The study by researchers at The Ohio State University Comprehensive Cancer Center Arthur G. James Cancer Hospital and Richard J. Solove Research Institute examined how a chemical change known as methylation spreads from one region of a breast-cancer gene to a neighboring region in tumor cells taken from patients.
The findings provide insight into how the methylation process progresses until it inactivates genes such as tumor suppressor genes that otherwise help protect against cancer. The findings are published in the Oct. 1 issue of the journal Cancer Research.
"Methylation is as important as gene mutations and chromosomal damage in the cancer process," says principal investigator Tim Hui-Ming Huang, associate professor of human cancer genetics.
"Our findings suggest that the degree of methylation may correlate with the seriousness of the tumor. If that proves to be true, it would have important implications for cancer diagnosis and predicting a patient's prognosis."
Methylation is the addition of small chemical units known as methyl groups to DNA. Cells normally use methylation to inactivate unneeded genes during embryonic development and throughout life. Abnormal methylation, however, occurs in many types of cancers.
The investigators developed microarray technology to measure methylation levels along two regions of a gene known as RASSF1A, which becomes highly methylated in many kinds of cancer. Microarray technology allows researchers to measure changes in genes from many different tumors simultaneously.
The researchers examined the methylation profiles of RASSF1A genes taken from 37 primary breast tumors, seven breast-cancer cell lines and 10 samples of normal breast tissue.