BP1, an isoform of DLX4 homeoprotein, negatively regulates BRCA1 in sporadic breast cancer.

INTRODUCTION: Several lines of evidence point to an important role for BP1, an isoform of DLX4 homeobox gene, in breast carcinogenesis and progression. BRCA1 is a well-known player in the etiology of breast cancer. While familial breast cancer is often marked by BRCA1 mutation and subsequent loss of heterozygosity, sporadic breast cancers exhibit reduced expression of wild type BRCA1, and loss of BRCA1 expression may result in tumor development and progression. METHODS: The Cister algorithm and Genomatix program were used to identify potential BP1 binding sites in BRCA1 gene. Real-time PCR, Western blot and immunohistochemistry analysis were performed to verify the expression of BRCA1 and BP1 in cell lines and breast cancer tissues. Double-stranded siRNA transfection was carried out for silencing BP1 expression. ChIP and EMSA were used to confirm that BP1 specifically binds to BRCA1. RESULTS: A putative BP1 binding site was identified in the first intron of BRCA1, which was confirmed by chromatin immunoprecipiation and electrophoresis mobility shift assay. BP1 and BRCA1 expression were inversely correlated in breast cancer cell lines and tissues, suggesting that BP1 may suppress BRCA1 transcription through consensus sequence binding. CONCLUSIONS: BP1 homeoprotein represses BRCA1 expression through direct binding to its first intron, which is consistent with a previous study which identified a novel transcriptional repressor element located more than 500 base pairs into the first intron of BRCA1, suggesting that the first intron plays an important role in the negative regulation of BRCA1. Although further functional studies are necessary to confirm its repressor activity towards BRCA1, the elucidation of the role of BP1 in breast tumorigenesis holds great promise in establishing BP1 as a novel target for drug therapy.

TCF7L2 expression in diabetic patients undergoing bariatric surgery.

INTRODUCTION: The cause of diabetes in morbidly obese patients is multifactorial, including genetic, social, and dietary components. Transcription factor 7-like 2 (TCF7L2) is a gene that is related to the development of diabetes. This pilot study examines TCF7L2 expression in liver samples obtained from morbidly obese patients undergoing bariatric surgery. TCF7L2 expression is compared between diabetic and nondiabetic patients. METHODS: Liver samples were obtained from 20 morbidly obese patients undergoing bariatric surgery. Samples were flash frozen in liquid nitrogen. Total RNA was extracted from tissue samples using the TRIzol reagent (Invitrogen Inc, Carlsbad, CA). Using the iScript cDNA synthesis kit (Bio-Rad Laboratories, Hercules,CA), cDNA was synthesized. Quantitative polymerase chain reaction (qPCR) was done using SYBR Green qPCR Reagents (Stratagene, Cedar Creek TX) and the 7300 Real-Time PCR system (Applied Biosystems, Foster City CA). Preoperative demographic and gene expression data were correlated using univariate analysis and logistic regression models. Only associations with a p-value less than 0.05 were considered significant. RESULTS: For the entire group, there was no correlation between body mass index (BMI) and TCF7L2 expression. In morbidly obese nondiabetic patients, there was a positive correlation between TCF7L2 expression and BMI (R(2)=0.21). In morbidly obese diabetic patients, there was an inverse correlation between TCF7L2 expression and BMI (R(2)=0.58). There was no significant relationship between TCF7L2 expression and age or glycosylated hemoglobin (HbA1c). CONCLUSIONS: The cause of diabetes is multifactorial but the data from our pilot study documents the relationship of TCF7L2 with type 2 diabetes in morbidly obese patients.

Expression of ectonucleotide pyrophosphate phosphodiesterase and peroxisome proliferator activated receptor gamma in morbidly obese patients.

BACKGROUND: Recently, two genes, peroxisome proliferator activated receptor gamma (PPARgamma) and ectonucleotide pyrophosphate phosphodiesterase (ENPP1), have been localized and associated with diabetes and obesity. This report hypothesizes that there is a correlation between the genetic expression of ENPP1 and PPARgamma from gastrointestinal tissue and body mass index (BMI). METHODS: Preoperative demographic data were collected from 16 severely morbidly obese patients. Extraneous gastrointestinal tissue was obtained during laparoscopic gastric bypass and gastric banding procedures. The tissue was snap frozen in liquid nitrogen. Initially, RNA extraction was performed on the tissue, followed by reverse transcription using appropriate primers and controls. Subsequently, the samples were subjected to quantitative polymerase chain reaction (PCR). Preoperative demographic data were analyzed for their influence on ENPP1 and PPARgamma expression using multivariate analysis and logistic regression models. RESULTS: Expression of PPARgamma and ENPP1 was found in all samples. There was a higher level of PPARgamma expression in omental tissue than in enteric tissue. There was no significant difference in the expression of ENPP1 among the different tissue types. The relative level of PPARgamma expression in small bowel and gastric tissue was found to be inversely proportional to body mass index (BMI) using linear regression analysis (p = 0.01; r (2) = 0.586). Similarly, PPARgamma expression from omental tissue showed an inverse relationship with BMI (p = 0.04; r (2 )= 0.576). The levels of ENPP1 expression did not show a correlation with BMI (p = 0.25). CONCLUSION: The results suggest that increasing obesity correlates with a decrease in PPARgamma expression. This decrease may induce dysfunctional adipocyte differentiation, maturation, and function, leading to diabetes and the metabolic syndrome. Similarly, the increased volume of adipose tissue may lead to a downregulation of PPARgamma. The lack of correlation between ENPP1 and BMI may suggest that glucose metabolism is more complex than lipid metabolism. Further evaluation is warranted to establish metabolic pathways for glucose and lipid biomarkers.