As PI3Kδ inhibition led to a significant reduction in FOXP3 transcript levels in the tumour samples (Fig. 1b), we assessed Treg cell levels in tumour tissue by immunohistochemistry, hypothesizing that the duration between cessation of treatment and tumour resection might be a critical factor influencing Treg cell abundance, owing to the relatively short half-life of the compound. This evidence concerns the gene FOXP3 and neoplasm.