Mesothelin promoter variants are associated with increased soluble mesothelin-related peptide levels in asbestos-exposed individuals

Our plain-English summary of Mesothelin promoter variants are associated with increased soluble mesothelin-related peptide levels in asbestos-exposed individuals, by C. De Santi, P. Pucci, A. Bonotti, et al (Occupational and Environmental Medicine, 2017).

The study

• Authors: C. De Santi, P. Pucci, A. Bonotti, O. Melaiu, M. Cipollini, R. Silvestri, V. Vymetalkova, E. Barone, E. Paolicchi, A. Corrado, I. Lepori, I. Dell'Anno, L. Pellè, P. Vodicka, L. Mutti, R. Foddis, A. Cristaudo, F. Gemignani, S. Landi
• Journal: Occupational and Environmental Medicine
• Published: 2017;74(6):456-463
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Soluble mesothelin-related peptide (SMRP) is a promising diagnostic biomarker for malignant pleural mesothelioma (MPM), but various confounders hinder its usefulness in surveillance programmes. We previously showed that a single nucleotide polymorphism (SNP) within the 3'untranslated region (3'UTR) of the mesothelin (MSLN) gene could affect the levels of SMRP.

Objectives: To focus on SNPs located within MSLN promoter as possible critical genetic variables in determining SMRP levels.

Methods: The association between SMRP and SNPs was tested in 689 non-MPM subjects and 70 patients with MPM. Reporter plasmids carrying the four most common haplotypes were compared in a dual luciferase assay, and in silico analyses were performed to investigate the putative biological role of the SNPs.

Results: We found a strong association between serum SMRP and variant alleles of rs3764247, rs3764246 (in strong linkage disequilibrium with rs2235504) and rs2235503 in non-MPM subjects. Inclusion of the genotype information led to an increase in SMRP specificity from 79.9% to 85.5%. Although not statistically significant, the group with MPM showed the same trend of association. According to the in vitro luciferase study, rs3764247 itself had a functional role. In silico approaches showed that the binding sites for transcription factors such as Staf and ZNF143 could be affected by this SNP. The other SNPs were shown to interact with each other in a more complex way.

Conclusions: These data support the suggestion that SMRP performance is affected by individual (ie, genetic) variables and that MSLN expression is influenced by SNPs located within the promoter regulatory region.

© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

In plain English

This study from Pisa, Italy, asked whether inherited variants in the control region (promoter) of the mesothelin gene relate to blood levels of soluble mesothelin-related peptide (SMRP), a proposed marker for malignant pleural mesothelioma. Participants were asbestos-exposed workers: 371 healthy, 318 with benign respiratory diseases and 70 with mesothelioma. Among the 689 without mesothelioma, SMRP rose with the number of variant copies for each of three variants. Mesothelioma patients showed similar, non-significant trends. Ignoring genotype, at a 1.28 nM cut-off, the test had 76.7% sensitivity and 79.9% specificity. Comparing non-mesothelioma subjects carrying no variants with all mesothelioma patients, the best cut-off was 1.11 nM, with 83.6% sensitivity and 85.5% specificity. For non-mesothelioma subjects carrying any variant, specificity was 67% at 1.28 nM. In cell tests, the promoter version with only the rs3764247 variant reached 182% and 191% of the common version in two cell lines; the all-variant version reached 121% and 194%. The authors concluded that SMRP levels are affected by genetic variants, implying different warning thresholds for different genotypes. They noted that the mesothelioma group was small.

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: Genetic association study in an occupational surveillance population, combined with laboratory (in vitro) reporter-gene experiments in cell lines and computer-based (in silico) database analyses
• Who was studied: 759 volunteers recruited at the University Hospital of Pisa, Italy. They were 371 healthy individuals, 318 patients with benign respiratory diseases (including pleural plaques, pleural thickening, asbestosis and others) and 70 patients with malignant pleural mesothelioma (42 epithelioid, 15 sarcomatoid, 13 biphasic). Most were male. Recruitment dates were not given. The laboratory work used non-malignant human pleural mesothelial cells (Met-5A) and epithelioid malignant mesothelioma cells (Mero-14).
• Exposure: All participants were workers previously exposed to asbestos. Fiber types and products were not reported. The variable actually studied was each person's genotype for promoter variants of the mesothelin gene (rs3764247, rs3764246 and rs2235503), which was compared with serum SMRP levels.
• Main results:
  • Patients with malignant pleural mesothelioma had a mean serum SMRP of 3.58 nM (plus or minus 0.49 SEM). This was significantly higher than in healthy subjects (0.94 plus or minus 0.03) or in patients with benign respiratory disease (1.04 plus or minus 0.03).
  • In the non-mesothelioma group (healthy subjects and patients with benign respiratory disease), SMRP was significantly associated with all three variants, and levels rose with the number of variant alleles. For example, for rs3764247 in healthy subjects, mean SMRP was 0.76 nM in AA carriers (237 people), 1.20 nM in AC carriers (119) and 1.75 nM in CC carriers (15).
  • Among the 70 patients with mesothelioma, similar trends were seen, but none of the differences was statistically significant (p=0.166, 0.363 and 0.373 for rs3764247, rs3764246 and rs2235503).
  • Participants were grouped as carrying no variant allele ('L genotype') or at least one variant allele ('H genotype'). SMRP levels were associated with genotype (p=0.001) and with diagnosis (p less than 0.0001).
  • Ignoring genotype, SMRP distinguished mesothelioma from non-mesothelioma subjects with an area under the curve of 0.867 (95% CI 0.841 to 0.890). At a cut-off of 1.28 nM, sensitivity was 76.7% and specificity was 79.9%.
  • Non-mesothelioma subjects with the L genotype (n=374) were compared against all mesothelioma patients. This gave an area under the curve of 0.922. At a cut-off of 1.11 nM, sensitivity was 83.6% and specificity was 85.5%.
  • Non-mesothelioma subjects with the H genotype (n=315) were compared against all mesothelioma patients. This gave an area under the curve of 0.801, with specificity of 67% at a cut-off of 1.28 nM.
  • In the cell experiments, reporter activity was measured relative to the common promoter version (set at 100%). For the version carrying only the rs3764247 variant (HAP4), activity was 182% in Met-5A cells and 191% in Mero-14 cells (p=0.0031 and 0.034 versus the common version). For the version carrying all four variants (HAP2), activity was 121% in Met-5A cells and 194% in Mero-14 cells (p=0.064 and 0.028). The version carrying variants at the second and fourth positions (HAP3) did not differ significantly from the common version.
  • Database analysis suggested that rs3764247 may affect binding sites for the transcription factors Staf and ZNF143.
• The authors' conclusion: The authors concluded that SMRP levels are affected by genetic variants, resulting in different 'warning' thresholds for healthy subjects with different genotypes. They also concluded that some of these variants appear to have a functional role that needs further investigation.
• Limitations the authors state:
  • The authors suggested that the lack of statistical significance among mesothelioma patients may be due to the small number of mesothelioma patients recruited.
  • In the analysis that split mesothelioma patients by genotype, only 37 and 33 patients fell into the two groups.
  • The variants were chosen using gene-expression data from lung tissue, because data on pleural tissue were unavailable.
  • The authors stated that further studies are needed to confirm the role of rs3764247 in regulating the mesothelin gene.
  • The authors stated that identifying variants that explain false-negative results (low SMRP in mesothelioma patients) would require a larger sample of mesothelioma patients.

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: Mesothelin, Soluble Mesothelin-Related Peptides (SMRP), Biomarker, Pleural Mesothelioma.

Related studies

• A common polymorphism within MSLN affects miR-611 binding site and soluble mesothelin levels in healthy people — S. Garritano, C. De Santi, et al. (2014)
• Two novel polymorphisms in 5' flanking region of the mesothelin gene are associated with soluble mesothelin-related peptide (SMRP) levels — A. Cristaudo, R. Foddis, et al. (2011)
• Soluble mesothelin-related peptide level elevation in mesothelioma serum and pleural effusions — H.I. Pass, A. Wali, et al. (2008)
• Soluble mesothelin-related peptides levels in patients with malignant mesothelioma — A. Franko, V. Dolzan, et al. (2012)
• Evaluation of soluble mesothelin-related peptides and MSLN genetic variability in asbestos-related diseases — K. Goricar, V. Kovac, et al. (2020)
• Soluble Mesothelin-Related Peptides to Monitor Recurrence After Resection of Pleural Mesothelioma — B.M. Burt, H.S. Lee, et al. (2017)

Browse more research in Occupational and Environmental Medicine, or return to medical research.