The future of personalized cancer treatment: An entirely new direction for RNA...( In technology that promises to one d...),Health

In technology that promises to one day allow drug delivery to be tailored to an individual patient and a particular cancer tumor, researchers at the University of California, San Diego School of Medicine, have developed an efficient system for delivering siRNA into primary cells. The work will be published in the May 17 in the advance on-line edition of Nature Biotechnology.

"RNAi has an unbelievable potential to manage cancer and treat it," said Steven Dowdy, PhD, Howard Hughes Medical Institute Investigator and professor of cellular and molecular medicine at UC San Diego School of Medicine. "While there's still a long way to go, we have successfully developed a technology that allows for siRNA drug delivery into the entire population of cells, both primary and tumor-causing, without being toxic to the cells."

For many years, Dowdy has studied the cancer therapy potential of RNA inhibition which can be used to silence genes through short interfering, double-stranded RNA fragments called siRNAs. But delivery of siRNAs has proven difficult due to their size and negative electrical charge which prohibits them from readily entering cells.

A small section of protein called a peptide transduction domain (PTD) has the ability to permeate cell membranes. Dowdy and colleagues saw the potential for PTDs as a delivery mechanism for getting siRNAs into cancer cells. He and his team had previously generated more than 50 "fusion proteins" using PTDs linked to tumor-suppressor proteins.

"Simply adding the siRNAs to a PTD didn't work, because siRNAs are highly negatively charged, while PTDs are positively charged, which results in aggregation with no cellular delivery," Dowdy explained. The team solved the problem by making a PTD fusion protein with a double-stranded RNA-binding domain, termed PTD-DRBD, which masks the siRNA's negative charge. This allows the resultant fusion protein to enter the cell and deliver the siRNA i
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