The LRP4/YAP axis drives the radiation-tolerant persister (RTP) cell state in breast cancer.

Breast cancer recurrences and treatment failures can be attributed to intra-tumoral heterogeneity (ITH), which is characterize by the coexistence of diverse cellular states, including cancer stem cells (CSCs), within a single tumor.Recent insights suggest that ITH arises from non-genetic dynamics, enabling tumors to adapt and evolve into a therapy-tolerant state under treatment pressure. The aim of this work is to decipher the origin of persistent radiation tolerant cells (RTP) in breast tumors and to understand their mechanisms in order to find new strategies to avoid radiation resistance. To this aim,we developed a lineage tracing system and engineeredvarious breast cancer cell lines and patient-derived xenografts totracked radiation-induced cell plasticity. We combined lineage tracing with a unique RNAi screen under irradiation to identify and functionally validate the regulators of radio-induced cell plasticity. We discovered that RTP cells, which possess CSC properties, emerge from radiotherapy-induced reprogramming of non-CSCs. From the combinatorial approach of the lineage tracing and the RNAi screen under irradiation, we then identified and functionally validated the LRP4/YAP axis as a crucial regulator of radio-induced cell plasticity. We further demonstrate that overexpression of LRP4 is common in residual disease post-treatment and is associated with breast tumors of poor prognosis. This work has demonstrated that the LRP4/YAP axis drives radioresistance by promoting the emergence of RTP cells through radiation-induced plasticity, and that modulation of the LRP4/YAP axis is a promising strategy for sensitizing breast cancers to radiotherapy, opening up a new avenue for improving patient outcomes.