Newly identified mutations in a gene that makes cells immortal—the TERT promoter gene—appear to play a role in several types of cancer, including three of the most common types of brain tumors, according to the results of a study published in the journal Proceedings of the National Academy of Sciences.
Under normal conditions, cell reproduction is carefully controlled by the body. Without getting too technical, an important component of cell reproduction are telomeres, which are sort of like “end tabs” on cells. As normal cells divide, the telomeres gradually grow shorter until they become so short that the cell stops dividing and dies. This process relies on an enzyme called telomerase, which is sort of like a growth factor that temporarily maintains the length of the telomeres and enables the cell to continue reproducing.
Cancer, though, is characterized by the uncontrolled growth of cells. While normal cells eventually peter out and die, cancer cells rapidly divide and proliferate. This new study may provide insight into this process.
The TERT promoter gene basically controls the instructions for making the telomerase enzyme. When this gene is mutated, the telomeres never shorten—which means the cells can divide and replicate forever. A mutation of the TERT promoter gene has been implicated in cancer.
Researchers from the Duke Cancer Institute analyzed more than 1,200 tumors across 60 types of cancer and identified nine tumor types that are highly associated with mutations of the TERT promoter gene: melanomas, liposarcomas, hepatocellular carcinomas (liver cancer), transitional cell carcinomas of the urinary tract, squamous cell carcinomas of the tongue, medulloblastomas, and three subtypes of gliomas, including 83 percent of primary glioblastomas. What do these cancers have in common? They originate in tissues with relatively low rates of cell renewal—indicating that they might require the mutation of the TERT promoter gene to trigger the abnormal production of telomerase.
In contrast, the researchers found almost no TERT promoter mutations in many of the major cancer types, including breast and prostate cancer—indicating that an unknown factor is causing the telomeres to elongate and promote cell immortality in those diseases. However, they noted that the results in brain tumors were notable. In fact, this is the most frequent genetic mutation yet identified for primary glioblastoma, a deadly type of brain tumor.
The researchers referred to it as a major discovery in brain tumors. They suggest that TERT mutations could provide a biomarker that may be useful in detecting urinary tract and liver cancer and aid in the classification and prognostication of brain tumors. What’s more, the discovery provides new targets for drug development.
Killela PJ, Reitman ZJ, Jiao Y, et al. TERT promoter mutations occur frequently in gliomas and a subset of tumors derived from cells with low rates of self-renewal. Proceedings of the National Academy of Sciences of the United States of America. 2013; 110(15): 6021-6026.