Methods of treatment and diagnosis of tumours

The invention relates to a method of treating a cartilage matrix-forming bone tumour and/or a metastatic cancer originating from a cartilage matrix-forming bone tumour, for example chondrosarcoma, in which one or more of an inhibitor of RUNX2 activity, an inhibitor of RUNX2 expression, an inhibitor of YBX1 activity and an inhibitor of YBX1 expression, is administered to a subject in need thereof. The invention also relates to an in vitro method for detecting the presence of a cartilage matrix-forming bone tumour in a subject or the risk of a subject developing a cartilage matrix-forming bone tumour, for example chondrosarcoma, in which the following steps are performed: (i) measuring the expression level of at least one of RUNX2 and YBX1 in a biological sample obtained from a subject , and (ii) com paring the expression level of RUNX2 and/or YBX1 in the biological sample obtained from the subject with the respective expression level of RUNX2 and/or YBX1 in normal cartilage or other biological material. A higher expression level of RUNX2 and/or YBX1 in the biological sample obtained from the subject compared to the respective expression level of RUNX2 and/or YBX1 in the normal cartilage or other biological material indicates the presence of or an increased risk of developing a cartilage matrix-forming bone tumour.