miR-16-5p specifically inhibits IFN-γ-regulated memory T helper cell differentiation in malignant pleural effusion of non-small cell lung cancer.

Background: The mechanism for memory T helper (Th) cell differentiation in malignant pleural effusion (MPE) of non-small cell lung cancer (NSCLC) is poorly understood. MicroRNAs (miRNAs), as small non-coding RNA that regulate gene expression, play a crucial role in the regulation of memory Th cell differentiation. However, whether miRNAs can inhibit the differentiation of memory Th cells in MPE of NSCLC has not been reported. This study aimed to explore miR-16-5p specifically inhibits interferon-gamma (IFN-γ)-regulated memory Th cell differentiation in MPE of NSCLC.

Methods: A total of 30 patients with NSCLC and 30 age- and sex-matched patients, who were clinically diagnosed as benign pleural effusion (BPE) of lung disease and had not received any intervention, were collected. The expression of nucleic acids, miRNAs, and cytokines was detected by polymerase chain reaction (PCR), miRNA microarray, enzyme-linked immunosorbent assay (ELISA), flow cytometry, and western blotting.

Results: The expression of CD4CD69 T cells in NSCLC with MPE was lower than that in lung disease BPE. CD4CD69 T cells highly express CD45RO and mainly secrete anti-tumor cytokines IFN-γ, interleukin-2 (IL-2), and tumor necrosis factor-α (TNF-α). The expression of miR-16-5p in CD4CD69 CD45RO T cells in MPE was higher than that in BPE. Moreover, miR-16-5p can bind to both IFN-γ promoter and its 5'untranslated region (5'-UTR), suggesting that - may be the target gene directly affected by miR-16-5p. IFN-γ also affects the differentiation of memory CD4 T cells by regulating T-bet.

Conclusions: We believe that miR-16-5p may regulate the decrease of differentiation of naïve CD4 T cells into memory CD4CD69 T cells through its target gene - in MPE, thus reducing the number of cytokines that produce anti-tumor effects. It may be the main reason for the low response rate of lung cancer with MPE immunotherapy.