MAPK3 and gastric cancer: Gao et al. found that the acidic microenvironment induced autophagy in GC cells by activating the MAPK/ERK1/2 pathway, while the expression of the pro-apoptotic protein Bax was decreased and the expression of the anti-apoptotic proteins Bcl-2 and NF-κB was increased compared to the neutral condition, suggesting that autophagy may attenuate the susceptibility of GC cells to apoptosis and may help explain why the acidic microenvironment is more conducive to aggressive growth and metastasis of tumour cells (Gao Y. et al., 2019).