Increasing evidence demonstrates that Lin28B plays critical roles in numerous biological processes including cell proliferation and stemness maintenance. However, the molecular mechanisms underlying Lin28B nuclear translocation remain poorly understood. Here, we found for the first time that KRAS promoted Lin28B nuclear translocation through PKCβ, which directly bound to and phosphorylated Lin28B at S243. Firstly, we observed that Lin28B was up-regulated in pancreatic cancer, contributing to cellular migration and proliferation. Furthermore, nuclear Lin28B upregulated TET3 mRNA and protein levels by blocking the production of mature let-7i. Subsequently, increased TET3 expression could also promote the expression of Lin28B, thereby forming a Lin28B/let-7i/TET3 feedback loop. Our results suggest that the KRAS/Lin28B axis drives the let-7i/TET3 pathway to maintain the stemness of pancreatic cancer cells. These findings illuminate the distinct mechanism of Lin28B nuclear translocation and its important roles in KRAS-driven pancreatic cancer, and have important implications for development of novel therapeutic strategies for this cancer.
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