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, vascular endothelial growth factor (VEGF) receptor (VEGFR) 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).

CLM3 was tested: in primary ATC cells at the concentrations of 5, 10, 30, 50 μM; in 8305C cells, and in AF cells, at 1, 5, 10, 30, 50 or 100 μM; in AF cells in CD nu/nu mice.

CLM3 significantly inhibited proliferation of 8305C and AF cells, inducing also apoptosis. A significant reduction of proliferation with CLM3 in ATC cells (P < 0.01, ANOVA) was shown. CLM3 increased the percentage of apoptotic ATC cells dose-dependently (P < 0.001, ANOVA) and inhibited migration (P < 0.01) and invasion (P < 0.001). AF-cell line was injected sc in CD nu/nu mice and tumor masses became detectable 15 days after. CLM3 (50 mg/kg/die) inhibited significantly tumor growth (starting 16 days after the beginning of treatment). CLM3 significantly decreased the VEGF-A expression and microvessel density in AF tumor tissues. Furthermore, CLM3 inhibited EGFR, AKT and ERK1/2 phosphorylation and down-regulated cyclin D1 in 8305C and AF cells.

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.