Peripheral immunological response to treatment with checkpoint inhibitor in recurrent/metastatic nasopharyngeal carcinoma

Abstract

Background: A better understanding of peripheral cellular phenotypes in association with checkpoint inhibitors (CPI) responsiveness in recurrent/metastatic NPC could profoundly impact our knowledge of NPC immunopathology. Methods: Blood were collected from 11 patients with recurrent/metastatic NPC who received CPI (pembrolizumab) after failing second-line chemotherapy. Response to pembrolizumab was assessed by imaging and EBV DNA. Patients who achieved CR/PR were considered responsive and those with SD/PD were considered non-responsive. Four patients in the responsive group also had baseline blood before pembrolizumab. PBMC were freshly isolated and stored until analysis. For surface staining, cells were rested overnight at 37°C before resuspended in BD Brilliant stain with 2.5ng/µl Fc block for 15mins. Cells were then co-stained: 7-AAD, CD19-BV510, CD3-Alexa Fluo 700, CD4-BV510, CD279(PD-1)-BB515, CD197(CCR7)-BV421, CD45RO-APC, CD45RA-Pe-Cy5, CD8-APC-H7, CD27-PE, CD95-PE-Cy7, incubated on ice for 30mins. Samples were washed and acquired on NovoCyte Quanteon. Immune phenotypes were correlated with clinical response. Results: We found that: 1) %CD3 was upregulated in responsive group; 2) CD4/CD8 ratio did not directly stratify drug responsiveness; 3) frequency of PD1-expressing CD8+ T cells was significantly reduced in responsive group; 4) lower frequency of CCR7+PD1+CD8+ T cells in responsive group, suggesting that these may be highly differentiated and have the ability to move into peripheral sites in response to inflammatory chemokines; 5) frequency of naïve and TEMRA CD8+ T cells, but not Tscm was upregulated in responsive group; 6) finally, an interesting finding of sustained CD19+ subsets was observed in non-responsive group. Conclusions: Our results suggest that peripheral blood analysis may provide valuable insights into NPC patients’ responses to PD-1-targeted therapies.