Mesothelioma patient derived tumor xenografts with defined BAP1 mutations that mimic the molecular characteristics of human malignant mesothelioma

Our plain-English summary of Mesothelioma patient derived tumor xenografts with defined BAP1 mutations that mimic the molecular characteristics of human malignant mesothelioma, by N. Kalra, J. Zhang, A. Thomas, et al (BMC Cancer, 2015).

The study

• Authors: N. Kalra, J. Zhang, A. Thomas, L. Xi, M. Cheung, J. Talarchek, S. Burkett, M.G. Tsokos, Y. Chen, M. Raffeld, M. Miettinen, I. Pastan, J.R. Testa, R. Hassan
• Journal: BMC Cancer
• Published: 2015;15:376
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: The development and evaluation of new therapeutic approaches for malignant mesothelioma has been sparse due, in part, to lack of suitable tumor models.

Methods: We established primary mesothelioma cultures from pleural and ascitic fluids of five patients with advanced mesothelioma. Electron microscopy and immunohistochemistry (IHC) confirmed their mesothelial origin. Patient derived xenografts were generated by injecting the cells in nude or SCID mice, and malignant potential of the cells was analyzed by soft agar colony assay. Molecular profiles of the primary patient tumors, early passage cell cultures, and patient derived xenografts were assessed using mutational analysis, fluorescence in situ hybridization (FISH) analysis and IHC.

Results: Primary cultures from all five tumors exhibited morphologic and IHC features consistent to those of mesothelioma cells. Mutations of BAP1 and CDKN2A were each detected in four tumors. BAP1 mutation was associated with the lack of expression of BAP1 protein. Three cell cultures, all of which were derived from BAP1 mutant primary tumors, exhibited anchorage independent growth and also formed tumors in mice, suggesting that BAP1 loss may enhance tumor growth in vivo. Both early passage cell cultures and mouse xenograft tumors harbored BAP1 mutations and CDKN2A deletions identical to those found in the corresponding primary patient tumors.

Conclusions: The mesothelioma patient derived tumor xenografts with mutational alterations that mimic those observed in patient tumors which we established can be used for preclinical development of novel drug regimens and for studying the functional aspects of BAP1 biology in mesothelioma.

In plain English

This laboratory study established five primary malignant mesothelioma cell cultures from the ascitic or pleural fluid of five patients enrolled at the National Cancer Institute, and tumor xenografts made by injecting those cells into nude or SCID mice. Four patients had pleural tumors and one peritoneal; four tumors were epithelioid and one predominantly epithelioid with focal sarcomatous features. Electron microscopy and immunohistochemistry supported mesothelial origin, and spectral karyotyping showed abnormal karyotypes in all five cultures. BAP1 mutations were found in 4 of 5 cultures, which lacked BAP1 protein by immunohistochemistry, though one early-passage mutant culture showed a faint band on western blot. CDKN2A deletions were found in four cultures; the text calls all four homozygous, but the tables list one as heterozygous. One culture also had an NF2 deletion and a TP53 mutation. Three cultures (NCI-Meso16, NCI-Meso17, NCI-Meso21), all BAP1-mutant, grew colonies in soft agar and formed tumors in mice. Xenografts matched their cultures, and the patient tumors where samples existed, for BAP1 mutations and CDKN2A deletion status, with one CDKN2A exception. Asbestos was mentioned only as background.

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: establishment and molecular characterization of primary mesothelioma cell cultures and patient-derived mouse tumor xenografts
• Who was studied: Five patients with advanced malignant mesothelioma (four pleural, one peritoneal) enrolled in IRB-approved protocols at the Center for Cancer Research, National Cancer Institute. One patient (NCI-Meso19) died before any specific treatment. Cells derived from the patients were also injected into nude or SCID mice.
• Exposure: No patient asbestos exposure was assessed; asbestos was mentioned only as background. The study examined genetic alterations, chiefly BAP1 mutation and CDKN2A deletion
• Main results:
  • BAP1 mutations were found in 4 of 5 early passage cell cultures: a splice site mutation in intron 4 (NCI-Meso16), frame shift mutations at the intron15/exon16 junction (NCI-Meso17) and in exon 13 (NCI-Meso21), and a large deletion (NCI-Meso18)
  • By immunohistochemistry, BAP1 mutation corresponded to absence of BAP1 protein; only the BAP1 wild-type culture (NCI-Meso19) expressed the protein
  • On western blot, the BAP1-mutant NCI-Meso17 culture showed a faint BAP1 band in early passages that was not detected in late passage cells
  • The text reports homozygous CDKN2A deletions by FISH in four of the five samples, with more than 60% of nuclei showing a homozygous deletion pattern in four cultures and less than 10% in one
  • Table 3, however, lists NCI-Meso21 as having a heterozygous CDKN2A deletion (Table 2 marks it 'Hz')
  • Three of five cultures (NCI-Meso16, NCI-Meso17, NCI-Meso21), all BAP1-mutant, formed soft agar colonies within 3 weeks and tumors in mice within 3-8 weeks, reaching 100 mm3 between 40 and 80 days after inoculation
  • One culture (NCI-Meso19, BAP1 wild type, from a 19-year-old patient) carried a large NF2 deletion and a TP53 missense mutation (P322S)
  • Xenograft tumors showed the same immunohistochemical marker pattern, lack of BAP1 expression and BAP1 mutations as the primary cells. CDKN2A deletion status matched the cultures except in one case.
  • The original patient tumor sample was not available for NCI-Meso21 (or for NCI-Meso18, which did not form tumors), so comparison with the patient tumor was possible for only two of the three tumor-forming lines
• The authors' conclusion: The authors concluded that the primary cultures and patient-derived xenografts reproduced the phenotypic and genetic features of the original tumors and should be useful for preclinical drug studies and for functional studies of BAP1 biology in mesothelioma

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, BAP1, Immunohistochemistry, Fluorescence In Situ Hybridization (FISH), CDKN2A.

Related studies

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• An asbestos-exposed family with multiple cases of pleural malignant mesothelioma without inheritance of a predisposing BAP1 mutation — M. Cheung, Y. Kadariya, et al. (2015)
• BAP1 Is Altered by Copy Number Loss, Mutation, and/or Loss of Protein Expression in More Than 70% of Malignant Peritoneal Mesotheliomas — N. Leblay, F. Leprêtre, et al. (2017)
• Comparison of Germline versus Somatic BAP1 Mutations for Risk of Metastasis in Uveal Melanoma — K.G. Ewens, E. Lalonde, et al. (2018)
• Sarcomatoid Mesothelioma: A CDKN2A molecular analysis of 53 cases with immunohistochemical correlation with BAP1 — M. Zaleski, N. Kalhor, et al. (2020)
• Fluorescence in situ hybridization (FISH) provides estimates of minute and interstitial BAP1, CDKN2A, and NF2 gene deletions in peritoneal mesothelioma — S. Brich, F. Bozzi, et al. (2020)

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