Dissecting the functional differences and clinical features of R-spondin family members in metastatic prostate cancer

This study investigates the R-spondin family of genes (RSPO1/2/3/4), a group of secreted proteins that act as Wnt regulators, and their subsequent role in advanced prostate cancer (PC). When evaluating transcriptomic data from primary and metastatic PC patients, we found that alterations in RSPO2 were more prevalent than in other RSPO family members or Wnt-regulating genes APC and CTNNB1. Further, we found that RSPO2 alterations in PCs were significantly associated with worse disease-free survival. Through our in silico modeling, RSPO2 exhibited strong positive associations with genes regulating epithelial-mesenchymal transition (EMT) and double-negative prostate cancer (DNPC), but had negative correlations with androgen receptor (AR) and AR-associated genes. Furthermore, 3D modeling of RSPO2 revealed structural differences between itself and other RSPOs. In cell lines, RSPO2 overexpression caused up-regulation of EMT pathways, including EMT-regulatory transcription factors ZEB1 and TWIST2. Conversely, this was not observed when CTNNB1 was overexpressed in the same models. These findings highlight that, in PC, RSPO2 functions as a unique member of the R-spondin family by promoting genes and signaling pathways associated with aggressive PC and RSPO2 amplifications are associated with poor outcomes in PC patients.