AUTHOR=Lacher Markus D. , Bauer Gerhard , Fury Brian , Graeve Sanne , Fledderman Emily L. , Petrie Tye D. , Coleal-Bergum Dane P. , Hackett Tia , Perotti Nicholas H. , Kong Ying Y. , Kwok William W. , Wagner Joseph P. , Wiseman Charles L. , Williams William V. 

TITLE=SV-BR-1-GM, a Clinically Effective GM-CSF-Secreting Breast Cancer Cell Line, Expresses an Immune Signature and Directly Activates CD4+ T Lymphocytes

JOURNAL=Frontiers in Immunology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2018.00776

DOI=10.3389/fimmu.2018.00776

ISSN=1664-3224

ABSTRACT=<p>Targeted cancer immunotherapy with irradiated, granulocyte–macrophage colony-stimulating factor (GM-CSF)-secreting, allogeneic cancer cell lines has been an effective approach to reduce tumor burden in several patients. It is generally assumed that to be effective, these cell lines need to express immunogenic antigens coexpressed in patient tumor cells, and antigen-presenting cells need to take up such antigens then present them to patient T cells. We have previously reported that, in a phase I pilot study (<uri xlink:href="http://ClinicalTrials.gov" xmlns:xlink="http://www.w3.org/1999/xlink">ClinicalTrials.gov</uri> NCT00095862), a subject with stage IV breast cancer experienced substantial regression of breast, lung, and brain lesions following inoculation with clinical formulations of SV-BR-1-GM, a GM-CSF-secreting breast tumor cell line. To identify diagnostic features permitting the prospective identification of patients likely to benefit from SV-BR-1-GM, we conducted a molecular analysis of the SV-BR-1-GM cell line and of patient-derived blood, as well as a tumor specimen. Compared to normal human breast cells, SV-BR-1-GM cells overexpress genes encoding tumor-associated antigens (TAAs) such as PRAME, a cancer/testis antigen. Curiously, despite its presumptive breast epithelial origin, the cell line expresses major histocompatibility complex (MHC) class II genes (<italic>HLA-DRA, HLA-DRB3, HLA-DMA, HLA-DMB</italic>), in addition to several other factors known to play immunostimulatory roles. These factors include MHC class I components (<italic>B2M, HLA-A, HLA-B</italic>), <italic>ADA</italic> (encoding adenosine deaminase), <italic>ADGRE5</italic> (<italic>CD97</italic>), <italic>CD58</italic> (<italic>LFA3</italic>), <italic>CD74</italic> (encoding invariant chain and CLIP), <italic>CD83, CXCL8</italic> (<italic>IL8</italic>), <italic>CXCL16, HLA-F, IL6, IL18</italic>, and <italic>KITLG</italic>. Moreover, both SV-BR-1-GM cells and the responding study subject carried an <italic>HLA-DRB3*02:02</italic> allele, raising the question of whether SV-BR-1-GM cells can directly present endogenous antigens to T cells, thereby inducing a tumor-directed immune response. In support of this, SV-BR-1-GM cells (which also carry the <italic>HLA-DRB3*01:01</italic> allele) treated with yellow fever virus (YFV) envelope (Env) 43–59 peptides reactivated YFV-DRB3*01:01-specific CD4<sup>+</sup> T cells. Thus, the partial HLA allele match between SV-BR-1-GM and the clinical responder might have enabled patient T lymphocytes to directly recognize SV-BR-1-GM TAAs as presented on SV-BR-1-GM MHCs. Taken together, our findings are consistent with a potentially unique mechanism of action by which SV-BR-1-GM cells can act as APCs for previously primed CD4<sup>+</sup> T cells.</p>