(The FASEB Journal. 2007;21:lb163)
© 2007 FASEB
Detection of methylation in African American breast tumors with quantitative multiplex methylation-specific PCR
Enass Abdel-Hameed1,
Tammy Naab2 and
Carolyn Broome1
1 Biochemistry & Molecular Biology,
2 Pathology, Howard University, 520 W Street N.W., Washington, DC, 20059-0001
ABSTRACT
Methylation of gene promoters decreases transcription and is an early event in cancer development. Quantitative multiplex methylation-specific PCR (QM-MSP) is a highly sensitive method that can simultaneously amplify several genes for quantitation. A statistically significant difference in the degree of methylation between the normal reduction mammoplasty samples and invasive carcinomas were found in all the genes studied; BRCA1 (P = 0.0261), Cyclin D2 (P=0.015), HIN1 (P = 0.0002), RAR ß (P = 0.0231), RASSF1A (P = 0.0388), and TWIST (P = 0.003). A cutoff (% M) for each gene was calculated such that 90% of normal breast tissues would be at or below the cutoff, values above the cutoffs were considered "positive" for hypermethylation. Among invasive carcinomas, 44% were positive for BRCA1, 60% for Cyclin D2, 81% for HIN1, 56% for RASSF1A, 50% for RARß, and 63% for TWIST. The sum of the percent methylation of the six genes was used as a cumulative methylation index (CMI). MDA-MB231 DNA is 100% methylated for all 6 genes, therefore has a CMI of 600 units. Normal tissues ranged from 23 to 47 units; carcinomas ranged from 56 to 296 units. The difference in the degree of methylation between normal and carcinomas was highly significant (P = 0.00003). These results suggest that the methylation profile of these six genes can be used as an early diagnostic biomarker for African American breast cancer in small samples. Army grant W81XWH-04-1-0586.
