The pyrazolo[3,4-d]pyrimidine derivative CLM24 has an antineoplastic effect in aggressive dedifferentiated thyroid cancer in vitro

Purpose: Compounds with a pyrazolo[3,4-d]pyrimidine nucleus (CLM24, CLM3, and CLM29) with inhibitory activities towards RET protein kinases, EGFR, VEGFR and as antiangiogenic agents had been evaluated in preceding researches in experimental models of thyroid cancer (TC) in vitro and in vivo. Here, we designed a study to evaluate the antineoplastic activity of CLM24 in vitro in primary dedifferentiated thyroid carcinoma (DeDTC) cells and in the AF cell line (a continuous ATC cell line previously obtained from a patient-derived cell culture and immortalized in vitro). Methods: We investigated in vitro CLM24 in human primary cultures from 10 patients with DeDTC and 5 healthy controls, and in the continuous AF cell line (as a comparative reference), evaluating its effect on cell proliferation, apoptosis, migration/invasion, and VEGF-A expression. Results: CLM24 showed a significant antiproliferative effect on the AF cell line (harboring the BRAF p.V600E mutation), along with a marked pro-apoptotic activity. In primary DeDTC cells with/without BRAF p.V600E mutation, CLM24 significantly reduced cell proliferation compared with controls, whereas no effect was observed in primary normal thyrocytes. In DeDTC cells with/without BRAF p.V600E mutation, the proportion of apoptotic cells increased in a dose-dependent manner following CLM24 treatment, which also significantly inhibited cell migration/invasion. Furthermore, CLM24 reduced significantly VEGF-A expression in DeDTC cells, especially at higher concentrations. Conclusion: CLM24 exhibited a potent antineoplastic effect in vitro in primary DeDTC cells, regardless of the presence of the BRAF p.V600E mutation. These encouraging results suggest further studies to assess CLM24 in a possible clinical trial setting.