For flow cytometry studies, AsPC-1 and BxPC-3 cells were prepared as described above and then incubated with 10× or 25× cold antibodies in complete medium for 48 h at 37 °C with 5% CO2. After incubation, media was removed and cells were washed with 1× PBS and subsequently labeled with anti-EGFR-AF488 (AY13, Biolegend) and anti-HER3-APC (1B4C3, Biolegend) and analyzed for receptor expression using BD LSR II FLOW cytometer (BD Biosciences).