CD4+ T cells infiltrating breast tumors exhibit altered expression of T cell immune response genes in comparison with their counterparts from the lymph node and blood

Equeter C, El Ouriaghli F, Haibe-Kains B, Stamatopoulos B, André F, Lallemand F, Filippov V, Larsimont D, Sotiriou C, Willard-Gallo K

We initiated a study to understand the functional defects in T cells infiltrating breast tumors by comparing purified CD4+ T cells from the primary tumor, axillary lymph node and peripheral blood of individual patients with ER+ and ER− invasive ductal breast carcinoma. CD4+ T cells were isolated after tissue digestion with collagenase IV and the extracted RNA was analyzed on Affymetrix Human GeneChip© Arrays. Unsupervised analysis revealed that the greatest differences in gene expression were characteristic of the tissue examined rather than the patient. Interestingly, the profiles of gene expression for CD4+ T cells from patients compared with age- and sex-matched controls were quite similar. However, patient’s CD4+ T cells isolated from the tumor were strikingly different from their blood. This comparative analysis revealed that the T cell receptor (TCR/CD3) and IL-2 signaling pathways were downregulated while the VEGF and TGFβ pathways were upregulated in the tumor infiltrating T cells. These effects do not appear to be due to an increased presence of regulatory CD4+ T cells since FOXP3 expression was similar in cells isolated from the three tissues. Preliminary real-time RT-PCR experiments confirm the downregulation of several genes in the TCR/CD3 as well as in the IL-2 pathways. Flow cytometric analysis revealed that TCR/CD3 surface proteins were also downregulated, with the greatest difference observed between CD4+ T cells from the tumor relative to the blood and to a lesser extent the lymph node. Ongoing experiments have been designed to further our understanding of changes in CD4+ T cell gene expression resulting from their interactions with other cells present in the tumor microenvironment.