STAT3 and cancer: Given that enhanced EGFR phosphorylation activates multiple downstream signaling pathways, including the MAPK-ERK, the PI3K-AKT, the JAK-STAT3, and the NF-κB [45–48], all of which play critical roles in cancer cell proliferation and migration, we investigated the activation of these pathways in response to circUCK2(2,3) knockdown or overexpression.