Antitumor Enediyne Chromoprotein C-1027: Mechanistic Investigation of the Chromophore-Mediated Self-Decomposition Pathway

An arginine-rich cell penetrating peptide contained anti-gelatinase scFv-LDM fusion protein shows potent antitumor efficacy in pancreatic cancer

Pancreatic cancer (PC) is one of the most dangerous cancers with less than 5% survival rate in 5 years. This study was to evaluate the antitumor activities of dFv-LDP-AE and dFv-R-LDP-AE, two energized fusion protein targeting gelatinases, on pancreatic cancer. The fusion protein dFv-LDP-AE consists of two tandem anti-gelatianses scFv and an enediyne antibiotic lidamycin (LDM) for receptor binding and cell killing. To improve the penetration capability, the fusion protein dFv-LDP-AE was integrated with an arginine-rich cell penetrating peptide (Arg)₉ and then generated the fusion protein dFv-R-LDP-AE. The current study demonstrated that dFv-LDP and dFv-R-LDP had high affinity with the antigen gelatinases and PC cells, the integration of (Arg)₉ could increase the penetration rate of fusion protein in SW-1990 and PANC-1 cells. After enediyne-energized with chromophore of lidamycin, the energized fusion protein dFv-LDP-AE and dFv-R-LDP-AE showed potent cytotoxicity to PC cells and could induced the robust cell apoptosis and necrosis in vitro. Western blot showed that dFv-R-LDP-AE could increase PARP cleavage, and inhibited the expression of VEGF, Cyclin D1, Cox-2 and Bcl-2 in SW-1990 and PANC-1 cells. In vivo, at a tolerated dosage, dFv-LDP, dFv-LDP-AE and dFv-R-LDP-AE inhibited tumor growth by 20.42%, 56.31% (P < 0.01, compared to that of control) and 74.2% (P < 0.05, compared to that of dFv-LDP-AE) in pancreatic cancer SW-1990 xenografted mice, respectively. Moreover, the results of in vivo optical imaging showed that fusion protein dFv-R-LDP displayed prominent accumulation in the tumor in SW-1990 xenografted mice and Capan-2 orthotopic transplanted mice. These results showed that dFv-R-LDP-AE possessed potent antitumor efficacy on PC, which indicating it could be a promising candidate for targeting therapy of PC.

Total synthesis and related studies of large, strained, and bioactive natural products

Our chemical syntheses and related scientific investigations of natural products with complex architectures and powerful biological activities are described, focusing on the very large 3 nm-long polycyclic ethers called the ciguatoxins, highly strained and labile chromoprotein antitumor antibiotics featuring nine-membered enediyne cores, and extremely potent anthelmintic macrolides called the avermectins.

The novel structure make LDM effectively remove CD123+ AML stem cells in combination with interleukin 3

CD123 became a therapeutic target for acute myelocytic leukemia(AML) because of its overexpression only on AML stem cells. It is α subunit of interleukin-3 (multi-CSF, IL3) receptor. Lidamycin(LDM) is a novel antibiotic composed of an apoprotein (LDP) and a chromophore (AE). We cloned, expressed and isolated IL3LDP fusion protein first then assembled with AE in vitro. We found that131/132 amino acids of IL3 were the key factors for IL3 fusion protein stability and I131L/F132L mutation effectively improved the IL3 fusion protein stability. The toxicity of IL3LDM to CD123+ tumor cells was 2-10 times compared to LDM alone and 10000 times compared to ADR. Meanwhile, IL3LDM impaired the colony-forming ability of CD123+ stem-like cells but not to CD123 negative normal cord blood cells. Three drug delivery methods in vivo were adopted: prophylactic treatment and single/multiple-dosing administration. The tumor-free survival extended to 120 d and cancer cell invasion significantly decreased after IL3LDM continuous multiple treated. Moreover, IL3LDM had been shown to modulate apoptosis by arrested cell cycle in G2/M phase. Therefore, IL3LDM is expected to be a new drug for leukemia target therapy.

Site-specific PEGylation of lidamycin and its antitumor activity

In this study, N-terminal site-specific mono-PEGylation of the recombinant lidamycin apoprotein (rLDP) of lidamycin (LDM) was prepared using a polyethyleneglycol (PEG) derivative (M_w 20 kDa) through a reactive terminal aldehyde group under weak acidic conditions (pH 5.5). The biochemical properties of mPEG-rLDP-AE, an enediyne-integrated conjugate, were analyzed by SDS-PAGE, RP-HPLC, SEC-HPLC and MALDI-TOF. Meanwhile, in vitro and in vivo antitumor activity of mPEG-rLDP-AE was evaluated by MTT assays and in xenograft model. The results indicated that mPEG-rLDP-AE showed significant antitumor activity both in vitro and in vivo. After PEGylation, mPEG-rLDP still retained the binding capability to the enediyne AE and presented the physicochemical characteristics similar to that of native LDP. It is of interest that the PEGylation did not diminish the antitumor efficacy of LDM, implying the possibility that this derivative may function as a payload to deliver novel tumor-targeted drugs.

Binding of a biosynthetic intermediate to AtrA modulates the production of lidamycin by Streptomyces globisporus

The control of secondary production in streptomycetes involves the funneling of environmental and physiological signals to the cluster-situated (transcriptional) regulators (CSRs) of the biosynthetic genes. For some systems, the binding of biosynthetic products to the CSR has been shown to provide negative feedback. Here we show for the production of lidamycin (C-1027), a clinically relevant antitumor agent, by Streptomyces globisporus that negative feedback can extend to a point higher in the regulatory cascade. We show that the DNA-binding activity of the S. globisporus orthologue of AtrA, which was initially described as a transcriptional activator of actinorhodin biosynthesis in S. coelicolor, is inhibited by the binding of heptaene, a biosynthetic intermediate of lidamycin. Additional experiments described here show that S. globisporus AtrA binds in vivo as well as in vitro to the promoter region of the gene encoding SgcR1, one of the CSRs of lidamycin production. The feedback to the pleiotropic regulator AtrA is likely to provide a mechanism for coordinating the production of lidamycin with that of other secondary metabolites. The activity of AtrA is also regulated by actinorhodin. As AtrA is evolutionarily conserved, negative feedback of the type described here may be widespread within the streptomycetes.

A tandem scFv-based fusion protein and its enediyne-energized analogue show intensified therapeutic efficacy against lung carcinoma xenograft in athymic mice

Gelatinases play important roles in tumor progression and are abundantly expressed in a variety of malignant tumors. Antibody targeting gelatinases is a possible avenue to fight against cancer. However, antibody alone can not achieve curative efficacy. Herein, we demonstrated the intensified targeting therapy of a tandem scFv-based fusion protein and its enediyne-energized analogue against gelatinases-overexpressed tumor. A fusion protein dFv-LDP, comprising a tandem scFv of anti-gelatinases linked to the apoprotein (LDP) of lidamycin, was generated and showed strong tumor targeting capability in three different tumor xenografts. In PG-BE1 lung carcinoma xenograft, the tumor inhibition rate was 77.5% by dFv-LDP versus 94.2% by dFv-LDP-AE, the product of dFv-LDP assembled with the active enediyne chromophore (AE) of lidamycin. Moreover, the combination of dFv-LDP with dFv-LDP-AE further augmented the therapeutic efficacy, producing initial tumor shrinkage in five of six mice. The microvessel density (P<0.05) and proliferation index (P<0.05) were also stepwise decreased in groups of dFv-LDP, dFv-LDP-AE and the combination. In conclusion, our results demonstrated that the antibody-based therapy against gelatinases was stepwise intensified in use of dFv-LDP, dFv-LDP-AE and dFv-LDP plus dFv-LDP-AE, and indicated that the combination of an antibody with its drug-armed analogue might be of interest as a new approach to augment antitumor efficacy.

Disruption of cagA, the apoprotein gene of chromoprotein antibiotic C-1027, eliminates holo-antibiotic production, but not the cytotoxic chromophore

C-1027 is a chromoprotein of the nine-membered enediyne antitumour antibiotic family, comprising apoprotein to stabilize and transport the enediyne chromophore. The disruption of apoprotein gene cagA within the C-1027 biosynthetic gene cluster abolished C-1027 holo-antibiotic production detected by an antibacterial assay, as well as the expression of the apoprotein and C-1027 chromophore extracted following protein precipitation of the culture supernatant. Complementation of the cagA-disrupted mutant AKO with the intact cagA gene restored C-1027 production, suggesting that cagA is indispensable for holo-antibiotic production. Overexpression of cagA in the wild-type strain resulted in a significant increase in C-1027 production as expected. Surprisingly, electrospray ionization (ESI)-MS and ESI-MS/MS analyses suggested that the AKO mutant still produced the C-1027 enediyne chromophore [m/z=844 (M+H)(+)] and its aromatized product [m/z=846 (M+H)(+)]. Consistent with this, the results from gene expression analysis using real-time reverse transcriptase-PCR showed that transcripts of the positive regulator sgcR3 and the structural genes sgcA1, sgcC4, sgcD6 and sgcE were readily detected in the AKO mutant as well as in the wild-type and the complementation strain. These results provided, for the first time, evidence suggesting that the apoprotein of C-1027 is not essential in the self-resistance mechanism for the enediyne chromophore.

DNA damage-site recognition by lysine conjugates

Simple lysine conjugates are capable of selective DNA damage at sites approximating a variety of naturally occurring DNA-damage patterns. This process transforms single-strand DNA cleavage into double-strand cleavage with a potential impact on gene and cancer therapy or on the design of DNA constructs that require disassembly at a specific location. This study constitutes an example of DNA damage site recognition by molecules that are two orders of magnitude smaller than DNA-processing enzymes and presents a strategy for site-selective cleavage of single-strand nucleotides, which is based on their annealing with two shorter counterstrands designed to recreate the above duplex damage site.

Protein–Small Molecule Interactions in Neocarzinostatin, the Prototypical Enediyne Chromoprotein Antibiotic

The enediyne chromoproteins are a class of potent antitumour antibiotics comprising a 1:1 complex of a protein and a noncovalently bound chromophore. The protein is required to protect and transport the highly labile chromophore, which acts as the cytotoxic component by reacting with DNA leading to strand cleavage. A derivative of the best-studied member of this class, neocarzinostatin (NCS), is currently in use as a chemotherapeutic in Japan. The application of the chromoproteins as therapeutics along with their unique mode of action has prompted widespread interest in this area. Notable developments include the discovery of non-natural ligands for the apoproteins and the observation that multiple binding modes are available for these ligands in the binding site. Mutation studies on the apoproteins have revealed much about their stability and variability, and the application of an in vitro evolution method has conferred new binding specificity for unrelated ligands. These investigations hold great promise for the application of the apoproteins for drug-delivery, transport and stabilisation systems.