Friedman-DeLuca, M. | Search bioRxiv

bioRxiv2026

Metastatic dissemination of breast cancer stem cells requires MenaINV for lung extravasation but not survival

Cancer stemness is a pivotal driver of tumor initiation, treatment resistance, and tumor cell survival. Cancer stem cells (CSCs), though constituting only a small fraction of primary tumor cells, are progressively enriched during metastatic progression: from circulating tumor cells traveling in the bloodstream, to disseminated tumor cells lodged in the lung vasculature, to extravasated tumor cells that have entered tissue parenchyma. However, whether CSCs have an intrinsic advantage for extravasation over cancer non-stem cells (CnSCs), or simply their increased representation in circulation renders them more likely to extravasate, remains unresolved. MenaINV, an invasive isoform of the actin regulatory protein Mena, promotes tumor cell transendothelial migration in primary and secondary sites, yet the direct mechanistic link between stemness and MenaINV in lung metastasis remains unresolved. Here, using a validated fluorescent stemness reporter (SORE6) to identify CSCs, we found that CSCs display elevated MenaINV expression relative to CnSCs. High-resolution intravital imaging showed that CSCs extravasate efficiently into lung parenchyma and survive at higher levels, robustly forming metastatic lesions, while CnSCs show limited extravasation, low survival, and poor colonization. Mechanistically, MenaINV disruption in CSCs specifically impaired extravasation without affecting survival, demonstrating that MenaINV is the key extravasation effector downstream of stemness, whereas stemness-associated factors independently confer survival advantages. Moreover, reintroduction of MenaINV in CnSCs restores their extravasation ability upon which extravasated CnSCs reactivate stem program and form metastases. Overall, we discovered a hierarchical framework where stemness regulates both survival and extravasation capacity, with MenaINV as the key CSC extravasation effector. Significance: This study reveals how breast cancer stem cells achieve metastatic dominance through separable pathways: MenaINV-dependent extravasation and MenaINV-independent survival, providing rationale for targeting stem program to improve patient outcome.

cancer biology↗

bioRxiv2025

Paclitaxel causes de novo induction of invasive breast cancer cells by repolarizing tumor-associated macrophages

Metastasis is the leading cause of breast cancer death, and tumor cells must migrate and invade to metastasize. Breast cancer cells that express the pro-metastatic actin regulatory protein MenaINV have an enhanced ability to migrate and intravasate within the primary tumor and extravasate at secondary sites. Though chemotherapy improves patient survival, treatment with paclitaxel leads to upregulation of MenaINV and an increase in metastasis in mice. MenaINV expression can be induced in breast cancer cells through cooperative NF-{kappa}B/ Notch1 signaling with macrophages, which are often increased in tumors in response to chemotherapy. MenaINV-expressing cells are also resistant to paclitaxel, raising the question of whether paclitaxel increases MenaINV by de novo induction or by selectively killing non-MenaINV-expressing cells. We hypothesized that paclitaxel causes de novo MenaINV induction by increasing macrophage-tumor cell NF-{kappa}B/ Notch1 signaling. Understanding this pro-metastatic effect of chemotherapy is crucial to refining treatment strategies. In this study, we demonstrate that paclitaxel increases MenaINV expression by de novo induction. Mechanistically, paclitaxel induces MenaINV by repolarizing tumor-associated macrophages towards a pro-inflammatory phenotype. These pro-inflammatory macrophages then participate in enhanced NF-{kappa}B/ Notch1 signaling with tumor cells, which leads to MenaINV induction in the tumor cells. These results lay the groundwork for novel microenvironment-based therapies to alleviate the pro-metastatic effects of chemotherapy in breast cancer.

cancer biology↗