Analysis of regulatory T cells in patients of NSCLC with malignant pleural effusion.

Abstract

e17511 Background: Enrichment of regulatory T (Treg) cells at the affected anatomic site in cancer may suppress the anti-tumor immune response influencing the cancer progression. Understanding of the clinical relevance of Treg mediated suppression of anti-tumor immune response and mechanisms underlying their preferential trafficking to the affected anatomic site is still limited. The aim of this study was to enumerate the frequencies of Treg cells in malignant pleural effusion and peripheral blood of patients with advanced NSCLC and it’s trend after treatment. Methods: Treg frequencies were evaluated in pleural effusion and peripheral blood of the patients with advanced NSCLC (n=27) using flowcytometry and compared with peripheral blood of age and sex matched healthy controls (n=15) and tubercular pleural effusions (n=10). The Treg cells were characterized as CD4+CD25+Foxp3+ T cells gated on CD4+CD25+ T cells. We assessed the effect of treatment response on Treg frequency. We have also looked for the expression of chemokine receptors CCR4 and CCR6 on the Tregs in pleural effusion and peripheral blood of the patients. Results: Compared to healthy controls, frequency of CD4+CD25+Foxp3+ Tregs was significantly increased in peripheral blood of patients with NSCLC (p=0.0036). In pleural effusion of patients, Treg frequency was higher than their corresponding peripheral blood (p=0.025). As compared to tubercular pleural effusion Treg frequency was higher in malignant effusion (p<0.0001). We had 12 patients who completed treatment and in whom response evaluation was available. Treg frequency reduced at the time of response (PR or SD) and increased again at disease progression. Surface expression of CCR4 and CCR6 was higher on Treg cells as compared to non Treg CD4 cells among the patients (p=0.0001; p=0.001 respectively). However, there was no difference in expression of these chemokine receptors on Tregs in pleural fluid and peripheral blood. Conclusions: Tregs are increased in patients of NSCLC, both at disease site and in systemic circulation. This increase may be chemokine receptors mediated. Treg frequency changes with treatment and response. Modulation of Tregs may have therapeutic implication in the management of advanced NSCLC.