HOUSTON - Even while being dragged to its destruction inside a cell, a cancer-promoting growth factor receptor fires away, sending signals that thwart the development of tumor-suppressing microRNAs (miRNAs) before it's dissolved, researchers reported in an early online publication at Nature.
Under conditions of oxygen starvation often encountered by tumors, the epidermal growth factor receptor (EGFR) gums up the cell's miRNA-processing machinery, an international team led by scientists at The University of Texas MD Anderson Cancer Center discovered.
"So when hypoxia stresses a cell, signaling by EGFR prevents immature miRNAs from growing up to fight cancer," said senior author Mien-Chie Hung, Ph.D., professor and chair of MD Anderson's Department of Molecular and Cellular Oncology and holder of the Ruth Legett Jones Distinguished Chair.
The group's findings point to a potential new prognostic marker for breast cancer, Hung noted, but also provide the first evidence of a growth factor signaling pathway regulating miRNA maturation.
"Inside of a cell, you have signal induction, in this case through EGFR, and you also have a protein complex that processes precursors into mature miRNA to perform a function. They didn't appear to talk to each other, it's as if one speaks English and the other Chinese," Hung said. "This is the first paper to show how they communicate."
The scientists established the relationship in cell line experiments, confirmed it in a mouse model and human breast cancer samples, then found that it reduced breast cancer patient survival in a review of 125 cases.
A new cancer-promoting role identified for EGFR
EGFR penetrates the cell membrane to receive signals from growth factors outside of the cell. After a growth factor binds to it, EGFR conveys the signal into the cell by attaching phosphate groups to other proteins, often acting as a molecular "on switch."<
|Contact: Scott Merville|
University of Texas M. D. Anderson Cancer Center