Angiogenesis and tumor growth inhibition by a matrix metalloproteinase inhibitor targeting radiation-induced invasion

Abstract

In this study, we have evaluated the interactions between ionizing radiation and a matrix metalloproteinase (MMP) inhibitor. Using Matrigel invasion assays, we show that ionizing radiation induced a dose-dependent increase in the invasive phenotype of cultured B16 melanoma cells and that conditioned medium from these irradiated B16 cells promoted endothelial cell [human microvascular endothelial cells (HMEC)] invasiveness. To determine whether the radiation-induced changes in invasive phenotype could be due to changes in MMP activation, we have tested the ability of the MMP inhibitor Metastat to modulate the ionizing radiation -induced invasive phenotype using both an in vitro melanoma model and a mouse s.c. tumor model. In these studies, Metastat inhibited the ionizing radiation -induced invasive phenotype in cultured B16 cells and similarly inhibited the increase in HMEC invasion induced by conditioned medium from irradiated B16 cells. Conversely, ionizing radiation increased B16 MMP-2 activity and the conditioned medium from irradiated B16 induced HMEC MMP-2 activity. To further investigate the interaction between ionizing radiation and MMP activation, we then studied the effects of ionizing radiation on downstream effectors of the MMP system. We found that ionizing radiation induced vascular endothelial growth factor (VEGF) secretion by B16 melanoma cells and that this secretion was inhibited by Metastat. Similarly, conditioned medium from irradiated B16 was also able to increase VEGF secretion in HMECs. Moreover, ionizing radiation -induced melanoma cell invasiveness was partially inhibited by an anti-VEGF monoclonal antibody. In vivo, ionizing radiation plus concomitant Metastat yielded the greatest growth inhibition of melanoma s.c. tumors and this effect correlated with inhibition of angiogenesis as measured by both Doppler ultrasonography and platelet/endothelial cell adhesion molecule-1 staining. Finally, ionizing radiation modulated MMP-2, VEGF, and VEGF receptor expression in these tumor samples using immunohistochemistry. Taken together, these results suggest that there is an ionizing radiationinduced tumor survival pathway and a possible paracrine ionizing radiation -induced stimulatory pathway emanating from tumor cells toward the endothelial bed that is impeded when Metastat is given simultaneously. This model could provide in vivo evidence of the antitumor efficacy of combining a MMP inhibitor with ionizing radiation to target radiation-induced invasion and angiogenesis.

Adenovirus-mediated transfer of siRNA against MMP-2 mRNA results in impaired invasion and tumor-induced angiogenesis, induces apoptosis in vitro and inhibits tumor growth in vivo in glioblastoma

“…In addition, irradiated melanoma cells displayed enhanced invasive capacity with increased MMP-2 expression, and subsequently induced VEGF protein secretion. Specific MMP-2 inhibition blocked VEGF upregulation, and inhibited tumor growth and angiogenesis in vivo (Kaliski et al, 2005). Similarly, the results of the present study demonstrate that siRNA-induced MMP-2 inhibition decreased VEGF protein levels in glioblastoma cell lines.…”

In vitro irradiation of basement membrane enhances the invasiveness of breast cancer cells

“…Sublethal in vitro irradiation of rat 9L glioma cells resulted in the formation of a greater number of tumour satellites after injection of these irradiated cells into the striatum of rat brain. The ability of radiation to increase the expression of some MMPs and the invasiveness of cancer cells have also been reported for pancreatic cancer cells (Qian et al, 2002;Ohuchida et al, 2004), melanoma cells (Kaliski et al, 2005), rectal carcinoma cells (Speake et al, 2005), colon carcinoma cells and osteosarcoma cells (Wang et al, 2000).…”

Molecular profiling of angiogenesis with targeted ultrasound imaging: early assessment of antiangiogenic therapy effects

“…Thus, it can be assumed that the reduced density of both markers in the treated tumors is related primarily to the decrease in absolute vessel density and not to a downregulation of the markers by the endothelial cells. However, preceding the decrease in vessel density, MMP inhibition could also cause a down-regulation of VEGFR2 and a v h 3 integrin expression on the endothelial cells [e.g., by inhibition of VEGF release from the matrix (30,31) and ensuing depletion of the positive feedback on VEGFR2 expression]. This might need to be elucidated in further longitudinal in vivo studies with more closely spaced examination intervals, a process for which molecular ultrasound is highly suited.…”