Simmler, P. | bioRxiv Science

bioRxiv2022

Mutant SF3B1 promotes PDAC malignancy through TGF-β resistance

The splicing factor SF3B1 is recurrently mutated in various tumors, including pancreatic ductal adenocarcinoma (PDAC). The impact of the hotspot mutation SF3B1K700E on the PDAC pathogenesis, however, remains elusive. Here, we demonstrate that Sf3b1K700E alone is insufficient to induce malignant transformation of the murine pancreas, but increases aggressiveness of PDAC if it co-occurs together with mutated KRAS and p53. We further demonstrate that SF3B1K700E reduces epithelial-mesenchymal transition (EMT) and confers resistance to TGF-{beta}1-induced cell death, and provide evidence that this phenotype is in part mediated through aberrant splicing of Map3k7. Taken together, our work suggests that SF3B1K700E acts as an oncogenic driver in PDAC through enhancing resistance to the tumor suppressive effects of TGF-{beta}.

cancer biology↗

bioRxiv2020

SF3B1 promotes tumor malignancy through splicing-independent co-activation of HIF1α

Mutations in the splicing factor SF3B1 are frequently occurring in various cancers and drive tumor progression through the activation of cryptic splice sites in multiple genes. Recent studies also demonstrate a positive correlation between expression levels of wildtype SF3B1 and tumor malignancy, but underlying mechanisms remain elusive. Here, we report that SF3B1 acts as an activator of HIF signaling through a splicing-independent mechanism. We demonstrate that SF3B1 forms a heterotrimer with HIF1 and HIF1{beta}, facilitating binding of the HIF1 complex to hypoxia response elements (HREs) to activate target gene expression. We further validate the relevance of this mechanism for tumor progression. Monoallelic deletion of Sf3b1 impedes formation and progression of hypoxic pancreatic cancer via impaired HIF signaling, but is well tolerated in normoxic chromophobe renal cell carcinoma. Our work uncovers an essential role of SF3B1 in HIF1 signaling, providing a causal link between high SF3B1 expression and aggressiveness of solid tumors.

cell biology↗