Our results showed that the expression of both TIMP-2 and TIMP-1 decreased when MMP-2 and MMP-9 were up-regulated following XRCC1 knockdown (Figure 4A), which indicated that XRCC1 can regulate MMP-2 and MMP-9 expression through TIMP-2 and TIMP-1 in ccRCC. The gene discussed is MMP9; the disease is nonpapillary renal cell carcinoma.