Abstract 3060: Target genes of chromosomal 9p13.3 amplification in prostate cancer

The development and progression of cancer is caused by alterations that accumulate in the genome of malignant cells. We are studying genetic alterations occurring in prostate cancer, the most common male malignancy in Western countries. We have previously identified a frequent (39%) gain at 9p13-q21 in 13 prostate cancer xenografts and 5 cell lines by aCGH (Saramäki et al., Int J Cancer 119:1322-1329, 2006). Preliminary results indicate that in clinical prostatectomy samples, gains and amplifications are found in approximately 30% and 10% of the cases, respectively, and that the amplification frequency seems to increase with disease progression to hormone-refractory stage. The 9p13.3 amplification is also found from several breast cancer cell lines, raising the possibility that the amplification target gene(s) in this area may take part in breast cancer formation in addition to prostate cancer.

We aim at identifying the target gene of the 9p13.3 amplification in prostate cancer. A minimal region for the 9p13.3 amplification, determined by fluorescence in situ hybridisation (FISH), spans nearly 3.5 Mb and contains more than 40 known and hypothetical protein-coding genes. We initially screened mRNA expression levels by quantitative RT-PCR and chromosomal copy number alterations by FISH for these genes in 7 prostate cancer cell lines and 19 prostate cancer xenografts. Thus, we narrowed down the list of amplification target candidates to eight protein-coding genes (C9orf25, GALT, PIGO, UBAP1, UBAP2, UBE2R2, UNC13B and VCP). We have performed siRNA-mediated downregulation of these genes in cell lines with either a normal copy number status or a gain/amplification in 9p13.3 (prostate cancer cell lines PC-3 and 22Rv1; breast cancer cell lines MCF-7 and BT-474). Downregulation of several of these genes decrease the proliferation rate of the cells significantly (GALT, PIGO, UBAP1, UBAP2, VCP). As decreased levels of VCP induce cell death in PC-3 cells, downregulation of UBAP1 induces a cell cycle arrest in the G2/M phase. In addition, invasion of PC-3 cells in Boyden chamber assay is affected by knock-down of GALT and PIGO. Genes exhibiting alterations in the siRNA assays have been further analyzed for their expression in clinical prostate cancer tumor material by qRT-PCR and immunohistochemistry. These genes are also studied by overexpressing their cDNAs in cell lines with normal 9p13.3 copy number status and screening for altered cellular growth, survival and invasion in vitro. We aim at identifying a novel diagnostic and/or prognostic marker for prostate cancer, and potentially also a target for new cancer therapies, from the 9p13.3 region.

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 3060. doi:10.1158/1538-7445.AM2011-3060

The miR-15a-miR-16-1 locus is homozygously deleted in a subset of prostate cancers

MicroRNAs (miRNAs) are small, non-coding RNAs that negatively regulate the expression of protein coding genes. In this study, we screened highly informative prostate cancer cell lines and xenografts (n = 42) for miRNA gene copy number and expression changes. The expression profiling showed distinction between cell lines and xenografts as well as between androgen sensitive and independent models. Only a few copy number alterations that were associated with expression changes were identified. Most importantly, the miR-15a-miR-16-1 locus was found to be homozygously deleted in two samples leading to the abolishment of miR-15a, but not miR-16, expression. miR-16 is also expressed from another genomic locus. Mutation screening of the miR-15a-miR-16-1 gene in the model systems as well as clinical samples (n = 50) revealed no additional mutations. In conclusion, our data indicate that putative tumor suppressors, miR-15a and miR-16-1, are homozygously deleted in a subset of prostate cancers, further suggesting that these miRNAs could be important in the development of prostate cancer.

ETS1 mediates MEK1/2-dependent overexpression of cancerous inhibitor of protein phosphatase 2A (CIP2A) in human cancer cells

EGFR-MEK-ERK signaling pathway has an established role in promoting malignant growth and disease progression in human cancers. Therefore identification of transcriptional targets mediating the oncogenic effects of the EGFR-MEK-ERK pathway would be highly relevant. Cancerous inhibitor of protein phosphatase 2A (CIP2A) is a recently characterized human oncoprotein. CIP2A promotes malignant cell growth and is over expressed at high frequency (40–80%) in most of the human cancer types. However, the mechanisms inducing its expression in cancer still remain largely unexplored. Here we present systematic analysis of contribution of potential gene regulatory mechanisms for high CIP2A expression in cancer. Our data shows that evolutionary conserved CpG islands at the proximal CIP2A promoter are not methylated both in normal and cancer cells. Furthermore, sequencing of the active CIP2A promoter region from altogether seven normal and malignant cell types did not reveal any sequence alterations that would increase CIP2A expression specifically in cancer cells. However, treatment of cancer cells with various signaling pathway inhibitors revealed that CIP2A mRNA expression was sensitive to inhibition of EGFR activity as well as inhibition or activation of MEK-ERK pathway. Moreover, MEK1/2-specific siRNAs decreased CIP2A protein expression. Series of CIP2A promoter-luciferase constructs were created to identify proximal −27 to −107 promoter region responsible for MEK-dependent stimulation of CIP2A expression. Additional mutagenesis and chromatin immunoprecipitation experiments revealed ETS1 as the transcription factor mediating stimulation of CIP2A expression through EGFR-MEK pathway. Thus, ETS1 is probably mediating high CIP2A expression in human cancers with increased EGFR-MEK1/2-ERK pathway activity. These results also suggest that in addition to its established role in invasion and angiogenesis, ETS1 may support malignant cellular growth via regulation of CIP2A expression and protein phosphatase 2A inhibition.

Activating mutation (V617F) in the tyrosine kinase JAK2 is absent in locally-confined or castration-resistant prostate cancer

Background: Transcription factor Stat5a/b is highly critical for the viability of human prostate cancer cells in vitro and for prostate tumor growth in vivo. Stat5 is constitutively active in clinical prostate cancers but not in the normal human prostate epithelium. Moreover, Stat5a/b activation in prostate cancer is associated with high histological grade of prostate cancer. However, the molecular mechanisms underlying constitutive activation of Stat5a/b in prostate cancer are unclear. The receptor-associated tyrosine kinase Jak2 is a known key activator of Stat5a/b in prostate cancer cells in response to ligand stimulation. Recently, a single gain-of-function point mutation of JAK2 was described in myeloproliferative diseases leading to constitutive Jak2 kinase activity, subsequent Stat5a/b activation and involvement of V617F Jak2 in the pathogenesis of myeloproliferative disorders.

Materials and Methods: We determined whether JAK2 undergoes the V617F activating mutation during clinical progression of human prostate cancer using a highly sensitive assay (amplification refractory mutation system) and a unique material of fresh specimens from organ-confined or castration-resistant prostate cancers.

Results: The JAK2 V617F mutation was not found in any of the normal or malignant prostate samples analyzed in this study.

Conclusions: Future work should focus on determining the molecular mechanisms other than V617F mutation of Jak2 resulting in continuous Stat5 activation in clinical prostate cancers.

MicroRNA in prostate, bladder, and kidney cancer: a systematic review

CONTEXT

MicroRNAs (miRNA) are noncoding RNAs that post-transcriptionally regulate gene expression. Their altered expression and function have been observed in most urologic cancers. MiRNAs represent potential disease biomarkers and novel therapeutic targets.

OBJECTIVE

To review and evaluate the evidence implicating miRNAs in the pathogenesis of prostate cancer (PCa), bladder cancer (BCa), and renal cancer.

EVIDENCE ACQUISITION

A systematic review was performed using PubMed and Embase to search for reports using strings for microRNA, non-coding RNA, cancer, prostate, bladder, and renal cancer. Identified manuscripts were retrieved and references searched. Selected studies were required to concentrate on the role of miRNA in these urologic cancers.

EVIDENCE SYNTHESIS

We reviewed articles that focus on this topic. More than 40 miRNAs have been implicated in urologic cancer and many target common carcinogenic pathways. In particular, apoptosis avoidance, cell proliferation, epithelial-to-mesenchymal transition, angiogenic signalling, and the generation of androgen independence are targeted or facilitated by more than one miRNA. Little work has been done to evaluate the translational applications for this knowledge to date. Novel therapeutic strategies have been developed and are under investigation to selectively modulate miRNAs; such work would potentially enable personalised tumour therapy.

CONCLUSIONS

MiRNAs appear to be important modulators of urologic cancer. Their expression is frequently altered in these tumours, and many are functionally implicated in their pathogenesis. They require evaluation to determine the translational role and therapeutic potential for this knowledge.

[Are there enough medical scientists in Finland?]

Discussion within the scientific society and hospital communities has raised concerns of the current status and future of clinical research in Finland. One of the crucial future challenges is whether there are enough medical scientists that are able to perform clinical research and comprehend and manage medicine as a whole. In the article, the authors present suggestions for solving the problematic issues.

Allelic variation at the 8q23.3 colorectal cancer risk locus functions as a cis-acting regulator of EIF3H

Common genetic variation at human 8q23.3 is significantly associated with colorectal cancer (CRC) risk. To elucidate the basis of this association we compared the frequency of common variants at 8q23.3 in 1,964 CRC cases and 2,081 healthy controls. Reporter gene studies showed that the single nucleotide polymorphism rs16888589 acts as an allele-specific transcriptional repressor. Chromosome conformation capture (3C) analysis demonstrated that the genomic region harboring rs16888589 interacts with the promoter of gene for eukaryotic translation initiation factor 3, subunit H (EIF3H). We show that increased expression of EIF3H gene increases CRC growth and invasiveness thereby providing a biological mechanism for the 8q23.3 association. These data provide evidence for a functional basis for the non-coding risk variant rs16888589 at 8q23.3 and provides novel insight into the etiological basis of CRC.

Common inherited variation on human chromosome 8q23 influences the risk of developing colorectal cancer (CRC). To understand the basis of this association we have compared the frequency of common genetic variants at 8q23 in ∼2,000 CRC cases and ∼2,000 healthy controls. Functional analyses of variants strongly associated with CRC risk showed that the single nucleotide polymorphism rs16888589 underscores the 8q23.3 association. The region of the genome harboring rs16888589 increases the expression of the gene for eukaryotic translation initiation factor 3, subunit H. We show that increased expression of this gene increases CRC growth thereby providing a biological mechanism for the 8q23.3 association. This finding is of particular importance in elucidating the etiological basis of CRC.

miR-193b is an epigenetically regulated putative tumor suppressor in prostate cancer

miRNAs have proven to be key regulators of gene expression and are differentially expressed in various diseases, including cancer. Our aim was to identify epigenetically dysregulated genes in prostate cancer. We performed miRNA expression profiling after relieving epigenetic modifications in 6 prostate cancer cell lines and nonmalignant prostate epithelial cells. Thirty-eight miRNAs showed increased expression in any prostate cancer cell line after 5-aza-2'-deoxycytidine (5azadC) and trichostatin A (TSA) treatments. Six of these also had decreased expression in clinical prostate cancer samples compared to benign prostatic hyperplasia. Among these, miR-193b was methylated in 22Rv1 cell line at a CpG island approximately 1 kb upstream of the miRNA locus. Expressing miR-193b in 22Rv1 cells using pre-miR-193b oligonucleotides caused a significant growth reduction (p < 0.001) resulting from a decrease of cells in S-phase of the cell cycle (p < 0.01). In addition, the anchorage independent growth was partially inhibited in transiently miR-193b-expressing 22Rv1 cells (p < 0.01). Altogether, our data suggest that miR-193b is an epigenetically silenced putative tumor suppressor in prostate cancer.

Probabilistic analysis of gene expression measurements from heterogeneous tissues

Motivation: Tissue heterogeneity, arising from multiple cell types, is a major confounding factor in experiments that focus on studying cell types, e.g. their expression profiles, in isolation. Although sample heterogeneity can be addressed by manual microdissection, prior to conducting experiments, computational treatment on heterogeneous measurements have become a reliable alternative to perform this microdissection in silico. Favoring computation over manual purification has its advantages, such as time consumption, measuring responses of multiple cell types simultaneously, keeping samples intact of external perturbations and unaltered yield of molecular content.

Results: We formalize a probabilistic model, DSection, and show with simulations as well as with real microarray data that DSection attains increased modeling accuracy in terms of (i) estimating cell-type proportions of heterogeneous tissue samples, (ii) estimating replication variance and (iii) identifying differential expression across cell types under various experimental conditions. As our reference we use the corresponding linear regression model, which mirrors the performance of the majority of current non-probabilistic modeling approaches.

Availability and Software: All codes are written in Matlab, and are freely available upon request as well as at the project web page http://www.cs.tut.fi/∼erkkila2/. Furthermore, a web-application for DSection exists at http://informatics.systemsbiology.net/DSection.

Contact:timo.p.erkkila@tut.fi; harri.lahdesmaki@tut.fi

Genetic alterations and changes in expression of histone demethylases in prostate cancer

BACKGROUND

Histone demethylases LSD1, JHDM2A, and GASC1 have been suggested to function as androgen receptor co-activators, and to be involved in prostate cancer (PC) progression. We aim to identify genetic alterations and changes in expression of these genes in PC.

METHODS

PC cell lines, xenografts as well as clinical specimens were screened for mutations using denaturating high-performance liquid chromatography and sequencing, and for expression alterations by using quantitative RT-PCR and immunohistochemistry.

RESULTS

Only known single nucleotide polymorphisms, but no mutations, were found in these genes. JHDMA2 mRNA expression was slightly increased (P < 0.05) in PC compared with benign prostate hyperplasia (BPH), whereas the expression of GASC1 was slightly higher (P < 0.05) in castration-resistant PC (CRPC) compared with untreated PC or BPH. The mRNA expression of LSD1 was not altered in PC. The expression of LSD1 protein was somewhat, although not statistically significantly (P = 0.0521) lower in CRPC compared with untreated PC. In prostatectomy specimens, the level of LSD1 protein expression was associated with low pT-stage (P = 0.0402), but not with Gleason score or progression-free survival.

CONCLUSIONS

As no genetic alterations and only very modest expression changes were found, it is unlikely that LSD1, JHDM2A, or GASC1 play a major role in the progression of PC.

Association of SPINK1 expression and TMPRSS2:ERG fusion with prognosis in endocrine-treated prostate cancer

PURPOSE

The aim of the study was to examine whether TMPRSS2:ERG fusion or SPINK1 protein expression is associated with hormone responsiveness of prostate cancer and can thus be used as a biomarker.

EXPERIMENTAL DESIGN

Diagnostic needle biopsies from prostate cancer patients primarily treated by endocrine therapy were evaluated for TMPRSS2:ERG fusion with fluorescence in situ hybridization and SPINK1 protein expression with immunohistochemistry.

RESULTS

The frequency of TMPRSS2:ERG fusion in 178 biopsies of hormonally treated patients was 34%. Of the fusion-positive cases, 71% showed deletion between the two genes, and 23% showed gain of the fusion. The fusion was associated with high Ki-67 staining (P=0.001), age at diagnosis (P=0.024), and tumor area (P=0.006), but not with Gleason score, T stage, M stage, prostate-specific antigen (PSA), or progression-free survival. Strong positive SPINK1 expression was found in 11% (21 of 186) of the biopsies. SPINK1-positive cases had significantly shorter progression-free survival compared with SPINK1-negative cases (P=0.001). The expression was not associated with any other clinicopathologic variables studied. In a multivariate analysis, SPINK1 expression showed independent prognostic value, with a relative risk of 2.3 (95% confidence interval, 1.1-4.6). SPINK1 expression and the fusion were not associated with each other.

CONCLUSIONS

There was no association between TMPRSS2:ERG fusion and prognosis, suggesting that TMPRSS2:ERG rearrangement does not implicate hormone dependence of the cancer. SPINK1 expression, found in approximately 10% of prostate cancers, was associated with aggressive form of the disease and could serve as a biomarker in endocrine-treated prostate cancer.

Abstract 4093: miR-193b is an epigenetically regulated putative tumor suppressor in prostate cancer

miRNAs have proven to be key regulators of gene expression and are differentially expressed in various diseases, including cancer. Our aim was to identify epigenetically dysregulated genes in prostate cancer. We performed miRNA expression profiling after relieving epigenetic modifications in six prostate cancer cell lines and non-malignant prostate epithelial cells. 38 miRNAs showed increased expression in any prostate cancer cell line after 5-aza-2′-deoxycytidine (5azadC) and trichostatin A (TSA) treatments. Six of these also had decreased expression in clinical prostate cancer samples compared to benign prostatic hyperplasia. Among these, miR-193b was methylated in 22Rv1 cell line at a CpG island ∼1kb upstream of the miRNA locus. Expressing miR-193b in 22Rv1 cells using pre-miR-193b oligonucleotides caused a significant growth reduction (p&lt;0.001) resulting from a decrease of cells in S-phase of the cell cycle (p&lt;0.01). In addition, the anchorage independent growth was partially inhibited in transiently miR-193b -expressing 22Rv1 cells (p&lt;0.01). Altogether, our data suggest that miR-193b is an epigenetically silenced putative tumor suppressor in prostate cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4093.

Abstract 2942: The effect of AR expression level on the chromatin binding of the receptor

Treatment of castration resistant prostate cancer remains to be a challenge. Androgen receptor (AR) is overexpressed and still active at this stage of the disease. Our goal is to identify AR downstream genes and to study the effect of AR overexpression on the chromatin binding.

We established, by stable transfection of wtAR into LNCaP cell, two cell lines that over express moderate (LNCaP-ARmo: 2-3 fold) and high (LNCaP-ARhi: 4-5 fold) receptor amounts of protein. We cultured the cell lines in androgen depleted medium for 4 days and subsequently treated them for 2 hours with vehicle or 1nM and 100nM of 5α-dihydrotestosterone (DHT). Subsequently, we used chromosome immunoprecipitation and deep sequencing (ChIP-seq) to identify AR binding. Expression profiling was done by Illumina array. The data analysis is ongoing. We first studied the well known AR target gene PSA. Our data indicated that in depleted medium there is not apparent difference in the loading of the promoter and enhancer of the PSA regulatory region in different cell lines. Instead, the promoter and the enhancer are more loaded in LNCaP-ARmo/−ARhi than in control cell line upon DHT stimulation. Our preliminary data show that there is a positive correlation between AR-levels and whole genome-wide binding upon stimulation with 1 nM DHT. Whereas, in 100 nM DHT, which is a saturating concentration of the ligand, there is a negative correlation. In the 1 nM DHT, AR seems to bind to different genomic loci in LNCaP-ARhi or ARmo than in control cells. In conclusions, the amount of AR has an effect on the chromatin binding of the receptor. Cells overexpressing AR seems to be more androgen-responsive.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2942.

Increased expression of androgen receptor sensitizes prostate cancer cells to low levels of androgens

Androgen receptor (AR) is known to be overexpressed in castration-resistant prostate cancer. To interrogate the functional significance of the AR level, we established two LNCaP cell sublines expressing in a stable fashion two to four times (LNCaP-ARmo) and four to six times (LNCaP-ARhi) higher level of AR than the parental cell line expressing the empty vector (LNCaP-pcDNA3.1). LNCaP-ARhi cell line grew faster than the control line in low concentrations, especially in 1 nmol/L 5alpha-dihydrotestosterone (DHT). Microarray-based transcript profiling and subsequent unsupervised hierarchical clustering showed that LNCaP-ARhi cells clustered together with VCaP cells, containing endogenous AR gene amplification and overexpression, indicating the central role of AR in the overall regulation of gene expression in prostate cancer cells. Two hundred forty genes showed >2-fold changes on DHT treatment in LNCaP-ARhi at 4 h time point, whereas only 164 and 52 showed changes in LNCaP-ARmo and LNCaP-pcDNA3.1, respectively. Many androgen-regulated genes were upregulated in LNCaP-ARhi at 10-fold lower concentration of DHT than in control cells. DHT (1 nmol/L) increased expression of several cell cycle-associated genes in LNCaP-ARhi cells. ChIP-on-chip assay revealed the presence of chromatin binding sites for AR within +/-200 kb of most of these genes. The growth of LNCaP-ARhi cells was also highly sensitive to cyclin-dependent kinase inhibitor, roscovitine, at 1nmol/L DHT. In conclusion, our results show that overexpression of AR sensitizes castration-resistant prostate cancer cells to the low levels of androgens. The activity of AR signaling pathway is regulated by the levels of both ligand and the receptor.

Castration-resistant prostate cancer: from new pathophysiology to new treatment targets

CONTEXT

Castration-resistant prostate cancer (CRPC) refers to patients who no longer respond to surgical or medical castration. Standard treatment options are limited.

OBJECTIVE

To review the concepts and rationale behind targeted agents currently in late-stage clinical testing for patients with CRPC.

EVIDENCE ACQUISITION

Novel targeted therapies in clinical trials were identified from registries. The MEDLINE database was searched for all relevant reports published from 1996 to October 2009. Bibliographies of the retrieved articles and major international meeting abstracts were hand-searched to identify additional studies.

EVIDENCE SYNTHESIS

Advances in our understanding of the molecular mechanisms underlying prostate cancer (PCa) progression has translated into a variety of treatment approaches. Agents targeting androgen receptor (AR) activation and local steroidogenesis, angiogenesis, immunotherapy, apoptosis, chaperone proteins, the insulin-like growth factor (IGF) pathway, RANK-ligand, endothelin receptors, and the Src family kinases are entering or have recently completed accrual to phase 3 trials for patients with CRPC.

CONCLUSIONS

A number of new agents targeting mechanisms of PCa progression with early promising results are in clinical trials and have the potential to provide novel treatment options for CRPC in the near future.

TCEB1 promotes invasion of prostate cancer cells

Amplification of the long arm of chromosome 8 is one of the most recurrent findings in prostate cancer and it is associated with poor prognosis. Several minimal regions of amplification suggest multiple target genes which are yet to be identified. We have previously shown that TCEB1, EIF3S3, KIAA0196 and RAD21 are amplified and overexpressed in prostate cancer and they are located in the 8q area. In this study, we examined the functional effects of these genes to prostate cancer cell phenotype. We overexpressed and inhibited the genes by lentivirus mediated overexpression and RNA interference, respectively. shRNA mediated TCEB1 silencing decreased significantly cellular invasion of PC-3 and DU145 cells through Matrigel. TCEB1 silencing reduced the anchorage-independent growth of PC-3 cells. Similar effects were not seen with any other genes. When overexpressed in NIH 3T3 cells, TCEB1 and EIF3S3 increased the growth rate of the cells. Transcriptional profiling of TCEB1 silenced PC-3 cells revealed decrease of genes involved in invasion and metastasis. Finally, we also confirmed here the overexpression of TCEB1 in hormone-refractory prostate tumors. This study indicates that TCEB1 promotes invasion of prostate cancer cells, is involved in development of hormone-refractory prostate cancer and is thereby a strong candidate to be one of the target genes for the 8q gain.

Biological aggressiveness of prostate cancer in the Finnish screening trial

Prostate cancer aggressiveness was evaluated based on pathologic characterization of cases detected in the Finnish prostate cancer screening trial. The trial population consists of 80,458 men aged 55-67 years. A total of 32,000 men were randomized to the screening arm. The remaining 48,000 men formed the control arm. The interval cases and cancers among nonparticipants and in the control arm were identified from the Finnish Cancer Registry. Random samples were selected from screen-detected cases (126 of 543 in the first and 133 of 508 in the second round) and control arm cancers (133 out of 863), in addition to all 92 interval cancers and 106 cases among nonparticipants. All the biopsies were regraded according to the Gleason system. The expression of the proliferation antigen Ki-67 was determined in 479 cases (72%). More than half of the tumors diagnosed in the first round of screening were high-grade cancers (Gleason 7 or higher). In the second round, the proportion of low-grade cancers increased from 47% to 70%. Cancers in the screening arm were more commonly focal and fewer bilateral cancers were detected. The cancers among nonparticipants were the most aggressive group. The aggressiveness of the interval cancers was between the cancers detected in the first and the second round. Our results indicate that prostate cancers detected through screening are less biologically aggressive. This was most notable after the first screening round. Nonparticipants had more aggressive cancers.

Generation of a conditionally replicating adenovirus based on targeted destruction of E1A mRNA by a cell type-specific MicroRNA

MicroRNAs have emerged as important players in tissue-specific mammalian gene regulation and have also been exploited in experimental targeting of gene expression. We have constructed a recombinant adenovirus that contains sequences complementary to the liver-specific microRNA 122 (miR122) in the 3' untranslated region of the E1A gene. In Huh7 cells, which resemble normal hepatocytes in expressing high levels of miR122, this feature resulted in strongly reduced levels of E1A mRNA and protein. This property allowed us to generate a novel recombinant adenovirus that was severely attenuated in cells of hepatic origin but replicated normally in other cells. This strategy may be useful in circumventing liver toxicity associated with the systemic delivery of oncolytic adenoviruses. These data provide the first example of exploiting differential microRNA expression patterns to alter the natural tropism of a DNA virus. In addition, these results suggest that other microRNAs expressed in a tissue- or transformation-specific manner may also be used for the targeting of adenoviral replication and that the same principle may be applied to other viruses that have shown promise as oncolytic or gene delivery platforms.

Somatic mutation analysis of MYH11 in breast and prostate cancer

BACKGROUND

MYH11 (also known as SMMHC) encodes the smooth-muscle myosin heavy chain, which has a key role in smooth muscle contraction. Inversion at the MYH11 locus is one of the most frequent chromosomal aberrations found in acute myeloid leukemia. We have previously shown that MYH11 mutations occur in human colorectal cancer, and may also be associated with Peutz-Jeghers syndrome. The mutations found in human intestinal neoplasia result in unregulated proteins with constitutive motor activity, similar to the mutant myh11 underlying the zebrafish meltdown phenotype characterized by disrupted intestinal architecture. Recently, MYH1 and MYH9 have been identified as candidate breast cancer genes in a systematic analysis of the breast cancer genome.

METHODS

The aim of this study was to investigate the role of somatic MYH11 mutations in two common tumor types; breast and prostate cancers. A total of 155 breast cancer and 71 prostate cancer samples were analyzed for those regions in MYH11 (altogether 8 exons out of 42 coding exons) that harboured mutations in colorectal cancer in our previous study.

RESULTS

In breast cancer samples only germline alterations were observed. One prostate cancer sample harbored a frameshift mutation c.5798delC, which we have previously shown to result in a protein with unregulated motor activity.

CONCLUSION

Little evidence for a role of somatic MYH11 mutations in the formation of breast or prostate cancers was obtained in this study.

Clusterin is epigenetically regulated in prostate cancer

Lack of good models has complicated investigations on the mechanisms of prostate cancer. By far, the most commonly used transgenic mouse model of prostate cancer is TRAMP, which, however, has not been fully characterized for genetic and epigenetic aberrations. Here, we screened TRAMP-derived C2 cell line for the alterations using different microarray approaches, and compared it to human prostate cancer. TRAMP-C2 had relatively few genomic copy number alterations according to array comparative genomic hybridization (aCGH). However, the gene copy number and expression were significantly correlated (p < 0.001). Screening genes for promoter hypermethylation using demethylation treatment with 5-aza-2'-deoxycytidine and subsequent expression profiling indicated 43 putatively epigenetically silenced genes. Further studies revealed that clusterin is methylated in the TRAMP-C2 cell line, as well as in the human prostate cancer cell line LNCaP. Its expression was found to be significantly reduced (p < 0.01) in untreated and hormone-refractory human prostate carcinomas. Together with known function of clusterin, the data suggest an epigenetic component in the regulation of clusterin in prostate cancer.

TMPRSS2:ERG fusion identifies a subgroup of prostate cancers with a favorable prognosis

PURPOSE

Our aim was to assess the frequency of ERG overexpression and TMPRSS2:ERG rearrangement in prostate cancer and their association with clinicopathologic variables and outcome.

EXPERIMENTAL DESIGN

The presence of the TMPRSS2:ERG rearrangement was studied by reverse transcription-PCR and fluorescence in situ hybridization in 19 prostate cancer xenografts and 7 prostate cancer cell lines. The expression of ERG was studied in the xenografts and cell lines and in 49 freshly frozen clinical prostate samples by quantitative reverse transcription-PCR. The frequency of the TMPRSS2:ERG fusion in clinical prostate cancer (n = 253) on tissue microarrays was assessed by three-color fluorescence in situ hybridization.

RESULTS

Seven of 19 (37%) of the xenografts overexpressed ERG and had TMPRSS2:ERG rearrangement. Two xenografts, representing small cell carcinomas, also contained the fusion but did not express ERG. In clinical tumor specimens, the overexpression of ERG was associated with the rearrangement (P = 0.0019). Fifty of 150 (33%) of the prostatectomy specimens and 28 of 76 (37%) of the hormone-refractory prostate cancers on the tissue microarrays carried the TMPRSS2:ERG rearrangement. It was associated with longer progression-free survival in patients treated by prostatectomy (P = 0.019), and according to multivariate analysis, it was an independent predictor of favorable outcome (relative risk, 0.54; 95% confidence interval, 0.30-0.98). The fusion was not associated with Gleason score, pT stage, diagnostic prostate-specific antigen, or cell proliferation activity in prostatectomy specimens nor with the AR gene amplification in hormone-refractory tumors.

CONCLUSIONS

The TMPRSS2:ERG rearrangement can be found in about one third of prostate cancers. A subgroup of prostate cancer patients with a good prognosis may be identified by the rearrangement.

Androgen regulation of the androgen receptor coregulators

Background

The critical role of the androgen receptor (AR) in the development of prostate cancer is well recognized. The transcriptional activity of AR is partly regulated by coregulatory proteins. It has been suggested that these coregulators could also be important in the progression of prostate cancer. The aim of this study was to identify coregulators whose expression is regulated by either the androgens and/or by the expression level of AR.

Methods

We used empty vector and AR cDNA-transfected LNCaP cells (LNCaP-pcDNA3.1, and LNCaP-ARhi, respectively), and grew them for 4 and 24 hours in the presence of dihydrotestosterone (DHT) at various concentrations. The expression of 25 AR coregulators (SRC1, TIF2, PIAS1, PIASx, ARIP4, BRCA1, β-catenin, AIB3, AIB1, CBP, STAT1, NCoR1, AES, cyclin D1, p300, ARA24, LSD1, BAG1L, gelsolin, prohibitin, JMJD2C, JMJD1A, MAK, PAK6 and MAGE11) was then measured by using real-time quantitative RT-PCR (Q-RT-PCR).

Results

Five of the coregulators (AIB1, CBP, MAK, BRCA1 and β-catenin) showed more than 2-fold induction and 5 others (cyclin D1, gelsolin, prohibitin, JMJD1A, and JMJD2C) less than 2-fold induction. Overexpression of AR did not affect the expression of the coregulators alone. However, overexpression of AR enhanced the DHT-stimulated expression of MAK, BRCA1, AIB1 and CBP and reduced the level of expression of β-catenin, cyclinD1 and gelsolin.

Conclusion

In conclusion, we identified 5 coactivators whose expression was induced by androgens suggesting that they could potentiate AR signaling. Overexpression of AR seems to sensitize cells for low levels of androgens.