Glioblastoma multiforme (GBM) is the most common malignant
brain tumor, which, despite combined modality treatment, reoccurs and is invariably fatal for affected patients. Recently, a member of the
serine/threonine protein kinase D (PRKD) family, PRKD2, was shown to be a potent mediator of
glioblastoma growth. Here we studied the role of PRKD2 in U87MG
glioblastoma cell migration and invasion in response to
sphingosine-1-phosphate (S1P), an activator of PRKD2 and a GBM
mitogen. Time-lapse microscopy demonstrated that random cell migration was significantly diminished in response to PRKD2 silencing. The pharmacological PRKD family inhibitor
CRT0066101 decreased chemotactic migration and invasion across uncoated or
matrigel-coated Transwell inserts. Silencing of PRKD2 attenuated migration and invasion of U87MG cells even more effectively. In terms of downstream signaling,
CRT0066101 prevented PRKD2 autophosphorylation and inhibited p44/42 MAPK and to a smaller extent p54/46 JNK and
p38 MAPK activation. PRKD2 silencing impaired activation of p44/42 MAPK and p54/46 JNK, downregulated nuclear c-Jun
protein levels and decreased c-Jun(S73) phosphorylation without affecting the NFκB pathway. Finally, qPCR array analyses revealed that silencing of PRKD2 downregulates
mRNA levels of
integrin alpha-2 and -4 (ITGA2 and -4),
plasminogen activator urokinase (PLAU),
plasminogen activator urokinase receptor (PLAUR), and matrix
metallopeptidase 1 (MMP1). Findings of the present study identify PRKD2 as a potential target to interfere with
glioblastoma cell migration and invasion, two major determinants contributing to recurrence of
glioblastoma after multimodality treatment.