CLM3, a Multitarget Tyrosine Kinase Inhibitor With Antiangiogenic Properties, Is Active Against Primary Anaplastic Thyroid Cancer In Vitro and In Vivo

Context and Objective: We have studied the antitumor activity of a pyrazolo[3,4-d] pyrimidine compound (CLM3) proposed for a multiple signal transduction inhibition [including the RET tyrosine kinase, epidermal growth factor receptor, and vascular endothelial growth factor (VEGF) receptor and with antiangiogenic activity] in primary anaplastic thyroid cancer (ATC) cells, in the human cell line 8305C (undifferentiated thyroid cancer), and in an ATC-cell line (AF). Design and Main Outcome Measures: CLM3 was tested in primary ATC cells at the concentrations of 5, 10, 30, and 50 mu M; in 8305C cells, in AF cells, at 1, 5, 10, 30, 50, or 100 mu M; and in AF cells in CD nu/nu mice. Results: CLM3 significantly inhibited the proliferation of 8305C and AF cells, also inducing apoptosis. A significant reduction of proliferation with CLM3 in ATC cells (P < .01, ANOVA) was shown. CLM3 increased the percentage of apoptotic ATC cells dose dependently (P < .001, ANOVA) and inhibited migration (P < .01) and invasion (P < .001). The AF cell line was injected sc in CD nu/nu mice, and tumor masses became detectable 15 days later. CLM3 (50 mg/kg per die) significantly inhibited tumor growth (starting 16 d after the beginning of treatment). CLM3 significantly decreased the VEGF-A expression and microvessel density in AF tumor tissues. Furthermore, CLM3 inhibited epidermal growth factor receptor, AKT, and ERK1/2 phosphorylation and down-regulated cyclin D1 in 8305C and AF cells. Conclusions: The antitumor and antiangiogenic activity of a pyrazolo[3,4-d] pyrimidine compound (CLM3) is very promising in anaplastic thyroid cancer, opening the way to a future clinical evaluation.