Effects of CD9-specific sense and antisense oligonucleotides on the expression of the tetraspanin on the surfaces of HMC-1 cells. HMC-1 cells were incubated with increasing amounts of a CD9-specific antisense (A,C,E) or sense (B,D,F) oligonucleotide. Twelve hours later, FACS analysis was carried out using anti-CD9 mAb. The gray line in each panel represents the surface expression of CD9 in the untreated control cells. The data depicted in black are the FACS data obtained with the 6 populations of oligonucleotide-treated cells.