Restored expression of the MYO18B gene suppresses orthotopic growth and the production of bloody pleural effusion by human malignant pleural mesothelioma cells in SCID mice

Our plain-English summary of Restored expression of the MYO18B gene suppresses orthotopic growth and the production of bloody pleural effusion by human malignant pleural mesothelioma cells in SCID mice, by N. Edakuni, K. Ikuta, S. Yano, et al (Oncology Research, 2006).

The study

• Authors: N. Edakuni, K. Ikuta, S. Yano, E. Nakataki, H. Muguruma, H. Uehara, M. Tani, J. Yokota, H. Aizawa, S. Sone
• Journal: Oncology Research
• Published: 2006;16(5):235-43
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Malignant pleural mesothelioma (MPM) is closely related to exposure to asbestos, and a rapid increase in the number of MPM patients is therefore estimated to occur from 2010 to 2040 in Japan. Because MPM is refractory to conventional chemotherapy and radiotherapy, the prognosis of MPM patients is extremely poor. MYO18B, a novel member of the myosin family, is a tumor suppressor gene isolated from a homozygously deleted region at 22q12.1 in a lung cancer cell line. The inactivation of the MYO18B gene plays an important role in several malignant diseases. However, the role of MYO18B in the progression of MPM is still unknown. Six different human MPM cell lines were used in this study. Western blot revealed that none of the cell lines expressed a detectable level of MYO18B protein. One of the MPM cell lines, EHMES-10, was transfected with the MYO18B gene. We found that a restored expression of the MYO18B protein in EHMES-10 cells resulted in the inhibition of their anchorage-independent growth and motility in vitro. In addition, it also inhibited their ectopic (subcutaneous space) and orthotopic (thoracic cavity) growth in SCID mice, in association with an increased degree of cell apoptosis. Furthermore, it also suppressed the production of bloody pleural effusion after orthotopic injection. These findings suggest that the restored expression of MYO18B may be a useful therapeutic strategy for the treatment of locally advanced MPM in humans.

In plain English

This was a laboratory and animal study from Japan. It did not study people exposed to asbestos, and asbestos appears only as background. The authors tested six human malignant pleural mesothelioma cell lines and found that none had a detectable level of MYO18B protein, the product of a gene that earlier work described as a tumor suppressor. They inserted the MYO18B gene into one line, EHMES-10. The altered cells formed fewer colonies in soft agar and moved less than unaltered cells or cells given an empty vector. Their ordinary growth in dishes did not differ significantly from empty-vector cells, and their VEGF output did not differ significantly from either comparison group. In SCID mice, the altered cells grew more slowly under the skin. When injected into the chest, they produced smaller tumors and no pleural effusion in any mouse. In one experiment the median tumor weight was 10 mg, against 228 mg for unaltered cells. Their tumors held more apoptotic (dying) cells. The authors concluded that restoring MYO18B may be a useful treatment strategy for locally advanced mesothelioma in humans. They noted that the mechanism still needs study.

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 of human mesothelioma cell lines, with animal experiments in SCID mice (cells injected under the skin and into the chest cavity)
• Who was studied: Six human malignant pleural mesothelioma cell lines (EHMES-1, EHMES-10, NCI-H28, NCI-H2052, NCI-H2452, MSTO-211H) and male SCID mice aged 6 to 8 weeks from CLEA Japan, studied at the University of Tokushima. Groups were 5 mice for the subcutaneous experiment and 4 to 5 mice per group for the chest-cavity experiments.
• Exposure: No asbestos exposure was studied. The experimental factor was transfection of the EHMES-10 cell line with the MYO18B gene (FLAG-tagged MYO18B cDNA in a pcDNA3.1(+) vector). Transfected cells were compared with unaltered EHMES-10 cells and with empty-vector (Mock) cells.
• Main results:
  • Western blotting detected no MYO18B protein in any of the six mesothelioma cell lines.
  • MYO18B mRNA was not detected in four clinical samples from mesothelioma patients (data not shown in the article).
  • Anchorage-dependent growth (MTT assay) of MYO18B-transfected cells tended to be slower than that of parental cells, but it did not differ significantly from empty-vector cells.
  • Anchorage-independent growth (colony formation in soft agar) of MYO18B-transfected cells was significantly suppressed compared with parental and empty-vector cells.
  • Motility of MYO18B-transfected cells in the scratch wound assay was significantly suppressed compared with parental and empty-vector cells.
  • VEGF secretion in culture did not differ significantly between MYO18B-transfected cells and parental or vector control cells.
  • Under the skin of SCID mice, all cell types formed palpable tumors. The MYO18B-transfected tumors grew much more slowly (p less than 0.05 compared with Mock cells).
  • Chest-cavity injection, Experiment 1, parental EHMES-10 cells: thoracic tumors in 4/4 mice (median 228 mg, range 30 to 298) and pleural effusion in 3/4 mice (median 725 µl, range 0 to 1000).
  • Chest-cavity injection, Experiment 1, Mock cells: thoracic tumors in 4/4 mice (median 191 mg, range 144 to 270) and pleural effusion in 3/4 mice (median 575 µl, range 0 to 820).
  • Chest-cavity injection, Experiment 1, MYO18B-transfected cells (labelled EHMES-10/MYO18B2 in Table 1): thoracic tumors in 3/5 mice (median 10 mg, range 0 to 43; p less than 0.05) and pleural effusion in 0/5 mice.
  • Chest-cavity injection, Experiment 2: parental cells gave tumors in 5/5 mice (median 88 mg, range 38 to 168) and effusion in 4/5 mice (median 450 µl). MYO18B-transfected cells gave tumors in 5/5 mice (median 18 mg, range 4 to 59; p less than 0.05) and effusion in 0/5 mice.
  • In the chest tumors, vascularization, VEGF production and the number of proliferating cells showed no discernible difference between groups.
  • Tumors from MYO18B-transfected cells had significantly more apoptotic (TUNEL-positive) cells than tumors from parental or Mock cells.
• The authors' conclusion: The authors concluded that restored expression of MYO18B may be a useful therapeutic strategy for the treatment of locally advanced malignant pleural mesothelioma in humans.
• Limitations the authors state:
  • The mechanism by which MYO18B induces apoptosis was not determined and needs further experiments.
  • MYO18B status in normal mesothelial cells could not be examined because a pure human mesothelial cell line was not commercially available.
  • The mechanisms of MYO18B gene silencing in mesothelioma remain unclear and need further study.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Effusion, Pleural Mesothelioma, Chemotherapy, Prognosis, Tumor Suppressor Gene, Lung Cancer, Apoptosis.

Related studies

• Novel orthotopic implantation model of human malignant pleural mesothelioma (EHMES-10 cells) highly expressing vascular endothelial growth factor and its receptor — E. Nakataki, S. Yano, et al. (2006)
• HMGB1 targeting by ethyl pyruvate suppresses malignant phenotype of human mesothelioma — L. Pellegrini, J. Xue, et al. (2017)
• Expression of the Wilms' tumor gene WT1 in human malignant mesothelioma cell lines and relationship to platelet-derived growth factor A and insulin-like growth factor 2 expression — A.W. Langerak, K.A. Williamson, et al. (1995)
• Inflammation precedes the development of human malignant mesotheliomas in a SCID mouse xenograft model — J.M. Hillegass, A. Shukla, et al. (2010)
• ZDHHC8 knockdown enhances radiosensitivity and suppresses tumor growth in a mesothelioma mouse model — H. Sudo, A.B. Tsuji, et al. (2012)
• SU6668, a multiple tyrosine kinase inhibitor, inhibits progression of human malignant pleural mesothelioma in an orthotopic model — T.T. Van, M. Hanibuchi, et al. (2012)

Browse more research in Oncology Research, or return to medical research.