Androgen receptor: good guy or bad guy in prostate cancer invasion?

Pro-angiogenic effect of PC-3 exosomes in endothelial cells in vitro

The progression to a castration-resistant prostate cancer can occur after treatment with androgen deprivation therapy, resulting in poor prognosis and ineffective therapy response. Hormone dependence transition has been associated with increased tumor vascularization. Considering that exosomes are important components in communication between tumor cells and the microenvironment, we examined the angiogenic potential of exosomes released from Pca cell lines with distinctive profiles of androgen response through exosomes isolation, microscopy and uptake, functional assays follow up by microarray, RT-qPCR and bioinformatics analysis. HUVEC cells treated with PC-3 exosomes (androgen independent) showed increased invasion and tube formation ability. In order to identify microRNAs (miRNAs) related to the angiogenic response, the characterization of exosomal miRNA profile was performed. As result we suggest that the miR-27a-3p could be involved in the pro-angiogenic effect of PC-3 exosomes.

Role of Stromal Paracrine Signals in Proliferative Diseases of the Aging Human Prostate

Androgens are essential for the development, differentiation, growth, and function of the prostate through epithelial–stromal interactions. However, androgen concentrations in the hypertrophic human prostate decrease significantly with age, suggesting an inverse correlation between androgen levels and proliferative diseases of the aging prostate. In elderly males, age- and/or androgen-related stromal remodeling is spontaneously induced, i.e., increased fibroblast and myofibroblast numbers, but decreased smooth muscle cell numbers in the prostatic stroma. These fibroblasts produce not only growth factors, cytokines, and extracellular matrix proteins, but also microRNAs as stromal paracrine signals that stimulate prostate epithelial cell proliferation. Surgical or chemical castration is the standard systemic therapy for patients with advanced prostate cancer. Androgen deprivation therapy induces temporary remission, but the majority of patients eventually progress to castration-resistant prostate cancer, which is associated with a high mortality rate. Androgen deprivation therapy-induced stromal remodeling may be involved in the development and progression of castration-resistant prostate cancer. In the tumor microenvironment, activated fibroblasts stimulating prostate cancer cell proliferation are called carcinoma-associated fibroblasts. In this review, we summarize the role of stromal paracrine signals in proliferative diseases of the aging human prostate and discuss the potential clinical applications of carcinoma-associated fibroblast-derived exosomal microRNAs as promising biomarkers.

Regulation and methylation of tumor suppressor miR-124 by androgen receptor in prostate cancer cells

Prostate cancer (PCa) is the most frequently diagnosed cancer for men in the developed world. Androgen receptor signaling pathway plays an important role in prostate cancer progression. Recent studies show that microRNA miR-124 exerts a tumor suppressive function in prostate cancer. However, the relationship between AR and miR-124 is unclear. In the present study, we found a negative feedback loop between AR and miR-124 expression. On one hand, miR-124 was a positively regulated target gene of the AR, on the other hand, overexpression of miR-124 inhibited the expression of AR. In addition, we found that miR-124-2 and miR-124-3 promoters were hypermethylated in AR-negative PCa cells. Furthermore, overexpression of miR-124 inhibited proliferation rates and invasiveness capacity of PCa cells in vitro, and suppressed xenograft tumor growth in vivo. Taken together, our results support a negative feedback loop between AR and miR-124 expression. Methylation of miR-124-2 and miR-124-3 may serve as a biomarker for AR-negative PCa cells, and overexpression of miR-124 might be of potential therapeutic value for the treatment of PCa.

Overexpression of α (1,6) fucosyltransferase associated with aggressive prostate cancer

Aberrant protein glycosylation is known to be associated with the development of cancers. The aberrant glycans are produced by the combined actions of changed glycosylation enzymes, substrates and transporters in glycosylation synthesis pathways in cancer cells. To identify glycosylation enzymes associated with aggressive prostate cancer (PCa), we analyzed the difference in the expression of glycosyltransferase genes between aggressive and non-aggressive PCa. Three candidate genes encoding glycosyltransferases that were elevated in aggressive PCa were subsequently selected. The expression of the three candidates was then further evaluated in androgen-dependent (LNCaP) and androgen-independent (PC3) PCa cell lines. We found that the protein expression of one of the glycosyltransferases, α (1,6) fucosyltransferase (FUT8), was only detected in PC3 cells, but not in LNCaP cells. We further showed that FUT8 protein expression was elevated in metastatic PCa tissues compared to normal prostate tissues. In addition, using tissue microarrays, we found that FUT8 overexpression was statistically associated with PCa with a high Gleason score. Using PC3 and LNCaP cells as models, we found that FUT8 overexpression in LNCaP cells increased PCa cell migration, while loss of FUT8 in PC3 cells decreased cell motility. Our results suggest that FUT8 may be associated with aggressive PCa and thus is potentially useful for its prognosis.

Quality of Life and Sexual Health in the Aging of PCa Survivors

Prostate cancer (PCa) is the most common malignancy in elderly men. The progressive ageing of the world male population will further increase the need for tailored assessment and treatment of PCa patients. The determinant role of androgens and sexual hormones for PCa growth and progression has been established. However, several trials on androgens and PCa are recently focused on urinary continence, quality of life, and sexual function, suggesting a new point of view on the whole endocrinological aspect of PCa. During aging, metabolic syndrome, including diabetes, hypertension, dyslipidemia, and central obesity, can be associated with a chronic, low-grade inflammation of the prostate and with changes in the sex steroid pathways. These factors may affect both the carcinogenesis processes and treatment outcomes of PCa. Any treatment for PCa can have a long-lasting negative impact on quality of life and sexual health, which should be assessed by validated self-reported questionnaires. In particular, sexual health, urinary continence, and bowel function can be worsened after prostatectomy, radiotherapy, or hormone treatment, mostly in the elderly population. In the present review we summarized the current knowledge on the role of hormones, metabolic features, and primary treatments for PCa on the quality of life and sexual health of elderly Pca survivors.

Androgen Regulation of JM-27 Is Associated With the Diseased Prostate

Despite intense research efforts, the etiology of prostatic hyperplasia associated with both benign prostatic hyperplasia (BPH) and prostate cancer remains poorly understood. Our previous studies using array technology identified JM-27 as a transcript that is dramatically up-regulated in the prostates of patients with symptomatic BPH and in normal, adjacent prostatic regions of patients with prostate cancer. In the present study, using an extended sample set, we show a correlation between the messenger RNA and protein expression of JM-27. To investigate the possible functions of this gene, its expression in the rat prostate was examined by immunoblot analysis using a polyclonal antibody specific to human JM-27. This antibody reacts with 2 rat polypeptides of 17 kd and 27 kd in size. Whereas the 27-kd form of the JM-27 protein found in human prostate is selectively expressed in the dorsolateral lobes of the rat prostate, the 17-kd form is expressed only in the ventral lobe. Expression of both forms of this protein appears to be androgen-regulated. There is a time-dependent decrease in expression of the protein products in the ventral and dorsolateral lobes of the rat prostate after castration. Administration of exogenous testosterone in castrated animals maintains protein expression in both lobes. Androgens are believed to play a central role in prostate growth and development, and therefore, it is tempting to speculate that JM-27, an androgen-regulated gene, may be involved in prostatic growth regulation. Further studies are underway to evaluate such a function for JM-27 in prostatic diseases.

Characterization of the low pH/low nutrient-resistant LNCaP cell subline LNCaP-F10

Intratumoral regions of low extracellular pH and low nutrition are common features of solid tumors. Although cancer cells normally die when they are removed from their environment, a small population of cells survive. In the present study, the subline LNCaP-F10, of the prostate cancer cell line LNCaP, was isolated and its low pH/low nutrient-resistant properties were examined. LNCaP-F10 cells were grown under low-pH/low-nutrient conditions, which caused cell death of the LNCaP cells. The cell death was associated with oligonucleosomal DNA fragmentation and poly (ADP-ribose) polymerase (PARP) cleavage, indicating that low-pH/low-nutrient induced apoptosis in these cells. Significant differences in the expression of BCL2, BIRC5 and DAPK1 were detected between LNCaP-F10 and LNCaP cells. Tumor growth caused by implantation of LNCaP-F10 cells into the renal subcapsular space of nude mice in the absence or presence of prostate stromal cell stimulation was greater than that caused by implantation of LNCaP cells. LNCaP-F10 cells were resistant to apoptosis induced by an environment of low-pH/low-nutrient in vitro, and displayed malignant potential in vivo.

Androgen regulation of prostate cancer: where are we now?

BACKGROUND

Androgens play an essential role in the development and differentiation of the prostate gland; their contribution to pathological conditions, such as benign prostatic hyperplasia and prostate cancer (PC), remains unclear.

AIM

We reviewed relationships between androgens and the prostate both in physiological and pathological conditions.

MATERIAL AND METHODS

A systematic search of published evidence was performed using Medline (1969 to September 2010).

RESULTS

Androgen-dependency of prostate growth is evident only in the hypogonadal condition, but not in the eugonadal state (the "saturation hypothesis"). There is unequivocal evidence that reducing androgen signaling to the hypogonadal range can reduce PC growth and patient symptoms. At physiological testosterone concentration there is no link between androgen levels and PC risk. In addition, different strategies of androgen deprivation (ADT) for advanced PC are only palliative and rarely cure patients. Preliminary evidence indicates that a low androgen milieu is associated with tumor aggressiveness. Transition to androgen-independence is complex and involves both selection and outgrowth of preexisting androgen resistant clones, as well as adaptative upregulation of genes that help the cancer cells to survive and grow after ADT. Because androgens are essential for the regulation of fat distribution, insulin sensitivity, and lipid and bone metabolism, recent publications have highlighted the concept that ADT may also be involved with an increase in overall, as well as cardiovascular, morbidity and mortality.

CONCLUSIONS

While ADT still represents a cornerstone for the palliative therapy of a small fraction of aggressive PC, a "misuse and/or abuse" of ADT should be avoided.

5-Azacitidine restores and amplifies the bicalutamide response on preclinical models of androgen receptor expressing or deficient prostate tumors

BACKGROUND

Epigenetic modifications play a key role in the in prostate cancer (Pca) progression to a hormone refractory state (HRPC) and the current use of agents targeting epigenetic changes has become a topic of intense interest in cancer research. In this regard, 5-Azacitine (5-Aza) represents a promising epigenetic modulator. This study tested the hypothesis that 5-Aza may restore and enhance the responsiveness of HRPC cells to anti-hormonal therapy on Androgen receptor (AR) expressing (22rv1) and AR-deficient (PC3) cells.

METHODS

The effects were studied in vitro and in vivo models. This sequential treatment induced in vitro cell cycle arrest and apoptosis both in 22rv1 and PC3 tumor cell lines.

RESULTS

This combined treatment up-regulated the expression of FasL, phospho-FADD, p16(INKA), Bax, Bak, and p21(WAF1), and inhibited FLIP, Bcl-2, and Bcl-XL expression. The re-activation of hormonal response of AR-negative PC3 cell line was partially due to the AR re-expression mediated by 5-Aza treatment. In contrast, the increase in the response to anti-androgenic therapy in 22rv1 did not correlate with AR expression levels. Furthermore, xenograft studies revealed that the combined treatment of 5-Aza with AR-antagonist Bicalutamide had additive/synergistic effects in repressing tumor growth in vivo and the underlying mechanisms responsible for these effects seem to be in part mediated by induction of apoptosis.

CONCLUSIONS

So, this study strongly suggests a therapeutic potential of 5-Aza in combination with anti-androgen therapy in patients with in AR expressing and AR-deficient HRPC.

Improvement in predicting tumorigenic phenotype of androgen-insensitive human LNCaP prostatic cancer cell subline in recombination with rat urogenital sinus mesenchyme

Hormone-refractory prostate cancer, a heterogeneous disease, has varying degrees of androgen sensitivity. To understand the physiological changes in the hormone-refractory state, the present study used a lineage-derived androgen receptor (AR)-positive, androgen-insensitive prostate cancer cell line and evaluated the tumorigenic phenotype, focusing on tumor-stromal interactions in vivo. First, tumorigenic differences of cancer cells alone were examined in an androgen-insensitive AR-positive LNCaP subline, AIDL, compared with those of the androgen-sensitive AR-positive parental LNCaP and the androgen-insensitive AR-negative PC-3 cells transplanted into subcutaneous, sub-renal and prostatic orthotopic graft sites. Next, cancer cells were recombined with rat urogenital sinus mesenchyme (rUGM) to simulate the tumor-stromal microenvironment. Tumors of AIDL and LNCaP without stromal components both formed well-defined globular tumors and contained large blood-filled areas, with no significant difference in tumor growth or histopathology regardless of the cell line's androgen sensitivity or graft site. In contrast, tumors of AIDL and LNCaP recombined with rUGM both showed reduction of blood-filled areas in the tumors and increased tumor growth compared with cancer cells alone. Tumors of AIDL + rUGM recombinants were approximately three times as large as those of LNCaP + rUGM recombinants, whereas tumors of AIDL and LNCaP without rUGM were not different in size. In addition to the tumor size, cell proliferation (Ki-67 labeling index) in tumors of AIDL + rUGM recombinants was significantly higher than that in tumors of LNCaP + rUGM recombinants. Immunoreactivities of AR, E-cadherin and beta-catenin were decreased in AIDL + rUGM recombinants relative to AIDL alone and LNCaP + rUGM recombinants. These results demonstrated that tumorigenic features of androgen-insensitive AR-positive prostate cancer cells could be significantly influenced by rUGM. Therefore, this in vivo recombination model with rUGM may be useful in developing new treatment strategies.

Chronic azacitidine treatment results in differentiating effects, sensitizes against bicalutamide in androgen-independent prostate cancer cells

BACKGROUND

About 20-30% of hormone-independent PCa are characterized by the extensive loss of AR expression that appears to occur at the transcriptional level. Treatment of AR-negative PCa cells with demethylating agents (Aza-CR) leads to expression of AR mRNA and protein. Here, we investigate the effect of Aza-CR administered both acutely and chronically on AR expression, PSA expression, cell survival, and proliferation in androgen-independent/AR-negative PCa cells. We also studied whether epigenetically reactivated AR is a target for bicalutamide therapy.

METHODS

The in vitro effect of Aza-CR as single agent and its ability to induce AR expression and to augment the efficacy to bicalutamide were assessed using two androgen-independent and AR-negative cell lines (PC3 and DU145).

RESULTS

Our results show that acute treatment (4 days) with Aza-CR results in a relatively low decrease in cell proliferation with G2 cell cycle arrest and no significant evidence of apoptosis or AR expression. Interestingly, when Aza-CR was chronically administered (20 days), this treatment resulted in marked decrease in tumor cell proliferation with significant increase in AR and PSA protein levels. Furthermore, following Aza-CR chronic treatment the formerly androgen-independent PC3 and DU145 cells increase their susceptibility to the apoptotic effects of bicalutamide.

CONCLUSIONS

Aza-CR acute treatment has modest effects on androgen-independent and AR-negative PCa cell survival and proliferation, but chronic administration results in profound decrease in proliferation and in sensitization to antiandrogen agents. All these effects seem, in some measure, dependent on a partial restoration of androgen regulation.

Androgen receptor and invasion in prostate cancer

Activation of androgen receptor (AR) stimulates the growth of not only androgen-dependent but also of androgen-refractory prostate cancer. However, neither the role of AR in invasion/metastasis nor the relationship between invasiveness and androgen-refractory status has been established. In this study, we used the androgen-dependent prostate cancer cell line MDA PCa 2b, derived from a human bone metastasis, to generate an invasive subline (MDA-I) using a Matrigel chamber. MDA-I cells expressed higher levels of AR and prostate-specific antigen than their less invasive parental cells. Blocking AR function or removal of androgen suppressed the invasion of MDA-I cells, whereas stimulating AR increased invasion. In addition, forced AR overexpression increased the invasiveness of MDA PCa 2b cells. Next, we showed that an androgen-refractory subline (MDA-hr) of MDA PCa 2b cells also expressed higher levels of AR and were more invasive than their parental androgen-dependent cells. Blocking AR function suppressed the invasiveness of MDA-hr cells. Gelatin zymography indicated that matrix metalloproteinase 2 (MMP-2) and MMP-9 activities were regulated by AR signaling and closely correlated with the invasiveness of the androgen-dependent and androgen-refractory prostate cancer cells. These data suggest that AR promotes the invasiveness of both androgen-dependent and androgen-refractory prostate cancer and that a more invasive phenotype might develop through AR activation during cancer progression. These findings potentially support the use of adjuvant hormonal therapy and the future development of more potent androgen blockade therapy.

Non-genomic effects of the androgen receptor and vitamin D agonist are involved in suppressing invasive phenotype of prostate cancer cells

Suppression of invasive phenotype is essential in developing new therapeutic tools to treat prostate cancer (PC). Evidence indicates that androgen-dependent (AD) prostate cancer cells are characterized by a lower malignant phenotype. We have demonstrated that transfection with an androgen receptor (AR) expression vector of the androgen-independent (AI) prostate cancer cell line PC3 decreases invasion of these cells through modulation of alpha6beta4 integrin expression, indicating a genotropic effect of androgens in inhibiting invasion ability of AD PC cells. Later on, we have shown that also a non-genotropic mechanism is involved in such an effect. By using immunoconfocal fluorescent microscopy, we demonstrated that AR in PC3-AR cells co-localizes with the EGFR receptors (EGFR) in PC3-AR cells. Co-immunoprecipitation studies both in PC3-AR cells and in the AD cell line LNCaP that physiologically express both receptors, confirm the occurrence of an interaction between of the two proteins. In PC3-AR cells, we demonstrated a disruption of EGFR signalling properties (reduced EGF-induced EGFR autotransphosphorylation, reduced EGF-stimulated PI3K activity as well as EGFR-PI3K interaction) contributing to the lower invasive phenotype of these cells. In another study, we investigated the effects of a new Vitamin D analogue, BXL628, on invasion in response to KGF in the androgen-independent PC cell line DU145. We found that the compound was able to reduce proliferation and invasion of the cells in response to the growth factor. In addition, we found that KGF-induced autotransphosphorylation of KGF receptor (KGFR) and PI3K activation were suppressed after short-term (5min) pre-treatment with the analogue before addition of KGF. Collectively, these studies demonstrate that a non-genotropic effect due to a direct interaction of the androgen receptor with EGFR and to a rapid effect of a Vitamin D agonist on KGFR may disrupt signalling of GF leading to decreased tumorigenicity and a less malignant phenotype of PC cells in vitro.

The androgen receptor and prostate cancer invasion

Recent evidence indicates that androgen-sensitive prostate cancer cells are characterized by a less pronounced malignant phenotype. We demonstrate that transfection with an androgen receptor (AR) expression vector of the androgen-independent (AI) prostate cancer cell line PC3 decreases invasion and adhesion of these cells through modulation of alpha6beta4 integrin expression. Treatment of PC3-AR cells with the synthetic androgen R1881 further reduced invasion without modifying alpha6beta4 expression on the cell surface, suggesting interference with the invasion process in response to EGF by an alternative mechanism. We investigated EGF-induced auto-transphosphorylation of EGFR in both cell lines. We found that EGFR auto-transphosphorylation was reduced in PC3-AR cells and was further decreased by administration of androgens. Since auto-transphosphorylation regulates many different functions of EGFR, including docking of kinases, ubiquitination and internalization, we next investigated all these processes in PC3-AR cells. EGF-stimulated PI3K activity, a key signalling pathway for invasion of these cells, was decreased in PC3-AR cells and further reduced by treatment with R1881. Interestingly, EGFR-PI3K interaction was also disrupted in these cells. Furthermore, EGFR ubiquitination and internalization were found to be reduced in PC3-AR cells both in basal conditions and following treatment with androgens. According to recent findings, an endocytotic pathway may be important for EGFR signalling by controlling the specificity of the response. By using immunoconfocal fluorescent microscopy, we demonstrated that AR in PC3 cells is mainly located in cytoplasm and transmigrates in part to the nucleus following stimulation with androgens. Interestingly, immunoconfocal and immunoprecipitation experiments demonstrated also the occurrence of co-localization and interaction of AR with EGFR in PC3-AR cells and in another androgen-dependent PC cell line, LNCaP. We hypothesize a mechanism by which, through direct interaction with EGFR, the AR elicits a reduction of EGF-mediated signalling and confers a less malignant phenotype.

The vitamin D analogue BXL-628 inhibits growth factor-stimulated proliferation and invasion of DU145 prostate cancer cells

PURPOSE

Suppression of the invasive phenotype is essential in developing new therapeutic tools to treat advanced prostate cancer (PC) indicating that androgen-independent prostate cancer (AI-PC) is characterized by increased metastatic potential. In the present study, we have investigated the effect of the nonhypercalcemic vitamin D analogue BXL-628 on proliferation and invasive properties of the human PC cell line DU145. In particular, the effect of the analogue was tested following stimulation with a potent growth factor, keratinocyte growth factor (KGF), which stimulates both proliferation and invasion of these cells. We have also evaluated the effect of the analogue on KGF stimulation of PI3K/AKT signaling pathway.

METHODS

Cell proliferation was determined by cell counting. Invasion through Matrigel was evaluated using Boyden chambers. PI3K activity was measured by immunokinase assay and AKT phosphorylation was evaluated by western blot analysis. Keratinocyte growth factor receptor (KGFR) autotransphosphorylation was evaluated by western blot after immunoprecipitation of the receptor.

RESULTS

BXL-628 is able to inhibit both proliferation and invasion of DU145 cells in basal conditions and in response to KGF. Following stimulation with KGF, the inhibition is due to suppression of KGFR autotransphosphorylation and downstream PI3K/AKT activation, both achieved following a brief (5 min) incubation with the analogue. This effect on KGFR autophosphorylation was still present when cells were treated with the alpha-amanitin, an inhibitor of RNA transcription, indicating a rapid, nongenomic effect.

CONCLUSIONS

Our results demonstrate that the vitamin D analogue BXL-628 is able to suppress KGF-induced proliferation and invasion of AI-PC cells in vitro, prospecting a possible use of the drug, which is currently in phase II clinical studies for benign prostatic hyperplasia, in the treatment of advanced prostate cancer.