Apoptosis In Castration-resistant Prostate Cancer Cells Research Articles

A novel HDAC6 inhibitor interferes microtubule dynamics and spindle assembly checkpoint and sensitizes cisplatin-induced apoptosis in castration-resistant prostate cancer.

Metastatic castration-resistant prostate cancer (CRPC), the most refractory prostate cancer, inevitably progresses and becomes unresponsive to hormone therapy, revealing a pressing unmet need for this disease. Novel agents targeting HDAC6 and microtubule dynamics can be a potential anti-CRPC strategy. Cell proliferation was examined in CRPC PC-3 and DU-145 cells using sulforhodamine B assay and anchorage-dependent colony formation assay. Flow cytometric analysis of propidium iodide staining was used to determine cell-cycle progression. Cell-based tubulin polymerization assay and confocal immunofluorescence microscopic examination determine microtubule assembly/disassembly status. Protein expressions were determined using Western blot analysis. A total of 82 novel derivatives targeting HDAC6 were designed and synthesized, and Compound 25202 stood out, showing the highest efficacy in blocking HDAC6 (IC50, 3.5 nM in enzyme assay; IC50, 1.0 μM in antiproliferative assay in CRPC cells), superior to tubastatin A (IC50, 5.4 μM in antiproliferative assay). The selectivity and superiority of 25202 were validated by examining the acetylation of both α-tubulin and histone H3, detecting cell apoptosis and HDACs enzyme activity assessment. Notably, 25202 but not tubastatin A significantly decreased HDAC6 protein expression. 25202 prolonged mitotic arrest through the detection of cyclin B1 upregulation, Cdk1 activation, mitotic phosphoprotein levels, and Bcl-2 phosphorylation. Compound 25202 did not mimic docetaxel in inducing tubulin polymerization but disrupted microtubule organization. Compound 25202 also increased the phosphorylation of CDC20, BUB1, and BUBR1, indicating the activation of the spindle assembly checkpoint (SAC). Moreover, 25202 profoundly sensitized cisplatin-induced cell death through impairment of cisplatin-evoked DNA damage response and DNA repair in both ATR-Chk1 and ATM-Chk2 pathways. The data suggest that 25202 is a novel selective and potent HDAC6 inhibitor. Compound 25202 blocks HDAC6 activity and interferes microtubule dynamics, leading to SAC activation and mitotic arrest prolongation that eventually cause apoptosis of CRPC cells. Furthermore, 25202 sensitizes cisplatin-induced cell apoptosis through impeding DNA damage repair pathways.

Abstract 520: Investigation the function and application of spermine in castration-resistant prostate cancer

Abstract Introduction & Objectives: Spermine (Spm) is a typical metabolite that is highly concentrated in healthy prostate epithelium maintaining cell growth and functions. Our previous studies found that Spm was significantly decreased in PCa tissue than in benign prostate tissue, as was the urinary Spm in PCa. This study aimed to reveal the specific role of Spm in PCa. Materials & Methods: In this study, Spm was resupplied to castration-resistant prostate cancer (CRPC) cells (PC3 and DU145). Following Spm treatment, MTT (methyl thiazolyl tetrazolium) and EdU (5-ethynyl-2’-deoxyuridine) assay were used to determine the cell proliferation of CRPC cell lines. Cellular apoptosis, cell cycle distribution and mitochondrial membrane potential were analyzed by flow cytometry. Cellular reactive Oxygen species (ROS) level was measured by fluorescence microscope. mRNA and ATAC sequencing in spermine-treated CRPC cells were performed to reveal the related mechanism for Spm effect. Results: In the in vitro studies, Spm was found to inhibit the cell viability of CRPC cells. Transwell assays demonstrated that Spm impaired migration and invasion ability. And Spm blocked tumor progression by inducing G2/M arrest and cellular apoptosis in CRPC cells dose-dependently. mRNA seq revealed that a series of genes were altered after Spm treatment and indicated the potential functional pathway of Spm might be mitophagy. We integrated mRNA seq data with ATAC seq profiles and accessed those genes regulated by polyamine metabolism and Spm-induced mitophagy. Results showed the sequencing tracks for the HMOX1 locus contain higher ATAC-seq peaks at the promoter under Spm treatment. Spm could affect oxidative phosphorylation which will lead to mitophagy and mitochondrial metabolism by modulating the transcriptional accessibility of genes. After Spm treatment, cellular ROS was upregulated while the mitochondrial membrane potential collapsed. Subsequently, western blot results showed that PINK1-mediated mitophagy related-proteins were significantly regulated. Conclusion: Our results indicated that Spm treatment led to mitochondrial dysfunction and subsequently degraded through mitophagy in CRPC cells. Our findings could provide a theoretical basis and have preliminary clinical implications in developing Spm as a promising agent against CRPC by inducing cellular mitophagy in CRPC cells. Citation Format: Jingkai Sun, Peter Ka-Fung Chiu, Tingting Xie, Jeremy Yuen-Chun Teoh, Chi-Fai Ng. Investigation the function and application of spermine in castration-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 520.

Polygodial, a Sesquiterpene Dialdehyde, Activates Apoptotic Signaling in Castration-Resistant Prostate Cancer Cell Lines by Inducing Oxidative Stress.

Prostate cancer (PCa) is the second leading cause of cancer death among men in the United States. Surgery, radiation therapy, chemotherapy, and androgen deprivation therapy are currently the standard treatment options for PCa. These have poor outcomes and result in the development of castration-resistant prostate cancer (CRPC), which is the foremost underlying cause of mortality associated with PCa. Taxanes, diterpene compounds approved to treat hormonal refractory PCa, show poor outcomes in CRPC. Polygodial (PG) is a natural sesquiterpene isolated from water pepper (Persicaria hydropiper), Dorrigo pepper (Tasmannia stipitata), and mountain pepper (Tasmannia lanceolata). Previous reports show that PG has an anticancer effect. Our results show that PG robustly inhibits the cell viability, colony formation, and migration of taxane-resistant CRPC cell lines and induces cell cycle arrest at the G0 phase. A toxicity investigation shows that PG is not toxic to primary human hepatocytes, 3T3-J2 fibroblast co-cultures, and non-cancerous BPH-1 cells, implicating that PG is innocuous to healthy cells. In addition, PG induces oxidative stress and activates apoptosis in drug-resistant PCa cell lines. Our mechanistic evaluation by a proteome profiler-human apoptotic array in PC3-TXR cells shows that PG induces upregulation of cytochrome c and caspase-3 and downregulation of antiapoptotic markers. Western blot analysis reveals that PG activates apoptotic and DNA damage markers in PCa cells. Our results suggest that PG exhibits its anticancer effect by promoting reactive oxygen species generation and induction of apoptosis in CRPC cells.

A Synthetic Small Molecule Carbazole SH-I-125 Degrades Androgen Receptor and Overcomes Castration-Resistance and Enzalutamide-Resistance in Prostate Cancer Cells

Resistance to clinical anti-androgens is an ongoing problem in the treatment of castration-resistant prostate cancer (CRPC). Although second generation anti-androgens demonstrate initial clinical benefit, patients often develop resistance to these therapies, evidenced by rising serum PSA levels and disease progression. Several mechanisms including the expression of androgen receptor (AR) splice variants contribute to the reactivation of AR signaling in drug-resistant prostate cancer. Novel therapies that target AR signaling and suppress growth in castration-resistant and anti-androgen-resistant prostate cancer are essential for the effective management of advanced disease. We developed a synthetic small molecule analog of mahanine, SH-I-125, a compound with the ability to disrupt androgen receptor signaling and induce apoptosis in castration-resistant and drug-resistant prostate cancer cellular models. SH-I-125 disrupted AR signaling and induced apoptosis in CRPC cells and anti-androgen-resistant prostate cancer cells in a manner more effective than clinical anti-androgens, enzalutamide and ARN509. Furthermore, SH-I-125 decreased full-length AR and its splice variant AR-V7 levels in 22Rv1 prostate cancer cells by a proteasome-dependent mechanism. These findings indicate the therapeutic potential of SH-I-125 in prostate cancer patients that have progressed on currently approved therapies for CRPC.

LncRNA HORAS5 promotes taxane resistance in castration-resistant prostate cancer via a BCL2A1-dependent mechanism.

Background: Castration-resistant prostate cancer (CRPC) is an incurable malignancy. Long noncoding RNAs (lncRNAs) play key roles in drug resistance. Materials & methods: LncRNA HORAS5 role in cabazitaxel resistance (i.e., cell-count, IC50 and caspase activity) was studied via lentiviral-mediated overexpression and siRNA-based knockdown. Genes expression was analyzed with RNA-sequencing, reverse transcriptionquantitative PCR (RT-qPCR) and westernblot. HORAS5 expression was queried in clinical database. Results: Cabazitaxel increased HORAS5 expression that upregulated BCL2A1, thereby protecting CRPC cells from cabazitaxel-induced apoptosis. BCL2A1 knockdown decreased cell-count and increased apoptosis in CRPC cells. HORAS5-targeting antisense oligonucleotide decreased cabazitaxel IC50. In CRPC clinical samples, HORAS5 expression increased upon taxane treatment. Conclusion:HORAS5 stimulates the expression of BCL2A1 thereby decreasing apoptosis and enhancing cabazitaxel resistance in CRPC cells.

Novel small-molecule LG1836 inhibits the in vivo growth of castration-resistant prostate cancer.

Androgen deprivation therapy (ADT) is the mainstay of treatment for castration-resistant prostate cancer (CRPC). Unfortunately, although ADT initially prolongs survival, most patients relapse and develop resistance. Clinical failure of these treatments in CRPC highlights the urgent need to develop novel strategies to more effectively block androgen receptor (AR) signaling and target other oncogenic factors responsible for ADT resistance. We developed a small-molecule compound LG1836 and investigated the in vitro and in vivo activity of LG1836 against CRPC in cellular and animal models. LG1836 exhibits potent in vitro cytotoxicity in CRPC cells. Mechanistic studies demonstrated that LG1836 inhibits the expression of AR and AR variant 7, partially mediated via proteasome-dependent protein degradation. LG1836 also suppresses survivin expression and effectively induces apoptosis in CRPC cells. Significantly, as a single agent, LG1836 is therapeutically efficacious in suppressing the in vivo growth of CRPC in the subcutaneous and intraosseous models and extends the survival of tumor-bearing mice. These preclinical studies indicate that LG1836 is a promising lead compound for the treatment of CRPC.

GLUT1 is an AR target contributing to tumor growth and glycolysis in castration-resistant and enzalutamide-resistant prostate cancers.

Castration-resistant prostate cancer (CRPC) displays a higher 18F-FDG PET SUVmax than hormone-sensitive prostate cancer, which suggests a greater need for glucose metabolism in CRPC. Targeting glucose metabolism in cancer cells remains attractive for cancer treatment. Glucose transporters (GLUTs) meditate the first and rate-limiting step of glucose metabolism. Here, we investigated the key mediator of glucose transporters and evaluated its therapeutic value in a preclinical model of CRPC. 18F-FDG PET showed a higher SUVmax in CRPC than in hormone-sensitive prostate cancer, and GLUT1 expression positively correlated with SUVmax and was associated with a worse CRPC outcome. GLUT1 inhibition significantly suppressed cell growth, glycolysis and tumor volume in a xenograft model both in CRPC and enzalutamide-resistant prostate cancer. Chromatin immunoprecipitation and dual luciferase reporter assay showed that androgen receptor (AR) directly bound to the GLUT1 gene promoter to promote GLUT1 transcription. Combining GLUT1 inhibition and enzalutamide remarkably suppressed proliferation and glycolysis and induced apoptosis in CRPC cells. Our results suggest that GLUT1 is an AR target and displays synergistic effects with enzalutamide. GLUT1 may act as a promising therapeutic target in CRPC and enzalutamide-resistant prostate cancer.

Rooibos suppresses proliferation of castration-resistant prostate cancer cells via inhibition of Akt signaling

BackgroundAndrogen ablation therapy is the primary treatment for metastatic prostate cancer (PCa). However, the majority of PCa patients receiving the androgen deprivation therapy develop recurrent castration-resistant prostate cancer (CRPC) within two years. Chemotherapies show little effect on prolonging survival of CRPC patients and new treatments are needed. Previous studies reported that the extracts from rooibos (Aspalathus linearis) exhibit chemopreventive properties in some cancer models, including skin, liver and oesophagus cancers in animals. We therefore investigate if extracts from rooibos can suppress the proliferation of CRPC cells. PurposeWe investigated whether an aspalathin-rich green rooibos extract (GRT™; 12.78 g aspalathin/100 g extract) demonstrates anti-cancer activity against CRPC cells. MethodsHigh performance liquid chromatography (HPLC) was used to profile the major flavonoids in GRT. Hoechst-dye proliferation assay, 3,4,5-dimethylthiazol-2-yl)-2-5-diphenyltetrazolium bromide (MTT) viability assay and flow cytometry assay were used to explore the effects of GRT on the proliferation and cell cycle progression of CRPC cells. Comet assay was used to survey whether GRT induces apoptosis in CRPC cells. LNCaP 104-R1 xenograft nude mice model was used to determine the inhibitory effect of GRT on CRPC tumors in vivo. Micro-Western Array (MWA) and Western blot analysis were carried out to unravel the underlying molecular mechanism. ResultsGRT contained aspalathin as the most abundant flavonoid. GRT suppressed the proliferation and survival of LNCaP 104-R1, LNCaP FGC and PC-3 PCa cells. Flow cytometry analysis showed that GRT decreased the population of PCa cells in S phase but increased the cell population in G2/M phase. Comet assay confirmed that GRT induced apoptosis in LNCaP 104-R1 cells. Gavage of 400 mg/kg GRT suppressed LNCaP 104-R1 xenografts in castrated nude mice. MWA and Western blot analysis indicated that GRT treatment suppressed Akt1, phospho-Akt Ser473, Cdc2, Bcl-2, TRAF4 and Aven, but increased activated Caspase 3, cytochrome c, and p27Kip1. Overexpression of Akt rescued the suppressive effects of GRT on CRPC cells. Co-treatment of GRT with Bcl-2 inhibitor ABT-737, PI3K inhibitor LY294002 and Akt inhibitor GSK 690693 exhibited additive inhibitory effect on proliferation of CRPC cells. ConclusionsGRT suppresses the proliferation of CRPC cells via inhibition of Akt signaling.

Phosphodiesterase Type 5 (PDE5) Inhibitors Sensitize Topoisomerase II Inhibitors in Killing Prostate Cancer Through PDE5-Independent Impairment of HR and NHEJ DNA Repair Systems.

Human castration-resistant prostate cancer (CRPC) is a significant target of clinical research. The use of DNA-damaging agents has a long history in cancer chemotherapy but is limited by their toxicities. The combination with a safer drug can be a strategy in reducing dosage and toxicity while increasing anticancer activity in CRPC treatment. Phosphodiesterase type 5 (PDE5) inhibitors are used to treat erectile dysfunction through the selective inhibition of PDE5 that is responsible for cGMP degradation in the corpus cavernosum. Several studies have reported that PDE5 inhibitors display protective effect against doxorubicin-induced cardiotoxicity. The combinatory treatment of CRPC with doxorubicin and PDE5 inhibitors has been studied accordingly. The data demonstrated that sildenafil or vardenafil (two structure-related PDE5 inhibitors) but not tadalafil (structure-unrelated to sildenafil) sensitized doxorubicin-induced apoptosis in CRPC cells with deteriorating the down-regulation of anti-apoptotic Bcl-2 family members, including Bcl-xL and Mcl-1, and amplifying caspase activation. Homologous recombination (HR) and non-homologous end joining (NHEJ) DNA repair systems were inhibited in the apoptotic sensitization through detection of nuclear foci formation of Rad51 and DNA end-binding of Ku80. PDE5 knockdown to mimic the exposure to PDE5 inhibitors did not reproduce apoptotic sensitization, suggesting a PDE5-independent mechanism. Not only doxorubicin, sildenafil combined with other inhibitors of topoisomerase II but not topoisomerase I also triggered apoptotic sensitization. In conclusion, the data suggest that sildenafil and vardenafil induce PDE5-independent apoptotic sensitization to doxorubicin (or other topoisomerase II inhibitors) through impairment of both HR and NHEJ repair systems that are evident by a decrease of nuclear Rad51 levels and their foci formation in the nucleus, and an inhibition of Ku80 DNA end-binding capability. The combinatory treatment may enable an important strategy for anti-CRPC development.

Abstract 3205: A nanomolar potency small-molecule compound against castration-resistant and bone metastatic prostate cancer

Abstract A standard treatment for prostate cancer (PCa) is androgen deprivation therapy (ADT) that suppresses androgen receptor (AR) signaling axis. Although initially responsive, most patients receiving ADT eventually develop metastatic castration-resistant prostate cancer (CRPC), with more than 90% of them exhibiting bone metastases. A mechanism by which CRPC cells evade ADT is the expression of constitutively active AR variants (AR-Vs), such as the well-characterized AR-V7. Recently we developed GH501, a flurbiprofen-modified small-molecule compound, and investigated its anti-cancer activity and mechanism of action in pre-clinical models of CRPC. At nanomolar range, GH501 effectively induces cell cycle arrest and apoptosis in CRPC cells regardless of their resistance status to enzalutamide treatment. RNA-seq analysis of GH501 combined with Western blotting analysis identified key targets implicated in CRPC progression, including the full-length AR, AR-V7 variant, and other important genes implicated in CRPC progression. Importantly, low doses of GH501 effectively inhibit the skeletal growth of CRPC in a xenograft model without obvious in vivo toxicities. These preclinical results indicate that GH501 is a promising small-molecule compound that can be further developed for the treatment of lethal prostate cancer. Citation Format: Kenza Mamouni, Lajos Gera, Xin Li, Daqing Wu. A nanomolar potency small-molecule compound against castration-resistant and bone metastatic prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3205. doi:10.1158/1538-7445.AM2017-3205

Inhibition of AKT promotes FOXO3a-dependent apoptosis in prostate cancer.

Growth factor-induced activation of protein kinase-B (PKB), also known as AKT, induces pro-survival signaling and inhibits activation of pro-apoptotic signaling molecules including the Forkhead box O-3a (FOXO3a) transcription factor and caspase in transformed prostate cells in vitro. Earlier we reported that Withaferin-A (WA), a small herbal molecule, induces pro-apoptotic response-4 (Par-4) mediated apoptosis in castration-resistant prostate cancer (CRPC) cells. In the present study, we demonstrate that inhibition of AKT facilitates nuclear shuttling of FOXO3a where it regulates Par-4 transcription in CRPC cells. FOXO3a is upstream of Par-4 signaling, which is required for induction of apoptosis in CRPC cells. Promoter bashing studies and Ch-IP analysis confirm a direct interaction of FOXO3a and Par-4; a sequential deletion of FOXO3a-binding sites in the Par-4 promoter fails to induce Par-4 activation. To confirm these observations, we either overexpressed AKT or silenced FOXO3a activation in CRPC cells. Both methods inhibit Par-4 function and apoptosis is significantly compromised. In xenograft tumors derived from AKT-overexpressed CRPC cells, FOXO3a and Par-4 expression is downregulated, leading to aggressive tumor growth. Oral administration of WA to mice with xenograft tumors restores FOXO3a-mediated Par-4 functions and results in inhibited tumor growth. Finally, an inverse correlation of nuclear localization of AKT expression corresponds to cytoplasmic Par-4 localization in human prostate tissue array. Our studies suggest that Par-4 is one of the key transcriptional targets of FOXO3a, and Par-4 activation is required for induction of apoptosis in CRPC cells. Activation of FOXO3a appears to be an attractive target for the treatment of CRPC and molecules such as WA can be explored further for the treatment of CRPC.

MicroRNA-19a regulates proliferation and apoptosis of castration-resistant prostate cancer cells by targeting BTG1

MicroRNAs (miRNAs) play a significant role in tumor development. Recent studies indicate that miRNAs are implicated in prostate cancer (PCa). In this study, we found that miR-19a expression was significantly increased in castration-resistant prostate cancer (CRPC) tissues compared with androgen-dependent prostate cancer (ADPC) tissues. We found that inhibiting the overexpression of miR-19a in CRPC cells suppressed proliferation and increased apoptosis. Additionally, we found that miR-19a repressed BTG1 expression by binding to its 3′-untranslated region. The overexpression of BTG1 in CRPC cells significantly suppressed proliferation and increased apoptosis. We conclude that miR-19a regulates proliferation and apoptosis of CRPC cells by directly targeting the tumor suppressor gene BTG1.

MLN2238 synergizes BH3 mimetic ABT-263 in castration-resistant prostate cancer cells by induction of NOXA

Patients undergoing androgen blockade therapy develop castration-resistant prostate cancer (CRPC), which is associated with Bcl-2 upregulation and results in disease progression and death. In recent years, promising therapeutic agents, such as the BH3-only mimetic ABT-263 and proteasome inhibitors, have been developed and widely evaluated against a broad spectrum of cancer types, including prostate cancer, alone or in combination with other chemotherapeutic agents. In this study, the antitumor efficacy of ABT-263 and MLN2238 were evaluated as single agents and in combination in four CRPC cell lines: PC3, C4-2B, C4-2, and DU145. The viability of the treated cells and markers of apoptosis were assayed. Protein-protein interactions were analyzed by co-immunoprecipitation in drug-treated cells. Lentivirus-mediated short hairpin RNA was used to knockdown Bax, Mcl-1, and NOXA expressions. We found that ABT-263 and MLN2238 alone exhibited a mild cytotoxicity, and in combination, they elicited a synergistic cytotoxic effect in CRPC cells. The cell apoptosis induced by the combination drug treatment was evidenced by enhanced caspase-3 and Poly (ADP-ribose) polymerase (PARP) cleavage, and annexin-V-positive staining was significantly depleted by Bax knockdown. MLN2238 treatment upregulated NOXA and Mcl-1 expression, leading NOXA/Mcl-1 complexes to disassociate Bak from its complexes with Mcl-1 and enhancing ABT263-triggered Bax activation. NOXA knockdown by short hairpin RNA significantly attenuated the cytotoxicity of ABT-263 and MLN2238 co-administration. In conclusion, MLN2238 and ABT-263 synergistically triggered apoptosis in CRPC cells by upregulating NOXA and activating Bax, indicating a promising therapeutic strategy for the treatment of CRPC.

Abstract 843: Inhibition of AKT signaling promotes FOXO3a-dependent apoptosis in castration-resistant prostate cancer cells.

Abstract Treatment for aggressive prostate cancers involves hormonal ablation therapy, radical prostatectomy, radiation therapy, chemotherapy or in combination. Despite their initial sensitivity to these treatments, prostate cancer eventually progresses to castration -resistant prostate cancer (CRPC), which is both aggressive and refractory to current therapeutic modalities. Hence, CRPC demands the identification of novel targeted therapies with minimal side effects. We identified Withaferin-A (WA) a major bioactive compound derived from the medicinal plant, Withania somnifera, is extensively used in Asian herbal medicines to treat a variety of ailments, including cancer. Earlier, we reported that WA induced the pro-apoptotic gene, prostate apoptosis response-4 (Par-4) and apoptosis in CRPC cells. These results encouraged us to determine the mechanism of action of WA on CRPC cells. It is known that activated AKT negatively regulates forkhead transcription factor class O family protein (FOXO3a) that regulates genes involved with tumorigenesis, cell cycle arrest or apoptosis. In the present study, we found that FOXO3a is an upstream of Par-4 signaling which transactivates Par-4 function in CRPC cells. Inhibition of AKT activation by WA facilitates nuclear translocation of FOXO3a which in turn activates Par-4 mediated apoptosis in CRPC cells. Our confocal and immuno-precipitation studies confirmed that upon activation. FOXO3a and Par-4 were co-localized in the nucleus. Similar results were found with overexpression of FOXO3a showing transactivation of Par-4 and growth arrest in CRPC cells. Treatment of actinomycin-D or cyclohexmide along with WA, confirmed that FOXO3a regulation on Par-4 function in CRPC cells. On contrary, inhibition of FOXO3a by siRNA resulted in down regulation of Par-4 and apoptosis by WA in CRPC cells suggesting FOXO3a activation is necessary for the induction of Par-4 mediated apoptosis. Promoter bashing studies suggest a direct interaction of FOXO3a with Par-4 promoter; a sequential deletion of FOXO3a DNA binding sites in Par-4 promoter fails to induce Par-4 activation upon WA treatment in CRPC cells. Overall, our studies conclude that Par-4 is a target of FOXO3a, and Par-4 activation is required for induction of apoptosis in CRPC cells. Activation of FOXO3a is an attractive target for the treatment of CRPC and molecules such as WA can be explored further for the treatment of CRPC. Citation Format: Trinath P. Das, Chendil Damodaran. Inhibition of AKT signaling promotes FOXO3a-dependent apoptosis in castration-resistant prostate cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 843. doi:10.1158/1538-7445.AM2013-843