Researchers at the UT Southwestern Medical Centre, in two preclinical studies, found an experimental drug tested against breast and lung cancer shows assurance in fighting the brain and prostate cancer. The study on glioblastoma appears in the January issue of Clinical Cancer Research. The prostate cancer study is available online in the International Journal of Cancer.
According to the researchers, the drug’s action observed in isolated human cells and rodents in trials were encouraging because they attacked not only the bulk of the tumor cells, but also the rare cancer stem cells that are believed to be responsible for most of the cancer growth.
In the current study on glioblastoma performed in mice, the drug has also crossed from the bloodstream into the brain, which is especially important because many drugs are not able to cross the blood brain barrier. The study mainly focused on telomeres, a region of repetitive DNA at the end of a chromosome, which protects the end of the chromosome from deterioration. The telomeres contain condensed DNA material that gives stability to the chromosomes As long as telomeres are longer than a certain minimum length, a cell can keep dividing. But telomeres shorten with each cell division, so a cell stops dividing once the telomeres are whittled down to that minimum. Telomerase is an enzyme that adds specific DNA sequence repeats(“TTAGGG” in vertebrates) to the 3’end of DNA strands in the telomere regions, which are found at the ends of eukaryotic chromosomes. The telomerase is a reverse transcriptase carries its own RNA molecule, and is used as a template when it elongates telomeres, that are shortened after each replication cycle. In cancer cells, the telomerase enzyme keeps rebuilding the telomeres, so the cells never be given the signal to halt dividing.
Imetelstat or GRN163L is a drug that blocks telomerase, and is already in clinical trials as a potential treatment for breast and lung cancer. The researchers focused on cells called tumor-initiating cells. Some researchers believe that tumors contain a small subset of initiating cells – or cancer stem cells – that are able to initiate and drive tumors and that are often resistant to radiation therapy and chemotherapy.