Release of hydrophobic anticancer drug from a newly designed self-assembling peptide

A newly designed self-assembling peptide, P4 (Ac-NH-LDLKLELKLDLKLELK-CONH(2)), capable of stabilizing hydrophobic compounds in aqueous solution has been discovered. The ionic self-complementary peptide P4 has 16 amino acids, ～5 nm in size, with an alternating polar and non-polar pattern. Circular dichroism analysis demonstrated that P4 forms stable β-sheet structures, and self-assembles into nanofibers, which was demonstrated by atomic force microscopy. These nanofibers can form a scaffold hydrogel consisting of >99% water. It showed that the P4 hydrogel had stable hydrogel rheological properties. The ability of the peptide to stabilize the hydrophobic anticancer agent ellipticine was tested in this research. The results showed that the state of ellipticine in the complexes was dependent on the concentration of the peptide, which also affected the size and morphology of the complex. The anticancer activity of the complexes was studied by testing the viability with a MTT assay and a LIVE/DEAD Viability/Cytotoxicity kit in two cancer cell lines including SMMC7721 and EC9706. The viability results showed that complexes of protonated ellipticine could significantly reduce the viability of the two cell lines. The results described herein provide further incentives for basic studies on self-assembling peptide-based delivery of hydrophobic anticancer drugs.     

A photocrosslinking assay for reporting protein interactions in polyketide and fatty acid synthases

Understanding protein-protein interactions that occur between ACP and KS domains of polyketide synthases and fatty acid synthases is critical to improving the scope and efficiency of combinatorial biosynthesis efforts aimed at producing non-natural polyketides. Here, we report a facile strategy for rapidly reporting such ACP-KS interactions based on the incorporation of an amino acid with photocrosslinking functionality. Crucially, this photocrosslinking strategy can be applied to any polyketide or fatty acid synthase regardless of substrate specificity, and can be adapted to a high-throughput format for directed evolution studies.     

Resonance assignments and secondary structure prediction of the As(III) metallochaperone ArsD in solution

ArsD is a metallochaperone that delivers As(III) to the ArsA ATPase, the catalytic subunit of the ArsAB pump encoded by the arsRDABC operon of Escherichia coli plasmid R773. Conserved ArsD cysteine residues (Cys¹², Cys¹³ and Cys¹⁸) construct the As(III) binding site of the protein, however a global structural understanding of this arsenic binding remains unclear. We have obtained NMR assignments for ArsD as a starting point for probing structural changes on the protein that occur in response to metalloid binding and upon formation of a complex with ArsA. The predicted solution structure of ArsD is in agreement with recently published crystallographic structural results.     

Adjuvant chemotherapy, with or without taxanes, in early or operable breast cancer: a meta-analysis of 19 randomized trials with 30698 patients

Background

Taxanes have been extensively used as adjuvant chemotherapy for the treatment of early or operable breast cancer, particularly in high risk, node-negative breast cancer. Previous studies, however, have reported inconsistent findings regarding their clinical efficacy and safety. We investigated disease-free survival (DFS), overall survival (OS), and drug-related toxicities of taxanes by a systematic review and meta-analysis.

Methodology and Principal Findings

We systematically searched PubMed, EMBASE, the Cochrane Center Register of Controlled Trials, proceedings of major meetings, and reference lists of articles for studies conducted between January 1980 and April 2011. Randomized controlled trials (RCTs) comparing chemotherapy with and without taxanes in the treatment of patients with early-stage or operable breast cancer were eligible for inclusion in our analysis. The primary endpoint was DFS. Nineteen RCTs including 30698 patients were identified, including 8426 recurrence events and 3803 deaths. Taxanes administration yielded a 17% reduction of hazard ratio (HR) for DFS (HR = 0.83, 95% CI 0.79–0.88, p<0.001) and a 17% reduction of HR for OS (HR = 0.83, 95% CI 0.77–0.90, p<0.001). For high risk, node-negative breast cancer, the pooled HR also favoured the taxane-based treatment arm over the taxane-free treatment arm (HR = 0.82, 95% CI 0.77–0.87, p = 0.022). A significantly increased rate of neutropenia, febrile neutropenia, fatigue, diarrhea, stomatitis, and oedema was observed in the taxane-based treatment arm.

Conclusions/Significance

Adjuvant chemotherapy with taxanes could reduce the risk of cancer recurrence and death in patients with early or operable breast cancer, although the drug-related toxicities should be balanced. Furthermore, we also demonstrated that patients with high risk, node-negative breast cancer also benefited from taxanes therapy, a result that was not observed in previous studies.     

Improved siRNA/shRNA functionality by mismatched duplex

siRNA (small interfering RNA) and shRNA (small hairpin RNA) are powerful and commonly used tools in biomedical research. Currently, siRNAs are generally designed as two 21 nt strands of RNA that include a 19 nt completely complementary part and a 2 nt overhang. However, since the si/shRNAs use the endogenous miRNA machinery for gene silencing and the miRNAs are generally 22 nt in length and contain multiple internal mismatches, we tested if the functionality can be increased by designing the si/shRNAs to mimic a miRNA structure. We systematically investigated the effect of single or multiple mismatches introduced in the passenger strand at different positions on siRNA functionality. Mismatches at certain positions could significantly increase the functionality of siRNAs and also, in some cases decreased the unwanted passenger strand functionality. The same strategy could also be used to design shRNAs. Finally, we showed that both si and miRNA structured oligos (siRNA with or without mismatches in the passenger strand) can repress targets in all individual Ago containing cells, suggesting that the Ago proteins do not differentiate between si/miRNA-based structure for silencing activity.