Abstract LB-30: Membrane-anchored MT1-MMP downstream of p63 is essential for the transition of in situ to invasive breast carcinoma
Authors: Lodillinsky Catalina , Infante Elvira , Fuhrmann Laetitia , Guichard Alan , Cyrta Joanna , Lagoutte Emilie , Irondelle Marie , Vacher Sophie , Bieche Ivan , Glukhova Marina , Vincent-Salomon Anne , Chavrier Philippe 
Published: May 2015

Abstract
Understanding breast tumor progression requires insights both at the molecular and cellular levels. In particular, the transition of ductal carcinoma in situ (DCIS) to invasive ductal carcinoma (IDC) is a key, yet poorly understood event. Membrane-Type 1 matrix metalloproteinase (MT1-MMP) is critical for pericellular remodelling of the basement membrane and interstitial collagen during invasion by carcinoma cells.
The role of MT1-MMP during the transition from DCIS to IDC was investigated using an intraductal human-in-mouse xenograft model. Breast tumor-derived MCF10.DCIS.com cells, which express MT1-MMP were injected into the primary mammary ducts of female SCID mice. Histological analysis revealed a progression from DCIS, to microinvasive and invasive lesions by 5, 7-8 and 10-12 weeks post-injection, respectively. Immunohistochemistry (IHC) staining showed homogeneous expression of MT1-MMP over the tumor section at DCIS stage, and up-regulation at the edge of the tumours at microinvasive and invasive states. In microinvasives lesion, up-regulation of MT1-MMP in tumour cells coincided with disruption of the basement membrane. At later stages, one characteristic of invasive lesions is the increase in collagen fibers deposition. Interestingly, MT1-MMP expression was also increased at the front of infiltrating tumours in contact with the stroma.
After 10 weeks, intraductally injected cells knocked down for MT1-MMP developed invasive tumours only in 20% of injected mammary glands, while 100% of glands injected with control cells developed infiltrating lesions. All together, these results demonstrated that MT1-MMP is instrumental for the transition from in situ to invasive breast tumours.
IHC staining revealed a strong correlation of the expression of the basal marker p63 and MT1-MMP in tumour cells both at the microinvasive and invasive stages. One hypothesis was that contact of tumor cells with the stroma triggered induction of p63 that in turn up-regulated MT1-MMP. Along this line, we found that MCF10.DCIS.com cells plated on type I collagen up-regulated p63 and MT1-MMP, both at the mRNA and protein levels, while silencing of p63 abolished collagen-dependent MT1-MMP increase. At the functional level, silencing of MT1-MMP or p63 inhibited invasion of multicellular spheroids into 3D type collagen as well as the cells capacity to degrade collagen I fibers.
Finally, MT1-MMP expression was analysed by IHC staining on human tissue microarray comprising 432 IDCs, 40 microinfiltrated lesions and 68 DCIS. MT1-MMP was upregulated in IDC as compared to DCIS. Invasive triple-negative breast (TNBC) and grade III tumours expressed highest MT1-MMP levels. To our knowledge, this is the first demonstration that up-regulation of MT1-MMP is associated with invasiveness, histopathologic grade and molecular subtypes in human breast cancer. We also observed 10% of TNBC expressing p63 and found a positive correlation with MT1-MMP expression suggesting an interplay between p63 and MT1-MMP during progression.
Citation Format: Catalina Lodillinsky, Elvira Infante, Laetitia Fuhrmann, Alan Guichard, Joanna Cyrta, Emilie Lagoutte, Marie Irondelle, Sophie Vacher, Ivan Bieche, Marina Glukhova, Anne Vincent-Salomon, Philippe Chavrier. Membrane-anchored MT1-MMP downstream of p63 is essential for the transition of in situ to invasive breast carcinoma. [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 LB-30. doi:10.1158/1538-7445.AM2014-LB-30