Tumor suppressor alterations cooperate to drive aggressive mesotheliomas with enriched cancer stem cells via a p53-miR-34a-c-Met axis

Our plain-English summary of Tumor suppressor alterations cooperate to drive aggressive mesotheliomas with enriched cancer stem cells via a p53-miR-34a-c-Met axis, by C.W. Menges, Y. Kadariya, D. Altomare, et al (Cancer Research, 2014).

The study

• Authors: C.W. Menges, Y. Kadariya, D. Altomare, J. Talarchek, E. Neumann-Domer, Y. Wu, G.H. Xiao, I.M. Shapiro, V.N. Kolev, J.A. Pachter, A.J. Klein-Szanto, J.R. Testa
• Journal: Cancer Research
• Published: 2014;74(4):1261-1271
• Cited by: 50 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant mesothelioma is a highly aggressive, asbestos-related cancer frequently marked by mutations of both NF2 and CDKN2A. We demonstrate that germline knockout of one allele of each of these genes causes accelerated onset and progression of asbestos-induced malignant mesothelioma compared with asbestos-exposed Nf2(+/-) or wild-type mice. Ascites from some Nf2(+/-);Cdkn2a(+/-) mice exhibited large tumor spheroids, and tail vein injections of malignant mesothelioma cells established from these mice, but not from Nf2(+/-) or wild-type mice, produced numerous tumors in the lung, suggesting increased metastatic potential of tumor cells from Nf2(+/-);Cdkn2a(+/-) mice. Intraperitoneal injections of malignant mesothelioma cells derived from Nf2(+/-);Cdkn2a(+/-) mice into severe combined immunodeficient mice produced tumors that penetrated the diaphragm and pleural cavity and harbored increased cancer stem cells (CSC). Malignant mesothelioma cells from Nf2(+/-);Cdkn2a(+/-) mice stained positively for CSC markers and formed CSC spheroids in vitro more efficiently than counterparts from wild-type mice. Moreover, tumor cells from Nf2(+/-);Cdkn2a(+/-) mice showed elevated c-Met expression/activation, which was partly dependent on p53-mediated regulation of miR-34a and required for tumor migration/invasiveness and maintenance of the CSC population. Collectively, these studies demonstrate in vivo that inactivation of Nf2 and Cdkn2a cooperate to drive the development of highly aggressive malignant mesotheliomas characterized by enhanced tumor spreading capability and the presence of a CSC population associated with p53/miR-34a-dependent activation of c-Met. These findings suggest that cooperativity between losses of Nf2 and Cdkn2a plays a fundamental role in driving the highly aggressive tumorigenic phenotype considered to be a hallmark of malignant mesothelioma.

©2013 AACR.

In plain English

In this mouse experiment, the authors compared mice lacking one copy of each of two tumor suppressor genes, Nf2 and Cdkn2a, with mice lacking one Nf2 copy and with normal (wild-type) mice. Starting at 6 to 8 weeks of age, all received crocidolite asbestos injected into the abdomen every 3 weeks over 24 weeks, 3.2 mg per mouse in total. The doubly altered mice developed malignant mesothelioma sooner (median 24 weeks) than Nf2-altered mice (38 weeks) or wild-type mice (45 weeks). Tumor clumps (spheroids) appeared in abdominal fluid of 22% of doubly altered, 4% of Nf2-altered and 0% of wild-type mice. Injected into the veins of immune-deficient mice, tumor cells from doubly altered mice produced multiple lung tumors in all 9 recipients. Nf2-altered cells gave tumors, which the authors called embolisms, in 3 of 9, and wild-type cells in 0 of 9. These cells also showed more cancer stem cell features and more of a protein, c-Met, which lab tests linked to p53 and miR-34a. The authors concluded that losing both genes cooperates to drive aggressive mesothelioma.

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 (genetically engineered mouse model of asbestos-induced malignant mesothelioma), with transplantation of tumor cells into immune-deficient mice and laboratory cell-culture experiments
• Who was studied: Mice carrying one inactivated copy of both Nf2 and Cdkn2a, compared with mice carrying one inactivated copy of Nf2 only and with wild-type littermates. All were in an FVB genetic background and were 6 to 8 weeks old at the start, at Fox Chase Cancer Center, Philadelphia. The text does not state the number of mice per group. Tumor cell lines were also injected into severe combined immunodeficient (SCID) mice.
• Exposure: Crocidolite asbestos (UICC) injected into the abdominal (peritoneal) cavity every 3 weeks over a 24-week period, totaling 3.2 mg per mouse. The per-injection dose is printed as "400 mg". Given the 3.2 mg total, this appears to be 400 micrograms with the micro symbol lost.
• Main results:
  • Mice with both genes altered developed malignant mesothelioma at a median of 24 weeks, compared with 38 weeks for Nf2-altered mice and 45 weeks for wild-type mice.
  • Tumor spheroids in ascites (abdominal fluid) were found in 22% of doubly altered mice, 4% of Nf2-altered mice and 0% of wild-type mice.
  • SCID mice received tail-vein injections (3 cell lines per genotype, each injected into 3 mice). Cells from doubly altered mice produced multiple lung tumors in 9 of 9 recipients. Cells from Nf2-altered mice gave tumors in 3 of 9 recipients, which the authors labeled embolisms. Cells from wild-type mice gave tumors in 0 of 9.
  • When injected into the abdomen of SCID mice, cells from both doubly altered and wild-type mice formed tumors. Only tumors from doubly altered mice migrated through the diaphragm and invaded the lungs.
  • Cells from doubly altered mice formed much larger cancer-stem-cell-type spheroids than cells from wild-type mice and stained more intensely for the stem cell marker CD24. Treatment with the chemotherapy drug pemetrexed significantly increased the percentage of aldefluor-positive (stem-like) cells among cells from doubly altered mice.
  • Microarray analysis found 929 genes expressed differently in cells from doubly altered mice than in cells from wild-type mice. c-Met was upregulated and activated in cells and tumors from doubly altered mice.
  • miR-34a was lower in cells from doubly altered mice than in wild-type cells. Restoring miR-34a lowered c-Met protein, and activating p53 with etoposide lowered c-Met. Knocking down p53 in wild-type cells lowered miR-34a and modestly raised c-Met protein.
  • The c-Met inhibitor SU11274 inhibited wound closure and migration of cells from doubly altered mice. It also reduced the invasiveness of all 3 cell lines tested. c-Met inhibitors also reduced spheroid size.
• The authors' conclusion: The authors concluded that inactivation of Nf2 and Cdkn2a cooperates to drive aggressive malignant mesotheliomas with enhanced invasive and metastatic potential and cancer-stem-cell-like features. In their model, they linked this to c-Met upregulation through a p53- and miR-34a-dependent mechanism.
• Limitations the authors state:
  • The authors noted that the cell migration (scratch) assay addresses only one aspect of metastasis.

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, STEM, Malignant Mesothelioma, CDKN2A, Ascites, Diaphragm, Pleural Cavity.

Related studies

• Similar tumor suppressor gene alteration profiles in asbestos-induced murine and human mesothelioma — C. Lecomte, P. Andujar, et al. (2005)
• Multipotent cancer stem cells derived from human malignant peritoneal mesothelioma promote tumorigenesis — S. Varghese, R. Whipple, et al. (2012)
• Inhibition of mesothelioma cancer stem-like cells with adenovirus-mediated NK4 gene therapy — X.B. Deng, L. Xiao, et al. (2015)
• Bap1 Is a Bona Fide Tumor Suppressor: Genetic Evidence from Mouse Models Carrying Heterozygous Germline Bap1 Mutations — Y. Kadariya, M. Cheung, et al. (2016)
• Caveolin-1 regulates lung cancer stem-like cell induction and p53 inactivation in carbon nanotube-driven tumorigenesis — S. Luanpitpong, L. Wang, et al. (2014)
• Asbestos, chromosomal deletions, and tumor suppressor gene alterations in human malignant mesothelioma — S.S. Murthy, J.R. Testa (1999)

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