PD L1 expression and CD274 gene alteration in triple negative breast cancer: implication for prognostic biomarker
PurposeTo estimate the therapeutic potential of PD L1 inhibition in breast cancer, we evaluated the prevalence and significance of PD L1 protein expression with a validated antibody and CD274 gene alternation in a large cohort of triple negative breast cancer (TNBC) and correlated with clinicopathological data and patients overall survival.MethodsImmunohistochemistry and in situ mRNA hybridization was used to detect PD L1 protein and mRNA expression in tumor tissues from 183 TNBC patients respectively. Fluorescence in situ hybridization analysis was performed on PD L1 strong expression samples to assess copy number on chromosome 9p24.1 of CD274 gene.ResultsExpression of PD L1 by immune cells was observed in 4.9 of TNBC, while expression by tumor cells accounted for 8.7 There was a high concordance in PD L1 protein expression and PDL1 mRNA expression. Samples with PD L1 strong expression were found to have a CD274 gene copy number gain. PD L1 expression was correlated with higher tumor grade, but was independent of menopausal status, lymph nodes metastasis, histological subtype and tumor size. In addition, we used precise stratification of PD L1 expression on tumor or immune cells of certain breast cancer subtype and suggested that patients with PD L1 expression in basal like tumors by immune cells or with CD274 gene copy number gain had a longer disease specific overall survival.ConclusionsOur findings may promote the more precise analysis of PD L1 expression in breast cancer and aid the selection of patients who may benefit from immune therapy.
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