Peripheral blood tumor-infiltrating lymphocytes in a neuroblastoma model.

OBJECTIVE

To detect tumor-infiltrating lymphocytes (TILs) in the peripheral blood (PB) of a preclinical neuroblastoma model.

MATERIALS AND METHODS

Two types of preclinical models - immunodeficient mice and immunocompetent mice - were generated by injecting a cell suspension of neuroblastoma cell line NB36769 with MYCN gene (TH-MYCN+) overexpression. Spleen, tumor, and peripheral blood were studied using flow cytometry to detect PD-1+ T-cells. TCR-β immunosequencing was performed in matched samples (tumor and peripheral blood).

RESULTS

Most PB T-cells of immunodeficient mice were CD4 (control: 83.1%; tumor: 86.1%), with a small proportion of PD-1+ T-cells (control: 0.4%; tumor: 0.3%). However, the percentage of PD-1+ T-cells in the spleen was higher (control: 6.5%; tumor: 6.2%), and it was expressed in the CD4+ subset only. Regarding the TCR repertoire of immunocompetent mice, the proportion of the 10 most frequent sequences was significantly higher in tumors (11.09% ± 2.83%) than in the peripheral blood (1.59% ± 0.59%) (p=0.024). These findings are suggestive of clonotype enrichment within the tumor. 9 out of the 10 most frequent tumor clones were identified in the matched peripheral blood sample in 2 mice, and 6 out of 10 in one mouse. In addition, TILs with shared sequences from different animals were found.

CONCLUSIONS

Our results in terms of immunophenotype and clonality suggest the presence of PB T-cells which could include TILs in a preclinical neuroblastoma model.