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Open Access Research

Amplification of Mdmx and overexpression of MDM2 contribute to mammary carcinogenesis by substituting for p53 mutations

Qiong Yu1, Yan Li2, Kun Mu1, Zhishuang Li1, Qingyong Meng3, Xiaojuan Wu1, Yan Wang1 and Li Li1*

Author Affiliations

1 Department of Pathology, Shandong University School of Medicine, 44#,Wenhua Xi Road, 250012 Jinan, Shandong, PR. China

2 Department of Medical Oncology, Shandong Cancer Hospital and Institute, Jinan University, 250117 Jinan, Shandong, PR. China

3 The No.2 People’s Hospital of Jinan, 148#, Jingyi Road, 250001 Jinan, Shandong, People’s Republic of China

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Diagnostic Pathology 2014, 9:71  doi:10.1186/1746-1596-9-71

Published: 25 March 2014

Abstract

Background

The p53 tumor suppressor gene is mutated or deleted in nearly half of human cancers. The murine double minute 2 (Mdm2) and Mdmx represent two important cellular regulators of p53. The aim of this study was to evaluate the abnormalities of p53, Mdmx and Mdm2 genes in archived breast cancers.

Methods

We assessed the genetic instability at p53, Mdmx and Mdm2 using high resolution multi-color fluorescent in situ hybridization (FISH) protocol and detected the expression status of the tumor protein p53 (TP53), MDMx and MDM2 by immunohistochemistry in 115 archived samples of infiltrating ductal breast carcinomas with foci of ductal carcinoma in situ (DCIS) components.

Results

The presence of p53 allelic loss and/or TP53 overexpression was observed in 38% out of all patients, and was significantly more often in larger, high grade, ER negative and high ki67 tumors. Mdmx amplification with low-level increase of gene copy number is at high frequency while Mdm2 amplification is rare in primary breast cancer. Mdmx amplification was seen in more invasive carcinomas than preinvasive lesions. MDMx and MDM2 overexpression were detected in 65% and 38% of all cases respectively. Moreover it was showed that most tumors contained either p53 dysfunction or Mdm2 alteration, but not both. This distribution was significant (P < 0.05). Inverse correlation between Mdmx amplification/overexpression and p53 disfunction was also observed (P < 0.05).

Conclusions

Our results suggest the involvement of Mdm2 and Mdmx in p53-independent breast carcinogenesis and Mdmx may contribute to the regulation of p53 independently of Mdm2.

Virtual slides

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1450529994118798 webcite.

Keywords:
Breast cancer; p53; Mdmx; Mdm2; FISH