Jingjing Song

Novel mode of action of polybia-MPI, a novel antimicrobial peptide, in multi-drug resistant leukemic cells.

As the frequent emergency of resistant tumor cells during treatment, the development of new agents with new modes of action attracts a great deal of interest. Polybia-MPI was a short cationic alpha-helical amphiphilic peptide that has selective toxicity toward cancer cells but no hemolytic activity. Its target selectivity is based on the binding preference to membranes containing anionic phospholipids by electrostatic driving. Its ability to make PI and trypan blue permeate into tumor cells at the same rate (within minutes), suggests a killing mechanism that involves plasma membrane perturbation. SEM and confocal microscopy experiments verified that the cell died as a result of acute injury and bursting, suggesting necrosis. As compared to the conventional chemotherapy, polybia-MPI targets at the cell membrane rather than enters into the cell to exert its action. So it is difficult for tumor cells to develop resistance to polybia-MPI during treatment and its action is not affected by the common multi-drug resistant mechanism. Although this is an initial study that looked at its in vitro activity rather than the in vivo activity, with the increasing resistance of conventional chemotherapy, polybia-MPI may offer a novel therapeutic strategy in the treatment of multi-drug resistant cancer.

Design of Acid-Activated Cell Penetrating Peptide for Delivery of Active Molecules into Cancer Cells

TP10-5 (TK) was screened as the most promising candidate among the designed analogues of transportan 10 (TP10), a cell penetrating peptide (CPP) with remarkable capacity for membrane translocation. However, low levels of specificity and high toxicity limit its successful use for drug delivery applications. Here, we developed a new type of acid-activated CPP (TH) by replacement of all lysines of TK with histidines. As expected, histidine-containing TH can be activated and subsequently enter cells at pH 6.0, whereas it is less active at pH 7.4. In contrast, the uptake of TK has no significant difference for both pH values. Importantly, the toxicity of TH is significantly lower than that of TK under physiological conditions. After attachment of camptothecin (CPT) to TH, this conjugate exhibited remarkable cytotoxicity to cancer cells in a pH-dependent manner compared with free CPT and TK-CPT. This study opens a new avenue to design CPPs that preferentially enter cells in acidic solid tumors, with minimal cellular uptake in normal tissues.

Two Hits Are Better than One: Membrane Active and DNA Binding Related Double Action Mechanism of NK-18, a Novel Antimicrobial Peptide Derived from Mammalian NK-lysin

ABSTRACT The extensive use and misuse of antibiotics in medicine result in the emergence of multidrug-resistant bacteria, creating an urgent need for the development of new chemotherapeutic agents. Nowadays, antimicrobial peptides are widely recognized as a class of promising candidates with activity against multidrug-resistant bacteria. NK-18 is a truncated peptide derived from NK-Lysin, an effector of cytotoxic T cells and natural killer cells. In this study, we studied the antibacterial mechanism of action of NK-18. The results revealed that NK-18 has potent antibacterial activity against Escherichia coli and Staphylococcus aureus. According to our findings, NK-18 is membrane active and its target of action is not only the bacterial membrane but also the DNA in the cytoplasm. The double targets of NK-18 make it difficult for bacteria to generate resistance, which may present a new strategy to defend against multidrug-resistant bacteria and provide a new lead in the design of potent antimicrobial peptides with therapeutic application in the presence of increasing resistance to conventional antibiotics.

Membrane active antitumor activity of NK-18, a mammalian NK-lysin-derived cationic antimicrobial peptide

As the increasing emergence of multi-drug resistant tumor cells, there is an urgent need for developing new chemotherapeutic agents. NK-lysin was a novel effector of cytotoxic T cells and natural killer (NK) cells and had broad antimicrobial activity. In this study, we developed a core region of NK-lysin termed NK-18, and studied its antitumor activity and possible action mode. Our results showed that NK-18 (with 18 amino acids) possesses potent antitumor activity against bladder and prostate cancer cells by disrupting the integrity of cell membrane, but has negligible hemolysis activity against mouse erythrocytes. In addition, CD spectra was employed to study its conformation in membrane mimicking environment. NK-18 takes a standard α-helical conformation in membrane mimicking environment, which could be accounted for its more potent antitumor activity compared with its low α-helical content homologous derivatives. These findings together with its shorter amino acid sequence and lower synthesis cost suggest that NK-18 could present an alternative therapeutic strategy to cancer chemotherapy and play a promising role in fighting the multi-drug resistant tumors.

A novel analog of antimicrobial peptide Polybia-MPI, with thioamide bond substitution, exhibits increased therapeutic efficacy against cancer and diminished toxicity in mice.

Polybia-MPI (MPI), a short cationic α-helical antimicrobial peptide, exhibited excellent anticancer activity and selectivity in vitro in our previous studies. To improve its in vivo application, we synthesized an analog (MPI-1) of MPI by replacing the C terminal amide -[CO-NH(2)] with thioamide -ψ[CS-NH(2)]. Although there is just one atom difference, the MPI-1 exhibited some surprising properties. In vitro studies revealed that MPI-1 exhibited relatively high lytic activity over MPI, whereas its stability to enzymatic degradation in serum was improved remarkably. Despite the enhanced toxicity in vitro, MPI-1 exhibited significantly lower mortality to mice than MPI at 75 mg/kg. Importantly, in vivo anticancer activity study indicated that MPI-1 could remarkably suppress the growth of sarcoma xenograft tumors more efficiently than MPI. Therefore, the significantly improved anticancer activity and predominantly lower in vivo toxicity might allow MPI-1 to be a good candidate for future anticancer treatment.

Membrane-active action mode of Polybia-CP, a novel antimicrobial peptide isolated from the venom of Polybia Paulista

ABSTRACT The extensive use of antibiotics in medicine, the food industry, and agriculture has resulted in the frequent emergence of multidrug-resistant bacteria, which creates an urgent need for new antibiotics. It is now widely recognized that antimicrobial peptides (AMPs) could play a promising role in fighting multidrug-resistant bacteria. Antimicrobial peptide polybia-CP was purified from the venom of the social wasp Polybia paulista. In this study, we synthesized polybia-CP and studied its action mode of antibacterial activity. Our results revealed that polybia-CP has potent antibacterial activity against both Gram-positive and Gram-negative bacteria. The results from both the real bacterial membrane and the in vitro model membrane showed that polybia-CP is membrane active and that its action target is the membrane of bacteria. It is difficult for bacteria to develop resistance to polybia-CP, which may thus offer a new strategy for defending against resistant bacteria in medicine and the food and farming industries.

Cellular uptake of transportan 10 and its analogs in live cells: Selectivity and structure-activity relationship studies.

Transportan 10 (TP10) is an amphipathic cell-penetrating peptide with high translocation ability. In order to obtain more details of structure-activity relationship of TP10, we evaluated the effects of structure and charge on its translocation ability. Our results demonstrated that disrupting the helical structure or Arg substitution could remarkably decrease the cellular uptake of TP10. However, increasing the number of positive charge was an effective strategy to enhance translocation ability of TP10. Furthermore, the molecular dynamics simulation supported the results derived from experiments, suggesting that higher membrane disturbance leads to higher cellular uptake of peptides. In addition, our study also demonstrated TP10 and its analogs preferentially entered cancer cells rather than normal cells. The uptake selectivity toward cancer cells makes TP10 and its analogs as potent CPPs for drug delivery.

Anticancer effects of a novel class rosin-derivatives with different mechanisms.

In this Letter, the anticancer activity of novel rosin-derivatives introducing indicated side chains at position C18 of dehydroabietic acid (DHAA) was reported. Gratifyingly, all of these derivatives showed significantly cytotoxicity toward diverse human carcinoma cell lines. We found the compound 4 could induce cell membrane damage at high concentration as well as cell apoptosis at low concentration. However, compound 5, attachment of quinidine to dehydroabietic acid via thiourea bond, only induced apoptotic cell death. In addition, all these active compounds induced apoptosis mainly through mitochondrial-dependent pathway. Interestingly, compound 5 exhibited the highest anticancer activity and little toxicity to normal cells compared with the other derivatives. Therefore, 5 merits further investigation as a potential agent for future anticancer treatment.

Design of an acid-activated antimicrobial peptide for tumor therapy

Antimicrobial peptides have received increasing attention as potential antitumor drugs due to their new mode of action. However, the systemic toxicity at high concentration always hampers their successful utilization for tumor therapy. Here, we designed a new type of acid-activated antimicrobial peptide AMitP by conjugating antimicrobial peptide MitP to its anionic binding partner MitPE via a disulfide linker. Compared with MitP, AMitP displayed significant antitumor activity at acidic pH and low cytotoxicity at normal pH. The results of MD simulations demonstrate that the changes of structure and membrane binding tendency of AMitP at different pH values played an important role in its pH-dependent antitumor activity. In addition, AMitP showed significant enzymatic stability compared with MitP, suggesting a potential for in vivo application. In short, our work opens a new avenue to develop antimicrobial peptides as potential antitumor drugs with high selectivity.

Cell penetrating peptide TAT can kill cancer cells via membrane disruption after attachment of camptothecin.

Attachment of traditional anticancer drugs to cell penetrating peptides is an effective strategy to improve their application in cancer treatment. In this study, we designed and synthesized the conjugates TAT-CPT and TAT-2CPT by attaching camptothecin (CPT) to the N-terminus of the cell penetrating peptide TAT. Interestingly, we found that TAT-CPT and especially TAT-2CPT could kill cancer cells via membrane disruption, which is similar to antimicrobial peptides. This might be because that CPT could perform as a hydrophobic residue to increase the extent of membrane insertion of TAT and the stability of the pores. In addition, TAT-CPT and TAT-2CPT could also kill cancer cells by the released CPT after they entered cells. Taken together, attachment of CPT could turn cell penetrating peptide TAT into an antimicrobial peptide with a dual mechanism of anticancer action, which presents a new strategy to develop anticancer peptides based on cell penetrating peptides.