ERBB4-truncated forms induce cell detachment in HEK-293T cells. (A) HEK-293T cells transfected with I12ΔERBB4-CYT1 (I12ΔC1), I12ΔERBB4-CYT2 (I12ΔC2), I20ΔERBB4-CYT1 (I20ΔC1), or I20ΔERBB4-CYT2 (I20ΔC2) express ERBB4-truncated proteins. I12ΔERBB4 constructs were constitutively phosphorylated. Total and phosphorylated (p-) proteins were detected by western blot analysis with the indicated antibodies. (B) HEK-293T cells expressing wild-type ERBB4 (WT) or I12ΔERBB4 C1 and C2 showed extracellular signal-regulated protein kinase (ERK) and phospholipase C-γ (PLCγ) pathways activation. I12ΔERBB4 and I20ΔERBB4 cotransfection (1:10 ratio) induced I20Δ trans-phosphorylation (arrow). (C) ERBB4-mediated ERK and PLCγ activations are inhibited by lapatinib treatment (2 μM). (D) HEK-293T cells conditionally expressing GFP or a doxycycline-inducible I12ΔERBB4 construct were analyzed by contrast-phase microscope 4 days after doxycycline administration (1 μg/mL). Original magnification ×10. (E) HEK-293T cells expressing the indicated constructs were analyzed in the presence or absence of doxycycline (DOX) and lapatinib treatment. Floating cells were quantified at days 4 and 6 and expressed as fold increase compared to GFP (relative number). Error bars represent standard deviation of 3 independent experiments. DMSO, dimethylsulfoxide.