Abstract P5-04-06: Soluble factors from activated immune cells induce epithelial mesenchymal transition in inflammatory breast cancer cells

Abstract

Rationale: Inflammatory breast cancer (IBC) is the most insidious form of locally advanced disease. Emerging evidence suggests that host factors in the microenviromement may interact with underlying IBC genetics to promote the aggressive nature of the tumor. An integral part of the metastatic process involves epithelial to mesenchymal transition (EMT) where primary breast cancer cells gain motility and stem cell features that allow distant seeding. Interestingly, the IBC consortium microarray data found no clear evidence for EMT in IBC tumor tissues. However, it is unknown if soluble factors secreted by activated immune cells mediate EMT in the IBC microenvironment that may account for the absence of EMT in studies of the tumor cells themselves. Therefore, we tested whether the conditioned media of activated immune cells were capable of inducing EMT in IBC cells. Methods: Conditioned media (CM) were generated using healthy donor peripheral blood mononuclear cells that were activated with anti-CD3 antibody immobilized to plastic and soluble anti-CD28 antibody to activate T cells through the T-cell receptor (TCR) or left unstimulated for 48 hours. Thereafter, CM from each of the cultures was harvested and filtered. Next, 48-hour pre-seeded SUM149 IBC cells were grown in culture medium consisting of 25% CM and 75% IBC culture medium for an additional 2 days. Unconditioned media and TGF-β were used as negative and positive controls, respectively for EMT. Following treatment with CM, RNA was extracted from the target cells and analyzed for the presence of EMT-related transcription factors (EMT-TF) and markers of epithelial and mesenchymal states by TaqMan® qRT-PCR. Subsequently, a panel of 24 genes was tested on 4 IBC cell lines (SUM149, SUM190, KPL4 and IBC-3) and 5 non-IBC cell lines (MCF-10a, MCF-7, MDA-231, and MDA-453) treated with immune-activated CM using the Fluidigm® Dynamic Array integrated fluidic circuit (“chip”) gene expression platform which allows for the simultaneous quantification of 2,304 data points using TaqMan® assays. Formalin-fixed, paraffin embedded blocks were prepared from trypsinized cells for immunohistochemical (IHC) staining to detect E-cadherin and vimentin expression. Results: SUM149 cells cultured in the presence of TCR-activated CM for two days showed upregulation in EMT-TFs (SNAIL1, ZEB1, and TG2), vimentin and fibronectin by qRT-PCR. IHC staining showed increases in both vimentin and E-cadherin expression after 48-hour exposure to anti-TCR CM. Fluidigm® gene expression analysis of multiple cell lines exposed to anti-TCR CM showed that E-cadherin expression was unchanged or slightly decreased in non-IBC cell lines, whereas 3 of 4 IBC cell lines showed an increase in E-cadherin. Discussion: These data suggest that soluble factors secreted by activated immune cells are capable of inducing EMT in IBC cells and may mediate the persistent E-cadherin expression observed in IBC. Such processes may contribute to the highly aggressive nature of the disease; however, an immune competent in vivo model is warranted to fully understand the implications of these findings. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-04-06.