HSF1 and cancer: In a breast cancer model, comprising several cancer cell lines, HSF1 forms a ternary complex with poly-(ADP-ribose) polymerases 1 and 13 (PARP1 and PARP13), which are key facilitators of DNA repair pathways, and in response to DNA damage HSF1 and PARP13 aid in the activation of PARP1 by supporting its auto-PARylation.