FOXP3 and cancer: Tumor-infiltrating T cells play an important role in tumor progression4; a high density of tumor-infiltrating T cells has been associated with improved prognosis.5,6 We showed in a previous study that CD3+, CD45RO+, CD8+, FOXP3+, and Granzyme B+ T cells were significantly associated with cancer-specific survival.7 T-cell densities also have potential as a predictive marker for response to adjuvant chemotherapy.8,9 In these studies,6, , –9 T cells were assessed using tissue sections of surgical resection specimens of treatment-naïve patients.