A small slice of RNA inhibits prostate cancer metastasis by suppressing a surface protein commonly found on prostate cancer stem cells. A research team led by scientists at The University of Texas MD Anderson Cancer Center reported today in an advance online publication at Nature Medicine.
"Our findings are the first to profile a microRNA expression pattern in prostate cancer stem cells and also establish a strong rationale for developing the microRNA miR-34a as a new treatment option for prostate cancer," said senior author Dean Tang, Ph.D., professor in MD Anderson's Department of Molecular Carcinogenesis.
MicroRNAs, or miRNAs, are short, single-stranded bits of RNA that regulate the messenger RNA expressed by genes to create a protein.
Cancer stem cells are capable of self-renewal, have enhanced tumor-initiating ability and are generally more resistant to treatment than other cancer cells. They are associated with tumor recurrence and metastasis, the lethal spreading of cancer to other organs. These capacities are more prevalent in cancer cells that feature a specific cell surface protein called CD44, Tang said.
"CD44 has long been linked to promotion of tumor development and, especially, to cancer metastasis," Tang said. "Many cancer stem cells overexpress this surface adhesion molecule. Another significant finding from our study is identifying CD44 itself as a direct and functional target of miR-34a."
MicroRNA goes up, CD44 and cancer stem cells fall
In a series of lab experiments with cell lines, human xenograft tumors in mice and primary human prostate cancer samples, the researchers demonstrated that miR-34a inhibits prostate cancer stem cells by suppressing CD44.
miR-34a is greatly reduced in prostate cancer cells that express high levels of CD44 on the cell surface. In 18 human prostate tumors, the microRNA was expressed at 25 to 70 percent of the levels found in cells without CD44.
Prostate tumors in mice that also received miR-34a treatment were one third to half the average size of those in control group mice.
In CD44-positive prostate cancer cell lines, treatment with miR-34a resulted in greatly reduced tumor incidence. Most dramatically, in one cell line, tumor regeneration was blocked in all 10 treated animals, while tumors formed in all 10 animals treated with the control miRNAs.
Many characteristics of cancer stem cells – formation of self-renewing cells, clonal growth capacity and formation of spheres – were suppressed when miR-34a was overexpressed in prostate cancer cell lines.
Most significantly, intravenous treatment of tumor-bearing mice with synthetic miR-34a reduced tumor burden by half in one tumor type. It also steeply reduced lung metastases in another tumor type, resulting in increased animal survival.
Interestingly, the researchers observed a consistent, inverse relationship between miR-34a levels and CD44, the surface marker used to enrich prostate cancer stem cells. For example, the CD44 protein and CD44-expressing cancer cells were reduced in tumors treated with the microRNA. Tumors with miR-34a blocked had higher levels of CD44 protein and messenger RNA.
Finally, knocking down CD44 with a short hairpin RNA produced the same results as treating cells with miR-34a did – reduced tumor development, tumor burden and metastases.
"There are many companies developing microRNA-based drugs," Tang said. "Delivery of miRNAs is a challenge, but the field is moving fast through the preclinical stage."
Scientists from Austin-based Mirna Therapeutics collaborated on the study. Mirna has eight microRNAs in preclinical development, including miR-34a.
The project was funded in part by grants from the National Cancer Institute and the National Institute of Environmental Health Science, the U.S. Department of Defense and the Elsa Pardee Foundation.
Co-authors were first author Can Liu, Bigang Liu, M.D., Xin Chen, Tammy Calhoun-Davis, Hangwen Li, Ph.D., Hong Yan, Ph.D., Collene Jeter, Ph.D., and Sofia Honorio, Ph.D., all of MD Anderson's Department of Molecular Carcinogenesis at the Science Park in Smithville, Texas; Can Liu and Xin Chen are also students in The University of Texas Graduate School of Biomedical Sciences at Houston, jointly operated by MD Anderson and The University of Texas Health Science Center at Houston; Lubna Patrawala, Ph.D., Kevin Kelnar, Jason Wiggins, Andreas Bader, Ph.D., and David Brown, Ph.D., all of Mirna Therapeutics, Inc. and Randy Fagin, M.D., of The Hospital at Westlake, Austin, Texas.
About MD Anderson
The University of Texas MD Anderson Cancer Center in Houston ranks as one of the world's most respected centers focused on cancer patient care, research, education and prevention. MD Anderson is one of only 40 comprehensive cancer centers designated by the National Cancer Institute. For seven of the past nine years, including 2010, MD Anderson has ranked No. 1 in cancer care in "America's Best Hospitals," a survey published annually in U.S. News & World Report. Get MD Anderson News Via RSS Follow MD Anderson News on Twitter
Scott Merville | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
19.07.2018 | Materials Sciences