Thrombospondin-1-derived 4N1K peptide expression is negatively associated with malignant aggressiveness and prognosis in urothelial carcinoma of the upper urinary tract

Background Thrombospondin (TSP) is a multi-functional protein that appears to have dual roles in cancer, that is, either as a promoter or a suppressor. 4N1K is a TSP-derived peptide that has been reported to be associated with neovascularity, cell survival, and invasion. There is a little information regarding its pathological roles in human cancer tissues. Our aim was to clarify clinical significance and prognostic value of 4N1K expression in patients with urothelial carcinoma of the upper urinary tract (UC-UUT). Methods We investigated 4N1K expression in 97 surgically excised, non-metastasized UC-UUT specimens and five normal tissues via immunohistochemistry. Microvessel density (MVD), lymph vessel density (LVD), cancer cell proliferation (PI), apoptotic index (AI), and matrix metalloproteinase (MMP)-9 expression was also determined. The relationships 4N1K expression and pT stage, grade, and prognosis were analysed. In addition, correlations with these cancer-related and TSP-related factors were also investigated. Results Strong and moderate 4N1K expression was found in normal urothelial tissues. Of the 97 specimens, 45 patients were positive for 4N1K expression, which was primarily located in the interstitial areas of the cancer tissue. 4N1K expression was negatively associated with pT stage ( p = 0.003) and grade ( p = 0.002). Survival analyses revealed that 4N1K is a predictor of metastasis-free ( p = 0.036) and cause-specific survival ( p = 0.009). 4N1K expression was closely associated with malignant behaviour, specifically MVD ( p = 0.001), AI ( p = 0.013), and MMP-9 expression ( p = 0.036), but not PI and LVD, as determined via multivariate analysis models. Conclusions 4N1K expression appears to be associated with cancer cell progression and survival in UC-UUT patients via the regulation of angiogenesis, apoptosis, and MMP-9 expression. There is a possibility that the 4N1K-peptide may be a useful marker and novel therapeutic target in patients with UC-UUT.