Blocking the activity of this "death receptor" can stop and even reverse the growth of tumors in human tissue culture and mice, scientists from the University of Chicago and Northwestern University Feinberg School of Medicine report in the May 27, 2010, issue of the journal Nature. This unexpected inhibition suggests a promising new strategy for cancer therapy.
Bloquer l'activité de ce récepteur de la mort peut stopper et même faire regresser la croissance des tumeurs dans des tissus humains en culture et chez les souris. Cette inhibition inatendue suggère une thérapie prometeuse pour le cancer.Cell self-destruction, known as apoptosis, helps the body eliminate unwanted cells. Under normal circumstances, when the death receptor called CD95 is activated by specific proteins, the process of apoptosis is triggered. This cell suicide is an important process for immune function and to prevent the formation of uncontrolled, cancerous cell growth.
L'auto-destruction de la cellule, connue sous le nom d'apoptose aide le corps à éliminer les cellules non-voulues. Dans des circonstances normales, quand le récepteur de la mort appelé CD95 est activé par des protéine spécifiques à cette fonction, le processus d'apoptose est enclanchée. Ce suicide cellulaire est un processus important pour la fonction immunitaire et pour prévenir la formation incontrolée de cellules cancéreuses.Scientists have long speculated that the loss of "death receptors" may be an early step in the formation of tumors. However, many cancers continue to express high levels of CD95, even as the cells rapidly grow and proliferate.
Les scinetifiques ont longtemps spéculer que la perte du "récepteur de la mort" pourrait être une étape importante dans la formation de tumeurs. Toutefois, plusieurs cancers continuent d'exprimer de hauts niveaux de CD95 même si les cellules croissent rapidement et prolifèrent."These data raised the intriguing possibility that CD95 could actually promote the growth of tumors," said lead author Marcus Peter, PhD, professor of hematology/oncology at Feinberg and a member of the Robert H. Lurie Comprehensive Cancer Center of Northwestern University. "The most apoptosis-sensitive cells in vitro are all cancer cells. But how are they so apoptosis-sensitive and yet don't die?"
"These facts," notes Peter, "have been widely ignored."
Ces données indiquent la possibilité que CD95 pourrait contribuer à promouvoir la croissance des tumeurs. Les cellules les plus sensibles à l'apoptose in vitro sont les cellules cancéreuses mais comment font-elles en étant si sensibles à l'apoptose et contineur à vivre ? Ces faits ont ét largement ignorer.The team studied the role of CD95 in tumors using several human cancer cell lines, liver cancer mouse models, and models of ovarian cancer (from the laboratory of Ernst Lengyel, MD, PhD, Associate Professor in the Section of Gynecologic Oncology at the University of Chicago Medical Center).
L'équipe a étudié le rôle de CD95 dans les tumeurs en utilisant plusieurs cellules cancéreuses provenant de
de souris ou de modèles d'
.
Selectively deleting or reducing CD95 in these tumors dramatically slowed cell growth and, in some cases, actually killed the cells. When researchers reduced the activator for CD95 in the cancer cell lines, the effect was even more dramatic. The tumors stopped growing; some of them even died.
"This is a paradigm-shifting discovery," Lengyel said. "For 20 years, scientists have tried to use CD95 to kill tumors, but what we showed is that it is actually promoting tumor growth."
Effacer ou réduire le cd95 dans ces tumeurs réduit beaucoup la croissance de la cellule et dans quelques cas les fait mourir. Quand les chercheurs ont réduit l'activateur de CD95 dans les cellules, l,effet a été encore plus grand. Les tumeurs arrêtaient de croitre et quelques unes mouraient. Ceci change le paradigme. Depuis 20 ans, les scientifiques essayaient de se servir de CD95 pour tuer les cellules cancéreuses mais ce que nous avons trouver c'est que ça promeut plutôt la croissance du cancer.Downstream targets of CD95 essential for cell growth, such as JNK, c-Fos and Egr1, also decreased their activity when the "death receptor" was blocked. Furthermore, treating cancer cells with JNK inhibitors caused cells to stop growing, the researchers discovered.
Des cibles plus basses dans la façon dont les molécules interviennent comme JNK, c-fos et Egr1 décroissent aussi leur activité lorsque le récepteur de la mort est bloqué. De plus, traiter les cellules cancéreuses avec des inhibiteurs de JNK fait que les cellules arrêtent de croitre Further research will probe how and when the cells decide to switch the function of CD95 from "death" to "growth." JNK, as a downstream target of CD95, may be critical for that switch, as it has both pro-death and pro-growth functions in different concentrations.
Des étude splus poussées vont chercher comment et quand les cellules décident de switcher la fonction de CD95 de "mort" à "croissance" , JNK pourrait être important pour cela parce qu'il a les deux fonctions pro-death et pro-croissance selon la concentration."Every cancer cell maintains the level of receptor that is just sufficient for it to grow," Peter said. "As with anything else in nature, it's always in the doses. Sun is important because it helps you get vitamin D, but you don't want to stay in the sun too long."
A drug that blocks the CD95 ligand, a molecule that activates CD95, is already being tested in a phase II clinical trial. Though originally developed to stop the death of cells affected by degenerative diseases and AIDS, the drug may also be effective in killing tumor cells, this research suggests.
Clinical studies hope to test an inhibitor of the CD95 ligand in combination with chemotherapy. Chemotherapy can induce a stress response during which the concentration of CD95 ligand increases, which may further promote the growth of tumors.
"This will be a big translational project, and it is years away from coming to the clinic," Lengyel said. "But there are two ways that it might be used to treat patients: either using a soluble receptor that will sweep away the ligand before it binds cells and promotes growth, or by using an antibody against this ligand to block its activity."
This will also shift how scientists understand the role of CD95 in health and disease, said Douglas R. Green, PhD, Chair of Immunology, of St. Jude's Children's Research Hospital in an accompanying "News & Views" article.
"A general role for autocrine CD95 signalling in promoting cancer is a stunning revelation that goes against many of the prevailing notions of what this receptor does," Green said. "There is our realization that this 'wolf,' this potentially vital tumour-promoting mechanism, has been there all along, disguised as a mechanism of cell death."
Un rôle général de CD95 comme promouvant le cancer esst une étonnante révélation qui va contre plusieurs notions qui ont prévalu jusqu'à maintenant sur ce que fait ce récepteur jusqu'à présent. C'est notre réalisation de démasquer ce loup, ce mécanisme vital promouvant le cancer et qui a été là tout le temps déguisé en mécanisme pour tuer les cellules cancéreuses.