Epigenetic silencing of peroxisome proliferator-activated receptor γ is a biomarker for colorectal cancer progression and adverse patients' outcome
Authors: Massimo Pancione
Nicola Forte
Lina Sabatino
Vincenzo Carafa
Lucia Altucci
Nicola Normanno
Angela Nebbioso
Antonio Febbraro
Concetta Ambrosino
Domenico Parente
Alessandra Fucci
Vittorio Colantuoni
Journal: PLoS ONE (2010)
Discipline: Multidisciplinary
Keywords: PPARG; epigenetic changes; colorectal cancer; methylation; promoter
Affiliations: Department of Biological and Environmental Sciences, University of Sannio, Benevento, Italy.

Abstract:  The relationship between peroxisome proliferator-activated receptor γ (PPARG) expression and epigenetic changes occurring in colorectal-cancer pathogenesis is largely unknown. We investigated whether PPARG is epigenetically regulated in colorectal cancer (CRC) progression. PPARG expression was assessed in CRC tissues and paired normal mucosa by western blot and immunohistochemistry and related to patients' clinicopathological parameters and survival. PPARG promoter methylation was analyzed by methylation-specific-PCR and bisulphite sequencing. PPARG expression and promoter methylation were similarly examined also in CRC derived cell lines. Chromatin immunoprecipitation in basal conditions and after epigenetic treatment was performed along with knocking-down experiments of putative regulatory factors. Gene expression was monitored by immunoblotting and functional assays of cell proliferation and invasiveness. Methylation on a specific region of the promoter is strongly correlated with PPARG lack of expression in 30% of primary CRCs and with patients' poor prognosis. Remarkably, the same methylation pattern is found in PPARG-negative CRC cell lines. Epigenetic treatment with 5'-aza-2'-deoxycytidine can revert this condition and, in combination with trichostatin A, dramatically re-activates gene transcription and receptor activity. Transcriptional silencing is due to the recruitment of MeCP2, HDAC1 and EZH2 that impart repressive chromatin signatures determining an increased cell proliferative and invasive potential, features that can experimentally be reverted. Our findings provide a novel mechanistic insight into epigenetic silencing of PPARG in CRC that may be relevant as a prognostic marker of tumor progression. 

Retracted: No

PubPeer comments:
 The correction is about a grant number. It does not address the data in figures 1E, 2B or 5F. , 
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 2019 retraction. https: journals.plos.org plosone article?id=10.1371 journal.pone.0227376 Following publication of [1], concerns were raised about results reported in Figs 1, 2, and 5: Fig 1E M4-T-M panel lanes 4u20138 and C+ appear similar to M1-NM-U panel lanes 1u20136 and to Fig 2B M3-U panel lanes 1u20136; Fig 1E M1-NM-U panel appears similar to Fig 2B M3-U panel; In Fig 5F, the Control panel appears similar to the sh-CC panel for the invasion assay. The authors commented that this resulted from an error in figure preparation. The authors provided original data, where available, as well as replication experiments to support the results in the article but explained that the data underlying the panels of concern are no longer available. The submission of replication data, however, does not address the concerns raised about the similarities in the figures identified above, and we have been unable to resolve these concerns due to the unavailability of the original image data. As of the date of this retraction, no concerns have been raised to PLOS ONE about other figures in the article. The authors noted that primary data underlying Fig 1A u03b2-actin panel lanes 1u20138, Fig 1C, Fig 1G, Fig 2A, 2B and 2D, Fig 4A, 4D and 4F and Fig 5D, 5F, 5G and 5I are unavailable. Original data supporting the other figures, as well as replication data supporting several results, are available from the authors. The authors apologize for any inconvenience this retraction may cause for readers and regret not being able to provide the underlying data for the panels of concern because, according to the authors, the data was lost during the time passed. The authors furthermore claim that the results reported in the paper are robust and the conclusions are valid. However, in light of the unresolved concerns about the results reported in Figs 1, 2 and 5, the PLOS ONE Editors retract this article. LS, LA, and V Colantuoni did not agree with the retraction. MP, A Fucci, CA, agree with the retraction. Per the corresponding author, NF, A Febbraro, DP, NN, also agree with the retraction. V Carafa and AN did not clarify directly to the journal whether they agree or disagree with the retraction. V Carafa, AN, and LA noted that they stand for the results in Fig 3 for which they provided the original data corresponding to those published. The original author contributions for the article state: u201cConceived and designed the experiments: MP LA VC. Performed the experiments: MP LS A. Fucci VC AN CA NN. Analyzed the data: MP LS A. Fucci VC AN LA VC. Contributed reagents materials analysis tools: LS A. Fucci AN NF A. Febbraro DP CA NN. Wrote the paper: MP LA VC.u201d Reference 1.Pancione M, Sabatino L, Fucci A, Carafa V, Nebbioso A, Forte N, et al. (2010) Epigenetic Silencing of Peroxisome Proliferator-Activated Receptor u03b3 Is a Biomarker for Colorectal Cancer Progression and Adverse Patients Ou , 
 I noticed an additional concern in this already retracted paper. Two images in Figure 5I appear to overlap, after horizontal stretch and 180-degree rotation. *** ![file] ,