PD-L1 expression in metastatic neuroblastoma as an additional mechanism for limiting immune surveillance. (2nd January 2016)

• Record Type: Journal Article
• Authors: Dondero, Alessandra; Pastorino, Fabio; Della Chiesa, Mariella; Corrias, Maria Valeria; Morandi, Fabio; Pistoia, Vito; Olive, Daniel; Bellora, Francesca; Locatelli, Franco; Castellano, Aurora; Moretta, Lorenzo; Moretta, Alessandro; Bottino, Cristina; Castriconi, Roberta
• Is Part Of: Oncoimmunology. Volume 5:Number 1(2016)
• Publication Date: 2016-01-02
• Subjects: Anti-tumor immunity -- immune checkpoints -- neuroblastoma -- natural killer cells -- T cells -- PD-1 -- PD-L1 -- PD-L2 -- INF-γ -- TNF-α; Tumors -- Immunological aspects -- Periodicals; Neoplasms -- therapy -- Periodicals; Immunotherapy -- Periodicals; 616.994
• DOI: 10.1080/2162402X.2015.1064578
• Languages: English
• ISSNs: 2162-402X

Abstract

ABSTRACT: The prognosis of high-risk neuroblastoma (NB) remains poor, although immunotherapies with anti-GD2 antibodies have been reported to provide some benefit. Immunotherapies can be associated with an IFNγ storm that induces in tumor cells the "adaptive immune resistance" characterized by the de-novo expression of Programmed Death Ligands (PD-Ls). Tumor cells can also constitutively express PD-Ls in response to oncogenic signaling. Here, we analyze the constitutive and the inducible surface expression of PD-Ls in NB cells. We show that virtually all HLA class I pos NB cell lines constitutively express PD-L1, whereas PD-L2 is rarely detected. IFNγ upregulates or induces PD-L1 both in NB cell lines in vitro and in NB engrafted nude/nude mice. Importantly, after IFNγ stimulation PD-L1 can be acquired by NB cell lines, as well as by metastatic neuroblasts isolated from bone marrow aspirates of high-risk NB patients, characterized by different MYCN amplification status. Interestingly, in one patient NB cells were poorly responsive to IFNγ stimulation, pointing out that responsiveness to IFNγ might represent a further element of heterogeneity in metastatic neuroblasts. Finally, we document the presence of lymphocytes expressing the PD-1 receptor in NB-infiltrated bone marrow of patients. PD-1 pos cells are mainly represented by αβ T cells, but also include small populations of γδ T cells and NK cells. Moreover, PD-1 pos T cells have a higher expression of activation markers. Overall, our data show that a PD-L1-mediated immune resistance mechanism occurs in metastatic neuroblasts and provide a biological rationale for blocking the PD-1/PD-Ls axis in future combined immunotherapeutic approaches.