Figure S1: HER2high cells are susceptible to NK-mediated ADCC, but not HER2369-377-sensitized CD8+ T-cell-mediated cytotoxicity. Figure S2: Cell line-specific IFN-γ receptor expression and impact of IFN-γ dose titration on MHC class I expression. Figure S3: Comparative effects of trastuzumab or lapatinib in conjunction with Th1 cytokines on class I and HER2 expression. Table S1: Demographic, tumor, and HLA-A typing characteristics of HER2pos-DCIS patients utilized for in vitro sensitization, recognition, and cytotoxicity assays.
ARTICLE ABSTRACT
Vaccination strategies incorporating the immunodominant HLA-A2–restricted HER2/neu-derived peptide 369–377 (HER2369–377) are increasingly utilized in HER2/neu-expressing cancer patients. The failure of postvaccination HER2369–377-specific CD8+ T cells to recognize HLA-A2posHER2/neu-expressing cells in vitro, however, has been attributed to impaired MHC class I/HLA-A2 presentation observed in HER2/neu-overexpressing tumors. We reconcile this controversy by demonstrating that HER2369–377 is directly recognized by high functional-avidity HER2369–377-specific CD8+ T cells—either genetically modified to express a novel HER2369–377 TCR or sensitized using HER2369–377-pulsed type 1–polarized dendritic cells (DC1)—on class I–abundant HER2low, but not class I–deficient HER2high, cancer cells. Importantly, a critical cooperation between CD4+ T-helper type-1 (Th1) cytokines IFNγ/TNFα and HER2/neu-targeted antibody trastuzumab is necessary to restore class I expression in HER2high cancers, thereby facilitating recognition and lysis of these cells by HER2369–377-specific CD8+ T cells. Concomitant induction of PD-L1 on HER2/neu-expressing cells by IFNγ/TNF and trastuzumab, however, has minimal impact on DC1-sensitized HER2369–377-CD8+ T-cell–mediated cytotoxicity. Although activation of EGFR and HER3 signaling significantly abrogates IFNγ/TNFα and trastuzumab-induced class I restoration, EGFR/HER3 receptor blockade rescues class I expression and ensuing HER2369–377-CD8+ cytotoxicity of HER2/neu-expressing cells. Thus, combinations of CD4+ Th1 immune interventions and multivalent targeting of HER family members may be required for optimal anti-HER2/neu CD8+ T-cell–directed immunotherapy. Cancer Immunol Res; 3(5); 455–63. ©2015 AACR.
