Effect of cyclin E overexpression on anti-tumor immune responses via activation of the cGAS/STING pathway following radiotherapy.

e15712 Background: Cyclin E is a key regulator of the G1-to-S phase transition and is often upregulated in cancers. Its abnormal activation contributes to genomic instability. Targeting genomic instability through radiotherapy offers potential strategies for cancer treatment. Methods: Investigating the Relationship Between Cyclin E and the Tumor Immune Microenvironment in Pan-Cancer Analyses. Using TCGA database to analyze Cyclin E-associated genomic alterations and mRNA expression, correlating these with patient survival outcomes. We assessed the association between Cyclin E mRNA levels and immune cell infiltration and used Single-cell RNA sequencing to assess DNA damage in Cyclin E-overexpressing cells. Evaluating DNA Damage in Cyclin E-Overexpressing Tumors Post-Radiotherapy. Cyclin E-overexpressing cell lines (HCT116, HT29) were generated. Post-radiotherapy, Comet assays and metaphase spreads assessed DNA damage. γH2AX, 53BP1, and RAD51 levels were detected by immunofluorescence and Western blotting to assess differences in DNA damage and repair. Clonogenic survival were assessed by CCK8 assays and colony formation assays. Investigating the cGAS/STING/TBK1/IRF3 Pathway Post-Radiotherapy in Cyclin E-Overexpressing Tumors. Post-radiotherapy, qRT-PCR and Western blotting were employed to assessed cGAS/STING/TBK1/IRF3 pathway. ELISA measured chemokines. Cyclin E-overexpressing MC38 cells were subcutaneously implanted in C57BL/6J mice, tumor growth were monitored. Immune cells from tumors and lymph nodes were analyzed by flow cytometry. Knockout of cGAS in tumor cells reversed these effects. Results: Cyclin E was upregulated in cancers, associated with poor prognosis and an immunosuppressive tumor microenvironment. Single-cell sequencing showed Cyclin E overexpression increased DNA damage. Compared to the control group, Cyclin E-overexpressing tumors exhibited increased comet assay tail moments and chromatin aberrations after irradiation (p < 0.05), with reduced proliferation and clonogenic survival (p < 0.05). Cyclin E-overexpressing tumors showed increased cytosolic double-stranded DNA (p < 0.05) and elevated levels of phosphorylated STING/TBK1/IRF3. IFN-β, CXCL9, and CXCL10 were also elevated (p < 0.05). In vivo, Cyclin E-overexpressing tumors showed reduced tumor size post-irradiation (p < 0.05) and increased CD8 + T cell infiltration in tumors and lymph nodes (p < 0.05). cGAS knockout reversed these findings. Conclusions: Cyclin E is upregulated in cancers and linked to poor prognosis. However, radiotherapy reverses this effect by exacerbating DNA damage in Cyclin E-overexpressing tumors. This process activates the cGAS/STING pathway, enhancing immune responses, particularly CD8+ T cell infiltration, and ultimately facilitates tumor eradication.