Tumor-suppressive function of long noncoding RNA MALAT1 in glioma cells by suppressing miR-155 expression and activating FBXW7 function.

The human metastasis associated lung adenocarcinoma transcript 1 (MALAT1) is a long non-coding RNA associated with metastasis, and is a favorable prognostic factor for lung cancer. Recent studies have shown that MALAT1 plays an important role in many malignancies. However, little is known about the role of MALAT1 in glioma. In this study, we determined the expression of MALAT1 and explored its prognostic value in glioma. Further, we investigated the regulatory mechanism of MALAT1 in glioma progression. Our results showed that the expression of MALAT1 was significantly decreased in glioma specimens than in noncancerous brain tissues. In addition, MALAT1 expression was significantly correlated with tumor size, WHO grade and Karnofsky Performance Status (KPS), and was an independent prognostic factor for survival of glioma patients. The gain- and loss-of-function experiments revealed miR-155 down-regulation by MALAT1, resulting in reciprocal effects. Further, MALAT1 suppresses cell viability by down-regulating miR-155. FBXW7 mRNA was identified as a direct target of miR-155 in glioma. The miR-155-induced tumorigenesis is mediated through FBXW7 function. Finally, we found that MALAT1 positively regulated FBXW7 expression, which was responsible for glioma progression mediated by MALAT1-miR-155 pathway. In conclusion, our data demonstrated that MALAT1 may be a novel prognostic biomarker and therapeutic target in glioma. Restoration of MALAT1 levels represents a novel therapeutic strategy against glioma.