Modulation of docetaxel-induced apoptosis and cell cycle arrest by all- trans retinoic acid in prostate cancer cells

Docetaxel radiosensitizes castration-resistant prostate cancer by downregulating CAV-1

PURPOSE

Docetaxel (DXL), a noted radiosensitizer, is one of the few chemotherapy drugs approved for castration-resistant prostate cancer (CRPC), though only a fraction of CRPCs respond to it. CAV-1, a critical regulator of radioresistance, has been known to modulate DXL and radiation effects. Combining DXL with radiotherapy may create a synergistic anticancer effect through CAV-1 and improve CRPC patients' response to therapy. Here, we investigate the effectiveness and molecular characteristics of DXL and radiation combination therapy in vitro.

MATERIALS AND METHODS

We used live/dead assays to determine the IC50 of DXL for PC3, DU-145, and TRAMP-C1 cells. Colony formation assay was used to determine the radioresponse of the same cells treated with radiation with/without IC50 DXL (4, 8, and 12 Gy). We performed gene expression analysis on public transcriptomic data collected from human-derived prostate cancer cell lines (C4-2, PC3, DU-145, and LNCaP) treated with DXL for 8, 16, and 72 hours. Cell cycle arrest and protein expression were assessed using flow cytometry and western blot, respectively.

RESULTS

Compared to radiation alone, combination therapy with DXL significantly increased CRPC death in PC3 (1.48-fold, p < .0001), DU-145 (1.64-fold, p < .05), and TRAMP-C1 (1.13-fold, p < .05) at 4 Gy of radiation. Gene expression of CRPC treated with DXL revealed downregulated genes related to cell cycle regulation and upregulated genes related to immune activation and oxidative stress. Confirming the results, G2/M cell cycle arrest was significantly increased after treatment with DXL and radiation. CAV-1 protein expression was decreased after DXL treatment in a dose-dependent manner; furthermore, CAV-1 copy number was strongly associated with poor response to therapy in CRPC patients.

CONCLUSIONS

Our results suggest that DXL sensitizes CRPC cells to radiation by downregulating CAV-1. DXL + radiation combination therapy may be effective at treating CRPC, especially subtypes associated with high CAV-1 expression, and should be studied further.

Functional inhibition of the RNA-binding protein HuR sensitizes triple-negative breast cancer to chemotherapy

Chemotherapy remains the standard treatment for triple-negative breast cancer (TNBC); however, chemoresistance compromises its efficacy. The RNA-binding protein Hu antigen R (HuR) could be a potential therapeutic target to enhance the chemotherapy efficacy. HuR is known to mainly stabilize its target mRNAs, and/or promote the translation of encoded proteins, which are implicated in multiple cancer hallmarks, including chemoresistance. In this study, a docetaxel-resistant cell subline (231-TR) was established from the human TNBC cell line MDA-MB-231. Both the parental and resistant cell lines exhibited similar sensitivity to the small molecule functional inhibitor of HuR, KH-3. Docetaxel and KH-3 combination therapy synergistically inhibited cell proliferation in TNBC cells and tumor growth in three animal models. KH-3 downregulated the expression levels of HuR targets (e.g., β-Catenin and BCL2) in a time- and dose-dependent manner. Moreover, KH-3 restored docetaxel's effects on activating Caspase-3 and cleaving PARP in 231-TR cells, induced apoptotic cell death, and caused S-phase cell cycle arrest. Together, our findings suggest that HuR is a critical mediator of docetaxel resistance and provide a rationale for combining HuR inhibitors and chemotherapeutic agents to enhance chemotherapy efficacy.

Nanoencapsulation of Docetaxel Induces Concurrent Apoptosis and Necroptosis in Human Oral Cancer Cells (SCC-9) via TNF-α/RIP1/RIP3 Pathway

Human oral squamous cell carcinoma is the sixth most frequent malignant cancer, with an unacceptably high death rate that affects people's health. Albeit, there are several clinical approaches for diagnosing and treating oral cancer they are still far from ideal. We previously synthesised and characterised the docetaxel nanoformulation (PLGA-Dtx) and discovered that docetaxel nanoencapsulation may suppress oral cancer cells. The goal of this study was to figure out the mechanism involved in the suppression of oral cancer cell proliferation. We discovered that PLGA-Dtx inhibited SCC-9 cell growth considerably as compared to free docetaxel (Dtx), and that the viability of SCC-9 cells treated with PLGA-Dtx was decreased dose-dependently. MTT assay showed that PLGA-Dtx selectively inhibited the growth of PBMCs from oral cancer patients while sparing PBMCs from normal healthy controls. Further, flow cytometry analysis showed that PLGA-Dtx induced apoptosis and necroptosis in SCC-9 cells. G2/M cell cycle arrest has been confirmed on exposure of PLGA-Dtx for 24 h in SCC-9 cells. Interestingly, western blot investigation found that PLGA-Dtx increased the amounts of necroptic proteins and apoptosis-related proteins more efficiently than Dtx. Furthermore, PLGA-Dtx was more effective in terms of ROS generation, and mitochondrial membrane potential depletion. Pretreatment with necroptosis inhibitor Nec-1 efficiently reversed the ROS production and further recover MMP caused by PLGA-Dtx. Overall, this study revealed a mechanistic model of therapeutic response for PLGA-Dtx in SCC-9 cells and proposed its potency by inducing cell death via activation of concurrent apoptosis and necroptosis in SCC-9 cells via TNF-α/RIP1/RIP3 and caspase-dependent pathway.

Prognostic value of tumor mutation burden in patients with advanced gastric cancer receiving first-line chemotherapy

Background

Tumor mutation burden (TMB) is a promising biomarker positively associated with the benefit of immunotherapy and that might predict the outcome of chemotherapy. We described the prognostic value of TMB in advanced gastric cancer and explored the underlying mechanism.

Methods

We enrolled 155 TMB-evaluated advanced gastric cancer patients and analyzed the relationship between clinicopathological characteristics and both overall survival (OS) and progression-free survival (PFS) among 40 patients treated with first-line chemotherapy. We further verified the distribution of TMB and analyzed the potential mechanism underlying the prognosis based on The Cancer Genome Atlas (TCGA) database.

Results

Among the 155 patients, 29 (18.7%) were TMB-high (TMB ≥ 10), roughly the same as the proportion in the TCGA data. Of the 40 patients receiving first-line chemotherapy, the median OS (7.9 vs. 12.1 months; HR 3.18; p = 0.0056) and PFS (4.4 vs. 6.2 months; HR 2.94; p = 0.0099) of the tissue-tested TMB (tTMB)-high patients were inferior to those of the tTMB-low patients. Similarly, unfavorable median OS (9.9 vs. 12.1 months; HR 2.11; p = 0.028) and PFS (5.3 vs. 6.5 months; HR 2.49; p = 0.0054) were shown in the blood-tested TMB (bTMB)-high than in the bTMB-low patients. The Cox analysis demonstrated that both tTMB-high and bTMB-high were significant independent predictors of dreadful OS and PFS. The differentially expressed genes (DEGs) according to TMB status were most significantly enriched in the downregulated metabolic pathway among the TMB-high patients.

Conclusions

TMB-high advanced gastric cancer patients accounted for around one-sixth and had a poorer prognosis than TMB-low patients when treated with first-line chemotherapy. The potential mechanism might be the downregulated metabolic activity in TMB-high patients.

CKD-516 potentiates the anti-cancer activity of docetaxel against epidermal growth factor receptor tyrosine kinase inhibitor-resistant lung cancer

Lung cancer is the leading cause of cancer death. Although docetaxel has been used as a second- or third-line treatment for non-small cell lung cancer (NSCLC), the objective response rate is less than 10%. Hence, there is a need to improve the clinical efficacy of docetaxel monotherapy; combination therapy should be considered. Here, we show that CKD-516, a vascular disruption agent, can be combined with docetaxel to treat epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI)-resistant NSCLC. CKD-516 was orally bioavailable; neither CKD-516 nor docetaxel affected the mean plasma concentration-time profile or pharmacokinetic parameters of the other drug. CKD-516 and docetaxel synergistically inhibited the growth of H1975 (with an L858R/T790M double mutation of EGFR) and A549 (with a KRAS mutation) lung cancer cell lines. In addition, docetaxel plus CKD-516 delayed tumor growth in-and extended the lifespan of-tumor-bearing mice. Thus, combination CKD-516 and docetaxel therapy could be used to treat EGFR-TKI-resistant NSCLC.

Proteomic characterization of gastric cancer response to chemotherapy and targeted therapy reveals new therapeutic strategies

Chemotherapy and targeted therapy are the major treatments for gastric cancer (GC), but drug resistance limits its effectiveness. Here, we profile the proteome of 206 tumor tissues from patients with GC undergoing either chemotherapy or anti-HER2-based therapy. Proteome-based classification reveals four subtypes (G-I-G-IV) related to different clinical and molecular features. MSI-sig high GC patients benefit from docetaxel combination treatment, accompanied by anticancer immune response. Further study reveals patients with high T cell receptor signaling respond to anti-HER2-based therapy; while activation of extracellular matrix/PI3K-AKT pathway impair anti-tumor effect of trastuzumab. We observe CTSE functions as a cell intrinsic enhancer of chemosensitivity of docetaxel, whereas TKTL1 functions as an attenuator. Finally, we develop prognostic models with high accuracy to predict therapeutic response, further validated in an independent validation cohort. This study provides a rich resource for investigating the mechanisms and indicators of chemotherapy and targeted therapy in GC.

Glioblastoma multiforme targeted delivery of docetaxel using bevacizumab-modified nanostructured lipid carriers impair in vitro cell growth and in vivo tumor progression

Glioblastoma multiforme (GBM) is the most common malignant brain cancer, characterized by high invasiveness and poor prognosis. Docetaxel (DTX) is a chemotherapeutic drug with promising anti-tumor properties. However, conventional intravenous formulations exhibit side effects of systemic biodistribution and low brain bioavailability, limiting their clinical use. The current work aimed to evaluate the effect of DTX-loaded nanostructured lipid carriers (NLC) functionalized with bevacizumab (BVZ-NLC-DTX) against GBM using in vitro and in vivo models. The NLC was obtained by the fusion-emulsification method followed by sonication, with narrow size distribution, negative zeta potential, and low polydispersity index. NLC showed DTX entrapment efficiency above 90%. BVZ coupling efficiency was 62% and BVZ integrity after functionalization was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Calorimetry studies confirmed thermal stability and molecular dispersion of DTX in the lipid matrix. NLC showed a sustained DTX release over 84 h. In vitro anti-tumor assays shown that BVZ-NLC-DTX selectively increased the cytotoxic of DTX in cells overexpressing VEGF (U87MG and A172), but not in peripheral blood mononuclear cells (PMBCs), promoting cell death by apoptosis. BVZ functionalization did not impair cellular uptake. An in vivo orthotopic rat model demonstrated that free-DTX was not capable of reducing tumor growth whereas BVZ-NLC-DTX reduced up to 70% tumor volume after 15-days of treatment. Therefore, this study contributes to understanding new nanotechnology-based vehicles capable of reaching the brain more efficiently and repurposing the use of anti-cancer drugs in GBM treatment.

Synergistic Antiproliferative Effects of All-Trans Retinoic Acid and Paclitaxel on Autosomal Dominant Polycystic Kidney Disease Epithelial Cells

Autosomal dominant polycystic kidney disease (ADPKD) is a genetic disorder characterized by uncontrollable epithelial cell growth, cyst formation, and kidney malfunction. In the present study, we investigated the antiproliferative effects of the treatment with the combination of paclitaxel (PAC) and all-trans retinoic acid (ATRA) on ADPKD epithelial cells. Our results show that the combined treatment with 1 nM PAC and 10 nM ATRA significantly suppressed ADPKD cell proliferation (20%), while the treatment with ATRA or PAC alone had no such effect. Treatment with PAC and ATRA induced cell cycle arrest at the G2/M phase and apoptosis by upregulating p53 and caspase-8 expression and increased the intracellular calcium (Ca²⁺) level possibly by enhancing Ca²⁺ uptake via plasma membrane channels. In addition, this treatment suppressed extracellular signal-regulated kinase signaling possibly through mitogen-activated protein kinase phosphatase-1 activation. Thus, the combination of PAC and ATRA can be explored as a potential treatment regimen for ADPKD.

TH1902, a new docetaxel-peptide conjugate for the treatment of sortilin-positive triple-negative breast cancer

Triple‐negative breast cancer (TNBC) is a heterogeneous subgroup of cancers which lacks the expression and/or amplification of targetable biomarkers (ie, estrogen receptor, progestrogen receptor, and human epidermal growth factor receptor 2), and is often associated with the worse disease‐specific outcomes than other breast cancer subtypes. Here, we report that high expression of the sortilin (SORT1) receptor correlates with the decreased survival in TNBC patients, and more importantly in those bearing lymph node metastases. By exploiting SORT1 function in ligand internalization, a new anticancer treatment strategy was designed to target SORT1‐positive TNBC‐derived cells both in vitro and in two in vivo tumor xenografts models. A peptide (TH19P01), which requires SORT1 for internalization and to which many anticancer drugs could be conjugated, was developed. In vitro, while the TH19P01 peptide itself did not exert any antiproliferative or apoptotic effects, the docetaxel‐TH19P01 conjugate (TH1902) exerted potent antiproliferative and antimigratory activities when tested on TNBC‐derived MDA‐MB‐231 cells. TH1902 triggered faster and more potent apoptotic cell death than did unconjugated docetaxel. The apoptotic and antimigratory effects of TH1902 were both reversed by two SORT1 ligands, neurotensin and progranulin, and on siRNA‐mediated silencing of SORT1. TH1902 also altered microtubule polymerization and triggered the downregulation of the anti‐apoptotic Bcl‐xL biomarker. In vivo, both i.p. and i.v. administrations of TH1902 led to greater tumor regression in two MDA‐MB‐231 and HCC‐70 murine xenograft models than did docetaxel, without inducing neutropenia. Altogether, the data demonstrates the high in vivo efficacy and safety of TH1902 against TNBC through a SORT1 receptor‐mediated mechanism. This property allows for selective treatment of SORT1‐positive TNBC and makes TH1902 a promising avenue for personalized therapy with the potential of improving the therapeutic window of cytotoxic anticancer drugs such as docetaxel.

Anticancer Properties of Platinum Nanoparticles and Retinoic Acid: Combination Therapy for the Treatment of Human Neuroblastoma Cancer

Neuroblastoma is the most common extracranial solid tumor in childhood. The different treatments available for neuroblastoma are challenged by high rates of resistance, recurrence, and progression, most notably in advanced cases and highly malignant tumors. Therefore, the development of more targeted therapies, which are biocompatible and without undesired side effects, is highly desirable. The mechanisms of actions of platinum nanoparticles (PtNPs) and retinoic acid (RA) in neuroblastoma have remained unclear. In this study, the anticancer effects of PtNPs and RA on neuroblastoma were assessed. We demonstrated that treatment of SH-SY5Y cells with the combination of PtNPs and RA resulted in improved anticancer effects. The anticancer effects of the two compounds were mediated by cytotoxicity, oxidative stress (OS), mitochondrial dysfunction, endoplasmic reticulum stress (ERS), and apoptosis-associated networks. Cytotoxicity was confirmed by leakage of lactate dehydrogenase (LDH) and intracellular protease, and oxidative stress increased the level of reactive oxygen species (ROS), 4-hydroxynonenal (HNE), malondialdehyde (MDA), and nitric oxide (NO), and protein carbonyl content (PCC). The combination of PtNPs and RA caused mitochondrial dysfunction by decreasing the mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) content, number of mitochondria, and expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). Endoplasmic reticulum-mediated stress and apoptosis were confirmed by upregulation of protein kinase RNA-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1 (IRE1), activating transcription factor 6 (ATF6), activating transcription factor 4 (ATF4), p53, Bax, and caspase-3 and down regulation of B-cell lymphoma 2 (BCl-2). PtNPs and RA induced apoptosis, and oxidative DNA damage was evident by the accumulation of 8-hydroxy-2-deoxyguanosine (8-OHdG) and 8-hydroxyguanosine (8-OHG). Finally, PtNPs and RA increased the differentiation and expression of differentiation markers. Differentiated SH-SY5Y cells pre-treated with PtNPs or RA or the combination of both were more sensitive to the cytotoxic effect of cisplatin than undifferentiated cells. To our knowledge, this is the first study to demonstrate the effect of the combination of PtNPs and RA in neuroblastoma cells. PtNPs may be a potential preconditioning or adjuvant compound in chemotherapeutic treatment. The results of this study provide a rationale for clinical evaluation of the combination of PtNPs and RA for the treatment of children suffering from high-risk neuroblastoma.

Advances in Gold Nanoparticle-Based Combined Cancer Therapy

According to the global cancer observatory (GLOBOCAN), there are approximately 18 million new cancer cases per year worldwide. Cancer therapies are largely limited to surgery, radiotherapy, and chemotherapy. In radiotherapy and chemotherapy, the maximum tolerated dose is presently being used to treat cancer patients. The integrated development of innovative nanoparticle (NP) based approaches will be a key to address one of the main issues in both radiotherapy and chemotherapy: normal tissue toxicity. Among other inorganic NP systems, gold nanoparticle (GNP) based systems offer the means to further improve chemotherapy through controlled delivery of chemotherapeutics, while local radiotherapy dose can be enhanced by targeting the GNPs to the tumor. There have been over 20 nanotechnology-based therapeutic products approved for clinical use in the past two decades. Hence, the goal of this review is to understand what we have achieved so far and what else we can do to accelerate clinical use of GNP-based therapeutic platforms to minimize normal tissue toxicity while increasing the efficacy of the treatment. Nanomedicine will revolutionize future cancer treatment options and our ultimate goal should be to develop treatments that have minimum side effects, for improving the quality of life of all cancer patients.

Inhibition of Notch pathway enhances the anti-tumor effect of docetaxel in prostate cancer stem-like cells

Background

Prostate cancer stem-like cells (PCSCs) likely participate in tumor progression and recurrence and demonstrate resistance to chemotherapy. The Notch pathway plays a role in the maintenance of the stemness in PCSCs. This study aimed to investigate the efficacy of Notch signaling inhibition as an adjuvant to docetaxel (DOX) in PCSCs.

Methods

PCSCs derived from the PC-3 cell line were examined for Notch-1 expression. The effect of Notch inhibition on response to DOX was evaluated in PCSCs in vitro and in murine models using a γ-secretase inhibitor (GSI), PF-03084014. Impacts on cell proliferation, apoptosis, cell cycle, and sphere formation were evaluated.

Results

PC-3 PCSCs expressed elevated Notch-1 mRNA compared with PC-3 parental cells. The combination of GSI with DOX promoted DOX-induced cell growth inhibition, apoptosis, cell cycle arrest, and sphere formation in PCSCs. In nude mice bearing PC-3 PCSC-derived tumors, the combination of GSI and DOX reduced the tumor growth, which was associated with the decreased Notch-1 expression in tumor tissues.

Conclusions

These results reveal that inhibition of the Notch pathway enhances the anti-tumor effect of DOX in PC-3 PCSCs, and suggest that Notch inhibition may have clinical benefits in targeting PCSCs.

Cell Size-Based Decision-Making of a Viral Gene Circuit

Latently infected T cells able to reinitiate viral propagation throughout the body remain a major barrier to curing HIV. Distinguishing between latently infected cells and uninfected cells will advance efforts for viral eradication. HIV decision-making between latency and active replication is stochastic, and drug cocktails that increase bursts of viral gene expression enhance reactivation from latency. Here, we show that a larger host-cell size provides a natural cellular mechanism for enhancing burst size of viral expression and is necessary to destabilize the latent state and bias viral decision-making. Latently infected Jurkat and primary CD4+ T cells reactivate exclusively in larger activated cells, while smaller cells remain silent. In addition, reactivation is cell-cycle dependent and can be modulated with cell-cycle-arresting compounds. Cell size and cell-cycle dependent decision-making of viral circuits may guide stochastic design strategies and applications in synthetic biology and may provide important determinants to advance diagnostics and therapies.

Bohn-Wippert et al. investigate reactivation of T cells latently infected with HIV. They discover that only larger cells exit latency, while smaller cells remain silent. Viral expression bursts are cell size and cell-cycle dependent, presenting dynamic cell states, capable of active control, as sources of viral fate determination.

Polymeric Core-Shell Combinatorial Nanomedicine for Synergistic Anticancer Therapy

Core-shell nanostructures are promising platforms for combination drug delivery. However, their complicated synthesis process, poor stability, surface engineering, and low biocompatibility are major hurdles. Herein, a carboxymethyl chitosan-coated poly(lactide-co-glycolide) (cmcPLGA) core-shell nanostructure is prepared via a simple one-step nanoprecipitation self-assembly process. Engineered core-shell nanostructures are tested for combination delivery of loaded docetaxel and doxorubicin in a cancer-mimicked environment. The drugs are compartmentalized in a shell (doxorubicin, Dox) and a core (docetaxel, Dtxl) with loading contents of ∼1.2 and ∼2.06%, respectively. Carboxymethyl chitosan with both amine and carboxyl groups act as a polyampholyte in diminishing ζ-potential of nanoparticles from fairly negative (-13 mV) to near neutral (-2 mV) while moving from a physiological pH (7.4) to an acidic tumor pH (6) that can help the nanoparticles to accumulate and release the drug on-site. The dual-drug formulation was found to carry a clinically comparable 1.7:1 weight ratio of Dtxl/Dox, nanoengineered for the sequential release of Dox followed by Dtxl. Single and engineered combinatorial nanoformulations show better growth inhibition toward three different cancer cells compared to free drug treatment. Importantly, Dox-Dtxl cmcPLGA nanoparticles scored synergism with combination index values between 0.2 and 0.3 in BT549 (breast ductal carcinoma), PC3 (prostate cancer), and A549 (lung adenocarcinoma) cell lines, demonstrating significant cell growth inhibition at lower drug concentrations as compared to single-drug control groups. The observed promising performance of dual-drug formulation is due to the G2/M phase arrest and apoptosis.

Class IIb HDAC Inhibition Enhances the Inhibitory Effect of Am80, a Synthetic Retinoid, in Prostate Cancer

Combination therapy is often an effective strategy to treat cancer. In this study, we examined the growth-inhibitory effects of Am80 (tamibarotene), a specific retinoic acid receptor (RAR) α/β agonist, in combination with a histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA), or a DNA methyl transferase (DNMT) inhibitor, 5-aza-2'-deoxycytidine, on androgen receptor (AR)-positive and AR-negative prostate cancer cell lines (LNCaP and PC-3, respectively). We found that the combination therapy of SAHA and Am80 showed an enhanced growth-inhibitory effect on LNCaP cells. Further studies with various HDAC isotype-selective inhibitors showed that SAHA and KD5170 (a selective class I and II HDAC inhibitor) each increased the RARα protein level in LNCaP cells. Our results indicate that the target of the enhancing effect belongs to the Class IIb HDACs, especially HDAC6. Dual targeting of Class IIb HDAC and RARα may be a candidate therapeutic strategy for prostate cancer.

Combination Effect of δ-Tocotrienol and γ-Tocopherol on Prostate Cancer Cell Growth

Tocotrienols (T3s) and tocopherols (Tocs) are both members of the vitamin E family. It is known that δ-tocotrienol (δ-T3) has displayed the most potent anti-cancer activity amongst the tocotrienols. On the other hand, γ-tocopherol (γ-Toc) is reported to have a protective effect against prostate cancer. Therefore, we investigated whether the combination of γ-Toc and δ-T3 could strengthen the inhibitory effect of δ-T3 on prostate cancer cell growth. In this study the effect of combined δ-T3 (annatto T3 oil) and γ-Toc (Tmix, γ-Toc-rich oil) therapy was assessed against human androgen-dependent prostate cancer cells (LNCaP). We found that combined treatment of δ-T3 (10 μM) and γ-Toc (5 μM) resulted in reinforced anti-prostate cancer activity. Specifically, cell cycle phase distribution analysis revealed that in addition to G1 arrest caused by the treatment with δ-T3, the combination of δ-T3 with γ-Toc induced G2/M arrest. Enhanced induction of apoptosis by the combined treatment was also observed. These findings indicate that combination of δ-T3 and γ-Toc significantly inhibits prostate cancer cell growth due to the simultaneous cell cycle arrest in the G1 phase and G2/M phase.

Precision medicine applications in prostate cancer

Aided by developments in diagnostics and therapeutics, healthcare is increasingly moving toward precision medicine, in which treatment is customized to each individual. We discuss the relevance of precision medicine in prostate cancer, including gene targets, therapeutics and resistance mechanisms. We foresee precision medicine becoming an integral component of prostate cancer management to increase response to therapy and prolong survival.

Clathrin-mediated endocytic uptake of PUFA enriched self-nanoemulsifying lipidic systems (SNELS) of an anticancer drug against triple negative cancer and DMBA induced preclinical tumor model

The current studies envisage unravelling the underlying cellular internalisation mechanism of the systematically developed docetaxel (DTH) polyunsaturated fatty acid (PUFA) enriched self-nanoemulsifying lipidic micellar systems (SNELS). The concentration-, time- and cytotoxicity-related effects of DTH-SNELS on triple negative breast cancer (TNBC) MDA-MB-231 and non-TNBC MCF-7 cell lines were assessed through Presto-blue assay. Subsequently, rhodamine-123 (Rh-123) loaded SNELS were employed for evaluating their internalisation through flow cytometry and fluorescence microscopy, establishing it to be "clathrin-mediated" endocytic pathway. Apoptosis assay (65% cell death) and cell cycle distribution (47% inhibition at G2/M phase) further corroborated the cytotoxicity of DTH-SNELS towards cancerous cells. Biodistribution, histopathology and haematology studies indicated insignificant toxicity of the optimized formulation on vital organs. Preclinical anticancer efficacy studies using 7,12-dimethylbenzantracene (DMBA)-induced model construed significant reduction in breast tumor-volume. Overall, extensive in vitro and in vivo studies indicated the intracellular localization and cytotoxicity, suggesting DTH-SNELS as promising delivery systems for breast tumor therapeutics including TNBC.

Galiellalactone induces cell cycle arrest and apoptosis through the ATM/ATR pathway in prostate cancer cells

Galiellalactone (GL) is a fungal metabolite that presents antitumor activities on prostate cancer in vitro and in vivo. In this study we show that GL induced cell cycle arrest in G₂/M phase, caspase-dependent apoptosis and also affected the microtubule organization and migration ability in DU145 cells. GL did not induce double strand DNA break but activated the ATR and ATM-mediated DNA damage response (DDR) inducing CHK1, H2AX phosphorylation (fH2AX) and CDC25C downregulation. Inhibition of the ATM/ATR activation with caffeine reverted GL-induced G₂/M cell cycle arrest, apoptosis and DNA damage measured by fH2AX. In contrast, UCN-01, a CHK1 inhibitor, prevented GL-induced cell cycle arrest but enhanced apoptosis in DU145 cells. Furthermore, we found that GL did not increase the levels of intracellular ROS, but the antioxidant N-acetylcysteine (NAC) completely prevented the effects of GL on fH2AX, G₂/M cell cycle arrest and apoptosis. In contrast to NAC, other antioxidants such as ambroxol and EGCG did not interfere with the activity of GL on cell cycle. GL significantly suppressed DU145 xenograft growth in vivo and induced the expression of fH2AX in the tumors. These findings identify for the first time that GL activates DDR in prostate cancer.

Cancer stem cell mediated acquired chemoresistance in head and neck cancer can be abrogated by aldehyde dehydrogenase 1 A1 inhibition

Chemoresistance leading to disease relapse is one of the major challenges to improve outcome in head and neck cancers. Cancer Stem Cells (CSCs) are increasingly being implicated in chemotherapy resistance, this study investigates the correlation between CSC behavior and acquired drug resistance in in vitro cell line models. Cell lines resistant to Cisplatin (Cal-27 CisR, Hep-2 CisR) and 5FU (Cal-27 5FUR) with high Resistance Indices (RI) were generated (RI ≥ 3) by short-term treatment of head and neck squamous cell carcinoma (HNSCC) cell lines with chemotherapeutic drugs (Cisplatin, Docetaxel, 5FU), using a dose-incremental strategy. The cell lines (Cal-27 DoxR, Hep-2 DoxR, Hep-2 5FUR) that showed low RI, nevertheless had a high cross resistance to Cisplatin/5FU (P < 0.05). Cal-27 CisR and DoxR showed 12-14% enrichment of CD44+ cells, while CisR/5FUR showed 4-6% increase in ALDH1A1+ cells as compared to parental cells (P < 0.05). Increased expression of stem cell markers (CD44, CD133, NOTCH1, ALDH1A1, OCT4, SOX2) in these cell lines, correlated with enhanced spheroid/colony formation, migratory potential, and increased in vivo tumor burden (P < 0.05). Inhibition of ALDH1A1 in Cal-27 CisR led to down regulation of the CSC markers, reduction in migratory, self-renewal and tumorigenic potential (P < 0.05) accompanied by an induction of sensitivity to Cisplatin (P < 0.05). Further, ex vivo treatment of explants (n = 4) from HNSCC patients with the inhibitor (NCT-501) in combination with Cisplatin showed a significant decrease in proliferating cells as compared to individual treatment (P = 0.001). This study hence suggests an ALDH1A1-driven, CSC-mediated mechanism in acquired drug resistance of HNSCC, which may have therapeutic implications. © 2016 Wiley Periodicals, Inc.

Vitamin A family compounds, estradiol, and docetaxel in proliferation, apoptosis and immunocytochemical profile of human ovary endometrioid cancer cell line CRL-11731

Endometrioid carcinoma represents approximately 10% of cases of the malignant ovarian epithelial tumors. According to literature, the vitamin A (carotenoids and retinoids) plays an essential role in cell proliferation, differentiation and apoptosis in both normal and neoplastic ovarian tissues. Apart from that, the retinoids alter a cytotoxic effect of chemiotherapeutics, i.e. docetaxel, on ovarian cancer cell lines. Retinoids act on cancer cells throughout different mechanism than taxanes, so they may be the potential candidates for the new treatment strategies of ovarian cancer. The aim of the study was to determine the effects of vitamin A family compounds (retinol, beta-carotene, lycopene, all-trans -, 9-cis - and 13-cis retinoic acid) on the growth and proliferation of CRL-11731 endometrioid ovary cancer cell line and on docetaxel and estradiol activity in this culture. The assay was based on [3H] thymidine incorporation and the proliferative activity of PCNA- and Ki 67-positive cells. The apoptotic index and expression of the Bcl-2 and p53 antigens in CRL-11731 cells were also studied. Among vitamin A family compounds retinol and carotenoids, but not retinoids, inhibited the growth of cancer cells in dose dependent manner. Only the concentration of 100 muM of docetaxel inhibited incorporation [3H] thymidine into CRL-11731 cancer cells. Retinol (33.4%+/-8.5), carotenoids (beta-carotene 20 muM 4.7%+/-2.9, 50 muM 2.2%+/-0.9; lycopene 10 muM 7.6%+/-0.8, 20 muM 5.2%+/-2.5, 50 muM 2.9%+/-1.2), and 13-cis retinoic acid (19.7%+/-2.2) combined with docetaxel (100 muM) significantly decreased the percentage of proliferating cells (p<0.0001). The antiproliferative action of lycopene alone and in combination with docetaxel was also confirmed in immunohistochemical examination (decreased the percentage of PCNA and Ki67 positive cells). Also retinol (10 muM) and lycopene (20 and 50 muM) combined with estradiol (0.01 muM) statistically decreased the percentage of proliferating cells compared to the control (p<0.0001) and estradiol (p<0.01, p<0.0001) group (63.5%+/-14.8, 61.0%+/-20.6, 15.0%+/-5.5 respectively). In our experiments, the compounds tested induced an apoptotic effect. Docetaxel and estradiol increased the percentage of apoptotic cells (71% apoptotic cells after administration of 10 muM all-trans retinoic acid combined with 0.01 muM estradiol, p<0.0001). beta-carotene, lycopene and all-trans retinoic acid alone and in combination with docetaxel were found to influence the expression of bcl-2 and p53 antigen in the cells examined. The results of our study justified an important role of vitamin A in the pathophysiology of the ovarian endometrioid cancer.

Radiosensitization of TPGS-emulsified docetaxel-loaded poly(lactic-co-glycolic acid) nanoparticles in CNE-1 and A549 cells

Docetaxel is among the most effective radiosensitizers. It is widely used as radiosensitizer in many tumors, including head and neck carcinoma. Nevertheless, poor solubility and severe hypersensitivity limit its clinical use and its therapeutic effect remains to be improved. In this study, docetaxel-loaded polymeric nanoparticles were prepared by nanoprecipitation method to be new radiosensitizer with lower side effects and higher efficacy. The physiochemical characteristics of the nanoparticles were studied. Two human tumor cell lines which are resistant to radiotherapy were used in this research. We have compared the radioenhancement efficacy of docetaxel-loaded nanoparticles with docetaxel in A549 and CNE-1 cells. Compared with docetaxel, radiosensitization of docetaxel-loaded nanoparticles was improved significantly (sensitization enhancement ratio in A549 increased 1.24-fold to 1.68-fold when the radiation was applied 2 h after the drug, p < 0.01, sensitization enhancement ratio in CNE-1 increased 1.32-fold to 1.61-fold, p < 0.05). We explored the mechanisms for the radiosensitization efficiency and the difference between docetaxel and docetaxel-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles. The improved radiosensitization efficacy was associated with enhanced G2/M arrest, promoted apoptosis and the role of D-alpha-tocopheryl polyethylene glycol 1000 succinate which will enhance the cell uptake and inhibit the multiple drug resistance. Moreover, the radiosensitization efficacy of docetaxel-loaded nanoparticles was more prominent than docetaxel. In conclusion, tocopheryl polyethylene glycol 1000 succinate-emulsified docetaxel-loaded PLGA nanoparticles were more efficacious and fewer adverse effects were observed than with the commercial docetaxel formulation. Thus, PLGA nanoparticles hold promise as a radiosensitizing agent.

CXCL12/CXCR4 signaling counteracts docetaxel-induced microtubule stabilization via p21-activated kinase 4-dependent activation of LIM domain kinase 1

Emerging data highlight the significance of chemokine (C-X-C motif) ligand 12/chemokine (C-X-C motif) receptor 4 (CXCL12/CXCR4) signaling axis in the chemoresistance of several malignancies, including prostate cancer (PCa); however, underlying mechanisms remain largely elusive. Here, we demonstrate that CXCL12 treatment rescues the PCa cells from docetaxel (DTX)-induced toxicity by overriding its effect on cell cycle (G₂/M phase arrest). We further demonstrate that the chemoprotective effect of CXCL12 is abolished upon pharmacological inhibition or RNA interference-mediated silencing of CXCR4. Moreover, microtubule stabilization caused by DTX is suppressed in CXCL12-stimulated PCa cells as revealed by immunofluorescence and immunoblot analyses. The effect of CXCL12 on microtubule stabilization is abrogated when PCa cells are pre-treated with a CXCR4 antagonist. In additional studies, we show that the chemoprotective action of CXCL12/CXCR4 signaling is mediated by p21-activated kinase 4 (PAK4)-dependent activation of Lim domain kinase 1 (LIMK1), and inhibition of either PAK4 or LIMK1 leads to re-sensitization of PCa cells to DTX-induced tubulin polymerization and cellular toxicity even in the presence of CXCL12. Altogether, our findings uncover a novel mechanism underlying CXCL12/CXCR4 signaling-induced PCa chemoresistance and suggest that targeting of this signaling axis or its downstream effector pathway could lead to therapeutic enhancement of DTX.

Silencing of TGM2 reverses epithelial to mesenchymal transition and modulates the chemosensitivity of breast cancer to docetaxel

Epithelial to mesenchymal transition (EMT) plays a critical role in drug resistance. The aim of the present study was to further elucidate its role by examining the effect of tissue transglutaminase (TG2) on EMT and drug resistance in breast cancer. An antisense lentiviral (LV) short hairpin (sh)RNA construct specific to the TG2 gene (TGM2) was designed, synthesized and stably transfected into MDA-MB-231 cells to silence TGM2 by RNA interference (RNAi). The transfected cells expressed low levels of TG2 and constituted the RNAi (TGM2-shRNA) group. A control (NC) group was also established by transfecting MDA-MB-231 cells with scrambled shRNA. The expression levels of TG2, E-cadherin, vimentin and B-cell lymphoma (Bcl)-2 in the cells were examined via western blotting. The transfected MDA-MB-231 cells were divided into four groups, two of which were treated with doxetaxel (TXT): NC, RNAi, TXT and RNAi + TXT groups,. Cell proliferation was analyzed by MTT assay and cell apoptosis was detected by flow cytometry. An in vivo assay was also conducted, in which MDA-MB-231 cells transfected with scrambled shRNA or TGM2-shRNA were subcutaneously implanted into nude mice. After 2 weeks, TXT or vehicle was intraperitoneally administered at a dose of 10 mg/kg on day 1 of every week and tumor growth was monitored. Following the silencing of TGM2 in the MDA-MB-231 cells, the cells showed changes in morphology, indicating that an increased expression of TG2 was associated with a mesenchymal morphology. Transfection of the cells with TGM2-shRNA affected the expression of TG2, E-cadherin, vimentin and Bcl-2. In the MTT assay, the proliferation of MDA-MB-231 cells was significantly inhibited in the RNAi group compared with the control group (P<0.05), and the inhibitory effect increased in a time-dependent manner. Following treatment with TXT for 48 h, apoptosis was significantly promoted in the RNAi + TXT group compared with that in the other groups (P<0.05). Measurement of the tumors in the nude mice indicated that the combination of RNAi and TXT brought about a stronger antitumor effect than either treatment alone. These results suggest that the downregulation of TG2 reversed EMT and modulated the chemosensitivity of breast cancer to TXT. TG2 may be an important predictive and prognostic factor for the treatment efficacy of chemotherapy in patients with breast cancer.

Feasibility study of a randomized controlled trial comparing docetaxel chemotherapy and androgen deprivation therapy with sequential prostatic biopsies from patients with advanced non-castration-resistant prostate cancer

BACKGROUND AND OBJECTIVE

Sequential tissue biopsies taken during clinical trials of novel systemic anticancer therapies for advanced prostate cancer (PCa) may aid pharmacodynamic evaluation and biomarker discovery. We conducted a single institution phase-II open-labeled randomized study to assess the safety, tolerability, and early efficacy of docetaxel chemotherapy plus androgen deprivation therapy (ADT) vs. ADT alone for patients with advanced non-castration-resistant PCa with sequential prostatic biopsies.

PATIENTS AND METHODS

We randomized 30 patients with newly diagnosed high-grade locally advanced or metastatic (cT3-4/N0-1/M0-1) PCa to receive ADT with (n = 15) or without (n = 15) docetaxel. Transrectal ultrasound-guided prostatic biopsies were taken at randomization and ~22 weeks after treatment initiation. Primary end point: biochemical response rate. Secondary end points: time to progression and tumor profiling.

RESULTS

Both treatments appear to be well tolerated, and there was no difference in mean nadir prostate-specific antigen and time to prostate-specific antigen relapse between treatment arms (P>0.05). No adverse effects of pre- and post-treatment prostatic biopsies were observed. The study was neither designed nor sufficiently powered to demonstrate statistically significant differences in oncological outcomes or safety profiles between the 2 treatment arms.

CONCLUSIONS

Despite the lack of statistical power, our study suggests that docetaxel and ADT in combination may be well tolerated with apparently similar short-term efficacy compared with ADT alone for high-grade locally advanced or metastatic non-castration-resistant PCa, Sequential prostatic biopsies may provide tissue for tumor profiling to yield mechanistic or prognostic insights relating to novel systemic anticancer therapies.

Enhance Cancer Cell Recognition and Overcome Drug Resistance Using Hyaluronic Acid and α-Tocopheryl Succinate Based Multifunctional Nanoparticles

Multidrug resistance (MDR) presents a clinical obstacle to cancer chemotherapy. The main purpose of this study was to evaluate the potential of a hyaluronic acid (HA) and α-tocopheryl succinate (α-TOS) based nanoparticle to enhance cancer cell recognition and overcome MDR, and to explore the underlying mechanisms. A multifunctional nanoparticle, HTTP-50 NP, consisted of HA-α-TOS (HT) conjugate and d-α-tocopheryl polyethylene glycol succinate (TPGS) with docetaxel loaded in its hydrophobic core. The promoted tumor cell recognition and accumulation, cytotoxicity, and mitochondria-specific apoptotic pathways for the HTTP-50 NP were confirmed in MCF-7/Adr cells (P-gp-overexpressing cancer model), indicating that the formulated DTX and the conjugated α-TOS in the HTTP-50 NP could synergistically circumvent the acquired and intrinsic MDR in MCF-7/Adr cells. In vivo investigation on the MCF-7/Adr xenografted nude mice models confirmed that HTTP-50 NP possessed much higher tumor tissue accumulation and exhibited pronouncedly enhanced antiresistance tumor efficacy with reduced systemic toxicity compared with HTTP-0 NP and Taxotere. The mechanisms of the multifunctional HTTP-50 NP to overcome MDR and enhance antiresistance efficacy may be contributed by CD44 receptor-targeted delivery and P-gp efflux inhibition, and meanwhile to maximize antitumor efficacy by synergism of DTX and mitocan of α-TOS killing tumor cells.

Identification of a candidate prognostic gene signature by transcriptome analysis of matched pre- and post-treatment prostatic biopsies from patients with advanced prostate cancer

BACKGROUND

Although chemotherapy for prostate cancer (PCa) can improve patient survival, some tumours are chemo-resistant. Tumour molecular profiles may help identify the mechanisms of drug action and identify potential prognostic biomarkers. We performed in vivo transcriptome profiling of pre- and post-treatment prostatic biopsies from patients with advanced hormone-naive prostate cancer treated with docetaxel chemotherapy and androgen deprivation therapy (ADT) with an aim to identify the mechanisms of drug action and identify prognostic biomarkers.

METHODS

RNA sequencing (RNA-Seq) was performed on biopsies from four patients before and ~22 weeks after docetaxel and ADT initiation. Gene fusion products and differentially-regulated genes between treatment pairs were identified using TopHat and pathway enrichment analyses undertaken. Publically available datasets were interrogated to perform survival analyses on the gene signatures identified using cBioportal.

RESULTS

A number of genomic rearrangements were identified including the TMPRSS2/ERG fusion and 3 novel gene fusions involving the ETS family of transcription factors in patients, both pre and post chemotherapy. In total, gene expression analyses showed differential expression of at least 2 fold in 575 genes in post-chemotherapy biopsies. Of these, pathway analyses identified a panel of 7 genes (ADAM7, FAM72B, BUB1B, CCNB1, CCNB2, TTK, CDK1), including a cell cycle-related geneset, that were differentially-regulated following treatment with docetaxel and ADT. Using cBioportal to interrogate the MSKCC-Prostate Oncogenome Project dataset we observed a statistically-significant reduction in disease-free survival of patients with tumours exhibiting alterations in gene expression of the above panel of 7 genes (p = 0.015).

CONCLUSIONS

Here we report on the first "real-time" in vivo RNA-Seq-based transcriptome analysis of clinical PCa from pre- and post-treatment TRUSS-guided biopsies of patients treated with docetaxel chemotherapy plus ADT. We identify a chemotherapy-driven PCa transcriptome profile which includes the down-regulation of important positive regulators of cell cycle progression. A 7 gene signature biomarker panel has also been identified in high-risk prostate cancer patients to be of prognostic value. Future prospective study is warranted to evaluate the clinical value of this panel.

Isolation and purification of oligopeptides from Ruditapes philippinarum and its inhibition on the growth of DU‑145 cells in vitro

Ruditapes philippinarum is a member of the Veneridae family of marine bivalve molluscs. RPOI‑1 (Ruditapes philippinarum oligopeptide) is a tetrapeptide that can be extracted from Ruditapes philippinarum by means of enzymolysis. This study showed that RPOI‑1 strongly inhibits proliferation and induces apoptosis in DU‑145 human prostate cancer cells. When cells were treated with varying concentrations of RPOI‑1, significant inhibition of proliferation was detected by an MTT assay, and sub‑G1 and G2/M phase cell cycle arrest was observed using flow cytometric (FCM) analysis. Furthermore, morphological changes characteristic of apoptosis and an increase in the proportion of apoptotic cells were observed using double sequential acridine orange/ethidium bromide staining, FCM analysis and transmission election microscopy. FCM studies showed that exposing DU‑145 cells to 10, 20 and 30 mg/ml RPOI‑1 for 24 h increased the percentage of cells in the early‑stages of apoptotis in a dose‑dependent manner, with the numbers rising from 3.01% in the control group to 13.40% in the group treated with the highest dose.

Synergistic enhancement of cancer therapy using a combination of ceramide and docetaxel

Ceramide (CE)-based combination therapy (CE combination) as a novel therapeutic strategy has attracted great attention in the field of anti-cancer therapy. The principal purposes of this study were to investigate the synergistic effect of CE in combination with docetaxel (DTX) (CE + DTX) and to explore the synergy mechanisms of CE + DTX. The 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and combination index (CI) assay showed that simultaneous administration of CE and DTX with a molar ratio of 0.5:1 could generate the optimal synergistic effect on murine malignant melanoma cell (B16, CI = 0.31) and human breast carcinoma cell (MCF-7, CI = 0.48). The apoptosis, cell cycle, and cytoskeleton destruction study demonstrated that CE could target and destruct the microfilament actin, subsequently activate Caspase-3 and induce apoptosis. Meanwhile, DTX could target and disrupt the microtubules cytoskeleton, leading to a high proportion of cancer cells in G2/M-phase arrest. Moreover, CE plus DTX could cause a synergistic destruction of cytoskeleton, which resulted in a significantly higher apoptosis and a significantly higher arrest in G2/M arrest comparing with either agent alone (p < 0.01). The in vivo antitumor study evaluated in B16 tumor-bearing mice also validated the synergistic effects. All these results suggested that CE could enhance the antitumor activity of DTX in a synergistic manner, which suggest promising application prospects of CE + DTX combination treatment.

Inhibition of PARP1 by small interfering RNA enhances docetaxel activity against human prostate cancer PC3 cells

Though poly(ADP-ribose) polymerase 1 (PARP1) inhibitors have benefits in combination with radiotherapy in prostate cancers, few is known about the exactly role and underlying mechanism of PARP1 in combination with chemotherapy agents. Here our data revealed that inhibition of PARP1 by small interfering RNA (siRNA) could enhance docetaxel's activity against PC3 cells, which is associated with an accelerate repression of EGF/Akt/FOXO1 signaling pathway. Our results provide a novel role of PARP1 in transcription regulation of EGFR/Akt/FOXO1 signaling pathway and indicate that PARP1 siRNA combined with docetaxel can be an innovative treatment strategy to potentially improve outcomes in CRPC patients.

Does androgen-ablation therapy (AAT) associated autophagy have a pro-survival effect in LNCaP human prostate cancer cells?

WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: Androgen-ablation therapy (AAT) and chemotherapy are commonly used to treat incurable prostate cancer. To improve outcome, there is major on-going research to develop more effective treatments with less toxicity. Autophagy has been suggested from previous studies to play a potential role in cell survival and may be associated with resistance to chemotherapy. Autophagy is known to be upregulated by nutrient starvation or AAT in prostate cancer. However, its functional impact is not fully known. The present study describes the potential synergism between the blockade of autophagy and AAT alone or AAT combined with taxane chemotherapy. Hence, future combined treatment options are warranted to further investigate the clinical impact of autophagy suppression as a treatment strategy.

OBJECTIVE

To study the cellular effects of the anti-androgen bicalutamide on autophagy and its potential impact on response to androgen-ablation therapy (AAT) alone or combined with docetaxel chemotherapy in human prostate cancer LNCaP cells.

MATERIALS AND METHODS

LNCaP cells were treated with bicalutamide ± docetaxel, and cellular effects were assayed: lipidated LC3 (a microtubule-associated protein) for autophagy and its trafficking to fuse with lysosome; flow cytometry using propidium iodide or caspase 3 for cell death; and sulforhodamine B assay for cell growth.

RESULTS

Bicalutamide treatment enhanced autophagy in LNCaP cells with increased level of autophagosome coupled with an altered cellular morphology reminiscent of neuroendocrine differentiation. Consistent with the literature on the interaction between androgen receptor activation and taxane chemotherapy, bicalutamide diminished docetaxel mediated cytotoxicity. Significantly, pharmacological inhibition of autophagy with 3-methyladenine significantly enhanced the efficacy cell kill mediated by AAT ± docetaxel.

CONCLUSION

Autophagy associated with bicalutamide treatment in LNCaP cells may have a pro-survival effect and strategy to modulate autophagy may have a potential therapeutic value.

Functional p53 determines docetaxel sensitivity in prostate cancer cells

BACKGROUND

Docetaxel is the first line treatment for castration resistant prostate cancer (CRPC). However, docetaxel resistance rapidly develops. Identifying the critical mechanisms giving rise to docetaxel resistance is the major challenge in advanced prostate cancer.

METHODS

The effects of docetaxel on human DU145, PC3, LNCaP, and C4-2 prostate cancer cells were examined in cell culture, and p53 expression were analyzed by Western blot analysis. The potential role of p53 in docetaxel sensitivity in prostate cancer cells was tested by either p53 silencing using shRNA or p53 overexpression by introducing wild-type p53.

RESULTS

We found that DU145 (mutant p53) and PC3 (p53 null) cells were less sensitive than LNCaP and C4-2 cells expressing functional p53 in response to docetaxel. Docetaxel treatment induces considerably higher apoptosis in LNCaP and C4-2 cells than in DU145 and PC3 cells in a dose dependent manner. Docetaxel increases the levels of ser15 phosphorylation of p53 in a dose dependent manner in both LNCaP and C4-2 cells, while has no effect on the levels of ser15 phosphorylation of p53 in DU145 cells. These results suggest that p53 phosphorylation is associated with docetaxel sensitivity in prostate cancer cells. To further confirm whether p53 activation can induce cell sensitivity to docetaxel treatment, we used p53 shRNA to knock down p53 expression in C4-2 cells and determined the cells response to docetaxel treatment. Knockdown of p53 significantly down regulated p53 phosphorylation and blocked docetaxel induced apoptotic cell death compared to the vector control. To further confirm this observation, we established a stable knock out p53 in C4-2 cells. Down regulation of p53 in the stable p53 knock out C4-2 cells significantly inhibited docetaxel induced apoptotic cell death. We also used wild-type (WT) p53 to over express p53 in DU145 cells, and found that expression of WT-p53 in DU145 cells increased their sensitivity to docetaxel.

CONCLUSIONS

These results demonstrate that docetaxel induces p53 phosphorylation and that p53 status is a crucial determinant of docetaxel sensitivity in prostate cancer cells.

Efficient simultaneous tumor targeting delivery of all-trans retinoid acid and Paclitaxel based on hyaluronic acid-based multifunctional nanocarrier

An amphiphilic hyaluronic acid (HA)-g-all-trans retinoid acid (HRA) conjugate was successfully developed as a tumor-targeting nanocarrier for potentially synergistic combination chemotherapy of all-trans retinoid acid (ATRA) and paclitaxel (PTX). The HRA conjugate was synthesized by an imine reaction between HA-COOH and ATRA-NH2. PTX-loaded HRA nanoparticles possessed a high loading capacity, nanoscale particle sizes, and good biocompatible characteristics. Cell viability assays indicated that PTX-loaded HRA nanoparticles exhibited concentration- and time-dependent cytotoxicity. Moreover, they displayed obvious superiority in inducing the apoptosis of tumor cells. Cellular uptake analysis suggested that HRA nanoparticles could be efficiently taken up by cells via endocytic pathway and transport into the nucleus, contributing to HA receptor-mediated endocytosis and ATRA-induced nuclear translocation, respectively. Moreover, in vivo imaging analysis indicated that the accumulation of DiR-loaded HRA nanoparticles in tumor was increased obviously after intravenous administration as compared to free DiR solution, which confirmed that the HRA nanoparticles could assist the drugs targeting to the tumor. Furthermore, PTX-loaded HRA nanoparticles exhibited greater tumor growth inhibition effect in vivo with reducing the toxicity. Therefore, HRA nanoparticles can be considered as a promising targeted codelivery system for combination cancer chemotherapy.

Retinoid receptors in gastric cancer: expression and influence on prognosis

BACKGROUND

Gastric cancer is frequently lethal despite aggressive multimodal therapies, and new treatment approaches are therefore needed. Retinoids are potential candidate drugs: they prevent cell differentiation, proliferation and malignant transformation in gastric cancer cell lines. They interact with nuclear retinoid receptors (the retinoic acid receptors [RARs] and retinoid X receptors [RXRs]), which function as transcription factors, each with three subclasses, α, β and γ. At present, little is known about retinoid expression and influence on prognosis in gastric cancers.

PATIENTS AND METHODS

We retrospectively analyzed the expression of the subtypes RARα, RARβ, RARγ, RXRα, RXRβ, RXRγ by immunohistochemistry in 147 gastric cancers and 51 normal gastric epithelium tissues for whom clinical follow-up data were available and correlated the results with clinical characteristics. In addition, we quantified the expression of retinoid receptor mRNA using real- time PCR (RT-PCR) in another 6 gastric adenocarcinoma and 3 normal gastric tissues. From 2008 to 2010, 80 patients with gastric cancers were enrolled onto therapy with all-trans-retinoic acid (ATRA).

RESULTS

RARα, RARβ, RARγ and RXRγ positively correlated with each other (p<0.001) and demonstrated significantly lower levels in the carcinoma tissue sections (p<0.01), with lower RARβ, RARγ and RXRα expression significantly related to advanced stages (p<=0.01). Tumors with poor histopathologic grade had lower levels of RARα and RARβ in different histological types of gastric carcinoma (p<0.01). Patients whose tumors exhibited low levels of RARa expression had significantly lower overall survival compared with patients who had higher expression levels of this receptor (p<0.001, HR=0.42, 95.0% CI 0.24-0.73), and patients undergoing ATRA treatment had significantly longer median survival times (p=0.007, HR=0.41, 95.0% CI 0.21-0.80).

CONCLUSIONS

Retinoic acid receptors are frequently expressed in epithelial gastric cancer with a decreased tendency of expression and RARa may be an indicator of a positive prognosis. This study provides a molecular basis for the therapeutic use of retinoids against gastric cancer.

Retinoic Acid Induces Apoptosis of Prostate Cancer DU145 Cells through Cdk5 Overactivation

Retinoic acid (RA) has been believed to be an anticancer drug for a long history. However, the molecular mechanisms of RA actions on cancer cells remain diverse. In this study, the dose-dependent inhibition of RA on DU145 cell proliferation was identified. Interestingly, RA treatment triggered p35 cleavage (p25 formation) and Cdk5 overactivation, and all could be blocked by Calpain inhibitor, Calpeptin (CP). Subsequently, RA-triggered DU145 apoptosis detected by sub-G1 phase accumulation and Annexin V staining could also be blocked by CP treatment. Furthermore, RA-triggered caspase 3 activation and following Cdk5 over-activation were destroyed by treatments of both CP and Cdk5 knockdown. In conclusion, we report a new mechanism in which RA could cause apoptosis of androgen-independent prostate cancer cells through p35 cleavage and Cdk5 over-activation. This finding may contribute to constructing a clearer image of RA function and bring RA as a valuable chemoprevention agent for prostate cancer patients.

Enhanced docetaxel-mediated cytotoxicity in human prostate cancer cells through knockdown of cofilin-1 by carbon nanohorn delivered siRNA

We synthesized a non-viral delivery system (f-CNH3) for small interfering RNA (siRNA) by anchoring a fourth-generation polyamidoamine dendrimer (G4-PAMAM) to carbon nanohorns (CNHs). Using this new compound, we delivered a specific siRNA designed to knockdown cofilin-1, a key protein in the regulation of cellular cytoskeleton, to human prostate cancer (PCa) cells. The carbon nanohorn (CNH) derivative was able to bind siRNA and release it in the presence of an excess of the polyanion heparin. Moreover, this hybrid nanomaterial protected the siRNA from RNAse-mediated degradation. Synthetic siRNA delivered to PCa cells by f-CNH3 decreased the cofilin-1 mRNA and protein levels to about 20% of control values. Docetaxel, the drug of choice for the treatment of PCa, produced a concentration-dependent activation of caspase-3, an increase in cell death assessed by lactate dehydrogenase release to the culture medium, cell cycle arrest and inhibition of tumor cell proliferation. All of these toxic effects were potentiated when cofilin-1 was down regulated in these cells by a siRNA delivered by the nanoparticle. This suggests that knocking down certain proteins involved in cancer cell survival and/or proliferation may potentiate the cytotoxic actions of anticancer drugs and it might be a new therapeutic approach to treat tumors.

Combination effect of PectaSol and Doxorubicin on viability, cell cycle arrest and apoptosis in DU-145 and LNCaP prostate cancer cell lines

The effect of PectaSol on Dox (Doxorubicin) cytotoxicity in terms of apoptosis and cell cycle changes in PCa (prostate cancer) cell lines (DU-145 and LNCaP) has been investigated. Combination of PectaSol and Dox resulted in a viability of 29.4 and 32.6% (P<0.001) in DU-145 and LNCaP cells. The IC₅₀ values decreased 1.5-fold and 1.3-fold in the DU-145 and LNCaP cells respectively. In the DU-145 cells, combination of PectaSol and Dox resulted in a reduction in p27 gene and protein expression (P<0.001). In LNCaP cells, this combination increased p53, p27 and Bcl-2 expression. Treatment with both drugs in DU-145 cells led to an increase in sub-G₁ arrest (54.6% compared with 12.2% in Dox). In LNCaP cells, combination of the drugs led to an increased in G₂/M arrest (61.7% compared with 53.6% in Dox). Based on these findings, progressive cytotoxicity effect of Dox and PectaSol together rapidly induce cell death in DU-145 through apoptosis and in LNCaP cells through cell cycle arrest (G₂/M arrest).

Novel hydrophilic docetaxel (CQMU-0519) analogue inhibits proliferation and induces apoptosis in human A549 lung, SKVO3 ovarian and MCF7 breast carcinoma cell lines

OBJECTIVE

Objectives of this investigation were not merely to perform a comparative study with original docetaxel, but to define anti-proliferative and apoptotic effects of novel hydrophilic docetaxel (CQMU-0519) analogue on A549 lung, SKVO3 ovary and MCF7 breast carcinoma cell lines.

MATERIALS AND METHODS

The materials for the study consist of a completely new docetaxel analogue (CQMU-0519), synthesized by the Department of Pharmacology, Chongqing Medical University, China, which is completely soluble in water. 50 nm of drug concentration was utilized on all three cell lines where cell population growth was assessed using cell culture kit-8 and flow cytometry analysis, whereas apoptotic pathways were unveiled by use of annexin-V FITC, apoptosis DNA ladder, caspases-3, 6, 8 and 9; in the meanwhile, regulation of Bcl-2 family members was analysed by western blotting.

RESULT

The novel docetaxel analogue (CQMU-0519) suppressed cell proliferation in all three cell lines, inhibition of cell proliferation and cell cycle arrest being more evident in G(2) /M phase. Also, in both lung and ovarian cell lines, apoptotic levels were higher as measured by the various tests performed, and downregulation of Bcl-2 and Bcl-xL with increased expressions of Bad and Bax indicated the intrinsic pathway for apoptosis. Nevertheless, it was found that MCF7 cells, although also manifesting high levels of apoptosis, used the extrinsic pathway instead. Hence, it was shown that novel docetaxel analogue (CQMU-0519) may have some prospective use in future clinical trials.

CONCLUSIONS

Novel hydrophilic docetaxel analogue (CQMU-0519) inhibited cell proliferation and enhanced the intrinsic apoptotic pathway in lung and ovarian carcinoma cells, whereas it used the extrinsic one in breast adenocarcinoma cells.

Activation of Multiple Molecular Mechanisms for Increasing Apoptosis in Human Glioblastoma T98G Xenograft

Glioblastoma is the most malignant brain tumor of astroglial origin. It renders poor response or resistance to existing therapeutics. We used all-trans retinoic acid (ATRA) and interferon gamma (IFN-γ) alone and in combination for controlling human glioblastoma T98G xenografted in nude mice. Histopathological examination showed astrocytic differentiation in ATRA group, some apoptosis in IFN-γ group, and occurrence of differentiation and enhancement of apoptosis in ATRA plus IFN-γ group. ATRA plus IFN-γ induced extrinsic pathway of apoptosis by activation of caspase-8 and cleavage of Bid to tBid and also down regulation of hTERT, c-IAP2, and survivin and upregulation of Smac/Diablo to promote apoptosis. Mitochondrial release of apoptosis-inducing factor (AIF) induced caspase-independent pathway and also upregulation of calpain and caspase-dependent pathways ultimately activated caspase-3 for apoptosis. Increased activities of calpain and caspase-3 degraded 270 kD α-spectrin at the specific sites to generate 145 kD spectrin breakdown product (SBDP) and 120 kD SBDP, respectively. In situ TUNEL and double immunofluorescent labelings detected apoptosis with increased expression of calpain, caspase-12, caspase-3, and AIF in tumors after treatment with IFN-γ and most effectively with ATRA plus IFN-γ. Results indicated that ATRA plus IFN-γ activated multiple molecular mechanisms for increasing apoptosis in human glioblastoma in vivo.

Enhancement of docetaxel-induced cytotoxicity and apoptosis by all-trans retinoic acid (ATRA) through downregulation of survivin (BIRC5), MCL-1 and LTbeta-R in hormone- and drug resistant prostate cancer cell line, DU-145

Background

The management of hormone-refractory prostate cancer (HRPC) still remains as an important challenge of daily oncology practice. Docetaxel has proved to be a first line treatment choice. All-trans retinoic acid (ATRA) could potently inhibit the growth of prostate cancer cells in vitro and its combination with various anticancer agents results in increased cytotoxicity. Based on these data, our aim was to examine the synergistic/additive cytotoxic and apoptotic effects of combination of docetaxel and ATRA, in hormone- and drug refractory human DU-145 prostate cancer cells. Furthermore, we have searched for the underlying mechanisms of apoptosis by demonstrating apoptosis-related genes.

Methods

XTT cell proliferation assay was used for showing cytotoxicity. For verifying apoptosis, both DNA Fragmentation by ELISA assay and caspase 3/7 activity measurement were used. For detecting the mechanism of apoptosis induced by docetaxel-ATRA combination, OligoGeArray^® which consists of 112 apoptosis related genes was used.

Results

Our results revealed that docetaxel and ATRA were synergistically cytotoxic and apoptotic in DU-145 cells, in a dose- and time dependent manner. It was also shown by our studies that apoptosis was induced in DU-145 prostate carcinoma cells with significant cytotoxicity, no matter which agent applied first. We have found out that docetaxel-ATRA combination significantly downregulates survivin (BIRC5), myeloid cell leukemia-1 (MCL-1) and lymphotoxin β-receptor (LTβR) genes, which all three have pivotal roles in regulation of apoptosis and cell cycle progression.

Conclusion

In conclusion, we strongly suggest that docetaxel and ATRA combination is a good candidate for this challenging era of daily oncologic practice. Also, the combination of docetaxel and ATRA might allow a reduction in docetaxel doses and by this way may diminish docetaxel adverse effects while maintaining the therapeutic effect in patients with HRPC.

Epothilones and new analogues of the microtubule modulators in taxane-resistant disease

BACKGROUND

Microtubule-stabilising agents typified by the epothilone class of drug have demonstrated promising activity in Phase II and III clinical trials.

OBJECTIVE

Data supporting the efficacy of these agents are reviewed and their potential use in taxane-refractory disease assessed.

METHODS

Preclinical evidence assessing the role of the spindle assembly checkpoint in determining the cellular response to microtubule stabilization are presented together with clinical data documenting the efficacy of non-taxane microtubule modulators.

RESULTS/CONCLUSIONS

Evidence suggests that microtubule-stabilising agents prolong activation of the spindle assembly checkpoint which may promote cancer cell death in mitosis or following mitotic exit. A weakened spindle assembly checkpoint is associated with altered sensitivity to agents targeting the microtubule and therefore pathways of drug resistance may be shared by these cytotoxic therapies. Preliminary clinical trial data do suggest modest activity of epothilones in truly taxane-resistant patient cohorts, indicating the potential niche for these agents in a molecularly undefined patient group, potentially implicating the role of P-glycoprotein in the acquisition of taxane-resistant disease. Trial data of these antimitotic agents will be presented together with their potential role in taxane-resistant disease and the implications for future clinical trial design.