Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Deadly liver cancer may be triggered by cells changing identity, UCSF study shows

17.07.2012
A rare type of cancer thought to derive from cells in the bile ducts of the liver may actually develop when one type of liver cell morphs into a totally different type, a process scientists used to consider all but impossible.

UCSF researchers triggered this kind of cellular transformation—and caused tumors to form in mice—by activating just two genes. Their discovery suggests that drugs that are able to target those genes may provide a way to treat the deadly cancer, known as cholangiocarcinoma. It also shows, yet again, how the process of scientific discovery involves serendipity as well as skill.

The study appears as an advanced online publication July 16, 2012 in the Journal of Clinical Investigation and will appear later in the August print edition.

The two cell types, hepatocytes and biliary cells, exist side by side in the liver, but don't normally change their "stripes" -- their cellular function -- let alone turn into each other. Scientists have therefore assumed that hepatocellular carcinomas, the most common kind of liver cancer, start in the hepatocytes and that cholangiocarcinomas, the bile duct cancers, start in the biliary cells.

Hepatocytes, which form the bulk of the liver, "are very good at making other hepatocytes," said Holger Willenbring, PhD, an associate professor of surgery, a member of the Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research at UCSF, and a senior author of the study. "They can divide many times but are restricted in the progeny they produce. They either produce more hepatocytes or, if something goes wrong, can cause hepatocellular carcinomas."

The study started when Xin Chen, PhD, an assistant professor of bioengineering and therapeutic sciences and a senior author of the manuscript, tried to make something go wrong in the hepatocytes as a way to explore the origins of hepatocellular carcinoma. Chen and her group hoped to induce the cancer in mice by activating oncogenes, genes that trigger cancer.

Things did go awry in the hepatocytes -- but not in the way the researchers expected. In specific conditions, mice developed cholangiocarcinoma instead of hepatocellular carcinoma. "We were very surprised," Chen recalls. They asked, "How did that happen?"

The two scientists figured some of the genes they had activated might have reprogrammed the hepatocytes in a way that turned them into aberrant biliary cells, capable of forming tumors. Their chief suspects were two genes, NOTCH, which is known to be involved in the embryonic development of bile ducts, and AKT, which has been shown to play a role in many tumors.

The scientists used bits of bacterial DNA called plasmids as delivery vehicles to boost levels of NOTCH and AKT in the liver. Three-and-a-half weeks after injecting these plasmids into mice, small white growths appeared on the surface of their livers and, by five weeks, the tumors had spread through the liver. Now the scientists needed to trace the origins of these cancer cells.

Willenbring's lab had previously developed a method for labeling mouse hepatocytes so that they, and any cell they turned into, would glow. They put this "hepatocyte fate-tracing" system to work and were able to show that the cancerous cells that formed bile duct tumors had in fact started out as hepatocytes.

For many years, scientists had believed that development of cells proceeded in one direction, moving step-by-step from primordial stem cells to fully differentiated adult cells. In recent years, researchers have shown that, by turning on certain genes, mature cells can go back in time to become stem cells or even move sideways to become other kinds of adult cell.

"This highlights how readily one cell can be converted into another and how cancer can do it for you very efficiently," Willenbring said. "For us, it's fairly shocking. It only took two oncogenes and it all happened in a few weeks."

The findings also help explain another puzzle: why the incidence of bile duct cancer is higher in people with hepatitis. "Since hepatitis doesn't do anything to biliary cells that didn't quite make sense," Willenbring said

Now there's a new way to look at it, he suggests. As hepatocytes and their genomes become disarrayed by disease, Willenbring says, they may activate oncogenes in much the same way their experiment did, causing the cells to change identity and become cancerous.

Having shown that NOTCH and AKT are the triggers in this tumor-inducing process, Chen and her team are now hunting for therapies. Working with colleagues from Genentech Inc., they are testing antibodies that may blunt the activity of the genes and halt or reverse the growth of bile duct cancers in mice. "The preliminary results with the therapeutic antibodies are very encouraging," Chen says. If they find the right formula, they may have an answer for a currently untreatable cancer.

Biao Fan, Yann Malato, Diego F. Calvisi, Syed Naqvi, Nataliya Razumilava, Silvia Ribback, Gregory J. Gores, Frank Dombrowski and Matthias Evert contributed to the research.

Funding support came from the California Institute of Regenerative Medicine, National Institutes of Health, Deutsche Forschungsgemeinschaft and the China Scholarship Council.

UCSF is a leading university dedicated to promoting health worldwide through advanced biomedical research, graduate-level education in the life sciences and health professions, and excellence in patient care.

Follow UCSF
UCSF.edu | Facebook.com/ucsf | Twitter.com/ucsf | YouTube.com/ucsf

Jennifer O'Brien | EurekAlert!
Further information:
http://www.ucsf.edu

More articles from Studies and Analyses:

nachricht The importance of biodiversity in forests could increase due to climate change
17.11.2017 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig

nachricht Win-win strategies for climate and food security
02.10.2017 | International Institute for Applied Systems Analysis (IIASA)

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

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

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>