Enzo Life Sciences)
was added to tumor cells (3 × 105) in 100 μL
of phosphate-buffered saline (PBS) + 1% bovine serum albumin, and
the mixture was incubated for 1 h at room temperature. The antibody
binding was detected by an fluorescein isothiocyanate (FITC)-conjugated
secondary antibody (1:200, Dako) for 30 min at 4 °C in the dark.
For each sample, at least 10 000 cells were acquired with an
Epics-XL flow cytometer (Beckman Coulter) and data were subsequently
analyzed using the WinMDi software.