A. Serum starved A549 were incubated (or not) for 30’ with 1 μM Erlotinib and 10 μM PP1-PP2 (5-5 μM), combined (or not), and then exposed to either EGF or CS for additional 30’, as before. EGFR was IPed from the total cell lysates and IBed for total receptor, total tyrosine phosphorylation level (p-YEGFR) and specific Tyr site phosphorylation levels (p-Y1173, p-Y1068, p-Y845). B. The graphic shows the quantification of EGFR p-Y1173, normalized to total EGFR in three independent experiments. NS stands for “Not statistically significant”. * = p < 0.05 in respect to control (-).