Development Of Human Prostate Cancer Research Articles

Microfluidic-based human prostate-cancer-on-chip.

Lack of adequate models significantly hinders advances in prostate cancer treatment, where resistance to androgen-deprivation therapies and bone metastasis remain as major challenges. Current in vitro models fail to faithfully mimic the complex prostate physiology. In vivo animal models can shed light on the oncogenes involved in prostate cancer development and progression; however, the animal prostate gland is fundamentally different from that of human, and the underlying genetic mechanisms are different. To address this problem, we developed the first in vitro microfluidic human Prostate-Cancer-on-Chip (PCoC) model, where human prostate cancer and stromal fibroblast cells were co-cultivated in two channels separated by a porous membrane under culture medium flow. The established microenvironment enables soluble signaling factors secreted by each culture to locally diffuse through the membrane pores affecting the neighboring culture. We particularly explored the conversion of the stromal fibroblasts into cancer-associated fibroblasts (CAFs) due to the interaction between the 2cell types. Immunofluorescence microscopy revealed that tumor cells induced CAF biomarkers, αSMA and COL1A1, in stromal fibroblasts. The stromal CAF conversion level was observed to increase along the flow direction in response to diffusion agents, consistent with simulations of solute concentration gradients. The tumor cells also downregulated androgen receptor (AR) expression in stromal fibroblasts, while an adequate level of stromal AR expression is maintained in normal prostate homeostasis. We further investigated tumor invasion into the stroma, an early step in the metastatic cascade, in devices featuring a serpentine channel with orthogonal channel segments overlaying a straight channel and separated by an 8µm-pore membrane. Both tumor cells and stromal CAFs were observed to cross over into their neighboring channel, and the stroma's role seemed to be proactive in promoting cell invasion. As control, normal epithelial cells neither induced CAF conversion nor promoted cell invasion. In summary, the developed PCoC model allows spatiotemporal analysis of the tumor-stroma dynamic interactions, due to bi-directional signaling and physical contact, recapitulating tissue-level multicellular responses associated with prostate cancer in vivo. Hence, it can serve as an in vitro model to dissect mechanisms in human prostate cancer development and seek advanced therapeutic strategies.

Abstract 2197: Dysregulated alternative splicing landscape identifies intron retention as a hallmark and spliceosome as a therapeutic vulnerability in aggressive prostate cancer

Abstract Dysregulation of mRNA alternative splicing (AS) has been implicated in development and progression of hematological malignancies. How the global AS dysregulation contributes to the development and progression of solid tumors is under-studied and remains generally unclear. Here we describe the first comprehensive AS landscape in the spectrum of human prostate cancer (PCa) development, progression and therapy resistance. We find that the severity of splicing dysregulation correlates with disease progression and establish intron retention (IR) as a hallmark of PCa stemness and aggressiveness. Systematic interrogation of 274 splicing-regulatory genes (SRGs) uncovers prevalent SRG mutations associated with, mainly, copy number variations leading to mis-expression of ~68% of SRGs during PCa evolution. Consequently, we identify many SRGs as prognostic markers associated with splicing disruption and patient outcome. Interestingly, androgen receptor (AR) controls a splicing program distinct from its transcriptional regulation. The spliceosome modulator, E7107, reverses cancer aggressiveness and inhibits the growth of castration-resistant PCa (CRPC) xenograft models and of the autochthonous Hi-Myc tumors. Altogether, our studies establish aberrant AS landscape caused by dysregulated SRGs as a hallmark of PCa aggressiveness and a novel therapeutic vulnerability for CRPC. Citation Format: Dingxiao Zhang, qiang Hu, Xiaozhuo Liu, Yibing Ji, Hsueh-Ping Chao, Amanda Tracz, Jason Kirk, Silvia Buonamici, Ping Zhu, Jianmin Wang, song liu, Dean Tang. Dysregulated alternative splicing landscape identifies intron retention as a hallmark and spliceosome as a therapeutic vulnerability in aggressive prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2197.

Progression-free survival of prostate cancer patients is prolonged with a higher regucalcin expression in the tumor tissues: Overexpressed regucalcin suppresses the growth and bone activity in human prostate cancer cells

Prostate cancer, which is a bone metastatic cancer, is the second leading cause of cancer-related death in men. There is no effective treatment for metastatic prostate cancer. Regucalcin has been shown to contribute as a suppressor in various types of human cancers. In the present study, furthermore, we investigate an involvement of regucalcin in suppression of prostate cancer. Regucalcin expression was compared in 131 primary tumor tissues and 19 metastatic tumor tissues in prostate cancer patients. Regucalcin expression in the metastatic tumor was found to be reduced as compared with that in primary tumor. The progression-free survival rate was prolonged in patients with a higher regucalcin expression. Translationally, overexpression of regucalcin in bone metastatic human prostate cancer PC-3 and DU-145 cells suppressed colony formation and cell growth in vitro. Mechanistically, overexpressed regucalcin enhanced the levels of p53, Rb, and p21, and decreased the levels of Ras, PI3 kinase, Akt, and mitogen-activated protein kinase, leading to suppression of cell growth. Furthermore, higher regucalcin expression suppressed the levels of nuclear factor-κB p65, β-catenin, and signal transducer and activator of transcription 3, which regulate a transcription activity. Cell growth was promoted by culturing with the calcium agonist Bay K 8644. This effect was blocked by overexpression of regucalcin. Notably, overexpressed regucalcin suppressed bone metastatic activity of PC-3 and DU-145 cells when cocultured with preosteoblastic or preosteoclastic cells. Regucalcin may suppress the development of human prostate cancer, suggesting that gene delivery systems in which its expression is forced may be a novel therapeutic strategy.

Human microbiome and prostate cancer development: current insights into the prevention and treatment.

The huge communities of microorganisms that symbiotically colonize humans are recognized as significant players in health and disease. The human microbiome may influence prostate cancer development. To date, several studies have focused on the effect of prostate infections as well as the composition of the human microbiome in relation to prostate cancer risk. Current studies suggest that the microbiota of men with prostate cancer significantly differs from that of healthy men, demonstrating that certain bacteria could be associated with cancer development as well as altered responses to treatment. In healthy individuals, the microbiome plays a crucial role in the maintenance of homeostasis of body metabolism. Dysbiosis may contribute to the emergence of health problems, including malignancy through affecting systemic immune responses and creating systemic inflammation, and changing serum hormone levels. In this review, we discuss recent data about how the microbes colonizing different parts of the human body including urinary tract, gastrointestinal tract, oral cavity, and skin might affect the risk of developing prostate cancer. Furthermore, we discuss strategies to target the microbiome for risk assessment, prevention, and treatment of prostate cancer.

The human gastrointestinal microbiota and prostate cancer development and treatment.

The human gastrointestinal microbiome contains commensal bacteria and other microbiota that have been gaining increasing attention in the context of cancer development and response to treatment. Microbiota play a role in the maintenance of host barrier surfaces that contribute to both local inflammation and other systemic metabolic functions. In the context of prostate cancer, the gastrointestinal microbiome may play a role through metabolism of estrogen, an increase of which has been linked to the induction of prostatic neoplasia. Specific microbiota such as Bacteroides, Streptococcus, Bacteroides massiliensis, Faecalibacterium prausnitzii, Eubacterium rectalie, and Mycoplasma genitalium have been associated with differing risks of prostate cancer development or extensiveness of prostate cancer disease. In this Review, we discuss gastrointestinal microbiota's effects on prostate cancer development, the ability of the microbiome to regulate chemotherapy for prostate cancer treatment, and the importance of using Next Generation Sequencing to further discern the microbiome's systemic influence on prostate cancer.

Growth Factor-Independent 1 Is a Tumor Suppressor Gene in Colorectal Cancer.

Colorectal cancer is the third most common cancer and the third leading cause of cancer death in the United States. Growth factor-independent 1 (GFI1) is a zinc finger transcriptional repressor responsible for controlling secretory cell differentiation in the small intestine and colon. GFI1 plays a significant role in the development of human malignancies, including leukemia, lung cancer, and prostate cancer. However, the role of GFI1 in colorectal cancer progression is largely unknown. Our results demonstrate that RNA and protein expression of GFI1 are reduced in advanced-stage nonmucinous colorectal cancer. Subcutaneous tumor xenograft models demonstrated that the reexpression of GFI1 in 4 different human colorectal cancer cell lines inhibits tumor growth. To further investigate the role of Gfi1 in de novo colorectal tumorigenesis, we developed transgenic mice harboring a deletion of Gfi1 in the colon driven by CDX2-cre (Gfi1F/F; CDX2-cre) and crossed them with ApcMin/+ mice (ApcMin/+; Gfi1F/F; CDX2-cre). Loss of Gfi1 significantly increased the total number of colorectal adenomas compared with littermate controls with an APC mutation alone. Furthermore, we found that compound (ApcMin/+; Gfi1F/F; CDX2-cre) mice develop larger adenomas, invasive carcinoma, as well as hyperplastic lesions expressing the neuroendocrine marker chromogranin A, a feature that has not been previously described in APC-mutant tumors in mice. Collectively, these results demonstrate that GFI1 acts as a tumor suppressor gene in colorectal cancer, where deficiency of Gfi1 promotes malignancy in the colon. IMPLICATIONS: These findings reveal that GFI1 functions as a tumor suppressor gene in colorectal tumorigenesis.

LincRNA-p21 suppresses development of human prostate cancer through inhibition of PKM2.

Previously, we found that long intergenic non-coding RNA-p21 (lincRNA-p21) inhibited the development of human prostate cancer. However, the underlying molecular mechanisms are poorly understood. Here, we attempted to investigate the downstream targets of lincRNA-p21 in prostate cancer. Expression of lincRNA-p21 and PKM2 was determined by qRT-PCR and Western blot. Lentivirus expressing shPKM2 or shCtrl was used to explore the role of PKM2 on the enhanced cell proliferation and glycolysis of lincRNA-p21-silenced prostate cancer cells. A xenograft mouse model was performed to investigate the effect of PKM2 suppression, glycolytic or mammalian target of rapamycin (mTOR) inhibitor on the tumorigenic capacity of lincRNA-p21-silenced prostate cancer cells. We revealed that lincRNA-p21 silencing in DU145 and LNCaP cells induced up-regulation of PKM2 and activation of glycolysis, which could be reversed by PKM2 knockdown or rapamycin treatment. We also found that the proliferation and tumorigenesis of lincRNA-p21-silenced prostate cancer cells were significantly inhibited after knocking down PKM2. 3-bromopyruvate (3-Brpa) or rapamycin treatment largely decreased the tumour burden. Importantly, PKM2 expression was inversely correlated with the lincRNA-p21 level and the survival of prostate cancer patients. We demonstrated that lincRNA-p21 blunted the prostate cancer cell proliferation and tumorigenic capacity through down-regulation of PKM2. Therefore, targeting PKM2 or glycolysis might be a therapeutic strategy in prostate cancer patients with lowly expressed lincRNA-p21.

English

Prostate cancer is the second most frequently diagnosed cancer and the sixth most commonly fatal cancer in men worldwide. Endothelin-1 (ET-1), produced by the prostate epithelia, likely plays an important role in the progression of prostate cancer. ET-1 has been previously reported in prostate and other organs. However, ET-1 expression in Prostate cancer cell lines has not been described. Therefore, we have used Western Blot to demonstrate ET-1 expression in breast cancer cell lines (LNCap cell line, PC3 cell line and DU145 cell line). The results suggest the expression of ET-1 is significantly high expressed in PC3 cell line. Moreover, knockdown of ET-1 gene with siRNA can effectively repress the cell proliferation and the cell cycle was blocked in G1/G2 phase. Knockdown of ET-1 gene can affect cell invasion, which is confirmed by cell invasion and migration related genes using west blot (-catenin, Ecadherin, RhoC and RhoA). Characterization of the role of ET-1 in the development of tumors could lead to a better understanding of the changes occurring at the molecular level during the development and progression of primary human Prostate cancer.

Long intragenic non-coding RNA lincRNA-p21 suppresses development of human prostate cancer.

Prostate cancer is one of the most frequent malignancies in men, worldwide, although its underlying mechanisms are not fully understood. Long non-coding RNAs participate in development of human cancers. In this invetsigation, we aimed to study the roles of lincRNA-p21 in development of human prostate cancer. Expression of lincRNA-p21 was assessed by real-time PCR in cell lines and in human tissues. Lentivirus carrying sh-lincRNA-p21, lincRNA-p21 or control constructs were used to determine their effects on cell proliferation and apoptosis. A mouse xenograft model was employed to explore the functions of lincRNA-p21 on cancer cell population growth in vivo. Relationships between p53 downstream genes and lincRNA-p21 levels were explored by real-time PCR, western blotting and chromatin immunoprecipitation. LincRNA-p21 was found to be down-regulated in human prostate cancer, and low levels of lincRNA-p21 correlated with high disease stage and prediction of poor survival. We further showed that lincRNA-p21 inhibited prostate cancer cell proliferation and colony formation in vitro and reduced rate of prostate cancer cell population growth in vivo. Study of mechanisms involved revealed that lincRNA-p21 promoted apoptosis and induced expression of p53 downstream genes by regulating p53 binding to their promoters. Finally, we showed that expression of p53 downstream genes was reduced in the malignant prostate tissues, which correlated with lincRNA-p21 level. Our findings indicated that lincRNA-p21 inhibited development of human prostate cancer partly by regulating p53 downstream gene expression and partly by apoptotic activation.

Stromal factors involved in human prostate cancer development, progression and castration resistance.

To detect new predictive markers from the prostate cancer tissue, to study the expression by cultured cancer-associated fibroblasts (CAFs) of stromal factors implicated in prostate carcinogenesis, and to compare their expressions in localized, metastatic, castration-sensitive (CSCP), castration-resistant prostate tumors (CRCP) as well as in fibroblasts from benign prostatic hyperplasia (BPH). The genomic expression of 20 stroma-derived factors, including the androgen receptor (AR), growth factors (FGF2, FGF7, FGF10, HGF, TGFβ, PDGFB), protein implicated in invasion (MMP-2, MMP-9 and MMP-11), inflammation (IL-6, IL-17, STAT-3 and NFκB), stroma/epithelium interaction (CDH11, FAP, CXCL12 and CXCL14) and chaperones (HPA1A and HSF1), was evaluated in cultured fibroblasts both from BHP and prostate carcinomas (PCa). After isolation and culture of fibroblasts by biopsy specimens, RNA was isolated and genomic studies performed. Finally, 5 BPH and 37 PCa specimens were selected: clinically localized (19), metastatic (5), CSCP (7) and CRPC (6). Interleukin-17 receptor (IL-17RB) was highly expressed in CAFs compared with fibroblasts from BPH. However, metalloproteinase-2 and chemokine ligand 14 (CXCL14) were expressed at higher levels by fibroblasts from BPH. The fibroblastic growth factor-7 was highly expressed by CAFs from localized tumors, but metalloproteinase-11 in metastatic tumors. MMP-11, androgen receptor (AR) and heat-shock-70kda-protein-1A (HSPA1A) expressions were significantly higher in CAFs from CRPC. These results demonstrate a CAFs heterogeneity among prostate carcinomas with regard to some molecular profile expressions that may be relevant in tumor development (IL-17RB), progression (MMP-11) and castration resistance (AR, MMP-11 and HSPA1A).

Abstract LB-160: Human telomerase RNA component (hTR/TERC) is consistently overexpressed in prostate cancer, required for cell proliferation and is positively regulated by MYC

Abstract Introduction: Telomerase activity (TA) is increased in most human cancers (80 - 90%) as a mechanism to maintain telomere function, yet the complex regulatory mechanisms driving TA in different cancer types remain obscure. Telomerase consists of at least two essential elements, a catalytic component (TERT) and an RNA subunit (hTR or TERC). Early data showed that TERC was constitutively expressed at similar levels in different tissues and cancer and that TERT mRNA levels best correlated with enzymatic activity across normal tissues and cancer cells. However, accumulating evidence suggests a more important role for the regulation of TERC in telomere maintenance, as well as possible telomerase activity-independent functions. MYC (c-Myc) is overexpressed in most prostate cancers and is known to regulate TERT mRNA levels in a number of cell types and hence to drive TA. However, there are no prior studies of MYC regulation of TERC. We performed a comprehensive study of TERC expression in cancer cell lines and prostatic tissue, across normal, high grade prostatic intraepithelial neoplasia (PIN), primary carcinomas (PCa), and castrate resistant metastatic disease. We further explored MYC regulation of TERC in Pca and examined cell proliferation in TERC-depleted Pca cell lines. Experiments and results: Using a novel chromogenic In Situ Hybridization (CISH) RNA assay in FFPE tissues, validated in cell lines by RT-PCR, we found consistent TERC overexpression in nuclei of PIN (p<0.001, N = 26 patients) and Pca cells (p<0.001, N = 66 patients), that was confirmed by qRT-PCR (n = 25) and RNAseq (n = 12) in tumor/benign frozen tissue pairs. There was no association with Gleason score or pathologic stage, and a weak correlation between TERC and TERT levels by RT-PCR. There was a correlation between TERC CISH and MYC protein expression in prostate tissue (Spearman 0.4540, p<0.0001). Further, we show: i) that forced reductions of MYC resulted in decreased TERC levels in 8 cancer cell lines (prostate, lung, breast, and colorectal); ii) MYC occupies the TERC locus by chromatin immunoprecipitation (ChIP); iii) there is a decrease in human TERC promoter activity with MYC silencing; iv) increased Terc levels in PIN and carcinoma in 2 different mouse models of prostate-restricted overexpression of MYC; and v) knockdown of TERC by siRNA resulted in reduced growth and decreased Ki-67 in TERC depleted human prostate cancer cells. Conclusions: We report consistent overexpression of TERC in PIN and PCa and show the first evidence of MYC regulation of TERC. These studies suggest an important role for MYC-regulated TERC overexpression in human prostate cancer development and progression. Further studies are required to better understand the functional roles of TERC (e.g. TA mediated vs. other activity) in carcinogenesis of the prostate and other organ sites and its regulation by MYC. Citation Format: Javier A. Baena Del Valle, Qizhi Zheng, Michael Rubenstein, Alan K. Meeker, Christopher M. Heaphy, Gretchen Hubbard, Charles J. Bieberich, Srinivasan Yegnasubramanian, David Esopi, Sarah J. Wheelan, Angelo M. De Marzo. Human telomerase RNA component (hTR/TERC) is consistently overexpressed in prostate cancer, required for cell proliferation and is positively regulated by MYC. [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 LB-160.

The Germ Cell Gene TDRD1 as an ERG Target Gene and a Novel Prostate Cancer Biomarker

TMPRSS2-ERG fusion occurs in about half of prostate cancers and results in over-expression of the oncogenic ERG protein in the prostate. The mechanism by which ERG contributes to prostate cancer initiation and progression remains largely unknown. Because ERG is a transcriptional activator, we reasoned that the target genes regulated by ERG could contribute to prostate cancer development. In a search for ERG target genes, we took advantage of published datasets from the MSKCC Prostate Oncogene Project, in which a comprehensive analysis was applied to define transcriptomes in 150 prostate tumors. We retrieved the mRNA expression dataset, split them based on ERG expression, and identified genes whose expression levels are associated with ERG mRNA levels. mRNA expression levels of 21 genes were found to be significantly increased, while for one gene it was decreased in ERG-positive prostate tumors. Among them, the expression of TDRD1 was the most significantly increased in ERG-positive tumors. Among 131 primary prostate tumors which were primarily from European American patients, TDRD1 is over-expressed in 68% of samples, while ERG is overexpressed in 48% of samples, suggesting an additional ERG-independent mechanism of TDRD1 overexpression. In African American prostate tumors, TDRD1 mRNA is expressed in 44%, while ERG is expressed in 24% of samples. In normal tissues, TDRD1 mRNA is exclusively expressed in germ cells and its protein is also known as cancer/testis antigen 41.1 (CT41.1). We generated a mouse monoclonal antibody that recognizes human TDRD1 protein with high specificity and sensitivity. By Western blot analysis and immunohistochemistry (IHC) staining, we demonstrate that TDRD1 protein is expressed in the majority of human prostate tumors, but not in normal prostate tissue. Finally, TDRD1 is not induced in the prostate of ERG overexpression transgenic mice, suggesting that such model does not fully recapitulate the TMPRSS2/ERG fusion-dependent human prostate cancer development. Our results suggest TDRD1 as a novel prostate cancer biomarker. As an ERG target gene, TDRD1 might play an important role in human prostate cancer development, and as a cancer/testis antigen, TDRD1 might have long-term potential to be a therapeutic target for prostate cancer immunotherapy. Prostate 76:1271-1284, 2016. © 2016 Wiley Periodicals, Inc.

The role of mesenchymal stem cells in promoting the transformation of androgen-dependent human prostate cancer cells into androgen-independent manner.

Mesenchymal stem cells (MSCs) play an important role in the development of human prostate cancer (PCa). However, the role of MSCs in the transformation of androgen-dependent human PCa cells into androgen-independent manner has been poorly understood. In this study, we investigated the underlying mechanism of MSCs in promoting PCa cells from androgen-dependent into androgen-independent manner. Firstly, we demonstrated that MSCs could affect the transformation of androgen-dependent human PCa cells into androgen-independent manner in vivo and in vitro. Then we found a substantial expression of TGF-β in MSCs. TGF-β blockade could significantly inhibit the promotive function of MSCs in PCa cells. Besides that, we also demonstrated androgen might inhibit the expression of TGF-β in MSCs. Furthermore, we found that either overexpression of SSEA-4 or the number of SSEA-4 positive MSCs in PCa tissues was associated with a shorter cancer-free survival interval (CFSI) and a worse overall survival (OS). Our results suggest that androgen blockade treatment in clinical PCa therapy may elicit the expression of TGF-β in MSCs, which will result in the transformation of androgen-dependent human PCa cells into androgen-independent manner.

Abstract B18: Myc governs a prostate epithelial differentiation program involving chromatin remodeling protein ING4 and Notch3: Disruption of which is necessary for human prostate cancer development

Abstract Myc is overexpressed in the majority of human prostate cancers and is a known determinant of cell fate, yet the cell of origin from which prostate cancers arise is controversial. Furthermore, the mechanisms by which oncogenes such as Myc disrupt prostate epithelial cell fate are poorly understood. Using a novel human in vitro differentiation model in which prostate basal epithelial cells are induced to differentiate into lumenal cells, we previously demonstrated that Myc-driven prostate cancer develops in an intermediate progenitor cell population whose full differentiation is derailed upon oncogenic transformation (Berger et al, Cancer Res 74:3357-68, 2014). In basal prostate epithelial cells, Myc is required for transient expression of the chromatin-binding protein ING4, which is required for lumenal cell differentiation. In human tissues, ING4 expression is lost in >60% of primary prostate tumors. Loss of ING4 prevented differentiation and was necessary for Myc-dependent tumorigenesis in vivo. ING4 loss generated Myc-dependent tumor cells co-expressing basal and lumenal markers, indicating Myc-dependent oncogenesis disrupted an intermediate step in the prostate epithelial differentiation program. Our objective for this study was to further elucidate the mechanisms by which Myc controls prostate epithelial cell fate. Myc is a known downstream target of Notch1, and several studies suggest Notch signaling is aberrant in prostate cancer; although the mechanistic details are vague. We found that Notch3 is required for lumenal cell differentiation and hypothesized that Notch3 expression is directly controlled by Myc. Inhibition of total Notch signaling with a γ-secretase inhibitor (RO4929097) prevented differentiation. Total Notch1 mRNA and protein levels change very little during differentiation; whereas both Notch3 mRNA and protein increase dramatically. Knock-down of Notch3 by shRNA blocked differentiation, while over expression of active Notch3 (NCID3) induced spontaneous differentiation. Less than 15% of the increase in Notch3 mRNA was attributable to increased mRNA stability, and required new protein synthesis. Temporally, Myc mRNA and protein levels increase prior to Notch3. Blocking Myc expression prevented Notch3 induction. The 2kb proximal promoter region of Notch3 lacked the elements that promote Notch3 induction. We identified a Notch3 enhancer element with Myc binding motifs that support differentiation-induced luciferase reporter activity. We further determined that p38α-MAPK is required for Myc and Notch3 induction. We are currently determining how Myc-dependent regulation of Notch3 influences Myc-dependent regulation of ING4. Thus, our studies demonstrate that at least 2 targets of Myc, ING4 and Notch3, control prostate epithelial cell fate, and that disruption of at least one of them is required for Myc-driven human prostate cancer development. In depth understanding of Myc-driven differentiation pathways will provide new insights into how oncogenic transformation by Myc in intermediate progenitor prostate epithelial cells gives rise to prostate cancer. Funding was provided by the Association for International Cancer Research, NIH/NCI CA154835, Department of Defense W81XWH-14-10479, and the Van Andel Research Institute. Citation Format: Sander B. Frank, Penny L. Berger, Cindy K. Miranti. Myc governs a prostate epithelial differentiation program involving chromatin remodeling protein ING4 and Notch3: Disruption of which is necessary for human prostate cancer development. [abstract]. In: Proceedings of the AACR Special Conference on Myc: From Biology to Therapy; Jan 7-10, 2015; La Jolla, CA. Philadelphia (PA): AACR; Mol Cancer Res 2015;13(10 Suppl):Abstract nr B18.

Abstract 267: Combining androgen deprivation with immune checkpoint blockade delays the development of castration resistance in a murine model of prostate cancer

Abstract Androgen deprivation therapy induces immune cell infiltration in human prostate cancer. These findings suggest that immunotherapy may be most efficacious when administered concurrently with androgen deprivation, early in disease progression. We used a subcutaneous allograft model of murine prostate cancer (Myc-Cap), which mimics the development of human castration-resistant prostate cancer (CRPC) progression to study the anti-tumor effects of concurrent hormonal/immunotherapy. Implanted Myc-Cap tumors initially respond to androgen deprivation (degarelix acetate or bilateral orchiectomy), but mice eventually progress with CRPC. To test the hypothesis that the combination of androgen deprivation and immune checkpoint blockade could mediate pre-clinical benefit, we treated mice with either anti-PD-1, a depleting anti-CTLA-4 antibody (IgG2A), a non-depleting anti-CTLA-4 antibody (IgG1 D265A) or antibody combinations in the peri-castration period, then followed mice for the development of castration-resistant disease. Interestingly, the depleting anti-CTLA-4 antibody with/without anti-PD-1 antibody was strikingly effective in preventing the emergence of castration-resistant disease. The median castration-resistance free survival was 22 days in mice treated with androgen deprivation alone versus 32 days in mice treated with androgen deprivation and depleting anti-CTLA-4 antibody (P<0.05, compared to androgen deprivation alone) versus 30 days in mice treated with androgen deprivation, depleting anti-CTLA-4 and anti-PD-1 (P<0.05, compared to androgen deprivation alone; non-significant, compared to androgen deprivation and depleting anti-CTLA-4 antibody). Immunologically, we found that castration increases intratumoral infiltration of helper, cytotoxic and regulatory T cells (Tregs), natural killer cells, and macrophages, as well as effector cytokine production of T cells. We also found up-regulated expression of CTLA-4 and PD-1 as well as their respective ligands. Mechanistic studies showed that androgen deprivation combined with depleting anti-CTLA-4 /anti-PD-1 significantly reduces intratumoral Tregs and increases interferon-γ- or tumor necrosis factor-α- producing T cells in the tumor and its draining lymph node. In conclusion, while androgen deprivation renders the tumor microenvironment more immunogenic; the combination of androgen deprivation and depleting anti-CTLA-4 antibody with/without anti-PD-1 can significantly delay the development of CRPC. Citation Format: Ying-Chun Shen, Christina Kochel, Brian J. Francica, Angela Alme, Christopher Nirschl, Thomas Nirschl, Zoila Areli Lopez Bujanda, Maria A. Carrera H, Mark Selby, Alan Korman, Charles G. Drake. Combining androgen deprivation with immune checkpoint blockade delays the development of castration resistance in a murine model of prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 267. doi:10.1158/1538-7445.AM2015-267

Crosstalking between Androgen and PI3K/AKT Signaling Pathways in Prostate Cancer Cells

Both androgen action and PI3K medicated signaling pathways have been implicated in prostate tumorigenesis. Our androgen receptor (AR) conditional transgenic mice developed murine prostatic intraepithelial neoplasia (mPIN) and prostatic adenocarcinoma lesions recapitulating human prostate cancer development and progression. Role of transgenic AR contributing to malignancy was demonstrated by high degree of transgenic AR expression in atypical and tumor cells in mPIN as well as prostatic adenocarcinoma lesions of the transgenic mice, but not in adjacent normal tissue. Interestingly, reduced PI3K/Akt activation also appeared in these mouse atypical and tumor cells, suggesting an interaction between androgen and PI3K/AKT pathways. In this study, we further investigated this interaction. We showed that the androgen depletion or knockdown of AR expression results in elevated levels of active phosphorylated AKT in prostate cancer cells. Castration of conditional Pten knock-out mice showed increased Akt, phosphorylated Akt, and pS6 expression in the mouse prostate. Using a series of newly generated Ar reporter and Pten knock-out compound mice, we showed that Pten loss directly represses endogenous Ar expression in prostatic epithelial cells. Moreover, Pten loss and PI3K/Akt activation reduced Ar-mediated transcription in purified Pten-null cells. This study provides novel evidence demonstrating interplay between androgen and PI3K pathways, as well as introduces unique and relevant mouse models for further studies of PI3K and AR pathways in the context of prostate tumorigenesis.

SPAG9 expression is increased in human prostate cancer and promotes cell motility, invasion and angiogenesis in vitro.

Sperm-associated antigen 9 (SPAG9) is a recently characterized oncoprotein involved in the progression of several human malignancies. To elucidate the role of SPAG9 in the development of human prostate cancer (PCa), tissue microarray (TMA) and immunohistochemistry were used to detect the clinical relevance of SPAG9 in PCa tissues. We found that SPAG9 expression was increased in the PCa tissues when compared with the level in the tumor adjacent normal prostate tissues, and increased SPAG9 staining was significantly correlated with TNM stage and tumor grade. We also examined prostate cancer cell motility, invasion and angiogenesis ability following reduced SPAG9 expression by siRNA. Our data showed that knockdown of SPAG9 in prostate cancer cell lines inhibited cell motility and invasion due to the inactivation of metalloproteinase-2 (MMP‑2)/MMP-9 by upregulation of tissue inhibitor of metalloproteinase-1 (TIMP-1)/TIMP-2. Furthermore, downregulation of vascular endothelial growth factor (VEGF) secretion greatly contributed to the reduced ability of angiogenesis. Our data indicate that SPAG9 expression is significantly increased in PCa and it may be involved in the process of prostate cancer cell motility, migration and angiogenesis.

EphA3, induced by PC-1/PrLZ, contributes to the malignant progression of prostate cancer.

Our previous study revealed the potential linkage of PC-1/PrLZ, a novel isolated prostate-specific gene, to the progression of prostate cancer (PCa) in vitro and in vivo. To gain more insight into the mechanism of PC-1-induced promotion of PCa, expression analysis of differential genes induced by PC-1 was scanned by microarray. Among all the differentially expressed genes, EphA3 was altered to the greatest extent. EphA3 has been identified to be associated with multiple tumor progression. However, little is known concerning the function of EphA3 in PCa. In the present study, we aimed to ascertain whether EphA3 is induced by PC-1 and the functional significance of EphA3 expression in PCa. We found that overexpression of PC-1 increased the amount of EphA3 and that knockdown of PC-1 led to a decrease in EphA3 in PCa cells. The functional significance and mechanisms by which EphA3 contributes to PCa was investigated in vitro using cell lines, and in vivo using a mouse model and clinical specimens. The results showed that EphA3 enhanced the proliferation and survival of LNCaP cells and suppression of EphA3 inhibited the survival of C4-2B cells. EphA3 enhanced the tumor development of LNCaP cells in null mice. A positive correlation between the levels of EphA3 and the Gleason grade of PCa was identified in clinical PCa specimens. In addition, cellular localization changed with Gleason grade. We further detected that EphA3 increased phosphorylation of Akt (Ser473 and Thr308), indicating that EphA3 activated the Akt pathway. Taken together, EphA3 was induced by PC-1 and contributed to the malignant progression of prostate cancer. Our results provide the first demonstration that EphA3 is a novel promoter of human prostate cancer development and progression.

Targeting Heat Shock Proteins in Prostate Cancer

Heat shock proteins (HSPs) and chaperones are highly conserved stress-induced factors. They regulate not only protein folding and stability but are also actively involved in protein transport and transcriptional regulation. HSPs have cytoprotective roles and are essential for cancer cell survival. Noteworthy, HSPs are often upregulated in cancer. Therefore, HSPs emerged as drug targets for cancer therapy. Especially for prostate cancer (PCa) therapy, a battery of different compounds has been identified that act with different modes to inhibit PCa growth. The androgen receptor (AR) is a major player in PCa progression and is a well-known interacting factor of HSPs. Since the AR function is very dependent on HSP activity, many emerging compounds address the AR-associated HSPs as novel drug targets. Here, we provide an insight into the different classes of HSPs, their association with the human AR, the role of HSPs in human PCa development and review also the targeting of HSPs in human PCa. Further, the function and the underlying molecular mechanisms of specific compounds that are currently under investigation for the use against PCa growth will be comprehensively summarized.

SGEF is overexpressed in prostate cancer and contributes to prostate cancer progression

The purpose of this study was to investigate the potential roles of the SH3-containing guanine nucleotide exchange factor (SGEF) in human prostate cancer. Experimental data showed that SGEF was overexpressed in human prostate cancer cells and specimens. The reduction of SGEF expression through an SGEF-targeting siRNA in androgen-independent C4-2 and C4-2B cells suppressed both anchorage-dependent and anchorage-independent growth. In addition, the androgen receptor (AR) antagonist bicalutamide further strengthened this inhibitory effect due to the suppression of the elevated AR transactivation after knockdown of SGEF. Collectively, our results provide the first demonstration that SGEF is a novel promoter of human prostate cancer progression and development.