Avelumab, an IgG1 anti-PD-L1 Immune Checkpoint Inhibitor, Triggers NK Cell-Mediated Cytotoxicity and Cytokine Production Against Triple Negative Breast Cancer Cells

Abstract

The standard treatment for Triple Negative Breast Cancer (TNBC) patients is cytotoxic chemotherapy, but it is restricted since the duration of response is usually short. Blocking the PD-1/PD-L1 pathway through monoclonal antibodies (mAbs) appears to be a promising therapeutic strategy for TNBC patients. Avelumab is a human IgG1 anti-PD-L1 mAb being tested in clinical trials that may also trigger antibody-dependent cell-mediated cytotoxicity (ADCC) against cancer cells as an additional antitumor activity. In the present work, we studied in vitro Avelumab-mediated ADCC against a panel of TNBC cells with different PD-L1 expression using peripheral blood mononuclear cells (PBMC) or purified NK cells from healthy donors. We determined that Avelumab significantly enhanced NK-cell mediated cytotoxicity against TNBC cells and that tumor cells expressing higher levels of PD-L1 were more sensitive to Avelumab-mediated ADCC. IFN-γ treatment upregulated PD-L1 expression in tumor cells but had a variable impact on Avelumab-mediated ADCC, which could be related to the simultaneous effect of IFN-γ on the expression of NK cell ligands. Moreover, IL-2 and IL-15 stimulation of NK cells enhanced Avelumab-triggered cytokine production and degranulation along with increased lytic activity against tumor cells. Improving the treatment of TNBC remains still a considerable challenge. This in vitro study suggests that Avelumab-mediated ADCC, independently of the blockade of the PD-1/PD-L1 pathway, could be a valuable mechanism for tumor cell elimination in TNBC. Avelumab combination with immunomodulators such as IL-15 or IL-2 could be taken into consideration to increase the therapeutic efficacy of Avelumab in TNBC.

NK Cell-Based Immune Checkpoint Inhibition

“…The immune checkpoint inhibitors, such as monalizumab and lirilumab, aimed at these inhibitory receptors present at the surface of NK cells have been assessed as monotherapy and have shown good safety profiles but mild success in terms of prolonging progression-free survival. Therefore, the combinations of immune checkpoint inhibitors, such as CTLA-4 and PD-1 inhibitors, that are being tried for synergistic response targeting T cells could also be tried in the context of NK cells (368), as anti-PD-1 and anti-PD-L1 inhibitors have also been shown to enhance NK cell-mediated cytotoxicity (346,348,352). Similarly, NKG2A potentiating CD8 T-cell immunity induced by cancer vaccines also stresses the potential of combination therapy (141).…”

“…ADCC toward multiple types of carcinoma cells obtained by avelumab, an anti-PD-L1 antibody, was augmented with epigenetic priming of NK cells and tumor (351). In another study, Avelumab triggered NK cells to produce cytokines and mediate the killing of triplenegative breast cancer cells (352). PD-L1-independent killing of CRC cells that were grown in 3D cultures by densely activated primary human NK cells has also been demonstrated (353).…”

Immune checkpoint molecules in natural killer cells as potential targets for cancer immunotherapy

“…Furthermore, it has been established that anti-CD112R antagonists combined with anti-PD-L1 could also reduce tumor growth or metastasis. 155 , 158 , 161 , 162 In an ex vivo study on human tumor-infiltrating lymphocytes, CD112R blockade enhanced T-cell function, and in combination with TIGIT or PD-1 blockade, further enhanced the effect. 11 , 163 However, its function in human NK cells is still inadequately known.…”

Mechanisms of Resistance to NK Cell Immunotherapy

“…Checkpoint inhibitors may rescue NK cells from exhaustion, unleashing their response and their ADCC activity [188,190,224]. However, it should be considered that blocking one type of receptor-ligand pair may not be always sufficient due to the presence of multiple receptor-ligand pairs within the tumor with variable tissue and immune cell distributions.…”