Curcumin converts Foxp3+ regulatory T cells to T helper 1 cells in patients with lung cancer.

The regulatory T cells (Treg) play an important role in the tumor tolerance. The methods to regulate the Treg population in cancer-bearing hosts are limited currently. The effect of curcumin on inhibiting cancer has been recognized, but the mechanism remains elusive. This study tests a hypothesis that administration of curcumin down regulates Tregs in lung cancer (LC) patients. In this study, a group of LC patients was treated with curcumin. The peripheral Tregs and T helper (Th) 1 cells were analyzed by flow cytometry. The mechanism by which curcumin regulated the Tregs was observed by cell culture approaches. The results showed that the frequency of peripheral Treg was markedly higher in LC patients than that in healthy subjects, which was suppressed after treating with curcumin for 2 weeks. The peripheral Th1 cells were increased in LC patients after the curcumin therapy. The data of the in vitro experiments showed that curcumin converted the LC patient-isolated Tregs to Th1 cells via repressing the gene transcription of forkhead protein-3 and increasing the expression of interferon-γ. In conclusion, curcumin can convert LC patient-isolated Tregs to Th1 cells. The results suggest that curcumin may improve the antitumor immunity by regulating the tumor specific immune tolerance.