Characterization of Tumor Infiltrating Lymphocytes in Human Breast Cancer by Infrared Imaging

Abstract

In human breast cancer spatially organized Tumor Infiltrating Lymphocytes (TILs) have been associated with effective therapeutic responses and favorable clinical outcomes.1-3 This study investigates the potential for using InfraRed (IR) imaging to identify and characterize infiltrating lymphocytes in breast tumors, focusing on CD4 +, CD8+ T lymphocytes and B lymphocytes (CD20+). Fourier Transform InfraRed (FTIR) spectroscopy coupled with microscopy is an emerging tool in cancer research and diagnosis.4,5 IR imaging can probe the chemical composition and molecular structure of cells and tissues, thereby providing a global and unique signature for all cellular constituents. Compared with standard techniques used for identification and characterization of immune cells in tissue sections, IR imaging has numerous advantages, including no requirement for staining or automation. In this study, infrared spectra of lymphocyte subpopulations were recorded for lymphocytes in FFPE tissue sections from tonsils and breast tumors. Samples were deposited on a BaF2 window and the spectroscopic imaging data acquired in transmission mode using a Hyperion imaging system (Bruker) equipped with a focal plane array detector. The specific lymphocyte subpopulations present in each region were evaluated using hematoxyline & eosin (HE) and immunofluorescent (IF) staining of adjacent tissue sections. Statistical analyses indicate that IR spectra obtained from the CD4 + , CD8+ or CD20+ lymphocyte subpopulations in tonsils are significantly different and identifiable relative to the other subpopulations. These data suggest that FTIR imaging can be used to identify specific lymphocyte subpopulations in tissues based on their spectral features. Our current work is testing this hypothesis to examine immune infiltrates in breast tumor tissue and these data will be presented at the meeting.