Washington: Researchers have discovered that weeks of treatment with a repurposed FDA-approved drug halted the growth of - and ultimately left no detectable trace of - human brain tumour cells in mice.
The scientists targeted a mutation in the IDH1 gene first identified in human brain tumours called gliomas by a team of Johns Hopkins cancer researchers in 2008.
This mutation was found in 70 to 80 percent of lower-grade and progressive forms of the brain cancer. The change occurs within a single spot along a string of thousands of genetic coding letters, and is disruptive enough to keep the seemingly innocuous protein from playing its role in converting glucose into energy.
Instead, the mutation hijacks the protein to make a new molecule not normally found in the cell, which is apparently a linchpin in the process of forming and maintaining cancer cells.
The IDH1 gene, whose name stands for isocitrate dehydrogenase 1, produces an enzyme that regulates cell metabolism. Mutations, or changes in the DNA code, force the IDH1 gene to increase production of a flawed version of the enzyme.
The flawed enzyme produces large amounts of an entirely new molecule, called 2-hydroxyglutarate. This molecule is believed to cause groups of atoms called methyl groups to latch onto the DNA strand.
Alexandra Borodovsky, a graduate student in the Cellular and Molecular Medicine Program at the Johns Hopkins University School of Medicine who performed the experiments, Gregory J. Riggins, M.D., Ph.D., a professor of neurosurgery and oncology at the Johns Hopkins University School of Medicine and their colleagues - including Timothy A. Chan, M.D., Ph.D., of Memorial Sloan-Kettering Cancer Center in New York - thought that a drug that could strip those methyl groups might be able to reverse the cancer process in those cancers with IDH1 mutations. They chose 5-azacytidine, which is approved to treat a pre-leukemia condition called myelodysplastic syndrome and is being tested on lung and other cancers at Johns Hopkins and elsewhere.
Once the tumours grew, the researchers injected the mice with 5-azacytidine for 14 weeks and saw a dramatic reduction in growth and what appeared to be complete regression. Then they withdrew therapy. Seven weeks later, the tumours had not regrown.
The study has been published in open-access journal Oncotarget.