MicroRNAs Enriched in Epithelium of Oral Squamous Cell Carcinoma in Never Smokers

Objective: Recently there has been an increase in incidence of oral tumors not associated with the habitual oral usage of mutagenic agents tobacco or betel nut. In an effort to better understand these tumors we studied miRNA in tumor epithelium of never tobacco/betel users.  MicroRNAs (miRNAs) play a role in the regulation of gene expression and cell processes that control cell proliferation, differentiation, apoptosis, and migration. 

Materials and Methods: A comparison of levels among 372 miRNAs in 12 non-tobacco, non-betel users with oral squamous cell carcinoma and 10 healthy controls was made using RT-PCR.

Results: It revealed miR10b, miR-196a, miR-31, miR-187 and miR-503 were enriched in the tumor epithelium in oral squamous cell carcinoma (OSCC) of never tobacco users. A second study examining miRNA expression in tobacco or betel users revealed that the changes seen in miR187 and miR-503 were specific to OSCC epithelium in never users. Only one miRNA, miR-196a, was enriched in OSCCs in both smokers and never users but not in benign pathologies. It has already been shown to promote cell proliferation in squamous cell carcinoma cells. 

Conclusion: These results suggest that epithelial expression of miR-196a may be a key part of OSCC formation and/or progression. This miRNA, along with miR187 and miR503, serve as attractive targets in oral cancer diagnosis in never smokers. Exploration of the roles of miR187 and miR503 in OSCC in never smokers may shed light on the cellular changes specific to this OSCC subtype.