CD9 negatively regulates CD26 expression and inhibits CD26-mediated enhancement of invasive potential of malignant mesothelioma cells

Our plain-English summary of CD9 negatively regulates CD26 expression and inhibits CD26-mediated enhancement of invasive potential of malignant mesothelioma cells, by T. Okamoto, S. Iwata, H. Yamazaki, et al (PloS One, 2014).

The study

• Authors: T. Okamoto, S. Iwata, H. Yamazaki, R. Hatano, E. Komiya, N.H. Dang, K. Ohnuma, C. Morimoto
• Journal: PloS One
• Published: 2014;9(1):e86671
• Cited by: 30 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

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.

In plain English

This was a laboratory study of human malignant mesothelioma cell lines (ACC-MESO1, MSTO-211H, NCI-H2452, NCI-H226) together with a xenograft experiment in female SCID mice; asbestos was mentioned only in the introduction as the usual background of pleural mesothelioma, and no people were studied. The authors manipulated the cell surface molecules CD26 (dipeptidyl peptidase IV) and CD9 by small interfering and short hairpin RNA, by transfecting CD26 or CD9 genes, and by treating cells with anti-CD26 and anti-CD9 monoclonal antibodies. CD26 and CD9 co-precipitated with each other, and their expression moved in opposite directions: removing CD26 raised CD9 and removing CD9 raised CD26. Cells carrying CD26 invaded through Matrigel more than CD26-negative cells, and CD9 removal increased invasion further; alpha5beta1 integrin co-precipitated with CD26 but not CD9, and antibodies to alpha5 or beta1 reduced invasion and migration. Depleting CD26, CD9, or both reduced cell growth in culture and tumour growth in mice. The authors concluded that CD26 and CD9 interact to govern mesothelioma behaviour and may be biomarkers and treatment targets.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory (in vitro) study of human mesothelioma cell lines with gene knockdown, gene transfer, antibody treatment, microarray, and an in vivo mouse xenograft experiment
• Who was studied: Human malignant mesothelioma cell lines ACC-MESO1 (MESO1), MSTO-211H (including a CD26 transfectant), NCI-H2452 and NCI-H226, plus female SCID mice aged 5-6 weeks inoculated subcutaneously with mesothelioma cells
• Exposure: Not an exposure study in people; the manipulations were siRNA/shRNA depletion of CD26 or CD9, transfection of CD26 or CD9 cDNA, and treatment with humanized anti-CD26 and anti-CD9 monoclonal antibodies (10 mg/ml in vitro; 8 mg/kg in mice)
• Main results:
  • CD26 and CD9 co-precipitated in MESO1 cells and in CD26-transfected MSTO-211H cells
  • Expression of the two molecules moved inversely: knocking down CD26 raised surface CD9, knocking down CD9 raised surface CD26 (in MESO1 cells)
  • Transfecting CD26 into CD26-negative MSTO-211H cells reduced CD9 at protein and gene level
  • In the Boyden chamber invasion assay, CD26-transfected MSTO cells invaded far more than CD26-negative MSTO-Wild cells; CD26 knockdown reduced invasion (figure legend gives p less than 0.005 and p less than 0.001)
  • Knocking down CD9, or treating with anti-CD9 antibody, increased invasion and migration of CD26-positive cells but not of CD26-negative MSTO-Wild cells
  • Alpha5beta1 integrin co-precipitated with CD26 but not with CD9, and antibodies to alpha5 or beta1 integrin inhibited invasion and migration of MESO1 and MSTO-CD26(+) cells
  • CD26 depletion lowered, and CD9 depletion raised, protein levels of FAK and Cas-L; CD9 depletion also increased their tyrosine phosphorylation
  • Combining anti-CD26 and anti-CD9 antibodies inhibited invasion of MSTO-CD26(+) and MESO1 cells, although anti-CD9 antibody alone increased invasion
  • In SCID mice given MESO1 cells, shRNA depletion of CD26 or of CD9 reduced tumour growth at day 14, with the greatest suppression when both were depleted (5 tumours per group)
• The authors' conclusion: The authors concluded that the interaction between CD26 and CD9 mediates mesothelioma behaviour and that both molecules may serve as biomarkers and as molecular targets for future treatment
• Limitations the authors state:
  • The authors stated that where CD26, CD9 and integrins sit within membrane microdomains was not established by this work
  • The authors noted their integrin findings conflicted with earlier ovarian carcinoma work and offered cell origin as a possible explanation

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelioma, Glycoprotein, STEM, Biomarker.

Related studies

• CD26-mediated regulation of periostin expression contributes to migration and invasion of malignant pleural mesothelioma cells — E. Komiya, K. Ohnuma, et al. (2014)
• Identification of cancer stem cell markers in human malignant mesothelioma cells — F.I. Ghani, H. Yamazaki, et al. (2011)
• CD9 expression as a favorable prognostic marker for patients with malignant mesothelioma — V.J. Amatya, Y. Takeshima, et al. (2013)
• The small GTPase RhoA regulates the expression and function of the sodium channel Nav1.5 in breast cancer cells — C. Dulong, Y.J. Fang, et al. (2014)
• AHNAK is highly expressed and plays a key role in cell migration and invasion in mesothelioma — H. Sudo, A.B. Tsuji, et al. (2014)
• Establishment of monoclonal anti-human CD26 antibodies suitable for immunostaining of formalin-fixed tissue — R. Hatano, T. Yamada, et al. (2014)

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