ADAM9 and neoplasm: By the Spearman correlation test, the IRS of ADAM9, CDCP1, and t-PA were significantly and positively correlated with distinct degrees of tumor cell differentiation in OSCC (r = 0.737, P < 0.001; r = 0.392, P = 0.009; and r = 0.526, P < 0.001; respectively; Fig. 2B), suggesting that enhanced expressions of ADAM9, CDCP1, and t-PA are associated with high-grade OSCC.