Abstract 30: Modulating the angiogenic potential of human microvascular endothelial cells by an endogenous zinc finger transcription factor, ZNF24

Abstract

Abstract Angiogenesis, the formation of new blood vessels from preexisting ones, is an indispensible process under normal physiological conditions such as embryonic development, certain stages of the female reproductive cycle and placenta formation during pregnancy as well as under pathological conditions such as wound healing, diabetic retinopathy, and cancer initiation, progression and metastasis. We have previously identified the molecular mechanism by which a zinc finger transcription factor, ZNF24, functions as a new inhibitor of tumor angiogenesis. ZNF24 represses the transcription of vascular endothelial growth factor (VEGF) in breast cancer cells via direct binding to an 11-bp fragment within the VEGF proximal promoter. In the current study, we have focused on the role of ZNF24 in modulating the angiogenic potential of the endothelial compartment of the tumor microenvironment. Utilizing primary human microvascular endothelial cells, we have found that silencing ZNF24 in these cells leads to significantly decreased endothelial cell proliferation. Quantitative real-time PCR array analyses have identified multiple cell cycle regulators as potential downstream targets of ZNF24, which may be responsible for the decreased proliferation in these cells. Moreover, knockdown of ZNF24 in microvascular endothelial cells leads to significantly decreased cell migration and invasion. Consistently, we found that VEGFR2 signaling and the proteolytic activity of matrix metalloproteinase-2 (MMP2) were significantly downregulated in these cells. We also determined the effect of ZNF24 silencing on the levels of major regulators of MMP2 proteolytic activity such as the tissue inhibitors of metalloproteinases (TIMPs) and other MMPs. Knockdown of ZNF24 does not induce significant changes in levels of these TIMPs and MMPs, suggesting that ZNF24 regulates MMP2 at the transcriptional level. Indeed, the mRNA level of MMP2 is significantly decreased in cells transfected with ZNF24 siRNA, indicating that ZNF24 may be potentiating endothelial cell invasion by positively regulating MMP2 transcription. In a pilot in vivo angiogenesis assay, knockdown of ZNF24 in microvascular endothelial cells leads to the significantly decreased formation of vascular networks when co-implanted with bone marrow-derived mesenchymal progenitor cells in immunodeficient mice. Taken together, these results demonstrate that ZNF24 may be playing an essential role in modulating the angiogenic potential of microvascular endothelial cells by regulating the proliferation and motility of these cells. (Supported by NIH P01 CA045548 and the Breast Cancer Research Foundation) Citation Format: Di Jia, Lan Huang, Joyce Bischoff, Marsha Moses. Modulating the angiogenic potential of human microvascular endothelial cells by an endogenous zinc finger transcription factor, ZNF24. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 30. doi:10.1158/1538-7445.AM2014-30