Intramolecular cyclization of N-phenyl N′(2-chloroethyl)ureas leads to active N-phenyl-4,5-dihydrooxazol-2-amines alkylating β-tubulin Glu198 and prohibitin Asp40

Abstract

The cyclization of anticancer drugs into active intermediates has been reported mainly for DNA alkylating molecules including nitrosoureas. We previously defined the original cytotoxic mechanism of anticancerous N-phenyl-N'-(2-chloroethyl)ureas (CEUs) that involves their reactivity towards cellular proteins and not against DNA; two CEU subsets have been shown to alkylate β-tubulin and prohibitin leading to inhibition of cell proliferation by G₂/M or G₁/S cell cycle arrest. In this study, we demonstrated that cyclic derivatives of CEUs, N-phenyl-4,5-dihydrooxazol-2-amines (Oxas) are two- to threefold more active than CEUs and share the same cytotoxic properties in B16F0 melanoma cells. Moreover, the CEU original covalent binding by an ester linkage on β-tubulin Glu198 and prohibitin Asp40 was maintained with Oxas. Surprisingly, we observed that Oxas were spontaneously formed from CEUs in the cell culture medium and were also detected within the cells. Our results suggest that the intramolecular cyclization of CEUs leads to active Oxas that should then be considered as the key intermediates for protein alkylation. These results will be useful for the design of new prodrugs for cancer chemotherapy.

Prohibitin Ligands in Cell Death and Survival: Mode of Action and Therapeutic Potential

“…Aftin-4 was found to interact with three proteins related to neural degeneration: PHB1, voltage-dependent anion channel 1 (VDAC1), and mitofilin. cHOxa The dihydrooxazole cHOxa, which displays some cytotoxicity with a GI 50 of 7.2 mM in B16F0 cells, was shown to alkylate the Asp40 of PHB1, suggesting that it could be used as a chemical probe to analyze the structure of PHB1 (Trzeciakiewicz et al, 2011; Figure 4G).…”

Expanding the Scope of Electrophiles Capable of Targeting K-Ras Oncogenes

“…A strategy for proximity-dependent labeling of aspartate or glutamate could find broad use in covalent probes . We wondered if the interaction between an optimized Ras ligand and K-Ras could promote a reaction between G12D and a functional group known to label catalytic carboxylates, such as an epoxide, aziridine, or chloroacetamide. ,− We also considered functional groups that have been reported to label noncatalytic aspartate and glutamate residues, such as chloroethylureas, stabilized diazo groups, , trichloroacetimidates, and acyl imidazoles . Here, we report the ability of these electrophiles to react with model nucleophiles and to form covalent complexes with K-Ras G12C.…”