Patients and tumor tissues

A total of 52 primary NSCLC patients (40 adenocarcinoma, 8 squamous-cell carcinoma, and 4 large-cell lung cancer) who received resection operation without preoperative radiotherapy and chemotherapy between June 2013 and March 2014 in Department of thoracic surgery, the Second Clinical Medical College of Jinan University (Shenzhen People’s Hospital) were selected. All the cases were confirmed by pathology. The patients ranged from 38 to 83 years old (average age was 62.8 years), including 40 males and 12 females. Up to 24, 12, and 16 cases of stage I, II, and III–IV NSCLC, respectively, without distant metastases were included. All subjects gave their informed consent for inclusion before they participated in the study. The study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by the Ethics Committee of Shenzhen People’s Hospital.

The parts of the cancerous tissues where tumors grow actively without necrosis and adjacent tissues of 0.5 cm to 2 cm distance from the tumor were surgically resected. Tissues were frozen in liquid nitrogen quickly within 10 min after leaving the body and transferred to a − 70 °C refrigerator within 30 min for long-term preservation.