CSK is required for fulvestrant-induced ERα protein degradation in MCF-7 cells.

(A, B) RNAi knockdown of CSK protein expression caused resistance of intracellular ERα protein to fulvestrant-induced degradation: Western blotting. Cells were infected with control (pLKO.1) or two CSK-knockdown shRNA lentivirus clones and subjected to exposure to fulvestrant. Expression of ERα protein was determined by Western blotting at varying time points of exposure (A). Intensities of ERα protein bands were determined by densitometry (B, mean±SEM of three independent experiments. Asterisk indicates statistical significance, p<0.05). (C) Similar experiments as shown in panels (A, B) were performed, but amounts of ERα protein in total cellular protein were determined by ELISA (mean±SEM of three independent experiments; *, p<0.05 to vehicle control; #, p<0.05 to pLKO.1-infected cells exposed to fulvestrant for the same period).