D-Amino Acid Analogues of the Antimicrobial Peptide CDT Exhibit Anti- Cancer Properties in A549, a Human Lung Adenocarcinoma Cell Line.

INTRODUCTION: The importance of the antitumor activity of some antimicrobial peptides (AMPs) is being increasingly recognized. The antimicrobial peptide, tachyplesin, has been shown to exhibit anticancer properties and a linear, cysteine deleted analogue (CDT), was found to retain its antibacterial function. OBJECTIVES: The objective was to test CDT and related analogues against normal mammalian, bacterial, and cancer cells to determine their effectiveness and then utilize specific assays to determine a possible mechanism of action. METHODS: We used sequence reversal and D-amino acids to synthesize four CDT analogues by solid phase peptide synthesis. A number of assays were used including liposome dye-leakage, antibacterial activity against both Gram-positive and Gram-negative bacterial strains, hemolytic assays, methyl thiazolyl tetrazolium (MTT), and apoptosis to examine their effectiveness as both AMPs and anti-cancer peptides (ACPs). We then tested the analogues for their ability to inhibit proliferation of the human lung cancer cell line, A549. RESULTS: We found that D-CDT exhibited the best bactericidal properties of those tested and was not damaging to red blood cells. Both D-CDT and reverse D-CDT showed a dose-dependent reduction of cell viability. However, D-CDT was most effective with an IC50 of 9.814 µM, a value 9-fold lower than that calculated for reverse D-CDT (90.16 µM). Apoptosis does not appear to be a mechanism by which D-CDT exerts its anticancer properties since > 100 µM was required to increase activation of caspase 3. Moreover, the ERK1/2 pathway is also unlikely since only a modest (20%) decrease of activity was observed with > 100 µM D-CDT. However, D-CDT was found to operate via a hyaluronan (HA)-dependent mechanism as pretreatment of the cells with hyaluronidase decreased the cytotoxic effects of D-CDT on A549 cells and increased its IC50 29-fold to 283.9 µM. CONCLUSION: D-CDT is both an effective AMP and ACP, and likely exerts its anticancer effects through both membranolytic as well as an HA-mediated mechanism.

Simultaneous detection of ultraviolet B-induced DNA damage using capillary electrophoresis with laser-induced fluorescence.

An immunoassay based on CE-LIF was developed for the simultaneous detection of cyclobutane pyrimidine dimers (CPDs) and pyrimidine 6-4 pyrimidone photoproducts (6-4PPs) in genomic DNA irradiated with UVB or natural sunlight. Human cells were first exposed to varying amounts of UVB or natural sunlight to induce DNA damage. Genomic DNA was extracted and incubated with anti-CPD and anti-6-4PP primary antibodies attached to secondary antibodies with a fluorescent quantum dot (QD) reporter that emitted either red or yellow fluorescence. CE was used to separate the unbound antibodies from those bound to the photoproducts, and LIF with appropriate optical filters was used to separate the fluorescence signals from each QD to individual photomultiplier tubes for simultaneous photoproduct detection. Using this strategy, photoproducts were detected from ∼6 ng (200 ng µL(-1)) of DNA under a low UVB fluence of 65 J m(-2) for CPDs or 195 J m(-2) for 6-4PPs. This assay was also the first to demonstrate the detection of CPDs in human cells after only 15 min of irradiation under natural sunlight.

Characterization of a cyclodextrinoligonucleotide complex by capillary electrophoresis using laser-induced fluorescence.

PURPOSE: Cyclodextrins (CDs) have been identified as a viable alternative to viral vectors for use in therapeutic applications. Here, the stability of the complex formed between the a multiply charged, cationic, fully substituted heptakis-(6-amino-2-galactosyl)cyclodextrin (BCDX12) with a multiply charged 12-mer hexachlorofluorescein tagged arabinopolynucleotide (Hex-PAH) have been evaluated. METHODS: The stability of complexes of Hex-PAH and BCD-X12 was studied with respect to mole ratio (1:1, 1:2, and 1:5 Hex-PAH:BCD-X12), pH, buffer concentration, temperature, and agitation using capillary electrophoresis with laser induced fluorescence detection (CE/LIF). Two neutral CDs and an additional cationic CD were also tested under the same analytical conditions to determine their ability to form complexes. RESULTS: Hex-PAH:BCDX12 complexes at mole ratios of 1:2 were stable in 10 mM (160 mM total borate concentration) sodium tetraborate buffer at pH 7.5 and at temperatures of 4 degrees C and 25 degrees C over 48 hours. However, the Hex-PAH:BCD-X12 complex was less stable at 37 degrees C and at higher buffer concentrations and pH values. Strong vortex mixing prior to analysis was found to disrupt the complex. Of the four CDs tested for their ability to complex with Hex-PAH, only BCDX12 formed stable complexes with Hex-PAH under the test conditions. CONCLUSIONS: Capillary electrophoresis was found to be well suited to test the stability of cyclodextrin-nucleotide complexes. CE/LIF indicated that only a single Hex- PAH:BCD-X12 complex was formed at all formulation ratios, and that the complexes were electrophoretically identical to each other, and increasing the molar ratio beyond 1:2 did not contribute measurably to complex stability. Storage temperature and agitation conditions were found to influence complex stability. Since no stable complexes were formed with neutral cyclodextrins, the results support the hypothesis of a 'charge associated' complex rather than an inclusion complex, although inclusion complexes cannot be excluded on the basis of these studies.

Assays for cytokines using aptamers.

Aptamers are short nucleic acid sequences that are used as ligands to bind their targets with high affinity. They are generated via the combinatorial chemistry procedure systematic evolution of ligands by exponential enrichment (SELEX). Aptamers have shown much promise towards detection of a variety of protein targets, including cytokines. Specifically, for the determination of cytokines and growth factors, several assays making use of aptamers have been developed, including aptamer-based enzyme-linked immunosorbent assays, antibody-linked oligonucleotide assay, fluorescence (anisotropy and resonance energy transfer) assays, and proximity ligation assays. In this article, the concept of aptamer selection using SELEX and the assay formats using aptamers for the detection of cytokines are discussed.

Study of binding stoichiometries of the human immunodeficiency virus type 1 reverse transcriptase by capillary electrophoresis and laser-induced fluorescence polarization using aptamers as probes.

Binding stoichiometries between four DNA aptamers (RT12, RT26, RTlt49, and ODN93) and the reverse transcriptase (RT) of the type 1 human immunodeficiency virus (HIV-1) were studied using affinity CE (ACE) coupled with LIF polarization and fluorescence polarization (FP). The ACE/LIF study showed evidence of two binding stoichiometries between the HIV-1 RT protein and aptamers RT12, RT26, and ODN93, suggesting that these aptamers can bind to both the p66 and p51 subunits of the HIV-1 RT. Only one binding stoichiometry for aptamer RTlt49 was found. The affinity complexes were easily separated from the unbound aptamers; however, the different stoichiometries were not well resolved. A complementary technique, FP, was able to provide additional information about the binding and supporting evidence for the ACE/LIF results. The ACE/LIFP study also revealed that the FP values of the 1:1 complexes of the HIV-1 RT protein with aptamers RT12, RT26, and ODN93 were always much greater than those of the 1:2 complexes. This was initially surprising because the larger molecular size of the 1:2 complexes was expected to result in higher FP values than the corresponding 1:1 complexes. This phenomenon was probably a result of fluorescence resonance energy transfer between the two fluorescent molecules bound to the HIV-1 RT protein.