The results of gene expression analyses showed that Cyclin D1, Cyclin E1 and MMP9 mRNA levels were significantly higher in ccRCC than that in normal tissues (Fig. 2A-C), whereas there was no significant difference between the expression level of MMP2 in ccRCC and normal control tissues (Supplement 1A). Here, MMP9 is linked to nonpapillary renal cell carcinoma.