Abstract 5580: Membrane-Type 1 Matrix Metalloproteinase (MT1-MMP): A predictive biomarker of chemotherapy response in osteosarcoma
Authors: Biswas Swethajit , Rankin Kenneth , Long Anna , Nisar Sohail , Gerrand Craig , Dildey Petra , Lunec John 
Published: August 2012

INTRODUCTION: Osteosarcoma (OS) is the most common primary bone sarcoma and affects mainly teenagers & young adults. Although OS survival ∼70% when patients are treated with both chemotherapy and surgery, the improvement in cure rates over the last 25 years has been slow. Given that OS frequently present with lung micrometastasis, proteins which regulate OS cell invasion would be important to identify as putative prognostic/predictive biomarkers, as well as possible drug targets. Membrane-Type 1 Matrix Metalloproteinase (MT1-MMP) is one such protein. MT1-MMP is a membrane tethered MMP that is involved in the regulation of cell invasion since it is a collagenase and regulates MAPK/ERK dependent cell motility. Given that MT1-MMP expression can be upregulated by hypoxia, we investigated the expression of MT1-MMP, as well as hypoxia-inducible factor (HIF) isoforms in 76 primary tumor biopsies from patients who received standard MAP chemotherapy. In vitro, we investigated the effects of hypoxia on MT1-MMP. MATERIALS & METHODS: OS tumors were immunostained for MT1-MMP, HIF-1 and HIF-2. U2OS & SJSA-1 cell lines were used for in vitro studies. Immunoblotting & immunofluoroscence confocal microscopy were performed for MT1-MMP and HIFs at 1% O2 for 8, 12, 24 and 48 hours, compared with normoxia. RESULTS: 71/76 tumors were evaluable for MT1-MMP expression. MT1-MMP was identified in the cytoplasm and nuclei of OS tumors. Only 10/85 tumors demonstrated membrane expression. High expression of cytoplasmic (HR:0.32(95%CI:0.07-0.49);p=0.005) and nuclear (HR:0.21(95%CI:0.09-0.42);p&lt;0.0001) MT1-MMP were independently associated with reduced overall survival. Nuclear, but not cytoplasmic, MT1-MMP was associated with reduced event free survival (EFS) (HR:0.28(95%CI:0.09-0.76);p=0.01). Nuclear MT1-MMP expression was positively correlated with HIF-2 expression (r=0.71;p=0.009). High nuclear HIF-2 expression was associated with reduced overall survival (HR:0.23(95%CI:0.1-0.49);p=0.0002). No effects were demonstrated for HIF-1. In vitro, each cell line expressed MT1-MMP and HIF-2 in normoxia, but this was not upregulated by 1%O2. HIF-1 was stabilized from 4 to 24 hours at 1% O2, but was not detectable &gt;24 hours. In U2OS cells, confocal microscopy & subcellular fractionation immunoblots demonstrated that MT1-MMP and HIF-2 protein translocated to the nucleus from the cytoplasm at 1%O2. HIF-2 co-localized with MT1-MMP in nuclei, but HIF-1 did not. CONCLUSION: Nuclear MT1-MMP is a prognostic and predictive biomarker in OS patients treated with MAP chemotherapy. Since MT1-MMP does not contain a nuclear localization signal (NLS), the in vitro data points to the possibility that HIF-2 might have a novel function as a MT1-MMP nuclear transporter and that MT1-MMP nuclear migration, but not expression, is hypoxia dependent in vitro and might have pro-survival effects on OS cells in vivo.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5580. doi:1538-7445.AM2012-5580