Down-regulation of ephrin-A5, a gene product of normal cartilage, in chondrosarcoma.

As ephrins have been associated with tumorigenesis and tumor progression, we investigated ephrin-A5 (EFNA5) expression in specimens of normal cartilage and chondrosarcomas of different grade by conventional and quantitative reverse transcription polymerase chain reaction (RT-PCR), Western blot, and immunohistochemistry. We detected a significant EFNA5 down-regulation in chondrosarcomas compared with normal cartilage using quantitative RT-PCR (P < .05). The results were confirmed by Western blot and immunohistochemistry. We did not detect any causative genetic or epigenetic alterations in EFNA5 promoter methylation, loss of heterozygosity, or mutation analyses. Apart from slight differences in EFNA5 transcript amounts, we detected no significant influence of hypoxia on EFNA5 expression in C3842 and SW1353 chondrosarcoma cells. As EFNA5 down-regulation is a consistent finding in chondrosarcomas, we presume that it represents another essential alteration in tumorigenesis and tumor progression associated with cell adhesion, in addition to a multitude of other partially unknown biologic functions mediated by bidirectional ephrin/Eph receptor signaling and cross talk.