Background Cabazitaxel (CBZ) is now widely used for prostate cancer (PC) patients resistant to docetaxel (DOC), however, most patients eventually acquire resistance. It will, therefore, be of great benefit to discover novel therapeutic target for the resistance. We aimed to identify candidate therapeutic targets for CBZ‐resistance by proteomic analysis of extracellular vesicles (EVs) isolated from serum of DOC‐resistant PC patients who later developed CBZ‐resistance as well as those harvested from culture medium of DOC‐ and CBZ‐resistant PC cell lines. Methods Using T‐cell immunoglobulin domain and mucin domain‐containing protein 4 (Tim4) conjugated to magnetic beads, EVs were purified from serum of PC patients with DOC‐resistance that was collected before and after acquiring CBZ‐resistance and conditioned medium of DOC‐resistant (22Rv1DR) and CBZ‐resistant (22Rv1CR) PC cell lines. Protein analysis of EVs was performed by nanoLC‐MS/MS, followed by a comparative analysis of protein expression and network analysis. The cytotoxic effect of a phosphatidylinositol‐3‐kinase (PI3K) inhibitor, ZSTK474, was evaluated by WST‐1 assay. The expression and phosphorylation of PI3K and PTEN were examined by western blot analysis. Results Among differentially regulated proteins, 77 and 61 proteins were significantly increased in EVs from CBZ‐resistant PC cell line and patients, respectively. A comparison between the two datasets revealed that six proteins, fructose‐bisphosphate aldolase, cytosolic nonspecific dipeptidase, CD63, CD151, myosin light chain 9, and peroxiredoxin‐6 were elevated in EVs from both cell line and patients. Network analysis of the increased EV proteins identified pathways associated with CBZ‐resistance including PI3K signaling pathway. ZSTK474 significantly inhibited growth of 22Rv1CR cells and improved their sensitivity to CBZ. In 22Rv1CR cells, PI3K was activated and PTEN that inhibits PI3K was deactivated. Conclusions Proteomic analysis of serum EVs was successfully accomplished by using Tim‐4 as a tool to isolate highly purified EVs. Our results suggest that the combination use of CBZ and PI3K inhibitor could be a promising treatment option for CBZ‐resistant PC patients.

Background: The aim of this study was to compare the surgical and oncological outcomes and complications of laparoscopic radical cystectomy (LRC) to those of open radical cystectomy (ORC) in patients with muscle-invasive bladder cancer (MIBC). Methods: Our study focused on patients with histologically confirmed stage T2-T4a urothelial carcinoma of the bladder without distant metastases, who underwent LRC (LRC group) or ORC (ORC group). The primary endpoints in this study were the overall survival (OS) and recurrencefree survival (RFS) rates. Results: In this study, 59 patients, 17 underwent LRC and 42 underwent ORC, were enrolled. The 2-year OS rate was 100% in the LRC group and 88.0% in the ORC group (p = 0.85). The 2-year RFS rate was 63.5% in the LRC group and 69.5% in the ORC group (p = 0.321). On multivariate analysis, the histological type, positive lymph node, and positive resection margin were significantly associated with the OS rates. Conclusions: This study suggested that LRC may achieve similar oncological outcomes and fewer perioperative complications and less blood loss compared to ORC. Therefore, LRC should be considered as one of the treatment options for patients with MIBC.

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