title: The secretion and biological function of tumor suppressor maspin as an exosome cargo protein.
abstract: Maspin is an epithelial-specific tumor suppressor shown to exert its biological effects as an intracellular, cell membrane-associated, and secreted free molecule. A recent study suggests that upon DNA-damaging g-irradiation, tumor cells can secrete maspin as an exosome-associated protein. To date, the biological significance of exosomal secretion of maspin is unknown. The current study aims at addressing whether maspin is spontaneously secreted as an exosomal protein to regulate tumor/stromal interactions. We prepared exosomes along with cell extracts and vesicle-depleted conditioned media (VDCM) from normal epithelial (CRL2221, MCF-10A and BEAS-2B) and cancer (LNCaP, PC3 and SUM149) cell lines. Atomic force microscopy and dynamic light scattering analysis revealed similar size distribution patterns and surface zeta potentials between the normal cells-derived and tumor cells-derived exosomes. Electron microscopy revealed that maspin was encapsulated by the exosomal membrane as a cargo protein. While western blotting revealed that the level of exosomal maspin from tumor cell lines was disproportionally lower relative to the levels of corresponding intracellular and VDCM maspin, as compared to that from normal cell lines, maspin knockdown in MCF-10A cells led to maspin-devoid exosomes, which exhibited significantly reduced suppressive effects on the chemotaxis activity of recipient NIH3T3 fibroblast cells. These data are the first to demonstrate the potential of maspin delivered by exosomes to block tumor-induced stromal response, and support the clinical application of exosomal maspin in cancer diagnosis and treatment.
authors.affiliation: Department of Pathology, Wayne State University School of Medicine, MI, USA.|Department of Oncology, Wayne State University School of Medicine, MI, USA.|The Tumor Biology and Microenvironment Program, Karmanos Cancer Institute, MI, USA.|Current address: Center for Bioengineering and Tissue Regeneration, The University of California San Francisco, San Francisco, CA, USA.
authors.forename: Ivory
authors.initials: I
authors.lastname: Dean
authors.affiliation: Department of Pathology, Wayne State University School of Medicine, MI, USA.|The Tumor Biology and Microenvironment Program, Karmanos Cancer Institute, MI, USA.
authors.forename: Sijana H
authors.initials: SH
authors.lastname: Dzinic
authors.affiliation: Department of Pathology, Wayne State University School of Medicine, MI, USA.|The Tumor Biology and Microenvironment Program, Karmanos Cancer Institute, MI, USA.
authors.forename: M Margarida
authors.initials: MM
authors.lastname: Bernardo
authors.affiliation: Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, MI, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zou
authors.affiliation: Department of Chemical Engineering and Materials Science, Wayne State University, MI, USA.|Current address: Ocular Structure and Imaging Facility, Eye Research Institute, Oakland University, Rochester Hills, MI, USA.
authors.forename: Vickie
authors.initials: V
authors.lastname: Kimler
authors.affiliation: Department of Pathology, Wayne State University School of Medicine, MI, USA.|The Tumor Biology and Microenvironment Program, Karmanos Cancer Institute, MI, USA.|Current address: Zhangjiagang Aoyang Hospital, Nanjing Medical University, Jiangsu, China.
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Pathology, Wayne State University School of Medicine, MI, USA.|The Tumor Biology and Microenvironment Program, Karmanos Cancer Institute, MI, USA.|Current address: Variantyx, Framingham, MA, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Kaplun
authors.affiliation: The Tumor Biology and Microenvironment Program, Karmanos Cancer Institute, MI, USA.|Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, MI, USA.
authors.forename: James
authors.initials: J
authors.lastname: Granneman
authors.affiliation: The Tumor Biology and Microenvironment Program, Karmanos Cancer Institute, MI, USA.|Department of Chemical Engineering and Materials Science, Wayne State University, MI, USA.
authors.forename: Guangzhao
authors.initials: G
authors.lastname: Mao
authors.affiliation: Department of Pathology, Wayne State University School of Medicine, MI, USA.|Department of Oncology, Wayne State University School of Medicine, MI, USA.|The Tumor Biology and Microenvironment Program, Karmanos Cancer Institute, MI, USA.
authors.forename: Shijie
authors.initials: S
authors.lastname: Sheng
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002633:Chemotaxis; D004847:Epithelial Cells / Q000378:metabolism* / Q000648:ultrastructure; D055354:Exosomes / Q000378:metabolism* / Q000648:ultrastructure; D005260:Female; D006801:Humans; D058922:Inflammatory Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D051379:Mice; D041681:NIH 3T3 Cells; D019899:Paracrine Communication; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D021381:Protein Transport; D034622:RNA Interference; D015843:Serpins / Q000235:genetics / Q000378:metabolism*; D017154:Stromal Cells / Q000378:metabolism* / Q000648:ultrastructure; D014162:Transfection; D059016:Tumor Microenvironment; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C085344:SERPIN-B5; D015843:Serpins; D025521:Tumor Suppressor Proteins
keywords: electron microscopy; exosome; exosome cargo; tumor microenvironment; tumor progression