PD-1 Blockade Induces Reactivation of Nonproductive T-Cell Responses Characterized by NF-κB Signaling in Patients with Pancreatic Cancer

PURPOSE

Pancreatic ductal adenocarcinoma (PDAC) trials have evaluated CTLA-4 and/or PD-(L)1 blockade in patients with advanced disease in which bulky tumor burden and limited time to develop antitumor T cells may have contributed to poor clinical efficacy. Here, we evaluated peripheral blood and tumor T cells from patients with PDAC receiving neoadjuvant chemoradiation plus anti-PD-1 (pembrolizumab) versus chemoradiation alone. We analyzed whether PD-1 blockade successfully reactivated T cells in the blood and/or tumor to determine whether lack of clinical benefit could be explained by lack of reactivated T cells versus other factors.

EXPERIMENTAL DESIGN

We used single-cell transcriptional profiling and TCR clonotype tracking to identify TCR clonotypes from blood that match clonotypes in the tumor.

RESULTS

PD-1 blockade increases the flux of TCR clonotypes entering cell cycle and induces an IFNγ signature like that seen in patients with other GI malignancies who respond to PD-1 blockade. However, these reactivated T cells have a robust signature of NF-κB signaling not seen in cases of PD-1 antibody response. Among paired samples between blood and tumor, several of the newly cycling clonotypes matched activated T-cell clonotypes observed in the tumor.

CONCLUSIONS

Cytotoxic T cells in the blood of patients with PDAC remain sensitive to reinvigoration by PD-1 blockade, and some have tumor-recognizing potential. Although these T cells proliferate and have a signature of IFN exposure, they also upregulate NF-κB signaling, which potentially counteracts the beneficial effects of anti-PD-1 reinvigoration and marks these T cells as non-productive contributors to antitumor immunity. See related commentary by Lander and DeNardo, p. 474.

Combination Therapies to Improve the Efficacy of Immunotherapy in Triple-negative Breast Cancer

Immune checkpoint inhibition combined with chemotherapy is currently approved as first-line treatment for patients with advanced PD-L1-positive triple-negative breast cancer (TNBC). However, a significant proportion of metastatic TNBC is PD-L1-negative and, in this population, chemotherapy alone largely remains the standard-of-care and novel therapeutic strategies are needed to improve clinical outcomes. Here, we describe a triple combination of anti-PD-L1 immune checkpoint blockade, epigenetic modulation thorough bromodomain and extra-terminal (BET) bromodomain inhibition (BBDI), and chemotherapy with paclitaxel that effectively inhibits both primary and metastatic tumor growth in two different syngeneic murine models of TNBC. Detailed cellular and molecular profiling of tumors from single and combination treatment arms revealed increased T- and B-cell infiltration and macrophage reprogramming from MHCIIlow to a MHCIIhigh phenotype in mice treated with triple combination. Triple combination also had a major impact on gene expression and chromatin profiles shifting cells to a more immunogenic and senescent state. Our results provide strong preclinical evidence to justify clinical testing of BBDI, paclitaxel, and immune checkpoint blockade combination.