siRNA-mediated knockdown of PTEN and its effect on phosphorylation of ribosomal protein S6. The breast carcinoma cell line MDA-MB-231 was treated with siRNAs to characterize the correlation between PTEN levels and ribosomal protein S6 phosphorylation levels. ~15,000 cells are presented. A. PTEN levels displayed as a histogram for samples treated with an siRNA targeting PTEN or a non-targeting control, as indicated. B. Ribosomal protein S6 phosphorylation for the same cells as in A, shown as a histogram of phosphorylation levels as reported by immunofluorescence intensities. C. Pairwise correlation for PTEN and phospho-S6 levels at the single cell level for data presented in A and B.