Pancreatic neuroendocrine tumors (PanNETs) are rare malignancies with heterogeneous clinical courses requiring novel prognosticators and therapies. B7 family molecules have an important role in various cancers; however, these have not been distinguished in PanNETs.
To investigate the expression and clinical significance of programmed death ligand-1 (PD-L1), programmed death ligand-2 (PD-L2), B7 homolog 3 (B7-H3), B7 homolog 4 (B7-H4), and V-domain immunoglobulin suppressor of T-cell activation (VISTA) in 182 PanNETs (with a high proportion of functioning versus nonfunctioning PanNETs: 51% versus 49%).
Molecules were immunostained by using tissue microarrays from 182 patients with grade 1/2 PanNETs. VISTA-positive microvessel density (VISTA+ MVD) was evaluated in 4 high-power fields (HPFs) (×200) and mean count was calculated; immune cells with 1% or greater VISTA staining were considered positive. PD-L1 tumoral expression was considered positive in samples with 5% or more membranous staining. Tumoral VISTA, stromal PD-L1, PD-L2, B7-H3, and B7-H4 expression were deemed positive if any staining was observed.
VISTA+ MVD was high (≥10.8/HPF) in 45 patients (25%), while VISTA stained positively on immune and tumor cells in 121 (66%) and 0 patients, respectively. Positive PD-L1 tumoral and stromal expression was observed in 23 (13%) and 0 patients, with positive B7-H3 expression in 76 (42%) and 98 (54%) patients, respectively, in these cells; PD-L2 and B7-H4 were not detected. PD-L1 positivity rate was high in functioning PanNETs. Stromal B7-H3 and high VISTA+ MVD correlated with unfavorable clinicopathologic features. Moreover, high VISTA+ MVD was an independent predictor of shorter progression-free survival.
VISTA may serve as a prognosticator and immunotherapeutic target for patients with pancreatic neuroendocrine tumor (PanNET).
This work was supported by grants from the Chinese Academy of Medical Sciences Initiative for Innovative Medicine (CAMS-2016-I2M-1–001), National Scientific Data Sharing Platform for Population and Health (NCMI–YF01N–201906), and the National Natural Science Foundation of China (Nos. 81472326, 81672648 and 82001664). The funders of the study had no role in the design of the study, in the collection, analysis, and interpretation of data, or in writing the manuscript.
The authors have no relevant financial interest in the products or companies described in this article.