Hippo pathway and tumoral FOXP3 expression correlate with tumor growth in squamous cell carcinoma of the lung

Background: Expression of FOXP3 in tumors is associated with proliferation, migration, and invasion, has been implicated in cancer prognosis, and may be related to metastatic potential. The Hippo signaling pathway is known to regulate tissue homeostasis and organ size through cell proliferation and apoptosis. We investigated tumoral FOXP3, Lats2, and YAP expression related to the Hippo pathway in squamous cell carcinoma (SCC) of the lung. Methods: Between 1983 and 2006, 149 cases of SCC were diagnosed and surgically resected at Kyung Hee University Hospital. Immunohistochemical staining for FOXP3, YAP, and Lats2 was done. Results: Tumor size was inversely correlated with tumoral FOXP3 expression (p=0.015), Treg count (p < 0.0001), and positive Lats2 expression (p=0.028). YAP expression was inversely correlated with lymph node metastasis (p=0.039). Positive tumoral FOXP3 expression was significantly associated with infiltrated Treg count (p=0.001) and positive Lats2 expression (p=0.007). Conclusion: Tumoral FOXP3 has the potential to suppress tumor function in SCC of the lung. The decrease or loss of FOXP3 expression in cancer cells is thought to contribute to SCC tumorigenesis and progression in the lung. The tumor suppressor function of FOXP3 in SCC of the lung was related to Lats2 and YAP expression in the Hippo pathway.