Frizzled 6 Drives EMT and Stromal Remodeling Downstream of SP1 in Basal-like Pancreatic Cancer

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy, in part due to its rapid progression and early metastasis. To uncover novel drivers of this aggressive behavior, we first analyzed Frizzled receptor expression in human PDAC datasets and identified Frizzled 6 (FZD6) as uniquely predictive of poor clinical outcomes among all ten Frizzled family members. High FZD6 expression correlated with significantly worse overall survival for PDAC patients of any age. Functional studies in human PDAC cell lines showed that FZD6 promotes mesenchymal phenotypes, including enhanced migration and growth in 3D culture, while FZD6 loss induces E-cadherin expression and impairs motility without affecting 2D proliferation. In vivo, conditional epithelial deletion of Fzd6 in KPC mice significantly extended survival, reduced tumor burden and metastasis, and remodeled the tumor microenvironment to suppress stromal activation. Single-cell RNA sequencing analysis of human and mouse PDAC tumors confirms that FZD6 is primarily found within the tumor cells and FZD6-activating, noncanonical Wnt ligands are found to be produced by the cancer-associated fibroblasts surrounding the tumors. Mechanistically, we found that FZD6 is a transcriptional target of specificity protein 1 (SP1), a factor upregulated in mutant p53 contexts and within basal-like PDAC subtypes. SP1 knockdown reduced FZD6 expression and signaling through the PCP pathway. Furthermore, reduced SP1 impaired cell motility. Together this implicates the SP1-Fzd6-Wnt/PCP axis as a key driver of epithelial plasticity and disease progression. These findings suggest that FZD6 is a central effector of mutant p53-driven EMT, and a promising therapeutic target in metastatic PDAC.