Abstract 2785: The role of heat shock factors for cancer stem cell regulation

Abstract

Abstract Introduction: Heat shock factor family is a group of transcription factors that can bind specifically to heat shock elements (HSE) within the promoter region of heat shock protein (HSP). The HSF pathway activation helps cells survive under stress by preventing protein misfolding and aggregation. Three heat shock factors (HSF1, HSF2 and HSF4) have been identified in humans, among them, HSF1, which is believed to be the master regulator of cellular response to stress, is by far the best-characterized member of the HSF family. We first identified that high HSF1 is associated with high tumor grade and poor survival in multiple cancer models including breast, ovarian, lung and colon cancers. In addition, our recent data indicate that HSF1 drives a distinct transcription program that is unrelated to heat shock response in malignant tumors, and this HSF1 “non-heat shock related transcription program” correlates with poor outcome in breast cancer patients. Moreover, we confirmed that HSF1 drives the Cancer Stem Cell (CSC) phenotype in multiple breast cancer cell lines and facilitate chemo-treatment resistance by increasing CSC frequency in breast cancer cells. Previous studies have shown that HSF2 and HSF4 may play a role in cancer progression either on their own or through interaction with HSF1. HSF2 forms hetero-trimers with HSF1 and facilitate its function in response to heat shock. Inactivation of HSF4 in p53 null mouse models causes cell senescence and suppression of tumorigenesis, with great similarities to HSF1-/- p53 null mice. Results: In an attempt to investigate how HSF1 is activated to regulate CSC phenotype, we constructed phospho HSF1 at three different sites. We observed that there is no correlation of phospho activation of HSF1 with CSC phenotype. In follow-up work to the studies above, we found that both HSF2 and HSF4 are also significantly up-regulated in CSCs, suggesting that they may cooperate with HSF1 in regulating CSCs. Moreover, we discovered that HSF4 is over-expressed in breast cancers compared to normal mammary gland, and over-expression of HSF4 induces tumorsphere formation in breast cancer cells. Conclusion: These observations indicated that in order to gain a complete understanding of the role of the HSFs in cancer it is now necessary to study all three HSFs together. Citation Format: Ankita Thakkar, Bin Wang, Tan A. Ince. The role of heat shock factors for cancer stem cell regulation. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2785.