HSP70 Promotes Heat Tolerance Effect of Lung Cancer Cells Through Mediating SUMOylation of HIF-1α

Radiofrequency ablation produces a heat-tolerance effect and increases HIF-1αp, and HSP70 expression is distributed in the lesion, but whether HSP70 mediates HIF-1α SUMOylation in lung cancer cells remains unclear. Mouse lung cancer LLC cells were cultured under hypoxia and randomly assigned into control group, heat tolerance group and HSP70 siRNA group followed by analysis of HSP70 and HIF-1α level by real time PCR and Western blot, association of HIF-1α with SUMO-1 and SUMO-2/3 by immunoprecipitation, SENP-1, Ubc9 and E3 ligase expression. CD4 + T cells were isolated and divided into control group, hyperbaric oxygen group, normal temperature hypoxia group, and high temperature hypoxia group followed by measurement of T17 and Treg cell by flow cytometry, and HIF-1α level. HSP70 and HIF-1α level was increased in heat tolerance group and reduced by HSP70 siRNA. Meanwhile, HSP70 siRNA decreased HSP70 binding to SENP-1, Ubc9, and E3 ligase. Heat tolerance group showed decreased SENP-1 expression, increased Ubc9 and E3 ligase expression. HIF-1 bound to SUMO-1, but not SUMO-2/3. HIF-1α expression was increased in CD4+ T cells in treatment group, with significantly increased CD4+ T cells apoptosis and changes of Treg and Th17 compared to control (P < 0 05). HSP70 can promote the heat tolerance effect of lung cancer cells by promoting SUMO-1 expression of HIF-1α; the heat tolerance effect leads to abnormal cellular immune response, which may affect the therapeutic effect.