Growth Of Androgen-dependent Prostate Cancer Cells Research Articles

Interleukin-10 Induces Expression of Neuroendocrine Markers and PDL1 in Prostate Cancer Cells.

Interleukin-10 (IL10) is best studied for its inhibitory action on immune cells and ability to suppress an antitumour immune response. But IL10 also exerts direct effects on nonimmune cells such as prostate cancer epithelial cells. Elevated serum levels of IL10 observed in prostate and other cancer patients are associated with poor prognosis. After first-line androgen-deprivation therapy, prostate cancer patients are treated with androgen receptor antagonists such as enzalutamide to inhibit androgen-dependent prostate cancer cell growth. However, development of resistance inevitably occurs and this is associated with tumour differentiation to more aggressive forms such as a neuroendocrine phenotype characterized by expression of neuron specific enolase and synaptophysin. We found that treatment of prostate cancer cell lines in vitro with IL10 or enzalutamide induced markers of neuroendocrine differentiation and inhibited androgen receptor reporter activity. Both also upregulated the levels of PDL1, which could promote tumour survival in vivo through its interaction with the immune cell inhibitory receptor PD1 to suppress antitumour immunity. These findings suggest that IL10's direct action on prostate cancer cells could contribute to prostate cancer progression independent of IL10's suppression of host immune cells.

Repression of Androgen Receptor Activity by HEYL, a Third Member of the Hairy/Enhancer-of-split-related Family of Notch Effectors

The Hairy/Enhancer-of-split-related with YRPW-like motif (HEY) family of proteins are transcriptional repressors and downstream effectors of Notch signaling. We previously reported that HEY1 and HEY2 selectively repress androgen receptor (AR) signaling in mammalian cell lines and have shown that in human tissue HEY1 is excluded from the nuclei in prostate cancer but not benign prostatic hyperplasia. We have now characterized a third member of this family, HEYL, which is a more potent repressor of AR activity. HEYL interacted with and repressed AR activation function-1 domain and competitively inhibited SRC1e activation of AR transcriptional activity. Using a cell line inducibly expressing exogenous HEYL, we showed that HEYL represses endogenous AR-regulated genes and reduces androgen-dependent prostate cancer cell growth. Using a trans-repression assay, we identified both trichostatin-sensitive and -insensitive domains within HEYL; however, analysis of endogenous AR target genes suggested that HEYL represses AR activity through histone deacetylase I/II-independent mechanisms. Immunohistochemical analyses of tissue indicated that, in a fashion similar to that previously reported for HEY1, HEYL is excluded from the nuclei in prostate cancer but not adjacent benign tissue. This suggests that nuclear exclusion of HEY proteins may be an important step in the progression of prostate cancer.

Abstract 249: Inhibition of protein phosphatase 2A supports androgen-independent growth of prostate cancer cells

Abstract Clinical progression of prostate cancer (PCa) is characterized by a transition from androgen-dependent (AD) to androgen-independent (AI) stage. Once the PCa has recurred in AI form, it progresses to a highly aggressive disease and poses an increased risk of morbidity and death. Therefore, understanding the mechanisms involved in AI progression of PCa is a significant area of research. Earlier, we identified PPP2CA, which encodes for alpha-isoform of the protein phosphatase 2A catalytic subunit (PP2Acα), as one of the downregulated genes in AI PCa cells. PP2A is a ser/thr phosphatase and a potent tumor suppressor involved in broad cellular functions; however, its role in PCa has not yet been determined. Here, we have investigated the effect of PP2A downregulation on the growth of AD PCa (LNCaP) cells under steroid-deprived condition. Furthermore, we have examined the effect of PP2A inhibition on the signaling pathways and delineated their role in AI growth of LNCaP cells. Our data show that the downregulation of PP2A activity by pharmacological inhibition or siRNA-mediated PPP2CA silencing sustains the growth of AD PCa cells under androgen-deprived condition by relieving the androgen-deprivation-induced cell cycle arrest and preventing apoptosis. Immunoblot analysis revealed enhanced phosphorylation of Akt, ERK, BAD, increased expression of cyclins (cyclin A1 and cyclin D1) and decreased expression of cyclin inhibitor (p27) upon PP2A downregulation. Furthermore, our data show that PP2A inhibition partially maintains AR signaling through its increased expression and ligand-independent phosphorylation, which is also supported by AR transcriptional activity assay and its target gene, KLK3, expression. Pharmacological inhibition of Akt, ERK and AR confirmed a role of these signaling pathways in facilitating the AI growth of LNCaP cells. Altogether, our findings suggest that modulation of PP2A activity may represent an alternative therapeutic approach for the treatment of advanced androgen-independent prostate cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 249. doi:10.1158/1538-7445.AM2011-249

FKBP51 and Cyp40 are positive regulators of androgen-dependent prostate cancer cell growth and the targets of FK506 and cyclosporin A

Prostate cancer (PCa) growth is dependent on androgens and the androgen receptor (AR), which acts by modulating gene transcription. Tetratricopeptide repeat (TPR) proteins (FKBP52, FKBP51 and Cyp40) interact with AR in PCa cells, suggesting roles in AR-mediated gene transcription and cell growth. We report here that FKBP51 and Cyp40, but not FKBP52, are significantly elevated in PCa tissues and in androgen-dependent (AD) and -independent (AI) cell lines. Overexpression of FKBP51 in AD LNCaP cells increased AR transcriptional activity in the presence and absence of androgen, whereas siRNA knockdown of FKBP51 dramatically decreased AD gene transcription and proliferation. Knockdown of Cyp40 also inhibited androgen-mediated transcription and growth in LNCaP cells. However, disruption of FKBP51 and Cyp40 in the AI C4-2 cells caused only a small reduction in proliferation, indicating that Cyp40 and FKBP51 predominantly regulate AD cell proliferation. Under knock-down conditions, the inhibitory effects of TPR ligands, CsA and FK506, on AR activity were not observed, indicating that Cyp40 and FKBP51 are the targets of CsA and FK506, respectively. Our findings demonstrate that FKBP51 and Cyp40 are positive regulators of AR that can be selectively targeted by CsA and FK506 to achieve inhibition of androgen-induced cell proliferation. These proteins and their cognate ligands thus provide new strategies in the treatment of PCa

Sphingosine Kinase-1 Is Central to Androgen-Regulated Prostate Cancer Growth and Survival

BackgroundSphingosine kinase-1 (SphK1) is an oncogenic lipid kinase notably involved in response to anticancer therapies in prostate cancer. Androgens regulate prostate cancer cell proliferation, and androgen deprivation therapy is the standard of care in the management of patients with advanced disease. Here, we explored the role of SphK1 in the regulation of androgen-dependent prostate cancer cell growth and survival.Methodology/Principal FindingsShort-term androgen removal induced a rapid and transient SphK1 inhibition associated with a reduced cell growth in vitro and in vivo, an event that was not observed in the hormono-insensitive PC-3 cells. Supporting the critical role of SphK1 inhibition in the rapid effect of androgen depletion, its overexpression could impair the cell growth decrease. Similarly, the addition of dihydrotestosterone (DHT) to androgen-deprived LNCaP cells re-established cell proliferation, through an androgen receptor/PI3K/Akt dependent stimulation of SphK1, and inhibition of SphK1 could markedly impede the effects of DHT. Conversely, long-term removal of androgen support in LNCaP and C4-2B cells resulted in a progressive increase in SphK1 expression and activity throughout the progression to androgen-independence state, which was characterized by the acquisition of a neuroendocrine (NE)-like cell phenotype. Importantly, inhibition of the PI3K/Akt pathway—by negatively impacting SphK1 activity—could prevent NE differentiation in both cell models, an event that could be mimicked by SphK1 inhibitors. Fascinatingly, the reversability of the NE phenotype by exposure to normal medium was linked with a pronounced inhibition of SphK1 activity.Conclusions/SignificanceWe report the first evidence that androgen deprivation induces a differential effect on SphK1 activity in hormone-sensitive prostate cancer cell models. These results also suggest that SphK1 activation upon chronic androgen deprivation may serve as a compensatory mechanism allowing prostate cancer cells to survive in androgen-depleted environment, giving support to its inhibition as a potential therapeutic strategy to delay/prevent the transition to androgen-independent prostate cancer.