MOLECULAR CARCINOGENESIS Evidence of MTCBP-1 Interaction With the Cytoplasmic Domain of MT1-MMP: Implications in the Autophagy Cell Index of High-Grade Glioblastoma Jonathan Pratt, 1 Mustapha Iddir, 1 Steve Bourgault, 2 and Borhane Annabi 1 * 1 Laboratoire d’Oncologie Mol  eculaire, Centre de recherche Biomed, Quebec, Canada 2 Centre de recherche Pharmaqam, D epartement de Chimie, Universit e du Qu ebec a ` Montr eal, Quebec, Canada Progression of astrocytic tumors is, in part, related to their dysregulated autophagy capacity. Recent evidence indicates that upstream autophagy signaling events can be triggered by MT1-MMP, a membrane-bound matrix metalloproteinase that contributes to the invasive phenotype of brain cancer cells. The signaling functions of MT1-MMP require its intracellular domain, and recent identification of MTCBP-1, a cytoplasmic 19 kDa protein involved in the inhibition of MT1- MMP-mediated cell migration, suggests that modulation of MT1-MMP cytoplasmic domain-mediated signaling may affect other carcinogenic processes. Using qPCR and screening of cDNA generated from brain tumor tissues of grades I, II, III, and IV, MT1-MMP gene expression was found to correlate with increased grade of tumors. Inversely, MTCBP-1 expression decreased with increasing grade of brain tumor. Confocal microscopy and fluorescence resonance energy transfer (FRET) analysis revealed that overexpressing a cytoplasmic-deleted MT1-MMP recombinant protein mutant prevented MTCBP-1 recruitment to the intracellular leaf of plasma membrane in U87 glioblastoma cells. The interaction between MTCBP-1 and the 20 amino acids peptide representing the MT1-MMP cytoplasmic domain was confirmed by surface plasmon resonance. Overexpression of a full-length Wt-MT1-MMP triggered acidic autophagy vesicle formation and autophagic puncta formation for green fluorescent microtubule-associated protein 1 light chain 3 (GFP-LC3). Autophagic vesicles and GFP-LC3 puncta formation were abrogated in the presence of MTCBP-1. Our data elucidate a new role for MTCBP-1 regulating the intracellular function of MT1-MMP-mediated autophagy. The inverse correlation between MTCBP-1 and MT1-MMP expression with brain tumor grades could also contribute to the decreased autophagic index observed in high-grade tumors. © 2015 Wiley Periodicals, Inc. Key words: Brain tumor; matrix metalloproteinase; chemoresistance INTRODUCTION Astrocytic tumors are the most common primary brain tumor type in humans. The World Health Organization (WHO) classifies pilocytic astrocytoma multiforme as grade I, diffuse astrocytoma as grade II, anaplastic astrocytoma as grade III, and glioblastoma multiforme as grade IV [1]. Progression from a low (I and II)- to a high (III and IV)-grade tumor has been associated with various molecular alterations [2]. Among these alterations, defective autophagy, shown via reduced expression of the Beclin-1 and LC3B-II autophagy biomarkers, has been suggested to cor- relate with reduced survival times of patients with astrocytic tumors [3]. On the other hand, induction of autophagy processes by pro-autophagic drugs is also becoming an emerging concept to trigger cell death in high-grade gliomas and to exploit caspase-indepen- dent programmed cell death pathways for the development of novel brain tumor therapies [4]. Although high-grade gliomas are characterized with reduced expression of autophagy-related proteins when compared to low-grade gliomas, it is still unclear whether dysregulation of autophagy in advanced brain cancer would promote survival or death upon various therapeutic settings. A low autophagy index in tumorigenesis has been inferred by recent studies where autophagic capacity was decreased during the progression of many tumors. Supporting this, autophagy could be induced in those tumors by numerous anti-tumor agents, Abbreviations: CNS, central nervous system; ER, Endoplasmic reticulum; FRET, Fluorescence resonance energy transfer; GFP- LC3Green, fluorescent microtubule-associated; MT1-MMP, Mem- brane type-1 matrix metalloproteinase; MTCBP-1Membrane-type, 1 matrix; SPR, Surface plasmon resonance; TIMP-2, Tissue inhibitor of metalloproteinase-2; WHO, World health organization. Conflict of interest: The authors declare that they have no competing interests. Authors’ contributions: J.P., S.B., and B.A. designed this study. J.P. performed all the experiments, except the SPR analysis which were performed by M.I. J.P. and S.B. performed and carried out the FRET data analysis. All authors have contributed to data analysis, discussions, and interpretations of the results. All authors have read and approved the final manuscript. Grant sponsor: NSERC; Grant number: #288249 *Correspondence to: Borhane Annabi, Laboratoire d'Oncologie Mol eculaire, Universit e du Qu ebec à Montr eal, C.P. 8888, Succ. Centre-ville, Montr eal, Qu ebec, H3C 3P8, Canada. Received 24 September 2014; Accepted 17 November 2014 DOI 10.1002/mc.22264 Published online in Wiley Online Library (wileyonlinelibrary.com). ß 2015 WILEY PERIODICALS, INC.