The Expression Pattern and Clinical Significance of the Immune Checkpoint Regulator VISTA in Human Breast Cancer.

Xiaoxue Xie,Zhongyuan Shi,Chenxin Qie,Jingwei Jiang,Xinlei Hu,Wenting Chen,Jun Liu,Yan Wang,Junying Zhang,Li Wang,Wanmei Liu

doi:10.3389/fimmu.2020.563044

Abstract

BackgroundImmunotherapies targeting CTLA-4 and PD-1 have elicited promising responses in a variety of cancers. However, the relatively low response rates warrant the identification of additional immunosuppressive pathways. V domain immunoglobulin suppressor of T cell activation (VISTA) plays a critical role in antitumor immunity and is a valuable target in cancer immunotherapy.MethodsHere, we used single-cell RNA-seq to analyze the gene expression levels of 14897 cells from a breast cancer sample and its paired 7,320 normal cells. Then, we validated the protein expression of immune checkpoint molecules (VISTA, PD-1, PD-L1, TIGIT, TIM3, and LAG3) in 324 human breast cancer samples by immunohistochemistry and quantitative immunofluorescence (QIF) approaches.ResultsSingle cell RNA-seq results show a higher level of immune checkpoint VISTA expression in breast cancer tissue compared to adjacent normal tissue. We also found that VISTA expressed highest in breast cancer tissue than other immune-checkpoints. Immunohistochemical results showed that VISTA was detected with a membranous/cytoplasmic staining pattern in intratumoral immune cells and breast cancer cells. Additionally, VISTA was positively correlated with pathological grade, lymph node status and the levels of PD-1 according to the chi-square test or Fisher’s test. Furthermore, VISTA expression was higher in CD68+ tumor-associated macrophages (TAMs) than in CD4+ T cells, CD8+ cytotoxic T cells or CD20+ B cells.ConclusionsThese findings therefore support the immunoregulatory role of VISTA in breast cancer and indicate that targeting VISTA may benefit breast cancer immunotherapy.

Highlights

Immunotherapies targeting CTLA-4 and PD-1 have elicited promising responses in a variety of cancers
VISTA was positively correlated with pathological grade, lymph node status and the levels of PD-1 according to the chi-square test or Fisher’s test
VISTA expression was higher in CD68+ tumor-associated macrophages (TAMs) than in CD4+ T cells, CD8+ cytotoxic T cells or CD20+ B cells

Summary

Introduction

Immunotherapies targeting CTLA-4 and PD-1 have elicited promising responses in a variety of cancers. V domain immunoglobulin suppressor of T cell activation (VISTA) plays a critical role in antitumor immunity and is a valuable target in cancer immunotherapy. Current mainstream treatments for breast cancer include surgery, radiation therapy, chemotherapy, hormone therapy and targeted therapy [2] These therapies are not efficacious in all types of breast cancer due to a variety of resistance mechanisms and toxicity. V-domain immunoglobulin (Ig) suppressor of T cell activation (VISTA) is a B7-family immune checkpoint protein that plays a multifaceted role in regulating peripheral tolerance, autoimmunity, inflammation, and antitumor immunity [10]. The extracellular domain of VISTA is homologous to that of PD-L1 [11, 12], our previous study indicates that the VISTA and PD-1/PD-L1 checkpoint pathways are functionally distinct and that they nonredundantly regulate T cell function and the antitumor immune response [12]. Among melanoma and prostate cancer patients treated with ipilimumab, VISTA expression is significantly upregulated on CD4+ T cells, CD8+ T cells and CD68+ macrophages, indicating that VISTA may contribute to mechanisms of resistance to checkpoint inhibitor therapies in these cancers [23, 24]

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Discussion

Conclusion