RETRACTED: Si RNA inhibition of GRP58 associated with decrease in mitomycin C-induced DNA cross-linking and cytotoxicity

In-silico prediction of drug targets, biological activities, signal pathways and regulating networks of dioscin based on bioinformatics

Background

Inverse docking technology has been a trend of drug discovery, and bioinformatics approaches have been used to predict target proteins, biological activities, signal pathways and molecular regulating networks affected by drugs for further pharmacodynamic and mechanism studies.

Methods

In the present paper, inverse docking technology was applied to screen potential targets from potential drug target database (PDTD). Then, the corresponding gene information of the obtained drug-targets was applied to predict the related biological activities, signal pathways and processes networks of the compound by using MetaCore platform. After that, some most relevant regulating networks were considered, which included the nodes and relevant pathways of dioscin.

Results

71 potential targets of dioscin from humans, 7 from rats and 8 from mice were screened, and the prediction results showed that the most likely targets of dioscin were cyclin A2, calmodulin, hemoglobin subunit beta, DNA topoisomerase I, DNA polymerase lambda, nitric oxide synthase and UDP-N-acetylhexosamine pyrophosphorylase, etc. Many diseases including experimental autoimmune encephalomyelitis of human, temporal lobe epilepsy of rat and ankylosing spondylitis of mouse, may be inhibited by dioscin through regulating immune response alternative complement pathway, G-protein signaling RhoB regulation pathway and immune response antiviral actions of interferons, etc. The most relevant networks (5 from human, 3 from rat and 5 from mouse) indicated that dioscin may be a TOP1 inhibitor, which can treat cancer though the cell cycle– transition and termination of DNA replication pathway. Dioscin can down regulate EGFR and EGF to inhibit cancer, and also has anti-inflammation activity by regulating JNK signaling pathway.

Conclusions

The predictions of the possible targets, biological activities, signal pathways and relevant regulating networks of dioscin provide valuable information to guide further investigation of dioscin on pharmacodynamics and molecular mechanisms, which also suggests a practical and effective method for studies on the mechanism of other chemicals.

Strategies and validation for siRNA-based therapeutics for the reversal of multi-drug resistance in cancer

Resistance of cancer cells to anticancer drugs is the main reason for the failure of traditional cancer treatments. Various cellular components and different loops within the signaling pathways contribute to drug resistance which could be modulated with the aim to restore drug efficacy. Unveiling the molecular mechanisms for cancer drug resistance has now paved the way for the development of novel approaches to regulate the response rates to anticancer drugs at the genetic level. The recent progress on identification and validation of the vital genes directly or indirectly involved in development of cancer drug resistance with the aid of the specific knock down ability of RNA interference technology is discussed in this review.

A new mechanism of action for the anticancer drug mitomycin C: mechanism-based inhibition of thioredoxin reductase

Mitomycin C (MMC) is a chemotherapeutic drug that requires an enzymatic bioreduction to exert its biological effects. Upon reduction, MMC is converted into a highly reactive bis-electrophilic intermediate that alkylates cellular nucleophiles. Alkylation of DNA is the most favored mechanism of action for MMC, but other modes of action, such as redox cycling and inhibition of rRNA, may also contribute to the biological action of the drug. In this work, we show that thioredoxin reductase (TrxR) is also a cellular target for MMC. We show that MMC inhibits TrxR in vitro, using purified enzyme, and in vivo, using cancer cell cultures. The inactivation presents distinctive parameters of mechanism-based inhibitors: it is time- and concentration-dependent and irreversible. Additionally, spectroscopic experiments (UV, circular dichroism) show that the inactivated enzyme contains a mitosene chromophore. On the basis of kinetic and spectroscopic data, we propose a chemical mechanism for the inactivation of the enzyme that starts with a reduction of the quinone ring of MMC by the selenolthiol active site of TrxR and a subsequent alkylation of the active site by the activated drug. We also report that MMC inactivates TrxR in cancer cell cultures and that this inhibition correlates directly with the cytotoxicity of the drug, indicating that inhibition of TrxR may play a major role in the biological mode of action of the drug.

Curcumin reduced the side effects of mitomycin C by inhibiting GRP58-mediated DNA cross-linking in MCF-7 breast cancer xenografts

Mitomycin C (MMC), a chemotherapeutic agent in breast cancer treatments, inhibits tumor growth through DNA cross-linking and breaking, but it has severe side effects. Here we examined whether and how curcumin reduced the side effects of MMC. We found that combination treatment with MMC and curcumin reduced tumor weight by 70% and 36% compared with saline and curcumin-treated groups, respectively. The combination treatment reduced weight loss and improved kidney function and bone marrow suppression compared with MMC treatment alone. Moreover, the combination treatment inhibited glucose regulatory protein (GRP58)-mediated DNA cross-linking. The combination treatment inhibited GRP58 through the ERK/p38 MAPK pathway. In conclusion, the current study provided evidence that MMC and curcumin combination treatment reduced MMC side effects by inhibiting GRP58-mediated DNA cross-linking through the ERK/p38 MAPK pathway.

Genes and proteins differentially expressed during in vitro malignant transformation of bovine pancreatic duct cells

Pancreatic carcinoma has an extremely bad prognosis due to lack of early diagnostic markers and lack of effective therapeutic strategies. Recently, we have established an in vitro model recapitulating the first steps in the carcinogenesis of the pancreas. SV40 large T antigen-immortalized bovine pancreatic duct cells formed intrapancreatic adenocarcinoma tumors on k-ras(mut) transfection after orthotopic injection in the nude mouse pancreas. Here we identified genes and proteins differentially expressed in the course of malignant transformation using reciprocal suppression subtractive hybridization and 2D gel electrophoresis and mass spectrometry, respectively. We identified 34 differentially expressed genes, expressed sequence tags, and 15 unique proteins. Differential expression was verified for some of the genes or proteins in samples from pancreatic carcinoma. Among these genes and proteins, the majority had already been described either to be influenced by a mutated ras or to be differentially expressed in pancreatic adenocarcinoma, thus proving the feasibility of our model. Other genes and proteins (e.g., BBC1, GLTSCR2, and rhoGDIalpha), up to now, have not been implicated in pancreatic tumor development. Thus, we were able to establish an in vitro model of pancreatic carcinogenesis, which enabled us to identify genes and proteins differentially expressed during the early steps of malignant transformation.