Functional analysis of the -2548G/A leptin gene polymorphism in breast cancer cells
Authors: Anna Mercanti
Stanislaw Sulkowski
Salim Merali
Marianna Terrasi
Eva Surmacz
Camilo A Moncada
Mariusz Koda
Antonio Russo
Elena Fiorio
Journal: International Journal of Cancer (2009)
Discipline: CLINICAL MEDICINE
Keywords: Leptin; breast cancer; Lep-2548G/A; Sp1; nucleolin
Affiliations: Sbarro Institute for Cancer Research and Molecular Medicine, Temple University, Philadelphia, PA 19122, USA.

Abstract:  Leptin is overexpressed in human breast tumors and is produced by breast cancer cells in response to obesity-related stimuli. The leptin promoter polymorphism Lep-2548G/A can be associated with increased leptin secretion by adipocytes and elevated cancer risk. However, molecular mechanisms underlying the link between Lep-2548G/A and breast cancer have never been addressed. Lep-2548G/A is proximal to a binding site for the transcriptional factor Sp1. Furthermore nucleolin, a transcriptional repressor, can bind Sp1 or its consensus site. Consequently, we focused on the impact of Lep-2548G/A on Sp1- and nucleolin-dependent leptin transcription in breast cancer cells. The Lep-2548G/A was identified in a homozygous conformation in BT-474 and SK-BR-3 breast cancer cells, in a heterozygous conformation in MDA-MB-231 cells, and a wild-type Lep-2548G/G sequence was present in MCF-7 and ZR-75-1 cells. The occurrence of Lep-2548A/A and Lep-2548G/A coincided with high and intermediate leptin mRNA expression, respectively, while cells containing Lep-2548G/G expressed low leptin mRNA levels. We demonstrated that the existence of Lep-2548G/A improved efficient recruitment of Sp1 to DNA under insulin treatment, while Sp1 loading on DNA containing Lep-2548G/G was not insulin-dependent. In contrast, nucleolin binding to Lep-2548G/A was downregulated in response to insulin, while it was not regulated on Lep-2548G/G. The presence of Lep-2548G/A was studied in breast cancer epithelial cells by IHC and LCM. Interestingly, all 14 tumors expressing high leptin levels contained Lep-2548A/A. In conclusion, the occurrence of Lep-2548G/A can enhance leptin expression in breast cancer cells via Sp1- and nucleolin-dependent mechanisms and possibly contribute to intratumoral leptin overexpression. 

Retracted: No

PubPeer comments:
 Figure 3a. Much more similar than you would expect. https: imgur.com o614uGO , 
 #1 Figure 3a continued. Much more similar than you would expect. https: imgur.com 7UGA8si , 
 2020 expression of concern. https: onlinelibrary.wiley.com doi full 10.1002 ijc.33275 u201cFunctional analysis of the u20102548G A leptin gene polymorphism in breast cancer cells.u201d Terrasi M, Fiorio E, Mercanti A, Koda M, Moncada CA, Sulkowski S, Merali S, Russo A, Surmacz E. Int. J. Cancer, 2009; 125(5):1038u201044. DOI: 10.1002 ijc.24372 This Expression of Concern is issued in relation to the above article, published online on 18 February 2009 in Wiley InterScience (www.interscience.wiley.com) and in Volume 125, ppu2010 1038u20101044, by agreement between the journal Editoru2010inu2010Chief, Prof. Christoph Plass and Wiley Periodicals LLC. The Expression of Concern has been rendered due to concerns about Figure 3a. In this Western Blot, the first three bands in the u201cSP1u201d and the u201cNucu201d lane (MCFu20107, Ins u2010 and +; MDAu2010MBu2010231, Ins u2010) look quite identical. Furthermore, the second (MCFu20107, Ins +) and the fifth band (BTu2010474, Ins u2010) in the u201cInputu201d lane look very similar, as well as the third (MDAu2010MB 231, Ins u2010) and the sixth band (BTu2010474, Ins +) in the u201cInputu201d lane. The authors are unable to retrieve the original data due to the time that has elapsed; therefore, duplication of the bands in question can neither be proven nor disproven. The first and senior authors stand by the conclusions of the paper and wish to point out that CHIP results presented in Figure 3a have been verified by an independent DAPA method shown in Figure 3b. Both methods suggest preferential recruitment of SPu20101 to Lepu20102548A A sequences under insulin treatment. ,