HSPA4 and cancer: Of interest, no cellular compartment-specific homologs of HSP70 such as HSPA5 (i.e., a binding immunoglobulin protein (BiP) localized in the endoplasmic reticulum) and HSPA9 (i.e., a mortalin localized in the mitochondria) were detected in this study, leading to the suggestion that (i) in the thermotolerant, or oxidative stress tolerant, cancer cells, maintenance of the structural integrity of the respective clients of HSP70s is not obligatory or (ii) HSPA4, which is located in multiple cellular compartments, can likely substitute for the protein folding activity of HSPA5/9.