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).     

Phenylbutyrate-induced apoptosis and differential expression of Bcl-2, Bax, p53 and Fas in human prostate cancer cell lines

OBJECTIVE: To assess the mechanisms of action of phenylbutyrate (PB), an investigational chemotherapeutic agent for prostate cancer (PCa), in apoptosis induction in PCa cell lines in vitro. STUDY DESIGN: We analyzed the differential expression of different apoptosis modulators, Bcl-2, Bax, p53 and Fas, for their potential role in PB-induced apoptosis using relative quantitative flow cytometry (FCM). Both androgen-dependent (LNCaP) and androgen-independent (C-4-2, PC-3-PF and DU145) human PCa cell lines were examined. RESULTS: PB induced apoptosis in PCa cell lines in a dose-dependent manner. Fifty percent apoptosis could be induced by 5-10 mM PB. Bcl-2 was down-regulated 30-75% and the Bax:Bcl-2 ratio elevated in apoptotic PCa cell lines regardless of their androgen dependency or p53 status. FCM revealed a heterogeneous stimulatory effect on the expression of Bax and Bcl-2 in PC3-PF cells at 0.5-2.5 mM PB. In a p53-positive cell line (DU145), p53 was repressed by 70% and Fas elevated sixfold with 10 mM PB. CONCLUSION: Our data show that PB-induced PCa apoptosis is associated with the relative repression of Bcl-2 and with up-regulation of Bax and Fas proteins and that this PB-induced apoptosis is independent of p53 and androgen-dependency status of PCa cell lines.     

Cadmium induces p53-dependent apoptosis in human prostate epithelial cells

Cadmium, a widespread toxic pollutant of occupational and environmental concern, is a known human carcinogen. The prostate is a potential target for cadmium carcinogenesis, although the underlying mechanisms are still unclear. Furthermore, cadmium may induce cell death by apoptosis in various cell types, and it has been hypothesized that a key factor in cadmium-induced malignant transformation is acquisition of apoptotic resistance. We investigated the in vitro effects produced by cadmium exposure in normal or tumor cells derived from human prostate epithelium, including RWPE-1 and its cadmium-transformed derivative CTPE, the primary adenocarcinoma 22Rv1 and CWR-R1 cells and LNCaP, PC-3 and DU145 metastatic cancer cell lines. Cells were treated for 24 hours with different concentrations of CdCl(2) and apoptosis, cell cycle distribution and expression of tumor suppressor proteins were analyzed. Subsequently, cellular response to cadmium was evaluated after siRNA-mediated p53 silencing in wild type p53-expressing RWPE-1 and LNCaP cells, and after adenoviral p53 overexpression in p53-deficient DU145 and PC-3 cell lines. The cell lines exhibited different sensitivity to cadmium, and 24-hour exposure to different CdCl(2) concentrations induced dose- and cell type-dependent apoptotic response and inhibition of cell proliferation that correlated with accumulation of functional p53 and overexpression of p21 in wild type p53-expressing cell lines. On the other hand, p53 silencing was able to suppress cadmium-induced apoptosis. Our results demonstrate that cadmium can induce p53-dependent apoptosis in human prostate epithelial cells and suggest p53 mutation as a possible contributing factor for the acquisition of apoptotic resistance in cadmium prostatic carcinogenesis.     

Regulation of prostate cancer cell division by glucose

Previous studies have shown that rapid cell proliferation is associated with elevated glucose consumption. However, those studies did not establish whether glucose is required for prostate cancer cell proliferation or define the molecular mechanisms by which glucose regulates cell division. We addressed these issues by studying two metastatic human prostate cancer cell lines: DU145, which is androgen independent and highly proliferative; and LNCaP, which is androgen dependent and relatively slow growing. We found that proliferation of DU145 cells was significantly inhibited by reduction of glucose in the medium to 0.5 g/L, which is half the physiologic concentration, whereas LNCaP cells grew at control rates even in the presence of only 0.05 g/L glucose. Glucose deprivation of DU145 cells caused a 90% reduction in DNA synthesis; a 10–20-fold reduction in cyclins D and E and CDK4 levels; and cell cycle arrest in G₀-G₁. However, glucose deprivation did not cause global inhibition of protein synthesis, since mutant p53 levels increased in glucose-deprived DU145 cells. This observed increase in mutant p53 levels was not associated with a rise in p21 levels. Glucose deprivation of DU145 cells also led to apparent dephosphorylation of mutant retinoblastoma (RB) protein. We conclude that: 1) high levels of glucose consumption are required for rapid proliferation of androgen-independent prostate cancer cells, 2) glucose may not be required for slow growth of androgen-dependent prostate cancer cells, and 3) glucose promotes passage of cells through early G₁ by increasing the expression of several key cell cycle regulatory proteins that normally inhibit RB function. J. Cell. Physiol. 180:431–438, 1999. © 1999 Wiley-Liss, Inc.     

Lycopene and the LXRα agonist T0901317 synergistically inhibit the proliferation of androgen-independent prostate cancer cells via the PPARγ-LXRα-ABCA1 pathway

In our previous study, we demonstrated that lycopene can inhibit the proliferation of androgen-dependent prostate LNCaP cancer cells through the activation of the peroxisome proliferator-activated receptor gamma (PPARγ)-liver X receptor alpha (LXRα)-ATP-binding cassette transporter 1 (ABCA1) pathway. However, it is still unclear whether lycopene possesses similar effects in androgen-independent prostate cancer cells DU145 and PC-3. As lycopene inhibited the proliferation of both cell types to a similar extent, we chose DU145 cells for most of the subsequent studies. We show that lycopene significantly increased protein and mRNA expression of PPARγ, LXRα and ABCA1 and cholesterol efflux (i.e., decreased cellular cholesterol and increased cholesterol in culture medium). Lycopene (10 μM) in the presence of a specific antagonist of PPARγ (GW9662) or of LXRα (GGPP) restored the proliferation of DU145 cells and significantly suppressed lycopene-induced protein and mRNA expression of PPARγ and LXRα and cholesterol efflux. Liver X receptor α knockdown by siRNA against LXRα significantly promoted the proliferation of DU145 cells, whereas si-LXRα knockdown followed by incubation with lycopene (10 μM) restored the proliferation to the control level. Furthermore, lycopene in combination with the LXRα agonist T0901317 exhibited synergistic effects on cell proliferation and protein expression of PPARγ, LXRα and ABCA1. These results demonstrate that lycopene can inhibit DU145 cell proliferation via PPARγ-LXRα-ABCA1 pathway and that lycopene and T0901317 exhibit synergistic effects.     

miR-182在前列腺癌组织中的表达及其对前列腺癌细胞增殖和凋亡的影响

目的:观察前列腺癌组织及不同前列腺癌细胞系中miR-182的表达,并探讨下调其表达对前列腺癌细胞增殖和凋亡的影响及机制。方法:采用实时荧光定量PCR(q RT-PCR)检测30例前列腺癌组织和30例相应的癌旁组织以及前列腺正常上皮RWPE-1细胞、前列腺癌PC-3、LNCa P和DU145细胞中miR-182的表达,进一步采用Lipfectamine 2000脂质体转染miRNA-182 inhibitor和阴性对照miRNA于PC-3细胞后,通过噻唑蓝(MTT)比色法检测细胞增殖情况,流式细胞术检测细胞凋亡率,免疫印迹(Western blot)法检测转录因子FOXO1、血管内皮生长因子(VEGF)和抑癌基因p53蛋白的表达。结果:miR-182在前列腺癌组织中的表达明显高于癌旁组织(P0.05);miR-182在前列腺癌细胞系PC-3、LNCa P和DU145中的表达均高于前列腺正常上皮细胞RWPE-1(P0.05),其中PC-3细胞中miR-182表达水平最高。转染miRNA-182 inhibitor至PC-3细胞成功下调miR-182表达后,细胞的增殖能力明显受到抑制,细胞凋亡能力明显增强,FOXO1表达水平显著升高,VEGF和p53的表达明显降低,差异均具有统计学意义(P0.05)。结论:miR-182在前列腺癌组织及细胞中呈高表达,下调miR-182的表达可能通过增加FOXO1的表达并减少VEGF和p53的表达,抑制前列腺癌细胞增殖并诱导细胞凋亡。     

mRNA Expression Profiles for Prostate Cancer following Fractionated Irradiation Are Influenced by p53 Status

We assessed changes in cell lines of varying p53 status after various fractionation regimens to determine if p53 influences gene expression and if multifractionated (MF) irradiation can induce molecular pathway changes. LNCaP (p53 wild-type), PC3 (p53 null), and DU145 (p53 mutant) prostate carcinoma cells received 5 and 10 Gy as single-dose (SD) or MF (0.5 Gy × 10, 1 Gy × 10, and 2 Gy × 5) irradiation to simulate hypofractionated and conventionally fractionated prostate radiotherapies, respectively. mRNA analysis revealed 978 LNCaP genes differentially expressed (greater than two-fold change, P < .05) after irradiation. Most were altered with SD (69%) and downregulated (75%). Fewer PC3 (343) and DU145 (116) genes were induced, with most upregulated (87%, 89%) and altered with MF irradiation. Gene ontology revealed immune response and interferon genes most prominently expressed after irradiation in PC3 and DU145. Cell cycle regulatory (P = 9.23 × 10^-73, 14.2% of altered genes, nearly universally downregulated) and DNA replication/repair (P = 6.86 × 10^-30) genes were most prominent in LNCaP. Stress response and proliferation genes were altered in all cell lines. p53-activated genes were only induced in LNCaP. Differences in gene expression exist between cell lines and after varying irradiation regimens that are p53 dependent. As the duration of changes is ≥24 hours, it may be possible to use radiation-inducible targeted therapy to enhance the efficacy of molecular targeted agents.     

CCR2 expression correlates with prostate cancer progression

Although the primary role of chemokines and their receptors is controlling the trafficking of leukocytes during inflammatory responses, they also play pleoitropic roles in cancer development. There is emerging evidence that cancer cells produce chemokines that induce tumor cell proliferation or chemotaxis in various cancer types. We have previously reported that MCP-1 acts as a paracrine and autocrine factor for prostate cancer (PCa) growth and invasion. As the cellular effects of MCP-1 are mediated by CC chemokine receptor 2 (CCR2), we hypothesized that CCR2 may contribute PCa progression. Accordingly, we first determined CCR2 mRNA and protein expression in various cancer cell lines, including PCa and other cancer types. All cells expressed CCR2 mRNA and protein, but in PCa, more aggressive cancer cells such as C4-2B, DU145, and PC3 expressed a higher amount of CCR2 compared with the less aggressive cancer cells such as LNCaP or non-neoplastic PrEC and RWPE-1 cells. Further, we found a positive correlation between CCR2 expression and PCa progression by analyzing an ONCOMINE gene array database. We confirmed that CCR2 mRNA was highly expressed in PCa metastatic tissues compared with the localized PCa or benign prostate tissues by real-time RT-PCR. Finally, CCR2 protein expression was examined by immunohistochemical staining on tissue microarray specimens from 96 PCa patients and 31 benign tissue controls. We found that CCR2 expression correlated with Gleason score and clinical pathologic stages, whereas lower levels of CCR2 were expressed in normal prostate tissues. These results suggest that CCR2 may contribute to PCa development.     

Fractionated Radiation Alters Oncomir and Tumor Suppressor miRNAs in Human Prostate Cancer Cells

We have previously demonstrated that prostate carcinoma cells exposed to fractionated radiation differentially expressed more genes compared to single-dose radiation. To understand the role of miRNA in regulation of radiation-induced gene expression, we analyzed miRNA expression in LNCaP, PC3 and DU145 prostate cancer cells treated with single-dose radiation and fractionated radiation by microarray. Selected miRNAs were studied in RWPE-1 normal prostate epithelial cells by RT-PCR. Fractionated radiation significantly altered more miRNAs as compared to single-dose radiation. Downregulation of oncomiR-17-92 cluster was observed only in the p53 positive LNCaP and RWPE-1 cells treated with single-dose radiation and fractionated radiation. Comparison of miRNA and mRNA data by IPA target filter analysis revealed an inverse correlation between miR-17-92 cluster and several targets including TP53INP1 in p53 signaling pathway. The base level expressions of these miRNAs were significantly different among the cell lines and did not predict the radiation outcome. Tumor suppressor miR-34a and let-7 miRNAs were upregulated by fractionated radiation in radiosensitive LNCaP (p53 positive) and PC3 (p53-null) cells indicating that radiation-induced miRNA expression may not be regulated by p53 alone. Our data support the potential for using fractionated radiation to induce molecular targets and radiation-induced miRNAs may have a significant role in predicting radiosensitivity.     

Genistein Inhibits Prostate Cancer Cell Growth by Targeting miR-34a and Oncogenic HOTAIR

Objective

Genistein is a soy isoflavone that has antitumor activity both in vitro and in vivo. It has been shown that genistein inhibits many type of cancers including prostate cancer (PCa) by regulating several cell signaling pathways and microRNAs (miRNAs). Recent studies suggest that the long non-coding RNAs (lncRNAs) are also involved in many cellular processes. At present there are no reports about the relationship between gensitein, miRNAs and lncRNAs. In this study, we focused on miRNAs, lncRNA that are regulated by genistein and investigated their functional role in PCa.

Method

Microarray (SurePrint G3 Human GE 8×60K) was used for expression profiling of genistein treated and control PCa cells (PC3 and DU145). Functional assay (cell proliferation, migration, invasion, apoptosis and cell cycle assays) were performed with the PCa cell lines, PC3 and DU145. Both in vitro and in vivo (nude mouse) models were used for growth assays. Luciferase reporter assays were used for binding of miR-34a to HOTAIR.

Results

LncRNA profiling showed that HOTAIR was highly regulated by genistein and its expression was higher in castration-resistant PCa cell lines than in normal prostate cells. Knockdown (siRNA) of HOTAIR decreased PCa cell proliferation, migration and invasion and induced apoptosis and cell cycle arrest. miR-34a was also up-regulated by genistein and may directly target HOTAIR in both PC3 and DU145 PCa cells.

Conclusions

Our results indicated that genistein inhibited PCa cell growth through down-regulation of oncogenic HOTAIR that is also targeted by tumor suppressor miR-34a. These findings enhance understanding of how genistein regulates lncRNA HOTAIR and miR-34a in PCa.     

Androgen and taxol cause cell type-specific alterations of centrosome and DNA organization in androgen-responsive LNCaP and androgen-independent DU145 prostate cancer cells

We investigated the effects of androgen and taxol on the androgen-responsive LNCaP and androgen-independent DU145 prostate cancer cell lines. Cells were treated for 48 and 72 h with 0.05-1 nM of the synthetic androgen R1881 and with 100 nM taxol. Treatment of LNCaP cells with 0.05 nM R1881 led to increased cell proliferation, whereas treatment with 1 nM R1881 resulted in inhibited cell division, DNA cycle arrest, and altered centrosome organization. After treatment with 1 nM R1881, chromatin became clustered, nuclear envelopes convoluted, and mitochondria accumulated around the nucleus. Immunofluorescence microscopy with antibodies to centrosomes showed altered centrosome structure. Although centrosomes were closely associated with the nucleus in untreated cells, they dispersed into the cytoplasm after treatment with 1 nM R1881. Microtubules were only faintly detected in 1 nM R1881-treated LNCaP cells. The effects of taxol included microtubule bundling and altered mitochondria morphology, but not DNA organization. As expected, the androgen-independent prostate cancer cell line DU145 was not affected by R1881. Treatment with taxol resulted in bundling of microtubules in both cell lines. Additional taxol effects were seen in DU145 cells with micronucleation of DNA, an indication of apoptosis. Simultaneous treatment with R1881 and taxol had no additional effects on LNCaP or DU145 cells. These results suggest that LNCaP and DU145 prostate cancer cells show differences not only in androgen responsiveness but in sensitivity to taxol as well.     

Downregulation of PTEN/MMAC/TEP1 expression in human prostate cancer cell line DU145 by growth stimuli

Genetic alterations and/or deletion of the tumor suppressor gene PTEN/MMAC/TEP1 occur in many types of human cancer including prostate cancer. We describe the production of monoclonal antibody against recombinant human PTEN and the study of PTEN gene and protein expression in three commercially available human prostate cancer cell lines, PC-3, LNCaP, and DU 145. Northern blotting analyses showed that LNCaP and DU145 but not PC-3 cells expressed PTEN mRNA. However, Western blotting analyses using a monoclonal antibody against PTEN demonstrated the expression of PTEN protein in DU145 but not LNCaP cells. In DU145 cells, PTEN expression at both the mRNA and protein levels inversely correlated with serum concentrations and levels of PKB/Akt phosphorylation. In addition, the basal activity of PKB/Akt as indicated by level of phosphorylation was higher in prostate cancer cells which do not express PTEN than that in the cells expressing wild type PTEN. Thus, PTEN may play a critical role in regulating cellular signaling in prostate cancer cells.     

Long noncoding RNA MALAT1 enhances the docetaxel resistance of prostate cancer cells via miR‐145‐5p‐mediated regulation of AKAP12

Our present work was aimed to study on the regulatory role of MALAT1/miR‐145‐5p/AKAP12 axis on docetaxel (DTX) sensitivity of prostate cancer (PCa) cells. The microarray data (GSE33455) to identify differentially expressed lncRNAs and mRNAs in DTX‐resistant PCa cell lines (DU‐145‐DTX and PC‐3‐DTX) was retrieved from the Gene Expression Omnibus (GEO) database. QRT‐PCR analysis was performed to measure MALAT1 expression in DTX‐sensitive and DTX‐resistant tissues/cells. The human DTX‐resistant cell lines DU145‐PTX and PC3‐DTX were established as in vitro cell models, and the expression of MALAT1, miR‐145‐5p and AKAP12 was manipulated in DTX‐sensitive and DTX‐resistant cells. Cell viability was examined using MTT assay and colony formation methods. Cell apoptosis was assessed by TUNEL staining. Cell migration and invasion was determined by scratch test (wound healing) and Transwell assay, respectively. Dual‐luciferase assay was applied to analyse the target relationship between lncRNA MALAT1 and miR‐145‐5p, as well as between miR‐145‐5p and AKAP12. Tumour xenograft study was undertaken to confirm the correlation of MALAT1/miR‐145‐5p/AKAP12 axis and DTX sensitivity of PCa cells in vivo. In this study, we firstly notified that the MALAT1 expression levels were up‐regulated in clinical DTX‐resistant PCa samples. Overexpressed MALAT1 promoted cell proliferation, migration and invasion but decreased cell apoptosis rate of PCa cells in spite of DTX treatment. We identified miR‐145‐5p as a target of MALAT1. MiR‐145‐5p overexpression in PC3‐DTX led to inhibited cell proliferation, migration and invasion as well as reduced chemoresistance to DTX, which was attenuated by MALAT1. Moreover, we determined that AKAP12 was a target of miR‐145‐5p, which significantly induced chemoresistance of PCa cells to DTX. Besides, it was proved that MALAT1 promoted tumour cell proliferation and enhanced DTX‐chemoresistance in vivo. There was an lncRNA MALAT1/miR‐145‐5p/AKAP12 axis involved in DTX resistance of PCa cells and provided a new thought for PCa therapy.     

Apolipoprotein C1 promotes prostate cancer cell proliferation in vitro

Here, we aimed to investigate the carcinogenic effects of apolipoprotein C1 (APOC1) in prostate cancer (PCa). APOC1 expression was evaluated in PCa and normal prostate specimens, and lentivirus‐mediated RNA interference was used to knockdown APOC1 in DU145 cells. The effects of APOC1 silencing on cell proliferation, cell cycle arrest, and apoptosis were assessed. APOC1 expression was much higher in PCa tissues than in normal tissues. Moreover, APOC1 silencing inhibited cell proliferation and colony formation, arrested cell cycle progression, and enhanced apoptosis in DU145 cells. Additionally, APOC1 silencing decreased survivin, phospho‐Rb, and p21 levels and increased cleaved caspase‐3 expression. These data supported the procarcinogenic effects of APOC1 in the pathogenesis of PCa and suggested that targeting APOC1 may have applications in the treatment of PCa.     

The COX-2 inhibitor Celecoxib enhances the sensitivity of KB/VCR oral cancer cell lines to Vincristine by down-regulating P-glycoprotein expression and function

Previous studies have indicated that long-term chemotherapy decreases the sensitivity of oral cancer cells to chemotherapeutics while simultaneously increasing resistance to these drugs. COX-2 inhibitors are known to enhance the toxic action of anti-tumor drugs against cancer cells. Using the MTT method, we investigated the influence of the COX-2 selective inhibitor Celecoxib on the proliferation of KB/VCR oral cancer cell lines and analyzed the effect of Celecoxib on the regulation of P-glycoprotein (P-gp) expression and function. Western blot analysis was employed to detect the expression of P-gp, and flow cytometry was used to evaluate P-gp function by detecting the accumulation of the active P-gp functional fluorescence substrate within KB/VCR cells. The results revealed that a low dose of Celecoxib (10 μmol/L) showed no growth inhibitory effects on KB/VCR cell lines. When the concentration of Celecoxib was greater than or equal to 20 μmol/L, the inhibitory effect on KB/VCR cells was significantly enhanced in a time- and dose-dependent manner. The lower dose of Celecoxib (10 μmol/L) significantly enhanced the toxicity of Vincristine (VCR) against KB/VCR cell lines. After the application of Celecoxib plus VCR (10 μmol/L+1.5μmol/L, respectively) treatment for 24, 48 or 72 h, the growth inhibition rates of KB/KBV cells were 37.82 ± 1.60%, 47.84 ± 1.29% and 54.43 ± 2.35%, respectively, which were significantly higher than the rates in the cells treated only with Celecoxib (10 μmol/L) or VCR (1.5 μmol/L) (all P<0.01). P-gp expression levels in KB/KBV cells treated with Celecoxib plus VCR (10 μmol/L+1.5 μmol/L, respectively) were markedly lower than the levels in control cells and those treated with VCR (1.5 μmol/L) (all P<0.01). In addition, the intensity of Rho123 fluorescence of KB/KBV cells in cells treated with Celecoxib plus VCR (10 μmol/L+1.5 μmol/L, respectively) or Celecoxib alone (10 μmol/L) was significantly higher than the intensity observed in control cells and those treated with VCR alone (1.5 μmol/L) (all P<0.01). The underlying mechanism of these phenomena is likely correlated with the down-regulation of the expression and function of P-gp due to Celecoxib, thereby increasing the amount of VCR accumulated in KB/VCR cells.