PO-398 Markers of immune exhaustion and immune suppression in immunoregulatory network of virus-associated cervical cancer: putative contribution in the induction of invasive tumour growth

Abstract

IntroductionAchieving positive outcomes of using immunotherapeutic approaches in cancer treatment implies multifaceted targeting of functionally different mechanisms of immune response, including immune exhaustion mechanisms, regulatory cell-mediated pathways, and inflammation. Of particular interest are molecular mechanisms that accompany the initial steps of invasive tumour growth. In the case of virus-associated cancer, particularly cervical cancer, there are still many questions to be answered regarding this issue.Material and methodsTranscriptomes of pre-invasive and invasive cervical cancer tissue samples were explored using RNA sequencing (RNAseq) on the Illumina MiSeq platform followed by bioinformatic analysis of immune-related signalling pathways. Flow cytometry was used to phenotype peripheral blood lymphocytes and tumor-infiltrating lymphocytes in enzymatically dissociated tissue samples.Results and discussionsAs follows from RNAseq data, in early-stage invasive cervical cancer, the expression of a wide set of interferon-induced genes and inflammatory response genes (including a specific group of innate molecular sensors of nucleic acids) was significantly elevated, as compared to pre-invasive carcinoma. In contrast, effector T and NK-cell activation markers were expressed at low levels. Interestingly, many markers of immune exhaustion and inhibitory ‘immune checkpoint’ molecules didn’t show any noticeable increase in mRNA levels, furthermore, some of them were found to have lower expression levels in invasive cancer. Pathway analysis revealed that, among the mechanisms most significantly upregulated in invasive vs. pre-invasive cancer, those mediated by immunosuppressive cytokines and implicated in differentiation of regulatory T cells were prevalent, while IL12-dependent pathways of T and NK-cell activation and differentiation were enriched among the downregulated genes. The results of transcriptome analysis are in agreement with our findings from flow cytometric assessment of regulatory (suppressive) cell populations within tumor-infiltrating lymphocytes and co-expression of PD-1, TIM-3, and LAG-3 in major subsets of peripheral blood lymphocytes in patients with early forms of cervical cancer.ConclusionThe observed relationships may be considered a direct consequence of impaired immune cell activation processes and an essential condition for further progression of inflammatory environment required for invasive growth of a tumour. The work is supported by the Russian Science Foundation (project №17-75-10027).