Retracted systematic reviews continued to be frequently cited: a citation analysis.

BACKGROUND AND OBJECTIVES: To survey the citations of retracted non-Cochrane systematic reviews (SRs) in scientific literature. METHODS: We searched the Web of Science and Google Scholar from their inception to 30 April 2020 to find the citations of 153 previously identified retracted non-Cochrane SRs. We calculated the numbers of citations before and after retraction separately. We also described how the citation addressed the retraction and how it was used in the article. RESULTS: A We identified 954 citations of 128 retracted SRs. The number of retracted SRs and citations reached the peak in 2014 and 2016, respectively, and the majority of the citations (n = 580, 60.8%) were in articles published after the SR was retracted. The mean number of citation per retracted SRs was 7.5. 2.6 before and 4.5 after the publication of the retraction notice. Twenty-nine (5.0%) citations indicated the retraction of the SRs in the reference section. Nine of these citations supported the retracted SR's results, and 15 disagreed with them. CONCLUSION: Retracted SRs continue to be cited after the publication of the retraction notice. Standardized methods are needed to guide the management of retractions and avoid inappropriate citations of retracted articles.

Grape Seed Proanthocyanidins Inhibit Migration and Invasion of Bladder Cancer Cells by Reversing EMT through Suppression of TGF-ß Signaling Pathway.

Bladder cancer (BC) is the most common cancer of the urinary system. Despite advances in diagnosis and therapy, the prognosis is still poor because of recurrence and metastasis. Epithelial-mesenchymal transition (EMT) is considered to play an important role in the invasion and metastasis of BC. Grape seed proanthocyanidins (GSPs) exhibit chemopreventive and chemotherapeutic activities against several types of cancer. However, their effects and underlying mechanisms on the invasive potential of BC remain unclear. In this study, we found that GSPs inhibited migration, invasion, and MMP-2/-9 secretion of both T24 and 5637 bladder cancer cells at noncytotoxic concentrations. We also discovered that 5637 cells were more suitable than T24 cells for the EMT study. Further study showed that GSPs inhibited EMT by reversing the TGF-ß-induced morphological change and upregulation of mesenchymal markers N-cadherin, vimentin, and Slug as well as downregulation of epithelial markers E-cadherin and ZO-1 in 5637 cells. GSPs also inhibited TGF-ß-induced phosphorylation of Smad2/3, Akt, Erk, and p38 in 5637 cells without affecting the expression of total Smad2/3, Akt, Erk, and p38. Taken together, the results of the present study demonstrate that GSPs effectively inhibit the migration and invasion of BC cells by reversing EMT through suppression of the TGF-ß signaling pathway, which indicates that GSPs could be developed as a potential chemopreventive and therapeutic agent against bladder cancer.

More consideration is needed for retracted non-Cochrane systematic reviews in medicine: a systematic review.

OBJECTIVE: To analyze the retraction status and reasons of non-Cochrane systematic reviews (SRs) in medicine. STUDY DESIGN AND SETTING: MEDLINE, Embase, Retraction Watch Database and Google Scholar were systematically searched to find all retracted non-Cochrane SRs. RESULTS: Of 159 non-Cochrane SRs in medicine retracted between 2004 and 2020, more than 70% were led by authors from China and affiliated with hospitals. The largest proportion of retraction notices were issued by the publisher and editor(s) jointly. Fraudulent peer-review was the most common reason for retraction, followed by unreliable data meaning errors in study selection or data analysis. The median time between publication and retraction was 14 months, and SRs retracted due to research misconduct took longer to retract than honest error. CONCLUSION: The total number of retracted SRs is increasing worldwide, in particular in China. The most common reasons for retraction are fraudulent peer-review and unreliable data, and in most cases the SR is retracted more than a year after publication. Better systems of ethical oversight and culture to improve the process of peer review and adherence to the COPE retraction guidance are needed, and authors should strengthen their skills in SR methodology.

Synthesis of tetrapeptide Bz-RGDS-NH2 by a combination of chemical and enzymatic methods.

The tetrapeptide Bz-Arg-Gly-Asp-Ser-NH(2) (Bz-RGDS-NH(2)) was successfully synthesized by a combination of chemical and enzymatic methods in this study. Firstly, the precursor tripeptide Gly-Asp-Ser-NH(2) (GDS-NH(2)) was synthesized by a novel chemical method in four steps including chloroacetylation of l-aspartic acid, synthesis of chloroacetyl l-aspartic acid anhydride, the synthesis of ClCH(2)COAsp-SerOMe and ammonolysis of ClCH(2)COAsp-SerOMe. Secondly, lipase (PPL) was used to catalyze the formation of Bz-RGDS-NH(2) in aqueous water-miscible organic cosolvent systems using Bz-Arg-OEt as the acyl donor and GDS-NH(2) as the nucleophile. The optimum conditions were Bz-Arg-OEt 50 mM; GDS-NH(2) 400 mM; 10 degrees C, 0.1M phosphate buffer, pH 7.5; 60% DMF or 58% DMSO, PPL: 10 mg ml(-1) with the maximum yields of the tetrapeptide of 73.6% for DMF and 70.4% for DMSO, respectively. The secondary hydrolysis of the tetrapeptide product did not take place due to the absence of amidase activity of lipase.

Chemo-enzymatic synthesis of tripeptide RGD diamide in organic solvents.

The tripeptide BzArgGlyAsp(NH(2))(2) was synthesized by a combination of chemical and enzymatic methods in this study. First of all, GlyAsp(NH(2))(2) was synthesized by a novel chemical method in three steps including chloroacetylation of L-aspartic acid, esterification of chloroacetyl L-aspartic acid and ammonolysis of chloroacetyl L-aspartic acid diethyl ester. Secondly, kinetically controlled synthesis of BzArgGlyAsp(NH(2))(2) catalyzed by trypsin in organic solvent was conducted. The optimum conditions are pH 8.0, 30 degrees C in ethanol/Tris-HCl buffer system (85:15, v/v) for 80 min in the maximum yield of 74.4%.

Synthesis of a precursor dipeptide of RGDS (Arg-Gly-Asp-Ser) catalysed by the industrial protease alcalase.

Synthesis of Bz-Arg-Gly-NH(2) (N-benzoylargininylglycinamide) [a precursor dipeptide of RGDS (Arg-Gly-Asp-Ser)] catalysed by protease in water/organic co-solvent systems was studied. Starting substrates were N-benzoyl-L-arginine ethyl ester hydrochloride (acyl donor) and glycinamide (nucleophile). Acetonitrile was selected as the organic solvent. Alcalase, an industrial alkaline protease, was applied to the synthesis of the target dipeptide. The conditions of the synthesis reaction were optimized by examining the effects of several factors, including water content, temperature, pH, molar ratio of the substrates and reaction time, on the yield of Bz-Arg-Gly-NH(2). The optimum conditions were established to be pH 10.0, 45 degrees C, in acetonitrile/0.1 M Na(2)CO(3)/NaHCO(3) buffer system (90:10, v/v) for 1 h with a dipeptide yield of 82.9%.

New synthetic route for RGD tripeptide.

A new route was employed to synthesize RGD. First, Gly-Asp dipeptide was synthesized by a novel chemical method in two steps, including chloroacetylation of L-aspartic acid and ammonolysis of chloroacetyl L-aspartic acid. Second, Nalpha-Z- L-Arginine was reacted with Gly-Asp to synthesize RGD by the N-carboxyanhydride method. Less protected amino acids were used in this synthesis. This method possessed advantages of low cost, simplicity, and rapidity with a reasonable yield of 62% calculated from arginine. In addition, compared with the above method, a conventional solid phase method was also used to synthesize RGD, the yield was 75% calculated from the first amino acid anchored to resin.

Alcalase-catalyzed, kinetically controlled synthesis of a precursor dipeptide of RGDS in organic solvents.

The protease-catalyzed, kinetically controlled synthesis of a precursor dipeptide of RGDS, Z-Asp-Ser-NH2 in organic solvents was studied. Alcalase, an industrial alkaline protease, was used to catalyze the synthesis of the target dipeptide in water-organic cosolvents systems with Z-Asp-OMe as the acyl donor and Ser-NH2 as the nucleophile. Acetonitrile was selected as the organic solvent from acetonitrile, ethanol, methanol, DMF, DMSO, ethyl acetate, 2-methyl-2-propanol, and chloroform tested under the experimental conditions. The conditions of the synthesis reaction were optimized by examining the effects of several factors, including water content, temperature, pH, and reaction time on the Z-Asp-Ser-NH2 yields. The optimum conditions are pH 10.0, 35 degrees C, in acetonitrile/Na2CO3-NaHCO3 buffer system (85:15, v/v), 6 h, with a dipeptide yield of 75.5%.