Abstract 5266: TGF-β1 modulates the homeostasis between MMPs and MMPs inhibitors through p38 MAPK and ERK½ in highly invasive human breast cancer cells

Abstract

Abstract Matrix metalloproteinases (MMPs) and their specific inhibitors, known as tissue inhibitors of MMPs (TIMPs) and the membrane-associated MMP inhibitor (RECK), are involved in several steps of the metastatic process. Previous results from our laboratory showed a positive correlation between high mRNA expression levels of MMPs and their inhibitors upon breast cancer progression, both in cellular models and in tumor tissue samples. However, the molecular mechanisms underlying this coordinate regulation of MMPs, TIMPs and RECK expression remain unknown. Since transforming growth factor beta 1 (TGF-β1) has been related to mechanisms which regulate the expression of some MMPs and MMPs inhibitors in different models, we investigated whether this multifunctional cytokine could have a role as a common regulator of MMPs, TIMPs and RECK in the human breast cancer model. The mRNA expression levels of TGF-β isoforms and their receptors were examined, by qRT-PCR, in a panel of five human breast cancer cell lines displaying different degrees of invasiveness and metastatic potential. We demonstrated that TGF-β1, TGF-β2 and TβRII are significantly overexpressed in more aggressive mammary cell lines. Furthermore, using the Spearman correlation test, we showed a significantly positive correlation between the mRNA expression levels of TGF-β1 and MMP-2, MMP-14, TIMP-1, TIMP-3 and RECK. In addition, upon treatment with TGF-β1, the MDA-MB-231 breast cancer cell line presented significantly increased mRNA expression levels of MMP-2, MMP-9, MMP-14, TIMP-2 and RECK. TGF-β1 was also able to induce the protein expression levels of MMP-2, MMP-9, MMP-14 and TIMP-2. On the other hand, RECK protein expression was significantly downregulated in TGF-β1-treated-MDA-MB-231 cells. In addition to the classical TGF-β-induced signal transduction by Smads, it is well known that this cytokine also signals in a Smad-independent manner, by induction of other pathways. Here, we analyzed the involvement of p38 MAPK and ERK½, two well established Smad-independent pathways, in the proposed mechanism of coordinate regulation of MMPs, TIMPs and RECK by TGF-β1 in the breast cancer model. Firstly, we confirmed that TGF-β1 is able to induce phosphorylation of p38MAPK and ERK½ proteins in the MDA-MB-231 cell line. Inhibition of ERK½ pathway led to increased levels of the MMPs inhibitors (TIMP-2 and RECK) mRNA in MDA-MB-231 cells treated (or not) with TGF-β1. In contrast, cells treated with a pharmacological p38MAPK inhibitor showed blockage of TGF-β1-induced mRNA expression of MMPs (MMP-2, MMP-9 and MMP-14) and MMPs inhibitors (TIMP-2 and RECK). Altogether, our results suggest that the balance between p38MAPK and ERK½ activities mediates the role of TGF-β1 as an important homeostasis regulator between MMPs and MMPs inhibitors in the MDA-MB231 breast cancer cell line. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5266. doi:10.1158/1538-7445.AM2011-5266