Apoptosis In LNCaP Cells Research Articles

Abstract 272: Metformin enhances the anti-prostate cancer activity of abiraterone and enzalutamide

Abstract The standard treatment for advanced castration sensitive prostate cancer (CSPC) is androgen deprivation therapy (ADT), generally in the form of suppression of gonadally produced androgens via medical or surgical castration. The selective inhibitor of androgen biosynthesis Abiraterone (Abi), and the androgen receptor (AR) antagonist Enzalutamide (MDV3100), are second line hormonal therapies used to treat PC patients failing ADT. However, these drugs provide treatment response for a limited duration of time due to the development of resistance to them. Included among the mechanisms leading to resistance to ABI or MDV is the expression of the AR variant AR-V7. Metformin, a widely used oral anti-diabetic drug, has been reported to reduce prostate cancer mortality in PC patients with type II diabetes. In this study, we explored the effects of ABI, MDV and metformin in a pre-clinical model of PC. Both Abi and MDV inhibited cell proliferation and the expression of prostate specific antigen (PSA) in androgen-sensitive LNCaP cells. However, neither induced cell death, and in fact MDV appeared to actually inhibit apoptosis in LNCaP cells. Both agents increased AR and AR-V7 expression, which in part may account for development of resistance to ABI or MDV. In contrast, metformin inhibited AR, AR-V7 and PSA expression in a dose-dependent manner, and induced apoptotic cell death in PC cells. Metformin, in combination with ABI or MDV, further enhanced apoptosis and inhibited expression of PSA than it did as single agent. Interestingly, at near physiological concentrations metformin induced apoptosis in a caspase-independent manner rather than by a caspase-dependent apoptotic program that is reported to occur with high doses of metformin. In conclusion, Abi or MDV inhibits AR signaling and PC cell proliferation, but also induces AR and AR-V7 expression. Metformin decreases AR and AR-V7 expression and induces apoptotic cell death. The combination of metformin with androgen biosynthesis/AR inhibitors results in caspase-independent apoptotic cell death in addition to inhibition of both cell proliferation and AR signaling. Further studies will be needed to evaluate the clinical efficacy of these combination treatments in patients with PC. Citation Format: Yi Xie, Linbo Wang, Arif Hussain. Metformin enhances the anti-prostate cancer activity of abiraterone and enzalutamide. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 272.

Enhancement of Genistein-Induced Apoptosis in LNCaP Prostate Cancer cells

This study determined the impact of vitamin C dosage on genistein-induced apoptosis in LNCaP cancer cells in vitro at various treatment regimens. Although the linear regression of viability assay (MTT) indicated a p-value = 0.11; NBT assay reveal a declining SOD activity during cell death. Apoptosis induction was the main mode of treatment induced cell death. The overall data showed the trend of treatment efficacy as; (Gen 10uM + Vit C 40uM) > (Gen 30uM + Vit C 40uM) > (Gen 70uM + Vit C 40uM) >10uM genistein > 70uM genistein. The chi-square test for comparing necrosis, apoptosis, and live cells showed that Vitamin C could impact genistein-induced apoptosis in LNCaP cells (p = 0.0003). This study forms basis for in vivo studies of the impact of vitamin C on genistein-induced apoptosis in LNCaP prostate cancer cells.

Effects of a novel carbocyclic analog of pyrrolo[2,3-d]pyrimidine nucleoside on pleiotropic induction of cell death in prostate cancer cells with different androgen responsiveness.

Prostate cancer is the most frequently diagnosed cancer and is one of the leading causes of male cancer death in the world. Recently, in the course of our screening for a novel anticancer compound, we synthesized carbocyclic analogs of pyrrolo[2,3-d]pyrimidine nucleoside; compounds 5, and 6. In the current study, we report the effects of compound 5 on pleiotropic induction of cell death via up-regulation of AR-associated p21(Cip1) protein in prostate cancer cells with different androgen responsiveness, such as LNCaP (androgen-dependent and -sensitive), LNCaP(C4-2) (androgen-independent and -sensitive; androgen-refractory), and DU145 (androgen-independent and -insensitive) cells. The treatment of LNCaP cells with 6 μM compound 5 for 24 h stimulated the androgen receptor (AR) activity and dramatically up-regulated transcription (56-fold) of p21(Cip1), which, in turn, induces typical apoptosis in the cells. However, induction of apoptosis through up-regulation (23-fold) of AR-associated p21(Cip1) achieved in LNCaP(C4-2) cells was possible by intensive cell treatment with compound 5 (9 μM, 48 h), because the cells are less sensitive and independent to androgen than LNCaP cells. Furthermore, 6 μM compound 5-treated DU145 cells, which exhibit extremely low AR activation due to no androgen responsiveness and dependency, showed neither up-regulation of p21(Cip1) nor apoptotic induction. Instead, a different type of cell death, autophagy-like death through the LC3B-associated autophagosome formation, was obviously induced in DU145 cells. Taken together, our results suggest that pleiotropic induction of prostate cancer cell death by compound 5 is determined by how efficiently and how abundantly androgen-dependent activation of the AR occurs, whereas compound 6 shows no induction of apoptosis in LNCaP cells.

Combined Treatment with Exendin-4 and Metformin Attenuates Prostate Cancer Growth.

IntroductionRecently, the pleiotropic benefits of incretin-based therapy have been reported. We have previously reported that Exendin–4, a glucagon-like peptide–1 (GLP–1) receptor agonist, attenuates prostate cancer growth. Metformin is known for its anti-cancer effect. Here, we examined the anti-cancer effect of Exendin–4 and metformin using a prostate cancer model.MethodsProstate cancer cells were treated with Exendin–4 and/or metformin. Cell proliferation was quantified by growth curves and 5-bromo–2′-deoxyuridine (BrdU) assay. TUNEL assay and AMP-activated protein kinase (AMPK) phosphorylation were examined in LNCaP cells. For in vivo experiments, LNCaP cells were transplanted subcutaneously into the flank region of athymic mice, which were then treated with Exendin–4 and/or metformin. TUNEL assay and immunohistochemistry were performed on tumors.ResultsExendin–4 and metformin additively decreased the growth curve, but not the migration, of prostate cancer cells. The BrdU assay revealed that both Exendin–4 and metformin significantly decreased prostate cancer cell proliferation. Furthermore, metformin, but not Exendin–4, activated AMPK and induced apoptosis in LNCaP cells. The anti-proliferative effect of metformin was abolished by inhibition or knock down of AMPK. In vivo, Exendin–4 and metformin significantly decreased tumor size, and further significant tumor size reduction was observed after combined treatment. Immunohistochemistry on tumors revealed that the P504S and Ki67 expression decreased by Exendin–4 and/or metformin, and that metformin increased phospho-AMPK expression and the apoptotic cell number.ConclusionThese data suggest that Exendin–4 and metformin attenuated prostate cancer growth by inhibiting proliferation, and that metformin inhibited proliferation by inducing apoptosis. Combined treatment with Exendin–4 and metformin attenuated prostate cancer growth more than separate treatments.

Efficacious delivery of protein drugs to prostate cancer cells by PSMA-targeted pH-responsive chimaeric polymersomes

Protein drugs as one of the most potent biotherapeutics have a tremendous potential in cancer therapy. Their application is, nevertheless, restricted by absence of efficacious, biocompatible, and cancer-targeting nanosystems. In this paper, we report that 2-[3-[5-amino-1-carboxypentyl]-ureido]-pentanedioic acid (Acupa)-decorated pH-responsive chimaeric polymersomes (Acupa-CPs) efficiently deliver therapeutic proteins into prostate cancer cells. Acupa-CPs had a unimodal distribution with average sizes ranging from 157–175nm depending on amounts of Acupa. They displayed highly efficient loading of both model proteins, bovine serum albumin (BSA) and cytochrome C (CC), affording high protein loading contents of 9.1–24.5wt.%. The in vitro release results showed that protein release was markedly accelerated at mildly acidic pH due to the hydrolysis of acetal bonds in the vesicular membrane. CLSM and MTT studies demonstrated that CC-loaded Acupa10-CPs mediated efficient delivery of protein drugs into PSMA positive LNCaP cells leading to pronounced antitumor effect, in contrast to their non-targeting counterparts and free CC. Remarkably, granzyme B (GrB)-loaded Acupa10-CPs caused effective apoptosis of LNCaP cells with a low half-maximal inhibitory concentration (IC50) of 1.6nM. Flow cytometry and CLSM studies using MitoCapture™ revealed obvious depletion of mitochondria membrane potential in LNCaP cells treated with GrB-loaded Acupa10-CPs. The preliminary in vivo experiments showed that Acupa-CPs had a long circulation time with an elimination phase half-life of 3.3h in nude mice. PSMA-targeted, pH-responsive, and chimaeric polymersomes have appeared as efficient protein nanocarriers for targeted prostate cancer therapy.

Delivery of retinoic acid to LNCap human prostate cancer cells using solid lipid nanoparticles

In this study retinoic acid (RTA) loaded solid lipid nanoparticles (SLNs) were optimized by tuning the process parameters (pressure/temperature) and using different lipids to develop nanodispersions with enhanced anticancer activity. The RTA-SLN dispersions were produced by high-pressure homogenization and characterized in terms of particle size, zeta potential, drug entrapment efficiency, stability, transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and in vitro drug release. Thermal and X-ray analysis showed the RTA to be in the amorphous state, whilst microscopic images revealed a spherical shape and uniform particle size distribution of the nanoparticles. Anticancer efficiency was evaluated by incubating RTA-SLNs with human prostate cancer (LNCap) cells, which demonstrated reduced cell viability with increased drug concentrations (9.53% at 200ug/ml) while blank SLNs displayed negligible cytotoxicity. The cellular uptake of SLN showed localization within the cytoplasm of cells and flow cytometry analysis indicated an increase in the fraction of cells expressing early apoptotic markers, suggesting that the RTA loaded SLNs are able to induce apoptosis in LNCap cells. The RTA-SLN dispersions have the potential to be used for prostate anticancer treatment.

Induction of apoptosis in prostate cancer cells by the novel ceramidase inhibitor ceranib-2.

Ceramidases are key enzymes that decrease ceramide levels in cells. A reduction in ceramide concentration impairs ceramide signalling, and results in apoptosis resistance in cancer cells. This study investigates the potential for ceranib-2, a novel ceramidase inhibitor, to affect the survival and/or promote apoptosis of prostate cancer cells (LNCaP and DU145) in vitro. Cell viability was determined using MTT, and apoptosis assessed via flow cytometry. We examined structural changes with both confocal and transmission electron microscopes. Ceranib-2 concentrations of 0.1, 1, 5, 10, 25 and 50μM were applied to LNCaP and DU145 cell lines. The corresponding reduction in LNCaP cell viability (against the control) was 84%, 80%, 64%, 56%, 40% and 15% after 24h, and 81%, 74%, 60%, 55%, 27% and 11% after 48h. For DU145 cells, viability was reduced to 84%, 82%, 63%, 50%, 41% and 18% after 24h, and 64%, 42%, 30%, 20%, 8% and 5% after 48h. Following treatment with 25 and 50μM ceranib-2, the respective observed rates of early apoptosis in LNCaP cells were 23% and 36% after 24h and 27% and 58% after 48h. The morphological and ultrastructural signs of apoptosis detected were fragmented nuclei, chromatin condensations and cytoskeleton laceration. The inhibitory effects of ceranib-2 on prostate cancer cell survival are dose and time dependent. For LNCaP cells, ceranib-2 toxicity was predominately apoptotic in nature, while for DU145 cells, cell death may be related to non-apoptotic mechanisms.

Abstract B51: The tyrphostin, NT157, suppresses insulin receptor substrates and augments therapeutic response of prostate cancer

Abstract Insulin-like growth factor (IGF) signaling is associated with castrate-resistant prostate cancer (CRPC) progression. Insulin receptor substrates 1 and 2 (IRS1/2) mediate mitogenic and anti-apoptotic signaling from IGF-1 receptor (IGF-1R), insulin receptor and other oncoproteins. This study demonstrates that IRS1/2 expression is increased in PCa and, persists in CRPC. Furthermore, this study assesses the anti-cancer activity of NT157, a small-molecule tyrphostin targeting IRS proteins, using androgen-responsive (LNCaP) and -independent (PC3) prostate cancer cells in vitro and in vivo. NT157 treatment resulted in dose-dependent inhibition of IGF1R activation, suppression of IRS protein expression, inhibition of IGF-1-induced AKT activation, but increased ERK activation in NT157-treated cells in vitro. These effects were correlated with decreased proliferation and increasing apoptosis of LNCaP cells and increasing G2M arrest in PC3 cells. NT157 also suppressed androgen-responsive growth, delayed CRPC progression of LNCaP xenografts and suppressed PC3 tumor growth alone and in combination with docetaxel. This study reports the first preclinical proof-of-principle data that this novel small-molecule tyrosine kinase inhibitor targeting human IRS suppresses IRS1/2 expression, delays CRPC progression, and suppresses growth of CRPC tumors in vitro and in vivo. Demonstration that IRS expression can be increased in response to a variety of stressors that may lead to resistance or reduced effect of the therapies indicate that NT157-mediated IRS1/2 down-regulation is a novel therapeutic approach for management of advanced prostate cancer. Citation Format: Naokazu Ibuki, Mazyar Ghaffari, Hadas Reuveni, Mitali Pandey, Ladan Fazli, Haruhito Azuma, Martin E. Gleave, Alexander Levitzki, Michael E. Cox. The tyrphostin, NT157, suppresses insulin receptor substrates and augments therapeutic response of prostate cancer. [abstract]. In: Proceedings of the AACR Special Conference: Targeting the PI3K-mTOR Network in Cancer; Sep 14-17, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(7 Suppl):Abstract nr B51.

Assessment of the anticancer mechanism of ferulic acid via cell cycle and apoptotic pathways in human prostate cancer cell lines.

Studies on genetic changes underlying prostate cancer and the possible signaling pathways are getting increased day by day, and new treatment methods are being searched for. The aim of the present study is to investigate the effects of ferulic acid (FA), a phenolic compound, on cell cycle, apoptosis, invasion, and colony formation in the PC-3 and LNCaP prostate cancer cells. The effect of FA on cell viability was determined via a 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) method. Total RNA was isolated with Tri Reagent. Expression of 84 genes for both cell cycle and apoptosis separately was evaluated by reverse transcriptase PCR (RT-PCR). Protein expressions were evaluated by Western blot analysis. Furthermore, apoptotic effects of FA were observed with terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling (TUNEL) assay. Effects of FA on cell invasion and colony formation were determined using Matrigel chamber and colony assay, respectively. The half maximal inhibitory concentration (IC50) dose of FA was found to be 300 μM in PC-3 cells and 500 μM in LNCaP cells. According to RT-PCR results, it was observed that FA inhibited cell proliferation by increasing the gene expressions of ATR, ATM, CDKN1A, CDKN1B, E2F4, RB1, and TP53 and decreasing the gene expressions of CCND1, CCND2, CCND3, CDK2, CDK4, and CDK6 in PC-3 cells. On the other hand, it was seen that FA suppressed cell proliferation by increasing in the gene expressions of CASP1, CASP2, CASP8, CYCS, FAS, FASLG, and TRADD and decreasing in the gene expressions of BCL2 and XIAP in LNCaP cells. In this study, protein expression of CDK4 and BCL2 genes significantly decreased in these cells. It could induce apoptosis in PC-3 and LNCaP cells. Also, it was observed that FA suppressed the invasion in PC-3 and LNCaP cells. Moreover, it suppressed the colony formation. In conclusion, it has been observed that FA may lead to cell cycle arrest in PC-3 cells while it may cause apoptosis in LNCaP cells.

Combining paclitaxel with ABT-263 has a synergistic effect on paclitaxel resistant prostate cancer cells.

We assessed the capability of paclitaxel, one of the taxanes, to induce death in two prostate cancer lines, LNCaP and PC3. Paclitaxel drove an apoptotic pathway in LNCaP, but not in PC3 cells, in response to G2/M arrest. An examination of the levels of anti-apoptotic proteins revealed that Bcl-xl was much higher in PC3 cells than in LNCaP cells and Bcl2 could be detected only in PC3 cells, not in LNCaP cells. Knocking down Bcl-xl enhanced paclitaxel-induced apoptosis in LNCaP cells, while we were unable to knock down Bcl-xl efficiently in PC3 cells. Significantly, a comparison of ABT-263, a specific inhibitor of Bcl2 and Bcl-xl, with ABT-199, a Bcl2 selective inhibitor, disclosed that only ABT-263, not ABT-199, could induce apoptosis in LNCaP and PC3 cells. The results indicate that Bcl-xl has a protective role against paclitaxel-induced apoptosis in LNCaP and PC3 cells, and its overexpression causes the paclitaxel resistance seen in PC3 cells. Interestingly, combined paclitaxel with ABT-263 to treat LNCaP and PC3 cells demonstrated synergistic apoptosis activation, indicating that ABT-263 could enhance paclitaxel-induced apoptosis in LNCaP cells and overcome Bcl-xl overexpression to trigger paclitaxel-induced apoptosis in PC3 cells. We also observed that the activation of apoptosis in LNCaP cells was more efficient than in PC3 cells in response to paclitaxel plus ABT-263 or to ABT-263 alone, suggesting that the apoptosis pathway in PC3 cells might have further differences from that in LNCaP cells even after Bcl-xl overexpression is accounted for.

Apoptosis Induction by Ocimum sanctum Extract in LNCaP Prostate Cancer Cells.

Tulsi (Ocimum sanctum Linn), commonly known as "holy basil," has been used for the treatment of a wide range of ailments in many parts of the world. This study focuses on apoptosis-inducing ability of tulsi extract on prostate cancer cells. For this purpose LNCaP prostate cancer cells were treated with different concentrations of 70% ethanolic extract of tulsi (EET) and then the cytotoxicity was determined after 24 and 48 h. After treatment with EET externalization of phosphatidyl serine (PS) from the inner membrane to outer leaflet of the plasma membrane was clearly evidenced by the results obtained from both flow cytometry analysis with Annexin V-FITC and pSIVA-IANBD binding fluorescence microscopy assay. Depolarization of the mitochondrial membrane potential was also evidenced by the presence of 5,5',6,6'-tetrachlolo-1,1',3,3'-tetraethyl benzimedazolyl carbocyanine iodide (JC-1) monomeric form in the EET-treated cells that emitted the green fluorescence when compared with the control cells that emitted the red fluorescence due to aggregation of JC-1. Furthermore, the level of poly (ADP-ribose) polymerase (PARP) cleavage and Bcl-2 were determined using western blot analysis. When compared to the control cells the level of cleaved PARP was found to be higher with a concomitant decrease in the Bcl-2 level after 24 h of treatment of cells with EET. In addition, treatment with EET significantly elevated the activities of caspase-9 and caspase-3 in LNCaP cells compared with the control. Also, after 48 h of treatment all doses used in this study showed clear fragments of DNA, which is one of the hallmarks of apoptosis. Taken together, our findings suggest that, EET can effectively induce apoptosis in LNCaP cells via activation of caspase-9 and caspase-3 that can eventually lead to DNA fragmentation and cell death.

Apoptosis-inducing effect of 131I-K237 on human prostate cancer LNCaP cells

Objective To assess the in vitro affinity and apoptosis-inducing effect of 131I-K237 peptide (H-His-Thr-Met-Tyr-Tyr-His-His-Tyr-Gln-His-His-Leu-OH) to LNCaP prostate cancer cell line. Methods The K237 peptide was radiolabeled with 131I by the Iodogen method. The radiolabeling efficiency and radiochemical purity after purification were then characterized by TLC in vitro. LNCaP cells were inoculated in 96-well cell plate and divided into following groups (3 duplicate wells for each group): 15 kBq 131I-K237 was added in the experimental group, different doses of Na131I (5, 10, 15 kBq) were added in 3 negative control groups, 15 kBq 131I-K237 with different doses of unlabeled K237 (1, 2, 4, 8, 16 μg/μl) were added in 3 blocking groups, and PBS was added in blank control group. The cellular binding ratios were calculated after 48 h. LNCaP cells were inoculated in 24-well cell plate and divided into 3 groups: 131I-K237 group, which including 3 different dose subgroups (5, 10, 15 kBq); unlabeled K237 group, which including 3 different dose subgroups (1, 2, 4 μg/μl); blank control group with 100 μl PBS. All the cells were cultured for 48 h, then optical microscopy (OM) and fluorescence microscopy (FM) were used to observe the cell morphology; DNA gel electrophoresis was conducted and flow cytometry (FCM) was used to estimate the apoptotic rate of LNCaP cells. One-way analysis of variance and the least significant difference (LSD)-t test were used to analyze the data. Results The labeling efficiency of 131I-K237 was (73.7±3.2)% and the radiochemical purity was (96.7±0.6)% after purification. The binding ratio of experimental group was (95.8±1.5)%, whereas the ratio of negative groups with 5, 10, 15 kBq Na131I and PBS group was (8.2±0.4)%, (8.3±0.6)%, (8.6±0.5)% and 0, respectively. The binding ratio of 131I-K237 and LNCaP significantly declined with the increased dose of unlabeled K237 (t=4.71, P<0.01). The apoptosis of LNCaP cells cultured with 131I-K237 was observed. Typical DNA ladder was found by DNA gel electrophoresis. The apoptotic rates of 5, 10, 15 kBq 131I-K237 groups were (34.1±2.9)%, (37.3±3.4)% and (41.7±3.6)%, respectively; whereas those of unlabeled K237 groups and blank control group were (10.8±1.0)%, (12.5±2.1)%, (13.1±2.4)% and (2.9±0.3)%, respectively. There were significant differences of apoptotic rate among groups (F=76.31, P<0.05). The difference among 5, 10, 15 kBq 131I-K237 groups was statistically significant (t=3.09, 3.27, 4.52, all P<0.05). Conclusion 131I-K237 can bind to LNCaP cells with highly affinity and has significant apoptosis-inducing efficacy on the prostate cancer cell line. Key words: Prostatic neoplasms; Tumor cells, cultured; Iodine radioisotopes; Apoptosis

TLR3 engagement induces IRF-3-dependent apoptosis in androgen-sensitive prostate cancer cells and inhibits tumour growth in vivo.

Toll-like receptors (TLRs) are a family of highly conserved transmembrane proteins expressed in epithelial and immune cells that recognize pathogen associated molecular patterns. Besides their role in immune response against infections, numerous studies have shown an important role of different TLRs in cancer, indicating these receptors as potential targets for cancer therapy. We previously demonstrated that the activation of TLR3 by the synthetic double-stranded RNA analogue poly I:C induces apoptosis of androgen-sensitive prostate cancer (PCa) LNCaP cells and, much less efficiently, of the more aggressive PC3 cell line. Therefore, in this study we selected LNCaP cells to investigate the mechanism of TLR3-mediated apoptosis and the in vivo efficacy of poly I:C-based therapy. We show that interferon regulatory factor-3 (IRF-3) signalling plays an essential role in TLR3-mediated apoptosis in LNCaP cells through the activation of the intrinsic and extrinsic apoptotic pathways. Interestingly, hardly any apoptosis was induced by poly I:C in normal prostate epithelial cells RWPE-1. We also demonstrate for the first time the direct anticancer effect of poly I:C as a single therapeutic agent in a well-established human androgen-sensitive PCa xenograft model, by showing that tumour growth is highly impaired in poly I:C-treated immunodeficient mice. Immunohistochemical analysis of PCa xenografts highlights the antitumour role of poly I:C in vivo both on cancer cells and, indirectly, on endothelial cells. Notably, we show the presence of TLR3 and IRF-3 in both human normal and PCa clinical samples, potentially envisaging poly I:C-based therapy for PCa.

The tyrphostin NT157 suppresses insulin receptor substrates and augments therapeutic response of prostate cancer.

Insulin-like growth factor (IGF) signaling is associated with castrate-resistant prostate cancer (CRPC) progression. Insulin receptor substrates 1 and 2 (IRS1/2) mediate mitogenic and antiapoptotic signaling from IGF1 receptor (IGF1R), insulin receptor, and other oncoproteins. This study demonstrates that IRS1/2 expression is increased in prostate cancer, and persists in CRPC. Furthermore, this study assesses the anticancer activity of NT157, a small molecule tyrphostin targeting IRS proteins, using androgen-responsive (LNCaP) and -independent (PC3) prostate cancer cells in vitro and in vivo. NT157 treatment resulted in dose-dependent inhibition of IGF1R activation, suppression of IRS protein expression, inhibition of IGF1-induced AKT activation, but increased ERK activation in NT157-treated cells in vitro. These effects were correlated with decreased proliferation and increasing apoptosis of LNCaP cells and increasing G2-M arrest in PC3 cells. NT157 also suppressed androgen-responsive growth, delayed CRPC progression of LNCaP xenografts, and suppressed PC3 tumor growth alone and in combination with docetaxel. This study reports the first preclinical proof-of-principle data that this novel small molecule tyrosine kinase inhibitor suppresses IRS1/2 expression, delays CRPC progression, and suppresses growth of CRPC tumors in vitro and in vivo. Demonstration that IRS expression can be increased in response to a variety of stressors that may lead to resistance or reduced effect of the therapies indicate that NT157-mediated IRS1/2 downregulation is a novel therapeutic approach for management of advanced prostate cancer.

Fas Activated Serine-Threonine Kinase Domains 2 (FASTKD2) mediates apoptosis of breast and prostate cancer cells through its novel FAST2 domain.

BackgroundExpression of NRIF3 (Nuclear Receptor Interacting Factor-3) rapidly and selectively leads to apoptosis of breast cancer cells. This occurs through binding of NRIF3 or its 30 amino acid Death Domain-1 (DD1) region to the transcriptional repressor, DIF-1 (DD1 Interacting Factor-1). DIF-1 acts in a wide variety of breast cancer cells but not other cell types to repress the pro-apoptotic gene, FASTKD2. Expression of NRIF3 or DD1 inactivates the DIF-1 repressor leading to rapid derepression of FASTKD2, which initiates apoptosis within 5–8 h of expression. Although FASTKD2 is an inner mitochondrial membrane protein, it does not require mitochondrial localization to initiate apoptosis.MethodsAndrogen dependent LNCaP cells as well as two androgen independent LNCaP cell lines (LNCaP-AI and LNCaP-abl) were studied and LNCaP-AI cells were engineered to conditionally express DD1 or the inactive DD1-S28A with 4-hydroxytamoxifen. Apoptosis was assessed by TUNEL assay. FASTKD2 is related to 4 other proteins encoded in the human genome (FASTKD1, 3, 4, 5). All contain a poorly conserved putative bipartite kinase domain designated as FAST1_FAST2. We examined whether expression of any of the other FASTKD isoforms leads to apoptosis and sought to identify the region of FASTKD2 necessary to initiate the apoptotic pathway.ResultsOf the FASTKD1-5 isoforms only expression of FASTKD2 leads to apoptosis. Although, the NRIF3/DD1/DIF-1 pathway does not mediate apoptosis of a wide variety of non-breast cancer cell lines, because of certain similarities and gene signatures between breast and prostate cancer we explored whether the NRIF3/DD1/DIF-1/FASTKD2 pathway mediates apoptosis of prostate cancer cells. We found that the pathway leads to apoptosis in LNCaP cells, including the two androgen-independent LNCaP cell lines that are generally resistant to apoptosis. Lastly, we identified that FASTKD2-mediated apoptosis is initiated by the 81 amino acid FAST2 region.ConclusionsThe NRIF3/DIF-1/FASTKD2 pathway acts as a “death switch” in breast and prostate cancer cells. Deciphering how this pathway is regulated and how FASTKD2 initiates the apoptotic response will allow for the development of therapeutic agents for the treatment of androgen-independent prostate cancer or Tamoxifen-unresponsive Estrogen Receptor negative tumors as well as metastatic breast or prostate cancer.

Abstract 4110: Gartanin from the mangosteen fruit modulates androgen receptor and ER stress proteins in prostate cancer cells leading to apoptosis

Abstract Background: The Purple mangosteen (Garcinia mangostana) has a long history of usage as a medicinal plant in Southeast Asia. Many studies have shown that the chemical constituents of Garcinia mangostana, mainly xanthone derivatives, have a variety of health-promoting properties including antioxidant, anti-inflammatory, antitumoral, antiallergic, antibacterial and antiviral activities. In this study, we evaluated the anticancer effects of gartanin, one of the major xanthones from the mangosteen fruit, in human prostate cancer cells. Next, we investigated the possible mechanisms involved in its anticancer effects. Methods: Two human prostate cancer cell lines, 22Rv1 and LNCaP, were treated with gartanin. Cell apoptosis, viability, proliferation, androgen receptor, prostate specific antigen (PSA), endoplasmic reticulum (ER) stress were evaluated by TdT-mediated dUTP Nick-End Labeling (TUNEL), 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), BrdU, Western blot, RT-PCR, androgen receptor competitor assay, siRNA transfection, ELISA and fluorescent microscopy. Results: Gartanin decreased viability and inhibited proliferation of prostate cancer cells in a dose-dependent manner. Gartanin induced apoptosis as evidenced by TUNEL staining, increased caspase-3 and Bax/Bcl-2 ratio. As a valuable target of prostate cancer, androgen receptor (AR) expression was significantly inhibited by gartanin. Further, gartanin was shown to be an effective AR antagonist, similar to flutamide. Gartanin decreased PSA, a prostate cancer risk factor regulated by the AR signaling pathway. Gartanin increased ER stress proteins and chaperones, such as phosphorylated PERK, CHOP, IRE1 and Bip. Gartanin also induced spliced XBP-1 mRNA, which is an ER stress marker. CHOP knockdown partly inhibited gartanin-induced apoptosis in LNCaP cells, as evidenced by cleaved caspase-3 decrease. Interestingly, CHOP knockdown showed evidence of restoring AR expression in gartanin treated cells. Conclusions: Our study demonstrated that gartanin inhibited proliferation and induced apoptosis on prostate cancer cells in vitro. It achieves its anticancer effects partly through inhibiting AR and promoting ER stress. The ability of gartanin to inhibit prostate cancer cells suggests further research is needed to evaluate gartanin as a novel agent for the management of prostate cancer. Citation Format: Gongbo Li, Sakina Petiwala, Jeremy Johnson. Gartanin from the mangosteen fruit modulates androgen receptor and ER stress proteins in prostate cancer cells leading to apoptosis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4110. doi:10.1158/1538-7445.AM2014-4110

Apogossypolone inhibits the proliferation of LNCaP cells in vitro and in vivo.

The aim of the present study was to investigate the anti-tumor effect of apogossypolone (ApoG2) on human LNCaP cells in vitro and in vivo. Cell viability was evaluated using an MTT assay. Cell autophagy and apoptosis were detected by flow cytometry and using a terminal deoxynucleotidyl transferase dUTP nick end labeling assay, respectively. Morphological autophagy alterations were observed by transmission electron microscopy. The formation of acidic vesicular organelles was assessed by acridine orange staining and fluorescence microscopy. Quantitative polymerase chain reaction (qPCR) was conducted to detect the expression levels of apoptosis-associated protein B-cell lymphoma 2 (Bcl-2) and Bak. The models of transplantation tumors in nude mice were established via subcutaneous injection of LNCaP cells. Growth of LNCaP cells was inhibited by ApoG2 treatment. Flow cytometry demonstrated that ApoG2 induced apoptosis in LNCaP cells. The Bcl-2 expression was decreased while Bak expression was increased. In addition, activation of cysteine aspartate protease (caspase)-3 and -8 was observed and 3-methyladenine (3-MA) enhanced apoptosis of LNCaP cells. Furthermore, nude mice treated with ApoG2 demonstrated a significant decrease in tumor volume and a significant increase in cell viability. Immunohistochemical analysis of tumor tissues demonstrated that ApoG2 enhanced caspase-3, -8, LC-3B and beclin-1 expression and reduced the expression of Bcl-2. ApoG2 was able to effectively suppress the growth of LNCaP cells through the induction of autophagy and apoptosis.

KLF9, a transcription factor induced in flutamide-caused cell apoptosis, inhibits AKT activation and suppresses tumor growth of prostate cancer cells.

Kruppel-like factors (KLFs) are involved in various biological processes; emerging studies have indicated that KLF9 plays a critical role in regulating tumorigenesis. The role of KLF9 in prostate cancer (PCa), however, has not yet been investigated. The expression of KLF members, AKT- and apoptosis-related proteins were analyzed by Western blot or qRT-PCR. Tet-On inducible KLF9 expression was established for the evaluation of the effects of KLF9 on cell proliferation, apoptosis, and xenograft tumor growth in nude mice. Cell cycle and apoptosis were determined by flow cytometry. KLF9 was induced in a time-dependent manner in flutamide-caused apoptosis, and knockdown of KLF9 significantly decreased flutamide-induced growth inhibition and apoptosis in LNCaP cells. The levels of KLF9 were relatively lower in PCa cell lines, particularly in androgen-independent cell lines compared with those in nontumorous prostate epithelial cell lines. Overexpression of KLF9 dramatically suppressed cell proliferation and caused cell cycle arrest in the G2/M phase and cell apoptosis in the androgen-independent cell lines, PC3 and DU145. Intriguingly, KLF9 expression severely suppressed the activation of AKT and its downstream targets. AKT reactivation partially rescued the KLF9-mediated inhibitory effects on the proliferation of PCa cells. More importantly, we found that KLF9 overexpression efficiently inhibited the xenograft tumor growth of PCa cells. These data collectively showing that KLF9 substantially inhibits AKT activation and abrogates tumor growth of PCa cells, suggest the potential of either genetic or pharmacological activation of KLF9 in the therapeutic treatment of castration-resistant PCa.

Adipose-derived stromal cells inhibit prostate cancer cell proliferation inducing apoptosis

Mesenchymal stem cells (MSCs) have generated a great deal of interest in the field of regenerative medicine. Adipose-derived stromal cells (AdSCs) are known to exhibit extensive proliferation potential and can undergo multilineage differentiation, sharing similar characteristics to bone marrow-derived MSCs. However, as the effect of AdSCs on tumor growth has not been studied sufficiently, we assessed the degree to which AdSCs affect the proliferation of prostate cancer (PCa) cell. Human AdSCs exerted an inhibitory effect on the proliferation of androgen-responsive (LNCaP) and androgen-nonresponsive (PC3) human PCa cells, while normal human dermal fibroblasts (NHDFs) did not, and in fact promoted PCa cell proliferation to a degree. Moreover, AdSCs induced apoptosis of LNCaP cells and PC3 cells, activating the caspase3/7 signaling pathway. cDNA microarray analysis suggested that AdSC-induced apoptosis in both LNCaP and PC3 cells was related to the TGF-β signaling pathway. Consistent with our in vitro observations, local transplantation of AdSCs delayed the growth of tumors derived from both LNCaP- and PC3-xenografts in immunodeficient mice. This is the first preclinical study to have directly demonstrated that AdSC-induced PCa cell apoptosis may occur via the TGF-β signaling pathway, irrespective of androgen-responsiveness. Since autologous AdSCs can be easily isolated from adipose tissue without any ethical concerns, we suggest that therapy with these cells could be a novel approach for patients with PCa.

Inhibition of IL-6 expression in LNCaP prostate cancer cells by a combination of atorvastatin and celecoxib

In the present study, we investigated the effect of a combination of atorvastatin and celecoxib on the formation of interleukin (IL)-6, a cytokine that is increased during the progression of LNCaP tumors from androgen dependence to androgen independence. Culturing LNCaP cells in androgen-depleted (AD) medium increased the levels of IL-6 and survivin, and treatment of the cells in AD medium with a combination of atorvastatin and celecoxib strongly inhibited the increase in IL-6 and survivin which is one of the downstream targets of the IL-6 signaling pathway. Addition of recombinant IL-6 partially abrogated the combined effect of atorvastatin and celecoxib on apoptosis in LNCaP cells cultured in AD medium. In SCID mice, we found that the levels of IL-6 and survivin expression were increased when LNCaP tumors became androgen-independent. Treatment of the mice with atorvastatin or celecoxib alone caused decrease in the levels of IL-6 and survivin as LNCaP tumors became androgen-independent, but treatment of the mice with a combination of celecoxib and atorvastatin resulted in a much stronger inhibition in the increase in IL-6 and survivin expression. Our results indicate that decreases in IL-6 and survivin levels by atorvastatin and celecoxib administration are associated with increased apoptosis in LNCaP cells treated with this drug combination. Our in vivo studies indicate that the inhibitory effect of a combination of atorvastatin and celecoxib on the progression of androgen-dependent LNCaP xenograft tumors to androgen independence is associated with inhibition of the increase in IL-6 and survivin that occurs when androgen-dependent LNCaP prostate tumors become androgen-independent.