KLF4 ablation disrupts oral epithelial differentiation and increases squamous cell carcinomas upon chemical carcinogenesis

PAPARELLA M L; ABRIGO M.; COZZARIN M. E.; BAL DE KIER JOFFÉ, E; RAIMONDI ANA R.

Bariloche

Simposio; The Third South American Symposium in Signal Transduction and Molecular Medicine; 2015

Squamous cell carcinoma (SSC) of the head and neck is the sixth most common cancer and is rarely diagnosed in early stages. The early events in oral SCC carcinogenesis have been less studied and still poorly understood. In this regard, the transcription factor Krûppel-like factor 4 (Klf4) suppresses cell proliferation and promotes differentiation in stratified epithelia and helps to maintain homeostasis in epithelial cells. We have previously developed inducible mice carrying an oral-specific ablation of Klf4 (K14-CreERtam/Klf4flox/flox) which showed mild dysplastic lesions and abnormal differentiation in the tongue. With the aim to analyze if Klf4 cooperate in oral carcinogenesis we applied 4-nitroquinoline 1-oxide (4NQO), a chemical carcinogen, to this conditional Klf4 knockout mice line. 4NQO treated K14-CreERtam/Klf4flox/flox mice (KO 4NQO) showed a significant weight loss and developed more severe dysplastic lesions than control mice with 4NQO (p<0.005). The KO 4NQO showed a tendency to higher incidence of oral SCC and a marked keratinization pattern in dysplasias, in situ carcinomas and SCC. Previously we have shown that the conditional Klf4 knockout mice presented an increased cell proliferation and abnormal differentiation as judged by cytokeratins 1 and 14 expressions. Here we found that KO 4NQO tongues exhibited fewer cytokeratin 1 labeled cells when compared with 4NQO treated controls. Also, tongues from KO 4NQO mice exhibited increased expression of cyclin D1 when compared with Klf4 knockout mice. Klf4 ablation results in more severe dysplastic lesions in oral mucosa, with a tendency to higher incidence of SCC, after chemical carcinogenesis. We show here, in a context similar to the human carcinogenesis, that absence of Klf4 accelerates carcinogenesis and correlates with the absence of cytokeratin 1 expression. Also, we provide evidence that Klf4 has an important role in the differentiation process of the squamous epithelium of the tongue. Taken together, our previous and current data suggest that molecules acting upstream and downstream of Klf4 may represent components of a novel tumor-suppressive pathway in oral cancer.