In a novel study, researchers from The University of Texas M. D. Anderson Cancer Centre have identified a gene that protects PTEN, a major tumor-suppressor in breast cancer.
They have found that the gene known as Rak helps protect and regulate PTEN, which also is important in several other types of cancer.
"We've clearly discovered the missing link that explains how Rak can stabilize PTEN protein to prevent breast cancer development," said lead author Shiaw-Yih Lin, Ph.D., an assistant professor in the Department of Systems Biology at M. D. Anderson.
"Our research explains why PTEN is defective in breast cancer and provides important clues for the development of effective therapy in Rak- or PTEN-defective breast cancers," Lin added.
The severity of PTEN irregularities strongly correlates with the tumor stage and grade. For example, complete loss of PTEN expression is found more frequently in metastatic cancer than in primary tumors.
During the study, the researchers analyzed cells from 42 breast cancers.
They found Rak can stabilize PTEN protein and function as a tumor suppressor gene to prevent breast cancer development.
"To further assess whether Rak is a bona fide breast tumor suppressor gene, we sought to determine if loss of Rak expression would transform normal mammary epithelial cells," Lin said.
"We injected control cells or cells in which Rak was compromised into the mammary glands of healthy mice and monitored tumor growth. Notably, all the mice injected with Rak-knockdown cells, but none of the mice injected with control cells, developed tumors," Lin added.
The study appears in Cancer Cell.