Integrin β4 and vinculin contained in exosomes are potential markers for progression of prostate cancer associated with taxane-resistance

Abstract

Abstract. Treatment with taxanes for castration-resistant prostate cancer often leads to the development of resistance. It has been recently demonstrated that exosomes present in the body fluids contain proteins and RNAs in the cells from which they are derived and could serve as a diagnostic marker for various diseases. In the present study, we aimed to identify proteins contained in exosomes that could be markers for progression and taxane-resistance of prostate cancer. Exosomes were isolated by differential centrifugation from the culture medium of taxane-resistant human prostate cancer PC-3 cells (PC-3R) and their parental PC-3 cells. Isolated exosomes were subjected to iTRAQ-based quantitative proteomic analysis. Exosomes were also isolated from the culture medium by using anti-CD9 antibody-conjugated magnetic beads. Protein expression was knocked down by siRNA transfection followed by analysis of the silencing effects. Proteomic analysis showed that integrin β4 (ITGB4) and vinculin (VCL) were upregulated in exosomes derived from PC-3R cells compared to PC-3 cells. The elevation of ITGB4 and VCL was confirmed in exosomes captured by anti-CD9 antibody from the culture medium of PC-3R cells. Silencing of ITGB4 and VCL expression did not affect proliferation and taxane-resistance of PC-3R cells, but ITGB4 knockdown attenuated both cell migration and invasion and VCL knockdown reduced invasion. Our results suggest that ITGB4 and VCL in exosomes could be useful markers for progression of prostate cancer associated with taxane-resistance, providing the basis for development of an exosome-based diagnostic system. IntroductionProstate cancer is one of the most common male cancers and is the second-leading cause of cancer death among men in the United States (1). Most patients with prostate cancer well respond to androgen deprivation therapy, but 10-20% of those develop castration-resistant prostate cancer (CRPC) (2). Taxanes, a class of microtubule-targeting anticancer agents such as paclitaxel and docetaxel, have been administered to CRPC patients and docetaxel is currently used as the first-line chemotherapy (3). Docetaxel therapy demonstrated an overall survival benefit for CRPC patients, but there is a finite amount of time before acquiring resistance (3,4).Development of resistance to anticancer drugs is associated with more malignant and aggressive phenotype and acceleration of tumor growth in various types of cancer including prostate cancer (5-7). Although prostate-specific antigen (PSA) has been commonly used as a marker for tumor growth, there are no clinically useful markers for diagnosing progression and aggressiveness as well as taxane-resistance of prostate cancer. Given that such markers were available, one could select CRPC patients sensitive to docetaxel, avoid administration to drug-resistant patients and also monitor the drug efficacy, minimizing the incidence of adverse effects as well. Furthermore, prediction of progression and prognosis of CRPC patients might be possible.Exosomes are microvesi...

mir-218-2 promotes glioblastomas growth, invasion and drug resistance by targeting CDC27

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Gamma-glutamyltransferase activity in exosomes as a potential marker for prostate cancer

“…More recently identified PC markers include prostate cancer antigen 3 (PCA3) [46], TMPRSS2-ERG fusion gene [47] and their combined use [48]. Although there have been a limited number of reports describing exosomal miRNA as a marker for PC [49], we and others have reported exosomal protein markers that would be helpful to diagnose PC (PSMA), taxane-resistant CRPC (P-gp) and progression and aggressiveness of PC (integrin β4 and vinculin) [12–16]. This is the first report that described serum exosomal GGT1 expression or GGT activity as a potential marker to diagnose PC.…”

“…Proteomic analysis was performed as previously described [16]. In brief, exosomes were labeled with iTRAQ reagents using the iTRAQ multiplex kit (AB Sciex, Foster City, CA, USA).…”

“…We and others have demonstrated that prostate-specific membrane antigen (PSMA) and P-glycoprotein (P-gp) encoded by multi-drug resistance protein 1 (MDR1) expressed on the surface of blood exosomes could be a marker for PC and taxane-resistant CRPC, respectively [12–15]. We have also recently reported the potential of integrin β4 and vinculin in exosomes as markers for progression and aggressiveness of CRPC [16]. …”

Exosomes: A Cancer Theranostics Road Map

“…Serum PSA quantification has been used for 2 decades for early detection of prostate cancer; however, this diagnostic approach is controversial, due to its inability to distinguish between PSA's malignant and benign tumor origin, thus resulting in false-positive results [37] . PSA detection and quantification in exosomes is characterized by higher specificity, when compared to blood PSA measurements, and findings suggest that both approaches can be used in conjunction [38,39] .…”