Improvement of the methylation specific PCR technical conditions for the detection of p16 promoter hypermethylation in small amounts of tumor DNA

Characterization of the Methylation Status of Pax7 and Myogenic Regulator Factors in Cell Myogenic Differentiation

Epigenetic processes in the development of skeletal muscle have been appreciated for over a decade. DNA methylation is a major epigenetic modification important for regulating gene expression and suppressing spurious transcription. Up to now, the importance of epigenetic marks in the regulation of Pax7 and myogenic regulatory factors (MRFs) expression is far less explored. In the present study, semi-quantitative the real-time polymerase chain reaction (RT-PCR) analyses showed MyoD and Myf5 were expressed in activated and quiescent C2C12 cells. MyoG was expressed in a later stage of myogenesis. Pax7 was weakly expressed in differentiated C2C12 cells. To further understand the regulation of expression of these genes, the DNA methylation status of Pax7, MyoD, and Myf5 was determined by bisulfite sequencing PCR. During the C2C12 myoblasts fusion process, the changes of promoter and exon 1 methylation of Pax7, MyoD, and Myf5 genes were observed. In addition, an inverse relationship of low methylation and high expression was found. These results suggest that DNA methylation may be an important mechanism regulating Pax7 and MRFs transcription in cell myogenic differentiation.

Regulation of MLH1 mRNA and protein expression by promoter methylation in primary colorectal cancer: a descriptive and prognostic cancer marker study

BACKGROUND

In colorectal cancer MLH1 deficiency causes microsatellite instability, which is relevant for the patient's prognosis and treatment, and its putative heredity. Dysfunction of MLH1 is caused by sporadic gene promoter hypermethylation or by hereditary mutations as seen in Lynch Syndrome. The aim of this study was to determine in detail how DNA methylation regulates MLH1 expression and impacts clinical management.

METHODS

Colorectal cancer samples were collected from 210 patients. The laboratory methods used to study these samples included methylation specific multiplex ligation-dependent probe amplification (MS-MLPA), real-time quantitative PCR (qPCR), and immunohistochemistry (IHC).

RESULTS

We found that the MLH1 mRNA and protein expression levels were highly related. MS-MLPA was successful in tumors from 195 patients. In these tumors, hypermethylation was observed in promoter regions A (n = 57), B (n = 30), C (n = 28), and D (n = 47), and in intron 1 (n = 25). The promoter region C and intron 1 methylation levels were found to be excellently suited for discriminating between low and high gene expression levels, whereas those of promoter regions A, B and D were less specific. Hypermethylation in any region (n = 77) served as an independent prognostic factor (hazard ratio 0.56, 95 % confidence interval 0.36-0.89, p = 0.01).

CONCLUSIONS

MLH1 inactivation through hypermethylation was found to be related to improved survival. Hypermethylation in promoter region C and intron 1 served as the most specific markers for this inactivation.

Epithelial to mesenchymal transition: expression of the regulators snail, slug, and twist in pancreatic cancer

PURPOSE

Epithelial to mesenchymal transitions are vital for tumor growth and metastasis. Several inducers of epithelial to mesenchymal transition are transcription factors that repress E-cadherin expression, such as Snail, Slug, and Twist. In this study, we aimed to examine the expression of these transcription factors in pancreatic cancer.

EXPERIMENTAL DESIGN

The expression of Snail, Slug, and Twist was detected by immunohistochemistry in tissue samples from patients with pancreatic ductal adenocarcinoma. Five human pancreatic cancer cell lines (AsPC-1, Capan-1, HPAF-2, MiaPaCa-2, and Panc-1) were analyzed by reverse transcription-PCR, real-time PCR, and Western blotting. An orthotopic nude mouse model of pancreatic cancer was applied for in vivo experiments.

RESULTS

Seventy-eight percent of human pancreatic cancer tissues showed an expression of Snail, and 50% of the patients displayed positive expression of Slug. Twist showed no or only weak expression. Snail expression was higher in undifferentiated cancer cell lines (MiaPaCa-2 and Panc-1) than in more differentiated cell lines (Capan-1, HPAF-2, AsPC-1). Expression of Slug was detected in all cell lines with different intensities. Twist was not expressed. After exposure to hypoxia, the Twist gene was activated in all five pancreatic cancer cell lines.

CONCLUSIONS

The transcription factors Snail and Slug are expressed in pancreatic cancer but not in normal tissue, suggesting a role in the progression of human pancreatic tumors. Twist, activated by hypoxia, may play an important role in the invasive behavior of pancreatic tumors.