The cyclin-dependent kinase inhibitor, p27^kip1, has no correlation with the malignant potential of GIST

Background: Tumor size and mitotic activity are characteristically associated with the malignant potential and prognosis of gastrointestinal stromal tumors (GIST). However, since neither small tumor size nor low mitotic activity can rule out malignancy, additional factors that may predict malignant behavior have been suggested. Aim: To evaluate the correlation between the cyclin-dependent kinase inhibitor (CDI), p27^kip1, expression and the malignant potential of GIST. Methods: Serial sections were evaluated by immunohistochemistry after staining with antibodies against p27/Kip1 and Ki-67 in surgical material obtained from 36 patients with GIST. p27^kip1 staining intensity and the percentage of positive cells were investigated for association with the malignancy risk, pathological features, overall survival, and disease-free survival. Histologic grade was assigned by spindle vs. epithelioid cell histology, mucosal invasion, tumor cell necrosis or atypia and the number of mitoses. Results: In the multivariate model, p27^kip1 expression was not significantly associated with any of the variables examined except Kit protein-CD117 (r = 0.37, p = 0.03). Comparative evaluation of p27^kip1 expression in GIST cells revealed higher levels of p27 ^kip1 in patients who died compared to those who survived (2.04 ± 0.54 vs. 1.3 ± 0.99, p = 0.1). Conclusion: The CDI p27 ^kip1 was not associated with malignancy of GISTs and did not serve as a predictor of survival.