Myeloid cell leukemia-1 is a molecular indicator for malignant transformation of oral lichen planus

Oral lichen planus (OLP), characterized by a chronic mucocutaneous inflammatory condition, is a common disease of the oral cavity. Retrospective and prospective epidemiological data suggest that OLP is considered to have malignant potential. However, it is unclear as to which types of molecules may cause malignant transformation of OLP. In the present study, the presence of myeloid cell leukemia-1 (Mcl-1) and B-cell lymphoma-2 (Bcl-2) was studied by western blot analysis in 11 OLP and three normal oral mucosa (NOM) samples and in two human oral cancer cell lines. The functional role of Mcl-1 in oral cancer cells was analyzed using a trypan blue exclusion assay and soft agar assay. Mcl-1 was strongly expressed in the OLP and the two oral cancer cell lines compared with NOM, whereas Bcl-2 was not. Sorafenib and mithramycin A decreased cell viability in MC-3 and HSC-3 oral cancer cells and at same concentration they reduced the expression level of Mcl-1 in the two cell lines. The two chemicals affected Mcl-1 protein and significantly inhibited neoplastic cell transformation in the two cell lines. We suggest that the malignant potential of OLP may be associated with the expression of Mcl-1, and that downregulation of Mcl-1 may prevent malignant transformation of OLP to oral cancer.