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Biochem Biophys Res Commun. 2015 Sep 25;465(3):338-43. doi: 10.1016/j.bbrc.2015.07.142. Epub 2015 Aug 1.

Intracellular distribution of TM4SF1 and internalization of TM4SF1-antibody complex in vascular endothelial cells.

Author information

1
Center for Vascular Biology Research and Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, USA.
2
Department of Molecular and Cellular Biology, Harvard University, USA.
3
Department of Pharmacology, Shanxi Medical University, Xinjiannanlu 56, Shanxi Province, Taiyuan 030001, China.
4
Center for Vascular Biology Research and Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, USA. Electronic address: hdvorak@bidmc.harvard.edu.
5
Center for Vascular Biology Research and Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, USA. Electronic address: sjaminet@bidmc.harvard.edu.

Abstract

Transmembrane-4 L-six family member-1 (TM4SF1) is a small plasma membrane-associated glycoprotein that is highly and selectively expressed on the plasma membranes of tumor cells, cultured endothelial cells, and, in vivo, on tumor-associated endothelium. Immunofluorescence microscopy also demonstrated TM4SF1 in cytoplasm and, tentatively, within nuclei. With monoclonal antibody 8G4, and the finer resolution afforded by immuno-nanogold transmission electron microscopy, we now demonstrate TM4SF1 in uncoated cytoplasmic vesicles, nuclear pores and nucleoplasm. Because of its prominent surface location on tumor cells and tumor-associated endothelium, TM4SF1 has potential as a dual therapeutic target using an antibody drug conjugate (ADC) approach. For ADC to be successful, antibodies reacting with cell surface antigens must be internalized for delivery of associated toxins to intracellular targets. We now report that 8G4 is efficiently taken up into cultured endothelial cells by uncoated vesicles in a dynamin-dependent, clathrin-independent manner. It is then transported along microtubules through the cytoplasm and passes through nuclear pores into the nucleus. These findings validate TM4SF1 as an attractive candidate for cancer therapy with antibody-bound toxins that have the capacity to react with either cytoplasmic or nuclear targets in tumor cells or tumor-associated vascular endothelium.

KEYWORDS:

Antibody drug conjugate; Antibody internalization; Endothelial cells; Microtubules; TM4SF1

PMID:
26241677
PMCID:
PMC4579096
DOI:
10.1016/j.bbrc.2015.07.142
[Indexed for MEDLINE]
Free PMC Article

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