Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

RNAi delivery system crosses blood-brain barrier to target brain cancer

01.06.2004


Researchers have combined novel molecular targeting technologies to deliver gene-silencing therapy specifically to tumor cells shielded by a normally impermeable obstacle, the blood brain barrier.



In the June 1 issue of the journal Clinical Cancer Research, William Pardridge, M.D., UCLA, reported that a delivery packet equipped with two specific antibodies first recognizes the transferrin receptor, a key protein portal in the blood brain barrier, and then gains entry into brain cancer cells with the second antibody targeting the human insulin receptor.

Using the antibody keys to traverse both the blood brain barrier and the tumor cell membrane, the delivery packets--called liposomes--deposit a genetically engineered non-viral plasmid in the brain cancer cells. The plasmid encodes a short hairpin RNA (shRNA) designed to interfere with the expression of the epidermal growth factor receptor, EGFR, a potent proponent of tumor cell proliferation. The use of shRNA to silence gene expression is RNA interference (RNAi) technology.


When treated with a weekly intravenous dose of Dr. Pardridge’s targeted therapeutic, mice with brain tumors survive almost twice as long compared to mice that do not receive the treatment.

"This is the first drug delivery system that demonstrates that by using RNA interference technology, you can prolong life threatened by cancer," said Dr. Pardridge, Professor of Medicine at UCLA. "By solving the delivery problem, powerful molecular tools and therapies such as RNA interference can be moved to clinical trials where they can be tested to see how much benefit the patient gets."

The delivery system designed by the Pardridge research team is much like a minute parcel with a primary delivery address, a forwarding delivery address, and a message that halts proliferation of the tumor cells.

Liposomes are the parcel. Composed of lipid, or fat, molecules that align to form an enclosed membrane much like a sealed envelope, the liposomes are constructed with thousands of molecular probes that recognize two specific proteins. The proteins are the addresses to which the liposome is targeted. One antibody that is engineered into the liposome recognizes only the transferrin receptor, a protein common to the blood brain barrier. By binding tightly to the transferrin receptor, the liposome gains entry to the chamber in which the brain is normally screened from pathogens, foreign proteins, and even small molecules.

Once inside the compartment that houses and protects the brain, a second set of liposome-embedded antibodies seeks out the human insulin receptor found in the membranes of brain cancer cells. The insulin receptor antibody latches on to the tumor’s insulin receptors. The liposome, and its contents, uses the insulin receptor to gain entry to the tumor cell.

Within the tumor cell, the plasmid payload is released from the liposome.

"This is the ’Trojan Horse’ element of the therapy," Dr. Pardridge said. The liposome acts as the hollowed horse; the plasmid is the Trojan warrior released inside the cell to combat the cancer.

The plasmid is constructed of genetic material designed to reproduce shRNA, which is then metabolized by a protein in the tumor cell called Dicer. Dicer produces the active RNAi molecule that complements a defined sequence from the EGFR gene RNA. When the tumor cell divides, the RNAi molecule is produced and binds to the message from the tumor cells’ pool of EGFR RNA. Binding of the RNAi therapeutic molecule to the cells’ innate RNA results in the silencing of the EGFR message. No EGFR protein is produced, and the gene is effectively inactivated.

Without its normal workload of EGFR proteins to encourage cell proliferation, the tumor growth is held in check.

The Pardridge group confirmed that the treatment strategy thwarted EGFR function in two ways. The EGFR is set into action when it binds a growth factor related to epidermal growth factor, a hormone growth factor that travels outside of cells in the blood. Activated EGFR normally induces a flow of calcium across tumor cell membranes. That calcium mobilization was minimized in the brain cancer cells treated with the targeted liposome packet.

Furthermore, activated EGFR induces DNA replication and cell proliferation. A radiolabeled DNA component, tritiated thymidine, is incorporated into newly synthesized DNA. By monitoring the level of radiation in the brain cancer cells, Dr. Pardridge noted minimized DNA replication, and hence, cellular proliferation, in the cancer cells that were treated with the immunoliposomes. Tumors in the treated mice had reduced EGFR content, and the mice showed an 88 percent increase in survival time.

The research leading to the Pardridge group’s design of a tandem-probed immunoliposome laden with RNAi technology was supported with funding from the Accelerated Brain Cancer Cure (ABC2), and the U.S. Government. ABC2 is a nonprofit foundation dedicated to discovery of research leading to cures for brain cancer. ABC2 was created by the late Dan Case, chairman of H.P. Morgan H&Q, and his brother Steve Case, the founder of AOL and the former chairman of AOL Time Warner.


Founded in 1907, the American Association for Cancer Research is a professional society of more than 22,000 laboratory, translational, and clinical scientists engaged in all areas of cancer research in the United States and in more than 60 other countries. AACR’s mission is to accelerate the prevention and cure of cancer through research, education, communication, and advocacy. Its principal activities include the publication of five major peer-reviewed scientific journals: Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; and Cancer Epidemiology, Biomarkers & Prevention. AACR’s Annual Meetings attract more than 15,000 participants who share new and significant discoveries in the cancer field. Specialty meetings, held throughout the year, focus on the latest developments in all areas of cancer research.

Russell Vanderboom | EurekAlert!
Further information:
http://www.aacr.org/

More articles from Health and Medicine:

nachricht 3D images of cancer cells in the body: Medical physicists from Halle present new method
16.05.2018 | Martin-Luther-Universität Halle-Wittenberg

nachricht Better equipped in the fight against lung cancer
16.05.2018 | Friedrich-Alexander-Universität Erlangen-Nürnberg

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

Im Focus: Dozens of binaries from Milky Way's globular clusters could be detectable by LISA

Next-generation gravitational wave detector in space will complement LIGO on Earth

The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...

Im Focus: Entangled atoms shine in unison

A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.

The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...

Im Focus: Computer-Designed Customized Regenerative Heart Valves

Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.

Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...

Im Focus: Light-induced superconductivity under high pressure

A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.

Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

 
Latest News

Supersonic waves may help electronics beat the heat

18.05.2018 | Power and Electrical Engineering

Keeping a Close Eye on Ice Loss

18.05.2018 | Information Technology

CrowdWater: An App for Flood Research

18.05.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>