Isoalantolactone/hydroxamic acid hybrids as potent dual STAT3/HDAC inhibitors and self-assembled nanoparticles for cancer therapy.

Conventional chemotherapy, especially with natural anticancer drugs, usually suffers from poor bioavailability and low tumor accumulation. To address these limitations, we developed a novel approach for modifying natural products in which amphiphilic hydroxamic acid hybrids based on a natural product: isoalantolactone (IAL) were rationally designed. Compound 18 is identified as a highly potent dual signal transducer and activator of transcription 3 (STAT3)/histone deacetylases (HDAC) inhibitor and induces autophagy and apoptosis. 18 exhibits higher antitumor potency than IAL and the hydroxamic acid SAHA in vitro and in vivo. Furthermore, 18 self-assembled in water to form nanoparticles (18 NPs), which facilitated the accumulation of drugs in tumor tissues and promoted their cellular uptake, resulting in superior anticancer efficacy compared to free 18. Compared to drug-drug conjugates, hydroxamic acid hybrids have a smaller molecular weight and can synergize with various anticancer drugs. Overall, these findings indicate that 18 utilizing nanomedicines and dual-target drugs provide an efficient strategy for the rational design of dual-target drugs and the modification of natural products.

Synthesis and anticancer activity of novel histone deacetylase inhibitors that inhibit autophagy and induce apoptosis.

The combination of histone deacetylase (HDAC) and autophagy inhibitor has been considered as a novel cancer therapeutic strategy. To find novel HDAC inhibitors that can inhibit autophagy, several new series of oxazole- and thiazole-based HDAC inhibitors were designed and synthesized by replacing the phenyl cap in SAHA with 5-phenyloxazoles and 5-phenylthiazoles. The representative oxazole derivative, compound 21, showed better enzymatic inhibitory activity than SAHA (vorinostat). Compound 21 induced G2/M cell cycle arrest and its antiproliferative activity is 10-fold better than SAHA in multiple tumor cell lines. Western blot analysis showed that compound 21 can markedly increase the acetylation levels of tubulin, histone H3, and histone H4. Contrary to SAHA, compound 21 was found to inhibit autophagy. Additionally, compound 21 induced cell apoptosis via the Bax/Bcl-2 and caspase-3 pathways. Ultimately, compound 21 exhibited higher oral antitumor potency than SAHA in a A549 xenograft model. Our results indicated that compound 21 may be further developed as a promising anticancer agent.

Synthesis and structure-activity relationships of 5-phenyloxazole-2-carboxylic acid derivatives as novel inhibitors of tubulin polymerization.

A series of 5-phenyloxazole-2-carboxylic acid derivatives were synthesized, and their structure-activity relationships (SARs) were studied. N,5-diphenyloxazole-2-carboxamides 6, 7, and 9, which mimicked ABT751, showed improved cytotoxicity compared with ABT751. Compound 9 exhibited the highest antiproliferative activities against Hela A549, and HepG2 cancer cell lines, with IC50 values of 0.78, 1.08, and 1.27 µM, respectively. Furthermore, compound 9 showed selectivity for human cancer cells over normal cells, and this selectivity was greater than those of ABT751 and colchicine. Preliminary mechanism studies suggested that compound 9 inhibited tubulin polymerization and led to cell cycle arrest at G2/M phase. Molecular docking studies indicated that compound 9 bound to the colchicine binding site of tubulin. Our findings provided insights into useful SARs for further structural modification of inhibitors of tubulin polymerization.