Efficacy of Wee1 G2 Checkpoint Kinase and Mouse Double Minute 2 Homolog Inhibitors in Gastrointestinal Stromal Tumors Determined by p53 Status.

Background: KIT proto-oncogene, receptor tyrosine kinase (KIT, CD117) and platelet-derived growth factor-alpha (PDGFRA) are key drivers of gastrointestinal stromal tumors (GIST), but resistance to targeted therapy often arises from tumor protein p53 (p53) alterations and loss of cell cycle control. However, the role of p53 status in GIST therapeutic potential has rarely been studied, so this study aimed to employ both wild-type and mutant p53 GIST models to investigate how p53 dysfunction influences the efficacy of p53 pathway-targeted therapies. Methods: The efficacy of the mouse double minute 2 homolog (MDM2) inhibitor (HDM201) and the Wee1 G2 checkpoint kinase (Wee1) inhibitor (adavosertib) was confirmed in both p53 wild-type (p53 WT) and p53 mutant (p53 MT) GIST cells. The anti-proliferative effects were assessed using the Cell Counting Kit-8 (CCK-8) assay. Flow cytometry (FACS) and immunoblotting were employed to evaluate apoptosis and the expression of proteins related to drug efficacy. These findings were further validated in a xenograft model. Results: HDM201 selectively inhibited growth and triggered apoptosis in p53 WT GIST cells, while adavosertib was effective mainly in p53 MT cells. Western blot analysis revealed that HDM201 increased p53 and p21 levels in p53 WT cells, and adavosertib affected Wee1 and phospho-cdc2 expression in both p53 WT and p53 MT cells. In a xenograft mouse model, HDM201 significantly reduced the tumor volume and weight in p53 WT GIST cells, whereas p53 MT tumors showed only a moderate size reduction with adavosertib, without significant changes. Conclusions: Our results highlight the importance of p53 status in guiding GIST treatment. p53 WT tumors respond to MDM2 inhibitors, while p53 MT tumors show greater sensitivity to Wee1 inhibitors, supporting p53 pathway targeting as a promising strategy for GIST patients.