Study On The Combined Treatment Effect And Mechanism Of PARP Inhibitor And BET Protein Inhibitor In Oral Squamous Cell Carcinoma

ObjectivesOral squamous cell carcinoma(OSCC)is a common oral malignant tumor,which has a great impact on the patients’ maxillofacial appearance and function,and therefore has a great impact on the patients’ physical and mental health.About half a million new cases of squamous cell carcinoma of the mouth occur worldwide each year.Although great progress has been made in the treatment of oral squamous cell carcinoma in recent years and numerous preclinical studies have been made on various therapeutic drugs,there are still few drugs with high specificity for oral squamous cell carcinoma in clinical practice.The average 5-year survival rate for patients with advanced squamous cell carcinoma of the mouth remains low,at about 50%.Therefore,the need for more effective drugs for oral squamous cell carcinoma remains urgent.In recent years,targeted drugs for the treatment of malignant tumors by inhibiting the DNA repair process of tumor cells have become a research hotspot,such as PARP family inhibitors.PARP enzyme family is a kind of DNA damage repair enzyme,which plays an important role in DNA damage repair and cell apoptosis.However,to date,the molecular mechanism of oral squamous cell carcinoma resistance to PARP inhibitors has not been elucidated.Because of the mechanism of action of PARP inhibitors,we consider enhancing their anticancer effects from the perspective of synergistic inhibition of DNA damage repair.Homologous recombination(HR)depends on the homology/identity of DNA sequences and is one of the most accurate DNA damage repair mechanisms.Inhibition of THE HR process in malignant cells in order to improve the sensitivity of homologous recombination functional malignancies to PARP inhibitors may have certain clinical benefits.Current research suggests that traditional drug anticancer therapies affect targeted immune responses to tumors,suggesting that oral squamous cell carcinoma resistance to PARP inhibitors may also be associated with immune escape.Powerful selective small molecule inhibitors that affect chromatin modification proteins have been developed as first-line targeted therapies for oral squamous cell carcinoma patients.Therefore,we consider combining it with PARP inhibitors to improve the anticancer effect of PARP inhibitors.In this study,the drug resistance mechanism of ORAL squamous cell carcinoma(OSCC)on PARP inhibitor Olaparib and the effect of the combination with BET inhibitor JQ1 on the therapeutic effect of PARP inhibitor Olaparib on oral squamous cell carcinoma were investigated in order to provide some references for the drug treatment of oral squamous cell carcinoma.Methods1.To observe the proliferation,apoptosis and cell cycle distribution of oral squamous cell carcinoma cells under the action of olaparib and JQ1 alone and in combination.2.Olaparib and JQ1 acted alone or in combination on oral squamous cell carcinoma cells.Real-time quantitative PCR,Western blot and immunofluorescence were used to detect the expression levels of RAD51,BRCA1 and TOPBP1,the DNA double-bond repair related factors,and pD-L1,the immune escape related factors,in tumor cells.3.To observe the therapeutic effect of olaparib and JQ1 on transplanted tumor mouse model when used alone or in combination.Results1.PARP inhibitor olapani induces HR-mediated DNA damage response in oral squamous cell carcinoma cells,promotes the high expression of PD-L1 and induces the high expression of BET protein,which may be partly responsible for the low sensitivity of oral squamous cell carcinoma.2.BET inhibitor and PARP inhibitor have synergistic inhibitory effect on cell proliferation of oral squamous cell carcinoma cells.3.JQ1 and olaparib inhibit the proliferation of oral squamous cell carcinoma cells by inducing cell apoptosis,promote the death of oral squamous cell carcinoma cells,and show a synergistic effect in inhibiting the activity of Ca127 and Scc25 cells,and the mechanism of such induction may be related to the activation of p53 pathway.4.JQ1 combined with olaparib resulted in cell G1 and G2/M phase arrest,resulting in a significant reduction in S phase cells.5.Compared with JQ1 or olaparib alone,the combination of the two drugs has a better anti-tumor effect on oral squamous cell carcinoma in vivo.6.The BET inhibitor JQ1 disrupts THE HR process by inducing inhibition of ATR/CHK1,thus making oral squamous cell cells more sensitive to PARP inhibitors.7.PARP inhibitors up-regulated the expression levels of PD-L1 and BRD4 in oral squamous cell carcinoma cells,while BET inhibitors reduced the expression levels of BRD4 and weakened the pD-Ll-mediated immune activity inhibition,thus enabling oral squamous cell carcinoma cells to obtain better therapeutic effects.ConclusionsThe results showed that the high expression of DNA damage repair related factors and immune escape related factors were involved in the mechanism of oral squamous cell carcinoma resistance to olaparib,which weakened its therapeutic effect on tumor.Experimental results also show that ora panitan and JQ1 in both in vitro and in vivo has strong joint anti-cancer effect,its mechanism of action is inhibition by ATR/CHK1 pathway mediated DNA damage response and suppress through the PD-L1 pathway mediated immune escape,this indicates that the combined use of two drugs could be as a kind of oral squamous cell carcinoma treatment continue to delve into.