Eosinophilic myeloid neoplasms

PDGFRβ reverses EphB4 signaling in alveolar rhabdomyosarcoma

Alveolar rhabdomyosarcoma (aRMS) is an aggressive myogenic childhood malignancy, not infrequently presenting as incurable metastatic disease. To identify therapeutic targets, we performed an unbiased tyrosine kinome RNA interference screen in primary cell cultures from a genetically engineered, conditional mouse model of aRMS. We identified ephrin receptor B4 (EphB4) as a target that is widely expressed in human aRMS and that portends a poor clinical outcome in an expression level-dependent manner. We also uncovered cross-talk of this ephrin receptor with another receptor tyrosine kinase, PDGFRβ, which facilitates PDGF ligand-dependent, ephrin ligand-independent activation of EphB4 converging on the Akt and Erk1/2 pathways. Conversely, EphB4 activation by its cognate ligand, EphrinB2, did not stimulate PDGFRβ; instead, apoptosis was paradoxically induced. Finally, we showed that small-molecule inhibition of both PDGFRβ and EphB4 by dasatinib resulted in a significant decrease in tumor cell viability in vitro, as well as decreased tumor growth rate and significantly prolonged survival in vivo. To our knowledge, these results are the first to identify EphB4 and its cross-talk with PDGFRβ as unexpected vital determinants of tumor cell survival in aRMS, with EphB4 at the crux of a bivalent signaling node that is either mitogenic or proapoptotic.

Gene expression analysis in allergology: the prediction of Hymenoptera venom allergy severity and treatment efficacy

Insect venom allergy (IVA) may result in the most severe systemic reactions seen in allergology. The only potentially curative treatment option is venom immunotherapy (VIT) over 3 to 5 years. This treatment is effective in more than 90% of subjects but no reliable predictors of VIT effectiveness exist. Sting challenge with a living insect can be performed to assess the effectiveness of VIT: the predictive value of sting challenge can be highly sensitive in patients with honeybee venom allergy whereas in yellow jacket allergy, a negative result can be reliable if the challenge has been repeated at least 3 times.

The analysis of gene expression may be a step towards personalized venom immunotherapy assessing the effectiveness of treatment, the minimal required time for VIT and the persistence of long term tolerance induced by the treatment. Recent studies have enabled construction of a predictive model that could potentially be used in clinical practice to assess the efficacy of insect venom immunotherapy. A set of 69 genes that may be responsible for long-term protection was identified. Further analysis of the previously identified 6 transcripts make up the 18 gene predictive peripheral blood showed differences in patients treated with IVA. Further studies are needed to investigate the usefulness of gene expression analysis and other markers in the prediction of VIT effectiveness.