Anticancer potency of small linear and cyclic tetrapeptides and pharmacokinetic investigations of peptide binding to human serum albumin.

We have in the present study explored the anticancer activity against human Burkitt's lymphoma cells (Ramos) of a series of small linear and cyclic tetrapeptides containing a ß2,2-amino acid with either two 2-naphthyl-methylene or two para-CF3-benzyl side chains, along with their interaction with the main plasma protein human serum albumin (HSA). The cyclic and more amphipathic tetrapeptides revealed a notably higher anticancer potency against Ramos cells [50% inhibitory concentration (IC50) 11­70 µM] compared to the linear tetrapeptide counterparts (IC50 18.7 to >413 µM). The most potent cyclic tetrapeptide c3 had a 16.5-fold preference for Ramos cells compared to human red blood cells, whereas the cyclic tetrapeptide c1 both showed low hemolytic activity and displayed the overall highest (2.9-fold) preference for Ramos cells (IC50 23 µM) compared to healthy human lung fibroblast cells (MRC-5). Investigating the interaction of selected tetrapeptides and recently reported hexapeptides with HSA revealed that the peptides bind to drug site II of HSA in the 22­28 µM range, disregarding size and overall structure. NMR and in silico molecular docking experiments identified the lipophilic residues as responsible for the interaction, but in vitro studies showed that the anticancer potency of the peptides varied in the presence of HSA and that c3 remained the most potent peptide. Based on our findings, we call for implementing serum albumin binding in development of anticancer peptides, as it may have implications for future administration and systemic distribution of peptide-based cancer drugs.

Synthesis of anticancer heptapeptides containing a unique lipophilic ß(2,2) -amino acid building block.

We report a series of synthetic anticancer heptapeptides (H-KKWß(2,2) WKK-NH(2)) containing eight different central lipophilic ß(2,2) -amino acid building blocks, which have demonstrated high efficiency when used as scaffolds in small cationic antimicrobial peptides and peptidomimetics. The most potent peptides in the present study had IC(50) values of 9-23 µm against human Burkitt's lymphoma and murine B-cell lymphoma and were all nonhaemolytic (EC(50) > 200 µm). The most promising peptide 10e also demonstrated low toxicity against human embryonic lung fibroblast cells and peripheral blood mononuclear cells and exceptional proteolytic stability.

Improved anticancer potency by head-to-tail cyclization of short cationic anticancer peptides containing a lipophilic ß(2,2) -amino acid.

We have recently reported a series of synthetic anticancer heptapeptides (H-KKWß(2,2) WKK-NH(2) ) containing a central achiral and lipophilic ß(2,2) -amino acid that display low toxicity against non-malignant cells and high proteolytic stability. In the present study, we have further investigated the effects of increasing the rigidity and amphipathicity of two of our lead heptapeptides by preparing a series of seven to five residue cyclic peptides containing the two most promising ß(2,2) -amino acid derivatives as part of the central lipophilic core. The peptides were tested for anticancer activity against human Burkitt's lymphoma (Ramos cells), haemolytic activity against human red blood cells (RBC) and cytotoxicity against healthy human lung fibroblast cells (MRC-5). The results demonstrated a considerable increase in anticancer potency following head-to-tail peptide cyclization, especially for the shortest derivatives lacking a tryptophan residue. High-resolution NMR studies and molecular dynamics simulations together with an annexin-V-FITC and propidium iodide fluorescent assay showed that the peptides had a membrane disruptive mode of action and that the more potent peptides penetrated deeper into the lipid bilayer. The need for new anticancer drugs with novel modes of action is demanding, and development of short cyclic anticancer peptides with an overall rigidified and amphipathic structure is a promising approach to new anticancer agents.

Use of Selective Serotonin Reuptake Inhibitors - Validity of Self-Report versus Plasma Concentrations and Pharmacy Dispensations - A Cross-Sectional Analysis of the Norwegian Women and Cancer Study.

Purpose: To validate self-reported current use of selective serotonin reuptake inhibitors (SSRI) in the Norwegian Women and Cancer study (NOWAC) and to identify factors associated with discordance between data sources. Material and Methods: This is a cross-sectional record-linkage study comparing SSRI-use derived from four data sources: 1) Specific SSRI questions in the main NOWAC questionnaire, 2) Open questions on medication use in the small questionnaire following blood samples, 3) plasma concentration measurements for a subsample, and 4) pharmacy dispensations from the Norwegian prescription database (NorPD) where current use of SSRI was defined by Legend Time Duration (LTD). Among 105 855 women, aged 46 to 64 years and randomly selected from the general population, 70,191 had data on SSRI-use from both NOWAC and NorPD. Plasma concentration was measured for 93 pairs of self-reported SSRI-users and non-users, with dispensation data available for 68 pairs. Validity was assessed by sensitivity and specificity; agreement was assessed by Cohen's kappa. Factors associated with discordance between information sources were analyzed by multiple binary logistic regression. Results: We found high sensitivity (89.5%) and specificity (98.7%) for the specific questions in the main questionnaire compared with pharmacy dispensations. Measured against plasma concentrations, current SSRI-use defined by open questions and pharmacy dispensations both had high sensitivity (100% and 92.5%, respectively) and specificity (98.6% both). Agreements (kappa) were similarly high for all comparisons (≥0.80). The factors associated with discordance between data sources included poor health, comorbidity, being single and not being in full time work. Education was inversely associated with discordance. Conclusion: Self-reported current use of SSRI from the NOWAC questionnaires is highly valid and, according to plasma concentrations, perhaps even more so than pharmacy dispensations. Factors associated with discordance between information sources should be taken into account in the interpretation of future analyses which include SSRI-use in the NOWAC study.

Covalent analogues of nucleobase-pairs.

Covalently linked base pairs analogues consisting of purine-purine or purine-pyrimidine conjugates linked by carbon linkages of diverse length and configuration (ethylene, vinylene, acetylene and phenylene) were prepared.

Anticancer activity of small amphipathic ß²,²-amino acid derivatives.

We report the anticancer activity from screening of a series of synthetic ß(2,2)-amino acid derivatives that were prepared to confirm the pharmacophore model of short cationic antimicrobial peptides with high anti-Staphylococcal activity. The most potent derivatives against human Burkitt's lymphoma (Ramos) cells displayed IC(50) values below 8 µM, and low toxicity against human red blood cells (EC(50) > 200 µM). A more than 5-fold preference for Ramos cancer cells compared to human lung fibroblasts (MRC-5 cells) was also obtained for the most promising ß(2,2)-amino acid derivative 3-amino-N-(2-aminoethyl)-2,2-bis(naphthalen-2-ylmethyl)propanamide (5c). Screening of 5c at the National Cancer Institute (NCI, USA) confirmed its anticancer potency and revealed a very broad range of anticancer activity with IC(50) values of 0.32-3.89 µM against 59 different cancer cell lines. Highest potency was obtained against the colon cancer cell lines, a non-small cell lung cancer, a melanoma, and three leukemia cell lines included in the NCI screening panel. The reported ß(2,2)-amino acid derivatives constitute a promising new class of anticancer agents based on their high anticancer potency, ease of synthesis, mode-of-action, and optimized pharmacokinetic properties compared to much larger antimicrobial peptides.

Synthesis of cationic antimicrobial ß(2,2)-amino acid derivatives with potential for oral administration.

We have prepared a series of highly potent achiral cationic ß(2,2)-amino acid derivatives that fulfill the Lipinski's rule of five and that contain the basic structural requirements of short cationic antimicrobial peptides. Highest antimicrobial potency was observed for one of the smallest ß(2,2)-amino acid derivatives (M(w) 423.6) exhibiting a MIC of 3.8 µM against methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE), and Staphylococcus aureus, and 7.7 µM against Escherichia coli. The ß(2,2)-amino acid derivatives were shown to have similar absorption properties as several commercially available drugs, and the results implied a resembling membrane disrupting mechanism of action as reported for much larger cationic antimicrobial peptides. By their high potency, nontoxicity, absorption properties, and ease of synthesis, the ß(2,2)-amino acid derivatives demonstrate a way to modify a vastly investigated class of cationic antimicrobial peptides into small drug-like molecules with high commercial potential.

Antimicrobial activity of small beta-peptidomimetics based on the pharmacophore model of short cationic antimicrobial peptides.

We have synthesized a series of small beta-peptidomimetics (M(w) <650) that were based on the minimal pharmacophore model for anti-Staphylococcal activity of short cationic antimicrobial peptides. All beta-peptidomimetics had a net charge of +2 and formed an amphipathic scaffold consisting of an achiral lipophilic beta(2,2)-amino acid coupled to a C-terminal l-arginine amide residue. By varying the lipophilic side-chains of the beta(2,2)-amino acids, we obtained a series of highly potent beta-peptidomimetics with high enzymatic stability against alpha-chymotrypsin and a general low toxicity against human erythrocytes. The most potent beta-peptidomimetics displayed minimal inhibitory concentrations of 2.1-7.2 muM against Staphylococcus aureus, methicillin resistant Staphylococcus aureus (MRSA), methicillin resistant Staphylococcus epidermidis (MRSE), and Escherichia coli. Small amphipathic beta-peptidomimetics may be a promising class of antimicrobial agents by means of having a similar range of potency and selectivity as larger cationic antimicrobial peptides in addition to improved enzymatic stability and lower costs of production.