Squamous cell carcinoma is a common form of lung cancer, the leading cause of cancer deaths in the world. Identifying early stage lung squamous cell carcinoma patients who would benefit most from effective therapies will reduce the mortality. We have previously shown that microRNAs (miRNAs) were stably present in sputum and potentially useful in diagnosis of lung cancer. The objective of this study was to develop a panel of miRNAs that can be used as a sputum-based test for early stage squamous cell carcinoma of the lungs. This study contained three phases: (1) marker discovery by profiling miRNA expression signatures on 15 lung squamous cell carcinoma and matched normal lung tissue samples with GeneChip miRNA Array; (2) marker optimization by real-time quantitative RT-PCR on sputum of a case-control cohort of 48 stage I lung squamous cell carcinoma patients and 48 healthy individuals; and (3) marker validation on an independent set including 67 lung squamous cell carcinoma patients and 55 healthy subjects. On the surgical tissues, six miRNAs were identified, of which three were overexpressed and three were underexpressed in all 15 tumors. On the sputum samples of the case-control cohort, three (miR-205, miR-210 and miR-708) of the six miRNAs were selected, which in combination produced the best prediction in distinguishing lung squamous cell carcinoma patients from normal subjects with 73% sensitivity and 96% specificity. Validation of the marker panel in the independent populations confirmed the sensitivity and specificity that provided a significant improvement over any single one alone. The sputum markers showed the potential to improve the early detection of lung squamous cell carcinomas.
