Ever since the discovery of a technique for isolating and growing human embryonic stem cells or ES cells in culture, they have emerged as an exciting possibility for developing superior systems to study the processes of disease and to replace cells and tissues ravaged by disease or injury.
In a paper published in Science a Memorial Sloan Kettering team recently reported that human ES cells had been used to create the first-ever genetically engineered model of cancer. This breakthrough has raised hopes of treatment for Pontine Glioma, a rare pediatric brain tumor called diffuse intrinsic (DIPG).
Senior study author and neurosurgeon Viviane Tabar said that “sequencing studies had yielded clues about some of the genetic mutations seen in these aggressive, incurable tumors. But there was no understanding of how these mutations lead to cancer. ” The decision to use ES cells to create a DIPG model was to “decipher the mechanisms of tumor formation.”
Among the reasons that make ES cells so exciting is their pluripotence, or their ability to develop into almost any cell type in the body. For years Dr. Tabar has focused on studying the processes by which ES cells may be induced to form different types of brain cells.
In the current study the first step was to try and get them to form a type of brain stem cells present in young children. The investigators then introduced the cancer-causing genes that are expressed in DIPG into the brain stem cells. When injected into the brain stems of mice, these cells formed tumors that exhibited many of the features of human DIPG.
“On the molecular level, the cells we created resembled brain tumors from patients,” Dr. Tabar explains. “Once they began growing in the mice, we could use them to test drugs that could potentially kill cancer cells in patients.” Their search for a drug that could kill the DIPG cells without harming the healthy brain stem cells led them to a compound, called menin inhibitor-2 (MI-2), a tumor suppressing protein that normally prevents cancer growth.
After the compound proved effective in significantly shrinking the tumour in mice they then tried it on tumor cells that had been removed from human patients. This experiment proved that the drug could potentially be effective against the human disease.
With the work showing that an ES-based system for cancer modeling may be significantly superior to tumor cell cultures and earlier types of mouse models, it offers hope for a potential therapy against DIPG, a disease that has defied hundreds of other drugs and carries a very short life expectancy.