EGR1 and breast cancer: Knockdown of PLCH1 using two specific siRNAs (si-PLCH1#1 and si-PLCH1#3) in BT-474 breast cancer cells significantly reduced the expression of p-ERK and early growth response 1 (EGR1), key components of the ERK signaling pathway, as demonstrated by Western blot analysis (Figure 8A).