HSF1 and cancer: 146. It enhances the phosphorylation of HSF1 at Ser303 and Ser307 through the ERK1/2, GSK3β and CK2 pathways in heat-treated HeLa cells. Consequently, the transcriptional activity of HSF1 is reduced and the formation of the HSF1-SSBP1 complex is disrupted, leading to downregulated expression of HSPs. This cascade of events ultimately results in a significant decrease in cancer cell survival under hyperthermia or chemotherapy (Table 1) 147.