Adenocarcinoma cells exposed in vitro to Navelbine or Taxol increase Ep-CAM expression through a novel mechanism.

Ep-CAM antigen expression was shown to vary by phase across the cell cycle. Following pretreatment of various adenocarcinoma cells in culture with clinically relevant concentrations of vinorelbine tartrate (Navelbine) or paclitaxel (Taxol), cell surface expression of Ep-CAM antigen increased by two- to ten-fold compared to that of untreated control cells and was associated with arrest of cell cycle progression and accumulation of cells in the S and G2/M phases. We demonstrated that increases in cell surface antigen expression resulted in improved biological effectiveness of the targeting antibody as measured in vitro by antibody-dependent cellular cytotoxicity and in vivo by enhanced antibody targeting to Ep-CAM-expressing xenografts in mice pretreated with Navelbine.