Dutton, L. | bioRxiv Science

bioRxiv2025

Radiotherapy drives lung metastasis in PDAC via a RhoGTPasesignaling shift towards MRCK-dependency

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with an extremely poor prognosis, partly owing to its highly metastatic nature. Although radiotherapy is an effective and potentially curative treatment modality, research over the last few decades has indicated that it may induce a more metastatic phenotype in surviving cancer cells. We demonstrate for the first time that clinically relevant doses of image-guided targeted radiotherapy induce metastasis in a genetically engineered KPC mouse model of PDAC. Furthermore, this induction is largely driven by an organotropic switch towards lung metastasis. Using an in vitro RNAi screening approach, we identified a key role for myotonic dystrophy-related Cdc42-binding kinase (MRCK) in driving this response. MRCK activity was spatially upregulated at the plasma membrane in response to radiotherapy in PDAC cell lines as well as at the invasive margins of PDAC tumors. This upregulation of activity was maintained in metastases, suggesting an important role for MRCK in not only triggering local invasion in response to radiotherapy but also promoting distant metastases. Importantly, inhibition of MRCK with a small-molecule inhibitor (BDP9066) specifically opposed radiation-driven MRCK upregulation and pro-metastatic response.

cancer biology↗

bioRxiv2025

Identification of a novel GREMLIN1 uptake pathway in epithelial cells that requires BMP binding

Gremlin1 is a member of a cysteine-knot containing family of secreted antagonists of bone morphogenetic protein signaling. GREM1 binding to BMP targets prevents their engagement with cognate BMP receptors, attenuating BMP-dependent gene expression. Some evidence suggests that GREM1 can directly bind to receptor tyrosine kinases on the plasma membrane, further complicating our understanding of GREM1 biology. To attempt to clarify the modalities of GREM1 signaling, we show that GREM1 protein is produced and secreted by intestinal fibroblasts and endocytosed by neighbouring epithelial cells. GREM1 uptake is a slow process and occurs by both clathrin- and caveolin-mediated endocytosis. Cell membrane heparin sulfate proteoglycans are required for GREM1 binding and uptake, and once internalised, GREM1 appears to localise to the early endosomes. Addition of BMP2 enhanced GREM1 uptake into cells. Remarkably, generation of a BMP-resistant GREM1 mutant abolished GREM1 uptake both in the presence and absence of BMP2. These data suggest that GREM1 binding and uptake into cells requires BMP binding, a process that may contribute to the antagonism of BMP signaling by GREM1. SummaryIn this article, we demonstrate differential GREM1 mRNA versus protein expression in mouse intestine. We also identify a novel GREM1 endocytosis pathway whereby mammalian cells take up GREM1 protein in what appears to be a BMP-dependent mechanism.

cell biology↗