Correlation analysis of surfactant protein A and surfactant protein D with lung function in exhaled breath condensate from lung cancer patients with and without COPD.

Pulmonary surfactant protein A (SP‑A) and pulmonary surfactant protein D (SP‑D) are associated with the pathogenesis of chronic obstructive pulmonary disease (COPD). The aim of the present study was to determine the correlation between SP‑A, SP‑D and lung function in patients with COPD. A total of 60 patients with lung cancer undergoing unilateral lobectomy were selected and divided into three groups, including a non‑COPD group (n=20), a COPD treatment group (n=20) and a COPD control group (n=20). The levels of SP‑A and SP‑D were detected in the exhaled breath condensate (EBC) using ELISA analysis. Tissue samples were obtained during lobectomy via resection of the adjacent lung tissues, located >5 cm from the nodule. Immunohistochemistry and reverse transcription‑quantitative polymerase chain reaction analysis was performed. The proportion of SP‑A+ alveolar type II (ATII) cells and the mRNA levels of SP‑A and SP‑D in lung tissue were measured. In addition, the correlation between SP‑A and SP‑D in EBC, SP‑A and SP‑D mRNA in lung tissue, forced expiratory volume in 1 sec (FEV1) and the ratio of SP‑A+ ATII, was evaluated. The expression levels of SP‑A and SP‑D were significantly increased in patients of the non‑COPD group compared with the other two groups (P<0.05). In addition, the expression levels of SP‑A were positively correlated with FEV1 and the ratio of SP‑A+ ATII (P<0.05). The expression levels of SP‑D exhibited no correlation with FEV1 and ratio of SP‑A+ ATII (P>0.05). The results of the present study indicated that the SP‑A and SP‑D levels in EBC were correlated with lung function, which contributed to COPD diagnosis. Future studies are required to further investigate the results of the present study.