ABSTRACT
BACKGROUND: Overtreatment of low-grade prostate cancer is a recognised problem for clinicians and patients. However, under-treatment runs the risk of missing the opportunity for cure in those who could benefit. Identification of new biomarkers of disease progression, including metastases, is required to better stratify and appropriately treat these patients. The ability to predict if prostate cancer will recur is an important clinical question that would impact treatment options for patients. Studies in other cancers have associated MARCKS with metastasis. METHODS: Tissue microarrays of local prostatectomy samples from a cohort of biochemical recurrent and non-biochemical recurrent tumours were assayed for MARCKS protein expression. Prostate cancer cell lines were transfected with siRNA targeting MARCKS or a control and functional endpoints of migration, invasion, proliferation, viability and apoptosis were measured. Actin was visualised by fluorescent microscopy and evidence of a cadherin switch and activation of the AKT pathway were assayed. RESULTS: MARCKS was upregulated in biochemical recurrent patients compared to non-biochemical recurrent. Knockdown of MARCKS reduced migration and invasion of prostate cancer cells, reduced MMP9 mRNA expression, as well as decreasing cell spreading and increased cell:cell adhesion in prostate cancer cell colonies. Knockdown of MARCKS had no effect on proliferation, viability or apoptosis of the prostate cancer cells. CONCLUSIONS: In conclusion, MARCKS promotes migration and invasion and is associated with biochemical recurrence in localised prostate cancer tumours. The mechanisms by which this occurs have yet to be fully elucidated but lack of a cadherin switch indicates it is not via epithelial-to-mesenchymal transition. Actin rearrangement indicates that MARCKS promotes invasion through regulating the architecture of the cell.
ABSTRACT
Docetaxel is the main treatment for advanced castration-resistant prostate cancer; however, resistance eventually occurs. The development of intratumoral drug-resistant subpopulations possessing a cancer stem cell (CSC) morphology is an emerging mechanism of docetaxel resistance, a process driven by epithelial-mesenchymal transition (EMT). This study characterised EMT in docetaxel-resistant sublines through increased invasion, MMP-1 production and ZEB1 and ZEB2 expression. We also present evidence for differential EMT across PC-3 and DU145 in vitro resistance models as characterised by differential migration, cell colony scattering and susceptibility to the CSC inhibitor salinomycin. siRNA manipulation of ZEB1 and ZEB2 in PC-3 and DU145 docetaxel-resistant sublines identified ZEB1, through its transcriptional repression of E-cadherin, to be a driver of both EMT and docetaxel resistance. The clinical relevance of ZEB1 was also determined through immunohistochemical tissue microarray assessment, revealing significantly increased ZEB1 expression in prostate tumours following docetaxel treatment. This study presents evidence for a role of ZEB1, through its transcriptional repression of E-cadherin to be a driver of both EMT and docetaxel resistance in docetaxel-resistant prostate cancer. In addition, this study highlights the heterogeneity of prostate cancer and in turn emphasises the complexity of the clinical management of docetaxel-resistant prostate cancer.
Subject(s)
Antineoplastic Agents/pharmacology , Drug Resistance, Neoplasm , Epithelial-Mesenchymal Transition/drug effects , Homeodomain Proteins/genetics , Prostate/drug effects , Prostatic Neoplasms/drug therapy , Repressor Proteins/genetics , Taxoids/pharmacology , Zinc Finger E-box-Binding Homeobox 1/genetics , Antineoplastic Agents/therapeutic use , Cadherins/genetics , Cell Line, Tumor , Docetaxel , Gene Expression Regulation, Neoplastic/drug effects , Homeodomain Proteins/analysis , Humans , Male , Prostate/metabolism , Prostate/pathology , Prostatic Neoplasms/genetics , Prostatic Neoplasms/pathology , RNA Interference , RNA, Small Interfering/genetics , Repressor Proteins/analysis , Taxoids/therapeutic use , Up-Regulation/drug effects , Zinc Finger E-box Binding Homeobox 2 , Zinc Finger E-box-Binding Homeobox 1/analysisABSTRACT
In this study, a folate targeted cyclodextrin (CD) nanoparticle was prepared by co-formulating CD.siRNA complexes with DSPE-PEG5000-folate to target the prostate specific membrane antigen (PSMA). Targeted formulations showed increased uptake, relative to untargeted controls, in two prostate cancer cell lines expressing PSMA (VCaP and LNCaP). Competitive uptake studies, using excess folate, significantly reduced uptake of targeted nanoparticles in PSMA positive cell lines (P<0.001). Relative to untreated controls, folate-targeted nanoparticles significantly reduced the levels of RelA mRNA in VCaP and LNCaP cells by 44% and 22% respectively (P<0.001). In contrast there was no significant reduction in RelA mRNA in these cell lines by untargeted complexes. Pharmacokinetic (PK) data indicated that the incorporation of PEG into the formulation increased the circulation time of siRNA 8-fold. This study highlights the ability of incorporating a folate ligand into CD.siRNA nanoparticles to allow for targeted delivery of siRNA to prostate cancer cells via the PSMA.
