Inhibition of MMP-9 using a pyrrole-imidazole polyamide reduces cell invasion in renal cell carcinoma

We investigated the clinical significance of the expression levels of matrix metalloproteinase 9 (MMP-9) in renal cell carcinoma (RCC). In addition, we validated the efficacy of pyrrole imidazole polyamide (PIP) targeting MMP-9 on inhibiting proliferation and invasion of RCC. We evaluated the expression levels of MMP-9 in 249 RCC specimens by immunostaining and analyzed the association between MMP-9 expression levels and cancer-specific survival. Furthermore, in a human RCC cell line, Caki-2, we tested the effect of a couple of PIPs targeting MMP-9 one recognizing an NF-κB binding site (MMP-9-NF-κB PIP) and another for the AP-1 binding site (MMP-9-AP-1 PIP) in the MMP-9 promoter. The expression levels of MMP-9, proliferative activity and invasive capability were tested by quantitative PCR, WST8 assay and Matrigel invasion assay, respectively. By immunostaining of the clinical specimens, strong MMP-9 staining was proven to be a significant predictor of poor prognosis for cancer-specific survival (P<0.01). In Caki-2 cells, MMP-9-NF-κB PIP significantly reduced the expression levels of MMP-9 mRNA and inhibited cell invasion, but did not affect the cell proliferation activity. On the other hand, no effect was found in MMP-9-AP-1 PIP on MMP-9 mRNA expression, cell proliferation and invasion. We confirmed the inhibitory effects of MMP-9-NF-κB PIP on the expression of MMP-9 and subsequent invasion of Caki-2 cells. Since it was clearly shown that high MMP-9 expression levels were associated with poor prognosis of RCC, MMP-9 is a potential candidate target for RCC treatment. Transcription therapy using a minor groove binder, such as NF-κB PIP, may be a potential therapeutic agent for RCC, although further investigation is required.