STAT3 and breast cancer: By comparing shDLEU1#2 cells with shDLEU1#2+HIF-1α cells, we found that similar to impacts presented by overexpressing CKAP2, HIF-1α was sufficient to reverse shDLEU1-induced inhibition on cell proliferation (Fig. 6A), migration (Fig. 6B), invasion (Fig. 6C), activation of ERK and STAT3 signaling, or CKAP2 expression (Fig. 6D), suggesting that by up-regulating CKAP2, HIF-1α critically mediates DLEU1-induced malignant behaviors of breast cancer cells.