Expression, localisation and potential significance of aquaporins in benign and malignant human prostate tissue

Johannes Bründl,Sabine Wallinger,Bernd Rosenhammer,Maximilian Burger,Nikolaos Theodoros Georgopoulos,Johannes Breyer,Wolfgang Otto,Florian Weber,Peter Rubenwolf,Matthias Evert

doi:10.1186/s12894-018-0391-y

Abstract

BackgroundTo study the expression pattern, localisation and potential clinical significance of aquaporin water channels (AQP) both in prostate cancer (PC) cell lines and in benign and malignant human prostate tissue.MethodsThe AQP transcript and protein expression of HPrEC, LNCaP, DU-145 and PC3 cell lines was investigated using reverse transcriptase polymerase chain reaction (RT-PCR) and immunofluorescence (IF) microscopy labelling. Immunohistochemistry (IHC) was performed to assess AQP protein expression in surgical specimens of benign prostatic hyperplasia as well as in PC. Tissue mRNA expression of AQPs was quantified by single-step reverse transcriptase quantitative polymerase chain reaction (qPCR). Relative gene expression was determined using the 40-ΔCT method and correlated to clinicopathological parameters.ResultsTranscripts of AQP 1, 3, 4, 7, 8, 10 and 11 were expressed in all four cell lines, while AQP 9 transcripts were not detected in malignant cell lines. IF microscopy confirmed AQP 3, 4, 5, 7 and 9 protein expression. IHC revealed highly heterogeneous AQP 3 protein expression in PC specimens, with a marked decrease in expression in tumours of increasing malignancy. Loss of AQP 9 was shown in PC specimens. mRNA expression of AQP3 was found to be negatively correlated to PSA levels (ρ = − 0.354; p = 0.013), D’Amico risk stratification (ρ = − 0.336; p = 0.012), ISUP grade (ρ = − 0.321; p = 0.017) and Gleason score (ρ = − 0.342; p = 0.011).ConclusionsThis is the first study to systematically characterize human prostate cell lines, benign prostatic hyperplasia and PC in relation to all 13 members of the AQP family. Our results indicate the differential expression of several AQPs in benign and malignant prostate tissue. A significant correlation was observed between AQP 3 expression and tumour grade, with progressive loss in more malignant tumours. Taken together, AQPs may play a role in the progression of PC and AQP expression patterns may serve as a prognostic marker.

Highlights

To study the expression pattern, localisation and potential clinical significance of aquaporin water channels (AQP) both in prostate cancer (PC) cell lines and in benign and malignant human prostate tissue
AQP expression by human prostate cell cultures in vitro AQP gene expression was investigated by reverse transcriptase polymerase chain reaction (RT-PCR) and immunofluorescence microscopy
AQP 5 Messenger ribonucleic acid (mRNA) transcripts were detected in the DU-145 and PC3 cancer cell lines, but not in LNCaP or human prostate epithelial cells (HPrEC) cells

Summary

Introduction

To study the expression pattern, localisation and potential clinical significance of aquaporin water channels (AQP) both in prostate cancer (PC) cell lines and in benign and malignant human prostate tissue. AQPs are a family of transmembrane pore-forming proteins that selectively allow water and other small, uncharged molecules such as urea, glycerol and pyrimidines to pass along hydrostatic and osmotic gradients. They play a fundamental role in numerous physiological processes, most notably in fluid absorption and secretion. There is strong presumptive evidence that AQPs play a role in carcinogenesis, in tumour angiogenesis and cell migration [3]

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