Synthesis of Oleanolic Acid-Dithiocarbamate Conjugates and Evaluation of Their Broad-Spectrum Antitumor Activities.

Efficient and mild synthetic routes for bioactive natural product derivatives are of current interest for drug discovery. Herein, on the basis of the pharmacophore hybrid strategy, we report a two-step protocol to obtain a series of structurally novel oleanolic acid (OA)-dithiocarbamate conjugates in mild conditions with high yields. Moreover, biological evaluations indicated that representative compound 3e exhibited the most potent and broad-spectrum antiproliferative effects against Panc1, A549, Hep3B, Huh-7, HT-29, and Hela cells with low cytotoxicity on normal cells. In terms of the IC50 values, these OA-dithiocarbamate conjugates were up to 30-fold more potent than the natural product OA. These compounds may be promising hit compounds for the development of novel anti-cancer drugs.

PROTACs in gastrointestinal cancers.

Proteolysis targeting chimera (PROTAC) presents a powerful strategy for targeted protein degradation (TPD). The heterobifunctional PROTAC molecule consists of an E3 ligase ligand covalently linked to a protein of interest (POI) via a linker. PROTAC can induce ubiquitinated proteasomal degradation of proteins by hijacking the ubiquitin-proteasome degradation system (UPS). This technique has the advantages of broad targeting profile, good cell permeability, tissue specificity, high selectivity, oral bioavailability, and controllability. To date, a growing number of PROTACs targeting gastrointestinal cancers have been successfully developed, and, in many cases, their POIs have been validated as clinical drug targets. To the best of our knowledge, 15 PROTACs against various targets are currently tested in clinical trials, and many more are likely to be added in the near future. Therefore, this paper details the mechanism, research progress, and application in clinical trials of PROTACs, and summarizes the research achievements related to PROTACs in gastrointestinal cancers. Finally, we discuss the advantages and potential challenges of PROTAC for cancer treatment.

Carboranes as unique pharmacophores in antitumor medicinal chemistry.

Carborane is a carbon-boron molecular cluster that can be viewed as a 3D analog of benzene. It features special physical and chemical properties, and thus has the potential to serve as a new type of pharmacophore for drug design and discovery. Based on the relative positions of two cage carbons, icosahedral closo-carboranes can be classified into three isomers, ortho-carborane (o-carborane, 1,2-C2B10H12), meta-carborane (m-carborane, 1,7-C2B10H12), and para-carborane (p-carborane, 1,12-C2B10H12), and all of them can be deboronated to generate their nido- forms. Cage compound carborane and its derivatives have been demonstrated as useful chemical entities in antitumor medicinal chemistry. The applications of carboranes and their derivatives in the field of antitumor research mainly include boron neutron capture therapy (BNCT), as BNCT/photodynamic therapy dual sensitizers, and as anticancer ligands. This review summarizes the research progress on carboranes achieved up to October 2021, with particular emphasis on signaling transduction pathways, chemical structures, and mechanistic considerations of using carboranes.