancer stem cells (CSC) (e.g., NES, TSPAN8, DPPP, DNAJC12, and MYC) were highly ranked and comprised 70% of the top 25 genes differentially upregulated in the DTX-resistant cells. Established markers of epithelial-to-mesenchymal transition (EMT) and CSCs were used to evaluate the stemness of adherent DTX-resistant cells (2D cultures) and tumorspheres (3D cultures). Increased formation and frequency of cells expressing CSC markers were detected in DTX-resistant cells. DU145-DR cells showed a 2-fold increase in tumorsphere formation and increased DTX resistance compared to DU145-DR 2D cultures. These results demonstrate the induction of a transcriptomic program associated with stemness in mCRPC cells selected for DTX resistance, and strengthen the emerging body of evidence implicating CSCs in this process. In addition, they provide additional candidate genes and molecular pathways for potential therapeutic targeting to overcome DTX resistance.

Targeting the stress oncoprotein LEDGF/p75 to sensitize chemoresistant prostate cancer cells to taxanes

Prostate cancer (PCa) is associated with chronic prostate inflammation resulting in activation of stress and pro-survival pathways that contribute to disease progression and chemoresistance. The stress oncoprotein lens epithelium-derived growth factor p75 (LEDGF/p75), also known as DFS70 autoantigen, promotes cellular survival against environmental stressors, including oxidative stress, radiation, and cytotoxic drugs. Furthermore, LEDGF/p75 overexpression in PCa and other cancers has been associated with features of tumor aggressiveness, including resistance to cell death and chemotherapy. We report here that the endogenous levels of LEDGF/p75 are upregulated in metastatic castration resistant prostate cancer (mCRPC) cells selected for resistance to the taxane drug docetaxel (DTX). These cells also showed resistance to the taxanes cabazitaxel (CBZ) and paclitaxel (PTX), but not to the classical inducer of apoptosis TRAIL. Silencing LEDGF/p75 effectively sensitized taxane-resistant PC3 and DU145 cells to DTX and CBZ, as evidenced by a significant decrease in their clonogenic potential. While TRAIL induced apoptotic blebbing, caspase-3 processing, and apoptotic LEDGF/p75 cleavage, which leads to its inactivation, in both taxane-resistant and -sensitive PC3 and DU145 cells, treatment with DTX and CBZ failed to robustly induce these signature apoptotic events. These observations suggested that taxanes induce both caspase-dependent and -independent cell death in mCRPC cells, and that maintaining the structural integrity of LEDGF/p75 is critical for its role in promoting taxane-resistance. Our results further establish LEDGF/p75 as a stress oncoprotein that plays an important role in taxane-resistance in mCRPC cells, possibly by antagonizing drug-induced caspase-independent cell death.

Inhibiting G protein βγ signaling blocks prostate cancer progression and enhances the efficacy of paclitaxel

Aberrant activation of G protein-coupled receptors (GPCRs) is implicated in prostate cancer progression, but targeting them has been challenging because multiple GPCRs are involved in cancer progression. In this study, we tested the effect of blocking signaling via a hub through which multiple GPCRs converge — the G-protein Gβγ subunits. Inhibiting Gβγ signaling in several castration-resistant prostate cancer cell lines (i.e. PC3, DU145 and 22Rv1), impaired cell growth and migration in vitro, and halted tumor growth and metastasis in nude mice. The blockade of Gβγ signaling also diminished prostate cancer stem cell-like activities, by reducing tumorsphere formation in vitro and tumor formation in a limiting dilution assay in nude mice. Furthermore, Gβγ blockade enhanced the sensitivity of prostate cancer cells to paclitaxel treatment, both in vitro and in vivo. Together, our results identify a novel function of Gβγ in regulating prostate cancer stem-cell-like activities, and demonstrate that targeting Gβγ signaling is an effective approach in blocking prostate cancer progression and augmenting response to chemotherapy.

Emerging aspects of microRNA interaction with TMPRSS2-ERG and endocrine therapy

Prostate cancer (PCa) is the most common malignancy detected in males and the second most common cause of cancer death in western countries. The development of the prostate gland, is finely regulated by androgens which modulate also its growth and function. Importantly, androgens exert a major role in PCa formation and progression and one of the hypothesized mechanism proposed has been linked to the chromosomal rearrangement of the androgen regulated gene TMPRSS2 with ERG. Androgens have been therefore used as main target for therapies in the past. However, despite the development of endocrine therapies (e.g. androgen ablation), when PCa progress, tumors become resistant to this therapeutic castration and patients develop incurable metastases. A strategy to better understand how patients respond to therapy, in order to achieve a better patient stratification, consists in monitoring the levels of small noncoding RNAs (microRNAs). microRNAs are a class of small molecules that regulate protein abundance and their application as biomarkers to monitor disease progression has been intensely studied in the last years. In this review, we highlight the interactions between microRNAs and endocrine-related aspects of PCa in tissues. We focus on the modulation of TMPRSS2-ERG and Glucocorticoid Receptor (GR) by microRNAs and detail the influence of steroidal hormonal therapies on microRNAs expression.

Polymer micro/nanocarrier-assisted synergistic chemohormonal therapy for prostate cancer

Polymer micro/nanocarrier-assisted chemohormonal therapy upregulates chemotherapy efficacy and down-regulates hormone level, effectively inhibiting the progression of prostate cancer.

PrLZ increases prostate cancer docetaxel resistance by inhibiting LKB1/AMPK-mediated autophagy

Rationale: Docetaxel-mediated chemotherapy is the first-line standard approach and has been determined to show a survival advantage for metastatic castration-resistant prostate cancer (mCRPC) patients. However, a substantial proportion of patients eventually becomes refractory due to drug resistance. The detailed mechanisms remain unclear. We have previously reported that Prostate Leucine Zipper (PrLZ), a specific oncogene of prostate cancer (PCa), promotes PCa cell growth at the castration-resistant stage, thus suggesting a vital role of PrLZ in the progression of CRPC. In this study, we aimed to investigate the role of PrLZ in docetaxel resistance in PCa, focusing on PrLZ-regulating autophagy pathway.

Methods: Human PCa PC3, LNCaP and C4-2 cell lines were used as the model system in vitro and PCa xenografts and PrLZ-knockout mice were used as the model system in vivo. Docetaxel-induced cell death and apoptosis in PCa were determined by MTT and flow cytometry assay. The role of PrLZ on the regulation of autophagy and liver kinase B1/AMP-activated protein kinase (LKB1/AMPK) signaling pathway was analyzed using immunoblotting, immunoprecipitation, siRNA silencing and plasmid overexpression.

Results: PrLZ increased docetaxel-mediated drug resistance both in vitro and in vivo. Mechanistic dissection revealed that PrLZ interacted with LKB1 and further inhibited the activation of LKB1/AMPK signals, which negatively contributed to the induction of autophagy. Moreover, PrLZ/LKB1-mediated autophagy conferred resistance to docetaxel-induced cell death and apoptosis both in vitro and in vivo.

Conclusion: These findings identify a novel role of PrLZ in autophagy manipulation and provide new insight into docetaxel chemoresistance in PCa, suggesting a new strategy for treating mCRPC by targeting this newly identified signaling pathway.

Pharmacological treatment with inhibitors of nuclear export enhances the antitumor activity of docetaxel in human prostate cancer

Background and aims

Docetaxel (DTX) modestly increases patient survival of metastatic castration-resistant prostate cancer (mCRPC) due to insurgence of pharmacological resistance. Deregulation of Chromosome Region Maintenance (CRM-1)/ exportin-1 (XPO-1)-mediated nuclear export may play a crucial role in this phenomenon.

Material and methods

Here, we evaluated the effects of two Selective Inhibitor of Nuclear Export (SINE) compounds, selinexor (KPT-330) and KPT-251, in association with DTX by using 22rv1, PC3 and DU145 cell lines with their. DTX resistant derivatives.

Results and conclusions

We show that DTX resistance may involve overexpression of β-III tubulin (TUBB3) and P-glycoprotein as well as increased cytoplasmic accumulation of Foxo3a. Increased levels of XPO-1 were also observed in DTX resistant cells suggesting that SINE compounds may modulate DTX effectiveness in sensitive cells as well as restore the sensitivity to DTX in resistant ones. Pretreatment with SINE compounds, indeed, sensitized to DTX through increased tumor shrinkage and apoptosis by preventing DTX-induced cell cycle arrest. Basally SINE compounds induce FOXO3a activation and nuclear accumulation increasing the expression of FOXO-responsive genes including p21, p27 and Bim causing cell cycle arrest. SINE compounds-catenin and survivin supporting apoptosis. βdown-regulated Cyclin D1, c-myc, Nuclear sequestration of p-Foxo3a was able to reduce ABCB1 and TUBB3 H2AX levels, prolonged γ expression. Selinexor treatment increased DTX-mediated double strand breaks (DSB), and reduced the levels of DNA repairing proteins including DNA PKc and Topo2A. Our results provide supportive evidence for the therapeutic use of SINE compounds in combination with DTX suggesting their clinical use in mCRPC patients.

Combinatorial effect of curcumin with docetaxel modulates apoptotic and cell survival molecules in prostate cancer

Docetaxel is the most commonly used chemotherapeutic agent to target androgen signaling in metastatic prostate cancer (PCa); however, prolonged treatment with docetaxel results in drug-resistant cancer cells. Combination therapies have the potential of increasing the effectiveness of drug treatment as well as decreasing the side effects. Curcumin is a nontoxic organic compound with multifaceted chemopreventive potential. In this study, we evaluated whether curcumin can reinforce the effect of docetaxel on PCa cells. The PCa cell lines DU145 and PC3 were treated with curcumin and docetaxel alone or in combination. After completion of the treatment cell proliferation and the expression of pro-survival and anti-apoptotic markers and the signaling molecules were analyzed. The combined treatment of curcumin and docetaxel inhibited the proliferation and induced apoptosis significantly higher than the curcumin and docetaxel-treated group alone. Interestingly, the combined treatment with curcumin and docetaxel modulates the expression of RTKs, PI3K, phospho-AKT, NF-kappa B, p53, and COX-2. These results suggest that curcumin can be a potential therapeutic contender in enhancing the efficacy of docetaxel in PCa treatment.

CDK4/6 Therapeutic Intervention and Viable Alternative to Taxanes in CRPC

Resistance to second-generation androgen receptor (AR) antagonists and CYP17 inhibitors in patients with castration-resistant prostate cancer (CRPC) develops rapidly through reactivation of the androgen signaling axis and has been attributed to AR overexpression, production of constitutively active AR splice variants, or the selection for AR mutants with altered ligand-binding specificity. It has been established that androgens induce cell-cycle progression, in part, through upregulation of cyclin D1 (CCND1) expression and subsequent activation of cyclin-dependent kinases 4 and 6 (CDK4/6). Thus, the efficacy of the newly described CDK4/6 inhibitors (G1T28 and G1T38), docetaxel and enzalutamide, was evaluated as single agents in clinically relevant in vitro and in vivo models of hormone-sensitive and treatment-resistant prostate cancer. CDK4/6 inhibition (CDK4/6i) was as effective as docetaxel in animal models of treatment-resistant CRPC but exhibited significantly less toxicity. The in vivo effects were durable and importantly were observed in prostate cancer cells expressing wild-type AR, AR mutants, and those that have lost AR expression. CDK4/6i was also effective in prostate tumor models expressing the AR-V7 variant or the AR F876L mutation, both of which are associated with treatment resistance. Furthermore, CDK4/6i was effective in prostate cancer models where AR expression was lost. It is concluded that CDK4/6 inhibitors are a viable alternative to taxanes as therapeutic interventions in endocrine therapy-refractory CRPC.Implications: The preclinical efficacy of CDK4/6 monotherapy observed here suggests the need for near-term clinical studies of these agents in advanced prostate cancer. Mol Cancer Res; 15(6); 660-9. ©2017 AACR.