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

Abstract

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 real-time 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.

Fig 1. Proportion of CD4⁺CD25⁺FOXP3⁺/CD4⁺ cells in peripheral blood in the six study groups.

YC:Young lung cancer; MC: Middle-aged lung cancer; EC: Elderly lungcancer; YH:Young healthy; MH: Middle-aged healthy; EH: Elderly healthy; Proportion of CD4⁺CD25⁺FOXP3⁺/CD4⁺ cells increases with both age (^aP<0.01, ^bP<0.01, one-way analysis of variance) and lung cancer (^cP<0.01, student’s t test). The elderly lung cancer group displayed the highest proportion.

Fig 2. Comparison of FOXP3 mRNA expression levels in the six groups.

The expression level of FOXP3 mRNA was higher in patients than in healthy group by student’s t test (P < 0.01). It also increased with age according to one-way analysis of variance: ^aP < 0.01 compared with the young healthy group, ^bP < 0.01 compared with the middle-aged healthy group, ^cP < 0.01 compared with the young lung cancer group, ^dP < 0.01 compared with the middle-aged lung cancer group. FOXP3 mRNA increases with both age and lung cancer. The elderly lung cancer group displayed the highest expression level of FOXP3 mRNA (3.14 ± 1.30).