Characterization of LDD-2633 as a Novel RET Kinase Inhibitor with Anti-Tumor Effects in Thyroid Cancer

Abstract

Rearranged during transfection (RET), a receptor tyrosine kinase, is activated by glial cell line-derived neurotrophic factor family ligands. Chromosomal rearrangement or point mutations in RET are observed in patients with papillary thyroid and medullary thyroid carcinomas. Oncogenic alteration of RET results in constitutive activation of RET activity. Therefore, inhibiting RET activity has become a target in thyroid cancer therapy. Here, the anti-tumor activity of a novel RET inhibitor was characterized in medullary thyroid carcinoma cells. The indirubin derivative LDD-2633 was tested for RET kinase inhibitory activity. In vitro, LDD-2633 showed potent inhibition of RET kinase activity, with an IC50 of 4.42 nM. The growth of TT thyroid carcinoma cells harboring an RET mutation was suppressed by LDD-2633 treatment via the proliferation suppression and the induction of apoptosis. The effects of LDD-2633 on the RET signaling pathway were examined; LDD-2633 inhibited the phosphorylation of the RET protein and the downstream molecules Shc and ERK1/2. Oral administration of 20 or 40 mg/kg of LDD-2633 induced dose-dependent suppression of TT cell xenograft tumor growth. The in vivo and in vitro experimental results supported the potential use of LDD-2633 as an anticancer drug for thyroid cancers.

Crucial Role of Reactive Oxygen Species (ROS) for the Proapoptotic Effects of Indirubin Derivatives in Cutaneous SCC Cells

“…Indirubin activity may be further enhanced by chemical modifications, and several new derivatives were described that showed antitumor activities in in vitro and in vivo tumor models, such as for non-small cell lung cancer, glioblastoma, breast, bladder, thyroid, hepatocellular and colorectal cancer [41][42][43][44][45][46]. We have previously reported a series of new indirubin derivatives based on N-glycosylated 3-alkylideneoxindoles containing halogen substituents [30,32].…”

The Fundamental Role of Oxime and Oxime Ether Moieties in Improving the Physicochemical and Anticancer Properties of Structurally Diverse Scaffolds

“…Jeong et al [108][109][110] further demonstrated that these piperazinium hydrochloride derivatives of indirubin-3 -oxime were potent inhibitors of FLT3 kinase and MV4-11 cells, with compounds 53 and 54 exhibiting the highest potency. Docking studies suggested that compound 53 bound tightly to the ATP binding pocket in FLT3, surrounded by residues Leu616, Leu818, Cys828, and Tyr693, and forming approximately five hydrogen bonds with these residues [108,109].…”

“…Jeong et al [108][109][110] further demonstrated that these piperazinium hydrochloride derivatives of indirubin-3 -oxime were potent inhibitors of FLT3 kinase and MV4-11 cells, with compounds 53 and 54 exhibiting the highest potency. Docking studies suggested that compound 53 bound tightly to the ATP binding pocket in FLT3, surrounded by residues Leu616, Leu818, Cys828, and Tyr693, and forming approximately five hydrogen bonds with these residues [108,109]. While the indirubin core formed two significant hydrogen bonds with the backbone Cys694 residue, the tertiary amine of the piperazine moiety formed a hydrogen bond with Asn816, and the terminal amino group established two hydrogen bonds with both Asn816 and Asp829 [108,109].…”

“…Docking studies suggested that compound 53 bound tightly to the ATP binding pocket in FLT3, surrounded by residues Leu616, Leu818, Cys828, and Tyr693, and forming approximately five hydrogen bonds with these residues [108,109]. While the indirubin core formed two significant hydrogen bonds with the backbone Cys694 residue, the tertiary amine of the piperazine moiety formed a hydrogen bond with Asn816, and the terminal amino group established two hydrogen bonds with both Asn816 and Asp829 [108,109]. Moreover, compound 53 effectively inhibited cell growth in vivo in an MV4-11 xenograft model following a daily oral administration of 20 mg/kg, without inducing significant hERG-related cardiotoxicity [108][109][110].…”

“…Conversely, compound 52 inhibited the growth of TT thyroid carcinoma cells by suppressing cell proliferation and inducing apoptosis [110]. This compound was also found to suppress the RET signaling pathway via a downregulation of the phosphorylation of RET kinase as well as the downstream Shc and ERK1/2 [108,109]. Dicationic piperazinium dihydrochloride derivatives of indirubin-3 -oxime have also been extensively studied for their anticancer activities.…”