MMP2 and nonpapillary renal cell carcinoma: In patients with ccRCC, positive correlations of SPOCK1 with MMP-14, MMP-16, and MMP-2 were also observed in tumor tissues, and a combination of high SPOCK1 and high MMP2 expressions revealed the worst prognosis compared to others, suggesting that the SPOCK1-MMP-2 axis may thus be a specific biomarker for forecasting EMT-regulated invasion of ccRCC cells and be a valuable therapeutic target for treating ccRCC patients.