Establishing a whole blood CD4+ T cell immunity measurement to predict response to anti-PD-1.

BACKGROUND: Biomarkers that can accurately predict the efficacy of immune checkpoint inhibitors (ICIs) against programmed death 1 (PD-1) ligand in cancer immunotherapy are urgently needed. We have previously reported a novel formula that predicts the response to treatment with second-line nivolumab with high sensitivity and specificity in patients with non-small cell lung cancer (NSCLC) previously treated with chemotherapy. The formula was based on the percentages of CD62LlowCD4+ T cells (effector T cells; %Teff) and CD4+CD25+FOXP3+ T cells (regulatory T cells; %Treg) in the peripheral blood before treatment estimated using the peripheral blood mononuclear cell (PBMC) method. Here, we investigated the applicability of the formula (K-index) to predict the response to treatment with another ICI to expand its clinical applicability. Furthermore, we developed a simpler assay method based on whole blood (WB) samples to overcome the limitations of the PBMC method, such as technical difficulties, in obtaining the K-index. METHODS: The K-index was evaluated using the PBMC method in 59 patients with NSCLC who received first-line pembrolizumab treatment. We also assessed the K-index using the WB method and estimated the correlation between the measurements obtained using both methods in 76 patients with lung cancer. RESULTS: This formula consistently predicted the response to first-line pembrolizumab therapy in patients with NSCLC. The WB method correlated well with the PBMC method to obtain %Teff, %Treg, and the formula value. The WB method showed high repeatability (coefficient of variation, < 10%). The data obtained using WB samples collected in tubes containing either heparin or EDTA-2K and stored at room temperature (18-24 °C) for one day after blood sampling did not differ. Additionally, the performance of the WB method was consistent in different flow cytometry instruments. CONCLUSIONS: The K-index successfully predicted the response to first-line therapy with pembrolizumab, as reported earlier for the second-line therapy with nivolumab in patients with NSCLC. The WB method established in this study can replace the cumbersome PBMC method in obtaining the K-index. Overall, this study suggests that the K-index can predict the response to anti-PD-1 therapy in various cancers, including NSCLC.

CD4+ T-cell Immunity in the Peripheral Blood Correlates with Response to Anti-PD-1 Therapy.

Accumulating evidence indicates that CD8+ T cells in the tumor microenvironment and systemic CD4+ T-cell immunity play an important role in mediating durable antitumor responses. We longitudinally examined T-cell immunity in the peripheral blood of patients with non-small lung cancer and found that responders had significantly (P < 0.0001) higher percentages of effector, CD62Llow CD4+ T cells prior to PD-1 blockade. Conversely, the percentage of CD25+FOXP3+ CD4+ T cells was significantly (P = 0.034) higher in nonresponders. We developed a formula, which demonstrated 85.7% sensitivity and 100% specificity, based on the percentages of CD62Llow CD4+ T cells and CD25+FOXP3+ cells to predict nonresponders. Mass cytometry analysis revealed that the CD62Llow CD4+ T-cell subset expressed T-bet+, CD27-, FOXP3-, and CXCR3+, indicative of a Th1 subpopulation. CD62Llow CD4+ T cells significantly correlated with effector CD8+ T cells (P = 0.0091) and with PD-1 expression on effector CD8+ T cells (P = 0.0015). Gene expression analysis revealed that CCL19, CLEC-2A, IFNA, IL7, TGFBR3, CXCR3, and HDAC9 were preferentially expressed in CD62Llow CD4+ T cells derived from responders. Notably, long-term responders, who had >500-day progression-free survival, showed significantly higher numbers of CD62Llow CD4+ T cells prior to PD-1 blockade therapy. Decreased CD62Llow CD4+ T-cell percentages after therapy resulted in acquired resistance, with long-term survivors maintaining high CD62Llow CD4+ T-cell percentages. These results pave the way for new treatment strategies for patients by monitoring CD4+ T-cell immune statuses in their peripheral blood.