Cytotoxicity In Prostate Cancer Cells Research Articles

Paradoxical and contradictory effects of imatinib in two cell line models of hormone-refractory prostate cancer.

Imatinib mesylate is a chemotherapeutic drug that inhibits the tyrosine kinase activity of c-KIT and has been successfully used to treat leukemias and some solid tumors. However, its application for treatment of hormone-refractory prostate cancer (HRPC) has shown modest effectiveness and did not follow the outcomes in cultured cells or animal models. Moreover, the molecular pathways by which imatinib induces cytotoxicity in prostate cancer cells are poorly characterized. Two cell line models of HRPC (DU145 and PC3) were exposed to 20 μM of imatinib for 6-72 hr. MTS assay was used to assess cell viability during the course of experiment. Gene expression analysis of c-KIT, cell-cycle and apoptosis regulators, and angiogenic factors was determined by means of real-time PCR, western blot, and/or immunocytochemistry. The enzymatic activity of the apoptosis effector, caspase-3, was determined by a colorimetric assay. Imatinib significantly decreased the viability of DU145 cells but paradoxically augmented the viability of PC3 cells. DU145 cells displayed diminished expression of anti-apoptotic Bcl-2 protein and augmented levels of caspase-8 and -9, as well as, increased enzymatic activity of caspase-3 in response to imatinib. No differences existed on the expression levels of apoptosis-related proteins in PC3 cells treated with imatinib, though the activity of caspase-3 was decreased. The mRNA levels of angiogenic factor VEGF were decreased in DU145-treated cells, whereas an opposite effect was seen in PC3. In addition, it was shown that DU145 and PC3 cells present a differential expression of c-KIT protein variants. DU145 and PC3 cells displayed a contradictory behavior in response to imatinib, which was underpinned by a distinct expression pattern (or activity) of target regulators of cell-cycle, apoptosis, and angiogenesis. The paradoxical effect of imatinib in PC3 cells may be related with the differential expression of c-KIT protein variants. Moreover, the present findings helped to understand the discrepancies in the efficacy of imatinib as therapeutic option in HRPC.

Bioassay guided identification of small chaperone proteins α-crystallin and Hsp27 inhibitors from Copaiba oil

Over-expression of small chaperone proteins in cancer tissue contributes to the resistance of chemotherapy. Targeting these small chaperones including α-crystallin and heat shock protein 27 (Hsp27) is a promising strategy for cancer treatment. Hardwickiic acid (HA), a clerodane diterpenoid from Copaiba oil has been reported to inhibit Hsp27. We expect to identify new small chaperone inhibitors from Copaiba oil that is abundant of diterpenoids. In the current study, cytotoxicity and anti-chaperone assay guided isolation of Copaiba oil led to two major fractions (non-acidic and acidic components) and seven sub-fractions from the acidic components. The non-acidic components and one sub-fraction showed significant cytotoxicity in prostate cancer cells. Four sub-fractions exhibited potent anti-chaperone activity. Three chemical components were identified from these sub-fractions including copalic acid, hardwickiic acid and 3-acetoxycopalic acid. All three compounds inhibited the chaperone activities of α-crystallin and Hsp27. In addition, these compounds enhanced the anti-proliferative activity of the chemotherapeutic agent carboplatin in LNCaP cells. 3-Acetoxycopalic acid slightly decreased the level of Hsp27 client protein signal transducer and activator of transcription 3 (Stat3) in PC3 cells. Overall, several diterpenoids were identified to be small chaperone inhibitors and could be used as lead compounds for the development of more potent derivatives.

Mitochondrial protein cyclophilin-D-mediated programmed necrosis attributes to berberine-induced cytotoxicity in cultured prostate cancer cells

The prostate cancer is one of the leading causes of men’s cancer mortality. The development of alternative chemotherapeutic strategies is urgent. Berberine has displayed significant anti-prostate cancer activities. The underlying mechanisms are not fully understood. In the current study, we found that berberine induced apoptosis and programmed necrosis in cultured prostate cancer cells (LNCaP and PC-82 lines), and necrosis weighted more than apoptosis in contributing berberine’s cytotoxicity. We demonstrated that mitochondrial protein cyclophilin-D (Cyp-D) is required for berberine-induced programmed necrosis. Inhibition of Cyp-D by its inhibitors cyclosporin A (CSA) or sanglifehrin A (SFA), and by Cyp-D shRNA depletion alleviated berberine-induced prostate cancer cell necrosis (but not apoptosis). Our data found that in prostate cancer cells, berberine induced reactive oxygen species (ROS) production, which dictated P53 translocation to mitochondria, where it physically interacted with Cyp-D to open mitochondrial permeability transition pore (mPTP). The anti-oxidant N-acetylcysteine (NAC), the P53 inhibitor pifithrin-α (PFTα) as well as P53 siRNA knockdown suppressed berberine-induced P53 mitochondrial translocation and Cyp-D association, thus inhibiting mitochondrial membrane potential (MMP) decrease and prostate cancer cell necrosis. In summary, the results of the present study provide mechanistic evidence that both apoptosis and programmed necrosis attribute to berberine’s cytotoxicity in prostate cancer cells.

Caffeic acid phenethyl ester synergistically enhances docetaxel and paclitaxel cytotoxicity in prostate cancer cells

Evidence is growing for the beneficial role of selective estrogen receptor modulators (SERM) in prostate diseases. Caffeic acid phenethyl ester (CAPE) is a promising component of propolis that possesses SERM activity. This study aimed at investigating the modulatory impact of CAPE on docetaxel (DOC) and paclitaxel (PTX) cytotoxicity in prostate cancer cells and exploring the possible underlying mechanisms for this chemomodulation. CAPE significantly increased DOC and PTX potency in PC-3, DU-145 and LNCaP prostate cancer cells. Combination index calculations showed synergistic interaction of CAPE/DOC and CAPE/PTX cotreatments in all the tested cell lines. Subsequent mechanistic studies in PC-3 cells indicated that cyclin D1 and c-myc were significantly reduced in the combined treatment groups with concurrent increase in p27kip. DNA-ploidy analysis indicated a significant increase in the percentage of cells in pre-G1 in CAPE/DOC and CAPE/PTX cotreatments. Decreased Bcl-2/Bax ratio together with increased caspase-3 activity and protein abundance were observed in the same groups. Estrogen receptor-β (ER-β) and its downstream tumor suppressor forkhead box O1 levels were significantly elevated in CAPE and combination groups compared to DOC or PTX-alone. ER-α and insulin-like growth factor-1 receptor protein abundance were reduced in the same groups. CAPE significantly reduced AKT, ERK and ER-α (Ser-167) phosphorylation in PC-3 cells. CAPE-induced inhibition of AKT phosphorylation was more prominent (1.7-folds higher) in cells expressing ER-α such as PC-3 compared to LNCaP. In conclusion, CAPE enhances the antiproliferative and cytotoxic effects of DOC and PTX in prostate cancer cells. This can be, at least partly, attributed to CAPE augmentation of DOC and PTX proapoptotic effects in addition to CAPE-induced alterations in ER-α and ER-β abundance.

A novel mechanism of methylglyoxal cytotoxicity in prostate cancer cells

Methylglyoxal is one of the most powerful glycating agents of proteins and other important cellular components and has been shown to be toxic to cultured cells. Methylglyoxal cytotoxicity appears to occur through cell-cycle arrest but, more often, through induction of apoptosis. In this study we examined whether, and through which molecular mechanism, methylglyoxal affects the growth of poorly aggressive LNCaP and invasive PC3 human prostate cancer cells, where its role has not been exhaustively investigated yet. We demonstrated that methylglyoxal is cytotoxic on LNCaP and PC3 and that such cytotoxicity occurs not via cell proliferation but apoptosis control. Moreover, we demonstrated that methylglyoxal cytotoxicity, potentiated by the silencing of its major scavenging enzyme Glyoxalase I, occurred via different apoptotic responses in LNCaP and PC3 cells that also showed a different susceptibility to this metabolite. Finally, we showed that the observed methylglyoxal apoptogenic role involved different molecular pathways, specifically mediated by methylglyoxal or methylglyoxal-derived argpyrimidine intracellular accumulation and NF-kB signaling-pathway. In particular, in LNCaP cells, methylglyoxal, through the accumulation of argpyrimidine, desensitized the key cell survival NF-kB signaling pathway, which was consistent with the modulation of NF-kB-regulated genes, triggering a mitochondrial apoptotic pathway. The results suggest that this physiological compound merits investigation as a potential chemo-preventive/-therapeutic agent, in differently aggressive prostate cancers.

Pharmacological ascorbate induces cytotoxicity in prostate cancer cells through ATP depletion and induction of autophagy

Recent studies have revealed the scientific basis for the use of intravenous (i.v.) vitamin C or ascorbic acid (ascorbate) in treating cancers, and raised the possibility of using i.v. ascorbate as a prooxidant anticancer therapy. Through the production of H2O2, pharmacologic ascorbate can induce some cancer cell death in vitro and inhibit a number of types of tumor growth in animal models. However, the mechanism of cell death triggered by ascorbate is not well understood. In this study, we investigated the cytotoxicity of pharmacological concentrations of ascorbate to human prostate cancer cells and the mechanisms involved. The results showed that ascorbate in the millimolar range induced cytotoxicity in five of the six tested prostate cancer cell lines. The IC50 values in the sensitive prostate cancer cells ranged from 1.9 to 3.5 mmol/l, concentrations clinically achievable with i.v. ascorbate use. All tested androgen-independent cells were sensitive to ascorbate treatment. The ascorbate-insensitive cell line LaPC4 is hormonally dependent. Whereas the reasons for sensitivity/resistance to ascorbate treatment need to be investigated further, cell death in sensitive cells was dependent on H2O2. Ascorbate treatment depleted ATP and induced autophagy in sensitive prostate cancer cells, resulting in cell death. Taken together with previous studies, high-dose ascorbate has the potential to be a novel treatment option to hormone-refractory prostate cancer.

Development of Cerium Oxide Nanoparticles and Its Cytotoxicity in Prostate Cancer Cells

+� oxide nanoparticles was produced by hydrothermal method and ceric (3 + � oxide nanoparticles were produced by hydrolysis method. The different synthesis routes adopted helped in synthesizing nanoparticles of similar size but exhibiting different properties. Detailed characterization of the nanoparticles proved that the synthesized cerium oxide nanoparticles were different in their stoichiometry. The selective toxicity of cerium oxide towards the normal and the cancer cell lines was evaluated. The nanoparticles were found to be nontoxic towards normal cell lines (L929) but cytotoxic towards prostate cancer cell lines (PC-3) as analyzed by MTT assay. Cellular uptake was confirmed by the conjugation of cerium oxide nanoparticle with a fluorescent dye rhodamine- 123 followed by optical detection of the uptake.

Ethanolic extract of Brazilian green propolis sensitizes prostate cancer cells to TRAIL-induced apoptosis

Prostate cancer represents an ideal disease for chemopreventive intervention. Propolis possesses immuno-modulatory, anti-tumour and chemopreventive properties. The tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is an important endogenous anti-cancer agent that induces apoptosis selectively in tumour cells. However, some cancer cells are resistant to TRAIL-mediated apoptosis. Naturally occurring phenolic and polyphenolic compounds sensitize TRAIL-resistant cancer cells and augment the apoptotic activity of TRAIL. The ethanolic extract of Brazilian green propolis (EEP) is rich in phenolic components. Our in vitro results indicate the potential targets in the TRAIL-induced apoptotic pathway for the cancer chemopreventive activity of Brazilian propolis. We examined the cytotoxic and apoptotic effects of Brazilian EEP and its bioactive components in combination with TRAIL on LNCaP prostate cancer cells. The chemical composition of Brazilian green propolis was determined by high performance liquid chromatography-diode array detection. The cytotoxicity was measured by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl-tetrazolium and lactate dehydrogenase assays. Apoptosis was detected using annexin V-FITC by flow cytometry and fluorescence microscopy. The mitochondrial membrane potential (∆Ψm) was evaluated using DePsipher staining by fluorescence microscopy. Flow cytometry was used to analyse death receptor (TRAIL-R1 and TRAIL-R2) expression in LNCaP cells. The inhibition of nuclear factor-κB (NF-κB) (p65) activation in cancer cells was confirmed by the ELISA-based TransAM NF-κB kit. The LNCaP cells were shown to be resistant to TRAIL-induced apoptosis. Our study demonstrates that EEP sensitizes TRAIL-resistant prostate cancer cells. The main phenolic components detected in Brazilian green propolis are artepillin C, quercetin, kaempferol and p-coumaric acid. Brazilian propolis and its bioactive components markedly augmented TRAIL-mediated apoptosis and cytotoxicity in prostate cancer cells. Brazilian EEP enhanced the expression of TRAIL-R2 and the activity of NF-κB in LNCaP cells. The co-treatment of prostate cancer cells with 100 ng/ml TRAIL and 50 µg/ml EEP increased the percentage of apoptotic cells to 65.8 ± 1.2% and caused a significant disruption of ∆Ψm in LNCaP cells. We show that Brazilian EEP helped cells overcome TRAIL resistance by engaging both intrinsic and extrinsic apoptotic pathways and regulating NF-κB activity. The data demonstrate the important role of Brazilian green propolis and its bioactive compounds in prostate cancer chemoprevention through the enhancement of TRAIL-mediated apoptosis.

Enhanced TRAIL-mediated apoptosis in prostate cancer cells by the bioactive compounds neobavaisoflavone and psoralidin isolated from Psoralea corylifolia

Numerous compounds detected in medical plants and dietary components or supplements possess chemopreventive, antitumor and immunomodulatory properties. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an important endogenous anticancer factor that induces apoptosis selectively in cancer cells. However, some tumor cells are resistant to TRAIL-mediated apoptosis. Naturally occurring agents could sensitize TRAIL-resistant cancer cells and augment their apoptotic activity. We examined the cytotoxic and apoptotic effects of neobavaisoflavone and psoralidin in combination with TRAIL on LNCaP prostate cancer cells. The cytotoxicity was evaluated by MTT and LDH assays. The apoptosis was detected using Annexin V-FITC by flow cytometry and fluorescence microscopy. The LNCaP cells were shown to be resistant to TRAIL-induced apoptosis. Our study demonstrated that neobavaisoflavone and psoralidin sensitized TRAIL-resistant cells and markedly augmented TRAIL-mediated apoptosis and cytotoxicity in prostate cancer cells. Cotreatment of LNCaP cells with 100ng/ml TRAIL and 50µM neobavaisoflavone or 50µM psoralidin increased the percentage of the apoptotic cells to 77.5 ± 0.5% or 64.4 ± 0.5%, respectively. The data indicate the potential role of the bioactive compounds isolated from the medicinal plant Psoralea corylifolia (neobavaisoflavone and psoralidin) in prostate cancer chemoprevention through enhancement of TRAIL-mediated apoptosis.

ID1 Enhances Docetaxel Cytotoxicity in Prostate Cancer Cells through Inhibition of p21

To identify potential mechanisms underlying prostate cancer chemotherapy response and resistance, we compared the gene expression profiles in high-risk human prostate cancer specimens before and after neoadjuvant chemotherapy and radical prostatectomy. Among the molecular signatures associated with chemotherapy, transcripts encoding inhibitor of DNA binding 1 (ID1) were significantly upregulated. The patient biochemical relapse status was monitored in a long-term follow-up. Patients with ID1 upregulation were found to be associated with longer relapse-free survival than patients without ID1 increase. This in vivo clinical association was mechanistically investigated. The chemotherapy-induced ID1 upregulation was recapitulated in the prostate cancer cell line LNCaP. Docetaxel dose-dependently induced ID1 transcription, which was mediated by ID1 promoter E-box chromatin modification and c-Myc binding. Stable ID1 overexpression in LNCaP increased cell proliferation, promoted G(1) cell cycle progression, and enhanced docetaxel-induced cytotoxicity. These changes were accompanied by a decrease in cellular mitochondria content, an increase in BCL2 phosphorylation at serine 70, caspase-3 activation, and poly(ADP-ribose) polymerase cleavage. In contrast, ID1 siRNA in the LNCaP and C42B cell lines reduced cell proliferation and decreased docetaxel-induced cytotoxicity by inhibiting cell death. ID1-mediated chemosensitivity enhancement was in part due to ID1 suppression of p21. Overexpression of p21 in LNCaP-ID1-overexpressing cells restored the p21 level and reversed ID1-enhanced chemosensitivity. These molecular data provide a mechanistic rationale for the observed in vivo clinical association between ID1 upregulation and relapse-free survival. Taken together, it shows that ID1 expression has a novel therapeutic role in prostate cancer chemotherapy and prognosis.

Curcumin-Induced Apoptosis in PC3 Prostate Carcinoma Cells Is Caspase-Independent and Involves Cellular Ceramide Accumulation and Damage to Mitochondria

Curcumin, the principal curcuminoid of tumeric, has potent anticancer activity. To determine the mechanism of curcumin-induced cytotoxicity in prostate cancer cells, we exposed PC3 prostate carcinoma cells to 25 to 100 μ M curcumin for 24 to 72 h. Curcumin treatment of PC3 cells caused time- and dose-dependent induction of apoptosis and depletion of cellular reduced glutathione (GSH). Exogenous GSH and its precursor N-acetyl-cysteine, but not ascorbic acid (AA) or ebselen, decreased curcumin accumulation in PC3 cells and also prevented curcumin-induced DNA fragmentation. The failure of AA and ebselen to protect PC3 cells from curcumin-induced apoptosis argued against the involvement of reactive oxygen species; rather, GSH-mediated inhibition of curcumin-induced cytotoxicity was due to reduced curcumin accumulation in PC3 cells. Curcumin-treated PC3 cells showed apoptosis-inducing cellular ceramide accumulation and activation of p38 mitogen-activated protein kinase (MAPK) and c-jun N-terminal kinase (JNK). Caspase-3, caspase-8, and caspase-9 were activated, and cytochrome c and apoptosis-inducing factor (AIF) were released from mitochondria following curcumin treatment. Interestingly, curcumin-induced apoptosis was not prevented by p38 MAPK, JNK, or caspase inhibition. We conclude that curcumin-induced cytotoxicity was due to cellular ceramide accumulation and damage to mitochondria that resulted in apoptosis mediated by AIF and other caspase-independent processes.

BASIC SCIENCE Isoflavones augment the effect of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) on prostate cancer cells

Introduction. Isoflavones are the subclass of flavonoids with chemopreventive and anticancer activities. Isoflavones induce cytotoxicity and apoptosis in prostate cancer cells. TRAIL plays an important role in immune surveillance and the defense mechanism against tumor cells. However, not all tumor cells are sensitive to TRAIL. TRAIL-resistant cancer cells can be sensitized to TRAILinduced apoptosis by flavonoids. We investigated the effect of TRAIL in combination with isoflavones on prostate cancer cells. Materials and methods. The LNCaP human prostate cancer cells were incubated with TRAIL and/or isoflavones (daidzein, puerarin, ipriflavone, genistein, neobavaisoflavone, and biochanin-A). Cytotoxicity was determined by MTT and LDH assays. results. Our study confirmed that LNCaP prostate cancer cells were resistant to TRAIL. We therefore examined the cytotoxic effect of TRAIL in combination with isoflavones on LNCaP cells. We showed for the first time that tested isoflavones markedly augmented TRAIL mediated cytotoxicity against prostate cancer cells. The strongest cytotoxic effect in combination with TRAIL was exhibited by neobavaisoflavone and biochanin-A. Co-treatment of prostate cancer cells with TRAIL and isoflavones, especially neobavaisoflavone and biochanin-A significantly sensitized LNCaP cells to TRAIL induced cytotoxicity. Conclusion. The tested isoflavones augmented the cytotoxic effect of TRAIL on LNCaP cells. The obtained results suggest that isoflavones supported TRAIL-induced cytotoxicity in prostate cancer cells and thus they might be a promising chemopreventive strategy in prostate cancer.

Chalcones Enhance TRAIL-Induced Apoptosis in Prostate Cancer Cells

Chalcones exhibit chemopreventive and antitumor effects. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a naturally occurring anticancer agent that induces apoptosis in cancer cells and is not toxic to normal cells. We examined the cytotoxic and apoptotic effect of five chalcones in combination with TRAIL on prostate cancer cells. The cytotoxicity was evaluated by the MTT and LDH assays. The apoptosis was determined using flow cytometry with annexin V-FITC. Our study showed that all five tested chalcones: chalcone, licochalcone-A, isobavachalcone, xanthohumol, butein markedly augmented TRAIL-mediated apoptosis and cytotoxicity in prostate cancer cells and confirmed the significant role of chalcones in chemoprevention of prostate cancer.

Abstract C13: Ascorbate induces cytotoxicity in prostate cancer cells through an autophagy pathway

Abstract Ascorbate (Vitamin C) has been shown to act as a pro-oxidant agent under pharmacological concentrations, and thus can cause cancer cell death in vitro and inhibit tumor growth in animal models, through formation of H2O2. The cell death mechanisms induced by ascorbate need to be further elaborated. The goal of our study was to determine whether ascorbate is cytotoxic to prostate cancer cells and if so, to determine the mechanism of ascorbate-induced cytotoxicity. We hypothesized that through generation of H2O2, pharmacological concentrations of ascorbate can deplete prostate cancer cell ATP and cause cell death through autophagy pathway. A panel of prostate cancer cell lines PC-3, LNCap, C4-2, LaPC4 and 22RV1 were incubated with millimolar range of ascorbate for two hours. Then ascorbate was washed out and cells were incubated in fresh media for 24 hrs before cell viability was assessed. Cell ATP levels were determined by HPLC. The results showed that 4 out of the 5 tested cell lines have IC50s < 5 mM, while the most resistant cell line LaPC4 has IC50 at 12 mM. Addition of catalase - a H2O2 scavenger to the culture media, completely protected the cells from the death caused by ascorbate, confirming the death is mediated by H2O2. PC-3 cell ATP levels significantly decreased after 2 hrs of incubation with 5 mM ascorbate, and did not recover over the following 24 hrs. To determine if ascorbate induced autophagy, western blot of PC-3 cells for LC3 was performed. The results showed an increase of LC3-II form at 2 hrs of ascorbate treatment, indicating the processing of LC3 protein to its lipidated form. At 24 hrs the LC3-II bands were decreased, which may due to degradation of LC3 proteins at the autophagosomes. We also generated cells (PC3-LC3G) that express a fusion protein of LC-3 and GFP. The GFP-LC3 protein punctation were observed at 4 hrs of ascorbate treatment, indicating a translocation of LC3 to the autophagic membranes. These results suggest that ascorbate induces cytotoxicity in prostate cancer cells through depletion of cell ATP and induction of autophagy. To further confirm this pathway, an autophagy inhibitor 3-MA is under testing, the degradation of GFP-LC3 is also under analysis to determine whether ascorbate increases the autophagic flux. Also, to confirm the role of ATP drop in ascorbate-induced autophagy, 3-aminibenzamide (3AB) and 4-hydroxyquinazoline (4HQ) are being used to prevent the drop in ATP level. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C13.

Estrogen effects on tubulin expression and taxane mediated cytotoxicity in prostate cancer cells

The present study was designed to determine if estrogens change microtubule polymerization and modulate cell cycle progression in vitro, related to modulation of tubulin expression and to determine if estrogens had antagonistic or synergistic effects with microtubule active agents. cDNA array analysis of LNCaP cells treated with the estrogens, estradiol, estrone, diethylstilbestrol (DES), and 2-methoxyestradiol (2-ME) was carried out and the results confirmed by PCR and Western blotting. Microtubule arrays in cells treated with estrogens were assessed using indirect immunofluorescence. The effects of combining estrogens with taxane was assessed by MTT assay and flow cytometry for cell cycle kinetics. Human prostate cancer xenografts were treated with DES and docetaxel to assess the effects of combining estrogens and taxane in vivo. Treatment of LNCaP cells with DES and 2-ME suppressed transcripts and protein for beta-tubulin isotype IVa. This effect on tubulin synthesis was not blocked by estrogen or androgen receptor modulators. Other estrogens had no effect on beta-tubulin expression. 2-ME and DES decreased the density of microtubules. The administration of DES or 2-ME with paclitaxel enhanced cytotoxicity and G(2)-M arrest in vitro. DES enhanced tumor suppression in a human prostate cancer xenograft model when combined with the taxane docetaxel. The use of DES and 2-ME enhances the effects of taxanes and may be a novel and important means of increasing therapeutic efficacy of cytotoxic chemotherapy against prostate carcinoma.

Discovery of 2-Arylthiazolidine-4-carboxylic Acid Amides as a New Class of Cytotoxic Agents for Prostate Cancer

To improve the selectivity and antiproliferative activity of previously reported serine amide phosphates (SAPs), we designed a new series of 4-thiazolidinone amides, in which the 4-thiazolidinone moiety was introduced as a phosphate mimic. However, these 4-thiazolidinone derivatives demonstrated less cytotoxicity in prostate cancer cells despite improved selectivity over RH7777 cells. To further optimize the thiazolidinone analogues in terms of cytotoxicity and selectivity, we made closely related structural modifications, which led us to the discovery of a new class of 2-arylthiazolidine-4-carboxylic acid amides. These compounds were potent cytotoxic agents with IC(50) values in the low micromolar concentration range and demonstrated enhanced selectivity in receptor-negative cells compared to SAPs and 4-thiazolidinone amides.

Effects of quercetin on the heat-induced cytotoxicity of prostate cancer cells.

It has been demonstrated that prostate cancer cells are relatively sensitive to heat stress. We have reported that heat treatment at 43 degrees C increases the expression of heat shock protein 70 (hsp70) in prostate cancer cells, leading to apoptosis. Hsp70 is a protein that protects cells against heat damage. Cells with lower levels of hsp70 have been shown to have a higher sensitivity to heat stress. Therefore, downregulation of hsp70 is expected to enhance heat-induced inhibitory effects on cell growth. Quercetin has been reported to be an agent that inhibits hsp70 expression. The present study was undertaken to investigate the effects of quercetin and/or heat on the growth of prostate cancer cells in vitro. Three human prostate cancer cell lines were used: Lncap; PC-3; and JCA-1. The cells were treated with quercetin and/or heat. Alterations in the cell cycle and hsp70 expression were examined by means of flow cytometry (FCM). The apoptotic cells were detected by FCM using fluorescein isothiocyanate (FITC) labeled annexin V. Treatment with quercetin alone resulted in an apparent decrease of hsp70-positive cells and an increase of subG1 cells in JCA-1 and LNcap cells. Quercetin inhibited an increase of hsp70 expression after heat treatment and increased the number of subG1 cells with lower levels of hsp70 in JCA-1 and LNcap cells. Quercetin was found to enhance heat-induced inhibitory effects on cell growth and heat-induced apoptosis in both JCA-1 and LNcap cells. These results suggest that quercetin may enhance heat-induced cytotoxicity in prostate cancer cell lines through the inhibition of hsp70 production.

β-Lapachone-Induced Apoptosis in Human Prostate Cancer Cells: Involvement of NQO1/xip3

β-Lapachone (β-lap) induces apoptosis in various cancer cells, and its intracellular target has recently been elucidated in breast cancer cells. Here we show that NAD(P)H:quinone oxidoreductase (NQO1/xip3) expression in human prostate cancer cells is a key determinant for apoptosis and lethality after β-lap exposures. β-Lap-treated, NQO1-deficient LNCaP cells were significantly more resistant to apoptosis than NQO1-expressing DU-145 or PC-3 cells after drug exposures. Formation of an atypical 60-kDa PARP cleavage fragment in DU-145 or PC-3 cells was observed after 10 μM β-lap treatment and correlated with apoptosis. In contrast, LNCaP cells required 25 μM β-lap to induce similar responses. Atypical PARP cleavage in β-lap-treated cells was not affected by 100 μM zVAD-fmk; however, coadministration of dicoumarol, a specific inhibitor of NQO1, reduced β-lap-mediated cytotoxicity, apoptosis, and atypical PARP cleavage in NQO1-expressing cells. Dicoumarol did not affect the more β-lap-resistant LNCaP cells. Stable transfection of LNCaP cells with NQO1 increased their sensitivity to β-lap, enhancing apoptosis compared to parental LNCaP cells or vector-alone transfectants. Dicoumarol increased survival of β-lap-treated NQO1-expressing LNCaP transfectants. NQO1 activity, therefore, is a key determinant of β-lap-mediated apoptosis and cytotoxicity in prostate cancer cells.

Anticancer Drug-Induced Apoptosis and Cytotoxicity in Prostate Cancer Cells Are Modulated by Organ-Specific Stromal Cell Factors.

INTRODUCTION. Most anticancer drugs kill tumor cells by inducing apoptotic cell death [1]. Enhancement of this apoptosis-inducing activity or overcoming tumor's resistance to apoptosis induction by anticancer drugs could bring a significant improvement in cancer therapy. Cytokines and tissue-specific factors mediate communication between tumor cells and surrounding stromal cells [2,3]. These agents are believed also to modulate tumor cells' response to anti-cancer drugs. This phenomenon is predominantly acute in metastatic prostate cancer, where most patients with metastatic disease survive less than 3 years. The purpose of this study was to examine the impact of stromal cells (fibroblast and endothelial cells)-induced cytokines on the response of tumor cells to anticancer drugs.