The poor prognosis of brain tumors
Malignant Brain tumors are extremely difficult to treat. Prognosis is very poor in most patients diagnosed with brain tumors despite receiving all kinds of therapy. Glioblastoma, the most aggressive form of brain tumor has a survival duration of fewer than 3 months in people without any treatment and 12-15 months in patients who receive treatment. Their highly penetrative nature makes surgical resection impossible.
The mainstay therapy in brain tumor patients is surgical resection, chemotherapy, and radiotherapy. However, due to the difficult properties of the brain, treatment is complicated.
Due to the highly selective blood-brain barrier, only a few drugs can successfully penetrate into the brain cells to exert their effects. Additionally, the regenerative capacity of the brain is very limited making radiotherapy dangerous as radiation may damage healthy parts of the brain along with the cancer cells. Due to the complex structure and intricate design of the brain, surgery also carries significant risks of complications.
The Ideal treatment
A treatment that specifically targets tumor cells leaving healthy cells untouched would be the ideal treatment for all brain tumors. New research on mice may have achieved this exact feat. In the research, scientists created individualized tumor-targeting cells that hunted down brain tumor cells to reduce their size up to 2% to 5% of their original size. Scientists were able to create these tumor-homing cells in just 4 days. The strategy has only been studied on mice and is yet to be applied to human studies.
Brain tumors release a chemical signal that draws stem cells towards them. Scientists are using this unique feature to enable stem cells to detect tumor cells and treat them as a wound that requires healing. The stem cells can then be used as transporting tools to deliver oncolytic drugs directly to the tumor cells.
Why has this treatment not been widely used yet?
Although many researchers have already employed stem cells to deliver cancer-killing drugs in mice, it has not yet been experimented on human tumor cells. This is due to the difficulty in the extraction of neural stem cells. Currently, there are only three methods to extract neural stem cells and two of them are invasive. The methods include harvesting the stem cells from the patients, harvesting the stem cells from another person, or reprogramming adult cells genetically. In addition to the extraction difficulties, administering the stem cells also requires two steps, which carries the risk of the final cells becoming cancerous as well. Stem cells extracted from another person also have the risk of the immune response being triggered in the cancer patient.
Solving the Dilemma
The new research by Hingtgen’s group changed the older genetic reprogramming process by skipping a step. The group treated the skin cells with a combination of drugs to promote neural stem cell features, which proved to be successful.
The next issue was whether the reprogrammed cells could target the tumor cells specifically. “We were really holding our breath,” Hingtgen says. “The day we saw the cells crawling across the [Petri] dish toward the tumors, we knew we had something special.” The tumor-homing cells moved 500 microns—the same width as five human hairs—in 22 hours, and they could burrow into lab-grown glioblastomas.
The cells were then designed to administer tumor-eradicating therapy to the brain tumors in mice. Within a period of 24-28 days, the tumor size shrank by 20 to 50 times in the treated patients.
These results are yet to be replicated in humans and require extensive clinical trials.