The strategy is based on the fact that both ovarian and pancreatic cancer cells significantly over-express a protein found on the cell membrane, called mesothelin. The function of that molecule is unknown, but it is found in the majority of pancreatic tumors and ovarian cancer tumors. Other solid tumors also express mesothelin, but not at such a high rate.
"We don't know completely why cancer cells repeatedly turn on mesothelin genes to produce these membrane proteins, but it gives us a way to fool the cell and hijack its machinery, to trick it into making other more potent genes that will be detrimental to the cancer cells," Brody says.
To do that, the researchers devised an agent that consists of a bit of mesothelin DNA connected to the gene that produces the toxin from diphtheria, a highly contagious and potentially deadly bacteria, which is now controlled through childhood DPT vaccination. "Naked" DNA is then coated in a polymer to form nanoparticles that are taken up by the cancer cells.
Inside the cells, the agent performs its trickery. The nanoparticles biodegrade and the cell machinery senses genetic material from mesothelin. It activates the diphtheria toxin gene, which then turns on production of the toxin which allows the toxin to then do its work on the cancer cells, Brody says. Within 24 hours of delivery, the toxin disrupted production of protein machinery by over 95 percent, and within six days, a number of cancer cells die or are arrested.
"The cancer thinks it is turning on mesothelin and once it gets started reading that genetic code, it can't stop," he says. "So it will read the bacteria's DNA and produce the to
|Contact: Ed Federico|
Thomas Jefferson University