Latrophilin-1 and latrophilin-2 as androgen receptor-responsive G protein-coupled receptors promote bladder cancer progression.

Abstract

Objectives: To investigate the functional role of latrophilin-1 (LPHN1; encoded by the ADGRL1 gene) and latrophilin-2 (LPHN2; encoded by the ADGRL2 gene), members of the G protein-coupled receptor family, in relation to androgen receptor (AR) signaling, in the outgrowth of bladder cancer.

Methods: Human bladder urothelial carcinoma cell lines were subjected to real-time PCR, western blotting, chromatin immunoprecipitation, MTT assay, and wound-healing assay. Immunostaining was also performed on a set of bladder cancer tissue microarrays consisting of transurethral resection specimens.

Results: In bladder cancer cells with endogenous or exogenous AR expression, dihydrotestosterone markedly up-regulated ADGRL1/LPHN1 and ADGRL2/LPHN2 expression. Chromatin immunoprecipitation confirmed AR binding to the promoter regions of ADGRL1 and ADGRL2. Additionally, LPHN ligands (e.g. α-latrotoxin, FLRT3) induced their expression. Knockdown of LPHN1 or LPHN2 via shRNA virus infection significantly reduced cell viability and migration, while the stimulatory effects of LPHN ligands on cell viability were more significant in AR-negative or AR-knockdown lines than in corresponding AR-positive lines. Immunohistochemical analysis in surgical specimens further showed that LPHN1 overexpression (i.e. moderate/strong) in muscle-invasive tumors (n = 62) independently predicted poorer disease-specific survival following radical cystectomy (hazard ratio 2.662, P = 0.031). Analysis of The Cancer Genome Atlas (TCGA) dataset (n = 305, stage II-IV bladder cancer) also revealed that high ADGRL2 expression was associated with significantly worse overall survival.

Conclusion: These findings suggest that LPHN1 and LPHN2 function as downstream effectors of AR and contribute to the progression of bladder cancer.