Overexpression of phospholipase D enhances matrix metalloproteinase-2 expression and glioma cell invasion via protein kinase C and protein kinase A/NF-κB/Sp1-mediated signaling pathways

Abstract

Glioblastoma is a severe type of primary brain tumor, and its highly invasive character is considered to be a major therapeutic obstacle. Phospholipase D (PLD) isozyme is overexpressed in various human tumor tissues and involved in tumorigenesis. However, the molecular mechanisms by which PLD enhances glioma invasion are unknown. In this study, we demonstrate that the increased expression of PLD and its enzymatic activity in the glioma stimulate the secretion and expression of matrix metalloproteinase (MMP)-2 and induce the invasiveness of glioma cells. The upregulation of MMP-2 induced by phosphatidic acid (PA), the product of PLD, was mediated by protein kinase C (PKC), protein kinase A (PKA), nuclear factor-kappaB (NF-kappaB) and Sp1 and it enhanced glioma cell invasion. PA activated PKC and PKA and induced the nuclear translocation and transactivation of NF-kappaB. PA also increased the binding of NF-kappaB and Sp1 to the MMP-2 promoter. Mutation of the NF-kappaB- or Sp1-binding sites significantly attenuated MMP-2 promoter activity. This is the first report to show that NF-kappaB and Sp1 are essential transcriptional factors linking PLD to MMP-2 upregulation, providing evidence that PLD contributes to glioma progression by enhancing MMP-2 expression and tumor cell invasion via PKC/PKA/NF-kappaB/Sp1-mediated signaling pathways.

Phospholipase D1 Drives a Positive Feedback Loop to Reinforce the Wnt/β-Catenin/TCF Signaling Axis

“…Growing evidence in support of PLD involvement in cancer development further strengthens the tumorigenic contributions of β-catenin and, thereby, establishes the critical role of the Wnt/β-catenin/PLD pathway, with important implications in carcinogenesis. We have reported on the enhancement of expression of the MMP-2 gene by increased DNA binding activity of NFκB and Sp1, which promotes glioma cell invasion (12). Thus, it is possible that promotion of the tumor phenotype by PLD1 is independent of TCF-induced genes.…”

“…Stable cells overexpressing PLD1 and PLD2 in nude mice have shown anchorage-independent growth, upregulation of matrix metalloproteinase (MMP), and tumorigenesis (11)(12)(13). We recently reported on the significant cooverexpression of PLD isozymes with β-catenin in human colorectal cancers and induced the expression of PLD1 by tumor promoter phorbol 12-myristate 13-acetate (PMA) for the enhancement of the activity of MMP (5).…”

Phospholipase D Signaling Pathways and Phosphatidic Acid as Therapeutic Targets in Cancer

“…Early indications of the importance of PLD and PtdOH in cancer came from observations that cells transformed by viral oncogenes, such as v-Src (Song et al, 1991), v-Fps (Jiang et al, 1994 v-Ras (Carnero et al, 1994;Jiang et al, 1995a), and v-Raf (Frankel et al, 1999), all showed elevated PLD activity relative to nontransformed control cells. Furthermore, PLD mRNA and protein analyses from tumors of breast (Uchida et al, 1997;Noh et al, 2000), renal (Zhao et al, 2000), colorectal , gastric (Uchida et al, 1999), thyroid , and brain (Park et al, 2009) origin show elevated PLD1 and/or PLD2 expression relative to normal surrounding tissue. As such, overexpression of PLD isoforms is associated with enhanced tumorigenesis in cultured cells as measured by increased anchorageindependent growth (Min et al, 2001b;Ahn et al, 2003), the most important measure of tumorigenicity (Shin et al, 1975).…”

“…Later studies revealed a positive correlation between PLD activity and invasive potential. Overexpression of PLD in breast, glioblastoma, or lymphoma cells stimulates invasion Knoepp et al, 2008;Park et al, 2009), whereas expression of dominant-negative PLD prevents invasion . Similarly, small-molecule PLD inhibitors and PLD siRNA decrease breast cancer cell invasion and further implicate the importance of PLD in invasive processes .…”

PLD2 (phospholipase D2)

“…Furthermore, a PLD2 polymorphism detected in colorectal cancer was found to be closely linked to the prevalence of the disease (Wood et al, 2007). In the terms of metastasis, PLD has been implicated in the secretions of matrix metalloproteinase (MMP)-2 and MMP-9 in glioma and colorectal cancers, respectively (Kang et al, 2008;Park et al, 2009). Also, the overexpression of active PLD2 has been reported to increase the serum-induced cell invasion of EL4 lymphoma cells and to promote the metastasis of EL4 lymphoma cells into liver in syngeneic mice (Knoepp et al, 2008).…”