GDF15 and esophageal squamous cell carcinoma: Several studies have shown that GDF15 can induce PI3K/Akt and Erk1/2 activation in esophageal squamous cell carcinomas, breast, cervical, gastric, and prostate cancers (56–59), while in brain tumors it was only found that an overexpression of GDF15 did not affected Erk1/2 activation (60).