P4HB and neoplasm: Current data suggests that PDI is an important drug target for cancer therapy because i) it is highly expressed in several cancers as confirmed by gene expression microarrays and proteome analysis, ii) upregulation of PDI correlates with metastasis, invasion, and migration, iii) PDI plays a role in chemoresistance, and iv) PDI supports tumor survival and cancer progression [15, 30].