SMAC Mimetic Debio 1143 And Ablative Radiation Therapy Synergize To Enhance Anti-tumor Immunity Against Lung Cancer

Stereotactic body radiotherapy/ stereotactic ablative radiotherapy(SBRT/SABR)has achieved a comparable effect for early,locally advanced or oligometastatic tumors.In addition to local control,stereotactic ablation radiotherapy changes the tumor local immune microenvironment,produces anti-tumor immune antigen,increases the infiltration of killer T cells and cytokine release to achieve systemic lesion regression.Nevertheless,local recurrence and distant metastasis caused by radiotherapy resistance are still the main modes of treatment failure.In addition,the immune response after radiotherapy with stereotactic ablation radiotherapy is not entirely pro-inflammatory in nature,and sometimes immunosuppressive cells may be recruited and activated after radiotherapy.Therefore,this project aims to explore the mechanism of stereotactic ablation radiotherapy combined with immunotherapy,and provide a new strategy for clinical treatment.Part 1Purpose: Adaptive antitumor immunity following SABR is attenuated by host myeloid-derived suppressor cell(MDSC),tumor-associated macrophage(TAM),and regulatory T-cell(Treg)infiltrates.We hypothesized treatment with SABR and a secondary mitochondrial-derived activators of caspase(SMAC)mimetic could reverse the immunosuppressive lung cancer microenvironment to favor adaptive immunity.Methods: To evaluate for synergy between SABR and the SMAC mimetic Debio 1143 and the dependence upon CD8+ T cells and TNF-α,we used LLC-OVA syngeneic mouse model of lung cancer and treated them with Debio 1143 and/or ART(30 Gy)with or without anti-CD8,anti-TNF-α,or anti-IFN-γ antibodies.Tumorinfiltrating OVA-specific CD8+ T cells,Tc1 effector cells,MDSCs,TAMs,and Tregs,were quantified by flow cytometry.Tc1-promoting cytokines TNF-α,IFN-γ,and IL1β and the immunosuppressive IL10 and Arg-1 within LLC-OVA tumor tissue or mouse serum were measured by RT-PCR and ELISA.Results: SABR delayed tumor growth,and the addition of Debio 1143 greatly enhanced its efficacy,which included several complete responses.These complete responders rejected an LLC-OVA tumor rechallenge.SABR and Debio 1143 synergistically induced a tumor-specific,Tc1 cellular and cytokine response while eliminating immunosuppressive cells and cytokines from the tumor microenvironment.Depletion of CD8+ cells,TNF-α,and IFN-γ with blocking antibody abrogated synergy between SABR and Debio 1143 and partially restored tumor-infiltrating MDSCs.Conclusions: Debio 1143 augments the tumor-specific adaptive immunity induced by SABR,while reversing host immunosuppressive cell infiltrates in the tumor microenvironment in a TNF-α,IFN-γ,and CD8+ T-cell-dependent manner.This provides a novel strategy to enhance the immunogenicity of SABR.Part 2Purpose: SABR is the standard treatment option for advanced prostate cancer.Unfortunately,prostate cancer radioresistance occurs in a large proportion of patients undergoing SABR.As a way to enhance SABR effectiveness,research advances into the mechanisms regulating the immune response have revived interest in combination radiation and immune-based therapies.Methods: mi R-195/-16 family and PD-L1 levels were analyzed in samples from a GSE21032 data set.Kaplan-Meier analysis was used to evaluate the difference in biochemical recurrence-free survival associated with mi R-195 and mi R-16 expression.q RT-PCR and western blot were used to evaluate the mi R-195,mi R-16 and PD-L1 expression.Then,we used bioinformatics analysis and luciferase reporter assay to predict and con rm the mi R-195 and mi R-16 target gene.Finally,we elucidate the mi R-195 and mi R-16 function on immune evasion in the DU145/T cell co-culture model.Results: High levels of mi R-195 and mi R-16 were positively correlated with the biochemical recurrence-free survival of prostate cancer patients.mi R-195 and mi R-16 were inversely correlated with PD-L1,PD-1,CD80 and CTLA-4 expression.Further mechanistic investigations revealed that mi R-195 and mi R-16 inhibited PD-L1 expression.Additionally,restoration of mi R-195 and mi R-16 expression enhanced SABR via T cell activation in the tumor microenvironment by blocking PD-L1 expression.This synergistic effect of immunotherapy and SABR was associated with the proliferation of functional cytotoxic CD8+ T cells and inhibition of myeloidderived suppressor cells and regulatory T cells.Conclusions: Our data reveal biological and functional interactions between immunotherapy and SABR through the mi R-195/-16 family regulatory cascade.Part 3Purpose: SABR has been considered as an option of local therapy that delivers high radiation doses in a few fractions with low morbidity and toxicity.This study investigates the efficacy and safety of SABR for colorectal cancer pulmonary oligometastases and evaluates predictive factors for local control and prognosis.Methods: This retrospective study included 51 patients with 85 lung oligometastases treated with SABR from February 2008 to October 2017.The overall survival(OS),progression-free survival(PFS)and local control(LC)rates were calculated by Kaplan–Meier method.Prognostic variables were assessed by using univariable log-rank test and multivariable Cox regression analyses.Toxicity was graded according to the Common Terminology Criteria for Adverse Events,version 4.0.Results: The median follow-up was 24 months.The median overall survival(OS)and progression-free survival(PFS)were 44 months and 14 months.The 1-and 3-year OS rates,PFS rates,and LC rates were 94% and 62%,51% and 23%,and 80% and 71%,respectively.On multivariate analysis,BED10 ≥138Gy was independently associated with favorable LC rates(HR 0.340;p = 0.038).The patients both with lung and other organ metastases at SABR had unfavorable PFS rates(HR 2.144;p = 0.028).Grade 3 adverse event was only recorded in one patient.Conclusion: SABR is a valid therapy for pulmonary oligometastic CRC patients who are not amenable to surgery or other local treatments.We identified several prognostic factors but it still requires more prospective clinical trials to obtain convincing evidences.