[Dendritic cell and/or PD-1 monoclonal antibody therapy induces intratumoral remodeling of CD8⁺T cells in humanized cerebral glioblastoma mice models].

Objective

To observe alterations in the intratumoral distribution of CD8⁺T cells in humanized glioblastoma (GBM) bearing mice models during the treatment with dendritic cell (DC) vaccine and/or programmed death monoclonal antibody-1 monoclonal antibody (PD-1mAb), using 68Ga-NODAGA-SNA006 with positron emission tomography-computed tomography (PET-CT) imaging.

Methods

A humanized glioblastoma xenograft model was established using humanized T cell-reconstituted mice (hu-TCRM). Mice were randomly divided into four groups (n=15 per group) according to the random number table: control (placebo), PD-1mAb, DC, and DC+PD-1mAb groups. Small-animal fluorescence imaging was performed daily to monitor treatment response. After 20 days of treatment, intracranial tumor volumes was calculated using magnetic resonance imaging (MRI). The CD8-targeted probe ⁶⁸Ga-NODAGA-SNA006 was used with PET-CT for in vivo visualization to acess intratumoral CD8⁺T lymphocyte distribution. Subsequently, the ex vivo analyses were conducted: immunohistochemistry was used to observe CD8⁺T lymphocyte infiltration in tumor tissue and lymph nodes, and flow cytometry was employed to quantify the numbers of infiltrating CD8⁺T lymphocytes in each group of mice. The comparisons among multiple groups were conducted using one-way analysis of variance, and pairwise comparisons between groups were performed using the Tukey HSD test.

Results

Small animal fluorescence imaging showed that on day 12 of treatment, tumor fluorescence intensity in the DC+PD-1mAb group was significantly lower than that in the control group (P<0.001). MRI results indicated that the tumor volumes in the DC+PD-1mAb group was significantly smaller than that in the control group (P<0.001). Both PET-CT and flow cytometry analyses revealed that on day 20 probe accumulation within tumors and the numbers of CD8⁺T lymphocytes in tumor tissue were significantly increased in the DC group and the DC+PD-1 mAb group compared to the control group (Intratumoral probe accumulation: control group vs DC group, P<0.001; control group vs DC+PD-1mAb group, P<0.001. Intratumoral CD8⁺ T lymphocyte count: control group vs. DC group, P<0.01).

Conclusions

Tumor-bearing mice treated with DC vaccine or PD-1 mAb showed significantly increased intratumoral infiltration of CD8⁺T lymphocytes, with the most pronounced infiltration observed in the combination therapy group. The 68 Ga-NODAGA-SNA006 probe combined with PET-CT can reliably visualize changes of intratumoral CD8⁺T lymphocytes in brain GBM tumors during immunotherapy.