High WEE2-AS1 expression in CAF-derived small extracellular vesicles inhibits the Hippo pathway to facilitate colorectal cancer progression via promoting degradation of MOB1A

Background: Cancer-associated fibroblasts (CAFs) are the most abundant stromal components in the tumor microenvironment (TME) and exert a critical effect on regulating tumor initiation and progression. However, the precise biological functions and underlying mechanisms of CAFs in the TME have yet to be understood. Methods: CAFs and normal fibroblasts (NFs) were isolated from paired fresh CRC and adjacent normal tissues. Small extracellular vesicles were extracted from conditioned medium and plasma by ultracentrifugation or ExoQuick kit. The biological functions of CAF-sEVsWEE2-AS1 were investigated by a series of experiments: CCK8, colony formation, flow cytometric assay, mouse xenograft, AOM/DSS-induced colitis-associated colon cancer, etc. The mechanisms of WEE2-AS1 were demonstrated by luciferase assay, RNA pull-down, etc.Results: We demonstrate that WEE2-AS1 is highly expressed in the CAF-derived small extracellular vesicles (sEVs). Moreover, WEE2-AS1 is markedly higher in plasma sEVs of CRC patients than in healthy subjects and its high level predicts advanced pathological staging and poor survival. Then, we conducted a series of in vitro and in vivo experiments. Elevated expression of WEE2-AS1 in sEVs increases CRC cell proliferation in vitro. Importantly, aberrant CAF-sEVsWEE2-AS1 leads to tumor formation and progression in BALB/c nude mice and promotes AOM/DSS-induced tumorigenesis. Mechanistically, WEE2-AS1 functions as a modular scaffold for the MOB1A and E3 ubiquitin-protein ligase praja2, leading to MOB1A degradation via the ubiquitin-proteasome pathway. Thus, the Hippo pathway is inhibited and more YAP are transported into the nucleus, where they activate downstream gene transcription. Conclusions: CAF-sEVsWEE2-AS1 interacts with MOB1A, promotes degradation of MOB1A, inhibits the Hippo pathway, and facilitates the growth of CRC cells. Hence, WEE2-AS1 may be a promising therapeutic target and circulating biomarker for CRC diagnosis and prognosis.