miR-1 and miR-133b expression in canine osteosarcoma.

Osteosarcoma (OS) is the most common primary malignant bone tumor in dogs and it is reported to represent 80-85% of primitive bone tumors and 3-4% of all canine tumors. Canine OS is highly comparable to human OS since it is characterized by similar genetic, biologic and clinical pathological features. MicroRNAs (miRNAs) are small non-coding RNA segments controlling post-transcriptional gene expression whose altered regulation has been described in different malignant tumors. In this study we analyzed the expression of two miRNAs with an important role in regulation of osteogenesis and tumor cell proliferation in order to define their role in canine OS development. A lower expression of miR-1 and miR-133b was seen in tumors when compared with normal bone associated to a higher expression of two target genes, respectively MET and MCL1. Accordingly, MET and MCL11 proteins presented a moderate to strong immunostaining in more than 50% of tumor samples. Our results, although obtained in a small series of cases, confirming the high molecular homology with human OS suggesting a potential role of miR-1 and miR-133b as biomarkers for canine OS treatment.