Cell-Type-Specific Signalling Networks Impacted by Prostate Epithelial-Stromal Intercellular Communication

SIMPLE SUMMARY: Prostate cancer is the most commonly diagnosed cancer in men and one of the leading causes of cancer-related death. Intercellular communication between prostate epithelial cells and cells within the tumour microenvironment (TME), particularly cancer-associated fibroblasts (CAFs), are known to contribute to prostate cancer development and progression. However, the signalling mechanisms by which these reciprocal interactions occur are unknown. The aim of our study was to investigate the cell-type-specific signalling networks initiated by intercellular communication between prostate epithelial cells and patient-derived CAFs when grown together. We identified significant differences in the proteomic profiles of both cell types in this experimental setting. Functional analysis revealed that one of the top upregulated epithelial proteins following co-culture, transglutaminase-2 (TGM2), promotes epithelial cell migration and proliferation under co-culture conditions. This study identifies novel signalling pathways involved in intercellular communication in prostate cancer that may be exploited to improve management of this malignancy. ABSTRACT: Prostate cancer is the second most common cause of cancer death in males. A greater understanding of cell signalling events that occur within the prostate cancer tumour microenvironment (TME), for example, between cancer-associated fibroblasts (CAFs) and prostate epithelial or cancer cells, may identify novel biomarkers and more effective therapeutic strategies for this disease. To address this, we used cell-type-specific labelling with amino acid precursors (CTAP) to define cell-type-specific (phospho)proteomic changes that occur when prostate epithelial cells are co-cultured with normal patient-derived prostate fibroblasts (NPFs) versus matched CAFs. We report significant differences in the response of BPH-1 benign prostate epithelial cells to CAF versus NPF co-culture. Pathway analysis of proteomic changes identified significant upregulation of focal adhesion and cytoskeleton networks, and downregulation of metabolism pathways, in BPH-1 cells cultured with CAFs. In addition, co-cultured CAFs exhibited alterations in stress, DNA damage, and cytoskeletal networks. Functional validation of one of the top differentially-regulated proteins in BPH-1 cells upon CAF co-culture, transglutaminase-2 (TGM2), demonstrated that knockdown of this protein significantly reduced the proliferation and migration of prostate epithelial cells. Overall, this study provides novel insights into intercellular communication in the prostate cancer TME that may be exploited to improve patient management.