An immunohistochemical analysis of cell cycle markers in oral mucosal dysplastic lesions treated by laser therapy. A pilot study

Inhibition of PORCN Blocks Wnt Signaling to Attenuate Progression of Oral Carcinogenesis

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.

Assessment of laminin-5 in oral dysplasia and squamous cell carcinoma

PURPOSE

Laminin-5 is an important protein in the establishment of an intact basement membrane. The aims of this study were to assess the expression of laminin-5 (γ2 chain) using cyclin D1 and Ki-67 in hyperplastic oral mucosal lesions, oral dysplasia, and squamous cell carcinoma (SCC).

MATERIALS AND METHODS

Paraffin-embedded tissue blocks of 134 patients were stained for laminin-5, cyclin D1, and Ki-67 using immunohistochemistry and assessed by virtual microscopy. Statistical analysis was performed using Kruskal-Wallis tests and Mann-Whitney U tests for post hoc assessment.

RESULTS

Laminin-5, cyclin D1, and Ki-67 were found to have significant differences in expression for the different categories of dysplasia, SCC, and hyperplasia (P < .001). Cyclin D1 and Ki-67 expression levels were significantly increased in moderate and severe dysplasia and SCC, with no significant difference in expression between hyperplasia and mild dysplasia or between biopsies of severe dysplasia and SCC. Laminin-5 expression was only significantly increased in SCC, confirming it as a marker of malignant transformation and invasion.

CONCLUSIONS

The results of this study indicate that overexpression of laminin-5 is found only in SCC and not dysplastic lesions. Therefore, laminin-5 has potential as a marker for the intraoperative assessment of cancer excision margins and could be used as a target for chemotherapeutic agents.