Detecting tumor-infiltrating Forkhead box P3-positive T cells in the prognosis of lung adenocarcinoma: Possible role of clustering tumor interleukin-12 subunit alpha and transforming growth factor beta 1 expression.

Background. While regulatory T cells (Tregs) are a poor prognostic factor for lung cancer, they may be detected as Forkhead box P3+ (FOXP3+) and cluster of differentiation (-CD) 4+ T cells by classifying FOXP3+CD4+ T cells into different subpopulations of CD4 cells. Objectives. To classify clusters of tumor-infiltrating Tregs in lung adenocarcinoma based on the mRNA expression levels of interleukin-12 subunit alpha (IL12A) and transforming growth factor beta 1 (TGFB1) in tumor specimens. Material and methods. Seventy-nine patients with lung adenocarcinoma were evaluated in this study. Clinical data were obtained from the patients' medical records, while tumor tissue samples were preserved as formalin-fixed paraffin-embedded (FFPE) tissue specimens. Immunohistochemical staining for CD4, CD8 and FOXP3 was performed and stained cell counts were obtained under 5 high-power fields. cDNA was synthesized from total RNA extracted from FFPE tissue specimens and amplified with Taqman probes for FOXP3, IL12A, TGFB1, and the glyceraldehyde-3-phosphate dehydrogenase gene. Results. Two clusters were identified:IL12AlowTGF1low (Cluster 1: n =44) and IL12AhighTGB1high (Cluster 2: n = 39). Although no significant difference in the FOXP3+ cell/CD4+ cell ratio was observed between the 2 clusters (p =0.921), the high FOXP3+/CD4+ cell ratio group showed a significantly poorer relapse-free survival rate than the low FOXP3+/CD4+ cell ratio group in Cluster 1 (p = 0.031). Conclusions. Although the results revealed no direct association between Tregs and prognosis according to each subtype, these results suggest that if a lung cancer specimen contains low levels of IL12A and T6F67, the FOXP3+/CD4+ cell ratio is useful for predicting the prognosis of lung cancer.