Guido Jenster

Vesiclepedia: A Compendium for Extracellular Vesicles with Continuous Community Annotation

Vesiclepedia is a community-annotated compendium of molecular data on extracellular vesicles.

The androgen receptor in LNCaP cells contains a mutation in the ligand binding domain which affects steroid binding characteristics and response to antiandrogens

The human prostate tumor cell line LNCaP contains an abnormal androgen receptor system with broad steroid binding specificity. Progestagens, estradiol and several antiandrogens compete with androgens for binding to the androgen receptor in the cells to a higher extent than in other androgen sensitive systems. Optimal growth of LNCaP cells is observed after addition of the synthetic androgen R1881 (0.1 nM). In addition, estrogens, progestagens and several antiandrogens do not inhibit androgen responsive growth, but have striking growth stimulatory effects and increase EGF receptor level and acid phosphatase secretion. We have found that the androgen receptor in the LNCaP cells contains a single point mutation changing the sense of codon 868 (Thr to Ala) in the ligand binding domain. Expression vectors containing the normal or mutated androgen receptor sequence were transfected into COS or HeLa cells. Androgens, progestagens, estrogens and several antiandrogens bind the mutated androgen receptor protein and activate the expression of an androgen-regulated reporter gene (GRE-tk-CAT), indicating that the mutation directly affects both binding specificity and the induction of gene expression. Interestingly, the antiandrogen casodex showed antiandrogenic properties in growth studies of LNCaP cells and did not induce reporter gene activity in Hela cells transfected with the mutant receptor. The mutated androgen receptor of LNCaP cells is therefore a useful tool in the elucidation of different levels of action of steroids and antisteroids.

TMPRSS2:ERG fusion by translocation or interstitial deletion is highly relevant in androgen-dependent prostate cancer, but is bypassed in late-stage androgen receptor-negative prostate cancer.

Recently, a unique fusion between the prostate-specific, androgen-regulated TMPRSS2 gene and the ETS genes ERG, ETV1, or ETV4 has been described in clinical prostate cancer. We investigated mechanisms of expression of four ETS genes, ERG, ETV1, ETV4, and FLI1, in 11 xenografts representing different stages of prostate cancer. All five androgen-dependent xenografts showed as major transcript overexpression of two splice variants of TMPRSS2:ERG, linking TMPRSS2 exon 1 or 2 sequences to ERG exon 4. In one of two androgen-sensitive xenografts, fusion transcripts of TMPRSS2 and ETV1 were detected. Array-based comparative genomic hybridization and interphase fluorescence in situ hybridization indicated both interstitial deletions and translocations as mechanisms of TMPRSS2:ERG gene fusion. Importantly, TMPRSS2 to ERG fusions were also observed in three of four androgen-independent, androgen receptor (AR)-negative xenografts and in two AR-negative clinical prostate cancer specimens; however, the fusion gene was not expressed. In almost all AR-negative tumor samples, overexpression of wild-type ETV4 or FLI1 was detected. Combined, our observations indicate a key role of fusion of TMPRSS2 and ETS genes in most androgen-regulated prostate cancers, which might be bypassed by androgen-independent expression of wild-type ETS factors in late-stage disease.

Diagnostic and prognostic signatures from the small non-coding RNA transcriptome in prostate cancer

Prostate cancer (PCa) is the most frequent male malignancy and the second most common cause of cancer-related death in Western countries. Current clinical and pathological methods are limited in the prediction of postoperative outcome. It is becoming increasingly evident that small non-coding RNA (ncRNA) species are associated with the development and progression of this malignancy. To assess the diversity and abundance of small ncRNAs in PCa, we analyzed the composition of the entire small transcriptome by Illumina/Solexa deep sequencing. We further analyzed the microRNA (miRNA) expression signatures of 102 fresh-frozen patient samples during PCa progression by miRNA microarrays. Both platforms were cross-validated by quantitative reverse transcriptase–PCR. Besides the altered expression of several miRNAs, our deep sequencing analyses revealed strong differential expression of small nucleolar RNAs (snoRNAs) and transfer RNAs (tRNAs). From microarray analysis, we derived a miRNA diagnostic classifier that accurately distinguishes normal from cancer samples. Furthermore, we were able to construct a PCa prognostic predictor that independently forecasts postoperative outcome. Importantly, the majority of miRNAs included in the predictor also exhibit high sequence counts and concordant differential expression in Illumina PCa samples, supported by quantitative reverse transcriptase–PCR. Our findings provide miRNA expression signatures that may serve as an accurate tool for the diagnosis and prognosis of PCa.

Evolution of the androgen receptor pathway during progression of prostate cancer

The present work focused on the potential involvement of selective adaptations of the androgen receptor pathway in the initiation and progression of prostate cancer. We defined the androgen receptor pathway by selecting 200 genes that were androgen responsive in prostate cancer cell lines and/or xenografts. This androgen receptor pathway gene signature was then used for profiling prostate cancer xenografts and patient-derived samples. Approximately half of the androgen receptor pathway genes were up-regulated in well-differentiated prostate cancer compared with normal prostate. Functionally distinct parts of the androgen receptor pathway were specifically down-regulated in high-grade cancers. Unexpectedly, metastases have down-regulated the vast majority of androgen receptor pathway genes. The significance of this progressive down-regulation of androgen receptor pathway genes was shown for a few androgen receptor-regulated genes. Lower mRNA expression of HERPUD1, STK39, DHCR24, and SOCS2 in primary prostate tumors was correlated with a higher incidence of metastases after radical prostatectomy. HERPUD1 mRNA expression predicted the occurrence of metastases almost perfectly. In vitro experiments showed that overexpression of the stress response gene HERPUD1 rapidly induces apoptosis. Based on the functions of the genes within the distinct subsets, we propose the following model. Enhanced androgen receptor activity is involved in the early stages of prostate cancer. In well-differentiated prostate cancer, the androgen receptor activates growth-promoting as well as growth-inhibiting and cell differentiation genes resulting in a low growth rate. The progression from low-grade to high-grade prostate carcinoma and metastases is mediated by a selective down-regulation of the androgen receptor target genes that inhibit proliferation, induce differentiation, or mediate apoptosis.

Exosome-mediated transmission of hepatitis C virus between human hepatoma Huh7.5 cells

Recent evidence indicates there is a role for small membrane vesicles, including exosomes, as vehicles for intercellular communication. Exosomes secreted by most cell types can mediate transfer of proteins, mRNAs, and microRNAs, but their role in the transmission of infectious agents is less established. Recent studies have shown that hepatocyte-derived exosomes containing hepatitis C virus (HCV) RNA can activate innate immune cells, but the role of exosomes in the transmission of HCV between hepatocytes remains unknown. In this study, we investigated whether exosomes transfer HCV in the presence of neutralizing antibodies. Purified exosomes isolated from HCV-infected human hepatoma Huh7.5.1 cells were shown to contain full-length viral RNA, viral protein, and particles, as determined by RT-PCR, mass spectrometry, and transmission electron microscopy. Exosomes from HCV-infected cells were capable of transmitting infection to naive human hepatoma Huh7.5.1 cells and establishing a productive infection. Even with subgenomic replicons, lacking structural viral proteins, exosome-mediated transmission of HCV RNA was observed. Treatment with patient-derived IgGs showed a variable degree of neutralization of exosome-mediated infection compared with free virus. In conclusion, this study showed that hepatic exosomes can transmit productive HCV infection in vitro and are partially resistant to antibody neutralization. This discovery sheds light on neutralizing antibodies resistant to HCV transmission by exosomes as a potential immune evasion mechanism.

Exosomes as biomarker treasure chests for prostate cancer.

CONTEXT Although progress has been made with regard to types of markers (protein, DNA, RNA, and metabolites) and implementation of improved technologies (mass spectrometry, arrays, and deep sequencing), the discovery of novel biomarkers for prostate cancer (PCa) in complex fluids, such as serum and urine, remains a challenge. Meanwhile, recent studies have reported that many cancer-derived proteins and RNAs are secreted through small vesicles known as exosomes. OBJECTIVE This narrative review describes recent progress in exosome research, focusing on the potential role of exosomes as novel biomarkers for PCa. The purpose of this review is to acquaint clinicians and researchers in the field of urology with the potential role of exosomes as biomarker treasure chests and with their clinical value. EVIDENCE ACQUISITION Medline and Embase entries between 1966 and September 2010 were searched using the keywords exosomes, microvesicles, prostasomes, biomarkers, prostate cancer, and urology. Leading publications and articles constructively contributing to exosome research were selected for this review. EVIDENCE SYNTHESIS Exosomes are small vesicles (50-100 nm) secreted by almost all tissues; they represent their tissue origin. Purification of prostate- and PCa-derived exosomes will allow us to profile exosomes, providing a promising source of protein and RNA biomarkers for PCa. This profiling will contribute to the discovery of novel markers for the early diagnosis and reliable prognosis of PCa. CONCLUSIONS Although the initial results are promising, further investigations are required to assess the clinical value of these exosomes in PCa.

Long noncoding RNA in prostate, bladder, and kidney cancer.

CONTEXT Genomic regions without protein-coding potential give rise to millions of protein-noncoding RNA transcripts (noncoding RNA) that participate in virtually all cellular processes. Research over the last 10 yr has accumulated evidence that long noncoding RNAs (lncRNAs) are often altered in human urologic cancers. OBJECTIVE To review current progress in the biology and implication of lncRNAs associated with prostate, bladder, and kidney cancer. EVIDENCE ACQUISITION The PubMed database was searched for articles in the English language with combinations of the Medical Subject Headings terms long non coding RNA, long noncoding RNA, long untranslated RNA, cancer, neoplasms, prostate, bladder, and kidney. EVIDENCE SYNTHESIS We summarise existing knowledge on the systematics, biology, and function of lncRNAs, particularly these involved in prostate, kidney, and bladder cancer. We also discuss the possible utilisation of lncRNAs as novel biomarkers and potential therapeutic targets in urologic malignancies and portray the major challenges and future perspectives of ongoing lncRNA research. CONCLUSIONS LncRNAs are important regulators of gene expression interacting with the major pathways of cell growth, proliferation, differentiation, and survival. Alterations in the function of lncRNAs promote tumour formation, progression, and metastasis of prostate, bladder, and kidney cancer. LncRNAs can be used as noninvasive tumour markers in urologic malignancies. Increased knowledge of the molecular mechanisms by which lncRNAs perform their function in the normal and malignant cell will lead to a better understanding of tumour biology and could provide novel therapeutic targets for the treatment of urologic cancers. PATIENT SUMMARY In this paper we reviewed current knowledge of long noncoding RNAs (lncRNAs) for the detection and treatment of urologic cancers. We conclude that lncRNAs can be used as novel biomarkers in prostate, kidney, or bladder cancer. LncRNAs hold promise as future therapeutic targets, but more research is needed to gain a better understanding of their biologic function.

AKT-Independent Protection of Prostate Cancer Cells from Apoptosis Mediated through Complex Formation between the Androgen Receptor and FKHR

ABSTRACT Recent studies suggested that the protection of cell apoptosis by AKT involves phosphorylation and inhibition of FKHR and related FOXO forkhead transcription factors and that androgens provide an AKT-independent cell survival signal in prostate cancer cells. Here, we report receptor-dependent repression of FKHR function by androgens in prostate cancer cells. Transcriptional analysis demonstrated that activation of the androgen receptor caused an inhibition of both wild-type FKHR and a mutant in which all three known AKT sites were mutated to alanines, showing that the repression is AKT independent. In vivo and in vitro coprecipitation studies demonstrated that the repression is mediated through protein-protein interaction between FKHR and the androgen receptor. Mapping analysis localized the interacting domains to the carboxyl terminus between amino acids 350 and 655 of FKHR and to the amino-terminal A/B region and the ligand binding domain of the receptor. Further analysis demonstrated that the activated androgen receptor blocked FKHRs DNA binding activity and impaired its ability to induce Fas ligand expression and prostate cancer cell apoptosis and cell cycle arrest. These studies identify a new mechanism for androgen-mediated prostate cancer cell survival that appears to be independent of the activity of the receptor on androgen response element-mediated transcription and establish FKHR and related FOXO forkhead proteins as important nuclear targets for both AKT-dependent and -independent survival signals in prostate cancer cells.

Evidence of Limited Contributions for Intratumoral Steroidogenesis in Prostate Cancer

Androgen-deprivation therapy for prostate cancer (PC) eventually leads to castration-resistant PC (CRPC). Intratumoral androgen production might contribute to tumor progression despite suppressed serum androgen concentrations. In the present study, we investigated whether PC or CRPC tissue may be capable of intratumoral androgen synthesis. Steroidogenic enzyme mRNAs were quantified in hormonally manipulated human PC cell lines and xenografts as well as in human samples of normal prostate, locally confined and advanced PC, local nonmetastatic CRPC, and lymph node metastases. Overall, the majority of samples showed low or absent mRNA expression of steroidogenic enzymes required for de novo steroid synthesis. Simultaneous but low expression of the enzymes CYP17A1 and HSD3B1, essential for the synthesis of androgens from pregnenolone, could be detected in 19 of 88 patient samples. Of 19 CRPC tissues examined, only 5 samples expressed both enzymes. Enzymes that convert androstenedione to testosterone (AKR1C3) and testosterone to dihydrotestosterone (DHT; SRD5A1) were abundantly expressed. AKR1C3 expression was negatively regulated by androgens in the experimental models and was increased in CRPC samples. Expression of SRD5A1 was upregulated in locally advanced cancer, CRPC, and lymph node metastases. We concluded that intratumoral steroid biosynthesis contributes less than circulating adrenal androgens, implying that blocking androgen production and its intraprostatic conversion into DHT, such as via CYP17A1 inhibition, may represent favorable therapeutic options in patients with CRPC.