Serine/threonine/tyrosine kinase 1 drives pancreatic carcinogenesis via GSK3β sequestration-mediated Wnt/β-catenin pathway hyperactivation

Abstract

The Wnt/β-catenin pathway is strongly relevant to pancreatic cancer progression, poor prognostic outcomes, and elevated cancer-related mortality. However, the mechanism underlying continuously activated Wnt/β-catenin signaling in pancreatic cancer, a context in which adenomatous polyposis coli (APC) mutations are rarely observed, remains poorly understood. In this study, we investigated the role of STYK1 in regulating canonical Wnt/β-catenin signaling and pancreatic cancer tumorigenesis using the LSL-Kras^G12D; Trp53^R172H/+; Pdx1^Cre mouse model. Our findings demonstrate that STYK1 directly binds to β-catenin and GSK3β, inhibiting GSK3β activity by increasing the level of its kinase-inactive form, which is phosphorylated at S9, and promoting its sequestration into MVBs. We further showed that STYK1-mediated GSK3β sequestration is impaired by autophagy inhibitors or in ATG7 knockout cells, linking this process to autophagic regulation. Structural analysis identified conserved tyrosine-based (Y191QRL194) and dileucine-based (GDLL203-204) sorting motifs in STYK1, which facilitate clathrin/AP2-dependent internalization essential for GSK3β sequestration. The phosphorylation of STYK1 at Y191 by BLK kinase enhances its interaction with AP2, thereby accelerating GSK3β sequestration and subsequent Wnt/β-catenin pathway activation. Notably, inhibitory peptides targeting either the STYK1-β-catenin or the STYK1-GSK3β interface significantly suppressed pancreatic cancer development in vitro and in vivo, underscoring their therapeutic potential. Collectively, these results elucidate a novel STYK1-driven mechanism for Wnt/β-catenin activation in APC-independent pancreatic cancer and provide preclinical evidence for targeting STYK1-mediated signaling as a therapeutic strategy.