Characterization of human malignant mesothelioma cell lines orthotopically implanted in the pleural cavity of immunodeficient mice for their ability to grow and form metastasis

Our plain-English summary of Characterization of human malignant mesothelioma cell lines orthotopically implanted in the pleural cavity of immunodeficient mice for their ability to grow and form metastasis, by D. Martarelli, A. Catalano, A. Procopio, et al (BMC Cancer, 2006).

The study

• Authors: D. Martarelli, A. Catalano, A. Procopio, S. Orecchia, R. Libener, G. Santoni
• Journal: BMC Cancer
• Published: 2006;6:130
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Malignant pleural mesothelioma (MPM) is a tumor known to be resistant to conventional therapies. Thus, an in vivo model can represent an important tool for assessing the efficacy of novel approaches in the treatment of MPM.Presently, human MPM cells have been grown orthotopically in mice upon transplantation of tumor masses or tumor cell suspensions following surgery. In these models however, surgery can interfere with the tumor growth and the early stages of tumor development cannot be easily explored. Finally, results may not be so accurate due to implantation of potentially different tumor samples in different experimental groups.Our work aimed at establishing a nude mouse model xenotransplanted with human MPM cell lines in which tumor progression exhibits some features of the human disease.

Methods: Three distinct human MPM cell lines previously established from MPM patients displaying two different phenotypes, biphasic (MM-B1 and IST-Mes3) and epithelioid (IST-Mes2), were directly injected into the pleural cavity of nude mice. At different times, mice were sacrificed for autopsy, tumor nodules were counted and then removed for histology. Presence of metastases in visceral organs was also monitored.

Results: IST-Mes2 cells were unable to grow in nude mice. MM-B1 and IST-Mes3 cells were capable of growing in nude mice and formed tumor nodules in the pleura. Post-mortem examination showed that MPM cells progressively colonized the parietal and visceral pleura, the diaphragm, the mediastinum and, lastly the lung parenchyma. No pneumo-thorax was evidenced in the mice. Pleural effusions as well as lymph node metastases were observed only at later times.

Conclusion: This model mimics the progression of human malignant mesothelioma and it is easy to perform and reproducible; therefore it can be useful to study human MPM biology and evaluate the efficacy of novel therapies.

In plain English

This animal experiment tested whether human malignant pleural mesothelioma (MPM) cell lines would grow after direct injection into the pleural cavity of nude mice, without surgery. Three cell lines previously established from MPM patients were used: the biphasic MM-B1 and IST-Mes3 and the epithelioid IST-Mes2, plus IST-Mes3/2P, a line re-established from an IST-Mes3 tumour grown in mice. Two million cells were injected into the left pleural cavity or subcutaneously in 6-week-old athymic male nude mice, and one subcutaneous IST-Mes3 group received four million cells. IST-Mes2 cells did not grow by either route (0/15 orthotopic, 0/15 subcutaneous). IST-Mes3, IST-Mes3/2P and MM-B1 each gave tumours in 15/15 mice after intrapleural injection; mean survival was 81.5 plus or minus 21.7 days (IST-Mes3), 69.6 plus or minus 14.5 days (IST-Mes3/2P) and 72.5 plus or minus 6.4 days (MM-B1). Tumour colonised parietal and visceral pleura, diaphragm and mediastinum, invading lung parenchyma later; pleural effusions and lymph node metastases appeared only at later stages, and no visceral organ metastases were formed. The authors concluded the model mimics human MPM progression and is simple and reproducible.

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: animal experiment (orthotopic and subcutaneous xenograft study in nude mice)
• Who was studied: Athymic male nude mice (nu/nu, 6 weeks old, Harlan, Italy) injected with three human malignant pleural mesothelioma cell lines previously established from patients (MM-B1, IST-Mes3, IST-Mes2) plus a derived line IST-Mes3/2P; 15 mice per cell line and route
• Exposure: Injection of 2 x 10^6 human MPM cells in 100 microlitres of HBSS into the left pleural cavity (orthotopic) or subcutaneously on the left lateral chest wall, with a subcutaneous IST-Mes3 group also given 4 x 10^6 cells; biphasic (MM-B1, IST-Mes3) and epithelioid (IST-Mes2) phenotypes
• Main results:
  • IST-Mes2 (epithelioid) formed no tumours: 0/15 by orthotopic and 0/15 by subcutaneous implantation
  • IST-Mes3 and MM-B1 cells injected intrapleurally gave a 100% take rate
  • Mean survival after intrapleural injection: 72.5 plus or minus 6.4 days for MM-B1, 81.5 plus or minus 21.7 days for IST-Mes3, 69.6 plus or minus 14.5 days for IST-Mes3/2P
  • Tumour spread in mice given intrapleural cells: parietal and visceral pleura, diaphragm and mediastinum, with lung parenchyma invasion at later times
  • No pneumothorax occurred; pleural effusions and lymph node metastasis were seen only in later stages of orthotopic growth of MM-B1, IST-Mes3 and IST-Mes3/2P cells
  • Subcutaneously, MM-B1 and IST-Mes2 cells did not grow; IST-Mes3 started growing only 40 days after injection, and the lag did not depend on the number of cells injected (2 x 10^6 or 4 x 10^6)
  • Tumours from IST-Mes3 and MM-B1 in mice were positive for calretinin, cytokeratin 8/18, EMA (membrane), HBME-1 and podoplanin and negative for CEA, CD15 (LeuM1) and Ber-EP4; CD31 staining showed high microvessel density
• The authors' conclusion: The authors proposed the intrapleural injection model as a useful tool for in vivo MPM studies because it resembles the human disease, is simple to perform and reproducible
• Limitations the authors state:
  • None of the cell lines formed metastases in visceral organs, which the authors attributed to the short time before the mice died of rapid intrapleural spread
  • The epithelioid line IST-Mes2 did not grow, although epithelioid is the most common mesothelioma subtype, so a model with other epithelioid cells remains to be set up
  • Tumour latency with IST-Mes3 varied from animal to animal, and the authors noted a noninvasive imaging method would be needed to follow tumour development

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Pleural Cavity, Metastasis, Pleural Mesothelioma, Biphasic Mesothelioma, Epithelioid, Autopsy, Histology.

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