Germline BAP1 mutations induce a Warburg effect

Our plain-English summary of Germline BAP1 mutations induce a Warburg effect, by A. Bononi, H. Yang, C. Giorgi, et al (Cell Death and Differentiation, 2017).

The study

• Authors: A. Bononi, H. Yang, C. Giorgi, S. Patergnani, L. Pellegrini, M. Su, G. Xie, V. Signorato, S. Pastorino, P. Morris, G. Sakamoto, S. Kuchay, G. Gaudino, H.I. Pass, A. Napolitano, P. Pinton, W. Jia, M. Carbone
• Journal: Cell Death and Differentiation
• Published: 2017;24(10):1694-1704
• Cited by: 110 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Carriers of heterozygous germline BAP1 mutations (BAP1+/-) develop cancer. We studied plasma from 16 BAP1+/- individuals from 2 families carrying different germline BAP1 mutations and 30 BAP1 wild-type (BAP1WT) controls from these same families. Plasma samples were analyzed by liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS), ultra-performance liquid chromatography triple quadrupole mass spectrometry (UPLC-TQ-MS), and gas chromatography time-of-flight mass spectrometry (GC-TOF-MS). We found a clear separation in the metabolic profile between BAP1WT and BAP1+/- individuals. We confirmed the specificity of the data in vitro using 12 cell cultures of primary fibroblasts we derived from skin punch biopsies from 12/46 of these same individuals, 6 BAP1+/- carriers and 6 controls from both families. BAP1+/- fibroblasts displayed increased aerobic glycolysis and lactate secretion, and reduced mitochondrial respiration and ATP production compared with BAP1WT. siRNA-mediated downregulation of BAP1 in primary BAP1WT fibroblasts and in primary human mesothelial cells, led to the same reduced mitochondrial respiration and increased aerobic glycolysis as we detected in primary fibroblasts from carriers of BAP1+/- mutations. The plasma and cell culture results were highly reproducible and were specifically and only linked to BAP1 status and not to gender, age or family, or cell type, and required an intact BAP1 catalytic activity. Accordingly, we were able to build a metabolomic model capable of predicting BAP1 status with 100% accuracy using data from human plasma. Our data provide the first experimental evidence supporting the hypothesis that aerobic glycolysis, also known as the 'Warburg effect', does not necessarily occur as an adaptive process that is consequence of carcinogenesis, but rather that it may also predate malignancy by many years and facilitate carcinogenesis.

In plain English

This laboratory study asked whether people who inherit one faulty copy of the BAP1 gene (carriers) produce energy differently from relatives without the mutation. The authors analyzed plasma from 46 members of two unrelated families, from Wisconsin and Louisiana, who carry different BAP1 mutations. These were 16 carriers and 30 non-carriers, giving 61 samples collected over 2 years. They also grew skin cells (fibroblasts) from 6 carriers and 6 non-carriers. Blood chemistry profiles separated carriers from non-carriers. In a blinded test, 41 unrelated healthy people were classified as non-carriers, and so was one relative whose status was unknown at the time, which genetic testing later confirmed. Carriers' fibroblasts showed a higher rate of glycolysis (28.05 ± 1.76 versus 16.73 ± 1.52 mpH/min), more lactate release, lower mitochondrial respiration and less cellular ATP. Reducing BAP1 in non-carrier fibroblasts and in mesothelial cells produced similar changes. Restoring working BAP1 in carrier cells reversed the changes; an inactive form did not. Asbestos exposure was not studied. The authors concluded that this 'Warburg effect' occurs in normal cells of carriers and may contribute to their high cancer incidence. They said the mechanism is unknown.

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: metabolomic analysis of human plasma plus cell culture experiments on primary fibroblasts and primary mesothelial cells, including gene silencing and gene re-introduction
• Who was studied: 46 members of two unrelated families (Wisconsin and Louisiana) with different germline BAP1 mutations. The Wisconsin family contributed 7 carriers and 7 non-carriers; the Louisiana family contributed 9 carriers and 23 non-carriers. There were 61 plasma samples over 2 years (37 from non-carriers, 24 from carriers). Fibroblast cultures came from 6 carriers and 6 non-carriers. A blinded test set also included 41 healthy controls unrelated to the families.
• Exposure: Inherited (germline) heterozygous BAP1 mutation status, and experimental reduction or restoration of BAP1 in cultured cells. The study did not measure or study asbestos exposure.
• Main results:
  • In blinded testing, the plasma model classified the one family member of unknown BAP1 status as a non-carrier, which genetic testing later confirmed. The 41 unrelated healthy controls were also classified as non-carriers.
  • The rate of glycolysis was higher in carrier fibroblasts (28.05 ± 1.76 mpH/min) than in non-carrier fibroblasts (16.73 ± 1.52 mpH/min).
  • Lactate in the culture medium was significantly higher for carrier fibroblasts than for non-carrier fibroblasts, by 32.75% ± 11.24.
  • Basal mitochondrial respiration was lower in carrier fibroblasts (65.78 ± 4.38 pMoles/min) than in non-carrier fibroblasts (111.20 ± 6.92 pMoles/min).
  • Carrier cells had lower total intracellular ATP than non-carrier cells.
  • Glycerol 3-phosphate and citrate were lower in carrier fibroblasts, but these differences were not statistically significant.
  • Silencing BAP1 in primary human mesothelial cells gave results similar to those in silenced fibroblasts.
  • Adding back normal BAP1 restored mitochondrial respiration in carrier fibroblasts. A catalytically inactive BAP1 (C91S) did not.
  • Carrier and non-carrier fibroblasts did not differ in mitochondrial number.
  • Carrier and non-carrier fibroblasts did not differ significantly in the expression of genes for the energy-metabolism enzymes examined.
• The authors' conclusion: The authors concluded that the Warburg effect, a hallmark of cancer cells, is also found in normal cells from people carrying heterozygous germline BAP1 mutations. They concluded it may contribute to the high incidence of cancer observed among these carriers.
• Limitations the authors state:
  • The authors state that the mechanism behind the metabolic changes is not known.

Topics

Medical terms in this study, explained in our Lexicon: BAP1 Tumor Predisposition Syndrome, BAP1, Fibroblast, Mesothelial Cells, Carcinogenesis.

Related studies

• BAP1 regulates IP3R3-mediated Ca2+ flux to mitochondria suppressing cell transformation — A. Bononi, C. Giorgi, et al. (2017)
• BAP1 forms a trimer with HMGB1 and HDAC1 that modulates gene × environment interaction with asbestos — F. Novelli, A. Bononi, et al. (2021)
• Germline BAP1 mutations predispose to malignant mesothelioma — J.R. Testa, M. Cheung, et al. (2011)
• Minimal asbestos exposure in germline BAP1 heterozygous mice is associated with deregulated inflammatory response and increased risk of mesothelioma — A. Napolitano, L. Pellegrini, et al. (2016)
• A recurrent germline BAP1 mutation and extension of the BAP1 tumor predisposition spectrum to include basal cell carcinoma — K.A. Wadt, L.G. Aoude, et al. (2015)
• High Incidence of Somatic BAP1 alterations in sporadic malignant mesothelioma — M. Nasu, M. Emi, et al. (2015)

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