A unique peptide stabilization method provides a tethered sulfonium that can rapidly and selectively modify protein cysteine in close vicinity.

A general peptide reversible macrocyclization strategy is developed based on a facile and chemoselective methionine bis-alkylation/dealkylation process.

We report a facile thiol-yne type reaction triggered by the sulfonium center. After facile propargylation of thiolethers, the resulting sulfonium could undergo facile addition with thiols in aqueous media at ambient temperature. Further applying this reaction in unprotected peptides bearing neighboring methionine and cysteine could enable a facile intramolecular addition to construct cyclic peptides with better stability, good glutathione resistance, and increased cellular uptakes. Also, the propargylated sulfonium may be used as robust and versatile probes to target cysteines containing biomolecules.

FDA-approved HDAC inhibitors exhibit dose-limiting adverse effects; thus, we sought to improve the therapeutic windows for this class of drugs. In this report, we describe a new class of peptide-based HDAC inhibitors derived from the HDAC1-specific substrate H3K56 with improved nonspecific toxicity compared with traditional small-molecular inhibitors. We showed that our designed peptides exerted superior antiproliferation effects on cancer stem–like cells with minimal toxicity to normal cells compared with the small-molecular inhibitor SAHA, which showed nonspecific toxicity to normal and cancer cells. These peptide inhibitors also inactivated cellular HDAC1 and HDAC6 and disrupted the formation of the HDAC1, LSD1, and CoREST complex. In ovarian teratocarcinoma (PA-1) and testicular embryonic carcinoma (NTERA-2) cell xenograft animal models (5 mice/group, 50 mg/kg, every other day, intraperitoneal injection), these peptides inhibited tumor growth by 80% to 90% with negligible organ (heart, liver, spleen, lung, kidney, brain) lesions. These results represent the first attempt to design chemically stabilized peptide inhibitors to investigate HDAC inhibition in cancer stem–like cells. These novel peptide inhibitors have significantly enhanced therapeutic window and offer promising opportunities for cancer therapy. Significance: Selective antiproliferative effects of stabilized peptide HDAC inhibitors toward cancer stem–like cells provide a therapeutic alternative that avoids high nonspecific toxicity of current drugs.

Herein, we report a unique siRNA-induced peptide co-assembly nanocarrier, which could efficiently co-assemble upon the addition of siRNA, forming nanospheres with high biocompatibility and transfection efficiency both in vitro and in vivo.

Epigenetics process is the heritable change in gene function that does not involve changes in the DNA sequence. Until now, several types of epigenetic mechanisms have been characterized, including DNA methylation, histone modification (acetylation, methylation, etc.), nucleosome remodeling, and noncoding RNAs. With the biological investigations of these modifiers, some of them are identified as promoters in the process of various diseases, such as cancer, cardiovascular disease and virus infection. Epigenetic changes may serve as potential “first hits” for tumorigenesis. Hence, targeting epigenetic modifiers is being considered as a promising way for disease treatment. To date, six agents in two epigenetic target classes (DNMT and HDAC) have been approved by the US Food and Drug Administration (FDA). Most of these drugs are applied in leukemia, lymphoma therapy, or are combined with other drugs for the treatment of solid tumor. Due to the rapid development of epigenetics and epigenetics targeted drugs, it is becoming an emerging area in targeted drug design.

Anti-apoptotic B cell lymphoma 2 (BCL-2) family proteins are proven targets for human cancers. Targeting the BH3-binding pockets of these anti-apoptotic proteins could reactivate apoptosis in BCL-2-depedent cancers. BFL-1 is a BCL-2 family protein overexpressed in various chemoresistant cancers. A unique cysteine at the binding interface of the BH3 and BFL-1 was previously proven to be an intriguing targeting site to irreversibly inhibit BFL-1 functions with stabilized cyclic peptide bearing a covalent warhead. Recently, we developed a sulfonium-tethered peptide cyclization strategy to construct peptide ligands that could selectively and efficiently react with the cysteine(s) of target proteins near the interacting interface. Using this method, we constructed a BFL-1 peptide inhibitor, B4-MC, that could selectively conjugate with BFL-1 both in vitro and in cell. B4-MC showed good cellular uptake, colocalized with BFL-1 on mitochondria, and showed obvious growth inhibition of BFL-1 over-expressed cancer cell lines.

Continuous efforts have been invested in the selective modification of proteins.