"These findings support the notion that variations in the genetic sequence of mitochondrial DNA are underappreciated factors in breast carcinogenesis," said Jeffrey Canter, M.D., M.P.H., of the Center for Human Genetics Research at Vanderbilt University, Nashville, Tenn.
The mitochondria, located outside the nucleus, are the cell's energy-producing factories. Unlike chromosomal DNA, the mitochondrial DNA is passed to offspring exclusively from the mother and carries important information necessary for the production of adenosine triphosphate, ATP, the energy source for cellular function.
In this study, the researchers focused on a specific variation (G10398A) in a mitochondrial gene called ND3, which serves as the blueprint for an important component of an enzyme called NADH dehydrogenase. In its changed state, however, an adenine is substituted for a guanine in the DNA structure, resulting in the enzyme containing the amino acid threonine instead of an alanine.
The clinical implication of this seemingly trivial alteration is profound. Among the greater population of humans, carriers of 10398A appear to be at higher risk for Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis (Lou Gehrig's disease), and other neurological disorders.
Canter and colleagues determined that the errant allele is associated with a significantly higher risk for breast cancer among African-American women who carry 10398A, but has no apparent implications for breast cancer in white women. A much greater proportion of the white female population, 80 percent, already carries the 10398A version of the NADH dehydrogenase gene than the five percent of b
Contact: Russell Vanderboom, Ph.D.
American Association for Cancer Research