A team of Catalan researchers has discovered that the forces exerted by tumor cells to spread transcend the laws of physics as currently formulated. In a
study published in the journal Nature Physics, a team led by
Xavier Trepat, ICREA researcher at the Institute for Bioengineering of Catalonia (IBEC) and
Jaume Casademunt, professor of physics at the University of Barcelona (UB), has unveiled the forces exerted by tumor cells to spread. This discovery is driven by the
"la Caixa" Banking Foundation.The researchers placed breast tumor cells on a collagen-rich surface and observed how they expanded.
The technology developed by Trepat's group allowed them to measure the physical forces exerted by cells during this process, something that had not been achieved until now. With this method, they discovered that tumor expansion depends on a competition between forces: cells grab onto each other, staying united, and at the same time, they grab onto their environment to escape. Depending on which force predominates, the tumor will maintain a spherical shape or spread completely over the surface.
"It is a process very similar to what happens when we put a drop of water on a surface. On some surfaces, the drop will spread completely, as happens on a tile, while on other surfaces it will remain almost spherical, as happens on the waterproof fabric of an umbrella"explains Carlos Pérez, a researcher at IBEC, a "la Caixa" fellow and first author of the article
Set of breast cancer cells adhered to a collagen-rich surface. The actin cytoskeleton can be observed in green, coated with active myosin (ppMLC) in red, and cell-cell junctions (E-cadherin) in blue. Despite the similarities found between tumors and everyday liquids, the physics of both phenomena is very different. "The wetting of surfaces is a central problem of classical physics that we understand very well. However, tumors seem to be governed by very different laws," says Ricard Alert, a UB researcher, "la Caixa" fellow and co-author of the article. Unlike passive fluids, cells are capable of generating forces and moving on their own. This turns biological tissues into active fluids and, in particular, tumors into active droplets. Thus, understanding the expansion of tumors on a surface has required the development of a new physical theory that researchers have called "active wetting."
"When we think about states of matter, we usually think about solids, liquids, or gases. Our results and those of other laboratories indicate that living cells do not fit into this scheme and behave like another form of matter, which we call active matter," says Jaume Casademunt. When a tumor appears, cells accumulate mutations and their mechanical properties change. Generally, tumor cells lose connections between them and gain connections with their environment. As the tumor grows, the environment itself is also modified, increasing its amount of collagen and its rigidity. "Our experiments reveal that these changes are sufficient to unbalance the forces of a tumor, causing cells to begin to spread through their environment," explains Xavier Trepat.
This discovery highlights the importance of physical forces in metastasis, opening the door to developing therapies to alter the mechanics of tumors as a possible treatment.
Set of breast cancer cells beginning to detach from a surface to form a spherical aggregate. In red we observe the actin cytoskeleton stretching the adhesions to the substrate (paxillin), marked in green. The study has been funded by MINECO, the Generalitat de Catalunya, the European Research Council (ERC), the European Commission (MECHANO-CONTROL), CIBER-BBN, and Obra Social "La Caixa".
Referenced article:Carlos Pérez-González, Ricard Alert, Carles Blanch-Mercader, Manuel Gómez-González, Tomasz Kolodziej, Elsa Bazellieres, Jaume Casademunt, Xavier Trepat (2018).
Active wetting of epithelial tissues.
Nature PhysicsEl presidente de la República, Gabriel Boric, se refirió este lunes a la conmemoración de los 50 años del golpe de Estado, que se cumplirá el próximo 11 de septiembre, y a la polémica que se ha generado en torno a la fecha.
En ese contexto, el Mandatario hizo un llamado a “no empatar las responsabilidades” y a “no falsear la historia”.
“No es aceptable que se falsee la historia, que se relativicen o se justifiquen violaciones a los derechos humanos, o que se empaten las responsabilidades entre quienes fueron víctimas y victimarios”, dijo Boric en un acto en el Palacio de La Moneda.
El jefe de Estado también se refirió a la propuesta de algunos sectores de la oposición de firmar una declaración conjunta con el oficialismo, en la que se condene el golpe de Estado y se valore la democracia.
Al respecto, Boric señaló que “no es el momento de buscar acuerdos mínimos, sino de avanzar en la construcción de una memoria compartida que nos permita mirar el futuro con esperanza”.
“No se trata de imponer una verdad oficial, sino de reconocer los hechos tal como ocurrieron, de condenar las violaciones a los derechos humanos y de valorar la democracia como el único camino para resolver nuestras diferencias”, agregó.
El Presidente Boric también hizo un llamado a la unidad y a la reflexión, y a “no caer en la tentación de la polarización y la división”.
“Chile es un país que ha sabido levantarse de sus tragedias, y estoy seguro de que esta vez no será la excepción”, concluyó.