However, Qin et al reported that treatment with MEK1/2 inhibitor U0126 in Peptidylargininedeiminase 1 (PAD1) knockdown cells significantly recovers MMP-2 expression, but has no effect on MMP-9 in human triple negative breast cancer (TNBC) cells [48]. Here, MAP2K1 is linked to triple-negative breast carcinoma.