Reactive oxygen species induction by cabazitaxel through inhibiting Sestrin-3 in castration resistant prostate cancer

Association between the apoptotic effect of Cabazitaxel and its pro-oxidant efficacy on the redox adaptation mechanisms in prostate cancer cells with different resistance phenotypes

Redox adaptation causes poor prognosis by adapting cancer cells to excessive oxidative stress. Previously, we introduced an oxidative stress-resistant metastatic prostate cancer (mPC) model (LNCaP-HPR) that redox adaptation reduced the effect of Cabazitaxel (Cab), the last taxane-derivative for metastatic castration-resistant PC (mCRPC). Whereas, we investigated for the first time whether there is an association between the altered apoptotic effect and pro-oxidant efficacy of Cab on the redox adaptation in PC cells with different phenotypes, including LNCaP mPC, LNCaP-HPR, C4-2 mCRPC, and RWPE-1 cells. Cab was shown pro-oxidant efficacy proportionally with the apoptotic effect, more prominent in the less aggressive LNCaP cells, by increasing the endogenous ROS, mitochondrial damage, and inhibiting nuclear ROS scavengers, p-Nrf2 and HIF-1α. However, the pro-oxidant and apoptotic effect was lower in the LNCaP-HPR and C4-2 cells, indicating that the drug sensitivity of the cells adapted to survive with more ROS was reduced via altered regulation of redox adaptation. Additionally, unlike LNCaP, Cab caused an increase in the p-NF-κB activation, suggesting that the p-NF-κB might accompany maintaining survival with the increased ROS in the aggressive PC cells. Moreover, the cytotoxic and apoptotic effects of Cab were less on RWPE-1 cells compared to LNCaP but were closer to those on the more aggressive LNCaP-HPR and C4-2 cells, except for the changing pro-oxidant effect of Cab. Consequently, this study indicates the variable pro-oxidant effects of Cab on redox-sensitive proteins, which could be a target for improving Cab's apoptotic effect more in aggressive PC cells.

PSMA-targeted combination brusatol and docetaxel nanotherapeutics for the treatment of prostate cancer

Active targeting to cancer involves exploiting specific interactions between receptors on the surface of cancer cells and targeting moieties conjugated to the surface of vectors such that site-specific delivery is achieved. Prostate specific membrane antigen (PSMA) has proved to be an excellent target for active targeting to prostate cancer. We report the synthesis and use of a PSMA-specific ligand (Glu-NH-CO-NH-Lys) for the site-specific delivery of brusatol- and docetaxel-loaded poly(lactide-co-glycolide) (PLGA) nanoparticles to prostate cancer. The PSMA targeting ligand covalently linked to PLGA-PEG3400 was blended with methoxyPEG-PLGA to prepare brusatol- and docetaxel-loaded nanoparticles with different surface densities of the targeting ligand. Flow cytometry was used to evaluate the impact of different surface densities of the PSMA targeting ligand in LNCaP prostate cancer cells at 15 min and 2 h. Cytotoxicity evaluations of the targeted nanoparticles reveal differences based on PSMA expression in PC-3 and LNCaP cells. In addition, levels of reactive oxygen species (ROS) were measured using the fluorescent indicator, H2DCFDA, by flow cytometry. PSMA-targeted nanoparticles loaded with docetaxel and brusatol showed increased ROS generation in LNCaP cells compared to PC-3 at different time points. Furthermore, the targeted nanoparticles were evaluated in male athymic BALB/c mice implanted with PSMA-producing LNCaP cell tumors. Evaluation of the percent relative tumor volume show that brusatol-containing nanoparticles show great promise in inhibiting tumor growth. Our data also suggest that the dual drug-loaded targeted nanoparticle platform improves the efficacy of docetaxel in male athymic BALB/c mice implanted with PSMA-producing LNCaP cell tumors.

Targeting prostate tumor low-molecular weight tyrosine phosphatase for oxidation-sensitizing therapy

Protein tyrosine phosphatases (PTPs) play major roles in cancer and are emerging as therapeutic targets. Recent reports suggest low-molecular weight PTP (LMPTP)-encoded by the ACP1 gene-is overexpressed in prostate tumors. We found ACP1 up-regulated in human prostate tumors and ACP1 expression inversely correlated with overall survival. Using CRISPR-Cas9-generated LMPTP knockout C4-2B and MyC-CaP cells, we identified LMPTP as a critical promoter of prostate cancer (PCa) growth and bone metastasis. Through metabolomics, we found that LMPTP promotes PCa cell glutathione synthesis by dephosphorylating glutathione synthetase on inhibitory Tyr270. PCa cells lacking LMPTP showed reduced glutathione, enhanced activation of eukaryotic initiation factor 2-mediated stress response, and enhanced reactive oxygen species after exposure to taxane drugs. LMPTP inhibition slowed primary and bone metastatic prostate tumor growth in mice. These findings reveal a role for LMPTP as a critical promoter of PCa growth and metastasis and validate LMPTP inhibition as a therapeutic strategy for treating PCa through sensitization to oxidative stress.

Association between the antioxidant properties of SESN proteins and anti-cancer therapies

Since the beginning of SESN protein development, they have attracted highly progressive attention due to their regulatory role in multiple signalling pathways. Through their antioxidant activity and autophagy regulation implication, they can function as powerful antioxidants to reduce oxidative stress in cells. SESN proteins received special attention in the field of regulation of reactive oxygen species level in the cell and its interplay with signalling pathways determining energy and nutrient homeostasis. Since perturbations in these pathways are implicated in cancer onset and development, SESNs might constitute potential novel therapeutic targets of broad interest. In this review, we discuss the impact of SESN proteins on anti-cancer therapy based on naturally occurring compounds and conventionally used drugs that influence oxidative stress and autophagy-induced cellular signalling pathways. The significant changes in reactive oxygen species level and nutrient status in cancer cells generate subsequent biological effect through the regulation of SESN-dependent pathways. Thus, SESN may serve as the key molecule for regulating anti-cancer drugs' induced cellular response.

2-Hydroxyoleic Acid as a Self-Assembly Inducer for Anti-Cancer Drug-Centered Nanoparticles

A potent nontoxic antitumor drug, 2-hydroxyoleic acid (6, 2OHOA) used for membrane lipid therapy, was selected as a self-assembly inducer due to its ability to form nanoparticles (NPs) in water. For this purpose, it was conjugated with a series of anticancer drugs through a disulfide-containing linker to enhance cell penetration and to secure drug release inside the cell. The antiproliferative evaluation of the synthesized NP formulations against three human tumor cell lines (biphasic mesothelioma MSTO-211H, colorectal adenocarcinoma HT-29, and glioblastoma LN-229) showed that nanoassemblies 16-22a,bNPs exhibit antiproliferative activity at micromolar and submicromolar concentrations. Furthermore, the ability of the disulfide-containing linker to promote cellular effects was confirmed for most nanoformulations. Finally, 17bNP induced intracellular ROS increase in glioblastoma LN-229 cells similarly to free drug 8, and such elevated production was decreased by pretreatment with the antioxidant N-acetylcysteine. Also, nanoformulations 18bNP and 21bNP confirmed the mechanism of action of the free drugs.

STEAP1 Knockdown Decreases the Sensitivity of Prostate Cancer Cells to Paclitaxel, Docetaxel and Cabazitaxel

The Six Transmembrane Epithelial Antigen of the Prostate 1 (STEAP1) protein has been indicated as an overexpressed oncoprotein in prostate cancer (PCa), associated with tumor progression and aggressiveness. Taxane-based antineoplastic drugs such as paclitaxel, docetaxel, or cabazitaxel, have been investigated in PCa treatment, namely for the development of combined therapies with the improvement of therapeutic effectiveness. This study aimed to evaluate the expression of STEAP1 in response to taxane-based drugs and assess whether the sensitivity of PCa cells to treatment with paclitaxel, docetaxel, or cabazitaxel may change when the STEAP1 gene is silenced. Thus, wild-type and STEAP1 knockdown LNCaP and C4-2B cells were exposed to paclitaxel, docetaxel or cabazitaxel, and STEAP1 expression, cell viability, and survival pathways were evaluated. The results obtained showed that STEAP1 knockdown or taxane-based drugs treatment significantly reduced the viability and survival of PCa cells. Relatively to the expression of proliferation markers and apoptosis regulators, LNCaP cells showed a reduced proliferation, whereas apoptosis was increased. However, the effect of paclitaxel, docetaxel, or cabazitaxel treatment was reversed when combined with STEAP1 knockdown. Besides, these chemotherapeutic drugs may stimulate the cell growth of PCa cells knocked down for STEAP1. In conclusion, this study demonstrated that STEAP1 expression levels might influence the response of PCa cells to chemotherapeutics drugs, indicating that the use of paclitaxel, docetaxel, or cabazitaxel may lead to harmful effects in PCa cells with decreased expression of STEAP1.

Knockdown of microRNA-214-3p Promotes Tumor Growth and Epithelial-Mesenchymal Transition in Prostate Cancer

Simple Summary

Prostate Cancer is the second leading cause of cancer-related deaths in the United States. In this study, we analyzed a molecule known as a microRNA, which regulates the expression of genes. microRNAs are involved in processes related to cancer onset and progression. Abnormal expression of microRNAs can promote prostate cancer. This study showed that knockdown of microRNA miR-214-3p enhanced the progression and of prostate cancer. In addition, miR-214 regulated the expression of many genes. These results are useful to better understand the function of miR-214-3p in prostate cancer and can be a useful target in the treatment of the disease.

Abstract

Abnormal expression of microRNA miR-214-3p (miR-214) is associated with multiple cancers. In this study, we assessed the effects of CRISPR/Cas9 mediated miR-214 depletion in prostate cancer (PCa) cells and the underlying mechanisms. Knockdown of miR-214 promoted PCa cell proliferation, invasion, migration, epithelial-mesenchymal transition (EMT), and increased resistance to anoikis, a key feature of PCa cells that undergo metastasis. The reintroduction of miR-214 in miR-214 knockdown cells reversed these effects and significantly suppressed cell proliferation, migration, and invasion. These in vitro studies are consistent with the role of miR-214 as a tumor suppressor. Moreover, miR-214 knockout increased tumor growth in PCa xenografts in nude mice supporting its anti-oncogenic role in PCa. Knockdown of miR-214 increased the expression of its target protein, Protein Tyrosine Kinase 6 (PTK6), a kinase shown to promote oncogenic signaling and tumorigenesis in PCa. In addition, miR-214 modulated EMT as exhibited by differential regulation of E-Cadherin, N-Cadherin, and Vimentin both in vitro and in vivo. RNA-seq analysis of miR-214 knockdown cells revealed altered gene expression related to PCa tumor growth pathways, including EMT and metastasis. Collectively, our findings reveal that miR-214 is a key regulator of PCa oncogenesis and is a potential novel therapeutic target for the treatment of the disease.

Topoisomerase II alpha inhibition can overcome taxane-resistant prostate cancer through DNA repair pathways

Cabazitaxel (CBZ) is approved for the treatment of docetaxel-resistant castration-resistant prostate cancer (CRPC). However, its efficacy against CRPC is limited, and there are no effective treatments for CBZ-resistant CRPC. This study explored the optimal treatment for CRPC in the post-cabazitaxel setting. PC3 (CBZ-sensitive) and PC3CR cells (CBZ-resistant) were used in this study. We performed in silico drug screening for candidate drugs that could reprogram the gene expression signature of PC3CR cells. The in vivo effect of the drug combination was tested in xenograft mice models. We identified etoposide (VP16) as a promising treatment candidate for CBZ-resistant CRPC. The WST assay revealed that VP16 had a significant antitumor effect on PC3CR cells. PC3CR cells exhibited significantly higher topoisomerase II alpha (TOP2A) expression than PC3 cells. Higher TOP2A expression was a poor prognostic factor in The Cancer Genome Atlas prostate cancer cohort. In the Fred Hutchinson Cancer Research Center dataset, docetaxel-exposed tissues and metastatic tumors had higher TOP2A expression. In addition, VP16 significantly inhibited the growth of tumors generated from both cell lines. Based on these findings, VP16-based chemotherapy may be an optimal treatment for CPRC in the post-CBZ setting.

DNA-PKc inhibition overcomes taxane resistance by promoting taxane-induced DNA damage in prostate cancer cells

BACKGROUND

Overcoming taxane resistance remains a major clinical challenge in metastatic castrate-resistant prostate cancer (mCRPC). Loss of DNA repair proteins is associated with resistance to anti-microtubule agents. We propose that alterations in DNA damage response (DDR) pathway contribute to taxane resistance, and identification of these alterations may provide a potential therapeutic target to resensitize docetaxel-refractory mCRPC to taxane-based therapy.

METHODS

Alterations in DDR gene expression in our prostate cancer cell line model of docetaxel-resistance (DU145-DxR) derived from DU-145 cells were determined by DDR pathway-specific polymerase chain reaction array and immunoblotting. The PRKDC gene encoding DNA-PKc (DNA-dependent protein kinase catalytic unit), was noted to be overexpressed and evaluated for its role in docetaxel resistance. Cell viability and clonogenic survival of docetaxel-treated DU145-DxR cells were assessed after pharmacologic inhibition of DNA-PKc with three different inhibitors-NU7441, LTURM34, and M3814. Response to second-line cytotoxic agents, cabazitaxel and etoposide upon DNA-PKc inhibition was also tested. The impact of DNA-PKc upregulation on DNA damage repair was evaluated by comet assay and analysis of double-strand breaks marker, γH2AX and Rad51. Lastly, DNA-PKc inhibitor's effect on MDR1 activity was assessed by rhodamine 123 efflux assay.

RESULTS

DDR pathway-specific gene profiling revealed significant upregulation of PRKDC and CDK7, and downregulation of MSH3 in DU145-DxR cells. Compared to parental DU145, DU145-DxR cells sustained significantly less DNA damage when exposed to etoposide and docetaxel. Pharmacologic inhibition of DNA-PKc, a component of NHEJ repair machinery, with all three inhibitors, significantly resensitized DU145-DxR cells to docetaxel. Furthermore, DNA-PKc inhibition also resensitized DU145-DxR to cabazitaxel and etoposide, which demonstrated cross-resistance. Inhibition of DNA-PKc led to increased DNA damage in etoposide- and docetaxel-treated DU145-DxR cells. Finally, DNA-PKc inhibition did not affect MDR1 activity, indicating that DNA-PKc inhibitors resensitized taxane-resistant cells via an MDR1-independent mechanism.

CONCLUSION

This study supports a role of DDR genes, particularly, DNA-PKc in promoting resistance to taxanes in mCRPC. Targeting prostatic DNA-PKc may provide a novel strategy to restore taxane sensitivity in taxane-refractory mCRPC.

Curcumin Targets Both Apoptosis and Necroptosis in Acidity-Tolerant Prostate Carcinoma Cells

Objective

Curcumin, a major bioactive curcuminoid derived from the rhizome of Curcuma longa, is known to have anticancer potential and is still under investigation. In this study, we investigated the cytotoxic mechanism(s) of curcumin against acidity-tolerant prostate cancer PC-3AcT cells in lactic acid-containing medium.

Methods

Using 2D-monolyer and 3D spheroid culture models, MTT assay, annexin V-PE binding assay, flow cytometric analysis, measurement of ATP content, and Western blot analysis were used for this study.

Results

At nontoxic concentrations in normal prostate epithelial RWPE-1 and HPrEC cells, curcumin led to strong cytotoxicity in PC-3AcT cells, including increases in sub-G₀/G₁ peak, annexin V-PE-positive cells, and ROS levels; loss of mitochondrial membrane potential; reduction of cellular ATP content; DNA damage; and concurrent induction of apoptosis and necroptosis. A series of changes induced by curcumin were effectively reversed by reducing ROS levels or replenishing ATP. Pretreatment with apoptosis inhibitor Q-VD-Oph-1 or necroptosis inhibitor necrostatin-1 restored cell viability inhibited by curcumin. Treatment of 3D spheroids with curcumin decreased cell viability, accompanied by an increase in mediators of apoptosis and necroptosis, including cleaved caspase-3 and cleaved PARP, phospho (p)-RIP3, and p-MLKL proteins.

Conclusion

This study shows that curcumin simultaneously induces apoptosis and necroptosis by oxidative mitochondrial dysfunction and subsequent ATP depletion, providing a mechanistic basis for understanding the novel role of curcumin for prostate carcinoma cells.

Targeting Nrf2-antioxidant signaling 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 approximately 7-fold 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 signaling 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 signaling by decreasing both nuclear and cytosolic Nrf2 protein levels, but also significantly augmented the cabazitaxel sensitivity. Thus, inhibition of Nrf2 signaling may be effective in overcoming the cabazitaxel resistance in prostate cancer cells.

LncRNA PAINT is associated with aggressive prostate cancer and dysregulation of cancer hallmark genes

Long noncoding RNAs (lncRNAs) play regulatory role in cellular processes and their aberrant expression may drive cancer progression. Here we report the function of a lncRNA PAINT (prostate cancer associated intergenic noncoding transcript) in promoting prostate cancer (PCa) progression. Upregulation of PAINT was noted in advanced stage and metastatic PCa. Inhibition of PAINT decreased cell proliferation, S-phase progression, increased expression of apoptotic markers, and improved sensitivity to docetaxel and Aurora kinase inhibitor VX-680. Inhibition of PAINT decreased cell migration and reduced expression of Slug and Vimentin. Ectopic expression of PAINT suppressed E-cadherin, increased S-phase progression and cell migration. PAINT expression in PCa cells induced larger colony formation, increased tumor growth and higher expression of mesenchymal markers. Transcriptome analysis followed by qRT-PCR validation showed differentially expressed genes involved in epithelial mesenchymal transition (EMT), apoptosis and drug resistance in PAINT-expressing cells. Our study establishes an oncogenic function of PAINT in PCa.

The regulatory effect of cabazitaxel on epithelial-mesenchymal transition in metastatic prostate cancer

Introduction

: Epithelial-mesenchymal transition (EMT) is a critical mechanism that promotes cancer cells to metastasis. Therefore, EMT regulation has become an important target in anticancer therapy approaches in recent years. However, in metastatic prostate cancer (PC), the EMT regulatory effect has not fully understood for cabazitaxel (Cbx), a third line taxane-based chemotherapeutic for metastatic castration-resistant PC.

Aim

In this study, we investigated the antimetastatic and EMT-regulatory effects of Cbx on hormone-sensitive metastatic PC cells.

Materials and Methods

The anticancer effects of Cbx were assessed by WST-1 and Annexin V analysis. The antimetastatic effect of Cbx was evaluated by wound healing and quantitative reverse transcription polymerase chain reaction through EMT-mesenchymal-to-epithelial transition (MET) markers as well as EMT-repressor microRNAs (miRNAs) in Cbx-treated LNCaP cells.

Results

Our results showed that, in addition to its apoptotic and anti-migratory activities, Cbx exhibited the EMT-repressor effects through the prominent downregulation of matrix metalloproteinase-9 and Snail levels as EMT-promoting factors, and the significant upregulation of the certain miRNAs, including miR-205, miR-524, and miR-124, which play a role in EMT-repressing by targeting regulators of the EMT-associated genes.

Conclusion

Although further evaluations are needed to improve the findings, we showed that, in addition to its classical taxane function, Cbx has a regulatory effect on EMT-MET cycling in hormone-sensitive metastatic PC.

New Small-Molecule Glycoconjugates of Docetaxel and GalNAc for Targeted Delivery to Hepatocellular Carcinoma

In this work, we have developed covalent and low molecular weight docetaxel delivery systems based on conjugation with N-acetyl-d-galactosamine and studied their properties related to hepatocellular carcinoma cells. The resulting glycoconjugates have an excellent affinity to the asialoglycoprotein receptor (ASGPR) in the nanomolar range of concentrations and a high cytotoxicity level comparable to docetaxel. Likewise, we observed the 21-75-fold increase in water solubility in comparison with parent docetaxel and prodrug lability to intracellular conditions with half-life values from 25.5 to 42 h. We also found that the trivalent conjugate possessed selective toxicity against hepatoma cells vs control cell lines (20-35 times). The absence of such selectivity in the case of monovalent conjugates indicates the effect of ligand valency. Specific ASGPR-mediated cellular uptake of conjugates was proved in vitro using fluorescent-labeled analogues. In addition, we showed an enhanced generation of reactive oxygen species in the HepG2 cells, which could be inhibited by the natural ligand of ASGPR. Overall, the obtained results highlight the potential of ASGPR-directed cytostatic taxane drugs for selective therapy of hepatocellular carcinoma.

Eprinomectin, a novel semi-synthetic macrocylic lactone is cytotoxic to PC3 metastatic prostate cancer cells via inducing apoptosis

Prostate Cancer (PCa) is the second most common cancer among men in United States after skin cancer. Conventional chemotherapeutic drugs available for PCa treatment are limited due to toxicity and resistance issues. Therefore, there is an urgent need to develop more effective treatment for advanced PCa. In this current study, we focused on evaluating the anti-cancer efficacy of Eprinomectin (EP), a novel avermectin analog against PC3 metastatic PCa cells. EP displayed robust inhibition of cell viability of PC3 cells in addition to suppressing the colony formation and wound healing capabilities. Our study showed that EP targets PC3 cells via inducing ROS and apoptosis activation. EP treatment enforces cell cycle arrest at G0/G1 phase via targeting cyclin-dependent kinase 4 (CDK4) and subsequent induction of apoptosis in PC3 cells. At the molecular level, EP effectively inhibited the expression of various cancer stem cell markers such as ALDH1, Sox-2, Nanog, Oct3/4 and CD44. Interestingly, EP also inhibited the activity of alkaline phosphatase, a maker of pluripotent stem cells. Of note, EP treatment resulted in the translocation of β-catenin from the nucleus to the cytoplasm indicating that EP antagonizes Wnt/β-catenin signaling pathway. Western blotting analysis revealed that EP downregulated the expression of key cell cycle markers such as cyclin D1, cyclin D3, CDK4, and c-Myc. In addition, EP inhibited the anti-apoptotic markers such as Mcl-1, XIAP, c-IAP1 and survivin in PC3 cells. On the other hand, EP treatment resulted in the activation of pH2A.X, Bad, caspase-9, caspase-3 and cleavage of PARP1. Taken together, our data suggests that EP is a potential agent to treat advanced PCa cells via modulating apoptosis signaling.

Overexpression of SLC6A1 associates with drug resistance and poor prognosis in prostate cancer

Background

Solute Carrier Family 6 Member 1 (SLC6A1) has been identified as a cancer-promoting gene in various human cancers, such as clear cell renal cell carcinoma and ovarian cancer. However, its roles in prostate cancer (PCa) has not been fully elucidated. The aim of this study was to investigate the expression and clinical significance of SLC6A1 in PCa tissues and its effect on drug resistance to docetaxel in PCa.

Methods

Expression patterns of SLC6A1 protein in PCa tissues were examined by immunohistochemistry based on Tissue microarray. Associations of SLC6A1 protein expression with various clinicopathological features and patients’ prognosis of PCa were also statistically evaluated based on TCGA data. Roles of SLC6A1 deregulation in prostate carcinogenesis and drug resistance was further determined in vitro and in vivo experiments.

Results

Based on TCGA Dataset, SLC6A1 expression was markedly higher in patients with high Gleason score, advanced clinical stage and positive biochemical recurrence than those with control features (all P < 0.05). Both unvariate and multivariate analyses demonstrated that SLC6A1 expression was significantly associated with biochemical recurrence-free survival in PCa patients. In addition, enforced expression of SLC6A1 effectively promoted cell proliferation, migration and invasion of PCa cells in vitro. Moreover, the inhibition of SLC6A1 suppressed the tumor growth in vivo. Additionally, immunohistochemical notches of PCNA and MMP-9 in the low-expression cluster were pointedly lower compared to those of NC group. Finally, the cell viability revealed that the overexpression of SLC6A1 obviously promoted the PCa cell resistant to docetaxel (DTX), and the transplanted tumor in the overexpression group had no significant reduction compared with the untreated group.

Conclusions

Our data suggest that SLC6A1 overexpression may be associated with aggressive progression and short biochemical recurrence-free survival of PCa, and may be related to the resistance to docetaxel therapy.

The function of miR-200 family in oxidative stress response evoked in cancer chemotherapy and radiotherapy

Since the beginning of the discovery of microRNAs (miRs), these molecules have attracted highly progressive attention due to their powerful regulatory roles in a broad spectrum of biological processes, including proliferation, differentiation, apoptosis and carcinogenesis. With regard to carcinogenesis, the miRs regulatory potency has been associated with cancer onset, progression, metastasis, diagnosis and therapeutic response. In this review we discuss the impact of miR-200 family on drug resistance development during anti-cancer therapy. Developing resistance to chemotherapeutic drugs as well as radiotherapy are major clinical obstacles in the successful therapeutic strategies to cancer treatment. Acquired cancer chemoresistance is a multifactorial phenomenon involving such factors as tumor type, tumor stage, cellular reactive oxygen species (ROS) level or ROS-responsive miRs profile. ROS level could influence the miRs expression level, which changes the cellular profile of the content of miRs. Such significant changes in the cellular miRs profile generate subsequent biological effects through the regulation of their target genes. This review outlines the interactions between ROS and miR-200 family in different kinds of cancers in response to chemotherapy.

Targeting Wnt/EZH2/microRNA-708 signaling pathway inhibits neuroendocrine differentiation in prostate cancer

Prostate cancer (PC) castration resistance has been linked to the differentiation of PC luminal cells into hormone-refractory neuroendocrine (NE) cells. However, the molecular mechanisms controlling the emergence of lethal NE prostate cancer (NEPC) remain unclear. The present study aimed to investigate the mechanisms underlying the transition from prostate adenocarcinoma to NEPC. The microRNA miR-708 was involved in NE differentiation and was downregulated in NEPC cells and tumor specimens. miR-708 targeted Sestrin-3 to inhibit Forkhead Box O1 (FOXO1) phosphorylation, resulting in apoptosis of prostate adenocarcinoma cells and AKT-inactivated NEPC cells, the latter of which was consistent with the progression of tumor xenografts in mice under miR-708 treatment. In silico analysis of PC and NEPC tumor specimens suggested that the polycomb repressive complex subunit Enhancer of zeste homolog 2 (EZH2) was particularly overexpressed in NEPC. Notably, EZH2 bound to the miR-708 promoter and induced its silencing in NEPC. Inhibition of EZH2 prevented NE differentiation of PC cells. EZH2 expression was regulated by both Cyclin Dependent Kinase 1 (CDK1) and Wnt signaling. Silencing transcription factor 4 (TCF4), as a key protein in Wnt signaling, prevented NEPC formation. These results provide a molecular basis for the roles of miR-708 and EZH2 in NE differentiation in PC and highlight a new paradigm in NEPC formation and survival.

Sestrins as a Therapeutic Bridge between ROS and Autophagy in Cancer

The regulation of Reactive Oxygen Species (ROS) levels and the contribution therein from networks regulating cell metabolism, such as autophagy and the mTOR-dependent nutrient-sensing pathway, constitute major targets for selective therapeutic intervention against several types of tumors, due to their extensive rewiring in cancer cells as compared to healthy cells. Here, we discuss the sestrin family of proteins—homeostatic transducers of oxidative stress, and drivers of antioxidant and metabolic adaptation—as emerging targets for pharmacological intervention. These adaptive regulators lie at the intersection of those two priority nodes of interest in antitumor intervention—ROS control and the regulation of cell metabolism and autophagy—therefore, they hold the potential not only for the development of completely novel compounds, but also for leveraging on synergistic strategies with current options for tumor therapy and classification/stadiation to achieve personalized medicine.

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.

Interactions between microRNA-200 family and Sestrin proteins in endometrial cancer cell lines and their significance to anoikis

In the present study, we intend to determine whether Sestrin proteins 1, 2, and 3 (SESN1-3) are targets of microRNA-200 family (miR-200) in endometrial cancer (EC) Ishikawa, AN3CA, KLE, and RL 95-2 cell lines and to investigate how these potential interactions influence anoikis resistance of EC cell lines. The luciferase reporter assay, qRT-PCR, and western blotting assays were used to verify whether SESN1-3 are direct targets of miR-200. Moreover, the anoikis assay and transient transfections of miR-200 mimics or inhibitors into EC cell lines were performed to evaluate the modulatory role of miR-200 and SESN proteins on anoikis resistance. We demonstrated that SESN2 protein is a direct target of mir-141 in KLE and RL-95-2 EC cell lines and the functional interaction of miR-141 and SESN2 protein has a downstream effect on anoikis resistance and SESN2 expression level in Ishikawa and AN3CA cell lines. Moreover, we have shown that SESN3 protein is a direct target of miR-200b, miR-200c, and miR-429 in Ishikawa, AN3CA, and KLE cell lines. Our results show that manipulation of miR-200b, miR-200c, and miR-429 expression patterns also has an influence on anoikis resistance in EC cell lines. In conclusion, we identified new interactions between miR-200 and the oxidative stress response SESN proteins that affect anoikis resistance in human EC cells.

No significant impact of patient age and prior treatment profile with docetaxel on the efficacy of cabazitaxel in patient with castration-resistant prostate cancer

BACKGROUND

The correlation of the oncological outcomes of docetaxel and cabazitaxel in Japanese metastatic castration-resistant prostate cancer (mCRPC) patients has not been unclear.

MATERIALS AND METHODS

This study included a total of 47 consecutive Japanese mCRPC patients treated with cabazitaxel and assessed the prognostic significance of cabazitaxel, focusing on patient age and the correlation of efficacy between docetaxel and cabazitaxel.

RESULTS

Prostate-specific antigen (PSA) decline was observed in 27 patients (57.4%), including 19 (40.0%) achieving the response defined by PSA decline ≥ 30%. The median overall survival (OS) periods after the introduction of cabazitaxel was 16.1 months. Twenty (42.6%) were judged to have responded to cabazitaxel with a PSA decrease ≥ 30% from the baseline. A 30% PSA response to cabazitaxel was achieved in 4 (50.0%) patients with ≧ 75 years (n = 8) and 16 (41.0%) patients with less than 75 years (n = 39). There was no significant correlation between the PSA response and patients' age (p = 0.707). A 30% PSA response to cabazitaxel was achieved in 13 (46.4%) and 7 (36.8%) patients with and without that to docetaxel, respectively. A 30% PSA response to cabazitaxel was achieved in 5 (16.6%) and 7 (41.2%) patients who had treated with less than 10 cycles docetaxel or 10 ≦ cycles, respectively. Univariate and multivariate analyses revealed that there were no significant correlation of patient age (p = 0.537), the response to prior docetaxel therapy (p = 0.339) or cycles of docetaxel therapy (p = 0.379) with shorter OS.

CONCLUSION

These results indicate that the introduction of cabazitaxel for Japanese mCRPC patients could result in oncological outcomes without any association with patient's age and the profiles of previous docetaxel therapy.

Analysis of cabazitaxel-resistant mechanism in human castration-resistant prostate cancer

Cabazitaxel (CBZ) is approved for docetaxel‐resistant castration‐resistant prostate cancer (CRPC). However, efficacy of CBZ for CRPC is limited and there are no effective treatments for CBZ‐resistant CRPC. In order to investigate the CBZ‐resistant mechanism, the establishment of a CBZ‐resistant cell line is urgently needed. We established CBZ‐resistant CRPC cell lines DU145CR and PC3CR by incubating DU145 and PC3 cells with gradually increasing concentrations of CBZ for approximately 2 years. We analyzed the gene expression profiles and cell cycle changes using microarray and flow cytometry. Pathway analysis revealed DU145CR cells had enhanced gene clusters of cell division and mitotic nuclear division. Enhancement of ERK signaling was detected in DU145CR cells. DU145CR cells had resistance to G₂/M arrest induced by CBZ through ERK signaling activation. The MEK inhibitor PD184352 significantly inhibited cell proliferation of DU145CR. In contrast to DU145CR, PC3CR cells had enhancement of PI3K/AKT signaling. The PI3K/mTOR inhibitor NVP‐BEZ 235 had a significant antitumor effect in PC3CR cells. Cabazitaxel ‐resistant CRPC cells established in our laboratory had enhancement of cell cycle progression signals and resistance to G₂/M arrest induced by CBZ. Enhancement of ERK signaling or PI3K/AKT signaling were detected in the cell lines, so ERK or PI3K/AKT could be therapeutic targets for CBZ‐resistant CRPC.

Hypoxia and Noncoding RNAs in Taxane Resistance

Taxanes are chemotherapeutic drugs employed in the clinic to treat a variety of malignancies. Despite their overall efficacy, cancer cells often display resistance to taxanes. Therefore, new strategies to increase the effectiveness of taxane-based chemotherapeutics are urgently needed. Multiple molecular players are linked to taxane resistance; these include efflux pumps, DNA repair mechanisms, and hypoxia-related pathways. In addition, emerging evidence indicates that both non-coding RNAs and epigenetic effectors might also be implicated in taxane resistance. Here we focus on the causes of taxane resistance, with the aim to envisage an integrated model of the 'taxane resistance phenome'. This model could help the development of novel therapeutic strategies to treat taxane-resistant neoplasms.

Establishment and characterization of two cabazitaxel-resistant prostate cancer cell lines

Once castration-resistant prostate cancer (CRPC) become resistant for cabazitaxel treatment, the patients are obliged to best supportive care. Therefore, the elucidation of the mechanism of the cabazitaxel-resistance and the conquest are important themes to improve the prognosis of the patients. Then we tried to establish cabazitaxel-resistant CRPC cell lines and characterized them. We established two cabazitaxel-resistant cell lines, PC-3-TxR/CxR and DU145-TxR/CxR from PC-3-TxR and DU145-TxR cell lines previously we established. PC-3-TxR/CxR and DU145-TxR/CxR cells became resistant for cabazitaxel by 11.8-fold and 4.4-fold, respectively. The TxR/CxR cells showed cabazitaxel-resistant using SCID mice in vivo. Although expression of multi-drug resistance gene 1 (MDR1) was up-regulated in DU145-TxR compared with DU145 cells, it was not up-regulated in DU145-TxR/CxR cells any more. In contrast, expression of MDR1 gene was up-regulated in PC-3-TxR compared with PC-3 cells and it was further up-regulated in PC-3-TxR/CxR compared with PC-3-TxR cells. Comparison of cDNA microarray between PC-3-TxR and PC-3-TxR/CxR cells or between DU145-TxR and DU145-TxR/CxR cells revealed that many genes were up-regulated or down-regulated. Finally, knockdown of MDR1 recovered the sensitivity to cabazitaxel not only in PC-3-TxR/CxR cells but also DU145-TxR/CxR cells. Together, regulation of MDR1 gene is important for conquest of the cabazitaxel-resistance.