HSPA5 and neoplasm: Interestingly, BiP has been shown to be highly expressed in various tumors due to the ER stress induced by oxygen- and nutrients-deprived tumor microenvironment and to be correlated with tumor growth, invasion, and metastasis, suggesting that ER stress-induced upregulation of BiP in tumors is closely related with the adaptation and the improved tolerance of tumor cells to altered tumor microenvironment [117].