ErbB2-activation reduces LRIG1 expression in breast tumor cells. A, Whole cell lysates collected from BT474, SKBR3, MDA-MB-361 and MDA-MB-453 cells were blotted with antibodies to p-ErbB2, ErbB2, LRIG1, and actin. B, MCF-7 cells were transiently transfected for 48h with NeuT or control vector pcDNA3.1 (3.1) and cell lysates were blotted for ErbB2, LRIG1, and actin. Additionally, MCF-7 cells were treated with 100 nM scrambled control (SC) or ErbB2 RNAi oligos (ErbB2-KD) for 48h. Lysates were collected and blotted for ErbB2, LRIG1, and actin. C, MCF-7, T47D, HMEC4, and HMEC6 cells were treated with SS media in the absence or presence of 10 nM Nrg1. After 24h, whole cell lysates were collected and samples were immunoblotted with antibodies to ErbB2, LRIG1, and actin. D, Densitometric analysis of LRIG1 protein expression from each cell line in C is plotted along with SE from at least four independent experiments.