T-cell CX3CR1 expression as a dynamic blood-based biomarker of response to immune checkpoint inhibitors

ABSTRACT: We investigated the frequency of CX3CR1+CD8+ T cells in peripheral blood (PB) before and during immune checkpoint inhibitor (ICI) therapy, and delineated the TCR repertoire in peripheral CX3CR1+CD8+ T-cell subsets and CD8+ tumor-infiltrating lymphocytes (TILs) using preclinical models. To understand the clinical utility of CX3CR1 as a circulating T-cell biomarker, we analyzed longitudinal PB samples from non-small cell lung cancer (NSCLC) patients undergoing anti-PD-1 therapy, and evaluated predictive and prognostic value of changes in the frequency of PB CX3CR1+ CD8+ T cells Methods: Female C57BL/6 mice were inoculated subcutaneously with 5 x 10^5 MC38 tumor cells per mouse on the right flank on day 0. When tumor volume reached approximately 50 mm^3, 200 µg of anti-PD-L1 Ab (clone 10F.9G2, BioXcell) and 100 µg of anti-CTLA-4 Ab (clone 9H10, BioXcell) were administered intraperitoneally every 3 days and every other day, respectively. MC38 tumor-bearing mice were treated for 14 days, and spleens and tumors were harvested. [Tumor cells] Tumors were cut into small pieces of 2-4 mm. Single-cell suspensions were obtained by mechanical dispersion consisting of two 30-min incubations at 37°C, 5% CO2 in 5 ml RPMI 1640 (Gibco) and tumor dissociation kit (Miltenyi Biotec) in C Tubes (Miltenyi Biotec) interspersed with three mechanical dispersions on a GentleMACS dissociator (Miltenyi Biotec). The tumor cell suspensions were then filtered through a cell strainer (70 μm; BD Biosciences). An EasySep Mouse CD8a Positive Selection Kit II (STEMCELL Technologies) was used to isolate murine CD8+ tumor-infiltrating lymphocytes (TILs) for TCR sequencing. [Splenocytes] Spleens were homogenized by forcing the tissue through a cell strainer (70 μm; BD Biosciences). Red blood cells in blood and spleen were lysed using ACK Lysis Buffer (Gibco). For TCR sequencing of murine splenic CD8+ T cells, single cell suspensions from freshly isolated splenocytes were stained. CD45+ CD3+ CD8+ T cells were gated, and CD27lo CX3CR1-, CD27hi CX3CR1-, and CX3CR1+ CD8+ T cells were sorted using BD FACSAria II Cell Sorter. DNA from flow-isolated murine splenic CD8+ T cells and CD8+ TILs, and PB CD8+ T cells was extracted using QIAamp DNA Micro Kit (QIAGEN). DNA was quantified using Qubit dsDNA BR Assay (Invitrogen). Amplification and sequencing of TCRβ CDR3 regions was performed using ImmunoSEQ immune profiling system at the survey level (Adaptive Biotechnologies). Sequencing was performed on an Illumina NextSeq system using 150 cycle mid-output kit (Illumina Inc.). Processed data were uploaded to the ImmunoSEQ Platform (Adaptive Biotechnologies) for bioinformatics analysis. Processed data were downloaded and frequencies/counts for TCR clonotypes and diversity were examined by nucleotide sequences after non-productive reads were filtered out. Results: Clonally expanded TCR repertoires of CD8+ TILs are enriched in the peripheral CX3CR1+ subset during ICI therapy. ICI therapy induces high degree of TCR sequence similarity and clonality between CD8+ TILs and the peripheral CX3CR1+ CD8+ T cells.

ORGANISM(S): Mus musculus

PROVIDER: GSE165383 | GEO | 2021/01/26

REPOSITORIES: GEO