MET Gene Status in Malignant Mesothelioma Using Fluorescent In Situ Hybridization

Our plain-English summary of MET Gene Status in Malignant Mesothelioma Using Fluorescent In Situ Hybridization, by S. Varesano, S. Salvi, S. Boccardo, et al (Journal of Thoracic Oncology, 2016).

The study

• Authors: S. Varesano, S. Salvi, S. Boccardo, J.L. Ravetti, M.P. Pistillo, P.A. Canessa, P. Ferro, F. Fedeli, S. Roncella
• Journal: Journal of Thoracic Oncology
• Published: 2016;11(2):e28-30
• Type of article: Letter, Comment
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Summary of the article

The authors followed up their earlier report of a patient with malignant mesothelioma (MM) whose tumor showed MET gene amplification with MET receptor expression, and examined how often MET copy number changes occur in MM. Tumor tissue from 60 patients was analyzed (66.7% male; median age 60.0 years, range 5–85 years). There were 36 epithelioid, 12 sarcomatoid, 8 biphasic, 2 desmoplastic and 2 papillary cases. Thirty cases came from a commercial tissue microarray, 12 from IRCCS A.O.U. San Martino–IST in Genova, Italy, and 18 from ASL5 in La Spezia, Italy. MET and chromosome 7 centromere (CEP7) copy numbers were measured by fluorescence in situ hybridization (FISH) and scored with criteria proposed for non-small cell lung cancer. MET protein was assessed by immunohistochemistry. Five cases (8.3%), all epithelioid, were FISH-positive. One had MET amplification (MET/CEP7 ratio 4.0) with moderate MET protein expression. Four showed high MET polysomy with low protein staining. The other 55 cases (91.7%) were disomic for MET. The authors concluded that MET amplification was rare in MM (1.7% of cases) and that polysomy was more frequent (6.7%). They suggested these findings reinforce new treatment possibilities, but stated that whether patients with MM could benefit from MET-targeted therapies remains to be established in clinical trials.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This letter to the editor reported a laboratory analysis of tumor tissue from 60 patients with malignant mesothelioma. The authors used fluorescence in situ hybridization (FISH) to count copies of the MET gene in tumor cells, and immunohistochemistry to look at MET protein. Thirty cases came from a commercial tissue microarray and 30 from two pathology units in Genova and La Spezia, Italy. Five of the 60 cases (8.3%) were FISH-positive, all of the epithelioid subtype. One case had MET amplification (1.7% of all cases), and four had high polysomy of MET, meaning extra copies of the gene (6.7% of all cases). The other 55 cases (91.7%) were FISH-negative. The amplified case showed moderate MET protein expression, and the high-polysomy case shown in the figure had low staining. The authors wrote that the biological impact of MET polysomy is not well established. They concluded that whether patients with mesothelioma could benefit from MET-targeted drugs remains to be established in clinical trials. Asbestos exposure was not reported.

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: Letter to the editor reporting a laboratory analysis of tumor tissue samples (gene copy number by FISH, protein by immunohistochemistry)
• Who was studied: 60 patients with malignant mesothelioma (66.7% male; median age 60.0 years, range 5 to 85 years as printed). Subtypes: 36 epithelioid, 12 sarcomatoid, 8 biphasic, 2 desmoplastic and 2 papillary. Thirty cases came from a commercial tissue microarray (US Biomax), 12 from the Unit of Pathology, IRCCS A.O.U. San Martino–IST (Genova, Italy), and 18 from the Division of Histopathology, ASL5 (La Spezia, Italy). Tumor site (pleural or peritoneal) and dates were not stated.
• Exposure: Asbestos exposure was not reported. The study measured MET gene status (amplified, polysomic or disomic) by FISH and MET protein expression by immunohistochemistry.
• Main results:
  • 5 of 60 cases (8.3%) were FISH-positive. The other 55 cases (91.7%) were FISH-negative and disomic for MET.
  • One epithelioid case had MET amplification (about 8 MET signals on more than 70% of cells; MET/CEP7 ratio 4.0). Four epithelioid cases showed high polysomy of MET.
  • MET amplification occurred in 1.7% of all cases and MET polysomy in 6.7% of all cases.
  • The amplified case showed moderate MET protein expression in the cytoplasm and membrane of tumor cells, while high gene polysomy resulted in low staining of MET protein.
• The authors' conclusion: The authors wrote that MET amplification and polysomy with MET receptor overexpression reinforce new possibilities of treatment, but that whether patients with mesothelioma could benefit from MET-targeted therapies remains to be established in clinical trials.
• Limitations the authors state:
  • The authors stated that the biological impact of MET polysomy on cancer cells has not been well established.

Topics

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

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Epithelioid, Sarcomatoid, Biphasic Mesothelioma, Desmoplastic Mesothelioma, Fluorescence In Situ Hybridization (FISH), Non-Small Cell Lung Cancer, Immunohistochemistry.

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