P4HB and neoplasm: Comprehensive profiling of the cell surface proteome of different tumor cell types (e.g., A549 lung adenocarcinoma, SH-SY5Y neuroblastoma, LoVo colon adenocarcinoma, Sup-B15 acute lymphoblastic leukemia, CX colon carcinoma and SKOV3 ovarian tumor cells) revealed the presence of numerous chaperones including HSP70, GRP75, GRP78, HSP60, HSP54, HSP27, and protein disulfide isomerase (PDI) on the plasma membrane [10,15].