Abstract
Ovarian cancer is an immune reactive malignancy with a complex immune suppressive network that blunts successful immune eradication. This suppressive microenvironment may be mediated by recruitment or induction of CD4+ regulatory T cells (Tregs). Our study sought to investigate the association of tumor-infiltrating CD4+CD25+FOXP3+ Tregs, and other immune factors, with clinical outcome in serous ovarian cancer patients. We performed immunofluorescence and quantification of intraepithelial tumor-infiltrating triple positive Tregs (CD4+CD25+FOXP3+), as well as CD4+CD25+FOXP3-, CD3+ and CD8+ T cells in tumor specimens from 52 patients with high stage serous ovarian carcinoma. Thirty-one of the patients had good survival (i.e. > 60 months) and 21 had poor survival of < 18 months. Total cell counts as well as cell ratios were compared among these two outcome groups. The total numbers of CD4+CD25+FOXP3+ Tregs, CD4+CD25+FOXP3-, CD3+ and CD8+ cells were not significantly different between the groups. However, higher ratios of CD8+/CD4+CD25+FOXP3+ Treg, CD8+/CD4+ and CD8/CD4+CD25+FOXP3- cells were seen in the good outcome group when compared to the patients with poor outcome. These data show for the first time that the ratios of CD8+ to both CD4+CD25+FOXP3+ Tregs and CD4+CD25+FOXP3- T cells are associated with disease outcome in ovarian cancer. The association being apparent in ratios rather than absolute count of T cells suggests that the effector/suppressor ratio may be a more important indicator of outcome than individual cell count. Thus, immunotherapy strategies that modify the ratio of CD4+CD25+FOXP3+ Tregs or CD4+CD25+FOXP3- T cells to CD8+ effector cells may be useful in improving outcomes in ovarian cancer.
Highlights
Ovarian cancer has the highest mortality rate of cancers exclusive to women
Subsequent studies have refined our understanding of intra-tumoral T cells, such as the work by Sato et al, that showed patients who had high levels of infiltrating cytotoxic T lymphocytes (CTL) had a median survival of 55 months versus those with few or no CTL who had a survival of 26 months [8]
Given that prior studies examined and enumerated nonrandom T cell enriched fields, we examined the validity of this approach by assessing the correlation between the total CD4+CD25+forkhead box P3 (FOXP3)+ Treg count across all 20 fields and the MAX1 and MAX3 counts
Summary
Ovarian cancer has the highest mortality rate of cancers exclusive to women. Despite many therapeutic efforts utilizing new chemotherapies, the cure rate has not improved substantially in decades [1,2,3]. It is well known that clinical outcomes in ovarian cancer are quite heterogeneous and not predicted by standard clinical and pathologic characteristics (e.g., grade, tumor histology) [4,5,6]. This suggests that there may be other tumor microenvironment or host characteristics with a dominant role in survival. The antigens to which the patients are naturally responding are being systematically studied [10,11] These findings show that anti-tumor immunity is elicited against ovarian cancers and impacts the clinical course of the disease. It is apparent that the anti-tumor immunity is counterbalanced by an immune suppressive microenvironment [7,12,13,14,15]
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