FIGURE 4.

Requirement of ErbB2 kinase activity for PMA-induced down-regulation of cell surface ErbB2. SKBR-3 cells were cultured in low serum (0.5% FBS) medium without (A) or with (B) Lapatinib (100 nm) for 24h followed by further incubation in the absence (DMSO) or the presence of PMA (25 nm) for 8 h. Live cells were stained with Alexa Fluor® 488-conjugated anti-ErbB2 antibody and cell surface ErbB2 levels quantified using FACS.