Prognostic Significance of Phosphorylated FOXO1 Expression in Soft Tissue Sarcoma

Forkhead box O1 (FOXO1; forkhead in rhabdomyosarcoma, FKHR) is a key transcription factor that regulates the cell cycle and apoptosis, and therefore is considered to be involved in cell transformation and tumorigenesis. Expression of FOXO1 in soft tissue sarcoma (STS) and its correlation with clinicopathological factors and prognostic significance were evaluated. Expression of phosphorylated FOXO1 (p-FOXO1) in localized STS from 84 adult patients, 50 male and 34 female, aged 15-89 (median 54) years, was evaluated by immunohistochemistry. Staining intensity of p-FOXO1 in the tumors was judged separately for the nucleus and cytoplasm and categorized as follows: level 0, absent or faint staining; level 1, weaker than that of endothelial cells in the same specimen; and level 2, equal to or stronger than that of endothelial cells. Twenty-three (27.3%), 26 (31.0%), and 35 (41.7%), and 32 (38.1%), 30 (35.7%), and 22 (26.2%) of the tumors showed level 0, 1, and 2 expression of p-FOXO1 for the nucleus and cytoplasm, respectively. Nuclear p-FOXO1 expression correlated with mitotic count, and cytoplasmic p-FOXO1 expression with histological subtype, mitotic count, cellularity, myxoid change, Ki-67 labeling index, histological grade, American Joint Committee on Cancer stage, and patient age. Multivariate analysis revealed nuclear and cytoplasmic p-FOXO1 expression, mitotic count, and tumor size to be independent prognostic indicators for overall survival, and cytoplasmic p-FOXO1 expression for disease-free survival, respectively. The prognostic significance of p-FOXO1 expression level in STS was demonstrated.