Why does a normal cell possibly harboring genetic mutations in oncogene or tumor suppressor genes becomes malignant and develop a tumor is a subject of intense debate. Various theories have been proposed but their experimental test has been hampered by the unpredictable and improbable malignant transformation of single cells. Here using an optogenetic approach we permanently turn on an oncogene (KRASG12V) in a single cell of a zebrafish brain that, only in synergy with the transient co-activation of a reprogramming factor (VENTX/NANOG/OCT4), undergoes a deterministic malignant transition and robustly and reproducibly develops within 6 days into a full-blown tumor. The controlled way in which a single cell can thus be manipulated to give rise to cancer lends support to the "ground state theory of cancer initiation" through "short-range dispersal" of the first malignant cells preceding tumor growth.
Abstract In MeLiM minipigs, melanomas develop around birth, can metastasize, and have histopathologic characteristics similar to humans. Interestingly, MeLiM melanomas eventually regress. This favorable outcome raises the question of their malignancy, which we investigated. We clinically followed tens of tumors from onset to first signs of regression. Transcriptome analysis revealed an enrichment of all cancer hallmarks in melanomas, although no activating or suppressing somatic mutation were found in common driver genes. Analysis of tumor cell genomes revealed high mutation rates without UV signature. Canonical proliferative, survival and angiogenic pathways were detected in MeLiM tumor cells all along progression stages. Functionally, we show that MeLiM melanoma cells are capable to grow in immunocompromised mice, with serial passages and for a longer time than in MeLiM pigs. Pigs set in place an immune response during progression with dense infiltration by myeloid cells while melanoma cells are deficient in B2M expression. To conclude, our data on MeLiM melanomas reveal several malignancy characteristics. The combination of these features with the successful spontaneous regression of these tumors make it an outstanding model to study an efficient anti-tumor immune response.
Why does a normal cell possibly harboring genetic mutations in oncogene or tumor suppressor genes becomes malignant and develop a tumor is a subject of intense debate. Various theories have been proposed but their experimental test has been hampered by the unpredictable and improbable malignant transformation of single cells. Here using an optogenetic approach we permanently turn on an oncogene (KRASG12V) in a single cell of a zebrafish brain that, only in synergy with the transient co-activation of a reprogramming factor (VENTX/NANOG/OCT4), undergoes a deterministic malignant transition and robustly and reproducibly develops within 6 days into a full-blown tumor. The controlled way in which a single cell can thus be manipulated to give rise to cancer lends support to the “ground state theory of cancer initiation” through “short-range dispersal” of the first malignant cells preceding tumor growth.
The presence of specific antibodies against human polyomavirus 12, Saint Louis polyomavirus and New Jersey polyomavirus was investigated by using virus-like particle-based ELISAs with serum samples from 706 Italians aged 1- to 100-years-old. The findings indicate that these polyomaviruses circulate widely in humans, with peak seroprevalence, observed at adulthood, of 97.3%, 93.3%, 57.5%, for human polyomavirus 12, Saint Louis polyomavirus and New Jersey polyomavirus, respectively.
Tectona grandis (teak) and Vernonia amygdalina (bitter leaf) are plants used in traditional medicine in West Africa. In this study, we tested ethanolic and hydro-ethanolic extracts of bark and leaves of T. grandis and ethanolic extract of leaves of V. amygdalina for their inhibitory effect on Toxoplasma gondii, a protozoan parasite responsible for toxoplasmosis. Ethanolic extract of V. amygdalina leaves had proportional contents of phenols, tannins, flavonoids, and polysaccharides. This extract presented the highest efficacy against T. gondii, the lowest cytotoxicity to mammalian cells, but moderate anti-oxidant activity compared to other plant extracts. Ethanolic extract of T. grandis bark also had elevated anti-T. gondii activity, low cytotoxicity on mammalian cells, and one of the highest anti-oxidant activities. However, the phytochemical content of this extract was not very different from the hydro-ethanolic extract, which had no anti-T. gondii activity. In addition, ethanolic extract of V. amygdalina leaves, but not of T. grandis bark, significantly increased the production of TNF-α and NO by antigen-presenting cells. Both extracts had the tendency to decrease expression of major histocompatibility complex molecules at the surface of antigen-presenting cells, while they did not modulate the percentage of apoptotic cells. A study of signalling pathways would help to determine the mechanisms of action of these plant extracts.Les extraits de Tectona grandis et de Vernonia amygdalina ont des propriétés anti-Toxoplasma et pro-inflammatoires in vitro.Tectona grandis (teck) et Vernonia amygdalina sont des plantes utilisées dans la médecine traditionnelle en Afrique de l’Ouest. Dans cette étude, l’effet inhibiteur d’extraits éthanoliques et hydro-éthanoliques d’écorce et de feuilles de T. grandis et de l’extrait éthanolique des feuilles de V. amygdalina a été étudié sur Toxoplasma gondii, un parasite protozoaire responsable de la toxoplasmose. L’extrait éthanolique des feuilles de V. amygdalina avait des quantités équivalentes de phénols, tanins, flavonoïdes et polysaccharides. Cet extrait présentait la plus grande efficacité contre T. gondii, la plus faible cytotoxicité vis-à-vis de cellules de mammifères, mais une activité anti-oxydante moyenne comparée aux autres extraits de plantes. L’extrait éthanolique d’écorce de T. grandis avait aussi une activité anti-T. gondii élevée, une faible cytotoxicité vis-à-vis des cellules de mammifères et l’une des activités anti-oxydantes les plus élevées. Cependant, le contenu phytochimique de cet extrait n’était pas très différent de l’extrait hydro-éthanolique qui n’avait pas d’activité anti-T. gondii. De plus, l’extrait éthanolique des feuilles de V. amygdalina, mais pas de l’écorce de T. grandis, augmentait significativement la production de TNF-α et de NO par les cellules présentatrices d’antigènes. Les deux extraits avaient tendance à diminuer l’expression des molécules du complexe majeur d’histocompatibilité à la surface des cellules présentatrices d’antigènes alors qu’ils ne modulaient pas le pourcentage de cellules apoptotiques. L’étude des voies de signalisation permettrait de comprendre les mécanismes d’action de ces extraits de plantes.
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