A landmark study by Florida State University biologists, in collaboration with scientists in Britain, is the first to identify a life-or-death "cell competition" process in mammalian tissue that suppresses cancer by causing cancerous cells to kill themselves.
Central to their discovery was the researchers' identification of "Mahjong" –– a gene that can determine the winners of the competition through its close relationship with another powerful protein player. Lead author Yoichiro Tamori and Associate Professor Wu-Min Deng of Florida State and Yasuyuki Fujita of University College London named the newfound gene after the Chinese game of skill and luck.
The findings shed light on the critical interactions between cancerous cells and surrounding tissue, and confirm that those interactions occur not only in fruit fly models but also in mammalian cell cultures.
Tamori and team found that Mahjong binds to and interacts with the tumor suppressor gene "Lethal giant larvae" (Lgl). That bond allows Mahjong to influence the outcome of cell competition, because it is mutations in Lgl –– or in genes interacting with it –– that transform a normal cell into a malignant one, triggering the lethal showdown between neighboring healthy cells and cancerous ones."A better understanding of the ways that inherited or acquired mutations in key proteins lead to cell competition should help foster new therapies that increase the odds of victory for normal cells," said Tamori, a postdoctoral fellow in Florida State's Department of Biological Science.
The study began with a focus on Lgl, a gene that normally prevents the development of tumors by tightly controlling cell asymmetry and proliferation. To more fully understand its role in cell competition, the Florida State and University College London biologists looked at Lgl in both fruit flies and mammals. They knew that earlier studies of Lgl's structural qualities had concluded that it worked in tandem with other proteins. To try to identify its possible partners, the researchers used a technique that worked to trap both Lgl and any proteins bound to it.
They learned that Lgl had just one binding partner –– soon to be known as Mahjong.
"In addition to identifying Mahjong and its relationship with Lgl," said Deng, "we confirmed that both genes function in the same pathway ¬¬in both fruit flies and mammals to regulate cellular competitiveness."
To determine if a mutation would induce cell competition in fruit flies, the Florida State biologists modified fly larvae by deleting the Mahjong gene from subsets of the wing-tissue cells.
Then, using a fluorescent probe that can identify cells undergoing apoptosis (a form of programmed suicide), they saw that cell death was occurring in the Mahjong mutant cells that were adjacent to normal cells, but not in those surrounded by fellow Mahjong mutants.
"In competition with their normal neighbors," said Tamori, "cells without Mahjong were the losers."
After Tamori and Deng confirmed the role of Mahjong in fruit fly cell competition, their collaborators at University College London sought to induce competition in mammalian cells.
To replicate as closely as possible the occurrence of mutations caused by environmental factors, Fujita and his team engineered kidney cells whose copies of the Mahjong gene could be shut down by the antibiotic tetracycline. Before adding tetracycline, they mixed the engineered cells with normal ones and allowed them to grow and form tissue.
"When tetracycline was added to the tissue, the cells in which Mahjong had been shut down began to die, just as they had in the fruit fly," Tamori said.
"In the kidney cells, as in flies," he said, "apoptosis was only observed in Mahjong mutants when they were surrounded by normal cells. We now had a clear demonstration of cell competition in mammalian tissue, triggered by mutations in a key protein."
Next, the team sought to prevent apoptosis in cells that lacked Lgl or Mahjong by copying the remaining protein partner in larger-than-normal numbers.
"We learned that overexpressing Mahjong in Lgl-deficient cells, which typically self destruct, did in fact prevent apoptosis," Deng said. "But, in contrast, we found that overexpressing Lgl in Mahjong-deficient cells did not prevent cell suicide."
Funding for the study came from a five-year grant to Deng from the National Institutes of Health (NIH). A developmental and cell biologist at Florida State since 2004, Deng is recognized for research in the model organism Drosophila melanogaster (fruit fly) that has enhanced understanding of gene regulation and signaling pathways linked to cancer and other diseases.
Deng's NIH grant supported another recent study that also has advanced cancer research. In collaboration with scientists from the Johns Hopkins University School of Medicine, Deng and Florida State colleagues studying the "Hippo" tumor suppressor pathway identified an influential new gene there, which they named "Kibra." Their findings were published Feb. 16, 2010, in the journal Developmental Cell and discussed in the April 2010 issue of Nature Reviews Cancer.
Tamori and Deng of Florida State University and Fujita of University College London co-authored the PLoS Biology paper "Involvement of Lgl and Mahjong/VprBP in Cell Competition" with support from a team comprised of a postdoctoral fellow, graduate and undergraduate students, and a technician. From FSU, the team members were Ai-Guo Tian, Yi-Chun Huang, Nicholas Harrison and John Poulton. From UCL, they were Carl Uli Bialucha, Mihoko Kajita, Mark Norman, Kenzo Ivanovitch, Lena Disch and Tao Liu.
Yoichiro Tamori | EurekAlert!
Hunting pathogens at full force
22.03.2017 | Helmholtz-Zentrum für Infektionsforschung
A 155 carat diamond with 92 mm diameter
22.03.2017 | Universität Augsburg
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
22.03.2017 | Materials Sciences
22.03.2017 | Physics and Astronomy
22.03.2017 | Materials Sciences