Podoplanin overexpression in human mesothelioma cell lines enhances the tumorigenic phenotype

Our plain-English summary of Podoplanin overexpression in human mesothelioma cell lines enhances the tumorigenic phenotype, by E. Yamaki, T. Yajima, T. Kosaka, et al (Oncology Reports, 2013).

The study

• Authors: E. Yamaki, T. Yajima, T. Kosaka, A. Mogi, S. Tanaka, H. Kuwano
• Journal: Oncology Reports
• Published: 2013;29(3):932-40
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Podoplanin, a small type I integral membrane mucin-type sialoglycoprotein, serves as a useful marker for diagnosing malignant pleural mesothelioma (MPM); however, the physiological function of podoplanin in mesothelioma cells is not known. To elucidate the role of podoplanin in the pathogenesis of MPM, we generated two mesothelioma cell lines (PODO1 and PODO2) that stably express high levels of podoplanin. Although PODO1 cells proliferated to the same extent in culture or in nude mice, the survival rate of the mice was significantly reduced compared with that of the controls. We demonstrated that PODO1 and PODO2 cells had increased invasive ability in in vitro assays and induced upregulation of matrix metalloproteinase-1. PODO1 and PODO2 cultures could not be induced to undergo apoptosis when starved or treated with cis-diamminedichloroplatinum(II) (CDDP) compared with the controls. Moreover, silencing of podoplanin expression using RNA interference restored the ability of CDDP to induce apoptosis. Consistent with their growth properties, we detected constitutive activation of extracellular signal-regulated kinase in PODO1 and PODO2 cultures. These findings suggest that constitutive expression of podoplanin contributes to the invasive growth properties of mesothelioma cells and their resistance to apoptosis. Moreover, our data suggest that podoplanin or components of its signaling pathway, or both, may serve as important targets for developing novel treatments for MPM.

In plain English

This laboratory study examined what podoplanin, a protein found on malignant pleural mesothelioma (MPM) cells, does in those cells. It did not study asbestos exposure. The authors added the podoplanin gene to a human mesothelioma cell line (MSTO-211H) to make two high-podoplanin lines, PODO1 and PODO2. They compared these with empty-vector control cells (p3x). Nude mice injected with PODO1 cells had significantly lower survival than mice injected with p3x cells, although tumor growth did not differ significantly and no spread to other organs was seen. In the dish, the podoplanin cells moved and invaded more and had higher messenger RNA levels for MMP-1, an enzyme linked to invasion. After 48 and 96 hours they grew more (p less than 0.001). They also resisted cell death from serum starvation and the drug cisplatin (CDDP). In a second cell line with natural podoplanin (NCI-H226), lowering podoplanin slightly but significantly increased cell death after cisplatin. The authors concluded that podoplanin may be a target for developing more effective MPM treatments. Mouse numbers are not stated, and survival is shown only in a graph.

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 experiment using human mesothelioma cell lines in culture and a nude mouse model (animal experiment)
• Who was studied: Two human mesothelioma cell lines, MSTO-211H and NCI-H226, from the American Type Culture Collection. MSTO-211H was used to make podoplanin-overexpressing clones PODO1 and PODO2, and NCI-H226 was used for gene silencing. Female BALB/c-nu/nu nude mice aged 6 weeks were also used; the number of mice is not stated.
• Exposure: No asbestos exposure was studied. The experimental factors were forced overexpression of podoplanin (compared with empty-vector p3x cells), silencing of podoplanin with siRNA, serum starvation, and the chemotherapy drug CDDP (cisplatin) at 5 µM (IC50) and 25 µM for 48 hours.
• Main results:
  • Podoplanin expression was significantly higher in PODO1 and PODO2 than in p3x cells. Platelet aggregation occurred only with the podoplanin-expressing cells.
  • Survival of nude mice injected with PODO1 cells was significantly lower than survival of mice injected with p3x cells. The results are shown in a Kaplan-Meier figure (Fig. 2B). The text prints no survival numbers or p-value.
  • In the mice, tumor growth from PODO1 cells did not differ significantly from tumor growth from p3x cells.
  • No metastases to other organs, including the lung, were seen in the mice.
  • PODO1 and PODO2 cells migrated more than p3x cells (p less than 0.05).
  • PODO1 and PODO2 cells invaded a Matrigel layer significantly more than p3x cells.
  • MMP-1 mRNA was increased in PODO1 and PODO2 compared with p3x cells, as measured by RT-PCR. MMP-2, MMP-7 and MMP-9 mRNA were not increased, and PDGF-BB and PDGFR-β mRNA did not differ.
  • In culture, proliferation did not differ significantly at 24 hours. At 48 and 96 hours, proliferation of the podoplanin cells was significantly greater than that of p3x cells (p less than 0.001).
  • After 96 hours of culture under serum starvation, p3x cultures had twice as many apoptotic (dying) cells as PODO1 cultures.
  • 48 hours after CDDP (cisplatin) treatment, PODO1 cultures had fewer apoptotic cells than p3x cultures. This was confirmed by measuring active caspase.
  • ERK phosphorylation (activation) was markedly higher in PODO1 and PODO2 than in p3x cells. Phosphorylation of JNK, p38 and AKT did not differ.
  • In NCI-H226 cells, which naturally express high podoplanin, siRNA silencing of podoplanin followed by CDDP treatment slightly but significantly increased the proportion of apoptotic cells compared with control.
• The authors' conclusion: The authors concluded that podoplanin overexpression had anti-apoptotic effects and increased tumor malignancy in vitro and in vivo, and that podoplanin may serve as a target for developing more effective treatments for MPM.

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), Mesothelioma, Pleural Mesothelioma, Apoptosis.

Related studies

• Antitumor activity of chLpMab-2, a human-mouse chimeric cancer-specific antihuman podoplanin antibody, via antibody-dependent cellular cytotoxicity — M.K. Kaneko, S. Yamada, et al. (2017)
• Establishment of Mouse Monoclonal Antibody LpMab-13 Against Human Podoplanin — S. Ogasawara, M.K. Kaneko, et al. (2016)
• Podoplanin: An emerging cancer biomarker and therapeutic target — H. Krishnan, J. Rayes, et al. (2018)
• Therapeutic efficacy evaluation of radioimmunotherapy with 90 Y-labeled anti-podoplanin antibody NZ-12 for mesothelioma — H. Sudo, A.B. Tsuji, et al. (2019)
• Antitumor effect of novel anti-podoplanin antibody NZ-12 against malignant pleural mesothelioma in an orthotopic xenograft model — S. Abe, M.K. Kaneko, et al. (2016)
• Podoplanin promotes progression of malignant pleural mesothelioma by regulating motility and focus formation — S. Takeuchi, K. Fukuda, et al. (2017)

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