Chicken Ovalbumin Upstream Promoter-Transcription Factor II (COUP-TFII) regulates growth and patterning of the postnatal mouse cerebellum

COUP-TFII (also known as Nr2f2), a member of the nuclear orphan receptor superfamily, is expressed in several regions of the central nervous system (CNS), including the ventral thalamus, hypothalamus, midbrain, pons, and spinal cord. To address the function of COUP-TFII in the CNS, we generated conditional COUP-TFII knockout mice using a tissue-specific NSE-Cre recombinase. Ablation of COUP-TFII in the brain resulted in malformation of the lobule VI in the cerebellum and a decrease in differentiation of cerebellar neurons and cerebellar growth. The decrease in cerebellar growth in NSE^Cre/+/CII^F/F mice is due to reduced proliferation and increased apoptosis in granule cell precursors (GCPs). Additional studies demonstrated that insulin like growth factor 1 (IGF-1) expression was reduced in the cerebellum of NSE^Cre/+/CII^F/F mice, thereby leading to decreased Akt1 and GSK-3β activities, and the reduced expression of mTOR. Using ChIP assays, we demonstrated that COUP-TFII was recruited to the promoter region of IGF-1 in a Sp1-dependent manner. In addition, dendritic branching of Purkinje cells was decreased in the mutant mice. Thus, our results indicate that COUP-TFII regulates growth and maturation of the mouse postnatal cerebellum through modulation of IGF-1 expression.     

Divergent Androgen Receptor and Beta-Catenin Signaling in Prostate Cancer Cells

Despite decades of effort to develop effective therapy and to identify promising new drugs, prostate cancer is lethal once it progresses to castration-resistant disease. Studies show mis-regulation of multiple pathways in castration-resistant prostate cancer (CRPC), reflecting the heterogeneity of the tumors and also hinting that targeting androgen receptor (AR) pathway alone might not be sufficient to treat CRPC. In this study, we present evidence that the Wnt/β-catenin pathway might be activated in prostate cancer cells after androgen-deprivation to promote androgen-independent growth, partly through enhanced interaction of β-catenin with TCF4. Androgen-independent prostate cancer cells were more prone to activate a Wnt-reporter, and inhibition of the Wnt/β-catenin pathway increased sensitivity of these cells to the second-generation antiandrogen, enzalutamide. Combined treatment of enzalutamide and Wnt/β-catenin inhibitor showed increased growth repression in both androgen-dependent and -independent prostate cancer cells, suggesting therapeutic potential for this approach.     

Antioxidants Abrogate Alpha-Tocopherylquinone-Mediated Down-Regulation of the Androgen Receptor in Androgen-Responsive Prostate Cancer Cells

Tocopherylquinone (TQ), the oxidation product of alpha-tocopherol (AT), is a bioactive molecule with distinct properties from AT. In this study, AT and TQ are investigated for their comparative effects on growth and androgenic activity in prostate cancer cells. TQ potently inhibited the growth of androgen-responsive prostate cancer cell lines (e.g., LAPC4 and LNCaP cells), whereas the growth of androgen-independent prostate cancer cells (e.g., DU145 cells) was not affected by TQ. Due to the growth inhibitory effects induced by TQ on androgen-responsive cells, the anti-androgenic properties of TQ were examined. TQ inhibited the androgen-induced activation of an androgen-responsive reporter and inhibited the release of prostate specific antigen from LNCaP cells. TQ pretreatment was also found to inhibit AR activation as measured using the Multifunctional Androgen Receptor Screening assay. Furthermore, TQ decreased androgen-responsive gene expression, including TM4SF1, KLK2, and PSA over 5-fold, whereas AT did not affect the expression of androgen-responsive genes. Of importance, the antiandrogenic effects of TQ on prostate cancer cells were found to result from androgen receptor protein down-regulation produced by TQ that was not observed with AT treatment. Moreover, none of the androgenic endpoints assessed were affected by AT. The down-regulation of androgen receptor protein by TQ was abrogated by co-treatment with antioxidants. Overall, the biological actions of TQ were found to be distinct from AT, where TQ was found to be a potent inhibitor of cell growth and androgenic activity in androgen-responsive prostate cancer cells.     

The Role of Androgen Receptor Mutations in Prostate Cancer Progression

Prostate tumour growth is almost always dependent upon the androgen receptor pathway and hence therapies aimed at blocking this signalling axis are useful tools in the management of this disease. Unfortunately such therapies invariably fail; and the tumour progresses to an “androgen-independent” stage. In such cases androgen receptor expression is almost always maintained and much evidence exists to suggest that it may still be driving growth. One mechanism by which the receptor is thought to remain active is mutation. This review summarises the present data on androgen receptor mutations in prostate cancer, and how such substitutions offer a growth advantage by affecting cofactor interactions or by reducing ligand specificity. Such alterations appear to have a subsequent effect upon gene expression suggesting that tumours may “behave” differently dependent upon the ligand promoting growth and if a mutation is present.     

Pterostilbene-Isothiocyanate Conjugate Suppresses Growth of Prostate Cancer Cells Irrespective of Androgen Receptor Status

Chemotherapy and anti-hormonal therapies are the most common treatments for non-organ-confined prostate cancer (PCa). However, the effectiveness of these therapies is limited, thus necessitating the development of alternative approaches. The present study focused on analyzing the role of pterostilbene (PTER)-isothiocyanate (ITC) conjugate – a novel class of hybrid compound synthesized by appending an ITC moiety on PTER backbone – in regulating the functions of androgen receptor (AR), thereby causing apoptosis of PCa cells. The conjugate molecule caused 50% growth inhibition (IC₅₀) at 40±1.12 and 45±1.50 μM in AR positive (LNCaP) and negative (PC-3) cells, respectively. The reduced proliferation of PC-3 as well as LNCaP cells by conjugate correlated with accumulation of cells in G2/M phase and induction of caspase dependent apoptosis. Both PI3K/Akt and MAPK/ERK pathways played an important and differential role in conjugate-induced apoptosis of these PCa cells. While the inhibitor of Akt (A6730) or Akt-specific small interference RNA (siRNA) greatly sensitized PC-3 cells to conjugate-induced apoptosis, on the contrary, apoptosis was accelerated by inhibition of ERK (by PD98059 or ERK siRNA) in case of LNCaP cells, both ultimately culminating in the expression of cleaved caspase-3 protein. Moreover, anti-androgenic activity of the conjugate was mediated by decreased expression of AR and its co-activators (SRC-1, GRIP-1), thus interfering in their interactions with AR. All these data suggests that conjugate-induced inhibition of cell proliferation and induction of apoptosis are partly mediated by the down regulation of AR, Akt, and ERK signaling. These observations provide a rationale for devising novel therapeutic approaches for treating PCa by using conjugate alone or in combination with other therapeutics.     

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.     

雄激素受体共调节因子及其在前列腺癌进展中的作用

雄激素受体（AR）信号通路在前列腺癌的发生、进展和转移中发挥着重要作用,但AR介导组织对雄激素的特异应答是通过与其相互作用的AR共调节因子共同完成的,许多AR共调节因子的功能已被广泛研究。简要综述了目前发现的部分AR共调节因子在调节AR转录活性及前列腺癌发生、进展中的生物学作用。     

Cystatin C Is Downregulated in Prostate Cancer and Modulates Invasion of Prostate Cancer Cells via MAPK/Erk and Androgen Receptor Pathways

Cystatin C is believed to prevent tumor progression by inhibiting the activities of a family of lysosomal cysteine proteases. However, little is known about the precise mechanism of cystatin C function in prostate cancer. In the present study, we examined the expression of cystatin C and its association with matrix metalloproteinases 2 (MMP2) and androgen receptor (AR) in a tissue microarray comparing benign and malignant specimens from 448 patients who underwent radical prostatectomy for localized prostate cancer. Cystatin C expression was significantly lower in cancer specimens than in benign tissues (p<0.001) and there was a statistically significant inverse correlation between expression of cystatin C and MMP2 (r_s² = −0.056, p = 0.05). There was a clear trend that patients with decreased level of cystatin C had lower overall survival. Targeted inhibition of cystatin C using specific siRNA resulted in an increased invasiveness of PC3 cells, whereas induction of cystatin C overexpression greatly reduced invasion rate of PC3 in vitro. The effect of cystatin C on modulating the PC3 cell invasion was provoked by Erk2 inhibitor that specifically inhibited MAPK/Erk2 activity. This suggests that cystatin C may mediate tumor cell invasion by modulating the activity of MAPK/Erk cascades. Consistent with our immunohistochemical findings that patients with low expression of cystatin C and high expression of androgen receptor (AR) tend to have worse overall survival than patients with high expression of cystatin C and high AR expression, induced overexpression of AR in PC3 cells expressing cystatin C siRNA greatly enhanced the invasiveness of PC3 cells. This suggests that there may be a crosstalk between cystatin C and AR-mediated pathways. Our study uncovers a novel role for cystatin C and its associated cellular pathways in prostate cancer invasion and metastasis.     

雄激素受体信号转导途径及其在前列腺癌发展中的作用

前列腺癌是西方男性发病率最高的癌症之一,在采用雄激素阻断疗法后,大部分患者的病情可得到控制,但经过一段时间又会转变为雄激素非依赖型前列腺癌。雄激素受体(AR)在前列腺细胞中扮演重要的角色,它可调节大量基因的表达。在前列腺癌由雄激素依赖型向雄激素非依赖型的转变过程中,AR及其信号途径通过多种方式发挥作用,AR基因的扩增、AR的突变,以及与共激活子之间作用的改变都可能使细胞获得雄激素非依赖型的生长能力。此外,AR还受到多肽生长因子和细胞因子等的调节,表现激素非依赖型的转录激活活性。AR在前列腺癌中作用的阐明对前列腺癌的诊断与治疗有着重大的意义。