Background: Organic solvents are widely used in cell biology experiments. Despite increasing the solubility, they have some moderate toxic effects. Therefore, selecting the appropriate solvent along with the use of suitable concentration insures the accuracy and reliability of experimental results. Objectives: The current study aimed to examine the cytotoxic effects of some organic solvents on various cell models including MCF-7, RAW-264.7 and human umbilical vein endothelial cells (HUVEC). Materials and Methods:To evaluate the cytotoxicity effect of common organic solvents on the MCF-7, RAW-264.7 and HUVEC cells, multi-table tournament (MTT) colorimetric assay, the widely used and validated cytotoxicity test was applied. For this purpose, the selected cells were treated with different concentrations (0, 0.1%, 0.5%, 1%, 1.5%, 2%, 3% and 5% v/v) of four most commonly used organic solvents (acetone, ethanol, dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) and then subjected to MTT experiment. Results: According to the obtained results, the cytotoxicity increased significantly with increasing the concentration of all four solvents compared to that of the control group. Studies with MCF-7, RAW-264.7 and HUVEC suggested that acetone, ethanol and DMSO at concentrations of 0.1% and 0.5%, had little or no toxicity, whereas higher concentrations inhibited the growth of all three cells. Compared with other three solvents, DMF displayed rather greater toxicity. Based on the results, proliferation of MCF-7, RAW-264.7 and HUVEC cells were inhibited by all used organic solvents, dose dependently. Conclusions: Thus, the background experimental error can be reduced remarkably by maximal concentration of 0.5% ethanol, acetone and DMSO and 0.1% DMF in the final treatment medium.

In the past decade, miRNAs have been extensively attracted the scientist's attentions as tumor suppressors or oncogenes that have been implicated in tumor progression, metastasis and intrinsic resistance to various cancer therapies. microRNA-21 (miR-21) demonstrates a potential oncogenic function and targets tumor inhibitor proteins in almost all types of cancer. miR-21 overexpression has been studied in terms of cell proliferation, migration, invasion, metastasis, and apoptosis regulation. Inhibition of miRNA expression using antisense technology by various nanovectors of different sizes, shapes and compositions has been evolved progressively to overcome the barriers confronted by miRNA delivery. Application of miR-21 antisense oligonucleotides for treating cancerous cells has become a promising achievement for cancer therapy. Moreover, miR-21 can mediate resistance to radiation and chemotherapy. The expanding role of miR-21 functions in human cancers with an emphasis on its regulatory targets and mechanisms, miR-21 related achievements against cancer promotion have been discussed.

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A comparison of the two most famous groups of calcium-regulated photoproteins, cnidarians and ctenophores, showed unexpectedly high degree of structural similarity regardless of their low sequence identity. It was suggested these photoproteins can play an important role in understanding the structural basis of bioluminescence activity. Based on this postulate, in this study the cDNA of mnemiopsin from luminous ctenophore Mnemiopsis leidyi was cloned, expressed, purified and sequenced. The purified cDNA, with 621 base pairs, coded a 206 residues protein. Sequence of mnemiopsin showed 93.5 and 51% similarity to other ctenophore proteins and cnidarians, respectively. The cDNA encoding apo-mnemiopsin of M. leidyi was expressed in Escherichia coli. The purified apo-protein showed a single band on SDS-PAGE (molecular weight ~27 kDa). A semi-synthetic mnemiopsin was prepared using coelenterazine and EDTA and its luminescence activity was measured in the presence of CaCl(2). The results showed an optimum pH of 9.0 and lower calcium sensitivity compared to aequorin. Comparison of amino acid residues in substrate binding site indicated that binding pocket of ctenophores contains less aromatic residues than cnidarians. This can lead to a decline in the number of stacking interactions between substrate and protein which can affect the stability of coelenterazine in binding cavity. Structural comparison of photoproteins with low sequence identity and high 3D structural similarity, can present a new insight into the mechanism of light emission in photoproteins.