Expression of miRNA-601 and PD-L1 among Iranian Patients with Lung Cancer and Their Relationship with Smoking and Mycoplasma Infection

OBJECTIVE: microRNAs (miRNAs) are highly conserved noncoding RNA molecules that mainly function to regulate gene expressions, and have a significant role in tumourigenesis. Programmed cell death-ligand 1 (PD-L1) is a major co-inhibitory checkpoint signal that controls T cell activities, maintains peripheral tolerance and is contribute to the development of cancer. The aim of this study is to examine miRNA-601 and PD-L1 gene expression in patients with non-small-cell lung cancer (NSCLC) and its relation with Mycoplasma infection. MATERIALS AND METHODS: In this case-control study, respiratory secretions and blood samples were collected from 80 healthy people and 80 NSCLC patients. The expression levels of miRNA-601 and PD-L1 were evaluated using real-time polymerase chain reaction (qRT-PCR). The presence of Mycoplasma species in respiratory secretions was detected by biochemical assays and PCR. RESULTS: There was no significant difference in the expression level of miRNA-601 between control and patients with tumour stage I, but miRNA-601 expression was significantly downregulated in patients with tumour stages II, III, and IV (P<0.05). A significant, negative relationship was found between miRNA-601 expression and tumour stage (P<0.001). Overexpression of PD-L1 was found in all of the disease stages. PCR results showed the presence of Mycoplasma pneumoniae (M. pneumoniae) in respiratory secretions from patients with stages III and IV NSCLC. We observed that 72% of patients with stages III and IV NSCLC had a positive smoking history and 65.3% were positive for Mycoplasma. CONCLUSION: Serum miRNA-601 may act as a potential noninvasive biomarker for lung cancer and Mycoplasma infection prognosis.