YAP acts as an independent prognostic marker and regulates growth and metastasis of gastrointestinal stromal tumors via FBXW7-YAP pathway.

BACKGROUND: Although imatinib (IM) and subsequent tyrosine kinase inhibitors (TKIs) significantly improve the prognosis of GIST patients by delaying metastasis and recurrence, most patients experience limited efficacy due to toxicity and secondary resistance. We evaluated Yes-associated protein (YAP), a coactivator of the Hippo pathway accounting for IM resistance and aggressive GIST phenotypes, in GISTs. The degradation of YAP is mediated by FBXW7, and FBXW7 predicts recurrence and IM efficacy for GIST patients. Here, we aimed to identify the potential of YAP as a prognostic marker for patients with GISTs, and the molecular mechanism of FBXW7-YAP pathway in GIST cells.

METHODS: We measured YAP expression in 167 GIST cases using immunohistochemical staining, correlated its expression levels with clinicopathological features, and the molecular mechanism underlying the FBXW7-YAP pathway was further examined in vitro and in vivo.

RESULTS: Compared to 80 (47.9%) cases in the low YAP expression group, 87 (52.1%) cases with high YAP expression associated with a poorer prognosis in terms of overall survival (P = 0.004) and recurrence-free survival (P = 0.003). YAP expression was identified as a significant independent factor affecting the 5-year overall survival (P = 0.005) and recurrence-free survival rates (P = 0.007). Moreover, YAP was directly targeted by FBXW7 to affect proliferation, invasion, and migration in GIST cells. High YAP expression correlated with FBXW7 deficiency, as shown in xenograft and metastasis mouse models.

CONCLUSIONS: YAP expression serves as a predictive marker of recurrence for GIST patients with curative resection, highlighting its potential as a novel therapeutic target that warrants further investigation.