BDNF and colorectal cancer: MicroRNA-497 has been reported to inhibit thyroid cancer tumor growth and invasion by suppressing BDNF (Wang et al., 2017), which is involved in cell proliferation and invasion of gastric cancer by repressing eIF4E (Li et al., 2014), and to inhibit colorectal cancer growth by targeting insulin-like growth factor 1 receptor (Guo et al., 2013).