Figure 6

Stat6 is required for the inhibition of G1/S cell cycle progression by progesterone. Synchronized T47D cells, transfected with control or Stat6 siRNAs (500 ng) and treated with or without progesterone, were harvested after 12 h or 24 h to determine cell cycle phase distribution (A) or Western blotting using either an antibody raised against pRB phosphorylated at Ser807/811 or an antibody recognizing specifically the underphosphorylated form of pRB (B). Representative Western blotting results are shown in B. pRB-Ser807-811, pRB phosphorylated on the Ser807/811 residue; pRB, hypophosphorylated pRB. The MDA-MB-468 cell line, deficient in pRB expression, was used as a negative control of pRB staining.