Age-related changes in CD4+CD25+FOXP3+ regulatory T cells and their relationship with lung cancer

Objectives CD4(+)CD25(+)FOXP3(+) regulatory T cells (Treg) inhibit the anti-tumour immune response and reduce the effect of cancer immunotherapy. Although studies have demonstrated that the number and suppressive activity of Treg increase with age, it is not clear whether these changes correlate with a higher incidence of tumours in the elderly. This study was designed to explore the relationship between increase in CD4(+)CD25(+)FOXP3(+) Treg and the higher risk of lung cancer in the elderly. Methods Seventy lung cancer patients and 60 sex-and age-matched controls were recruited. Both groups were divided into three subgroups based on their age (young, middle-aged, or elderly). The proportion of CD4(+)CD25(+)FOXP3(+)/CD4(+) T cells was detected using flow cytometry, and the level of FOXP3 mRNA in the peripheral blood was examined with realtime RT-PCR. Results The levels of CD4(+)CD25(+)FOXP3(+)/CD4(+) T cells and FOXP3 mRNA were significantly higher in lung cancer patients than in healthy controls (t = 7.16, P < 0.01 and t = 3.65, P < 0.01, respectively). Within the healthy groups, the elderly group had larger proportion of CD4(+)CD25(+)FOXP3(+) Treg (F = 32.54, P < 0.01) and higher FOXP3 mRNA expression (F = 4.76, P < 0.01) than their younger counterparts. Among the six subgroups, the elderly lung cancer patients exhibited the highest levels of both CD4(+)CD25(+)FOXP3(+) Treg (11.81 +/- 2.40%) and FOXP3 mRNA (3.14 +/- 1.30). Conclusions The accumulation of CD4(+)CD25(+)FOXP3(+) Treg with age correlates well with the increasing incidence of lung cancer in the elderly.