In the present study, we focused on the expression of the 4N1K peptide for the following reasons: i) antibodies against this peptide were shown to block the TSP-1-induced inhibition of angiogenesis, suggesting that 4N1K plays a crucial role in the inhibitory effects of TSP-1 on angiogenesis [35]; and ii) 4N1K expression was found to be closely associated with malignant potential, cancer cell progression, and survival in patients with renal cell carcinoma [31]. This evidence concerns the gene THBS1 and renal cell carcinoma.