Nuclear localization of CD26 induced by a humanized monoclonal antibody inhibits tumor cell growth by modulating of POLR2A transcription

PLoS One. 2013 Apr 29;8(4):e62304. doi: 10.1371/journal.pone.0062304. Print 2013.

Abstract

CD26 is a type II glycoprotein known as dipeptidyl peptidase IV and has been identified as one of the cell surface markers associated with various types of cancers and a subset of cancer stem cells. Recent studies have suggested that CD26 expression is involved in tumor growth, tumor invasion, and metastasis. The CD26 is shown in an extensive intracellular distribution, ranging from the cell surface to the nucleus. We have previously showed that the humanized anti-CD26 monoclonal antibody (mAb), YS110, exhibits inhibitory effects on various cancers. However, functions of CD26 on cancer cells and molecular mechanisms of impaired tumor growth by YS110 treatment are not well understood. In this study, we demonstrated that the treatment with YS110 induced nuclear translocation of both cell-surface CD26 and YS110 in cancer cells and xenografted tumor. It was shown that the CD26 and YS110 were co-localized in nucleus by immunoelectron microscopic analysis. In response to YS110 treatment, CD26 was translocated into the nucleus via caveolin-dependent endocytosis. It was revealed that the nuclear CD26 interacted with a genomic flanking region of the gene for POLR2A, a subunit of RNA polymerase II, using a chromatin immunoprecipitation assay. This interaction with nuclear CD26 and POLR2A gene consequently led to transcriptional repression of the POLR2A gene, resulting in retarded cell proliferation of cancer cells. Furthermore, the impaired nuclear transport of CD26 by treatment with an endocytosis inhibitor or expressions of deletion mutants of CD26 reversed the POLR2A repression induced by YS110 treatment. These findings reveal that the nuclear CD26 functions in the regulation of gene expression and tumor growth, and provide a novel mechanism of mAb-therapy related to inducible translocation of cell-surface target molecule into the nucleus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus
  • Animals
  • Antibodies, Monoclonal, Humanized / immunology*
  • Cell Line, Tumor
  • Cell Nucleus / metabolism*
  • Cell Proliferation
  • Cell Transformation, Neoplastic
  • Dipeptidyl Peptidase 4 / immunology*
  • Dipeptidyl Peptidase 4 / metabolism*
  • Extracellular Space / metabolism
  • Genomics
  • Humans
  • Lung Neoplasms / genetics
  • Lung Neoplasms / pathology
  • Mesothelioma / genetics
  • Mesothelioma / pathology
  • Mesothelioma, Malignant
  • Mice
  • RNA Polymerase II / genetics*
  • Transcription, Genetic*

Substances

  • Antibodies, Monoclonal, Humanized
  • RNA Polymerase II
  • Dipeptidyl Peptidase 4

Grants and funding

This study was supported by the Program for Promotion of Fundamental Studies in Health Sciences of the National Institute of Biomedical Innovation (07–17 to T.Y. and C.M.), a Grant-in-Aid for Scientific Research (B) (23390086 to T.Y. and 22790355 to M.H.) and Global COE Program “Education and Research Center for Stem Cell Medicine” (to K.Y.) from the Ministry of Education, Culture, Sports, Science and Technology of Japan, and a Grant-in-Aid for Drug Design Biomarker Research (H24-B10-003 to T.Y. and C.M.) from the Ministry of Health, Labor and Welfare. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.