Changes Of Immune Cells In Different Tumors Treated With Or Without Radiotherapy And Their Efficacy Differences

BackgroundDifferent tumors have different cellular components in the tumor microenvironment,so tumor immune surveillance and immune responses are different,resulting in different treatment outcomes.Radiation therapy is widely used to treat many types of cancer.Recent studies have demonstrated the importance of the immune system in mediating the antitumor effects of radiation therapy.Ionizing radiation(IR)enhances DNA sensing-mediated type Ⅰ/Ⅱ interferon(IFN)production through mature dendritic cells(DCs)and activated T cells to mediate antitumor immunity.Research on immune checkpoint inhibitors,such as programmed death 1(PD-1)inhibitors,has focused on enhancing T cell function in part by increasing the production of type Ⅱ IFN,IFNγ.The promise of combined immunotherapy and radiation therapy warrants further study to understand their interactions with different tumors.Current evidence suggests that ionizing radiation(IR)does not appear to be sufficient to maintain antitumor immune effects due to frequent local recurrences.The promotion of enhanced immunotherapy includes increased release of tumor antigens and enhanced antigen presentation by T cell infiltration.In recent years,with the rise of immunotherapy,the research value of tumor microenvironment has become increasingly prominent.Immune cells are the main cellular components of tumor lesions,but the types and functions of immune cells infiltrated in different tumor microenvironments vary greatly,and this difference is not fully understood.ObjectivesIn this study,we aimed to investigate the microenvironment of different tumors after radiotherapy and immunotherapy,especially the changes of immune cells,in order to better understand the heterogeneity among different tumors.Materials and methodsChapter 1:We searched English-language electronic databases including PubMed,EMBASE,and the Cochrane Library to collect studies on the changes in peripheral blood CD3+T lymphocytes,CD4+T lymphocytes,and CD8+T lymphocytes before and after radiotherapy in tumor patients from January 2015 to April 2021.The quality of the included literature was evaluated using the NOS scale provided by the Cochrane Collaboration,and statistical software RevMan 5.4 was used to analyze the included literature.P<0.05 was considered to indicate statistical significance.Chapter 2:LLC,MC38,4T1 and H22 subcutaneous tumor models were established using 4-6 week-old C57BL/6 and BALB/C mice,which were divided into control group(IgG),simple immunization group(PD-1 antibody was injected intraperitoneally with a total of 200ug in 3 times every other day),simple radiotherapy group(8Gyx3F,every other day),radiotherapy combined with immunotherapy group(sequential immunotherapy with PD-1 antibody one week after radiotherapy),tumor growth and survival statistics of mice were conducted from the first day of treatment.Then,kaplan-Meier plots were generated using TIMER database to explore the relationship between immune cell infiltration and prognosis in triple-negative breast cancer,lung adenocarcinoma,and hepatocellular carcinoma.ResultsChapter 1:A total of 19 studies in 16 articles involving 877 tumor patients were included.All data were collected within 1 month before or after radiotherapy.Meta-analysis showed that numbers of CD3+T lymphocytes(SMD:-0.40;95%CI:[-0.75,-0.04];p=0.03)and CD4+T lymphocytes(SMD:-0.43;95%CI:[-0.85,-0.02];p=0.04)were significantly reduced after radiotherapy compared with before treatment,but there was no statistically significant difference for CD8+T lymphocytes(SMD:0.33;95%CI:[-0.88,0.74];p=0.12).Subgroup analysis showed that peripheral blood T lymphocytes were decreased in head and neck cancer.However,in prostate cancer and breast cancer,there were no significant changes in peripheral blood.It has potential proliferation and activation effects on lymphocytes of esophageal and lung cancers 1 month after radiotherapy.However,further immune cell functional typing analysis is required to confirm our conclusions.CD8+T lymphocytes in peripheral blood increased after SBRT.Conventional fractionated radiotherapy,3D-CRT and IMRT all tended to reduce peripheral blood T lymphocytes.The reason may be that SBRT reduces the target volume and the number of fractions,so it can protect circulating lymphocytes.Radiation alone reduces CD3+T lymphocyte numbers,which also suggests that RT alone is not sufficient to establish protective antitumor immunity,but it may enhance the effects of other therapies.Chapter 2:Compared with the control group and the immune group alone,radiation therapy significantly delayed the growth and extended the overall survival time of mice with 4T1 subcutaneous tumor tumor,but the addition of immunotherapy did not further improve the therapeutic effect,and 4T1 subcutaneous tumor showed drug resistance to immunotherapy.In H22 subcutaneous tumor mice,compared with the control group and immunotherapy group,radiotherapy group and sequential immunotherapy for 1 week delayed tumor growth and extended the total survival time of mice,and radiotherapy and immunotherapy showed a synergistic effect.But in LLC subcutaneous tumor mice,in addition to the survival time of the radiotherapy group was slightly longer than that of the immune group,purity of PD1 immune treatment group,the radiotherapy,radiotherapy sequential 1 week immune treatment group four groups,the treatment of tumor growth and overall survival in mice had no statistical difference between each treatment no significant benefit in the LLC treatment in mice.TIMER database was used to analyze the relationship between immune cell infiltration and prognosis in triple negative breast cancer,lung adenocarcinoma and hepatocellular carcinoma.We found that macrophage infiltration was correlated with prognosis in lung adenocarcinoma,while no significant correlation between prognosis and immune cell infiltration was observed in triple negative breast cancer and hepatocellular carcinoma.ConclusionsWithin 1 month after radiotherapy,the patient’s immunology changes significantly,which can cause apoptosis and decrease of T lymphocytes and affect the balance of peripheral blood immune cells.The magnitude of radiation-induced immune responses varied between tumor types.Analyzing immune responses at different time points can help to select patients most likely to benefit from combined therapy and avoid unnecessary radiation-related adverse effects in other patients.Therefore,our current study may pave the way for more effective cancer treatments such as combination immunotherapy.Based on this,in basic experiments,we added immunotherapy to radiotherapy and noticed differences in tumor growth and survival in different tumors.Among H22 liver cancer,LLC lung cancer,and 4T1 breast cancer,H22 liver cancer was relatively sensitive to immunotherapy and radiotherapy compared with the other three subcutaneous tumor models,and the combination of the two therapies showed a synergistic effect.4T1 and LLC were mainly cold tumors,both of which were resistant to immunotherapy,especially for LLC lung cancer.In terms of survival and growth,immunotherapy,radiotherapy and sequential immunotherapy 1 week after radiotherapy showed no statistical difference compared with the control group,showing resistance to radiotherapy.TIMER database analysis showed that macrophage infiltration was associated with the prognosis of lung adenocarcinoma,while there was no significant correlation between the prognosis and immune cell infiltration in triple negative breast cancer and hepatocellular carcinoma.Further quantitative and functional analysis of immune cells by flow cytometry is needed to elucidate the mechanism.