Hyperthermia Inhibits Growth and Stemness of Esophageal Squamous Cell Carcinoma Cells Through Promoting Degradation of GLI1

Background: Hyperthermia is a widely used adjunct treatment for different cancers. The GLI1 is upregulated in ESCC and its expression is associated with the stemness of ESCC.

Objective: We hypothesized that GLI1 constitutes an important hyperthermia treatment target, and investigated its contribution to hyperthermia responses in ESCC.

Methods: The growth of the human ESCC cell lines KYSE70 and KYSE140 was analyzed using CCK-8, clonogenicity and spheres formation assays after 43°C hyperthermia, under conditions of knockdown or overexpression of GLI1. Stemness-related proteins were determined using Western blotting and immunofluorescence staining. Last, the molecular mechanism of GLI1 degradation was studied using chemical inhibitors and immunoprecipitation assays.

Results: Hyperthermia increased the ubiquitination and proteasomal destruction of GLI1, causing a rapid decline in GLI1 protein levels of ESCC cells. Similar to GLI1 knockdown, ESCC cells treated with hyperthermia showed growth inhibition associated with the downregulation of Cancer stemness proteins.

Conclusion: Our study reveals that hyperthermia can readily destabilize GLI1 levels in ESCC cells and inhibit ESCC cells growth. This proposes new strategies for implementing hyperthermia to target GLI1 driven cancers to improve therapeutic efficacy.

GLI1; cancer stem cell; esophageal squamous cell carcinoma; heat shock; hyperthermia; ubiquitination.