zd-6474 and Thyroid-Neoplasms

It is now known that "gain of function" mutations of RET (REarranged during Transfection) kinase are specific and key oncogenic events in the onset of thyroid gland cancers such as the Medullary Thyroid Carcinoma (MTC). Although a number of RET inhibitors exist and are capable of inhibiting RET variants, in which mutations are outside the enzyme active site, the majority becomes dramatically ineffective when mutations are within the protein active site (V804L and V804M). Pursuing a receptor-based virtual screening against the kinase domain of RET, we found that compound 5 is able to inhibit efficiently both wild type and V804L mutant RET. Compound 5 was able to significantly reduce proliferation of both commercially available TT cell lines and surgical thyroid tissues obtained from patients with MTC and displayed a suitable drug-like profile, thus standing out as a promising candidate for further development towards the treatment of clinically unresponsive MTC.

Topics: Antineoplastic Agents; Carcinoma, Neuroendocrine; Cell Line, Tumor; Cell Proliferation; Dose-Response Relationship, Drug; Drug Discovery; Drug Screening Assays, Antitumor; Humans; Molecular Structure; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-ret; Structure-Activity Relationship; Thyroid Gland; Thyroid Neoplasms

RET/papillary thyroid carcinoma (PTC) oncogenes, generated by recombination of the tyrosine kinase-encoding domain of RET with different heterologous genes, are prevalent in papillary carcinomas of the thyroid. Point mutations of RET cause multiple endocrine neoplasia type 2 (MEN2) familial cancer syndrome and are found in sporadic medullary thyroid carcinomas. Here, we show that ZD6474, a low molecular weight tyrosine kinase inhibitor, blocks the enzymatic activity of RET-derived oncoproteins at a one-half maximal inhibitory concentration of 100 nM. ZD6474 blocked in vivo phosphorylation and signaling of the RET/PTC3 and RET/MEN2B oncoproteins and of an epidermal growth factor (EGF)-activated EGF-receptor/RET chimeric receptor. RET/PTC3-transformed cells-treated ZD6474 lost proliferative autonomy and showed morphological reversion. ZD6474 prevented the growth of two human PTC cell lines that carry spontaneous RET/PTC1 rearrangements. Finally, it blocked anchorage-independent growth of RET/PTC3-transformed NIH3T3 fibroblasts and the formation of tumors after injection of NIH-RET/PTC3 cells into nude mice. Thus, targeting RET oncogenes with ZD6474 might offer a potential treatment strategy for carcinomas sustaining oncogenic activation of RET.

Topics: 3T3 Cells; Animals; Carcinoma, Papillary; Cell Transformation, Neoplastic; Drosophila Proteins; Enzyme Inhibitors; Mice; Mice, Inbred BALB C; Mice, Nude; Phosphorylation; Piperidines; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-ret; Quinazolines; Receptor Protein-Tyrosine Kinases; Signal Transduction; Thyroid Neoplasms; Vascular Endothelial Growth Factor Receptor-2