Differential expression of miR200a-3p and miR21 in grade II–III and grade IV gliomas

Apr 24, 2014Cancer biology & therapy

Differences in miR200a-3p and miR21 levels in mid- and high-grade brain tumors: miR200a-3p is controlled by DNA repair enzyme and may increase response to chemotherapy

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Abstract

miR21 is upregulated in grade IV glioblastomas compared to lower-grade gliomas, while miR200a is downregulated in GBMs.

The expression level of miR21 correlates with tumor grade and may serve as a marker for tumor progression.
This study reveals for the first time that miR200a is downregulated in glioblastomas compared to lower-grade gliomas.
Overexpression of miR200a in GBM cells is associated with increased sensitivity to temozolomide (TMZ).
Higher levels of miR200a are found in TMZ-responsive compared to TMZ-unresponsive glial cells in primary culture.
miR200a expression is negatively correlated with the DNA repair enzyme MGMT, suggesting a potential link to therapeutic response.

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Glioblastoma multiforme (GBM) is the most common primary brain tumor and is among the deadliest of human cancers. Dysregulation of microRNAs (miRNAs) expression is an important step in tumor progression as miRNAs can act as tumor suppressors or oncogenes and may affect cell sensitivity to chemotherapy. Whereas the oncogenic miR21 has been shown to be overexpressed in gliomas, the expression and function of the tumor-supressor miR200a in GBMs remains unknown. In this study, we show that miR21 is upregulated in grade IV (GBMs) vs. grade II-III (LGs) gliomas, confirming that miR21 expression level is correlated with tumor grade, and that it may be considered as a marker of tumor progression. Conversely, miR200a is demonstrated for the first time to be downregulated in GBMs compared with LGs, and overexpression of miR200a in GBM cells is shown to promote TMZ-sensitivity. Interestingly, miR200a but not miR21 expression level is significantly higher in TMZ-responsive vs. -unresponsive tumoral glial cells in primary culture. Furthermore, miR200a appears negatively correlated with the expression of the DNA repair enzyme O (6)-methylguanine methyltransferase (MGMT), and the inhibition of MGMT activity results in an increase of miR200a expression in GBM cells. Taken together, these data strongly suggest that miR200a is likely to act as a crucial antitumoral factor regarding glioma progression. Interplay between miR200a and MGMT should be considered as potential mechanism involved in therapeutic response.

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Differential expression of miR200a-3p and miR21 in grade II–III and grade IV gliomas

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