Expression and unique functions of four nuclear factor of activated T cells isoforms in non-small cell lung cancer

Nuclear factor of activated T cells (NFAT) is an important family of transcription factors that can be activated by calmodulin and calcineurin in human cells. To investigate the expression and clinical significance of NFAT isoforms and calcineurin in non-small cell lung cancer (NSCLC), we collected tumor and adjacent normal tissues from 159 NSCLC patients and assembled them in a tissue microarray. Protein levels of NFAT1, NFAT2, NFAT3, NFAT4, and calcineurin were determined using immunohistochemistry. Correlations between NFAT and calcineurin expression and clinicopathologic characteristics were analyzed. We found that the positive rates of NFAT1 (52.8%, 84/159), NFAT2 (11.3%, 18/159), NFAT3 (28.3%, 45/159), NFAT4 (47.2%, 75/159), and calcineurin (47.8%, 76/159) expression were significantly higher in tumor tissues than in adjacent normal lung tissues (P<0.001), respectively. The positive rate of NFAT1 expression was significantly higher in patients with adenocarcinoma (63.5%, 47/74) than in those with squamous cell carcinoma (43.5%, 37/85) (χ2=6.340, P=0.012); with lymph node metastasis (61.6%, 53/86) than without lymph node metastasis (42.5%, 31/73) (χ2=5.818, P=0.016); and with stage-II and -III diseases (61.8%, 55/89) than with stage-I disease (41.4%, 29/70) (χ2=6.524, P=0.011). Moreover, the overexpression of NFAT1 was associated with poor survival of NSCLC patients (χ2=5.006, P=0.025). The positive rate of NFAT4 was significantly higher in patients with squamous carcinoma (57.6%, 49/85) than in those with adenocarcinoma (35.1%, 26/74) (χ2=8.045, P=0.005) and with high and moderate differentiation (54.9%, 61/111) than with low differentiation (29.2%, 14/48) (χ2=8.943, P=0.003). Calcineurin overexpression was significantly associated with histologic type (higher in squamous carcinoma than in adenocarcinoma, χ2=8.897, P=0.003), differentiation grade (higher in high-moderation grade than in low grade, χ2=9.566, P=0.002) and gender (higher in male than in female, χ2=5.766, P=0.016). Furthermore, calcineurin expression was significantly correlated with NFAT4 level (r=0.429, P<0.001). These results suggest that NFAT1 expression is associated with lung adenocarcinoma progression, and NFAT4 expression, which was higher in squamous lung cancer, is associated with calcineurin expression and differentiation grade.