RPS6KB1 and breast cancer: We further extended the findings in breast cancer cells to normal MEF cells, by using two independent pairs of Rps27l+/+ vs. Rps27l−/− MEFs15, and found that Rps27l−/− MEFs had reduced basal phosphorylation levels of S6K1 and 4E-BP1 (Fig. 3a, Figure S3).