Hsp70-2 is required for tumor cell growth and survival.

Heat shock protein 70 (Hsp70) family consists of at least eight chaperone proteins that differ from each other by their pattern of expression and intracellular localization. Whereas ample experimental and clinicopathological data has implicated the major stress-inducible Hsp70-1 as a protein required for cancer cell survival, the study of the other family members has been limited by the lack of experimental tools to differentiate between the highly homologous family members. This limitation has been recently overcome by the RNA interference technology that for the first time allows targeted knockdown of the individual Hsp70 family members. Data based on this technology has revealed that also Hsp70-2, a protein essential for spermatogenesis, is required for cancer cell growth and survival. Remarkably, the highly homologous Hsp70 proteins enhance cancer cell growth and survival by distinct molecular mechanisms.