In this study, we utilized 11 previously constructed tissue microarray (TMA) blocks containing formalin fixed, paraffin-embedded primary tumor tissue from 276 patients enrolled in the SBG0102 study, provided by the DBCG Tumor Tissue Data Repository. The TMAs contain two 2 mm cores of primary breast cancer tissue per patient, as previously described.40 (link) Immunohistochemical (IHC) staining for CD8 (clone C8/144B, Dako), PD-1 (clone NAT105, CellMarque), LAG3 (clone 17B4, Abcam), FOXP3 (clone 236A/E7, Abcam) and CD163 (clone 10D6, Leica Biosystems) was performed as per manufacturer’s protocol using the Ventana Discovery Ultra staining platform at the Genetic Pathology Evaluation Center (Vancouver, Canada). PD-L1 staining using the SP142 clone (Roche) was performed following manufacturer’s instructions at the Victoria Deeley Research Center (Victoria, Canada).
Staining and scoring of the standard breast cancer biomarkers ER, PR, and HER2 had been performed in connection with previous publications following published methods at the Genetic Pathology Evaluation Center, Vancouver, Canada.40–43 (link)Slides were scanned and digitized on the Aperio AT2 scanner at 20X magnification. Representative photomicrographs are shown in supplementary Figure S1.
Staining and scoring of the standard breast cancer biomarkers ER, PR, and HER2 had been performed in connection with previous publications following published methods at the Genetic Pathology Evaluation Center, Vancouver, Canada.40–43 (link)Slides were scanned and digitized on the Aperio AT2 scanner at 20X magnification. Representative photomicrographs are shown in supplementary Figure S1.