A mitochondrial ROS pathway controls matrix metalloproteinase 9 levels and invasive properties in RAS‐activated cancer cells

Abstract

Matrix metalloproteinases (MMPs) are tissue‐remodeling enzymes involved in the processing of various biological molecules. MMPs also play important roles in cancer metastasis, contributing to angiogenesis, intravasation of tumor cells, and cell migration and invasion. Accordingly, unraveling the signaling pathways controlling MMP activities could shed additional light on cancer biology. Here, we report a molecular axis, comprising the molecular adaptor hydrogen peroxide‐inducible clone‐5 (HIC‐5), NADPH oxidase 4 (NOX4), and mitochondria‐associated reactive oxygen species (mtROS), that regulates MMP9 expression and may be a target to suppress cancer metastasis. We found that this axis primarily downregulates mtROS levels which stabilize MMP9 mRNA. Specifically, HIC‐5 suppressed the expression of NOX4, the source of the mtROS, thereby decreasing mtROS levels and, consequently, destabilizing MMP9 mRNA. Interestingly, among six cancer cell lines, only EJ‐1 and MDA‐MB‐231 cells exhibited upregulation of NOX4 and MMP9 expression after shRNA‐mediated HIC‐5 knockdown. In these two cell lines, activating RAS mutations commonly occur, suggesting that the HIC‐5–mediated suppression of NOX4 depends on RAS signaling, a hypothesis that was supported experimentally by the introduction of activated RAS into mammary epithelial cells. Notably, HIC‐5 knockdown promoted lung metastasis of MDA‐MB‐231 cancer cells in mice. The tumor growth of HIC‐5–silenced MDA‐MB‐231 cells at the primary sites was comparable to that of control cells. Consistently, the invasive properties of the cells, but not their proliferation, were enhanced by the HIC‐5 knockdown in vitro. We conclude that NOX4‐mediated mtROS signaling increases MMP9 mRNA stability and affects cancer invasiveness but not tumor growth.

On elucidation of the role of mitochondria dysfunction and oxidative stress in multiple sclerosis

“…142 MMP members particularly MMP-7 and MMP-9, have been shown to play a role in the disruption of the blood-brain barrier (BBB) in MS and the chronicity of the disease. [143][144][145][146] Notably, Mitochondria, ROS, and OS are key regulators of MMP production [147][148][149][150] and antioxidant treatment has been shown to suppress MMA secretion and activity. 151,152…”

Regulation of mitochondrial ROS production by HIC‐5: a common feature of oncogene‐induced senescence and tumor invasiveness?

“…By examination of six tumor cell lines transformed by different oncogenes, Mori et al . observed the inhibitory function of HIC‐5 on MMP9 expression in MDA‐MB‐231 breast cancer cells and the colon cancer cell line EJ‐1 . Since only these two cancer cell lines, but none of the others, contain activated H‐RAS or K‐RAS oncogenes, the authors speculate that HIC‐5 requires activated RAS to mediate its effect on NOX4, a notion which was further supported by the acquisition of this phenotype by mammary epithelial cells after transformation with H‐RAS.…”

“…In order to explain this discrepancy, Mori et al . speculate the prevalence of a short‐term metastasis‐promoting effect of HIC‐5 via its effect on RhoA signaling followed by a long‐term protecting effect mediated by downregulation of MMP9 .…”

“…As now described in the paper by Mori et al . published in this issue of the FEBS Journal, one of the actions of HIC‐5 is to downregulate NADPH oxidase 4 (NOX4), a membrane‐bound protein reported to localize to various subcellular sites, including the plasma membrane, the endoplasmic reticulum membrane, and the mitochondria. As cellular localization studies with NOX4 are usually performed by immunofluorescence assays, the choice of the appropriate antibodies is crucial, and only a few reliable antibodies are currently available .…”

“…In this manuscript, evidence was presented for a posttranslational mechanism involving ubiquitin‐proteasomal system‐mediated degradation of NOX4 promoted by the association of the HIC‐5 protein with the ubiquitin ligase Cbl‐c and the ubiquitin‐binding protein heat shock protein 27. Destabilization of NOX4 mRNA by HIC‐5 is proposed as another mode of interaction of these two proteins . A model explaining how NOX4 may increase mtROS production was proposed based on the finding that NOX4 inactivates complex I of the mitochondrial electron transport chain in human endothelial cells; however, if this mechanism is also effective in the cell types used in the study by Mori et al .…”