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Eph receptors are a unique family of receptor tyrosine kinases (RTK) that play critical roles in embryonic patterning, neuronal targeting, and vascular development during embryogenesis. In adults, Eph RTKs and their ligands, the ephrins, are frequently overexpressed in a variety of cancers and tumor cell lines, including breast, prostate, non-small cell lung and colon cancers, melanomas, and neuroblastomas. Unlike traditional oncogenes that often function only in tumor cells, recent data show that Eph receptors mediate cell-cell interaction both in tumor cells and in tumor microenvironment, namely the tumor stroma and tumor vasculature. As such, Eph RTKs represent attractive potential targets for drug design, as targeting these molecules could attack several aspects of tumor progression simultaneously. This review will focus on recent advances in dissecting the role of Eph RTKs in tumor cells, tumor angiogenesis, and possible contribution to trafficking of inflammatory cells in cancer.

Synapse maturation includes the shortening of postsynaptic currents, due to changes in the subunit composition of respective transmitter receptors. Patch clamp experiments revealed that GABAergic inhibitory postsynaptic currents (ISPCs) of superior colliculus neurons significantly shorten from postnatal day (P)1 to P21. The change started after P6 and was steepest between P12 and P15, i.e. around eye opening. It was accompanied by enhanced sensitivity to zolpidem and increased expression of GABAAR alpha1 mRNA, whereas the level of alpha3 mRNA decreased. This result is consistent with the hypothesis that the IPSC kinetics of developing collicular neurons is determined by the level of alpha1/alpha3. As alpha1/alpha3 peaked when N-methyl-D-aspartate receptor (NMDAR)-mediated synaptic currents reached their maximum (P12) it was asked whether NMDAR activity can shape the kinetics of GABAergic IPSCs. Cultured collicular neurons were treated with NMDA or NMDAR block, and it was found that the former resulted in faster and the latter in slower IPSC decay. Group I mGluR blockade had no effect. Experiments with bdnf-/- mice revealed that, with some delay, the increase of alpha1/alpha3 mRNA also occurred in the chronic absence of brain-derived neurotrophic factor (BDNF) and, again, this was accompanied by the shortening of IPSCs. In addition, there was an age-dependent depression of IPSC amplitudes by endogenous BDNF, which might reflect the developmental increase in the expression of GABAAR gamma2L, as opposed to gamma2S. Together, these experiments suggest that the GABAAR alpha subunit switch and the associated change in the IPSC kinetics were specifically controlled by NMDAR activity and independent on the signalling through group I mGluRs or TrkB.