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- Title
- MICRORNA REGULATION OF PROSTATE CANCER DESENSITIZATION TO ANDROGEN RECEPTOR ANTAGONIST DRUGS DURING ANDROGEN DEPRIVATION THERAPY.
- Creator
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Lorch, Robert, Chakrabarti, Ratna, University of Central Florida
- Abstract / Description
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The current standard treatment of prostate cancer by androgen deprivation therapy involves using drugs such as bicalutamide (Casodex) to antagonistically block androgen receptors that are normally present within prostate cells. Usually, the therapy is successful in the short run at limiting the growth of prostate cancer. However, in virtually all cases tumors begin to grow aggressively again after several months of treatment and new therapies must be started. The mechanism by which these...
Show moreThe current standard treatment of prostate cancer by androgen deprivation therapy involves using drugs such as bicalutamide (Casodex) to antagonistically block androgen receptors that are normally present within prostate cells. Usually, the therapy is successful in the short run at limiting the growth of prostate cancer. However, in virtually all cases tumors begin to grow aggressively again after several months of treatment and new therapies must be started. The mechanism by which these prostate cells transform from androgen sensitive to androgen independent and anti-androgen resistant is unclear. In this study, we investigated the role of microRNAs, small 15 to 18 nucleotide regulatory RNAs, in regulating the desensitization of prostate cancer cells to the androgen receptor antagonist drug bicalutamide. In order to identify significant microRNAs, quantitative PCR was used to obtain genome-wide microRNA expression levels of 885 human microRNAs at different timepoints for androgen sensitive LNCaP cancer cells treated with bicalutamide and for untreated control cells in tissue culture. Analysis of microRNA expression by clustering analysis and by statistical comparisons of treatment groups resulted in identification of 28 microRNAs that have altered expression in the progression process. In silico target prediction analysis was performed with the microRNAs shown to have altered expression, and a group of genes predicted to be under microRNA regulatory control during cancer progression to resistance was identified. A microRNA expression profile can be useful in developing more effective prognostic and therapeutic tools for prostate cancer.
Show less - Date Issued
- 2011
- Identifier
- CFH0003826, ucf:44740
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0003826
- Title
- THE ROLE OF FRABIN (FGD4) IN AGGRESSIVE PROSTATE CANCER.
- Creator
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Bossan, Alexia M, Chakrabarti, Ratna, University of Central Florida
- Abstract / Description
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A major problem in prostate cancer (PCa) management is the development of drug resistance. It is known that there are changes in PCa biology upon prolonged treatment with drugs, including anti-androgen drugs that alter cellular signaling processes leading to the development of castration resistant PCa. MicroRNAs (miRNAs) are regulatory molecules that modulate gene expression through inhibition of protein translation and modulate cellular functions. Altered expression of miRNAs is often noted...
Show moreA major problem in prostate cancer (PCa) management is the development of drug resistance. It is known that there are changes in PCa biology upon prolonged treatment with drugs, including anti-androgen drugs that alter cellular signaling processes leading to the development of castration resistant PCa. MicroRNAs (miRNAs) are regulatory molecules that modulate gene expression through inhibition of protein translation and modulate cellular functions. Altered expression of miRNAs is often noted in drug resistant cancer including PCa. Studies from our laboratory have identified a number of down-regulated miRNAs in PCa, including miR-l 7-92a miRNAs. Frabin (FGD4) is a target of the miR-l 7-92a cluster that was found to be up-regulated in PCa cells. For this paper's investigation, an FGD4 knockdown approach was used to identify the effects on cell viability, cell cycle progression, cell migration and drug sensitivity. Two PCa cells lines, LNCaP-104S (androgen sensitive) and PC-3 (androgen independent), were used for our studies. MTS assays for both cell lines showed significant reduction in cell viability following knockdown of FGD4 compared to transfection with control siRNAs. Cell cycle analysis revealed an arrest in the G2/M phase of the cells that were transfected with FGD4 siRNAs. Cell migration assays revealed a decrease in migration rate of PC-3 cells after knockdown, which supports the involvement of FGD4 in actin- cytoskeleton rearrangement. Treatments with anti-mitotic drug Docetaxel (PC-3) or androgen receptor antagonist bicalutamide/Casodex (LNCaP-104S) showed improved sensitivity of the FGD4 siRNA treated cells to these drugs. Our results suggest the potential for FGD4 knockdown to be used in combination with currently used drugs, increasing the effectiveness of frontline chemotherapeutics.
Show less - Date Issued
- 2017
- Identifier
- CFH2000162, ucf:45937
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000162
- Title
- A major double strand repair pathway and cancer-associated circulating proteins are effecters of epigenetic revision.
- Creator
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Allen, Brittany, Masternak, Michal, Khaled, Annette, Zhao, Jihe, Muller, Mark, Siddiqi, Shadab, University of Central Florida
- Abstract / Description
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DNA methylation is a vital epigenetic process that acts as a major control mechanism for gene expression. In addition to its essential role in many normal cellular processes, it is also implicated in a wide variety of disease states and processes including cancer. Along with genetic mutations, aberrant DNA methylation patterns, specifically the inappropriate DNA methylation or demethylation of CpG residues, may activate oncogenes or suppress tumor suppressor genes, respectively. These changes...
Show moreDNA methylation is a vital epigenetic process that acts as a major control mechanism for gene expression. In addition to its essential role in many normal cellular processes, it is also implicated in a wide variety of disease states and processes including cancer. Along with genetic mutations, aberrant DNA methylation patterns, specifically the inappropriate DNA methylation or demethylation of CpG residues, may activate oncogenes or suppress tumor suppressor genes, respectively. These changes can generate or facilitate the progression of tumorigenesis and tend to accumulate throughout the development of cancer. Although they play such a major role in cancer and in other diseases, it remains unclear what causes these epigenetic revisions to occur. This dissertation will focus on uncovering mechanisms that are sources of epigenetic revision, specifically as they relate to cancer. Due to rapid cell division and increased DNA damage, cells are increasingly dependent on DNA repair as they continue on a path of tumorigenic progression. We hypothesize that DNA repair, specifically the repair of DNA double strand breaks (DSB) by Non-Homologous End Joining (NHEJ) may play a role in inappropriate epigenetic revision. Using a GFP reporter system inserted into the genome of HeLa cells, we are able to induce targeted DNA damage that enables the cells, after successfully undergoing NHEJ repair, to express WT GFP. These GFP+ cells were segregated into two expression classes, one with robust expression (Bright) and the other with reduced expression (Dim). Using a DNA hypomethylating drug (AzadC) we were able to demonstrate that the different GFP expression levels was due to differential methylation statuses of CpGs in regions on either side of the break site. Deep sequencing analysis of this area in sorted Bright and Dim populations revealed a collection of different epi-alleles that display patterns of DNA methylation following repair by NHEJ. These patterns differ between Bright and Dim cells which are hypo- and hypermethylated, respectively, and between the post-repair populations and the original, uncut cells. These data suggest that NHEJ repair facilitates a rewrite of the methylation landscape in repaired genes, elucidating one potential source for the altered methylation patterns seen in cancer cells.The Dim cells generated during this study are known to have a hypermethylated GFP gene that is correlated with reduced expression, allowing it to be used as a screening tool for hypomethylating agents. We used this tool to screen the blood serum of patients with head and neck squamous cell carcinoma (HNSCC). We found that the serum from HNSCC patients, but not from healthy individuals, contains some factor that causes hypomethylation in exposed cells. Further, we were able to identify this factor as a protein capable of effecting changes in DNA methylation, gene expression, and miRNA levels in the treated Dim cells. The novel concept presented in this study has immense implications on the study of cancer progression as it evidences circulating proteins, presumably released by cancer cells, which are able to effect gene expression in cells that are distal to the location of the cancer. Further, the fact that these proteins are in circulation makes them a potential target for use in diagnostics. Changes in DNA methylation play a major role in the development of cancer and understanding the mechanisms by which this occurs could provide new therapeutic targets for preventing this process from contributing to tumorigenesis. This dissertation presents potential sources of epigenetic revision in cancer and thus provides answers to a major question that has yet to be answered in the area of cancer research.
Show less - Date Issued
- 2017
- Identifier
- CFE0006555, ucf:51333
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006555
- Title
- Involvement of miRNAs in the Development of Androgen Independent Prostate Cancer.
- Creator
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Ottman, Richard, Chakrabarti, Ratna, Cole, Alexander, Khaled, Annette, Zervos, Antonis, University of Central Florida
- Abstract / Description
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Development of resistance to androgen deprivation therapy (ADT) is a major obstacle for the management of advanced prostate cancer. Therapies with androgen receptor (AR) antagonists and androgen withdrawal initially result in tumor regression but development of compensatory mechanisms including AR bypass signaling leads to tumor re-growth, independent of circulating androgens. The result is the emergence of castration resistant prostate cancer (CRPC), a highly morbid disease exhibiting...
Show moreDevelopment of resistance to androgen deprivation therapy (ADT) is a major obstacle for the management of advanced prostate cancer. Therapies with androgen receptor (AR) antagonists and androgen withdrawal initially result in tumor regression but development of compensatory mechanisms including AR bypass signaling leads to tumor re-growth, independent of circulating androgens. The result is the emergence of castration resistant prostate cancer (CRPC), a highly morbid disease exhibiting aberrant expression of many protein-coding and non-coding genes. Under the umbrella of non-coding RNAs is a class of small regulatory RNAs referred to as microRNAs (miRNAs). MicroRNAs are believed to function in the maintenance of cell homeostasis but are often differentially expressed in many different types of cancer including CRPC.In this study, the association of genome wide miRNA expression (1113 unique miRNAs) with development of resistance to ADT was determined. Androgen sensitive prostate cancer cells that progressed to ADT and AR antagonist Casodex (CDX) resistance upon androgen withdrawal and treatment with CDX were used. Validation of expression of a subset of 100 miRNAs led to identification of 43 miRNAs that are significantly altered during progression of cells to treatment resistance. A correlation of altered expression of 10 proteins targeted by some of these miRNAs in these cells was shown.Additionally, profiles of miRNA expressions in cancerous prostate tissues were created and compared with profiles of paired adjacent uninvolved areas of prostate tissue. Among the miRNAs identified from these analyses, a cluster of miRNAs, miR-17-92a, that is under-expressed in prostate tumors and in androgen independent prostate cancer cells was highlighted. The miR-17-92a cluster miRNAs are transcribed from a polycistronic transcription unit C13orf25 that generates six mature miRNAs: miR-17, miR-18a, miR-19a, miR-19b, miR-20a and miR-92a, and is commonly de-regulated in many cancers. In this research, the expression of miR-17-92a miRNAs was found to be reduced in cancerous prostate tissues when compared to uninvolved areas and also in aggressive prostate cancer cells. Restoration of expression of all members of miR-17-92a cluster showed decreased expression of cell cycle regulatory proteins cyclin D1 and SSH1; as well as LIMK1 and FGD4 of the RhoGTPase signaling pathway. Expression of miR-17-92a miRNAs caused decreased cell proliferation, reduced activation of AKT and MAP kinases, delayed tumorigenicity and reduced tumor growth in animals. Additionally, miR-17-92a miRNA expression inhibited EMT via reduced cell migration and expression of mesenchymal markers while elevating expression and surface localization of the epithelial marker e-cadherin. Expression of miR-17-92a miRNAs improved sensitivity of androgen dependent LNCaP104-S prostate cancer cells to the Androgen Receptor antagonist bicalutamide (CDX), AKT inhibitor MK-2206 2HCl, and docetaxel. Androgen refractory PC-3 cells also showed increased sensitivity to docetaxel, MK-2206 2HCl, and Aurora kinase inhibitor VX680 upon ectopic expression of miR-17-92a cluster miRNAs. In conclusion, dynamic alterations in miRNA expression occur early on during androgen deprivation therapy and androgen receptor blockade. The cumulative effect of these altered miRNA expression profiles is the temporal modulation of multiple signaling pathways promoting survival and acquisition of resistance. These early events are driving the transition to castration resistance and cannot be studied in already developed CRPC cell lines or tissues. Notably, these data demonstrate a tumor suppressor effect of miR-17-92a cluster miRNAs in prostate cancer cells and restoration of expression of these miRNAs has a therapeutic benefit for both androgen-dependent and -independent prostate cancer cells. Furthermore, these results can be used as a prognostic marker of cancers with a potential to be resistant to ADT.
Show less - Date Issued
- 2016
- Identifier
- CFE0006697, ucf:52866
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006697
