Direct interaction of TrkA/CD44v3 is essential for NGF-promoted aggressiveness of breast cancer cells

Background CD44 is a multifunctional membrane glycoprotein. Through its heparan sulfate chain, CD44 presents growth factors to their receptors. We have shown that CD44 and Tropomyosin kinase A (TrkA) form a complex following nerve growth factor (NGF) induction. Our study aimed to understand how CD44 and TrkA interact and the consequences of inhibiting this interaction regarding the pro-tumoral effect of NGF in breast cancer. Methods After determining which CD44 isoforms (variants) are involved in forming the TrkA/CD44 complex using proximity ligation assays, we investigated the molecular determinants of this interaction. By molecular modeling, we isolated the amino acids involved and confirmed their involvement using mutations. A CD44v3 mimetic peptide was then synthesized to block the TrkA/CD44v3 interaction. The effects of this peptide on the growth, migration and invasion of xenografted triple-negative breast cancer cells were assessed. Finally, we investigated the correlations between the expression of the TrkA/CD44v3 complex in tumors and histo-pronostic parameters. Results We demonstrated that isoform v3 (CD44v3), but not v6, binds to TrkA in response to NGF stimulation. The final 10 amino acids of exon v3 and the TrkA H112 residue are necessary for the association of CD44v3 with TrkA. Functionally, the CD44v3 mimetic peptide impairs not only NGF-induced RhoA activation, clonogenicity, and migration/invasion of breast cancer cells in vitro but also tumor growth and metastasis in a xenograft mouse model. We also detected TrkA/CD44v3 only in cancerous cells, not in normal adjacent tissues. Conclusion Collectively, our results suggest that blocking the CD44v3/TrkA interaction can be a new therapeutic option for triple-negative breast cancers

Observations and modelisation of blowing and drifting snow over Antarctica

L'augmentation de l'accumulation de neige simulée en Antarctique de l'Est pour le siècle à venir est une contribution négative à la hausse du niveau moyen des mers. Les modèles climatiques simulant cette augmentation ne possèdent pas de paramétrisation du transport éolien de neige or ce dernier joue un rôle primordial sur l'accumulation d'après les observations. Les modèles climatiques régionaux possédant une paramétrisation du transport éolien permettent d'estimer l'incertitude des modèles climatiques sur la hausse du niveau moyen des mers en ne représentant pas ce processus. Cependant aucune donnée de transport ne permet une validation précise de ces modèles en Antarctique. Dans ce contexte, cette thèse décrit la constitution d'une base de données de transport éolien de neige en Antarctique ainsi qu'une validation d'un modèle climatique régional incluant le transport éolien de neige. Un instrument acoustique, le FlowCapt, a été choisi pour acquérir les données. Une comparaison avec un appareil de mesure optique du transport, le Snow Particle Counter, a été menée dans les Alpes françaises. Cette comparaison a permis de déterminer les limites des deux générations de FlowCapt existantes pour la détection des événements de transport et la quantification du flux de neige. Une base de données de trois années a été acquise en Terre Adélie, Antarctique, pour permettre une comparaison avec un modèle climatique régional. Elle a permis de calculer la hauteur de rugosité et la vitesse de frottement seuil avec leurs incertitudes. Les épisodes de transport éolien de neige et une borne inférieure de la quantité de neige déplacée en un point ont été estimés. Deux comparaisons ont été menées avec le Modèle Atmosphérique Régional, un modèle climatique régional incluant de nombreuses rétroactions du transport sur l'écoulement. Les deux simulations utilisées pour les comparaisons ont été faites sur un petit domaine à fine échelle sur une période d'un mois. Le modèle simule bien les épisodes de transport sauf lorsque de la fonte s'est produite juste avant un épisode ou lorsque les épisodes ont une hauteur maximale de transport inférieure à cinquante centimètres. Le modèle sous-estime les quantités de neige transportée.Predicted accumulation by global numerical climate models for the next century increases in East Antarctica and negatively contributes to the mean sea level rise. None of the climate models integrates a blowing snow parametrisation. However few smaller scale regional climate models include a blowing snow parametrisation and thus can assess the climate models uncertainty on the mean sea level rise by not representing this process. Yet none of the blowing snow data available in Antarctica allows for a precise validation of a regional climate model. In this context, this PhD described the establishment of an Antarctica blowing snow database and the validation of a regional climate model including a blowing snow parametrisation. An acoustic blowing snow sensor, the FlowCapt, has been chosen to collect data in Antarctica. A comparison with an optic blowing snow sensor, the Snow Particle Counter, has been conducted in the French Alps. The capacity of the two existing FlowCapt generation has been determined on the blowing snow event and the flux quantification. A three years blowing snow model-oriented database is now available in Adélie Land, Antarctica. The threshold friction velocity and the roughness height have been calculated with their uncertainty. Blowing snow variability has been determined as well as the minimum transport rate at one field point. Two comparisons have been done with the Modèle Atmosphérique Regional (MAR), a regional climate model including a blowing snow parametrisation. Both simulations represent a small domain with a high vertical and horizontal resolution over one month. The model is able to reproduce the blowing snow event except when melting occurs or when the blowing snow height is encompassed within the first fifty centimetres above the ground. The model underestimate the snow quantity transported at the field measurement point

Observations et modélisation de la neige soufflée en Antarctique

Predicted accumulation by global numerical climate models for the next century increases in East Antarctica and negatively contributes to the mean sea level rise. None of the climate models integrates a blowing snow parametrisation. However few smaller scale regional climate models include a blowing snow parametrisation and thus can assess the climate models uncertainty on the mean sea level rise by not representing this process. Yet none of the blowing snow data available in Antarctica allows for a precise validation of a regional climate model. In this context, this PhD described the establishment of an Antarctica blowing snow database and the validation of a regional climate model including a blowing snow parametrisation. An acoustic blowing snow sensor, the FlowCapt, has been chosen to collect data in Antarctica. A comparison with an optic blowing snow sensor, the Snow Particle Counter, has been conducted in the French Alps. The capacity of the two existing FlowCapt generation has been determined on the blowing snow event and the flux quantification. A three years blowing snow model-oriented database is now available in Adélie Land, Antarctica. The threshold friction velocity and the roughness height have been calculated with their uncertainty. Blowing snow variability has been determined as well as the minimum transport rate at one field point. Two comparisons have been done with the Modèle Atmosphérique Regional (MAR), a regional climate model including a blowing snow parametrisation. Both simulations represent a small domain with a high vertical and horizontal resolution over one month. The model is able to reproduce the blowing snow event except when melting occurs or when the blowing snow height is encompassed within the first fifty centimetres above the ground. The model underestimate the snow quantity transported at the field measurement point.L'augmentation de l'accumulation de neige simulée en Antarctique de l'Est pour le siècle à venir est une contribution négative à la hausse du niveau moyen des mers. Les modèles climatiques simulant cette augmentation ne possèdent pas de paramétrisation du transport éolien de neige or ce dernier joue un rôle primordial sur l'accumulation d'après les observations. Les modèles climatiques régionaux possédant une paramétrisation du transport éolien permettent d'estimer l'incertitude des modèles climatiques sur la hausse du niveau moyen des mers en ne représentant pas ce processus. Cependant aucune donnée de transport ne permet une validation précise de ces modèles en Antarctique. Dans ce contexte, cette thèse décrit la constitution d'une base de données de transport éolien de neige en Antarctique ainsi qu'une validation d'un modèle climatique régional incluant le transport éolien de neige. Un instrument acoustique, le FlowCapt, a été choisi pour acquérir les données. Une comparaison avec un appareil de mesure optique du transport, le Snow Particle Counter, a été menée dans les Alpes françaises. Cette comparaison a permis de déterminer les limites des deux générations de FlowCapt existantes pour la détection des événements de transport et la quantification du flux de neige. Une base de données de trois années a été acquise en Terre Adélie, Antarctique, pour permettre une comparaison avec un modèle climatique régional. Elle a permis de calculer la hauteur de rugosité et la vitesse de frottement seuil avec leurs incertitudes. Les épisodes de transport éolien de neige et une borne inférieure de la quantité de neige déplacée en un point ont été estimés. Deux comparaisons ont été menées avec le Modèle Atmosphérique Régional, un modèle climatique régional incluant de nombreuses rétroactions du transport sur l'écoulement. Les deux simulations utilisées pour les comparaisons ont été faites sur un petit domaine à fine échelle sur une période d'un mois. Le modèle simule bien les épisodes de transport sauf lorsque de la fonte s'est produite juste avant un épisode ou lorsque les épisodes ont une hauteur maximale de transport inférieure à cinquante centimètres. Le modèle sous-estime les quantités de neige transportée

Evaluation of the FlowCapt Acoustic Sensor for the Aeolian Transport of Snow

International audienceFlowCapt acoustic sensors, designed for measuring the aeolian transport of snow fluxes, are compared to the snow particle counter S7optical sensor, considered herein as the reference. They were compared in the French Alps at the Lac Blanc Pass, where a bench test for the aeolian transport of snow was set up. The two existing generations of FlowCapt are compared. Both seem to be good detectors for the aeolian transport of snow, especially for transport events with a flux above 1 g m 22 s 21. The second-generation FlowCapt is also compared in terms of quantification. The aeolian snow mass fluxes and snow quantity transported recorded by the second-generation FlowCapt are close to the integrative snow particle counter S7 fluxes for an event without precipitation , but they are underestimated when an event with precipitation is considered. When the winter season is considered, for integrative snow particle counter S7 fluxes above 20 g m 22 s 21 , the second-generation FlowCapt fluxes are underestimated, regardless of precipitation. In conclusion, both generations of FlowCapt can be used as a drifting snow detector and the second generation can record an underestimation of the quantity of snow transported at one location: over the winter season, the quantity of snow transported recorded by the SPC is between 4 and 6 times greater than the quantity recorded by the second-generation FlowCapt

A novel experimental study of aeolian snow transport in Adelie Land (Antarctica)

None of the previous aeolian snow transport campaigns in Antarctica meet the requirements in terms of tempo- ral resolution, long-term series and qualified instruments for evaluations of meteorological and climate models including parameterization for aeolian snow transport. Consequently, determining the quantity of snow transported remains a challenge. A field campaign was therefore launched in January 2009, in Adélie Land, Antarctica, to acquire new model-evaluation-oriented observations within the European ICE2SEA project, with the logistical support of the French polar Institute (IPEV). The available aeolian snow transport sensors are reviewed and the sensor that best suited our specific needs was chosen: FlowCaptTM acoustic sensors. Three au- tomatic weather stations were deployed with FlowCaptsTM close to the coast. The stations' locations are distinct, ranging from 1 to 100 km inland, one of them with a 7-m mast with six levels of anemometers and thermohygrometers. The fluid and impact threshold friction velocities recorded were 0.48 ± 0.09 m s− 1 and 0.4 ± 0.09 m s−1, respectively, with a high standard deviation of 0.12 ± 0.03 m s−1 and 0.13 ± 0.03 m s−1, respectively. The aeolian snow transport frequency in Adélie Land was very high with seasonal variation of trans- port occurring with minima during the austral summer. Seven percent of the aeolian snow transport events were drifting snow (maximum particle's height, b1 m above the surface). The snow quantity transported was above 1 kiloton per year in the first meter above the surface

Direct interaction of TrkA/CD44v3 is essential for NGF-promoted aggressiveness of breast cancer cells

International audienceAbstract Background CD44 is a multifunctional membrane glycoprotein. Through its heparan sulfate chain, CD44 presents growth factors to their receptors. We have shown that CD44 and Tropomyosin kinase A (TrkA) form a complex following nerve growth factor (NGF) induction. Our study aimed to understand how CD44 and TrkA interact and the consequences of inhibiting this interaction regarding the pro-tumoral effect of NGF in breast cancer. Methods After determining which CD44 isoforms (variants) are involved in forming the TrkA/CD44 complex using proximity ligation assays, we investigated the molecular determinants of this interaction. By molecular modeling, we isolated the amino acids involved and confirmed their involvement using mutations. A CD44v3 mimetic peptide was then synthesized to block the TrkA/CD44v3 interaction. The effects of this peptide on the growth, migration and invasion of xenografted triple-negative breast cancer cells were assessed. Finally, we investigated the correlations between the expression of the TrkA/CD44v3 complex in tumors and histo-pronostic parameters. Results We demonstrated that isoform v3 (CD44v3), but not v6, binds to TrkA in response to NGF stimulation. The final 10 amino acids of exon v3 and the TrkA H112 residue are necessary for the association of CD44v3 with TrkA. Functionally, the CD44v3 mimetic peptide impairs not only NGF-induced RhoA activation, clonogenicity, and migration/invasion of breast cancer cells in vitro but also tumor growth and metastasis in a xenograft mouse model. We also detected TrkA/CD44v3 only in cancerous cells, not in normal adjacent tissues. Conclusion Collectively, our results suggest that blocking the CD44v3/TrkA interaction can be a new therapeutic option for triple-negative breast cancers

Transport of Snow by the Wind: A Comparison Between Observations in Adélie Land, Antarctica, and Simulations Made with the Regional Climate Model MAR

For the first time a simulation of blowing snow events was validated in detail using one-month long observations (January 2010) made in Adélie Land, Antarctica. A regional climate model featuring a coupled atmosphere/blowing snow/snowpack model is forced laterally by meteorological re-analyses. The vertical grid spacing was 2 m from 2 to 20 m above the surface and the horizontal grid spacing was 5 km. The simulation was validated by comparing the occurrence of blowing snow events and other meteorological parameters at two automatic weather stations. The Nash test allowed us to compute effi- ciencies of the simulation. The regional climate model simulated the observed wind speed with a positive efficiency (0.69). Wind speeds higher than 12 m s−1 were underestimated. Positive efficiency of the simulated wind speed was a prerequisite for validating the blowing snow model. Temperatures were simulated with a slightly negative efficiency (−0.16) due to overestimation of the amplitude of the diurnal cycle during one week, probably because the cloud cover was underestimated at that location during the period concerned. Snowfall events were correctly simulated by our model, as confirmed by field reports. Because observations suggested that our instrument (an acoustic sounder) tends to overestimate the blowing snow flux, data were not sufficiently accurate to allow the complete validation of snow drift val- ues. However, the simulation of blowing snow occurrence was in good agreement with the observations made during the first 20 days of January 2010, despite the fact that the blowing snow flux may be underestimated by the regional climate model during pure blowing snow events. We found that blowing snow occurs in Adélie Land only when the 30-min wind speed value at 2 m a.g.l. is >10 m s−1. The validation for the last 10 days of January 2010 was less satisfactory because of complications introduced by surface melting and refreezing

ProNGF promotes brain metastasis through TrkA/EphA2 induced Src activation in triple negative breast cancer cells

Abstract Background Triple-Negative Breast Cancer is particularly aggressive, and its metastasis to the brain has a significant psychological impact on patients' quality of life, in addition to reducing survival. The development of brain metastases is particularly harmful in triple-negative breast cancer (TNBC). To date, the mechanisms that induce brain metastasis in TNBC are poorly understood. Methods Using a human blood–brain barrier (BBB) in vitro model, an in vitro 3D organotypic extracellular matrix, an ex vivo mouse brain slices co-culture and in an in vivo xenograft experiment, key step of brain metastasis were recapitulated to study TNBC behaviors. Results In this study, we demonstrated for the first time the involvement of the precursor of Nerve Growth Factor (proNGF) in the development of brain metastasis. More importantly, our results showed that proNGF acts through TrkA independent of its phosphorylation to induce brain metastasis in TNBC. In addition, we found that proNGF induces BBB transmigration through the TrkA/EphA2 signaling complex. More importantly, our results showed that combinatorial inhibition of TrkA and EphA2 decreased TBNC brain metastasis in a preclinical model. Conclusions These disruptive findings provide new insights into the mechanisms underlying brain metastasis with proNGF as a driver of brain metastasis of TNBC and identify TrkA/EphA2 complex as a potential therapeutic target