miR-221 and miR-222 expression increased the growth and tumorigenesis of oral carcinoma cells

BACKGROUNDS: MicroRNAs are small noncoding RNAs involved in posttranscriptional gene regulation, which play an important role in both physiological functioning and pathological progression. The miR-221/miR222 microRNA family has been shown to be related to the neoplastic process in a number of different types of cancers; nevertheless, its function in oral squamous cell carcinoma (OSCC) remained uncertain. MATERIALS AND METHODS: Paired OSCC and matched noncancerous oral mucosa were examined for miR-221/miR-222 expression using quantitative reverse-transcription PCR. Ectopic expression of miR-221/miR222 by lentiviral infection was investigated to explore its in vitro and in vivo impact on the oncogenic phenotype and the expression of various target genes. The expression of Cip/Kip cell cycle regulator p27 in tumors was analyzed with immunohistochemistry. RESULTS: The expression levels of miR-221 and miR-222 were highly correlated in OSCC. Increased miR-221/miR222 expression was found in 40% of OSCC tissues. The ectopic expression of miR-221 or of miR-222 increased growth and anchorage-independent colony formation of OSCC cell lines. It also resulted in an increase in the tumorigenesis of an OSCC cell line in nude mice. Western blot analysis suggested that p27 and p57 might be the targets of miR-221/miR-222. p27 expression was reversely associated with the miR-221 and miR-222 expression level in OSCC tissues. CONCLUSIONS: Our findings suggested that increased miR-221/miR-222 expression was associated with the OSCC cell growth. J Oral Pathol Med (2011) 40: 560-566