Suppression of cell death by the secretory form of N-terminal ERC/mesothelin

Our plain-English summary of Suppression of cell death by the secretory form of N-terminal ERC/mesothelin, by T. Wang, K. Kajino, M. Abe, et al (International Journal of Molecular Medicine, 2010).

The study

• Authors: T. Wang, K. Kajino, M. Abe, K. Tan, M. Maruo, G. Sun, Y. Hagiwara, M. Maeda, O. Hino
• Journal: International Journal of Molecular Medicine
• Published: 2010;26(2):185-91
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

ERC/mesothelin is highly expressed in malignant mesothelioma, pancreatic cancer, and ovarian cancer. It is cleaved to a 30 kDa N-terminal secretory form (N-ERC) and a 40 kDa C-terminal membranous form (C-ERC). Several functions have been reported for full-length ERC (full-ERC) and C-ERC/mesothelin, such as in cell adhesion and invasion, stimulation of cell proliferation, and the suppression of cell death. However, there have been no studies to date on the function of secretory N-ERC, despite the fact that it is abundantly secreted into the sera of mesothelioma patients. In this study, we investigated whether N-ERC could function as a secretory factor to stimulate tumor progression. Full-, N, or C-ERC was overexpressed in the human hepatocellular carcinoma cell line Huh7 that lacks endogenous expression of ERC/mesothelin. Changes in the rates of cell proliferation and cell death were determined, and the state of signal transducers was examined using various endpoints: total cell counts, trypan blue exclusion rate, BrdU incorporation rate, TUNEL assay, and the phosphorylation of ERK1/2 and Stat3. In cells overexpressing N-ERC, phosphorylation of ERK1/2 was enhanced and the rate of cell death decreased, leading to the increase of cell number. The culture medium containing the secretory N-ERC also had the activity to increase the number of cells. Our data suggested that one of the full-ERC functions reported previously was mediated by the secretory N-ERC.

In plain English

This laboratory study used cultured cells, not people, and did not study asbestos. ERC/mesothelin, highly expressed in malignant mesothelioma, splits into a secreted piece (N-ERC) and a membrane-bound piece (C-ERC). The authors made Huh7 liver cancer cells, which lack the protein, produce full-length ERC, N-ERC or C-ERC. Cells were grown in low serum, on non-attaching plates for counts and viability or in glass-bottom dishes for staining. At 72 hours, cells making full-length ERC or N-ERC were significantly more numerous and more often alive than empty-vector or C-ERC cells. They also had fewer dying cells than empty-vector cells and more cells with activated ERK1/2, a signaling protein. C-ERC's effects were not statistically significant. Medium from N-ERC cells raised numbers of untreated cells on non-attaching plates at 72 hours, but not when cells could attach. The authors interpreted the growth increase as mainly due to less cell death. They wrote that their data suggested secreted N-ERC mediated a previously reported function of full-length mesothelin. They noted the cell-death pathway was unclear and other medium factors might explain its effect.

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) cell culture experiment using plasmid transfection to overexpress forms of ERC/mesothelin, with conditioned-medium experiments
• Who was studied: Cultured Huh7 human hepatic (liver) cancer cells, which do not normally express ERC/mesothelin; no human subjects or mesothelioma cells; most measurements reported with n=6
• Exposure: No asbestos or fiber exposure was studied. Cells were transfected with vectors expressing full-length ERC/mesothelin (70 kDa), the N-terminal secreted form N-ERC (30 kDa), or the C-terminal membrane form C-ERC (40 kDa), compared with an empty (mock) vector. All cultures used low serum (2%). Cell counts and trypan blue viability used low adhesion (anchorage-independent) plates; BrdU, TUNEL and phospho-ERK1/2 staining used glass bottom dishes. Untreated cells were also given culture medium from N-ERC- or mock-transfected cells.
• Main results:
  • At 72 h, cells transfected with full-ERC or N-ERC had significantly larger cell numbers (p<0.01) than mock- or C-ERC-transfected cells
  • Full-, N- and C-ERC all increased BrdU incorporation (a marker of dividing cells) compared with mock, but the increase was statistically significant only for full-ERC (p=0.0027) and N-ERC (p=0.0023)
  • At 72 h, full-ERC and N-ERC transfected cells showed significantly higher viability by trypan blue exclusion (p<0.01) than mock or C-ERC cells
  • In the TUNEL assay, full-ERC and N-ERC reduced cell death rates compared with mock (p values printed as 5.43E-10 and 5.22E-11, respectively)
  • Rates of phospho-ERK1/2-positive cells were significantly higher (p<0.01) in full-ERC and N-ERC cultures than in mock or C-ERC cultures; no change was detected in Stat3 phosphorylation or cyclin E expression (data not shown)
  • Untreated Huh7 cells cultured on low adhesion plates in medium from N-ERC-transfected cells had significantly more cells at 72 h (p<0.01) than cells in mock medium; the effect of the medium was observed only in the anchorage-independent condition, not in the anchorage-dependent condition (data not shown)
  • C-ERC showed some effect on BrdU incorporation and cell death, but these effects were not statistically significant
  • The authors interpreted the apparent growth stimulation by full-ERC or N-ERC as resulting mainly from suppression of cell death
• The authors' conclusion: The authors wrote that their data suggested one previously reported function of full-length ERC/mesothelin was mediated by secretory N-ERC
• Limitations the authors state:
  • The molecular pathway by which N-ERC suppressed cell death was not clarified, and Bim and Bcl-2 measurements did not show consistent changes
  • The conditioned-medium effect might have come from other cytokines induced by overexpressed N-ERC rather than from N-ERC itself; purified N-ERC would need to be tested
  • The reason why secreted and transfected N-ERC behaved differently under anchorage-dependent conditions was unclear
  • The authors could not exclude that C-ERC also stimulates cell growth

Topics

Medical terms in this study, explained in our Lexicon: Mesothelin, Malignant Mesothelioma, Ovarian Cancer, Mesothelioma, Carcinoma.

Related studies

• Mesothelin (MSLN) promoter is hypomethylated in malignant mesothelioma, but its expression is not associated with methylation status of the promoter — K. Tan, K. Kajino, et al. (2010)
• Antitumor activity of anti-C-ERC/mesothelin monoclonal antibody in vivo — K. Inami, M. Abe, et al. (2010)
• Sensitive and specific new enzyme-linked immunosorbent assay for N-ERC/mesothelin increases its potential as a useful serum tumor marker for mesothelioma — K. Shiomi, Y. Hagiwara, et al. (2008)
• Establishment of a novel specific ELISA system for rat N- and C-ERC/mesothelin. Rat ERC/mesothelin in the body fluids of mice bearing mesothelioma — Y. Hagiwara, Y. Hamada, et al. (2008)
• Combined treatment with cisplatin and sirolimus to enhance cell death in human mesothelioma — M.L. Hartman, J.M. Esposito, et al. (2010)
• Soluble mesothelin-related peptides in the diagnosis of malignant pleural mesothelioma — A. Scherpereel, B. Grigoriu, et al. (2006)

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