Cells were harvested at 75% confluence using non-enzymatic cell dissociation solution (Sigma-Aldrich) and labeled in suspension with anti-CEACAM1-4S monoclonal antibody MAb 9.2 as described above. Primary and secondary antibodies were diluted in 1% normal goat serum in PBS and incubated sequentially with cells at 4uC for 20 min. Cells were washed with sterile ice cold sort buffer (Ca/Mg++ free, pH 7.0 PBS, 5 mM EDTA, 2 mM HEPES and 1% FBS) and resuspended at a final concentration of 8-10610 6 cells/ml. CEACAM1-4S positive cells were isolated by FACS as previously described by Comegys et al. [38] .