BAX and gastric cancer: Vitamin D amplified the effect of cisplatin by upregulating the pro-apoptotic protein like BCL2-associated X protein (Bax), enhancing cell cycle regulators such as p21 and p27 [51], and reducing the phosphorylation of phosphatidylinositol 3-kinase/AKT and extracellular-signal-related kinase 1/ERK, kinases implicated in GC cell proliferation and apoptosis [52,53].