BackgroundHormone-refractory prostate cancer remains hindered by inevitable progression of resistance to first-line treatment with docetaxel. Recent studies suggest that phenotypic changes associated with cancer may be transferred from cell-to-cell via microvesicles/exosomes. Here we aimed to investigate phenotypic changes associated with docetaxel-resistance in order to help determine the complexity of this problem and to assess the relevance of secreted exosomes in prostate cancer.Methodology/Principal FindingsDocetaxel-resistant variants of DU145 and 22Rv1 were established and characterised in terms of cross-resistance, morphology, proliferation, motility, invasion, anoikis, colony formation, exosomes secretion their and functional relevance. Preliminary analysis of exosomes from relevant serum specimens was also performed. Acquired docetaxel-resistance conferred cross-resistance to doxorubicin and induced alterations in motility, invasion, proliferation and anchorage-independent growth. Exosomes expelled from DU145 and 22Rv1 docetaxel-resistant variants (DU145RD and 22Rv1RD) conferred docetaxel-resistance to DU145, 22Rv1 and LNCap cells, which may be partly due to exosomal MDR-1/P-gp transfer. Exosomes from prostate cancer patients’ sera induced increased cell proliferation and invasion, compared to exosomes from age-matched controls. Furthermore, exosomes from sera of patients undergoing a course of docetaxel treatment compared to matched exosomes from the same patients prior to commencing docetaxel treatment, when applied to both DU145 and 22Rv1 cells, showed a correlation between cellular response to docetaxel and patients’ response to treatment with docetaxel.Conclusions/SignificanceOur studies indicate the complex and multifaceted nature of docetaxel-resistance in prostate cancer. Furthermore, our in vitro observations and preliminary clinical studies indicate that exosomes may play an important role in prostate cancer, in cell-cell communication, and thus may offer potential as vehicles containing predictive biomarkers and new therapeutic targets.

BackgroundThere is no effective treatment strategy for advanced castration-resistant prostate cancer. Although Docetaxel (Taxotere®) represents the most active chemotherapeutic agent it only gives a modest survival advantage with most patients eventually progressing because of inherent or acquired drug resistance. The aims of this study were to further investigate the mechanisms of resistance to Docetaxel. Three Docetaxel resistant sub-lines were generated and confirmed to be resistant to the apoptotic and anti-proliferative effects of increasing concentrations of Docetaxel.ResultsThe resistant DU-145 R and 22RV1 R had expression of P-glycoprotein and its inhibition with Elacridar partially and totally reversed the resistant phenotype in the two cell lines respectively, which was not seen in the PC-3 resistant sublines. Resistance was also not mediated in the PC-3 cells by cellular senescence or autophagy but multiple changes in pro- and anti-apoptotic genes and proteins were demonstrated. Even though there were lower basal levels of NF-κB activity in the PC-3 D12 cells compared to the Parental PC-3, docetaxel induced higher NF-κB activity and IκB phosphorylation at 3 and 6 hours with only minor changes in the DU-145 cells. Inhibition of NF-κB with the BAY 11-7082 inhibitor reversed the resistance to Docetaxel.ConclusionThis study confirms that multiple mechanisms contribute to Docetaxel resistance and the central transcription factor NF-κB plays an immensely important role in determining docetaxel-resistance which may represent an appropriate therapeutic target.

Purpose:In an effort to additionally determine the global patterns of CpG island hypermethylation in sporadic breast cancer, we searched for aberrant promoter methylation at 10 gene loci in 54 primary breast cancer and 10 breast benign lesions.Experimental Design: Genomic DNA sodium bisulfate converted from benign and malignant tissues was used as template in methyl-specific PCR for BRCA1, p16, ESR1, GSTP1, TR␤1, RAR␤2, HIC1, APC, CCND2, and CDH1 genes.Results: The majority of the breast cancer (85%) showed aberrant methylation in at least 1 of the loci tested with half of them displaying 3 or more methylated genes.The highest frequency of aberrant promoter methylation was found for HIC1 (48%) followed by ESR1 (46%), and CDH1 (39%). Similar methylation frequencies were detected for breast benign lesions with the exception of the CDH1 gene (P ‫؍‬ 0.02). The analysis of methylation distribution indicates a statistically significant association between methylation of the ESR1 promoter, and methylation at CDH1, TR␤1, GSTP1, and CCND2 loci (P < 0.03). Methylated status of the BRCA1 promoter was inversely correlated with methylation at the RAR␤2 locus (P < 0.03).Conclusions: Our results suggest a nonrandom distribution for promoter hypermethylation in sporadic breast cancer, with tumor subsets characterized by aberrant methylation of specific cancer-related genes. These breast cancer subgroups may represent separate biological entities with potential differences in sensitivity to therapy, occurrence of metastasis, and overall prognosis.

CpG island hypermethylation is emerging as one of the main mechanisms for inactivation of cancer related genes in breast tumorigenesis. We examined the changes in methylation patterns during ductal breast cancer progression from atypical ductal hyperplasia to in situ and invasive carcinoma. Paired samples of synchronous pre invasive lesions (Atypical Ductal Hyperplasia and/or Ductal Carcinoma in situ) and invasive ductal breast carcinoma from 31 patients, together with isolated lesions from additional 24 patients were studied. Overall, 95 pathological samples and 20 normal breast tissues were analyzed by Quantitative Methylation Specific PCR (QMSP) on a panel of 9 gene promoters (ESR1, APC, CDH1, CTNNB1, GSTPI, THBS1, MGMT, TMS1 and TIMP3). APC, CDH1, and CTNNB1 promoter regions showed an increase in frequency of methylation and increased methylation levels in pathological samples when compared with normal breast tissues. The analysis of the syncronous paired breast lesions demonstrated also an increase in methylation frequency and level for APC, CDH1, and CTNNB1 genes during progression. By establishing a cutoff value, we were able to distinguish among -invasive and invasive lesions. Synchronous methylation of APC, CDH1, and CTNNB1 was associated only with invasive lesions, whereas simultaneous methylation of APC and CDH1 or APC and CTNNB1 were more frequent in ductal carcinoma in situ and invasive carcinoma. Our data point to direct involvement of APC, CDH1, and CTNNB1 CpG island promoter methylation in the early stages of breast cancer progression, and suggest that these molecular alterations might be involved in the transition to an invasive phenotype.