Macroautophagy/autophagy is an intracellular process involved in the breakdown of macromolecules and organelles. Recent studies have shown that PKD2/PC2/TRPP2 (polycystin 2, transient receptor pote...

Purpose: Oral squamous cell carcinoma (OSCC) is commonly preceded by potentially malignant lesions, referred to as oral dysplasia. We recently reported that oral dysplasia is associated with aberrant activation of the Wnt/β-catenin pathway, due to overexpression of Wnt ligands in a Porcupine (PORCN)-dependent manner. Pharmacologic inhibition of PORCN precludes Wnt secretion and has been proposed as a potential therapeutic approach to treat established cancers. Nevertheless, there are no studies that explore the effects of PORCN inhibition at the different stages of oral carcinogenesis. Experimental Design: We performed a model of tobacco-induced oral cancer in vitro, where dysplastic oral keratinocytes (DOK) were transformed into oral carcinoma cells (DOK-TC), and assessed the effects of inhibiting PORCN with the C59 inhibitor. Similarly, an in vivo model of oral carcinogenesis and ex vivo samples derived from patients diagnosed with oral dysplasia and OSCC were treated with C59. Results: Both in vitro and ex vivo oral carcinogenesis approaches revealed decreased levels of nuclear β-catenin and Wnt3a, as observed by immunofluorescence and IHC analyses. Consistently, reduced protein and mRNA levels of survivin were observed after treatment with C59. Functionally, treatment with C59 in vitro resulted in diminished cell migration, viability, and invasion. Finally, by using an in vivo model of oral carcinogenesis, we found that treatment with C59 prevented the development of OSCC by reducing the size and number of oral tumor lesions. Conclusions: The inhibition of Wnt ligand secretion with C59 represents a feasible treatment to prevent the progression of early oral lesions toward OSCC.

Nearly 90% of oral cancers are characterized as oral squamous cell carcinoma (OSCC), representing the sixth most common type of cancer. OSCC usually evolves from oral potentially malignant disorders that, in some cases, are histologically consistent with a oral dysplasia. The levels of 1α,25 dihydroxyvitamin D3 (1,25-(OH)2D3; calcitriol), the active form of vitamin D3, have been shown to be decreased in patients with oral dysplasia and OSCC. Moreover, treatment with 1,25-(OH)2D3 has been proven beneficial in OSCC by inhibiting the Wnt/β-catenin pathway, a signaling route that promotes cell migration, proliferation, and viability. However, whether this inhibition mechanism occurs in oral dysplasia is unknown. To approach this question, we used dysplastic oral keratinocyte cultures and oral explants (ex vivo model of oral dysplasia) treated with 1,25-(OH)2D3 for 48 h. Following treatment with 1,25-(OH)2D3, both in vitro and ex vivo models of oral dysplasia showed decreased levels of nuclear β-catenin by immunofluorescence (IF) and immunohistochemistry (IHC). Consistently, reduced protein and mRNA levels of the Wnt/β-catenin target gene survivin were observed after treatment with 1,25-(OH)2D3. Moreover, 1,25-(OH)2D3 promoted membranous localization of E-cadherin and nuclear localization of vitamin D receptor (VDR). Functionally, DOK cells treated with 1,25-(OH)2D3 displayed diminished cell migration and viability in vitro.

Oral Squamous Cell Carcinoma (OSCC), the main form of oral cancer, is a major health problem globally that affects 400,000 people every year. It has been postulated that periodontitis, a chronic inflammatory disease characterized by alveolar bone resorption, is an independent risk factor for OSCC. However, the mechanisms underlying this link are not fully elucidated. It has been demonstrated that the Wnt/β-catenin pathway is key to the transformation of oral potentially malignant disorders (OPMD) towards OSCC (i.e., leukoplakia), particularly in OPMD histologically diagnosed as oral dysplasia. Using a GEO database of oral carcinogenesis (GSE85195), the transcriptional modification of 19 Wnt ligands and 4 key regulatory proteins of β-catenin, including E-cadherin, APC, AXIN and GSK3B, during leukoplakia, and early and late stages OSCC, was determined. The transcriptional expression of these targets was also assessed in periodontitis (GEO database GSE223924). Together, it was found that Wnt ligands Wnt3, Wnt3a, Wnt5b and Wnt7b are concomitantly upregulated in periodontitis and oral carcinogenesis. With these results, and the information retrieved from the literature, this review discusses the potential role of the Wnt/β-catenin pathway as a molecular mechanism that could interlink periodontitis and OSCC.

Oral squamous cell carcinoma (OSCC) is the most common type of oral cancer, which is usually preceded by a potentially malignant disorder histologically diagnosed as dysplasia. We and others have provided evidence for the pro-carcinogenic role of the Wnt/β-catenin pathway in this context, in which Wnt ligands stabilize and allow relocalization of β-catenin to the nucleus for transcription of pro-survival and pro-proliferation genes. However, the contribution of Porcupine (PORCN), an O-acyltransferase that catalyzes the palmitoylation of Wnt ligands, to OSCC carcinogenesis is not known. Moreover, the effectiveness of LGK974, a novel PORCN inhibitor remains to be elucidated. By using different ex vivo, in vivo and in vitro OSCC carcinogenesis models, we show that PORCN expression is significantly increased in high-grade dysplasia as well as moderately/poorly- differentiated OSCC. Consistent with these observations, expression of key proteins involved in the Wnt/β-catenin pathway are elevated as well. Importantly, the treatment with LGK974, a chemical PORCN inhibitor, reduced the number and size of oral lesions in mice treated with 4-Nitroquinoline 1-oxide (4NQO), a tobacco smoke surrogate. These results highlight the role of PORCN during OSCC carcinogenesis.