MiR-9 is highly expressed in biologically high grade canine MCTs and malignant mast cell lines. (A) Real-time PCR evaluating mature miR-9 expression in primary canine MCTs demonstrated that the mean expression of miR-9 was 3.2-fold higher in aggressive, high grade MCTs compared to benign MCTs (p = 0.001). (*) indicates primary tumor sample from a dog with a low-grade mast cell tumor that expressed high levels of miR-9 but had lymph node metastasis at the time of surgery. (B) Malignant canine BR and C2 mast cells, normal canine and mouse BMMCs, and malignant mouse C57 and P815 cells were cultured and real-time PCR was performed to assess miR-9 expression levels. Three independent experiments were performed and all reactions were performed in triplicate. The experiments were repeated 3 times in the cell lines and twice for normal cBMMCs.