STAT3 and cancer: In urinary bladder cancer cell lines, downregulation of CD44v3 increases cell apoptosis and cell cycle via inhibiting p-STAT3 signal, while using an anti-CD44 antibody to block CD44 signaling could attenuate STAT3 activation in cultured atrial fibroblasts, hinting that blocking CD44-dependent signaling might be a therapeutic option for cancer treatment [36].