ABSTRACT
PTPL1, a non-receptor type protein tyrosine phosphatase, has been involved in the regulation of apoptosis and invasiveness of various tumour cell types, but its role in prostate cancer remained to be investigated. We report here that downregulation of PTPL1 by small interfering RNA in PC3 cells decreases cell proliferation and concomitantly reduces the expression of cell cycle-related proteins such as cyclins E and B1, PCNA, PTTG1 and phospho-histone H3. PTPL1 downregulation also increases the invasion ability of PC3 cells through Matrigel coated membranes. cDNA array of PTPL1-silenced PC3 cells versus control cells showed an upregulation of invasion-related genes such as uPA, uPAR, tPA, PAI-1, integrin α6 and osteopontin. This increased expression was also confirmed in PTPL1-silenced DU145 prostate cancer cells by quantitative real time PCR and western blot. These findings suggest that PTPL1 is an important mediator of central cellular processes such as proliferation and invasion.
Subject(s)
Cell Cycle , Gene Expression Regulation, Neoplastic , Prostatic Neoplasms/genetics , Prostatic Neoplasms/pathology , Protein Tyrosine Phosphatase, Non-Receptor Type 13/metabolism , Blotting, Western , Cell Cycle/drug effects , Cell Cycle Proteins/genetics , Cell Proliferation/drug effects , Down-Regulation/drug effects , Gene Expression Regulation, Enzymologic , Humans , Integrin alpha6/genetics , Integrin alpha6/metabolism , Male , Neoplasm Invasiveness/genetics , Osteopontin/genetics , Osteopontin/metabolism , Phenotype , Plasminogen Activator Inhibitor 1/genetics , Plasminogen Activator Inhibitor 1/metabolism , Prostatic Neoplasms/enzymology , RNA, Small Interfering/pharmacology , Real-Time Polymerase Chain Reaction , Receptors, Urokinase Plasminogen Activator/genetics , Receptors, Urokinase Plasminogen Activator/metabolism , Tissue Plasminogen Activator/genetics , Tissue Plasminogen Activator/metabolism , Tumor Cells, Cultured , Up-Regulation/drug effects , Urokinase-Type Plasminogen Activator/genetics , Urokinase-Type Plasminogen Activator/metabolismABSTRACT
OBJECTIVES: To investigate the expression of Hsp60 protein in prostate cancer biopsy samples, and its association with prognostic clinical parameters and hormone resistance and survival. Molecular chaperones are involved in protein folding, protein degradation, and protein trafficking among subcellular compartments. METHODS: We selected 107 patients with localized and locally advanced prostate cancer at our hospital from 1999 through 2004. We performed an analysis by western blot and immunohistochemistry on paraffin-embedded tissue sections. Clinical data were used to determine associations between immunohistochemical expression of Hsp60 and tumor behavior. RESULTS: The expression level of Hsp60 was significantly increased in tumors with high Gleason score (P < .001). Hsp60 expression was also significantly associated with initial serum PSA levels (P < .01) and with the presence of lymph node metastasis (P < .003). In 50 locally advanced cancers treated by androgen ablation we found an association between high Hsp60-expressing tumors and an early onset of hormone refractory disease (P < .02) and reduced cancer-specific survival (P < .05). CONCLUSIONS: Hsp60 protein is overexpressed in poorly differentiated prostate cancers. Hsp60 expression is strongly associated with prognostic clinical parameters, such as Gleason score, initial serum PSA levels, and lymph node metastasis and with the onset of hormone-refractory disease and reduced cancer-specific survival. Identification of such markers could be of relevance in the clinical management of prostate cancer.
Subject(s)
Adenocarcinoma/chemistry , Antineoplastic Agents, Hormonal/therapeutic use , Biomarkers, Tumor/analysis , Chaperonin 60/analysis , Drug Resistance, Neoplasm , Neoplasm Proteins/analysis , Prostatic Neoplasms/chemistry , Adenocarcinoma/blood , Adenocarcinoma/drug therapy , Adenocarcinoma/pathology , Androgens , Antineoplastic Agents, Hormonal/pharmacology , Cell Differentiation , Disease Progression , Gene Expression Regulation, Neoplastic , Humans , Kaplan-Meier Estimate , Lymphatic Metastasis , Male , Neoplasms, Hormone-Dependent/chemistry , Neoplasms, Hormone-Dependent/drug therapy , Neoplasms, Hormone-Dependent/pathology , Proportional Hazards Models , Prostate-Specific Antigen/blood , Prostatic Neoplasms/blood , Prostatic Neoplasms/drug therapy , Prostatic Neoplasms/pathology , Survival AnalysisABSTRACT
Androgen-sensitive prostate cancer cells turn androgen resistant through complex mechanisms that involve dysregulation of apoptosis. We investigated the role of antiapoptotic Bcl-xL in the progression of prostate cancer as well as the interactions of Bcl-xL with proapoptotic Bax and Bak in androgen-dependent and -independent prostate cancer cells. Immunohistochemical analysis was used to study the expression of Bcl-xL in a series of 139 prostate carcinomas and its association with Gleason grade and time to hormone resistance. Expression of Bcl-xL was more abundant in prostate carcinomas of higher Gleason grades and significantly associated with the onset of hormone-refractory disease. In vivo interactions of Bcl-xL with Bax or Bak in untreated and camptothecin-treated LNCaP and PC3 cells were investigated by means of coimmunoprecipitation. In the absence of any stimuli, Bcl-xL interacts with Bax and Bak in androgen-independent PC3 cells but only with Bak in androgen-dependent LNCaP cells. Interactions of Bcl-xL with Bax and Bak were also evidenced in lysates from high-grade prostate cancer tissues. In LNCaP cells treated with camptothecin, an inhibitor of topoisomerase I, the interaction between Bcl-xL and Bak was absent after 36 h, Bcl-xL decreased gradually and Bak increased coincidentally with the progress of apoptosis. These results support a model in which Bcl-xL would exert an inhibitory effect over Bak via heterodimerization. We propose that these interactions may provide mechanisms for suppressing the activity of proapoptotic Bax and Bak in prostate cancer cells and that Bcl-xL expression contributes to androgen resistance and progression of prostate cancer.
