Glioma is the most common malignant
cancer affecting the central nerve system, with dismal prognosis. Differentiation-inducing
therapy is a novel strategy that has been preliminarily proved effective against
malignant glioma. We have reported previously that activation of
cAMP/protein kinase A (PKA) pathway is capable of inducing
glioma cell differentiation, characterized by astrocyte-like shape and dramatic induction of astrocyte
biomarker glial fibrillary acidic protein (GFAP). However, little progress has been made on molecular mechanisms related. Here we demonstrate that
microRNA 335 (miR-335) is responsible for the
glioma cell differentiation stimulated by activation of cAMP/PKA pathway. In the cAMP elevator
cholera toxin-induced differentiation model of rat C6
glioma cells, miR-335 was significantly up-regulated, which was mimicked by other typical cAMP/PKA pathway activators (e.g.,
forskolin, dibutyryl-cAMP) and abolished by PKA-specific inhibitor (9R,10S,12S)-2,3,9,10,11,12-hexahydro-10-hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-i] [1,6]benzodiazocine-10-
carboxylic acid, hexyl
ester (
KT5720). In an assay measuring gain and loss of miR-335 function, exogenetic miR-335 resulted in induction of GFAP, whereas miR-335 specific inhibitor antagomir-335 violently blocked
cholera toxin-induced GFAP up-regulation. It is noteworthy that in human U87-MG
glioma cells and human primary culture
glioma cells, miR-335 also mediated
cholera toxin-induced differentiation. Taken together, our findings suggest that miR-335 is potently required for differentiation of
malignant glioma cells induced by cAMP/PKA pathway activation, and a single
microRNA may act as an important fate determinant to control the differentiation status of
malignant gliomas, which has provided a new insight into differentiation-inducing
therapy against
malignant gliomas.