Cabazitaxel Resistance Research Articles

Overcoming ABCB1 mediated multidrug resistance in castration resistant prostate cancer

Prostate cancer (PCa) is the second leading cause of cancer-related death in American men. PCa that relapses after hormonal therapies, referred to as castration resistant PCa (CRPC), often presents with metastases (mCRPC) that are the major cause of mortality. The few available therapies for mCRPC patients include taxanes docetaxel (DTX) and cabazitaxel (CBZ). However, development of resistance limits their clinical use. Mechanistically, resistance arises through upregulation of multidrug resistance (MDR) proteins such as MDR1/ABCB1, making ABCB1 an attractive therapeutic target. Yet, ABCB1 inhibitors failed to be clinically useful due to low specificity and toxicity issues. To study taxanes resistance, we produced CBZ resistant C4-2B cells (RC4-2B) and documented resistance to both CBZ and DTX in cell culture and in 3D prostaspheres settings. RNAseq identified increased expression of ABCB1 in RC4-2B, that was confirmed by immunoblotting and immunofluorescent analysis. ABCB1-specific inhibitor elacridar reversed CBZ and DTX resistance in RC4-2B cells, confirming ABCB1-mediated resistance mechanism. In a cell-based screen using a curated library of cytotoxic drugs, we found that DNA damaging compounds Camptothecin (CPT) and Cytarabine (Ara-C) overcame resistance as seen by similar cytotoxicity in parental C4-2B and resistant RC4-2B. Further, these compounds were cytotoxic to multiple PC cells resistant to taxanes with high ABCB1 expression and, therefore, can be used to conquer the acquired resistance to taxanes in PCa. Finally, inhibition of cyclin-dependent kinases 4/6 (CDK4/6) with small molecule inhibitors (CDK4/6i) potentiated cytotoxic effect of CPT or Ara-C in both parental and resistant cells. Overall, our findings indicate that DNA damaging agents CPT and Ara-C alone or in combination with CDK4/6i can be suggested as a new treatment regimen in CRPC patients, including those that are resistant to taxanes.

Abstract 2302 Resisting Resistance: Developing Gemcitabine and Cabazitaxel Resistance in HL-60 Cells to Uncover Collateral Sensitivities in Acute Promyelocytic Leukemia

Abstract 2302 Resisting Resistance: Developing Gemcitabine and Cabazitaxel Resistance in HL-60 Cells to Uncover Collateral Sensitivities in Acute Promyelocytic Leukemia

G-protein signaling of oxytocin receptor as a potential target for cabazitaxel-resistant prostate cancer.

Although the treatment armamentarium for patients with metastatic prostate cancer has improved recently, treatment options after progression on cabazitaxel (CBZ) are limited. To identify the mechanisms underlying CBZ resistance and therapeutic targets, we performed single-cell RNA sequencing of circulating tumor cells (CTCs) from patients with CBZ-resistant prostate cancer. Cells were clustered based on gene expression profiles. In silico screening was used to nominate candidate drugs for overcoming CBZ resistance in castration-resistant prostate cancer. CTCs were divided into three to four clusters, reflecting intrapatient tumor heterogeneity in refractory prostate cancer. Pathway analysis revealed that clusters in two cases showed up-regulation of the oxytocin (OXT) receptor-signaling pathway. Spatial gene expression analysis of CBZ-resistant prostate cancer tissues confirmed the heterogeneous expression of OXT-signaling molecules. Cloperastine (CLO) had significant antitumor activity against CBZ-resistant prostate cancer cells. Mass spectrometric phosphoproteome analysis revealed the suppression of OXT signaling specific to CBZ-resistant models. These results support the potential of CLO as a candidate drug for overcoming CBZ-resistant prostate cancer via the inhibition of OXT signaling.

Berbamine targets cancer stem cells and reverses cabazitaxel resistance via inhibiting IGF2BP1 and p-STAT3 in prostate cancer.

Cancer stem cells (CSCs) are a small subpopulation of tumor cells with the capability of self-renewal and drug resistance, leading to tumor progression and disease relapse. Our study aimed to investigate the antitumor effect of berbamine, extracted from berberis amurensis, on prostate CSCs. Sphere formation was used to collect prostate CSCs. The viability, proliferation, invasion, migration, and apoptosis assays were used to evaluate the antitumor effect of berbamine on prostate CSCs. Prostate CSC markers were analyzed by flow cytometry and qRT-PCR. Small RNA sequencing analysis was conducted to analyse miRNAs. Exosomes were extracted using the ExoQuick-TC kit and verified by testing exosomal markers using western blot. Berbamine targets prostate CSCs. Additionally, berbamine enhanced the antitumor effect of cabazitaxel, a second-line chemotherapeutic drug for advanced prostate cancer, and re-sensitized Cabazitaxel-resistant PCa cells (CabaR-DU145) to cabazitaxel by inhibiting ABCG2, CXCR4, IGF2BP1, and p-STAT3. Berbamine enhanced the expression of let-7 miRNA family and miR-26b and influenced the downstream targets IGF2BP1 and p-STAT3, respectively. Silencing CXCR4 and ABCG2 downregulated the expression of IGF2BP1 and p-STAT3, respectively. Importantly, berbamine enhanced also levels of exosomal let-7 family and miR-26b, suggesting that berbamine possibly influences the expression of let-7 family and miR-26b through exosome delivery. Exosomes derived from berbamine-treated CabaR-DU145 cells re-sensitized the cells to cabazitaxel. Berbamine enhanced the toxic activity of cabazitaxel and reversed cabazitaxel resistance potentially through CXCR4/exosomal let-7/IGF2BP1 and ABCG2/exosomal miR-26b/p-STAT3 axes.

Investigation of enzalutamide, docetaxel, and cabazitaxel resistance in the castration resistant prostate cancer cell line C4 using genome-wide CRISPR/Cas9 screening

Enzalutamide, docetaxel, and cabazitaxel treatment resistance is a major problem in metastatic castration resistant prostate cancer (mCRPC), but the underlying genetic determinants are poorly understood. To identify genes that modulate treatment response to these drugs, we performed three genome-wide CRISPR/Cas9 knockout screens in the mCRPC cell line C4. The screens identified seven candidates for enzalutamide (BCL2L13, CEP135, E2F4, IP6K2, KDM6A, SMS, and XPO4), four candidates for docetaxel (DRG1, LMO7, NCOA2, and ZNF268), and nine candidates for cabazitaxel (ARHGAP11B, DRG1, FKBP5, FRYL, PRKAB1, RP2, SMPD2, TCEA2, and ZNF585B). We generated single-gene C4 knockout clones/populations for all genes and could validate effect on treatment response for five genes (IP6K2, XPO4, DRG1, PRKAB1, and RP2). Altered enzalutamide response upon IP6K2 and XPO4 knockout was associated with deregulation of AR, mTORC1, and E2F signaling, and deregulated p53 signaling (IP6K2 only) in C4 mCRPC cells. Our study highlights the necessity of performing individual validation of candidate hits from genome-wide CRISPR screens. Further studies are needed to assess the generalizability and translational potential of these findings.

Integrated analysis of single-cell and bulk RNA sequencing identifies a signature based on macrophage marker genes involved in prostate cancer prognosis and treatment responsiveness

In the tumor microenvironment, tumor-associated macrophages (TAMs) interact with cancer cells and contribute to the progression of solid tumors. Nonetheless, the clinical significance of TAM-related biomarkers in prostate cancer (PCa) is largely unexplored. The present study aimed to construct a macrophage-related signature (MRS) for predicting PCa patient prognosis based on macrophage marker genes. Six cohorts comprising 1056 PCa patients with RNA-Seq and follow-up data were enrolled. Based on macrophage marker genes identified by single-cell RNA-sequencing (scRNA-seq) analysis, univariate analysis, least absolute shrinkage and selection operator (Lasso)-Cox regression, and machine learning procedures were performed to derive a consensus MRS. Receiver operating characteristic curve (ROC), concordance index, and decision curve analyses were used to confirm the predictive capacity of the MRS. The predictive performance of the MRS for recurrence-free survival (RFS) was stable and robust, and the MRS outperformed traditional clinical variables. Furthermore, high-MRS-score patients presented abundant macrophage infiltration and high-expression levels of immune checkpoints (CTLA4, HAVCR2, and CD86). The frequency of mutations was relatively high in the high-MRS-score subgroup. However, the low-MRS-score patients had a better response to immune checkpoint blockade (ICB) and leuprolide-based adjuvant chemotherapy. Notably, abnormal ATF3 expression may be associated with docetaxel and cabazitaxel resistance in PCa cells, T stage, and the Gleason score. In this study, a novel MRS was first developed and validated to accurately predict patient survival outcomes, evaluate immune characteristics, infer therapeutic benefits, and provide an auxiliary tool for personalized therapy.

Efficacy of cabazitaxel and androgen splicing variant-7 status in circulating tumor cells in Asian patients with metastatic castration-resistant prostate cancer

Androgen receptor splice variant-7 (AR-V7) expression in circulating tumor cells (CTCs) in metastatic castration-resistant prostate cancer (mCRPC) is associated with abiraterone and enzalutamide resistance. We determine whether cabazitaxel (CBZ) is equally effective in AR-V7-positive and -negative CRPC and whether AR-V7-positive patients retain CBZ sensitivity. This is the first prospective, open-label, Asian validation study of CBZ in Japanese patients with mCRPC after docetaxel (n = 48; four CBZ cycles; 2017–2020, Juntendo University Hospitals). Primary endpoint was prostate-specific antigen response rate (PSA-RR); secondary endpoints included overall survival (OS), bone scan index (BSI) PSA-RR (≥ 50% decline from baseline) for CTC−/ARV7−, CTC+ /ARV7−, and CTC +/ARV7+ groups. PSA-RR ≥ − 30% was 38% (18/48) and ≥ − 50% was 26% (12/48). BSI-change rate ≥ − 30% was 19% (9/41) and ≥ − 50% was 17% (8/41). Median OS was 13.7(12.2–18.9) months. PSA decline in early CBZ treatment associated with OS (p = 0.00173). BSI decline associated with OS (p = 0.0194). PSA-RR(≥ 50%) was 43%(6/14) in CTC−/ARV7−, 19%(5/26) in CTC+ ARV7−, and 12%(1/8) in CTC+/ARV7+ ( p > 0.05). AR-V7 in CTCs at baseline not associated with OS. AR-V7 was not associated with CBZ resistance in CTCs. Reductions in BSI and PSA in early stages of CBZ treatment may predict OS.

Discovery of a new candidate drug to overcome cabazitaxel-resistant gene signature in castration-resistant prostate cancer by in silico screening

BackgroundThe taxane cabazitaxel (CBZ) is a promising treatment for docetaxel-resistant castration-resistant prostate cancer (CRPC). However, the survival benefit with CBZ for patients with CRPC is limited. This study used screening tests for candidate drugs targeting CBZ-resistant-related gene expression and identified pimozide as a potential candidate for overcoming CBZ resistance in CRPC.MethodsWe established CBZ-resistant cell lines, DU145CR and PC3CR by incubating DU145 cells and PC3 cells with gradually increasing concentrations of CBZ. We performed in silico drug screening for candidate drugs that could reprogram the gene expression signature of a CBZ-resistant prostate cancer cells using a Connectivity Map. The in vivo effect of the drug combination was tested in xenograft mice models.ResultsWe identified pimozide as a promising candidate drug for CBZ-resistant CRPC. Pimozide had a significant antitumor effect on DU145CR cells. Moreover, combination treatment with pimozide and CBZ had a synergic effect for DU145CR cells in vitro and in vivo. Microarray analysis identified AURKB and KIF20A as potential targets of pimozide in CBZ-resistant CRPC. DU145CR had significantly higher AURKB and KIF20A expression compared with a non-CBZ-resistant cell line. Inhibition of AURKB and KIF20A had an antitumor effect in DU145CR xenograft tumors. Higher expression of AURKB and KIF20A was a poor prognostic factor of TGCA prostate cancer cohort. CBZ-resistant prostate cancer tissues in our institution had higher AURKB and KIF20A expression.ConclusionsPimozide appears to be a promising drug to overcome CBZ resistance in CRPC by targeting AURKB and KIF20A.

Circulating Cell-Free DNA as Biomarker of Taxane Resistance in Metastatic Castration-Resistant Prostate Cancer.

Simple SummaryThere is a clinical need for biomarkers predictive of resistance to taxane therapy for patients with metastatic castration-resistant prostate cancer (mCRPC). Based on existing evidence for the role of ATP-binding cassette (ABC) transporters in taxane resistance, we sought to assess the association between ABCB1 gene amplification and primary resistance to docetaxel or cabazitaxel in mCRPC patients using sparse whole genome sequencing from plasma-derived cell-free DNA (cfDNA). Because sparse whole genome sequencing is more cost-effective than traditional cfDNA profiling and less invasive than tissue biopsies, a clinically useful biomarker of taxane resistance discovered using this technique has the potential to be broadly applied in clinical practice. We did not detect a statistically significant association between ABCB1 amplification detected by this method and docetaxel or cabazitaxel resistance in our cohort. Future studies with larger samples including ABCB1 amplification in a suite of putative biomarkers are warranted to draw definitive conclusions.There are no biomarkers predictive of resistance to docetaxel or cabazitaxel validated for patients with metastatic castration-resistant prostate cancer (mCRPC). We assessed the association between ABCB1 amplification and primary resistance to docetaxel or cabazitaxel for patients with mCRPC, using circulating cell-free DNA (cfDNA). Patients with ≥1 plasma sample drawn within 12 months before starting docetaxel (cohort A) or cabazitaxel (cohort B) for mCRPC were identified from the Dana–Farber Cancer Institute IRB approved database. Sparse whole genome sequencing was performed on the selected cfDNA samples and tumor fractions were estimated using the computational tool ichorCNA. We evaluated the association between ABCB1 amplification or other copy number alterations and primary resistance to docetaxel or cabazitaxel. Of the selected 176 patients, 45 samples in cohort A and 21 samples in cohort B had sufficient tumor content. No significant association was found between ABCB1 amplification and primary resistance to docetaxel (p = 0.58; odds ratio (OR) = 1.49) or cabazitaxel (p = 0.97; OR = 1.06). No significant association was found between exploratory biomarkers and primary resistance to docetaxel or cabazitaxel. In this study, ABCB1 amplification did not predict primary resistance to docetaxel or cabazitaxel for mCRPC. Future studies including ABCB1 amplification in a suite of putative biomarkers and a larger cohort may aid in drawing definitive conclusions.

Targeting Nrf2-antioxidant signalling reverses acquired cabazitaxel resistance in prostate cancer cells.

Prostate cancer is known to have a relatively good prognosis, but long-term hormone therapy can lead to castration-resistant prostate cancer (CRPC). Cabazitaxel, a second-generation taxane, has been used for the CRPC treatment, but its tolerance is an urgent problem to be solved. In this study, to elucidate the acquisition mechanism of the cabazitaxel-resistance, we established cabazitaxel-resistant prostate cancer 22Rv1 (Cab-R) cells, which exhibited ∼sevenfold higher LD50 against cabazitaxel than the parental 22Rv1 cells. Cab-R cells showed marked increases in nuclear accumulation of NF-E2 related factor 2 (Nrf2) and expression of Nrf2-inducible antioxidant enzymes compared to 22Rv1 cells, suggesting that Nrf2 signalling is homeostatically activated in Cab-R cells. The cabazitaxel sensitivity of Cab-R cells was enhanced by silencing of Nrf2, and that of 22Rv1 cells was reduced by activation of Nrf2. Halofuginone (HF) has been recently identified as a potent Nrf2 synthetic inhibitor, and its treatment of Cab-R cells not only suppressed the Nrf2 signalling by decreasing both nuclear and cytosolic Nrf2 protein levels, but also significantly augmented the cabazitaxel sensitivity. Thus, inhibition of Nrf2 signalling may be effective in overcoming the cabazitaxel resistance in prostate cancer cells.

YM155 Reverses Cabazitaxel Resistance in Castration-resistant Prostate Cancer by Reducing Survivin Expression.

The purpose of the present study was to clarify whether treatment with YM155, a novel small-molecule inhibitor of survivin, reversed cabazitaxel resistance in castration-resistant prostate cancer (CRPC). Cabazitaxel resistance was induced in the castration-resistant prostate cancer cell line, 22Rv1-CR. In vitro and in vivo models were used to test the efficacy of YM155 and cabazitaxel. Survivin gene expression was significantly higher in 22Rv1-CR than its parent cells (22Rv1). In 22Rv1-CR cells, YM155 significantly reduced expression of the survivin gene in a concentration-dependent manner. YM155 alone was poorly effective; however, it significantly enhanced the anticancer effects of cabazitaxel on 22Rv1-CR in vitro and in vivo. Inhibition of survivin by YM155 overcomes cabazitaxel resistance in CRPC cells.

LncRNA HORAS5 promotes taxane resistance in castration-resistant prostate cancer via a BCL2A1-dependent mechanism.

Background: Castration-resistant prostate cancer (CRPC) is an incurable malignancy. Long noncoding RNAs (lncRNAs) play key roles in drug resistance. Materials & methods: LncRNA HORAS5 role in cabazitaxel resistance (i.e., cell-count, IC50 and caspase activity) was studied via lentiviral-mediated overexpression and siRNA-based knockdown. Genes expression was analyzed with RNA-sequencing, reverse transcriptionquantitative PCR (RT-qPCR) and westernblot. HORAS5 expression was queried in clinical database. Results: Cabazitaxel increased HORAS5 expression that upregulated BCL2A1, thereby protecting CRPC cells from cabazitaxel-induced apoptosis. BCL2A1 knockdown decreased cell-count and increased apoptosis in CRPC cells. HORAS5-targeting antisense oligonucleotide decreased cabazitaxel IC50. In CRPC clinical samples, HORAS5 expression increased upon taxane treatment. Conclusion:HORAS5 stimulates the expression of BCL2A1 thereby decreasing apoptosis and enhancing cabazitaxel resistance in CRPC cells.

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

BackgroundDespite 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.MethodsDu145 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.ResultsWhile 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.ConclusionOur 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.

Abstract A34: Longitudinal analysis of personal DNA methylome patterns in metastatic prostate cancer

Abstract Background: Epigenetic modifications, in particular DNA methylation, are centrally involved in initiation and progression of prostate cancer (PCa). Yet, it is still unknown how these events unfold during acquired drug resistance in advanced PCa. One reason for this knowledge gap is the inherent difficulty in accessing metastatic tumor deposits for study. The advent of liquid biopsies has emerged as a useful method that allows to not only overcome the challenges of tissue biopsies but also to study tumor dynamics by use of serial sampling. The aim of this study is to understand how the methylome evolves over time, during clinical progression and acquired drug resistance in metastatic PCa (mPCa), on an individual level. Methods: 48 serial samples of peripheral blood plasma, taken at baseline and multiple therapeutic intervals, were collected from mPCa patients (n=9) involved in the iPROSPECT study. Samples were collected every 4 months and subjects were followed for 13-21 months. Cell-free DNA was isolated using the QIAamp Circulating Nucleic Acid kit. Epigenome-wide methylation measurements were performed with the Infinium® MethylationEPIC BeadChip. Raw data were preprocessed with minfi. QC was performed, with all 48 samples and 801,849 probes retained for analysis. To study differential methylation over time, the standard deviation (SD) was calculated for each probe longitudinally. Within each subject, the top 5% most variable probes were selected for further analysis. Probe patterns across time-points were compared using TSdist to identify congruent changes between probes. Gene ontology was performed with probes displaying similar patterns. Results: Evaluation of temporal variability in CpG methylation showed that most probes remained relatively stable (SD<0.1) across different treatments, indicating a low intrasubject variation in methylation of cfDNA. The top 5% most variable probes (n=40,092) in each subject were selected and filtered for 5’-regulatory probes. Analysis suggests coordinate dysregulation of DNA methylation at gene promoters, with specific patterns observed at clinically relevant time-points. For example, in one individual, de novo hypermethylation of GSTP1 with concurrent hypomethylation of the AR gene emerged at biochemical (PSA) evidence of cabazitaxel resistance. Work is ongoing to further identify coordinate epigenetic changes in cfDNA and the corresponding genes involved during disease progression and treatment resistance. Conclusions: Early analysis of this longitudinal study of mPCa patients, at an individual level, indicates correlation of dynamic methylation changes with clinical events. Further examination will determine the potential use of these specific molecular signatures in precision medicine. Citation Format: Romina Silva, Bruce Moran, William M. Gallagher, Donal J. Brennan, Antoinette S. Perry. Longitudinal analysis of personal DNA methylome patterns in metastatic prostate cancer [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr A34.

MP51-16 DECREASING SURVIVIN BY YM155 REVERSES CABAZITAXEL RESISTANCE IN PROSTATE CANCER

You have accessJournal of UrologyProstate Cancer: Basic Research & Pathophysiology II (MP51)1 Apr 2020MP51-16 DECREASING SURVIVIN BY YM155 REVERSES CABAZITAXEL RESISTANCE IN PROSTATE CANCER Takeshi Miyao*, Hidekazu Koike, Akira Otsu, Daisuke Oka, Masanori Aoki, Hiroshi Nakayama, Yoshiyuki Miyazawa, Seiji Arai, Yoshitaka Sekine, Hiroshi Matsui, Yasuhiro Shibata, and Kazuhiro Suzuki Takeshi Miyao*Takeshi Miyao* More articles by this author , Hidekazu KoikeHidekazu Koike More articles by this author , Akira OtsuAkira Otsu More articles by this author , Daisuke OkaDaisuke Oka More articles by this author , Masanori AokiMasanori Aoki More articles by this author , Hiroshi NakayamaHiroshi Nakayama More articles by this author , Yoshiyuki MiyazawaYoshiyuki Miyazawa More articles by this author , Seiji AraiSeiji Arai More articles by this author , Yoshitaka SekineYoshitaka Sekine More articles by this author , Hiroshi MatsuiHiroshi Matsui More articles by this author , Yasuhiro ShibataYasuhiro Shibata More articles by this author , and Kazuhiro SuzukiKazuhiro Suzuki More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000000913.016AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Cabazitaxel has exhibited promising anticancer activity for the treatment of prostate cancer. However, many patients acquire resistance to therapeutic agents leading to treatment failure. The objective of this study was to determine whether treatment with YM155, a novel small molecule inhibitor of survivin, could reverse Cabazitaxel resistance in a Cabazitaxel-resistant prostate cancer. METHODS: We induced a Cabazitaxel-resistant prostate cancer cell line (22Rv1-CR). We showed that survivin gene expression was significantly up-regulated in 22Rv1-CR compared with that in its parent cells (22Rv1). Therefore, we hypothesized that targeting of survivin in 22Rv1-CR could reverse the resistant phenotype in tumor cells, thereby enhancing the therapeutic efficacy of Cabazitaxel. We used both in vitro and in vivo models to test the efficacy of YM155 either as a single agent or in combination with Cabazitaxel. RESULTS: In 22Rv1-CR cells, YM155 significantly decreased survivin gene expression levels and cell proliferation in a dose-dependent manner in vitro. In addition, YM155 treatment significantly reversed Cabazitaxel resistance in 22Rv1-CR cells. In a nude mouse tumor xenograft model, YM155 significantly enhanced the antitumor effects of Cabazitaxel in 22Rv1-CR tumor. CONCLUSIONS: Our results suggest a potentially novel strategy to use YM155 to overcome the resistance in tumor cells, thereby enhancing the effectiveness of Cabazitaxel-therapy in prostate cancer. Source of Funding: none © 2020 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 203Issue Supplement 4April 2020Page: e770-e770 Advertisement Copyright & Permissions© 2020 by American Urological Association Education and Research, Inc.MetricsAuthor Information Takeshi Miyao* More articles by this author Hidekazu Koike More articles by this author Akira Otsu More articles by this author Daisuke Oka More articles by this author Masanori Aoki More articles by this author Hiroshi Nakayama More articles by this author Yoshiyuki Miyazawa More articles by this author Seiji Arai More articles by this author Yoshitaka Sekine More articles by this author Hiroshi Matsui More articles by this author Yasuhiro Shibata More articles by this author Kazuhiro Suzuki More articles by this author Expand All Advertisement PDF downloadLoading ...

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.

1949P - Cell plasticity and taxanes resistance in metastatic prostate cancer: ESRP1 as a predictive biomarker of taxane response

1949P - Cell plasticity and taxanes resistance in metastatic prostate cancer: ESRP1 as a predictive biomarker of taxane response

1986PD - HORAS5 promotes cabazitaxel resistance in castration resistant prostate cancer via a BCL2A1-dependent survival mechanism

BackgroundLong non-coding RNAs (lncRNAs) have been recently identified as key players in several cancer-associated pathways such as metastasis and drug resistance. Emerging evidence indicates that the HORAS5 lncRNA (i.e. linc00161) modulates drug response in different malignancies. In a recently published study, we have shown that HORAS5 promotes the survival of androgen receptor-positive (AR+) castration resistant prostate cancer (CRPC) cells. Preliminary data obtained in our lab show that HORAS5 is involved in response to cabazitaxel, in both AR+ and AR- CRPC cells. MethodsHORAS5 expression was modulated in AR+ and AR- CRPC cells with lentiviral-mediated overexpression and siRNA-based silencing. We measured cell count (Trypan Blue exclusion test) and apoptosis (caspase 3/7) of CRPC cells exposed to clinically achievable concentrations of cabazitaxel. RNA sequencing, RT-qPCR and western blot were used to identify genes regulated by HORAS5 in cabazitaxel-treated cells. We also transfected the cells with antisense oligonucleotides (ASOs), a technology that is currently being tested in clinical trials. ResultsOur results show that HORAS5 overexpression increases cabazitaxel IC50 (p=0.01), while HORAS5 silencing has an opposite effect (p=0.003). HORAS5 also inhibits caspase activity upon cabazitaxel treatment (p<0.0001). RNA sequencing and RT-qPCR revealed that BCL2A1 is the most upregulated transcript in HORAS5 overexpressing cells exposed to cabazitaxel (p<0.0001), and that BCL2A1 silencing decreases cell count (p<0.03) and increases caspase activity (p<0.0001). This evidence suggests that BCL2A1 expression is induced by HORAS5, thereby enhancing CRPC cells resistance to cabazitaxel. Transfection of CRPC cells with HORAS5-targeting ASOs can effectively silence this lncRNA (∼80% KD) and determine a decrease in the IC50 (p=0.03) in response to cabazitaxel. ConclusionsOur findings show that HORAS5 mediates cabazitaxel resistance in both AR+ and AR- CRPC cells via regulation of the anti-apoptotic BCL2A1. Experiments with ASOs demonstrate the translational potential of HORAS5 inhibition. We are currently assessing HORAS5 expression in biological fluids from patients exposed (or not) to cabazitaxel. Legal entity responsible for the studyFrancesco Crea. FundingThe Open University. DisclosureAll authors have declared no conflicts of interest.

TUBB3 Reverses Resistance to Docetaxel and Cabazitaxel in Prostate Cancer.

Recent studies have reported that TUBB3 overexpression is involved in docetaxel (DTX) resistance in prostate cancer (PCa). The aim of this study was to clarify the role of TUBB3 in DTX and cabazitaxel (CBZ) resistance, and cross-resistance between DTX and CBZ in PCa. We analyzed the effect of TUBB3 knockdown on DTX and CBZ resistance and examined the interaction between TUBB3 and PTEN. We also investigated the role of phosphoinositide 3-kinases (PI3K) inhibitor (LY294002) in DTX and CBZ resistance. TUBB3 expression was upregulated in DTX-resistant and CBZ-resistant cells. TUBB3 knockdown re-sensitized DTX-resistant cells to DTX and CBZ-resistant cells to CBZ. Additionally, TUBB3 knockdown re-sensitized DTX-resistant cell lines to CBZ, indicating that TUBB3 mediates cross-resistance between DTX and CBZ. Knockdown of TUBB3 enhanced PTEN expression, and PTEN knockout enhanced TUBB3 expression. LY294002 suppressed TUBB3 expression in DTX-resistant and CBZ-resistant cell lines. LY294002 re-sensitized DTX-resistant cell lines to DTX and CBZ-resistant cell lines to CBZ. These results suggest that TUBB3 is involved in DTX resistance and CBZ resistance. A combination of LY294002/DTX and that of LY294002/CBZ could be potential strategies for PCa treatment.

Suppressive Role of Androgen/Androgen Receptor Signaling via Chemokines on Prostate Cancer Cells.

Androgen/androgen receptor (AR) signaling is a significant driver of prostate cancer progression, therefore androgen-deprivation therapy (ADT) is often used as a standard form of treatment for advanced and metastatic prostate cancer patients. However, after several years of ADT, prostate cancer progresses to castration-resistant prostate cancer (CRPC). Androgen/AR signaling is still considered an important factor for prostate cancer cell survival following CRPC progression, while recent studies have reported dichotomic roles for androgen/AR signaling. Androgen/AR signaling increases prostate cancer cell proliferation, while simultaneously inhibiting migration. As a result, ADT can induce prostate cancer metastasis. Several C-C motif ligand (CCL)-receptor (CCR) axes are involved in cancer cell migration related to blockade of androgen/AR signaling. The CCL2-CCR2 axis is negatively regulated by androgen/AR signaling, with the CCL22-CCR4 axis acting as a further downstream mediator, both of which promote prostate cancer cell migration. Furthermore, the CCL5-CCR5 axis inhibits androgen/AR signaling as an upstream mediator. CCL4 is involved in prostate carcinogenesis through macrophage AR signaling, while the CCL21-CCR7 axis in prostate cancer cells is activated by tumor necrotic factor, which is secreted when androgen/AR signaling is inhibited. Finally, the CCL2-CCR2 axis has recently been demonstrated to be a key contributor to cabazitaxel resistance in CRPC.