Interactions of Indoleamine 2,3-dioxygenase-expressing LAMP3 dendritic cells with CD4 regulatory T cells and CD8 exhausted T cells: synergistically remodeling of the immunosuppressive microenvironment in cervical cancer and therapeutic implications.

Background: Cervical cancer (CC) is the fourth most common cancer in women worldwide. Although immunotherapy has been applied in clinical practice, its therapeutic efficacy remains far from satisfactory, necessitating further investigation of the mechanism of CC immune remodeling and exploration of novel treatment targets. This study aimed to investigate the mechanism of CC immune remodeling and explore potential therapeutic targets.

Methods: We conducted single-cell RNA sequencing on a total of 17 clinical specimens, including normal cervical tissues, high-grade squamous intraepithelial lesions, and CC tissues. To validate our findings, we conducted multicolor immunohistochemical staining of CC tissues and constructed a subcutaneous tumorigenesis model in C57BL/6 mice using murine CC cell lines (TC1) to evaluate the effectiveness of combination therapy involving indoleamine 2,3-dioxygenase 1 (IDO1) inhibition and immune checkpoint blockade (ICB). We used the unpaired two-tailed Student's t-test, Mann-Whitney test, or Kruskal-Wallis test to compare continuous data between two groups and one-way ANOVA with Tukey's post hoc test to compare data between multiple groups.

Results: Malignant cervical epithelial cells did not manifest noticeable signs of tumor escape, whereas lysosomal-associated membrane protein 3-positive (LAMP3 ) dendritic cells (DCs) in a mature state with immunoregulatory roles were found to express IDO1 and affect tryptophan metabolism. These cells interacted with both tumor-reactive exhausted CD8 T cells and CD4 regulatory T cells, synergistically forming a vicious immunosuppressive cycle and mediating CC immune escape. Further validation through multicolor immunohistochemical staining showed co-localization of neoantigen-reactive T cells (CD3 , CD4 /CD8 , and PD-1 ) and LAMP3 DCs (CD80 and PD-L1 ). Additionally, a combination of the IDO1 inhibitor with an ICB agent significantly reduced tumor volume in the mouse model of CC compared with an ICB agent alone.

Conclusions: Our study suggested that a combination treatment consisting of targeting IDO1 and ICB agent could improve the therapeutic efficacy of current CC immunotherapies. Additionally, our results provided crucial insights for designing drugs and conducting future clinical trials for CC.