GREB1 is a novel androgen-regulated gene required for prostate cancer growth

BACKGROUND: Gene regulated in breast cancer 1 (GREB1) is a novel estrogen-regulated gene shown to play a pivotal role in hormone-stimulated breast cancer growth. GREB1 is expressed in the prostate and its putative promoter contains potential androgen receptor (AR) response elements. METHODS: We investigated the effects of androgens on GREB1 expression and its role in androgen-dependent prostate cancer growth. RESULTS: Real-time PCR demonstrated high level GREB1 expression in benign prostatic hypertrophy (BPH), localized prostate cancer (L-PCa), and hormone refractory prostate cancer (HR-PCa). Androgen treatment of AR-positive prostate cancer cells induced dose-dependent GREB1 expression, which was blocked by anti-androgens. AR binding to the GREB1 promoter was confirmed by chromatin immunoprecipitation (ChIP) assays. Suppression of GREB1 by RNA interference blocked androgen-stimulated LNCaP cell proliferation. CONCLUSIONS: GREB1 is expressed in proliferating prostatic tissue and prostate cancer, is regulated by androgens, and suppression of GREB1 blocks androgen-induced growth suggesting GREB1 may be critically involved in prostate cancer proliferation.     

Endothelin-1 production by prostate cancer cell lines is up-regulated by factors involved in cancer progression and down-regulated by androgens.

BACKGROUND: Recent data demonstrate that endothelin-1 (ET-1) concentration increases in plasma of men with advanced, hormone-refractory prostate adenocarcinoma. In addition, ET-1 is involved in osteblastic remodelling and new bone formation, suggesting a role for this vasoactive peptide in the metastatic progression of prostate cancer to the bone. METHODS: We investigated the regulation of ET-1 expression in androgen-sensitive and insensitive prostate cancer cell lines by androgens and several factors involved in progression of prostate cancer (EGF) and bone remodelling (TGFbeta-1, IL1-alpha and IGF-1). RESULTS: Northern analysis and radio immunoassay demonstrated that all the ET-1 pathways are tuned off in the androgen-sensitive LNCaP cell line when compared to the androgen-insensitive PC-3 and DU145. In PC-3 cells transfected with a full-length androgen receptor expression vector (PC-3-AR), treatment with androgens reduced gene expression and secretion of ET-1 without affecting the gene expression of ET-3. Collectively, these data support a role for androgens in the regulation of ET-1 production by prostate adenocarcinoma cells. In PC-3 and DU145 cells, ET-1 gene expression and secretion were up-regulated by TGFbeta-1, EGF and IL1-alpha, whereas IGF-1 was ineffective. Conversely, none of the treatments affected ECE-1 or ET-3 gene expression. CONCLUSIONS: In conclusion, ET-1 production by prostate adenocarcinoma cells is down-regulated by androgens and up-regulated by factors involved in tumour progression indicating a role for this peptide in the biology of prostate cancer. In view of the role exerted by ET-1 in the process of bone metastasis, our data suggest the use of ET-1 receptor antagonists in the treatment of advanced prostate cancer.     

Small ubiquitin-like modifier protein-specific protease 1 and prostate cancer

Small ubiquitin-like modifier protein （SUMO） modification is a highly dynamic process, catalyzed by SUMO- specific activating （El）, conjugating （E2） and ligating （E3） enzymes, and reversed by a family of SUMO-specific proteases （SENPs）. There are six members of the human SENP family, and each SENP has different cellular locations and substrate specificities. However, the precise roles of SENPs in cellular processes have not been elucidated to date. This brief review will focus on recent advances pertaining to the identified targets of SENP 1 and its potential role in prostate cancer.     

BM18: A novel androgen-dependent human prostate cancer xenograft model derived from a bone metastasis

BACKGROUND: Androgen-dependent prostate cancer (PrCa) xenograft models are required to study PrCa biology in the clinically relevant in vivo environment. METHODS: Human PrCa tissue from a femoral bone metastasis biopsy (BM18) was grown and passaged subcutaneously through male severe combined immune-deficient (SCID) mice. Human mitochondria (hMt), prostate specific antigen (PSA), androgen receptor (AR), cytokeratin-18 (CK-18), pan-cytokeratin, and high molecular weight-cytokeratin (HMW-CK) were assessed using immunohistochemistry (IHC). Surgical castration was performed to examine androgen dependence. Serum was collected pre- and post-castration for monitoring of PSA levels. RESULTS: BM18 stained positively for hMt, PSA, AR, CK-18, pan keratin, and negatively for HMW-CK, consistent with the staining observed in the original patient material. Androgen-deprivation induced tumor regression in 10/10 castrated male SCID mice. Serum PSA levels positively correlated with BM18 tumor size. CONCLUSIONS: BM18 expresses PSA and AR, and rapidly regresses in response to androgen withdrawal. This provides a new clinically significant PrCa model for the study of androgen-dependent growth.     

Germline CAG repeat length of the androgen receptor and time to progression in patients with prostate cancer treated with androgen deprivation therapy

Study Type – Prognosis (retrospective cohort) Level of Evidence 2b What’s known on the subject? and What does the study add? Germline CAG repeat polymorphisms in the androgen receptor (AR‐CAG) have been shown to influence the activity of the androgen receptor, but there has been conflicting data from small retrospective studies evaluating the effect of CAG repeat polymorphisms on response to ADT. This is the largest published study to date investigating the association of germline AR‐CAG repeat lengths and efficacy of ADT in prostate cancer. Germline AR‐CAG repeat lengths do not predict response to ADT.

OBJECTIVES

? Germline CAG repeat polymorphisms in the androgen receptor (AR‐CAG) have been shown to influence the activity of the AR. ? The purpose of the present study was to determine if AR‐CAG repeat length correlates with time to progression on androgen deprivation therapy (ADT).

PATIENTS AND METHODS

? Germline AR‐CAG repeat lengths were determined in a cohort of 480 patients with recurrent or metastatic prostate cancer treated at a single tertiary care institution and correlated to time to progression (TTP) and overall survival.

RESULTS

? There was no significant correlation between differences in the AR‐CAG repeat lengths and TTP or overall survival in patients with prostate cancer receiving ADT. ? AR‐CAG repeat lengths did not significantly correlate with age, prostate‐specific antigen (PSA), Gleason score or clinical stage at diagnosis. ? In patients with metastatic disease, longer AR‐CAG repeat lengths (>23 vs ≤23) were associated with a longer TTP on ADT, but this finding was of borderline significance (median TTP 18.3 vs 15.5 months, P= 0.09; adjusted HR = 0.76, 95% confidence interval = 0.54–1.09).

CONCLUSIONS

? This is the largest published study to date investigating the association of germline AR‐CAG repeat lengths and efficacy of ADT in prostate cancer. ? Germline AR‐CAG repeat lengths do not predict response to ADT.     

Serum human glandular kallikrein 2 (hK2) for distinguishing stage and grade of prostate cancer

BACKGROUND: Human glandular kallikrein (hK2) has been shown to add important information regarding the early detection and staging of prostate cancer. Preliminary analysis pointed out that hK2 may discriminate between pT2 and pT3 tumors, and that hK2 may predict Gleason grade 4/5 cancer volume, better than prostate-specific antigen (PSA) or percent free PSA (%fPSA). We investigated the role of hK2 serum values for predicting pathological stage, grade and Gleason score. METHODS: Prostate-specific antigen, free PSA and hK2 were measured on 222 untreated prostate cancer patients who had received radical prostatectomy at the Charité Hospital, Berlin, Germany. Pathological work up revealed pT2-cancer in 111 patients and pT3-cancer in 111 patients. Grade 2 was found in 118 patients whereas grade 3 tumors were found in 104 patients. RESULTS: For pT2 and pT3 patients, the %fPSA (P=0.006), the ratios hK2/fPSA (P=0.08) and hK2xtPSA/fPSA (P=0.002) were all significant different whereas hK2 (P=0.143) and PSA (P=0.1) did not differ. Between grade 2 and grade 3 tumors, the hK2 alone (P=0.27), the %fPSA (P=0.13), the ratios hK2/fPSA (P=0.94) and hK2xtPSA/fPSA (P=0.12) did not separate, whereas PSA (P=0.039) showed a difference. The same relationships were found between the two groups in Gleason score<7 and >or=7. Neither the hK2 ratio, nor % fPSA was different. CONCLUSION: Human glandular kallikrein was not different between pT2 and pT3, nor between G2 versus G3 or Gleason scores<7 and >or=7 prostate cancer. Together with %fPSA, hK2 may only help to distinguish preoperatively between pT2 and pT3 prostate cancer but cannot add further information.     

Involvement of arginine methyltransferase CARM1 in androgen receptor function and prostate cancer cell viability

BACKGROUND: Androgen receptor (AR) may play a role in prostate cancer progression. Coactivator-associated arginine methyltransferase (CARM1) catalyzes methylation of histone H3 at Arg-17. METHODS: Immunohistochemistry of CARM1 was performed on primary prostate cancer specimens. CARM1 recruitment and histone methylation was analyzed by chromatin immunoprecipitation. The effect of CARM1 overexpression or CARM1 knockdown was assessed on reporter assays, cell proliferation, apoptosis, and endogenous androgen target gene expression. RESULTS: CARM1 expression was increased in the nucleus of castration-resistant, but not androgen-stimulated prostate cancer. Androgen stimulation led to CARM1 recruitment and methylation of histone H3 at androgen responsive enhancers. Overexpression of CARM1 stimulated and CARM1 knockdown inhibited AR reporter activity. CARM1 knockdown inhibited cell proliferation and induced apoptosis. CARM1 knockdown inhibited androgen-dependent prostate specific antigen (PSA) and hK2 mRNA expression. CONCLUSIONS: CARM1 is essential for AR function and may play a role in prostate cancer progression. CARM1 may represent a novel therapeutic target in prostate cancer.     

ADAMTS1, a putative anti‐angiogenic factor,is decreased in human prostate cancer

OBJECTIVE

To investigate the expression of ‘ADAM metallopeptidase with thrombospondin type I motif, 1’ (ADAMTS1) in human prostate cancer, and to study its relationship to microvessel density (MVD) and metastasis. ADAMTS1 has been described as an anti‐angiogenic and antitumour factor, but its function in prostate cancer is unknown.

PATIENTS AND METHODS

ADAMTS1 expression was evaluated by immunohistochemistry in specimens obtained by transurethral resection of the prostate from patients with hormone‐naïve and hormone‐refractory prostate tumours, including adjacent benign tissue. A semiquantitative scoring system was used for evaluating the staining. MVD was quantified by counting the number of CD34‐positive blood vessels.

RESULTS

ADAMTS1 was strongly expressed in the luminal epithelial cells in benign prostate glands, whereas expression was significantly lower in prostate cancer cells. There was no obvious difference between hormone‐naïve and hormone‐refractory tumours, and ADAMTS1 expression did not correlate with Gleason score. However, in hormone‐refractory tumours from patients with metastatic disease, the expression of ADAMTS1 was significantly lower than in tumours from patients without metastases. Furthermore, the MVD was higher in hormone‐refractory than in hormone‐naïve tumours and benign tissue, and MVD correlated with Gleason score. There was no association between ADAMTS1 and MVD in the hormone‐naïve tumours, while hormone‐refractory tumours with low ADAMTS1 expression had a higher MVD than those with moderate/high expression.

CONCLUSION

ADAMTS1 expression is decreased in prostate cancer, and might be involved in the early steps of prostate cancer development. Further, ADAMTS1 might have an anti‐angiogenic and antimetastatic role in hormone‐refractory prostate cancer, where low ADAMTS1 expression is associated with a high MVD and metastasis.     

KLK31P is a novel androgen regulated and transcribed pseudogene of kallikreins that is expressed at lower levels in prostate cancer cells than in normal prostate cells

BACKGROUND: Fifteen human tissue kallikrein (KLK) genes have been identified as a cluster on chromosome 19. KLK expression is associated with various human diseases including cancers. Noncoding RNAs such as PCA3/DD3 and PCGEM1 have been identified in prostate cancer cells. METHODS: Using massively parallel signature sequencing (MPSS) technology, RT-PCR, and 5' rapid amplification of cDNA ends (RACE), we identified and cloned a novel gene that maps to the KLK locus. RESULTS: We have characterized this gene, named as KLK31P by the HUGO Gene Nomenclature Committee, as an unprocessed KLK pseudogene. It contains five exons, two of which are KLK-derived while the rest are "exonized" interspersed repeats. KLK31P is expressed abundantly in prostate tissues and is androgen regulated. KLK31P is expressed at lower levels in localized and metastatic prostate cancer cells than in normal prostate cells. CONCLUSIONS: KLK31P is a novel androgen regulated and transcribed pseudogene of kallikreins that may play a role in prostate carcinogenesis or maintenance.     

不同前列腺组织中雄激素受体的表达研究

目的:研究雄激素受体(AR)在正常前列腺、良性前列腺增生(BPH)和前列腺癌(PCa)组织中的表达,探讨AR与BPH和PCa的关系。方法:采用实时定量PCR、免疫荧光和组织蛋白电泳方法,分析15例正常前列腺、20例BPH与40例PCa标本中AR的表达情况。结果:实时定量PCR和组织蛋白电泳检测BPH组织与正常前列腺组织中AR的表达量差异无统计学意义(P>0.05)。但免疫荧光检测发现BPH组织中AR蛋白表达量增高。3种方法检测PCa组织中AR表达量较正常前列腺组织和BPH组织增高(P<0.05)。高分化PCa的AR表达比低分化PCa高(P<0.05)。随着临床分期的增高,AR的表达降低(P<0.05),激素非依赖性前列腺癌(HRPC)组织中AR表达最低。结论:AR在PCa组织中的表达较正常前列腺和BPH组织中增高,AR的表达与PCa的分级、分期相关。     

Increased phospho-AKT is associated with loss of the androgen receptor during the progression of N-methyl-N-nitrosourea-induced prostate carcinogenesis in rats

BACKGROUND: Characterization of molecular events during N-methyl-N-nitrosourea (MNU)-induced rat prostate carcinogenesis enhances the utility of this model for the preclinical assessment of preventive strategies. Androgen independence is typical of advanced human prostate cancer and may occur through multiple mechanisms including the loss of androgen receptor (AR) expression and the activation of alternative signaling pathways. METHODS: We examined the interrelationships between AR and p-AKT expression by immunohistochemical staining during MNU-androgen-induced prostate carcinogenesis in male Wistar-Unilever rats. Histone nuclear staining and image analysis was employed to assess parallel changes in chromatin and nuclear structure. RESULTS: The percentage of AR positive nuclei decreased (P < 0.01) as carcinogenesis progressed: hyperplasia (92%), atypical hyperplasia (92%), well-differentiated adenocarcinoma (57%), moderately-differentiated adenocarcinoma (19%), and poorly-differentiated adenocarcinoma (10%). Conversely, p-AKT staining increased significantly during carcinogenesis. Sparse staining was observed in normal tissues (0.2% of epithelial area) and hyperplastic lesions (0.1%), while expression increased significantly (P < 0.001) in atypical hyperplasia (7.6%), well-differentiated adenocarcinoma (16.7%), moderately-differentiated adenocarcinoma (19.6%), and poorly-differentiated adenocarcinoma (17.4%). In parallel, nuclear morphometry revealed increased nuclear size, greater irregularity, and lower DNA compactness as cancers became more poorly differentiated. CONCLUSIONS: In the MNU model, the progressive evolution of dominant tumor cell populations showing an increase in p-AKT in parallel with a decline in AR staining suggests that activation of AKT signaling may be one of several mechanisms contributing to androgen insensitivity during prostate cancer progression. Our observations mimic findings suggested by human studies and support the relevance of the MNU model in preclinical studies of preventive strategies.     

Raf-1 expression may influence progression to androgen insensitive prostate cancer

BACKGROUND: Recent evidence has implicated the MAP kinase pathway with the development of androgen insensitive prostate cancer (AIPC). We have previously reported gene amplification of critical members of this pathway with the development of androgen insensitive disease. METHODS: Protein expression of Raf-1 was analyzed using immunohistochemistry (IHC) in a database of 65 paired tumor specimens obtained before and after the development of AIPC and correlated with other members of the pathway. RESULTS: Patients whose Raf-1 expression rose with development of AIPC had a significantly shorter median time to biochemical relapse compared to those whose expression fell or remained unchanged (1.16 vs. 2.62 years, P = 0.0005). In AIPC tumors, expression of Raf-1 correlated significantly with expression of HER2 and with expression of c-fos. CONCLUSIONS: We conclude that the HER2/Raf-1/AP-1 axis may promote the development of AIPC, leading to early relapse. Members of the pathway may act as novel therapeutic targets for patients.     

A polymorphism in a transporter of testosterone is a determinant of androgen independence in prostate cancer

OBJECTIVE

To determine if patients with advanced prostate cancer carrying a polymorphism that codes for a more active testosterone transporter have less durable responses to androgen‐deprivation therapy (ADT) than patients not carrying this polymorphism.

PATIENTS AND METHODS

We previously determined that a polymorphism in SLCO1B3 affects testosterone transport and that those men who have at least one wild‐type T allele at the 334 T > G polymorphism in this gene have a shorter survival. We hypothesized that the T allele which increases testosterone transport would be associated with a shorter interval from ADT to androgen independence. We examined the association between this SLCO1B3 polymorphism and time from ADT to androgen independence, ADT to prostate‐specific antigen (PSA) nadir and PSA nadir to androgen independence in 68 Caucasian patients with advanced prostate cancer who were treated with ADT with metastatic disease (D2) or biochemical failure with no metastatic disease (D0).

RESULTS

When examined separately, patients in the individual stages tended to have a shorter time to androgen independence with the T allele in the D0 (P = 0.11) and D2 (P = 0.18) groups. Combining these groups and stratifying by stage yielded a statistically significant shorter time to androgen independence with the T allele (P = 0.048).

CONCLUSION

A polymorphism in a transporter that increases testosterone import is associated with a shorter time to androgen independence in patients with prostate cancer who are treated with ADT.