Aims: To investigate whether and how the JNK/ERK-AP-1/-Runx2 signalling pathways and vascular endothelial growth factor (VEGF) are engaged in the pathogenesis of cartilaginous tumours. Chondrosarcoma is the third most common primary skeletal malignancy. Nevertheless, the molecular events underlying its pathogenesis remain elusive. JNK/ERK MAPKs and their downstream effectors, c-Jun and c-Fos (AP-1), are involved in chondroblastic differention/proliferation. These proteins interact with the Runx2 transcription factor, which is also implicated in chondroblast biology. VEGF, a key angiogenic factor, is up-regulated in human chondrosarcomas.
Methods and results: Normal cartilage and neoplastic cells from 45 chondrosarcomas and 21 enchondromas were investigated immunohistochemically. We evaluated the cellular levels of JNK2, p-JNK2 (phosphorylated/activated JNK2), its main substrate, c-Jun, pc-Jun (phosphorylated/activated c-Jun) and c-Fos. Moreover, the levels of p-ERK (phosphorylated/activated ERK), Runx2 and VEGF were assessed. Positive immunostaining for all proteins was observed in the majority of the examined chondrosarcomas and in a small fraction of enchondromas. The expression levels of all proteins were positively and significantly correlated with each other. These levels were substantially augmented in high-grade compared with low-grade chondrosarcomas and in low-grade tumours compared with benign enchondromas, implying a potential use as molecular markers for prediction of high-grade neoplasms.
Conclusions: The JNK/ERK-AP-1/-Runx2 signal transduction 'network' is associated with chondroblastic malignant transformation and chondrosarcoma development, either separately or through coordinated induction of VEGF.