Abstract 2703: Leukocyte complexity in human breast cancer and response to chemotherapy
Authors: Ruffell Brian , DeNardo David G. , Au Alfred , Rugo Hope S. , Hwang E. Shelley , Coussens Lisa M. 
Published: June 2012

Despite the use of immune based biomarkers that predict outcomes for women with breast cancer (BC), leukocyte complexity in BCs remains poorly described, with scant information available regarding effects of cytotoxic therapy on leukocytic infiltrates. To evaluate leukocyte complexity and nature of the immune microenvironment in BCs, and to determine if chemotherapy (CTX) alters leukocyte density or phenotype, we evaluated BC tumor tissue, as compared to “normal” adjacent breast tissue, from women who had either received neoadjuvant CTX or had not received CTX prior to surgery. Tissues were evaluated immediately following surgical resection by polychromatic flow cytometry, as well as by immunohistochemical evaluation of tissue sections, or quantitative real-time PCR for mRNA expression. Independent of neoadjuvant CTX, myeloid-lineage leukocytes represented the dominant immune population in adjacent normal tissue. Tumor tissue from treated- and untreated patients contained significantly higher infiltration of activated CD4+ and CD8+ T cells, as compared to adjacent normal tissue. CD8+ T cells in treated tumors comprised a larger percent of the T cell infiltrate, corresponding to increased expression of CD3∈, CD8α, and cytotoxic molecules (granzyme B, perforin, granulysin) indicating higher infiltration by functional cytotoxic T cells. Importantly, adjacent normal and tumor tissue from women that had received neoadjuvant CTX contained significantly higher levels of infiltrating myeloid cells (macrophages, dendritic cells, neutrophils and mast cells), as compared to untreated women. Furthermore, mRNA expression analysis revealed corresponding increases in expression of myeloid-associated genes CD68, CD86, and HLA-DR, and evidence of induction of an immunosuppressive microenvironment, e.g., increased expression of IL-10 and -12β, and reduced expression of IL-12α. To determine if these changes were a direct response to CTX, or instead a response to CTX-induced cell death, we evaluated multiple human BC cell lines in culture following exposure to either Paclitaxel or Cisplatin and found CTX induced mRNA expression of cytokines and chemokines involved in myeloid recruitment. Using a murine model of mammary carcinogenesis, we revealed that, as predicted from these clinical data, CTX induced myeloid recruitment into mammary tumors, and that these tumor-promoting leukocytes in part regulated the response to cytotoxic therapy. Together, these data indicate that neoadjuvant chemotherapy leads to simultaneous induction of both a T cell-mediated anti-tumor immune response and recruitment of immunosuppressive and protumor myeloid cells that blunt response to cytotoxic therapy. Therapeutic strategies targeting these immunosuppressive and tumor-promoting immune cells may improve treatment efficacy and extend survival for women with BC.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2703. doi:10.1158/1538-7445.AM2011-2703