FoxQ1 overexpression influences poor prognosis in non-small cell lung cancer, associates with the phenomenon of EMT

Abstract

Background: We determined the expression of forkhead box Q1 (FoxQ1), E-cadherin (E-cad), Mucin 1 (MUC1), vimentin (VIM) and S100 calcium binding protein A4 (S100A4), all epithelial-mesenchymal transition (EMT) indicator proteins in non-small cell lung cancer (NSCLC) tissue samples. We also investigated the relationship between these five proteins expression and other clinicopathologic factors in NSCLC. Finally, we assessed the potential value of these markers as prognostic indicators of survival in NSCLC's patients.

Methods: Quantitative real-time PCR and immunohistochemistry were used to characterize the expression of the FoxQ1 mRNA and protein in NSCLC. Expression of transcripts and translated products for the other four EMT indicator proteins was assessed by immunohistochemistry in the same clinical NSCLC samples.

Results: FoxQ1 mRNA and protein were up-regulated in NSCLC compared with normal tissues (P = 0.015 and P<0.001, respectively). Expression of FoxQ1 in adenocarcinoma was higher than in squamous cell carcinoma (P = 0.005), and high expression of FoxQ1 correlated with loss of E-cad expression (P = 0.012), and anomalous positivity of VIM (P = 0.024) and S100A4 (P = 0.004). Additional survival analysis showed that high expression of FoxQ1 (P = 0.047) and E-cad (P = 0.021) were independent prognostic factors.

Conclusion: FoxQ1 maybe plays a specific role in the EMT of NSCLC, and could be used as a prognostic factor for NSCLC.

Figure 1. Expression of FoxQ1 mRNA in NSCLC tissues and corresponding non-cancerous tissues.

One-step q RT-PCR was performed to confirm the expression of FoxQ1 mRNA in human tissues. Results were normalized to GAPDH mRNA level. The FoxQ1 mRNA level in NSCLC tissues were higher than that in peritumoural tissues with statistical significance using a paired-samples T test. ** P<0.05. Bars indicate standard error (S.E.).

Figure 2. Representative IHC images showing expression of FoxQ1 and EMT-related biomarkers in TMA sections of NSCLC.

(A) 1 and 2: lung squamous cell carcinoma tissue pattern with H&E staining; 3 and 4: high expression of FoxQ1; 5 and 6: loss of E-cad expression; 7 and 8: strong VIM-positive staining. (B) 1 and 2: lung adenocarcinoma tissue pattern with H&E staining; 3 and 4: positive staining for FoxQ1; 5 and 6: negative staining for MUC1; 7 and 8: up-regulated expression of S100A4. (C) 1 and 2: lung adenocarcinoma tissue with H&E staining; 3 and 4: negative IHC for FoxQ1; 5 and 6: strong immunological reaction of E-cad; 7 and 8: negative for S100A4. (D) 1 and 2: lung squamous cell carcinoma tissue with H&E staining; 3 and 4: low expression of FoxQ1; 5 and 6: high expression of MUC1; 7 and 8: weak expression of VIM. Original magnification was ×40 for 1, 3, 5 and 7; and ×400 for 2, 4, 6 and 8.

Figure 3. Kaplan-Meier survival curves after surgical therapy in NSCLC.

(A) Curves calculated for FoxQ1 expression. High expression in the FoxQ1 group (red line) indicated significantly less survival than low and no expression in the FoxQ1 group (blue line). (B) Curves calculated for E-cad expression. Lifespans of patients with positive E-cad staining are much shorter (red line) than in patients with negative E-cad staining (blue line).