Abstract 1116: The role of ADAM9 and PI3K-dependent NF-kappa B pathway in promoting metastasis of triple-negative breast cancer
Authors: Zhou Rui , Zhang Hong , Cho Chi Shing , Wong Sze Chuen , Tian Mei , Chan Wing Chi 
Published: August 2019

Abstract
Objectives:
As a zinc-dependent proteinase family member, A Disintegrin and Metalloproteinase 9 (ADAM9) has the metalloproteinase domain that performs proteolytic function to liberate or shed factors, such as bFGF, VEGF, EGF, TGF-α and IGF, from cell surface and make them more accessible to tumor cells. It was shown in previous studies that the upregulation of ADAM9 in breast cancer is associated with metastasis.
In this study, we examined the effect of ADAM9 on the cell proliferation, migration and invasion and elucidated the molecular mechanism in TNBC. We hypothesize that ADAM9 sheds Tumor Necrosis Factor alpha (TNF-α), which activates TNF receptor and then triggers PI3K-dependent NF-kappa B pathway, affecting metastatic phenotypes of triple negative breast cancer (TNBC).
Materials and Methods:
Correlation of the levels of ADAM9 expression and survival time in triple negative breast cancer patients was analysed by the Kaplan-Meier (KM) plotter integrative data analysis tool. The TNBC subjects were divided into two groups of high and low ADAM9 expression levels with respect to the median. We also compared the protein expression levels of ADAM9 in a highly aggressive, invasive and poorly differentiated TNBC cell line, MDA-MB-231, and a non-tumorigenic epithelial cell line, MCF-10A.
ADAM9 was knocked down in MDA-MB-231 using siRNA. In comparison to negative and blank controls, we examined the cell proliferation, migration and invasion, and the phosphorylation levels of AKT subject to ADAM9 knockdown. We also profiled the mRNA expression levels of ADAM9 and NF-kappa B in breast cancer patients.
Results:
As shown in Figure 1(a), the survival curves of these two groups were plotted and compared using Kaplan-Meier survival analysis, indicating that lower ADAM9 expression is linked to better survival rate (p=0.0038). Figure 1(b) illustrates significantly higher ADAM9 protein level in MDA-MB-231, compared with MCF-10A (p=0.0019).
It is shown in Figure 2 and Figure 3(a) that the cell proliferation, migration and invasion, and the phosphorylation of AKT are significantly suppressed by ADAM9 knockdown in the aggressive TNBC cell line. Figure 3(b) shows significant association between ADAM9 and NF-kappa B in the mRNA expression level (p&lt;0.001).
Conclusions:
The results clearly showed the activation of PI3K-dependent NF-kappa B pathway triggered by ADAM9. This suggests a novel molecular mechanism that the stable homotrimers of TNF-α are released from the membrane through the proteolytic cleavage by ADAM9 and activate the signaling pathway leading to metastatic phenotype of TNBC.
Acknowledgments:
This project was supported by the National Basic Research Program of China (973 program, 2014CB744505).
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Citation Format: Rui Zhou, Hong Zhang, Chi Shing Cho, Sze Chuen Wong, Mei Tian, Wing Chi Chan. The role of ADAM9 and PI3K-dependent NF-kappa B pathway in promoting metastasis of triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1116.