Background: Human blood outgrowth endothelial cells (BOECs), used as cellular vehicles for experimental cancer therapy, infiltrate tumors. Infiltration may determine their therapeutic efficacy. The role of matrix metalloproteinases (MMPs) in BOEC infiltration and its potential enhancement by irradiation were investigated.
Materials and methods: Infiltration of BOECs into spheroids made of tumor cells and fibroblasts was determined in the presence of low-dose EDTA, a potent inhibitor of MMPs. Expression and secretion of MMP-2 and -9 by these tumor cells and tumor-stromal cells were investigated with zymography and immunohistochemistry.
Results: Infiltration of BOECs into spheroids was blocked by low-dose EDTA. Irradiation enhanced secretion of MMP-2 and, less so, of MMP-9 by tumor-stromal cells and tumor cells, and increased the amount of MMP-2 and -9 in subcutaneous LLC tumors. However, irradiation did not increase infiltration by BOECs.
Conclusion: MMPs are involved in the infiltration of BOECs into spheroids. Infiltration of BOECs is not increased by irradiation at the doses employed.