MicroRNA-144 promotes cell proliferation, migration and invasion in nasopharyngeal carcinoma through repression of PTEN

Nasopharyngeal carcinoma (NPC) is a type of head and neck cancer with significantly high prevalence in Southern China. Unlike other head and neck cancers, mutations or deletions of tumor suppressor genes in NPC are not common. Recently, down-regulation of tumor suppressor genes expression by microRNA (miRNA) is increasingly recognized as an important mechanism of nasopharyngeal tumorigenesis. In this study, we reported that microRNA-144 (miR-144) was frequently upregulated in NPC specimens and cell lines. Repression of miR-144 significantly decreased cell proliferation, clonogenicity, migration, invasion and tumor formation in nude mice, while restoring miR-144 in miR-144-attenuated NPC cells exhibited a strong tumorigenic role. Further, we found that miR-144 was inversely correlated with the tumor suppressor gene phosphatase and tensin homolog (PTEN) in NPC specimens and cell lines, and then we identified PTEN as a direct target of miR-144 in NPC cell lines. PTEN downregulation in miR-144-attenuated cells could increase cell growth, migration and invasion. Mechanistic investigations revealed that miR-144 suppressed the expression of PTEN to increase the expression of pAkt and cyclin D1 to promote G(1)-phase transition and decrease E-cadherin to promote migration and invasion. Taken together, we provide compelling evidence that miR-144 functions as an onco-miRNA in NPC, and its oncoeffects are mediated chiefly by repressing PTEN expression to activate the PI3K/Akt pathway.