SKP2 and gastrointestinal stromal tumor: However, high p16 and p53 expression was found to be an unfavorable factor in univariate analysis, and p53 overexpression correlated with several parameters of malignant potential (mitotic index, AFIP high risk, cell type, Ki67 and SKP2 expression), indicating an important auxiliary role for p53 in predicting the aggressive potential of GIST.