Stromal NRG1 in luminal breast cancer defines pro-fibrotic and migratory cancer-associated fibroblasts
Mireia Berdiel‐Acer, Ana Maia, Zhivka Hristova, Simone Borgoni, Martina Vetter, Sara Burmester, Corinna Becki, Birgitta E. Michels, Khalid Abnaof, Ilona Binenbaum, Daniel Bethmann, Aristotelis Chatziioannou, Max Hasmann, Christoph Thomssen, Elisa Espinet, Stefan Wiemann
Abstract
HER3 is highly expressed in luminal breast cancer subtypes. Its activation by NRG1 promotes activation of AKT and ERK1/2, contributing to tumour progression and therapy resistance. HER3-targeting agents that block this activation, are currently under phase 1/2 clinical studies, and although they have shown favorable tolerability, their activity as a single agent has proven to be limited. Here we show that phosphorylation and activation of HER3 in luminal breast cancer cells occurs in a paracrine manner and is mediated by NRG1 expressed by cancer-associated fibroblasts (CAFs). Moreover, we uncover a HER3-independent NRG1 signaling in CAFs that results in the induction of a strong migratory and pro-fibrotic phenotype, describing a subtype of CAFs with elevated expression of NRG1 and an associated transcriptomic profile that determines their functional properties. Finally, we identified Hyaluronan Synthase 2 (HAS2), a targetable molecule strongly correlated with NRG1, as an attractive player supporting NRG1 signaling in CAFs.