Quantification of macrophage migration inhibitory factor mRNA expression in non-small cell lung cancer tissues and its clinical significance

Purpose: Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine derived from T cells and the pituitary gland. However, several types of solid cancers also secrete MIF, and this factor has been suggested to play an important role in carcinogenesis and the progression of malignancy. In this study, we quantified MIF mRNA expression of non-small cell lung cancer tissues and examined its relationship with clinicopathological factors. Experimental Design: MIF mRNAs of both tumor and normal tissues were quantified by a real-time monitoring reverse-transcription PCR in 59 patients with non-small cell lung cancer. The relationship between the grade of MIF expression and clinicopathological factors such as smoking history, cell type, stage, and prognosis was examined to investigate the clinical significance of intratumoral expression of MIF. Results: The mean copy number of MIF mRNA per 0.08 μg of total mRNA in tumor tissues was 144,078.00, whereas that of normal lung tissue was 25,438.46 (P < 0.0001). The amounts of MIF proteins revealed by a Western blot analysis correlated well with those of the corresponding mRNAs. Male patients and heavy smokers showed significantly higher expression of MIF. Patients with squamous cell carcinomas showed a higher expression of MIF mRNA than other subjects. In squamous cell carcinoma patients, higher expression of MIF mRNA was significantly associated with unfavorable prognosis (P = 0.0142). Conclusions: The general intratumoral expression and close relation with smoking suggested that MIF might contribute to tumorigenesis in the lung.