RPS6KB1 and breast cancer: Besides the colon cancer cells, the elevation of p70S6K1 phosphorylation is also observed in breast cancer MCF7 cells treated with an IGF-1R inhibitor, OSI-906.30 Collectively, our findings indicate that enhancement of p70S6K1 phosphorylation is a key event for the resistance to IGF-1R inhibition in colon cancer cells.