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Introduction: The overexpression of ATP-binding cassette (ABC) transporters, ABCB1 and ABCG2, are two of the major mediators of multidrug resistance (MDR) in cancers. Although multiple ABCB1 and ABCG2 inhibitors have been developed and some have undergone evaluation in clinical trials, none have been clinically approved. The compound, MK-2206, an inhibitor of the protein kinases AKT1/2/3, is undergoing evaluation in multiple clinical trials for the treatment of certain types of cancers, including those resistant to erlotinib. In this in vitro study, we conducted in vitro experiments to determine if MK-2206 attenuates multidrug resistance in cancer cells overexpressing the ABCB1 or ABCG2 transporter. Methodology: The efficacy of MK-2206 (0.03-1 µM), in combination with the ABCB1 transporter sub-strates doxorubicin and paclitaxel, and ABCG2 transporter substrates mitoxantrone, SN-38 and topotecan, were determined in the cancer cell lines, KB-C2 and SW620/Ad300, which overexpress the ABCB1 transporter or H460/MX20 and S1-M1-80, which overexpress the ABCG2 transporter, respectively. The expression level and the localization of ABCG2 transporter on the cancer cells membranes were determined using western blot and immunofluorescence assays, respectively, following the incubation of cells with MK-2206. Finally, the interaction between MK-2206 and human ABCG2 transporter was predicted using computer-aided molecular modeling. Results: MK-2206 significantly increased the efficacy of anticancer compounds that were substrates for the ABCG2 but not the ABCB1 transporter. MK-2206 alone (0.03-1 µM) did not significantly alter the viability of H460/MX20 and S1-M1-80 cancer cells, which overexpress the ABCG2 transporter, compared to cells incubated with vehicle. However, MK-2206 (0.3 and 1 µM) significantly increased the anticancer efficacy of mitoxantrone, SN-38 and topotecan, in H460/MX20 and S1-M1-80 cancer cells, as indicated by a significant decrease in their IC50 values, compared to cells incubated with vehicle. MK-2206 significantly increased the basal activity of the ABCG2 ATPase (EC50 = 0.46 µM) but did not significantly alter its expression level and sub-localization in the membrane. The molecular modeling results suggested that MK-2206 binds to the active pocket of the ABCG2 transporter, by a hydrogen bond, hydrophobic interactions and π-π stacking. Conclusion: These in vitro data indicated that MK-2206 surmounts resistance to mitoxantrone, SN-38 and topotecan in cancer cells overexpressing the ABCG2 transporter. If these results can be translated to humans, it is possible that MK-2206 could be used to surmount MDR in cancer cells overexpressing the ABCG2 transporter.

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DDP-resistant MDA-MB-231 cells (MDA-MB-231/DDP) cells had higher expression of L1CAM than their parental cells. L1CAM siRNA decreased the IC50 of MDA-MB-231/DDP cells to DDP. L1CAM inhibition down-regulated p-AKT/AKT in MDA-MB-231/DDP cells; meanwhile, it could promote MDA-MB-231/DDP cell apoptosis, inhibit cell EMT, invasion, and migration. Moreover, SC79 (an AKT activator) increased the DDP-resistance of MDA-MB-231/DDP cells, which was reversed by L1CAM inhibition. Furthermore, co-treatment of L1CAM shRNA and cisplatin injection had better anti-tumor effects in vivo than these two single treatments with decreased p-AKT/AKT. Thus, silencing L1CAM reversed the DDP resistance by inhibiting the AKT pathway.

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A new genus and new species of terrestrial freshwater crab, Calcipotamon puglabrum gen. nov. et sp. nov., is described from the limestone forests of Changjiang, Hainan Island, China, based on morphology and mitochondrial 16S rDNA sequences. The new genus is closest to Neotiwaripotamon Dai Naiyanetr, 1994, and Tiwaripotamon Bott, 1970, but differs in a combination of carapace, third maxilliped, ambulatory leg and male gonopod characters. Molecular analysis shows that the new genus is closely related with but not clustered within other Hainan potamid genera. Notes on the general biology of this new species are also provided.

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Myostatin (MSTN) is a member of the TGF-ß superfamily that acts as a negative regulator of skeletal muscle growth. A full-length, 2 180 bp, cDNA sequence of the myostatin gene from Schizopygopisis pylzovi was cloned with RT-PCR,5'-RACE and 3'-RACE and the cDNA clone included a 1 128 bp ORF, encoding a 375 amino acid peptide. Using PCR, we obtained the sequences of two introns of the MSTN gene and found that its structure in Schizopygopsis pylzovi was similar to that of other vertebrates, including three exons and two introns. Likewise, the putative MSTN peptide of Schizopygopsis pylzovi contains a conserved RXXR proteolytic cleavage domain, and 8 conserved cysteine residues in the C terminal of the protein, similar to other vertebrates. Phylogenetic analysis showed that the MSTN of Schizopygopsis pylzovi has high homology with other cyprinid fishes, but a low homology with mammals and birds. In the 9 examined tissues, the MSTN gene was highly expressed in heart, kidney, intestine and spermary, while weakly expressed in muscle, brain, fat, gill and hepatopancreas. Quantitative real-time PCR analysis showed that the expression of MSTN gene was different during embryo development, suggesting that the fish MSTN may not only play roles in muscle development but also contribute to other biological functions.

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