SHP-2 tyrosine phosphatase inhibits p73-dependent apoptosis and expression of a subset of p53 target genes induced by EGCG
Authors: Munna L Agarwal
Vijay S Thakur
Hasan Mukhtar
Gen Sheng Feng
Rajib K Paul
Cheng-Kui Qu
A R M Ruhul Amin
Journal: Proceedings of the National Academy of Sciences of the United States of America (2007)
Discipline: Multidisciplinary
Keywords: Green tea polyphenol; EGCG; cancer cells; p53; apoptosis
Affiliations: Department of Genetics, Case Western Reserve University, Cleveland, OH 44106, USA.

Abstract:  Green tea polyphenol, epigallocatechin-3-gallate (EGCG) differentially regulates the cellular growth of cancer cells in a p53-dependent manner through apoptosis and/or cell cycle arrest. In an effort to further elucidate the mechanism of differential growth regulation by EGCG, we have investigated the role of the tyrosine phosphatase, SHP-2. Comparing the responses of mouse embryonic fibroblasts (MEFs), expressing either WT or functionally inactive/truncated SHP-2, we find that inactivation of SHP-2 remarkably sensitizes cells to EGCG-mediated killing. MEFs lacking functional SHP-2 undergo massive apoptosis upon treatment with EGCG. By comparing gene expression profiles, we have identified a set of transcriptional targets of p53 that are differentially modulated in cells undergoing apoptosis. Western blot and real-time PCR analyses of a select group of genes further confirm that the expression is SHP-2-dependent. Similar observations were made in MEFs lacking p53, confirming that the expression of these "p53 target genes" is p53-independent. In addition, EGCG treatment induced the expression of p73 mRNA and protein in both cell types, but not p63. Inactivation of p73 in cells expressing nonfunctional SHP-2 markedly inhibited apoptosis and p53 target gene expression. Although phosphorylation of JNK is differentially regulated by SHP2, it was found to be dispensable for EGCG-induced apoptosis and p53 target gene expression. Our results have identified SHP-2 as a negative regulator of EGCG-induced-apoptosis and have identified a subset of p53 target genes whose expression is paradoxically not mediated by p53 but by one of its family members, p73. 

Retracted: No

PubPeer comments:
 Figure 1A.  , 
 Figure 2. https: imgur.com jGZziGs , 
 Thank you very much for bringing this to my attention. These experiments were done in between 2004-2006. I left Dr. Agarwal s lab in July 2007 leaving all films and notes. In a couple of years, the lab has been closed permanently. I could not recall anything after so many years. From the pointed figures, I could say that there is no indication of data manipulation to get advantage or change scientific conclusion. Fig. 1A describes development of rescue clones (R7 and R10) and expression of full length SHP2 is important. Actin indicates loading and needs not to be same in this case. In fact, it is not same for C10. It is common practice to pick up multiple clones for screening to find out positive clones. It is possible that the actin is from the initial raw screening in which negative clone(s) (C8, C9) were spliced out to bring C10 after C7. Since WT, vector, C7 and C10 were used for subsequent experiments, only these four lysates were run again to confirm expression of SHP-2 in C7 and C10 but used the previous actin. For Fig. 2C, the splicing is not clear to me but there is a faint line. I could only say that Fig. 2A, B and C were used together to draw the scientific conclusion (expression of p53 target genes in SHP2 mutant cells), which could be drawn without MDM2 in 2C. In fact, MDM2 is not in 2D, which is used to draw the conclusion that EGCG and DNA damaging agents have different signaling. Again, this is my understanding from the figures. ,