PDK1 and neoplasm: Next, to reveal the in vivo functions of PDK1-S549 phosphorylation in tumor growth, we employed a xenograft mouse model, and observed that expression of PDK1-S549A could apparently facilitate DLD1-PDK1−/− cell tumor growth compared with PDK1 WT or S549D expressing DLD1-PDK1−/− cells (Fig. 2f–j).