PPA2 and neoplasm: The protein expression of KPNA3 [21], TACSTD2 [22], GRHL2 [23], NCAM2 [24], LLGL2 [25], ATP1B1 [26], CLTC [27], PARP4 [28], MVP [29], and PPA2 [20] that play a tumor-suppressive role was increased in non-invasive BUC (NIBUC) compared to invasive BUC (Group 1).