CD9 negatively regulates CD26 expression and inhibits CD26-mediated enhancement of invasive potential of malignant mesothelioma cells.
CD26/dipeptidyl peptidase IV is a cell surface glycoprotein which consists of multiple functional domains beside its ectopeptidase site. A growing body of evidence indicates that elevated expression of CD26 correlates with disease aggressiveness and invasive potential of selected malignancies. To further explore the molecular mechanisms involved in this clinical behavior, our current work focused on the interaction between CD26 and CD9, which were recently identified as novel markers for cancer stem cells in malignant mesothelioma. We found that CD26 and CD9 co-modulated and co-precipitated with each other in the malignant mesothelioma cell lines ACC-MESO1 and MSTO-211H. SiRNA study revealed that depletion of CD26 led to increased CD9 expression, while depletion of CD9 resulted in increased CD26 expression. Consistent with these findings was the fact that gene transfer of CD26 into CD26-negative MSTO-211H cells reduced CD9 expression. Cell invasion assay showed that overexpression of CD26 or gene depletion of CD9 led to enhanced invasiveness, while CD26 gene depletion resulted in reduced invasive potential. Furthermore, our work suggested that this enhanced invasiveness may be partly mediated by α5β1 integrin, since co-precipitation studies demonstrated an association between CD26 and α5β1 integrin. Finally, gene depletion of CD9 resulted in elevated protein levels and tyrosine phosphorylation of FAK and Cas-L, which are downstream of β1 integrin, while depletion of CD26 led to a reduction in the levels of these molecules. Collectively, our findings suggest that CD26 potentiates tumor cell invasion through its interaction with α5β1 integrin, and CD9 negatively regulates tumor cell invasion by reducing the level of CD26-α5β1 integrin complex through an inverse correlation between CD9 and CD26 expression. Our results also suggest that CD26 and CD9 serve as potential biomarkers as well as promising molecular targets for novel therapeutic approaches in malignant mesothelioma and other malignancies.
Department of Therapy Development and Innovation for Immune disorders and Cancers, Graduate School of Medicine, Juntendo University, Tokyo, Japan ; Division of Clinical Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
Toshihiro
T
Okamoto
Department of Therapy Development and Innovation for Immune disorders and Cancers, Graduate School of Medicine, Juntendo University, Tokyo, Japan ; Division of Clinical Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
Satoshi
S
Iwata
Department of Therapy Development and Innovation for Immune disorders and Cancers, Graduate School of Medicine, Juntendo University, Tokyo, Japan ; Division of Clinical Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
Hiroto
H
Yamazaki
Department of Therapy Development and Innovation for Immune disorders and Cancers, Graduate School of Medicine, Juntendo University, Tokyo, Japan ; Division of Clinical Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
Ryo
R
Hatano
Department of Therapy Development and Innovation for Immune disorders and Cancers, Graduate School of Medicine, Juntendo University, Tokyo, Japan.
Eriko
E
Komiya
Division of Hematology and Oncology, University of Florida Shands Cancer Center, Gainesville, Florida, United States of America.
Nam H
NH
Dang
Department of Therapy Development and Innovation for Immune disorders and Cancers, Graduate School of Medicine, Juntendo University, Tokyo, Japan ; Division of Clinical Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
Kei
K
Ohnuma
Department of Therapy Development and Innovation for Immune disorders and Cancers, Graduate School of Medicine, Juntendo University, Tokyo, Japan ; Division of Clinical Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
Chikao
C
Morimoto
D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement; D049109:Cell Proliferation; D018819:Dipeptidyl Peptidase 4 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D047468:Immunoprecipitation; D019012:Integrin beta1 / Q000235:genetics / Q000378:metabolism; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000517:prevention & control*; D008654:Mesothelioma / Q000378:metabolism / Q000473:pathology* / Q000517:prevention & control*; D000086002:Mesothelioma, Malignant; D051379:Mice; D016513:Mice, SCID; D009361:Neoplasm Invasiveness; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D060245:Tetraspanin 29 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
C554869:CD9 protein, human; D019012:Integrin beta1; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D060245:Tetraspanin 29; C042807:DPP4 protein, human; D018819:Dipeptidyl Peptidase 4