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

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.

The Role of Nuclear Receptors in Prostate Cancer

The nuclear receptor (NR) superfamily consists of 48 members that are divided into seven subfamilies. NRs are transcription factors that play an important role in a number of biological processes. The NR superfamily includes androgen receptor, which is a key player in prostate cancer pathogenesis, suggesting the functional roles of other NRs in prostate cancer. The findings on the roles of NRs in prostate cancer thus far have shown that several NRs such as vitamin D receptor, estrogen receptor β, and mineralocorticoid receptor play antioncogenic roles, while other NRs such as peroxisome proliferator-activated receptor γ and estrogen receptor α as well as androgen receptor play oncogenic roles. However, the roles of other NRs in prostate cancer remain controversial or uninvestigated. Further research on the role of NRs in prostate cancer is required and may lead to the development of novel preventions and therapeutics for prostate cancer.

SP1 and RARα regulate AGAP2 expression in cancer

AGAP2 (Arf GAP with GTP-binding protein-like domain, Ankyrin repeat and PH domain 2) isoform 2 is considered a proto-oncogene, but not much is known about AGAP2 gene expression regulation. To get some insight into this process, AGAP2 proximal promoter was cloned and characterised using reporter assays. We have identified SP1 as a transcription factor bound to AGAP2 promoter and required for AGAP2 expression in two different types of cancer cells (KU812, a chronic myeloid leukaemia cell line; and DU145, a prostate cancer cell line): silencing SP1 decreased AGAP2 protein levels. We have also found that all-trans retinoic acid (ATRA) treatment increased AGAP2 protein levels in both cell lines whilst curcumin treatment reduced ATRA-mediated AGAP2 increase. Furthermore, chromatin immunoprecipitation studies revealed the presence of RARα, RXRα and the lysine acetyl transferase PCAF in AGAP2 promoter. Our results provide a novel understanding of AGAP2 expression regulation that could be beneficial to those patients with cancers where AGAP2 is overexpressed.

Engineering fast dissolving sodium acetate mediated crystalline solid dispersion of docetaxel

It is hypothesized that a novel crystalline solid dispersion (CSD) of docetaxel (C-DXT) can be engineered by dispersing native docetaxel (DXT, a BCS class II drug) in sodium acetate crystal (SA). DXT is dissolved in glacial acetic/SA solution and freeze-dried. The resulting C-DXT is characterized by differential scanning calorimetry (DSC), powder X-ray analysis (PXRD), LC-MS/MS, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Quartz crystal microbalance with dissipation monitoring (QCM-D) and dynamic light scattering (DLS). Its cytotoxicity on model cancerous (MCF-7, MDA-MB-468) and normal breast cells (MCF-10A) is assessed by MTS assay. SEM/TEM data and the absence of the characteristics peaks of DXT on the DSC curve (at 193.4 °C) and the XRD scan (at 2θ = 15.31 °C and 23.04 °C) confirm the presence of C-DXT in SA. The LC-MS/MS data indicates the chemical stability of DXT. The yield and C-DXT loading are 95.2% and 6.52% w/w, respectively. The C-DXT rapidly forms an aqueous non-rigid nanosuspension with a faster drug dissolution rate compared to native DXT. Unlike, control Tween 80/ethanol, SA is noncytotoxic to normal cells. However, C-DXT's cytotoxicity is time and dose dependent for all diseased cells. This unique CSD process might be applicable to other hydrophobic bioactive agents to enhance their safety and efficacy.

Reversal of drug resistance by planetary ball milled (PBM) nanoparticle loaded with resveratrol and docetaxel in prostate cancer

The folate receptor (FR) is a valued target that is highly expressed in various cancers, which will expedite the development of ligand-receptor binding based cancer therapeutics. In the present investigation, through tissue microarray analysis, we report higher levels of folate receptor expression in prostate cancer (PCa) tissue derived from patients, which were minimal in normal tissue. For folate-receptor based targeted therapy of PCa, we generated novel planetary ball milled (PBM) nanoparticles (NPs) encapsulated with resveratrol (RES), and in combination with docetaxel (DTX) and conjugated with folic acid (FA) on the surface. The cytotoxic effect of FA-conjugated DTX-nanoparticles was found effectual that reduced the concentration of free drug (DTX) to 28 times. Flow cytometry analysis showed a significant increase in the number of apoptotic cells by 30.92% and 65.9% in the FA-conjugated RES and in combination with DTX nanoparticle formulation respectively. However, only 8.9% apoptotic cells were found with control (empty NP). The expressions of NF-kB p65, COX-2, pro (BAX, BAK) and anti-apoptotic (BCL-2, BCL-XL) genes were significantly reduced after treatment with FA-RES + DTX-NP. In addition, the FA-conjugated DTX formulation exhibited additional cytotoxic effects with the down-regulation of survivin and an increased expression of Cleaved Caspase-3 in PCa cells. Further, we observed that treating DTX resistant PCa cells with FA-RES + DTX-NP exhibited a reversal of the ABC-transporter markers thereby limiting the multidrug resistance phenotype of the cancer cells. Our results strongly suggested that FA conjugated nanoparticle drugs acted as effective inhibitors of drug efflux that effectually enhances the intracellular concentration of the drug to exhibit their cytotoxic effect.

Knockdown of the M2 Isoform of Pyruvate Kinase (PKM2) with shRNA Enhances the Effect of Docetaxel in Human NSCLC Cell Lines In Vitro

PURPOSE

The aim of our study was to explore the relationships between the M2 isoform of pyruvate kinase (PKM2) and the sensitivity of human non-small cell lung cancer (NSCLC) cells to docetaxel in vitro.

MATERIALS AND METHODS

With the method of plasmid transfection, we silenced the expression of PKM2 successfully in A549 and H460 cells. Western blotting and real-time PCR were applied to detect PKM2 expression at protein and gene levels. Cell viability was examined by CCK8 assay. Cell cycle distribution and apoptosis were examined by flow cytometry. P21 and Bax were detected.

RESULTS

Expression of PKM2 mRNA and protein were significantly decreased by shRNA targeting PKM2. Silencing of PKM2 increased docetaxel sensitivity of human NSCLC A549 and H460 cells in a collaborative manner, resulting in strong suppression of cell viability. The results of flow cytometric assays suggested that knockdown of PKM2 or docetaxel treatment, whether used singly or in combination, blocked the cells in the G2/M phase, which is in consistent with the effect of the two on the expression of p21. Cells with PKM2 silencing were more likely to be induced into apoptosis by docetaxel although knockdown of PKM2 alone can't induce apoptosis significantly, which is in consistent with the effect of the two on Bax expression.

CONCLUSION

The results suggest that PKM2 knockdown could serve as a chemosensitizer to docetaxel in non-small lung cancer cells through targeting PKM2, leading to inhibition of cell viability, increase of cell arrest of G2/M phase and apoptosis.

Nanoscale drug delivery for taxanes based on the mechanism of multidrug resistance of cancer

Taxanes are one type of the most extensively used chemotherapeutic agents to treat cancers. However, their clinical use is severely limited by intrinsic and acquired resistance. A diverse variety of mechanisms has been implicated about taxane resistance, such as alterations of drug targets, overexpression of efflux transporters, defective apoptotic machineries, and barriers in drug transport. The deepening understanding of molecular mechanisms of taxane resistance has spawned a number of targets for reversing resistance. However, circumvention of taxane resistance would not only possess therapeutic potential, but also face with clinical challenge, which accelerates the development of optimal nanoscale delivery systems. This review highlights the current understanding on the mechanisms of taxane resistance, and provides a comprehensive analysis of various nanoscale delivery systems to reverse taxane resistance.

Microarray analysis of cell cycle gene expression in adult human corneal endothelial cells

Corneal endothelial cells (ECs) form a monolayer that controls the hydration of the cornea and thus its transparency. Their almost nil proliferative status in humans is responsible, in several frequent diseases, for cell pool attrition that leads to irreversible corneal clouding. To screen for candidate genes involved in cell cycle arrest, we studied human ECs subjected to various environments thought to induce different proliferative profiles compared to ECs in vivo. Donor corneas (a few hours after death), organ-cultured (OC) corneas, in vitro confluent and non-confluent primary cultures, and an immortalized EC line were compared to healthy ECs retrieved in the first minutes of corneal grafts. Transcriptional profiles were compared using a cDNA array of 112 key genes of the cell cycle and analysed using Gene Ontology classification; cluster analysis and gene map presentation of the cell cycle regulation pathway were performed by GenMAPP. Results were validated using qRT-PCR on 11 selected genes. We found several transcripts of proteins implicated in cell cycle arrest and not previously reported in human ECs. Early G1-phase arrest effectors and multiple DNA damage-induced cell cycle arrest-associated transcripts were found in vivo and over-represented in OC and in vitro ECs. Though highly proliferative, immortalized ECs also exhibited overexpression of transcripts implicated in cell cycle arrest. These new effectors likely explain the stress-induced premature senescence that characterizes human adult ECs. They are potential targets for triggering and controlling EC proliferation with a view to increasing the cell pool of stored corneas or facilitating mass EC culture for bioengineered endothelial grafts.

Mithramycin A induces apoptosis by regulating the mTOR/Mcl-1/tBid pathway in androgen-independent prostate cancer cells

Mithramycin A (Mith) is an aureolic acid-type polyketide produced by various soil bacteria of the genus Streptomyces. Mith inhibits myeloid cell leukemia-1 (Mcl-1) to induce apoptosis in prostate cancer, but the molecular mechanism underlying this process has not been fully elucidated. The aim of this study was therefore to investigate the detailed molecular mechanism related to Mith-induced apoptosis in prostate cancer cells. Mith decreased the phosphorylation of mammalian target of rapamycin (mTOR) in both cell lines overexpressing phospho-mTOR compared to RWPE-1 human normal prostate epithelial cells. Mith significantly induced truncated Bid (tBid) and siRNA-mediated knock-down of Mcl-1 increased tBid protein levels. Moreover, Mith also inhibited the phosphorylation of mTOR on serine 2448 and Mcl-1, and increased tBid protein in prostate tumors in athymic nude mice bearing DU145 cells as xenografts. Thus, Mith acts as an effective tumor growth inhibitor in prostate cancer cells through the mTOR/Mcl-1/tBid signaling pathway.

Effects of simvastatin on retinoic acid system in primary human endometrial stromal cells and in a chimeric model of human endometriosis

CONTEXT

Retinoic acid (RA) may promote survival or apoptosis of cells, depending on the levels of binding proteins: apoptosis-inducing cellular RA binding protein 2 (CRABP2), and cell survival-promoting fatty acid binding protein 5 (FABP5). Increased cellular uptake of retinol and altered actions of RA related to reduced expression of CRABP2 may contribute to the development of endometriosis. Recently statins have been shown to inhibit growth of human endometrial stromal (HES) cells and to reduce the number and size of endometriotic implants in experimental models of this disorder.

OBJECTIVE

The objective of the study was to determine whether effects of simvastatin on HES cells and experimental endometriotic implants are related to the modulation of the RA system.

METHODS

Effects of simvastatin and RA on proliferation and apoptosis of HES cells were evaluated. Expression of stimulated by RA 6 (STRA6), CRABP2, and FABP5 was determined by real-time PCR and Western blotting. Effects of simvastatin were also evaluated in a nude mouse model of human endometriosis.

RESULTS

Simvastatin potentiated an inhibitory effect of RA on growth of HES cells. In HES cells, simvastatin induced expression of STRA6 and CRABP2 but not FABP5. Similarly, simvastatin treatment of nude mice bearing human endometrial xenografts led to an increased expression of CRABP2 and STRA6 proteins in ectopic lesions.

CONCLUSIONS

Simvastatin interacts with the RA system, inducing the expression of the key protein regulating the uptake of retinol (STRA6) and the expression of apoptosis-promoting CRABP2. These effects may contribute to cooperative apoptosis-inducing effects of simvastatin and RA and support the examination of these compounds in the treatment of endometriosis.

Molecular pathways: current role and future directions of the retinoic acid pathway in cancer prevention and treatment

Retinoids and their naturally metabolized and synthetic products (e.g., all-trans retinoic acid, 13-cis retinoic acid, bexarotene) induce differentiation in various cell types. Retinoids exert their actions mainly through binding to the nuclear retinoic acid receptors (α, β, γ), which are transcriptional and homeostatic regulators with functions that are often compromised early in neoplastic transformation. The retinoids have been investigated extensively for their use in cancer prevention and treatment. Success has been achieved with their use in the treatment of subtypes of leukemia harboring chromosomal translocations. Promising results have been observed in the breast cancer prevention setting, where fenretinide prevention trials have provided a strong rationale for further investigation in young women at high risk for breast cancer. Ongoing phase III randomized trials investigating retinoids in combination with chemotherapy in non-small cell lung cancer aim to definitively characterize the role of retinoids in this tumor type. The limited treatment success observed to date in the prevention and treatment of solid tumors may relate to the frequent epigenetic silencing of RARβ. Robust evaluation of RARβ and downstream genes may permit optimized use of retinoids in the solid tumor arena.

ATRA inhibits the proliferation of DU145 prostate cancer cells through reducing the methylation level of HOXB13 gene

All-trans retinoic acid (ATRA) has been widely investigated for treatments of many cancers including prostate cancer. HOXB13, silenced in androgen receptor-negative (AR(-)) prostate cancer cells, plays a role in AR(-) prostate cancer cell growth arrest. In this study we intended to elucidate the mechanisms that are involved in the proliferation inhibition of AR(-) prostate cancer cells triggered by ATRA. We discovered that ATRA was able to induce the growth arrest and to increase HOXB13 expression in AR(-) prostate cancer cells. Both EZH2 and DNMT3b participated in the repression of HOXB13 expression through an epigenetic mechanism involving DNA and histone methylation modifications. Specifically, EZH2 recruited DNMT3b to HOXB13 promoter to form a repression complex. Moreover, ATRA could upregulate HOXB13 through decreasing EZH2 and DNMT3b expressions and reducing their interactions with the HOXB13 promoter. Concurrently, the methylation level of the HOXB13 promoter was reduced upon the treatment of ATRA. Results from this study implicated a novel effect of ATRA in inhibition of the growth of AR(-) resistant human prostate cancer cells through alteration of HOXB13 expression as a result of epigenetic modifications.

Genome-wide transcriptional profiling analysis of all trans retinoic acid-treated tongue carcinoma SCC-9 cells

BACKGROUND

All trans retinoic acid (ATRA) is used as standard of care in promyelocytic leukemia. Not much is known about the gene expression profile in ATRA-treated tongue cancer cells. We performed a genome-wide transcriptional profiling of ATRA-treated tongue cancer cells to understand the pathways that mediate ATRA action in tongue cancer.

METHODS

We measured the effects of ATRA on the proliferation of SCC-9 human tongue carcinoma cells. The differential gene expression profile was measured by microarray analysis of untreated and ATRA-treated cells and expression of key genes was validated by real-time RT-PCR.

RESULTS

ATRA treatment (24 and 48 hr) significantly inhibited SCC-9 cell proliferation in a dose-dependent manner. SCC-9 cells treated for 48 hr with ATRA showed upregulation of 276 genes, including ANGPTL4, GDF15, ICAM1 and TUSC4, and downregulation of 43 genes, including CXCL10. Validation by real-time PCR showed a significant upregulation of intracellular adhesion molecule 1 (ICAM1) and downregulation of CXCL10 and IL32.

CONCLUSIONS

ATRA had an anti-tumor effect in tongue cancer cells. This effect is likely mediated via upregulation of ICAM1 and downregulation of CXCL10 and IL32.

ATRA in combination with nedaplatin inhibits cell proliferation but promotes apoptosis in human hepatoma cell line Huh-7

AIM: To observe the effects of all-trans retinoic acid (ATRA) and nedaplatin, alone or in combination, on cell proliferation and apoptosis in human hepatoma cell line Huh-7, and to determine whether the two drugs in combination have a synergistic effect in treating hepatocarcinoma.

METHODS: After Huh-7 cells were incubated with different concentrations of ATRA (10^-4, 10^-5 and 10^-6 mol/L) and nedaplatin (1, 2 and 5 mg/L), alone or in combination, for 24, 48 and 72 h, cell morphology changes were observed using an inverted microscope; cell proliferation was evaluated by MTT assay; and apoptosis was evaluated by flow cytometry.

RESULTS: Both ATRA and nedaplatin could markedly inhibit cell proliferation in a time- and concentration-dependent manner (all P < 0.01). ATRA and nedaplatin in combination had a significant synergistic effect on cell proliferation compared with ATRA or nedaplatin alone (both P < 0.01). Both ATRA and nedaplatin promoted the apoptosis of Huh-7 cells. The apoptosis rate was significantly lower in Huh-7 cells treated with ATRA and nedaplatin alone for 48 h than in those treated with the two drugs in combination (28.49% ± 0.6%, 42.57% ± 1.03% vs 55.35% ± 1.30%, both P < 0.01), suggesting a synergistic effect of combined nedaplatin and ATRA on the apoptosis of Huh-7 cells.

CONCLUSION: Both ATRA and nedaplatin can inhibit cell proliferation and promote apoptosis in human hepatoma cell line Huh-7. ATRA combined with nedaplatin has a significant synergistic effect on the proliferation and apoptosis of Huh-7 cells.

Enhancing cytotoxic and apoptotic effect in OVCAR-3 and MDAH-2774 cells with all-trans retinoic acid and zoledronic acid: a paradigm of synergistic molecular targeting treatment for ovarian cancer

Background

Ovarian cancer is the most fatal gynecologic malignancies in the world. Although, platinum based treatments are widely used, the disease becomes treatment refractory within two years, and novel treatment options should be searched. All- trans retinoic acid (ATRA) induces growth arrest, differentiation and cell death in some types of cancer cells and its combination with various anticancer agents results in enhanced cytotoxicity. Zoledronic acid is a common bisphosphonate known for its anticancer effects beyond its current use in the treatment of cancer-induced bone disease. We aimed to investigate the possible additive/synergistic effect of both agents in OVCAR-3 and MDAH-2774 ovarian cancer cell lines, since both agents show superiority to conventional cytotoxics in terms of adverse events.

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. OligoGeArray^® which consists of 112 apoptosis related genes was used to elucidate the genetic changes within cancer cells. To validate our oligoarray results, quantitative real-time PCR was performed on four selected genes that were maximally effected by the combination treatment: lymphotoxin beta receptor (LTBR), myeloid cell leukemia-1 (MCL-1), tumor necrosis factor receptor superfamily, member 1A (TNFRSF1A), TNFRSF1A-associated death domain protein (TRADD).

Results

We demonstrated that a novel combination of ATRA and zoledronic acid is a strong inducer of apoptotic related cell death in both ovarian cancer cells. While the combination therapy significantly induced proapoptotic genes such as tumor necrosis factor receptor superfamily (TNFRSF), TRADD and caspase 4, some of the antiapoptotic genes such as members of MCL-1, LTBR, BAG3 and Bcl-2 family members were inhibited.

Conclusions

These are the preliminary molecular results of a novel combination treatment of ATRA and zoledronic acid, with fewer side effects as compared to conventional cytotoxic agents. With additional experimental analysis, it may serve as a good option for the treatment of refractory and elderly ovarian cancer patients, for whom there exists very limited choice of treatment.

Randomized Phase II Trial of All-Trans-Retinoic Acid With Chemotherapy Based on Paclitaxel and Cisplatin As First-Line Treatment in Patients With Advanced Non–Small-Cell Lung Cancer

Purpose

This randomized phase II trial evaluated whether the combination of cisplatin and paclitaxel (PC) plus all-trans retinoic acid (ATRA) increases response rate (RR) and progression-free survival (PFS) in patients with advanced non–small-cell lung cancer (NSCLC) with an acceptable toxicity profile and its association with the expression of retinoic acid receptor beta 2 (RAR-β2) as a response biomarker.

Patients and Methods

Patients with stages IIIB with pleural effusion and IV NSCLC were included to receive PC, and randomly assigned to receive ATRA 20 mg/m2/d (RA/PC) or placebo (P/PC) 1 week before treatment until two cycles were completed. RAR-β2 expression was analyzed in tumor and adjacent lung tissue.

Results

One hundred seven patients were included, 55 in the P/PC group and 52 in the RA/PC group. RR for RA/PC was 55.8% (95% CI, 46.6% to 64.9%) and for P/PC, 25.4% (95% CI, 21.3 to 29.5%; P = .001). The RA/PC group had a longer median PFS (8.9 v 6.0 months; P = .008). Multivariate analysis of PFS showed significant differences for the RA/PC group (hazard ratio, 0.62; 95% CI, 0.4 to 0.95). No significant differences in toxicity grade 3/4 were found between groups, except for hypertriglyceridemia (10% v 0%) in RA/PC (P = .05). Immunohistochemistry and reverse-transcriptase polymerase chain reaction assays showed expression of RAR-β2 in normal tissues of all tumor samples, but only 10% of samples in the tumor tissue.

Conclusion

Adding ATRA to chemotherapy could increase RR and PFS in patients with advanced NSCLC with an acceptable toxicity profile. A phase III clinical trial is warranted to confirm these findings.

Expression of Survivin, COX-2 and VEGF in colorectal cancer and its correlation with tumor angiogenesis

AIM: To simultaneously detect the expression of Survivin, cyclooxygenasa-2 (COX-2), vascular endothelial growth factor (VEGF) and CD34 in colorectal cancer and explore its correlation with tumor angiogenesis.

METHODS: All specimens (including 26 colorectal cancer specimens, 10 colorectal polyp specimens and 7 chronic colitis specimens) were collected from September 2007 to May 2008 at the Second Affiliated Hospital of Harbin Medical University. All specimens were pathologically reevaluated to confirm the initial diagnosis. The expression of Survivin, COX-2, VEGF and CD34 in these specimens was detected by immunohistochemistry.

RESULTS: The positive rates of Survivin, COX-2 and VEGF proteins in colorectal cancer tissue were 76.9%, 80.8% and 69.28% respectively, significantly higher than those in colorectal polyp and chronic colitis tissues (P < 0.01 or 0.05). The microvascular density (MVD) revealed by CD-34 immunostaining in colorectal cancer tissue was significantly higher than that in colorectal polyp and chronic colitis tissues (23.69 ± 9.96 vs 13.10 ± 7.05 and 10.43 ± 4.24, both P < 0.01). Furthermore, the expression of Survivin, COX-2 and VEGF proteins in colorectal cancer tissue is positively correlated with tumor microvessel count (all P < 0.05). In colorectal cancer tissue, the expression of Survivin was closely correlated with that of COX-2 and VEGF (χ² = 11.18, 4.72, P < 0.05).

CONCLUSION: Survivin is probably able to promote tumor angiogenesis through regulating the expression of COX-2 and VEGF in colorectal cancer.