Thermosensitivity in HIKESHI Knockout Human Oral Squamous Cell Carcinoma HSC-3 Cells

HIKESHI is a nuclear transport carrier protein for HSP70 under heat-stress conditions. To explore the role of HIKESHI in thermosensitivity, we developed HIKESHI knockout (KO) human oral squamous cell carcinoma (OSCC) HSC-3 cell lines using genome editing techniques. Western blotting and sequence analyses confirmed HIKESHI KO in HIKESHI KO-14 (HIKO-14) cells. Cell growth of HIKO-14 cells was significantly decreased compared to that in HIKESHI wild-type (WT) HSC-3 cells. In HIKO-14 cells, nuclear translocation of HSP70 at 42 ℃, but not 44 ℃, was significantly reduced compared to that of WT cells. Under heat stress conditions at 42 ℃, HIKO-14 cells showed a significant increase in thermosensitivity compared to WT cells, indicating that HSP70 located in the nucleus may play an important role in the enhancement of thermosensitivity. However, the increase in thermosensitivity of HIKO-14 cells was not observed under heat stress conditions at 44 ℃. In WT HSC-3 cells, a transient activation of HSF1 was observed upon exposure to 42 ℃ heat. In contrast, sustained activation of HSF1 led to increased expression of HSP70 in HIKO-14 cells exposed to 42 ℃ heat, suggesting that this increased expression may function as cytoprotectant against heat stress in HIKO-14 cells. In conclusion, depletion of HIKESHI inhibited the nuclear translocation of HSP70 and enhanced thermosensitivity at 42 ℃, a temperature within the mild range used for hyperthermia temperature, in OSCC HSC-3 cells.