Effect And Mechanism Of Hyperthermia On The Expression Of CGAS In Cervical Cancer Cells

Hyperthermia is an important treatment associated with regulating both innate and adaptive immune responses.Hyperthermia can stimulate the expression of homeostasis chemokines,integrins,adhesion factors,and cytokines IFN-γ,IL-2,etc.Combination hyperthermia with radiotherapy and chemotherapy in the treatment of cervical cancer also up-regulates the secretion of cytokines and induces an intensive systemic anti-HPV immune response.However,people have not fully understood the mechanism of hyperthermia promoting cytokine expression.cGAS is a kind of cytoplasmic double-strand DNA sensor discovered in recent years.After sensing abnormal DNA in the cytoplasm,cGAS will activate the cGAS-STING pathway and stimulate type I IFN response,which is an important part of the innate immunity of the host.As a kind of ds DNA virus,HPV will be cleared by various immune mechanisms.Correspondingly,HPV has also developed multiple mechanisms to escape hosts’ immune response.To continuously infect hosts,viruses have to avoid the innate immune and adaptive immune response.In order to learn the effect of hyperthermia on the expression of cGAS,HPV18 positive cervical cancer cells He La and HPV16 positive cervical cancer cells Si Ha were selected,and two kinds of heating models to treat cells were established: early response and periodic mode.The transcription level of cGAS was detected by q RT-PCR,and the expression of another nucleotide sensor RIG-1 was also detected.Results showed that the m RNA level of cGAS was more than twice that of the control group after 60 minutes of heating at 42°C.The expression of cGAS increased significantly after two cycles of periodic mode,but the promotion effect of 42°C on RIG-1 was not that obvious.In view of the important role of HPV E6 and E7 in the immune escape of the virus,the expression of the two was then detected.Continuous cultivation at 42°C for 90 min can completely inhibit the expression of E6,E7 of HPV16 and HPV18.To investigate whether the increase of cGAS expression caused by heat stress is related to histone modification,the expression of histone acetyltransferase EP300 and GCN5 after 2 kinds of heating treatment were detected by q RT-PCR.After continuous cultured at 42°C for 30 min,the expression levels of EP300 and GCN5 increased significantly,and both maintained a high level of expression after 120-180 min.After periodic heating treatment,the expression patterns of EP300 and GCN5 were similar to cGAS which reached the peak on the second day.It can be seen that hyperthermia can stimulate the transcription level of key enzymes of epigenetic modification.This research proves that hyperthermia can up-regulate the expression of cGAS which is a key enzyme of type I IFN response,and can almost completely inhibite the expression of HPV key oncogenic proteins E6 and E7,which contributes to restore hosts’ innate immuity.In view of the inhibition of acetylation by HPV,the increased expression of EP300 and GCN5 after hyperthermia has positive significance for the immunity of hosts and the cure of cervical cancer.