Gabriel Fung

Well-Defined, Reversible Boronate Crosslinked Nanocarriers for Targeted Drug Delivery in Response to Acidic pH Values and cis-Diols†

Stimuli-responsive nanoparticles are gaining considerable attention in the field of drug delivery due to their useful physicochemical changes in response to specific triggers, such as pH[1], temperature[2], enzymes[3] or redox conditions[4], present in certain physiological or disease microenvironment of interest. Among these nanoparticles, stimuli-responsive cross-linked micelles (SCMs) represent a versatile nanocarrier system for tumor targeting drug delivery[2c, 4-5]. For instance, SCMs exhibit superior structural stability under physiological condition compared to the non-crosslinked counterpart. As a result, these nanocarriers are able to better retain the encapsulated drug and minimize its premature release while circulating in the blood pool[2c, 4b, 5b]. The introduction of environmentally sensitive crosslinkers makes SCMs responsive to the local environment of the tumor (e.g. tumor extra-cellular pH (6.5-7.2), endosomal/lysosomal pH (4.5–6)[5b, 6], and tumor reductive intra-cellular condition[4-5]). In these instances, the payload drug is released almost exclusively in the cancerous tissue upon accumulation via the well known enhanced permeation and retention (EPR) effect[2c, 4b, 5b].

PEG-oligocholic acid telodendrimer micelles for the targeted delivery of doxorubicin to B-cell lymphoma

Doxorubicin (DOX) is one of most common anti-cancer chemotherapeutic drugs, but its clinical use is associated with dose-limiting cardiotoxicity. We have recently developed a series of PEG-oligocholic acid based telodendrimers, which can efficiently encapsulate hydrophobic drugs and self-assemble to form stable micelles in aqueous condition. In the present study, two representative telodendrimers (PEG(5k)-CA(8) and PEG(2k)-CA(4)) have been applied to prepare DOX micellar formulations for the targeted delivery of DOX to lymphoma. PEG(2k)-CA(4) micelles, compared to PEG(5k)-CA(8) micelles, were found to have higher DOX loading capacity (14.8% vs. 8.2%, w/w), superior stability in physiological condition, and more sustained release profile. Both of these DOX-loaded micelles can be efficiently internalized and release the drug in Raji lymphoma cells. DOX-loaded micelles were found to exhibit similar in vitro cytotoxic activities against both T- and B-lymphoma cells as the free DOX. The maximum tolerated dose (MTD) of DOX-loaded PEG(2k)-CA(4) micelles in mice was approximately 15 mg/kg, which was 1.5-fold higher of the MTD of free DOX. Pharmacokinetics and biodistribution studies demonstrated that both DOX-loaded micelles were able to prolong the blood retention time, preferentially accumulate and penetrate in B-cell lymphomas via the enhanced permeability and retention (EPR) effect. Finally, DOX-PEG(2k)-CA(4) micelles achieved enhanced anti-cancer efficacy and prolonged survival in Raji lymphoma bearing mice, compared to free DOX and PEGylated liposomal DOX (Doxil®) at the equivalent dose. In addition, the analysis of creatine kinase (CK) and lactate dehydrogenase (LDH) serum enzymes level indicated that DOX micellar formulations significantly reduced the cardiotoxicity associated with free DOX.

Mangiferin suppressed advanced glycation end products (AGEs) through NF-κB deactivation and displayed anti-inflammatory effects in streptozotocin and high fat diet-diabetic cardiomyopathy rats.

Given the importance of the aggregation of advanced glycation end products (AGEs) and cardiac inflammation in the onset and progression of diabetic cardiomyopathy (DCM), our objective in this study was to demonstrate the cardioprotective effect of mangiferin, an antidiabetic and anti-inflammatory agent, on diabetic rat model. The DCM model was established by a high-fat diet and a low dose of streptozotocin. DCM rats were treated orally with mangiferin (20 mg/kg) for 16 weeks. Serum and left ventricular myocardium were collected for determination of inflammatory cytokines. AGEs mRNA and protein expression of nuclear factor kappa B (NF-κB) and receptor for AGEs (RAGE) in myocardium were assayed by real-time PCR and Western blot. ROS levels were measured by dihydroethidium fluorescence staining. NF-κB binding activity was assayed by TransAM NF-κB p65 ELISA kit. Chronic treatment with mangiferin decreased the levels of myocardial enzymes (CK-MB, LDH) and inflammatory mediators (TNF-α, IL-1β). Meanwhile, NF-κB is inhibited by the reduction of nuclear translocation of p65 subunit, and mangiferin reduced AGE production and decreased the mRNA and protein expression of RAGE in DCM rats. Our data indicated that mangiferin could significantly ameliorate DCM by preventing the release of inflammatory cytokines, and inhibiting ROS accumulation, AGE/RAGE production, and NF-κB nuclear translocation, suggesting that mangiferin treatment might be beneficial in DCM.

Facile synthesis of glycosylated Fmoc amino acid building blocks assisted by microwave irradiation

The synthesis of glycosylated Fmoc amino acids by reaction of mono- and disaccharide peracetates with Fmoc amino acids having free carboxyl groups was rapidly promoted by Lewis acids (SnCl(4), BF(3)·Et(2)O) under microwave irradiation. The products are useful building blocks for the synthesis of glycopeptides.

Enhanced enteroviral infectivity via viral protease-mediated cleavage of Grb2-associated binder 1

Coxsackievirus B3 (CVB3), an important human causative pathogen for viral myocarditis, pancreatitis, and meningitis, has evolved different strategies to manipulate the host signaling machinery to ensure successful viral infection. We previously revealed a crucial role for the ERK1/2 signaling pathway in regulating viral infectivity. However, the detail mechanism remains largely unknown. Grb2‐associated binder 1 (GAB1) is an important docking protein responsible for intracellular signaling assembly and transduction. In this study, we demonstrated that GAB1 was proteolytically cleaved after CVB3 infection at G175 and G436 by virus‐encoded protease 2Apro, independent of caspase activation. Knockdown of GAB1 resulted in a significant reduction of viral protein expression and virus titers. Moreover, we showed that virus‐induced cleavage of GAB1 is beneficial to viral growth as the N‐terminal proteolytic product of GAB1 (GAB1‐N1‐174) further enhances ERK1/2 activation and promotes viral replication. Our results collectively suggest that CVB3 targets host GAB1 to generate a GAB1‐N1‐174 fragment that enhances viral infectivity, at least in part, via activation of the ERKpathway. The findings in this study suggest a novel mechanism that CVB3 employs to subvert the host signaling and facilitate consequent viral replication.—Deng, H., Fung, G., Shi, J., Xu, S., Wang, C., Yin, M., Hou, J., Zhang, J., Jin, Z.‐G., Luo, H. Enhanced enteroviral infectivity via viral protease‐mediated cleavage of Grb2‐associated binder 1. FASEB J. 29, 4523‐4531 (2015). www.fasebj.org

A novel galectin-1 inhibitor discovered through one-bead two-compound library potentiates the antitumor effects of paclitaxel in vivo

Through the one-bead two-compound (OB2C) ultra–high-throughput screening method, we discovered a new small-molecule compound LLS2 that can kill a variety of cancer cells. Pull-down assay and LC/MS-MS indicated that galectin-1 is the target protein of LLS2. Galectin-1 is known to be involved in the regulation of proliferation, apoptosis, cell cycle, and angiogenesis. Binding of LLS2 to galectin-1 decreased membrane-associated H-Ras and K-Ras and contributed to the suppression of pErk pathway. Importantly, combination of LLS2 with paclitaxel (a very important clinical chemotherapeutic agent) was found to exhibit synergistic activity against several human cancer cell lines (ovarian cancer, pancreatic cancer, and breast cancer cells) in vitro. Furthermore, in vivo therapeutic study indicated that combination treatment with paclitaxel and LLS2 significantly inhibits the growth of ovarian cancer xenografts in athymic mice. Our results presented here indicate that the OB2C combinatorial technology is a highly efficient drug screening platform, and LLS2 discovered through this method can be further optimized for anticancer drug development. Mol Cancer Ther; 16(7); 1212–23. ©2017 AACR.

Covalent Chemical Ligation Strategy for Mono- and Polyclonal Immunoglobulins at Their Nucleotide Binding Sites

Nonspecific ligation methods have been traditionally used to chemically modify immunoglobulins. Site-specific ligation of compounds (toxins or ligands) to antibodies has become increasingly important in the fields of therapeutic antibody-drug conjugates and bispecific antibodies. In this present study, we took advantage of the reported nucleotide-binding pocket (NBP) in the Fab arms of immunoglobulins by developing indole-based, 5-fluoro-2,4-dinitrobenzene-derivatized OBOC peptide libraries for the identification of affinity elements that can be used as site-specific derivatization agents against both mono- and polyclonal antibodies. Ligation can occur at any one of the few lysine residues located at the NBP. Immunoconjugates resulting from such affinity elements can be used as therapeutics against cancer or infectious agents.