title: RAB27A, RAB27B and VPS36 are downregulated in advanced prostate cancer and show functional relevance in prostate cancer cells.
abstract: Paracrine and long-range signaling via extracellular vesicles, such as exosomes and microvesicles, is deemed crucial for tumorigenesis, invasion and spread of solid tumors. The ESCRT machinery (endosomal sorting complexes required for transport) and Rab-proteins act as key players in vesicular trafficking and secretion. Yet, their role in prostate cancer (PCa) is unknown. Therefore, this study aimed to elucidate the relevance of these components in PCa. In silico reanalysis of genes with known involvement in vesicular trafficking and secretion in an existing microarray dataset revealed low expression of RAB27A, RAB27B and VPS36 to be predictive for reduced BCR-free survival in patients with localized PCa (p=0.033, 0.025 and 0.005). In the same microarray dataset underexpression of RAB27A, RAB27B and VPS36 was seen in distant metastases (p<0.001; p=0.003; p<0.001). This was consistent in two further microarray datasets. qRT-PCR-validation in two independent cohorts of PCa specimens (n=90) showed low expression of VPS36 in PCa tissue (p=0.023), especially in castration-resistant tumors (p=0.002). In all five datasets there were significant correlations between the expression of at least two of the candidates. Upon knockdown of VPS36 an increase of RAB27A and RAB27B expression, but not vice versa, was observed in both prostate and breast cancer cells (PC3, MDA-MB‑231). In PC3 cell knockdown of RAB27B and VPS36 dramatically reduced colony formation (-52.2%, p<0.001; -71.1%, p<0.001) and, controversial to reports in other tumor entities, increased the release of extracellular particles (+25.3%, p=0.014; +45.6%, p<0.001). Taken together RAB27A, RAB27B and VPS36 are frequently underexpressed in advanced PCa and are inversely correlated with PCa outcome. There seems to be a close relationship in the expression of RAB27A, RAB27B and VPS36, with RAB27A and RAB27B being dependent on VPS36. Changes in colony formation and particle release upon RNAi indicate an involvement in paracrine cell-cell communication.
authors.affiliation: Department of Urology, Mannheim Medical Center, University of Heidelberg, D-68167 Mannheim, Germany.
authors.forename: Thomas Stefan
authors.initials: TS
authors.lastname: Worst
authors.affiliation: Department of Urology, Mannheim Medical Center, University of Heidelberg, D-68167 Mannheim, Germany.
authors.forename: Yannic
authors.initials: Y
authors.lastname: Meyer
authors.affiliation: Institute of Pathology, Mannheim Medical Center, University of Heidelberg, D-68167 Mannheim, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Gottschalt
authors.affiliation: Institute of Pathology, Mannheim Medical Center, University of Heidelberg, D-68167 Mannheim, Germany.
authors.forename: Cleo-Aron
authors.initials: CA
authors.lastname: Weis
authors.affiliation: Department of Urology, Mannheim Medical Center, University of Heidelberg, D-68167 Mannheim, Germany.
authors.forename: Jost
authors.initials: J
authors.lastname: von Hardenberg
authors.affiliation: Department of Urology, Mannheim Medical Center, University of Heidelberg, D-68167 Mannheim, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Frank
authors.affiliation: Department of Urology, Mannheim Medical Center, University of Heidelberg, D-68167 Mannheim, Germany.
authors.forename: Annette
authors.initials: A
authors.lastname: Steidler
authors.affiliation: Department of Urology, Mannheim Medical Center, University of Heidelberg, D-68167 Mannheim, Germany.
authors.forename: Maurice Stephan
authors.initials: MS
authors.lastname: Michel
authors.affiliation: Department of Urology, Mannheim Medical Center, University of Heidelberg, D-68167 Mannheim, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Erben
mesh_terms: D014408:Biomarkers, Tumor / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000235:genetics; D015536:Down-Regulation; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000235:genetics / Q000473:pathology*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000075745:rab27 GTP-Binding Proteins
chemical_list: D014408:Biomarkers, Tumor; D056827:Endosomal Sorting Complexes Required for Transport; D034741:RNA, Small Interfering; C516152:VPS36 protein, human; D000075745:rab27 GTP-Binding Proteins; C066694:RAB27A protein, human; C512960:Rab27B protein, human; D020691:rab GTP-Binding Proteins