Tumor-infiltrating CD8+ lymphocytes predict clinical outcome in breast cancer.

Breast carcinomas are often infiltrated by inflammatory cells, particularly macrophages and T lymphocytes, but the significance of these cells remains unclear. One possible role of these inflammatory cells is that they represent a cell-mediated immune response against the carcinoma. CD8(+) lymphocytes are a known crucial component of cell-mediated immunity. The purpose of this study was to explore the prognostic value of tumor-infiltrating CD8(+) cytotoxic lymphocytes in breast cancer. Tumor-infiltrating CD8(+) lymphocytes were assessed by immunohistochemical staining of tissue microarray cores from 1,334 unselected breast tumors from patients with long-term follow-up. The number of CD8(+) T cells was counted in tumor nests (intratumoral), in stroma adjacent to tumor cells, and in stroma distant to tumor cells, and their relationship with clinical outcome was determined. The total number of CD8(+) cells was positively correlated with tumor grade (r(s) = 0.20; P < .001) and inversely correlated with patient's age at diagnosis, estrogen receptor-alpha (ER-α), and progesterone receptor (PgR) expression (Mann-Whitney U test, P < .001). The total patient cohort was randomly divided into two separate training and validation sets before performing univariate survival analysis. Total number and distant stromal CD8(+) lymphocytes were associated with better patient survival (P = .041 and P < .001, respectively) in the training set. In multivariate analysis, total CD8(+) T-cell count was an independent prognostic factor in both training and validation sets. These results suggest that tumor-infiltrating CD8(+) T lymphocytes have antitumor activity as judged by their favorable effect on patients' survival and could potentially be exploited in the treatment of breast cancer.

An evaluation of the clinical significance of FOXP3+ infiltrating cells in human breast cancer.

Studies in mice have shown that thymic-derived CD4+ CD25+ regulatory T cells (T reg; FOXP3(+) lymphocytes) inhibit an antitumour immune response. Additional studies have also reported that the T reg population increases in peripheral blood and tumour tissues from patients with cancer. However, the relationship between the T reg population and the patient prognosis remains controversial. Our aim was to determine the prognostic value of T reg cell density in breast cancer using immunohistochemical assessment of FOXP3, which has been shown to be the optimal marker for T regs. Tissue microarrays were used, and the density of FOXP3(+) cells was determined in a series of 1445 cases of well-characterised primary invasive breast carcinoma cases with long-term follow up. FOXP3(+) cell numbers were counted in tumour nests, in tumour-adjacent stroma, and in distant stroma. The total number of FOXP3(+) cells significantly correlated with higher tumour grade (r (s) = 0.37, P < 0.001) and ER negativity (Mann-Whitney U test, P < 0.001). In addition, FOXP3 infiltration positively correlated with HER2 expression and basal phenotype subclass. On univariate analysis, FOXP3(+) cells were associated with a worse prognosis (P = 0.012, log rank = 6.36). This association was found for intratumoural FOXP3(+) and for tumour-adjacent stromal FOXP3(+)-cells (tumour-cell associated FOXP3, P = 0.001 and log rank 10.35). However, the number of FOXP3(+) cells was not found to be an independent prognostic factor in multivariate analysis. We therefore conclude that FOXP3(+) infiltrating cells do not have a dominant role in breast cancer prognosis and suggest that other inflammatory cell subsets may be more critical variables.