Abstract
The proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) promotes tumor progression through activation of matrix metalloproteinase (MMP) activity. MMP-9 is a gelatinase secreted by both cancer cells and surrounding stromal cells, and it contributes to TNF-alpha-stimulated tumor invasion and metastasis. Cyclin-dependent kinase 9 (CDK9), the catalytic component of positive transcription elongation factor-b, phosphorylates serine 2 residues in the C-terminal domain of RNA polymerase II for productive transcription elongation and is up-regulated upon exposure to various stresses. This study investigated roles of CDK9 in TNF-alpha-stimulated MMP-9 expression in human lung adenocarcinoma cells. CDK9 activity was inhibited using three different strategies, including the CDK9 pharmacological inhibitor 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), a dominant-negative CDK9, and a CDK9-specific small interfering RNA. All three approaches reduced TNF-alpha-mediated accumulation of MMP-9 in the conditioned media as demonstrated by gelatin zymography. In contrast, transforming growth factor-beta1-induced accumulation of MMP-2 was unaffected by DRB. Expression of the MMP-9 gene was examined using reverse transcription real time PCR and using a transient transfection assay to evaluate MMP-9 promoter activity. DRB reduced the TNF-alpha-induced increase in MMP-9 mRNA levels but did not effect transforming growth factor-beta1-induced MMP-2 mRNA expression. Consistently DRB and dominant-negative CDK9 completely abrogated TNF-alpha-stimulated human MMP-9 promoter activity. TNF-alpha did not regulate expression or localization of CDK9 or its regulatory partner Cyclin T. However, TNF-alpha stimulated CDK9 binding to Cyclin T and MMP-9 gene occupancy by both CDK9 and the serine 2-phosphorylated form of RNA polymerase II. Our findings indicate that CDK9 mediates TNF-alpha-induced MMP-9 transcription. Disruption of TNF-alpha signaling using CDK9 inhibitors could serve as a potential therapeutic strategy against tumor invasion and metastasis.
Highlights
Metastasis is one of the six hallmarks of cancer [1], and the persistent inflammatory environment surrounding cancer cells promotes invasion and metastasis [2, 3]
Our results indicated that Cyclin-dependent kinase 9 (CDK9) was essential for the induction of Matrix metalloproteinase-9 (MMP-9) by TNF-␣
Requirement of CDK9 for TNF-␣-stimulated Expression of matrix metalloproteinase (MMP)-9 Human Lung Adenocarcinoma Cells—To investigate a potential role of CDK9 in TNF-␣-stimulated expression, we examined MMP-9 activity in the conditioned media from TNF␣-stimulated cells in the presence or absence of DRB, a pharmacological inhibitor of CDK9
Summary
Metastasis is one of the six hallmarks of cancer [1], and the persistent inflammatory environment surrounding cancer cells promotes invasion and metastasis [2, 3]. Expression of dominant-negative CDK9 by transient transfection partially reduced TNF-␣-induced MMP-9 activity in the conditioned media by 50% (Fig. 2A).
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
