Peptidyl arginine deiminase, type II (PADI2) expression has been shown to potentiate multiple different
carcinogenesis pathway including
breast carcinoma and spontaneous skin
neoplasia. The objective of this study was to examine the role of PADI2 in urothelial
bladder cancer which has not been evaluated previously. Analysis of mutation and genome amplification of
bladder cancer within The
Cancer Genome Atlas (TCGA) showed that PADI2 is both mutated and amplified in a cohort of
bladder cancer patients, with the largest number of mutations detected in urothelial
bladder cancer. Even though PADI2 expression was not significantly correlated to survival in
bladder cancer patients, it was significantly overexpressed at the
mRNA and
protein levels, as revealed by TCGA data and immunohistochemistry analysis, respectively. PADI2 showed wide expression pattern in
bladder cancer tissues but was hardly detected in
tumor adjacent normal tissue. RNAi mediated silencing of PADI2 in the
bladder cancer cell line T24 did not result in a change of proliferation. Interestingly knockdown of PADI2 expression did not affect Snail1
protein, which is associated with metastatic progression, in these cells. However, PADI2 silencing remarkably attenuated both in vitro migration and invasion- in T24 cells indicating a Snail1-independent effect of PADI2 on invasive potential of urothelial
bladder cancer. This was further corroborated by in vivo xenograft assays where PADI2
shRNA harboring T24 cells did not have detectable
tumors by week 4 as compared to robust
tumors in the control
Luciferase shRNA harboring cells. PADI2 silencing did not affect proliferation rates and hence this would suggest that PADI2 knockdown is perhaps causing increased apoptosis as well as transition through the cell cycle, which needs to be confirmed in future studies. Our results reveal a yet undefined role of PADI2 as an oncogene in urothelial
bladder cancer.