Abstract A18: Investigating the differential expressions of miRNAs and programmed-death-ligand-1 related to the T-bet positive tumor-infiltrating lymphocytes in axillary-node-negative breast cancer
Authors: Lee Minji , Mulligan Anna-Marie , Bull Shelley , Pinnaduwage Dushanti , Andrulis Irene 
Published: October 2016

Axillary lymph node-negative (ANN) breast cancer (BC) patients generally have a good prognosis; however, 20-30% of ANN patients will experience recurrence. To identify biomarkers that distinguish ANN patients who may benefit from systemic therapy we have been studying characteristics of the breast tumor cells and the tumor microenvironment. We have found that tumor-infiltrating lymphocytes (TILs) that express T-bet (T-box transcription factor) are associated with poor prognosis features such as high grade, hormone receptor negativity and basal subtype. Despite these adverse clinical-pathologic characteristics, T-bet+ TILs cells are associated with a favorable outcome. T-bet is essential for Th1 development and IFN-γ production. To investigate how T-bet+ TILs influence the BC suppression, we are examining molecular differences in T-bet+/high and T-bet-/low tumors including expression of tumor miRNA expression profiles and expression of Programmed-Death-Ligand-1 (PD-L1). Tumors expressing PD-L1 inhibit Programmed-Death-receptor-1-(PD-1)-expressing TILs and evade immune surveillance. Interestingly, PD-L1 is induced by IFNγ, the hallmark cytokine of the T-bet+ TILs, which suggests a potential relationship between the tumor PD-L1 and T-bet+ TILs. Microdissected, formalin-fixed, paraffin-embedded (FFPE) samples of 35 T-bet+/high and 35 T-bet-/low ANN BC tumors are being used to identify the differentially-expressed miRNAs via miRNA sequencing. The sufficiency of the FFPE samples as the miRNA source was confirmed by quantifying miRNA expressions in the 3-5 paired frozen and FFPE samples, and observing the expressions to be highly correlated with both qPCR (r=0.81) and miRNA sequencing (rs=0.73). After identifying the differentially-expressed miRNAs via miRNA sequencing, these miRNAs will be validated via qPCR in both the original and independent BC tumor set. Based on the genes and molecular pathways the validated miRNA(s) may regulate, appropriate in vitro functional assays will be conducted to examine their roles in cellular proliferation, migration and invasion. Furthermore, PD-L1 mRNA expression has been evaluated in 107 ANN tumors and correlations with clinico-pathological characteristics will be determined. Identifying the tumor miRNA(s) associated with T-bet+ TILs and studying their functions may indicate differences between T-bet+/high and T-bet-/low tumors that can be used to improve the prognosis of ANN BC. Characterizing the tumor PD-L1 expression based on T-bet+ TILs and the clinical data may distinguish a subset of ANN BC patients who may benefit from the PD-L1 blockade therapy.

Citation Format: Minji Lee, Anna-Marie Mulligan, Shelley Bull, Dushanti Pinnaduwage, Irene Andrulis. Investigating the differential expressions of miRNAs and programmed-death-ligand-1 related to the T-bet positive tumor-infiltrating lymphocytes in axillary-node-negative breast cancer. [abstract]. In: Proceedings of the AACR Special Conference: Function of Tumor Microenvironment in Cancer Progression; 2016 Jan 7–10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2016;76(15 Suppl):Abstract nr A18.