Figure 1: Transcriptional regulation of Hsp synthesis under stress conditions. The transcription factor, HSF1 is negatively regulated by either Hsp70 or Hsp90 under normal physiological conditions. Stress induces disassociation of HSF1 from Hsp and leads to its activation through phosphorylation and oligomerization to enable it to bind to the promoters of Hsp genes. The induced Hsps therefore are involved in the cytoprotection in stressed cell or in the case of tumors, they may help in the escape of immune responses. The anti-Hsp drugs that either limit Hsp transcription or interfere with Hsp chaperone activity promote cell death, immune lysis or may be involved with host immunity.