Next, turning to cancerous tissue outside of the reproductive system, in this case breast tissue, the team determined, to their surprise, that the expression of the genes was active there, too.
"We thought this was going to be a phenomenon unique to germ cell tumors," says the senior author of the study, Amander Clark, PhD, assistant research geneticist in the laboratory of co-author Renee Reijo Pera, PhD, associate professor of obstetrics, gynecology and reproductive sciences and co-director of the UCSF Human Embryonic Stem Cell Center.
"This is the first indication that these genes are markers of breast cancer. The finding might lead to information about where breast cancers come from," Clark adds. "Are they derived from an original stem cell population, one that is expressing these genes, or do the cells in the tumor represent normal cells that have reverted to a more embryonic state that would express these genes?"
The suggestion that embryonic stem cell genes play a role in some cancers is not surprising. Embryonic stem cells, which emerge in the first five to seven days of the embryo's development, undergo a series of steps in which they selectively "turn on," or "express," genes that cause the cells progressively to assume the characteristics of a particular cell type, such as that of the skin, heart or brain. Cancers, meanwhile, develop when particular genes that regulate cell growth become misregulated, leading a cell to begin proliferating excessively. Misregulated embryonic stem cell genes, scientists have reasoned, could cause or advance cancer.
Substantial evidence already suggests, in fact, that genes in adult stem cells ?which reside in many tissues of the body ?cause some leukemias, and that they may cause gliomas, the most common form of brain tumor (UCSF - Nature, Feb. 19, 2004 ; UCSF - New England Journal of Medicine, Aug. 25, 2005).
The current study evolved from
Source:University of California - San Francisco