MAZ drives tumor-specific expression of PPAR gamma 1 in breast cancer cells

• Published in: Breast cancer research and treatment 2008-09, Vol.111 (1), p.103-111
• Main Authors: Wang, Xin, Southard, R. Chase, Allred, Clinton D., Talbert, Dominique R., Wilson, Melinda E., Kilgore, Michael W.
• Format: Article
• Language: English
• Subjects: Binding sites; Biological and medical sciences; Blotting, Western; Breast cancer; Breast Neoplasms - genetics; Breast Neoplasms - metabolism; Cancer research; Cancer therapies; Cell Line, Tumor; Cellular biology; Disease Progression; DNA-Binding Proteins - metabolism; Female; Gene Expression; Gene Expression Regulation, Neoplastic; Gynecology. Andrology. Obstetrics; Humans; Immunoprecipitation; Mammary gland diseases; Medical sciences; Medicine; Medicine & Public Health; Oligonucleotide Array Sequence Analysis; Oncology; Plasmids; PPAR gamma - biosynthesis; PPAR gamma - genetics; Preclinical Study; Promoter Regions, Genetic; Reverse Transcriptase Polymerase Chain Reaction; Transcription Factors - metabolism; Transfection; Tumors
• ISSN: 0167-6806; 1573-7217
• DOI: 10.1007/s10549-007-9765-7

The peroxisome proliferator-activated receptor gamma 1 (PPARγ1) is a nuclear receptor that plays a pivotal role in breast cancer and is highly over-expressed relative to normal epithelia. We have previously reported that the expression of PPARγ1 is mediated by at least six distinct promoters and expression in breast cancer is driven by a tumor-specific promoter (pA1). Deletional analysis of this promoter fragment revealed that the GC-rich, 263 bp sequence proximal to the start of exon A1, is sufficient to drive expression in breast cancer cells but not in normal, human mammary epithelial cells (HMEC). By combining the disparate technologies of microarray and computer-based transcription factor binding site analyses on this promoter sequence the myc-associated zinc finger protein (MAZ) was identified as a candidate transcription factor mediating tumor-specific expression. Western blot analysis and chromatin immunoprecipitation assays verify that MAZ is overexpressed in MCF-7 cells and is capable of binding to the 263 bp promoter fragment, respectively. Furthermore, the over-expression of MAZ in HMEC is sufficient to drive the expression of PPARγ1 and does so by recruiting the tumor-specific promoter. This results in an increase in the amount of PPARγ1 capable of binding to its DNA response element. These findings help to define the molecular mechanism driving the high expression of PPARγ1 in breast cancer and raise new questions regarding the role of MAZ in cancer progression.