World's First RNA Aptamer Could Be Key to Eradicating Cancer

Medical scientists in Australia have created the world's first cancer stem cell-targeting chemical missile, putting them a step closer to creating a medical "smart bomb” that would seek out and destroy the root of cancer cells.

The researchers, from Deakin University (Geelong, VIC, Australia), have worked with scientists in India and Australia to create the world's first RNA aptamer, a chemical antibody that acts like a guided missile to seek out and bind only to cancer stem cells. The aptamer has the potential to deliver drugs directly to the stem cells (the root of cancer cells) and to be used to develop a more effective cancer imaging system for early detection of the disease. Their discoveries have been published online February 1, 2011, in the international cancer research journal Cancer Science.

The director of Deakin Medical School's Nanomedicine Program, Prof. Wei Duan, reported that the development of the aptamer had huge implications for the way cancer is detected and treated. "Despite technological and medical advances, the survival rates for many cancers remain poor, due partly to the inability to detect cancer early and then provide targeted treatment,” Prof. Duan said. "Current cancer treatments destroy the cells that form the bulk of the tumor, but are largely ineffective against the root of the cancer, the cancer stem cells. This suggests that in order to provide a cure for cancer we must accurately detect and eliminate the cancer stem cells.”

The aptamer is the first part of the medical smart bomb the researchers have been developing. "What we have created is the guided missile part of the smart bomb,” Prof. Duan explained. "The aptamer acts like a guided missile, targeting the tumor and binding to the root of the cancer. The aim now is to combine the aptamer with the bomb [a microscopic fat particle] that can carry anticancer drugs or diagnostic imaging agents directly to the cancer stem cells, creating the ultimate medical smart bomb.”

Prof. Duan noted that the medical smart bomb opened up exciting possibilities for detection and treatment of cancer. "The cancer stem cell-targeting missile and the smart bomb could revolutionize the way cancer is diagnosed,” he explained. "The minute size of the aptamer means it could locate cancer cells in their very early stages. Attaching radioactive compounds to the aptamer could lead to the development of sensitive diagnostic scans for earlier detection, more accurate pinpointing of the location of cancer, better prediction of the chance of cure, and improved monitoring of the response to treatment. More accurate identification of the type of cancer present would lead to more personalized treatment that is more successful and cost-effective. This could ultimately lead to better cancer survival rates and greatly improved quality of life for patients.”

There are two parts to the project being undertaken by the Deakin and Indian scientists. The first is building the guided missile (aptamer). The aptamer is a chemical antibody, much smaller, less expensive, and easier to make than traditional antibodies, designed to bind specifically to cancer cells. It has been created to effectively penetrate a tumor and specifically target cancer stem cells. This missile will carry the bomb; the second part of the drug delivery system.

The bomb will be a very smart lipid, or fat particle that will remain stable in the body, i.e., it will not break down. This particle will carry the anticancer agent as well as anticancer genes. When combined, the smart bomb will be injected into the body and target the cancer cell. It will then enter the cell through an endosome route--a small pathway within the cell. Once inside the cell, it will very quickly release its contents and kill the whole cancer cell.

A novel part of the system being developed is that the bomb is very stable outside of the cancer cell, but once inside it will very rapidly release its contents and destroy the cancer cell from within. This system is comprised of components that are very human-compatible and human-degradable--it is not toxic to other cells in the body and would cause very limited side effects.

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