Abstract
BackgroundProgrammed death-1 ligand-1 (PD-L1) an important cancer biomarker that can suppress the immune system and its high expression is often reported to be related with increased tumor aggressiveness in some cancers. Here, we examined and evaluated PD-L1 expression in patients with malignant salivary gland tumor. Moreover, the relationship between PD-L1 immunolocalization and clinical pathological features, as well as the prognosis of malignant salivary gland tumors was investigated.MethodsWe examined PD-L1expression in 47 patients with malignant salivary gland tumor by immunohistochemical staining. PD-L1 positivity was defined as ≥5% in tumor cell membrane and evaluated according to three categories (0% = 0, < 5% = 1, ≥5% = 2) in tumor-infiltrating mononuclear cells (TIMCs). Fisher’s exact test was used to compare between PD-L1 expression and clinico-pathological features, and Kaplan–Meier method was used to estimate the distribution of OS by PD-L1 positivity.ResultsPD-L1 expression was detected in 51.1% of malignant salivary gland tumor tissues. No association was observed between PD-L1 immunolocalization in tumor and patient gender, or age. However, PD-L1 immunodetection of tumor cell membranes was significantly associated to stage, recurrence or metastasis after surgery, and patient outcome. On the other hand, PD-L1 immunodetection of tumor-infiltrating mononuclear cells (TIMCs) was significantly associated to recurrence or metastasis after surgery, and patient outcome. PD-L1 positivity in both tumor cell membrane and TIMCs was associated with shorter overall survival (OS) (p = 0.002 and p = 0.016, respectively).ConclusionThese findings suggested that patients with PD-L1 positive tumors or TIMCs appear to have poor clinical outcomes in malignant salivary gland tumors.
Highlights
Programmed death-1 ligand-1 (PD-L1) an important cancer biomarker that can suppress the immune system and its high expression is often reported to be related with increased tumor aggressiveness in some cancers
Two binding ligands have been identified for PD-1, Programmed death-1 ligand-1 (PD-L1, known as B7-H1) and PD-L2, and both belong to the B7 family [10, 11]
PD-L1 is expressed in resting T cells, B cells, dendritic cells (DCs) and in various tumor cells; and the formation of PD-1 and PD-L1 receptor-ligand complex leads to the inhibition of the cytotoxic T cells and induces special apoptosis of T cells, which results in tumor immune escape [12,13,14]
Summary
Programmed death-1 ligand-1 (PD-L1) an important cancer biomarker that can suppress the immune system and its high expression is often reported to be related with increased tumor aggressiveness in some cancers. The incidence of malignant salivary gland tumors is relatively low compared to other head and neck cancers. It is well known that development and prognosis of malignant tumors are closely associated with host immune functions. Programmed death-1 (PD-1) is a co-stimulatory molecule that functions as an immune checkpoint. It is expressed on T cells and pro-B cells, and negatively regulates T cell activation and responses [9]. The levels and clinical significance of PD-L1 expression in malignant salivary gland tumor is still unknown
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