Podoplanin promotes progression of malignant pleural mesothelioma by regulating motility and focus formation

Our plain-English summary of Podoplanin promotes progression of malignant pleural mesothelioma by regulating motility and focus formation, by S. Takeuchi, K. Fukuda, T. Yamada, et al (Cancer Science, 2017).

The study

• Authors: S. Takeuchi, K. Fukuda, T. Yamada, S. Arai, S. Takagi, G. Ishii, A. Ochiai, S. Iwakiri, K. Itoi, H. Uehara, H. Nishihara, N. Fujita, S. Yano
• Journal: Cancer Science
• Published: 2017;108(4):696-703
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant pleural mesothelioma (MPM) is characterized by dissemination and aggressive growth in the thoracic cavity. Podoplanin (PDPN) is an established diagnostic marker for MPM, but the function of PDPN in MPM is not fully understood. The purpose of this study was to determine the pathogenetic function of PDPN in MPM. Forty-seven of 52 tumors (90%) from Japanese patients with MPM and 3/6 (50%) MPM cell lines tested positive for PDPN. Knocking down PDPN in PDPN-high expressing MPM cells resulted in decreased cell motility. In contrast, overexpression of PDPN in PDPN-low expressing MPM cells enhanced cell motility. PDPN stimulated motility was mediated by activation of the RhoA/ROCK pathway. Moreover, knocking down PDPN with short hairpin (sh) RNA in PDPN-high expressing MPM cells resulted in decreased development of a thoracic tumor in mice with severe combined immune deficiency (SCID). In sharp contrast, transfection of PDPN in PDPN-low expressing MPM cells resulted in an increase in the number of Ki-67-positive proliferating tumor cells and it promoted progression of a thoracic tumor in SCID mice. Interestingly, PDPN promoted focus formation in vitro, and a low level of E-cadherin expression and YAP1 activation was observed in PDPN-high MPM tumors. These findings indicate that PDPN is a diagnostic marker as well as a pathogenetic regulator that promotes MPM progression by increasing cell motility and inducing focus formation. Therefore, PDPN might be a pathogenetic determinant of MPM dissemination and aggressive growth and may thus be an ideal therapeutic target.

© 2017 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.

In plain English

This laboratory study examined what podoplanin (PDPN), an established diagnostic marker for malignant pleural mesothelioma (MPM), does in the disease. The authors stained tumours from 52 Japanese patients with MPM using the D2-40 antibody and screened six human MPM cell lines, then altered PDPN levels in selected lines and implanted those modified cells into the thoracic cavity of SCID mice. Forty-seven of 52 tumours (90%) were PDPN-positive, and 3 of 6 cell lines (H226, H2452, EHMES-1) expressed high PDPN. Knocking down PDPN with siRNA or shRNA in high-expressing H226 cells reduced cell motility without changing viability, while transfecting PDPN into low-expressing MSTO-211H cells increased motility; RhoA-GTP binding changed in the same direction, and two ROCK inhibitors reduced motility dose-dependently. In the mice, PDPN knockdown in H226 cells reduced tumour burden, and PDPN transfection into MSTO-211H cells increased tumour burden, Ki-67-positive cells, and shortened survival (P < 0.001, log-rank). PDPN also promoted focus formation, lowered E-cadherin, and increased nuclear YAP1. The authors concluded PDPN promotes MPM progression and is a potential therapeutic target.

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 study combining immunohistochemistry of human tumour specimens, in vitro cell line experiments (knockdown and overexpression), and an orthotopic mouse xenograft model
• Who was studied: Tumours from 52 Japanese patients with malignant pleural mesothelioma; six human MPM cell lines (MSTO-211H, H226, H2452, YMESO-14, EHMES-1, NCI-H290); SCID mice implanted with selected modified cell lines (H226, MSTO-211H, H290)
• Exposure: Not an exposure study; the variable manipulated was podoplanin (PDPN) expression in tumour cells, by siRNA/shRNA knockdown or gene transfection, plus ROCK inhibitors Y-27632 and fasudil hydrochloride. The authors noted in the introduction that MPM incidence is closely associated with asbestos exposure
• Main results:
  • 47 of 52 (90%) MPM tumours from Japanese patients and 3 of 6 MPM cell lines were PDPN-positive
  • In H226 cells (high PDPN), siRNA knockdown left viability unchanged but reduced motility; shRNA knockdown also inhibited motility
  • In MSTO-211H cells (low PDPN), overexpression of PDPN increased motility in wound healing and transwell migration assays
  • PDPN transfection into MSTO-211H increased RhoA-GTP binding; PDPN knockdown in H226 decreased it; ROCK inhibitors Y-27632 and fasudil inhibited motility of MSTO-211H/PDPN cells dose-dependently without affecting viability
  • After orthotopic implantation of the modified cells into SCID mice, shRNA knockdown of PDPN in H226 cells reduced intrathoracic tumour burden; PDPN transfection into MSTO-211H cells promoted tumour progression and significantly shortened survival (P < 0.001, log-rank)
  • PDPN-transfected MSTO-211H tumours had more Ki-67-positive proliferating cells; PDPN-knockdown H226 tumours had fewer
  • PDPN promoted focus formation in MSTO-211H and H290 cells; knockdown in H226 markedly reduced focus number
  • Nuclear YAP1 was present in 50% or more tumour cells in H226 (high PDPN) tumours and in 60% or more cells in PDPN-transfected MSTO-211H or H290 tumours; PDPN knockdown increased E-cadherin, PDPN transfection decreased it
  • PDPN expression did not change the engraftment rate or number of tumours produced by MPM cells
• The authors' conclusion: The authors concluded that PDPN, besides being a diagnostic marker, promotes MPM progression by stimulating motility through RhoA/ROCK activation and by blocking contact inhibition linked to lower E-cadherin and YAP1 activation, and that it could be a therapeutic target
• Limitations the authors state:
  • The authors stated that the mechanism by which PDPN suppresses E-cadherin expression remains to be analysed
  • The authors noted debate over whether PDPN-driven motility involves epithelial–mesenchymal transition, and reported some observations only as unshown data

Topics

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

Medical terms in this study, explained in our Lexicon: Podoplanin (D2-40), Pleural Mesothelioma, Ki-67.

Related studies

• Podoplanin: An emerging cancer biomarker and therapeutic target — H. Krishnan, J. Rayes, et al. (2018)
• Pleural mesothelioma instigates tumor-associated fibroblasts to promote progression via a malignant cytokine network — Q. Li, W. Wang, et al. (2011)
• Podoplanin overexpression in human mesothelioma cell lines enhances the tumorigenic phenotype — E. Yamaki, T. Yajima, et al. (2013)
• The impact of Aggrus/podoplanin on platelet aggregation and tumour metastasis — N. Fujita, S. Takagi (2012)
• Hippo pathway gene mutations in malignant mesothelioma: revealed by RNA and targeted exon sequencing — A. Miyanaga, M. Masuda, et al. (2015)
• Targeting YAP in malignant pleural mesothelioma — W.Q. Zhang, Y.Y. Dai, et al. (2017)

Browse more research in Cancer Science, or return to medical research.