Zaki Shaikhibrahim

ETS transcription factors and prostate cancer: the role of the family prototype ETS-1 (review).

The ETS family of transcription factors is known to play important roles in various biological processes such as development, differentiation, proliferation, apoptosis, migration, tissue remodeling, invasion and angiogenesis in various cell types including B cells, endothelial cells, fibroblasts as well as diverse neoplastic cells. In prostate cancer, recurrent gene fusions involving members of the ETS family are frequently reported. ETS-1, the prototype of the ETS family, is expressed in different cell types and is known to play various roles during both physiological and pathological conditions. In this review, we focus on studies investigating the role of ETS-1 in prostate cancer.

The peripheral zone of the prostate is more prone to tumor development than the transitional zone: Is the ETS family the key?

Predisposition to develop prostate cancer (PCA) varies among the prostate zones, with the peripheral zone (PZ) more prone to tumor development than the transitional zone (TZ). In view of the fact that molecular differences between the zones may explain this difference, combined with the findings that translocations between TMPRSS2 and several ETS members are frequently observed in PCA, we hypothesized that the ETS family may be crucial to explaining this difference. Normal tissues from the PZ and the TZ of 20 PCA patients were laser microdissected to separate glands from stroma. Two oligo microarrays were performed in order to investigate the variation in ETS family gene expression between the glands and the stroma of the two zones. The ETS members, ELF-3, ELF-5, ERG, ETV-1, ETV-4, ETV-5, ETV-7 and FEV, were found to be differentially expressed. A striking observation was that ERG and ETV-1 were found to be up-regulated in the glands of the PZ compared to the TZ, particularly when considering that ERG and ETV-1 fusions account for 50-80% and 20% of PCA occurrences, respectively. These results indicate that the glands and stroma of the two zones display distinct molecular differences and zonal-specific expression of ETS members. Furthermore, ETS members up-regulated in PCA are already overexpressed in the normal PZ, suggesting that these members play a role in the development and progression of PCA.

Epigenetics-related genes in prostate cancer: expression profile in prostate cancer tissues, androgen-sensitive and -insensitive cell lines

Epigenetic changes have been suggested to drive prostate cancer (PCa) development and progression. Therefore, in this study, we aimed to identify novel epigenetics-related genes in PCa tissues, and to examine their expression in metastatic PCa cell lines. We analyzed the expression of epigenetics-related genes via a clustering analysis based on gene function in moderately and poorly differentiated PCa glands compared to normal glands of the peripheral zone (prostate proper) from PCa patients using Whole Human Genome Oligo Microarrays. Our analysis identified 12 epigenetics-related genes with a more than 2-fold increase or decrease in expression and a p-value <0.01. In moderately differentiated tumors compared to normal glands of the peripheral zone, we found the genes, TDRD1, IGF2, DICER1, ADARB1, HILS1, GLMN and TRIM27, to be upregulated, whereas TNRC6A and DGCR8 were found to be downregulated. In poorly differentiated tumors, we found TDRD1, ADARB and RBM3 to be upregulated, whereas DGCR8, PIWIL2 and BC069781 were downregulated. Our analysis of the expression level for each gene in the metastatic androgen-sensitive VCaP and LNCaP, and -insensitive PC3 and DU-145 PCa cell lines revealed differences in expression among the cell lines which may reflect the different biological properties of each cell line, and the potential role of each gene at different metastatic sites. The novel epigenetics-related genes that we identified in primary PCa tissues may provide further insight into the role that epigenetic changes play in PCa. Moreover, some of the genes that we identified may play important roles in primary PCa and metastasis, in primary PCa only, or in metastasis only. Follow-up studies are required to investigate the functional role and the role that the expression of these genes play in the outcome and progression of PCa using tissue microarrays.

Analysis of laser-microdissected prostate cancer tissues reveals potential tumor markers

Prostate cancer (PCA) is a clinically heterogeneous and often multifocal disease with a clinical outcome difficult to predict. A deeper knowledge of the molecular basis of the disease may lead to a better prediction of prognosis. Therefore, in this study we investigated the molecular basis of PCA by identifying potential tumor markers in laser-microdisected PCA tissues. Among a group of PCA patients, quantitative RT-PCR analysis was performed to compare the expression of 70 genes. These genes were selected from the results of two microarrays which investigated the gene expression profile differences between moderately or poorly differentiated prostate carcinoma glands and the corresponding normal glands. Among the genes examined, CDKN2A, GATA3, CREBBP, ITGA2, NBL1 and TGM4 were down-regulated in the prostate carcinoma glands compared to the corresponding normal glands, whereas TFF3, TMPRSS2 and ERG were up-regulated. Our findings indicate that these genes may play roles as tumor suppressor genes or oncogenes in PCA, and may serve as potential tumor markers and novel therapeutic targets.

ERG rearrangement in local recurrences compared to distant metastases of castration-resistant prostate cancer

Castration-resistant prostate cancer is the second most common cause of cancer death and results in a median survival of less than 2xa0years. In prostate cancer, fusions between TMPRSS2 and ERG are common. The ERG rearrangement prevalence in local recurrent castration-resistant prostate cancer compared to distant metastatic prostate cancer is unknown. We investigated the frequency of ERG rearrangement in local recurrent castration-resistant prostate cancer compared to distant metastatic prostate cancer, and assessed for associations between androgen receptor (AR) amplification and ERG rearrangement status. Samples from 134 patients diagnosed with prostate cancer (84 local recurrent castration resistant prostate cancer, 55 distant metastatic prostate cancer) were assessed for their ERG rearrangement and AR amplification status by fluorescence in situ hybridization. Statistical analysis was performed using the χ2 test. We found that the ERG rearrangement occurs at a significantly lower frequency in distant metastatic prostate cancer (25xa0%) than in local recurrent castration-resistant prostate cancer (45xa0%). The AR amplification frequencies were 45 and 35xa0% in local recurrent castration-resistant prostate cancer and distant metastatic prostate cancer, respectively. The ERG rearrangement occurred at a lower frequency in distant metastatic prostate cancer compared to local recurrent castration-resistant prostate cancer.

Rearrangement of the ETS genes ETV-1, ETV-4, ETV-5, and ELK-4 is a clonal event during prostate cancer progression

ETS gene rearrangements are frequently found in prostate cancer. Several studies have assessed the rearrangement status of the most commonly found ETS rearranged gene ERG, and the less frequent genes, ETV-1, ETV-4, ETV-5, and ELK-4 in primary prostate cancer. However, frequency in metastatic disease is not well investigated. Recently, we have assessed the ERG rearrangement status in both primary and corresponding lymph node metastases and observed that ERG rearrangement in primary prostate cancer transfers into lymph node metastases, suggesting it to be a clonal expansion event during prostate cancer progression. As a continuation, we investigated in this study whether this observation is valid for the less frequent ETS rearranged genes. Using dual-color break-apart fluorescent in situ hybridization assays, we evaluated the status of all less frequent ETS gene rearrangements for the first time on tissue microarrays constructed from a large cohort of 86 patients with prostate cancer and composed of primary and corresponding lymph node metastases, as well as in a second cohort composed of 43 distant metastases. ETV-1, ETV-4, ETV-5, and ELK-4 rearrangements were found in 8 (10%) of 81, 5 (6%) of 85, 1 (1%) of 85, and 2 (2%) of 86 of primary prostate cancer, respectively, and in 6 (8%) of 73, 4 (6%) of 72, 1 (1%) of 75, and 1 (1%) of 78 of corresponding lymph node metastases, respectively. ETV-1 and ETV-5 rearrangements were not found in the distant metastases cases, whereas ETV-4 and ELK-4 rearrangements were found in 1 (4%) of 25 and 1 (4%) of 24, respectively. Our findings suggest that rearrangement of the less frequent ETS genes is a clonal event during prostate cancer progression.

Ets-1 is implicated in the regulation of androgen co-regulator FHL2 and reveals specificity for migration, but not invasion, of PC3 prostate cancer cells

Different members of the Ets-family of transcription factors are involved in TMPRSS-2-Ets translocations frequently found in human prostate cancers. We previously reported that Ets-1, which is the prototype of Ets-family members, promotes both migration and invasion of melanoma, Hela and glioma cells. Here, we examined whether Ets-1 has a similar effect upon migration and invasion of PC3 prostate cancer cells, and whether it is implicated in the regulation of the androgen co-regulator four and a half LIM only protein-2 (FHL2). Two stable PC3 cell cultures were established by transfection with either an Ets-1 inverse antisense expression vector or a mock control vector. Western blot analysis confirmed presence of Ets-1 in mock and absence in Ets-1 inverse cells. Microarray and qRT-PCR revealed an up-regulation of FHL2 in Ets-1 blocked cells, compared to mock. To examine the effects of Ets-1 upon cell migration, a wound assay was performed, and demonstrated that wounds were completely colonized by mock compared to Ets-1 blocked cells after 55 h. Evaluation of the effect upon invasion was examined using the Boyden chamber, which revealed no significant difference between mock and Ets-1 blocked cells. In conclusion, our study demonstrated for the first time that Ets-1 is implicated in the regulation of the androgen co-regulator FHL2, and reveals specificity of action for migration, but not invasion of PC3 prostate cancer cells.

Comprehensive gene expression microarray analysis of Ets-1 blockade in PC3 prostate cancer cells and correlations with prostate cancer tissues: Insights into genes involved in the metastatic cascade

Ets-1 is the prototype of the ETS family of transcription factors and is suggested to play an important role in the malignant progression of prostatic carcinomas. Therefore, in this study we investigated the effect of blocking Ets-1 in PC3 prostate cancer cells on genes involved in the metastatic cascade, and correlated these findings with prostate cancer tissues. Two stable PC3 cell cultures were established by transfection with either an Ets-1 inverse antisense expression vector or a mock control vector. The effect of blocking Ets-1 on genes involved in the metastatic cascade was assessed by a comprehensive gene expression microarray analysis of Ets-1 inverse and mock control cells. Correlating the sets of genes found in the PC3 microarray data with prostate cancer tissues was performed by verifying the genes in a comprehensive gene expression microarray analysis of RNA extracted from laser microdissected normal prostate glands and from carcinoma glands taken from prostate cancer patients. Western blot analysis confirmed the presence of Ets-1 in mock cells and its absence in Ets-1 inverse cells. In the Ets-1 blockade microarray, many differentially expressed genes were found; however, only genes with a greater than 10-fold up- or down-regulation between the Ets-1 blockade and mock control were considered significant. The genes were placed into four groups that play a role in the so-called metastatic cascade based on their known functions in proliferation, apoptosis, migration and angiogenesis. The genes found in the Ets-1 blockade microarray analysis were verified for their presence in the microarray analysis of prostate cancer tissues. Genes found in the microarray analysis of prostate cancer tissues with an >2-fold change and a p-value <0.01 were considered significant. We identified sets of genes that are involved in the metastatic cascade and are known to be implicated in prostate cancer to show changes in the expression patterns due to the Ets-1 blockade in PC3 cells. Correlating these sets of genes with the findings in prostate cancer tissues, we identified 16 genes that are up- or down-regulated in healthy compared to tumor prostate glands. Further investigation revealed that 4 out of the 16 genes have been reported to be regulated by members of the ETS family. These findings provide inxa0vitro and inxa0vivo evidence for the importance of Ets-1 in the development and progression of prostate cancer.

Identification of immunity-related genes in prostate cancer and potential role of the ETS family of transcription factors in their regulation

The role of the immune response in tumor progression, and disease outcome is still debated, and a lack of knowledge of the immune defenses in prostate cancer still exists. In addition, the ETS family of transcription factors which is involved in translocations frequently found in prostate cancer is reported to be essential for the regulation of immunity-related genes. In order to identify immunity-related genes in prostate cancer, we performed two microarrays using RNA extracted from laser microdissected glands of the normal prostate proper (or the peripheral zone) and moderately and poorly differentiated prostate carcinomas from patients who had undergone radical prostatectomy. Many differentially expressed genes were found, however, only immunity-related genes (B cell, innate, and T cell immunity) with an expression of more than 10-fold increase or decrease and a P<0.01 between the moderately differentiated tumors and the normal glands, and the poorly differentiated tumors and the normal glands were considered significant. Based on these two microarrays, we identified a set of 37 genes that were up- or down-regulated in tumors (moderately and poorly differentiated) compared to the normal glands. Analysis of these genes revealed, strikingly, that 31/37 of these genes have potential binding sites within their promoter regions for members of the ETS family of transcription factors, and some are reported to be targets of ETS members. These findings identified immunity-related genes in prostate cancer, and provided insights into their potential regulation, which may lead to a better early detection, immunotherapy, and therapeutic drug treatment of this disease. Unraveling the dynamics of the ETS-immunity-related genes will provide an invaluable insight into understanding prostate cancer immunology.

Differential expression of ETS family members in prostate cancer tissues and androgen-sensitive and insensitive prostate cancer cell lines

The ETS family of transcription factors plays important roles in both normal and neoplastic cells for different biological processes such as proliferation, differentiation, development, transformation, apoptosis, migration, invasion and angiogenesis. The 27 ETS factors are probably a part of complex regulatory networks including interactions among family members. In human prostate cancer, rearrangements have been found in several genes of the ETS family resulting in chimeric oncoproteins. In a previous study we found that the ETS family prototype, Ets-1 affects biological properties of PC3 prostate cancer cells. In a first effort to understand the cooperative interactions between different ETS factors in prostate cancer, in the present study we examined the expression pattern of all 27 ETS members using quantitative RT-PCR (qRT-PCR) in the androgen-sensitive VCaP and LNCaP, and the androgen-insensitive PC3 and DU-145 prostate cancer cell lines as well as in human prostate cancer tissue samples. We further investigated whether the ETS family prototype, Ets-1, regulates other ETS family members by examining the effect of Ets-1 blockade in PC3 cells on their expression. We found an expression specificity of various ETS family members in the prostate cancer cell lines which might reflect their different biological properties. In human prostate samples only 3 among the 27 ETS family members (Ehf, Elk-4 and Ets-2) showed significant expression differences between normal and cancerous prostate glands. We finally demonstrate that the family prototype, Ets-1, regulates the family members Elf-1, Elf-2, Elk-1, Etv-5 and Spi-1 in PC3 prostate cancer cells. Chimeric oncoproteins containing ETS family members arising due to frequent translocations in prostate cancer are probably part of a regulatory network involving other ETS family members as well.