Overexpressed long noncoding RNA TUG1 affects the cell cycle, proliferation, and apoptosis of pancreatic cancer partly through suppressing RND3 and MT2A.

BACKGROUND: Long noncoding RNAs (lncRNAs) are involved in various human diseases, including cancers. However, their mechanisms remain undocumented. We investigated alterations in lncRNA that may be related to pancreatic cancer (PC) through analysis of microarray data. METHODS: In the present study, quantitative real-time PCR analysis was used to examine the expression of taurine upregulated 1 (TUG1) in PC tissue samples and PC cell lines. In PC cell lines, MTT assays, colony formation assays, and flow cytometry were used to investigate the effects of TUG1 on proliferation, cell cycle regulation, and apoptosis. Moreover, we established a xenograft model to assess the effect of TUG1 on tumor growth in vivo. The molecular mechanism of potential target genes was detected through nuclear separation experiments, RNA immunoprecipitation (RIP), chromatin immunoprecipitation assays (ChIP), and other experimental methods. RESULTS: The findings suggest that the abnormally high expression of TUG1 in PC tissues was associated with tumor size and pathological stage. Knockdown of TUG1 blocked the cell cycle and accelerated apoptosis, thereby inhibiting the proliferation of PC cells. In addition, RIP experiments showed that TUG1 can recruit enhancer of zeste homolog 2 (EZH2) to the promoter regions of Rho family GTPase 3 (RND3) and metallothionein 2A (MT2A) and inhibit their expression at the transcriptional level. Furthermore, ChIP experiments demonstrated that EZH2 could bind to the promoter regions of RND3 and MT2A. The knockdown of TUG1 reduced this binding capacity. CONCLUSION: In conclusion, our data suggest that TUG1 may regulate the expression of PC-associated tumor suppressor genes at the transcriptional level and these may become potential targets for the diagnosis and treatment of PC.

The effects of buthionine sulfoximine on the proliferation and apoptosis of biliary tract cancer cells induced by cisplatin and gemcitabine.

Patients with biliary tract cancer (BTC) have a poor prognosis. Advanced BTC patients have been treated with cisplatin in combination with gemcitabine, however, the treatment has had little impact on survival rates, and more effective treatments are urgently required for this disease. Previous studies discovered that buthionine sulfoximine (BSO), a potent inhibitor of glutathione (GSH) synthesis, was able to enhance the cytotoxic effect of various drugs in cancer cells. Phase I studies demonstrated that continuous-infusion of BSO was relatively non-toxic and resulted in the depletion of tumor GSH. However, the synergistic effect of BSO and cisplatin in BTC cells remains unknown, and no reports are available regarding sensitization to gemcitabine by BSO. In the present study, the effect of BSO in combination with cisplatin or gemcitabine in the treatment of BTC cells was examined in vitro. Cytotoxic effects were measured using an MTT assay, Annexin V assay and fluorescence-activated cell sorting analysis. Antiapoptotic protein expression levels were examined using western blot analysis. The results revealed that a sub-toxic concentration of BSO was capable of significantly enhancing cisplatin-induced apoptosis in BTC cells. The mechanisms of BSO's effect on BTC cells may be attributable to the reduction of GSH levels and downregulation of the expression of antiapoptotic proteins (Bcl-2, Bcl-xL and Mcl-1). Furthermore, BSO enhanced the antiproliferative effect of gemcitabine. In conclusion, the present data are the first results to indicate that BSO may sensitize BTC cells to standard first-line chemotherapeutic agents (cisplatin and gemcitabine). Combining BSO with cisplatin and gemcitabine is a promising therapeutic strategy for the treatment of BTC.

Phenylethyl isothiocyanate reverses cisplatin resistance in biliary tract cancer cells via glutathionylation-dependent degradation of Mcl-1.

Biliary tract cancer (BTC) is a highly malignant cancer. BTC exhibits a low response rate to cisplatin (CDDP) treatment, and therefore, an understanding of the mechanism of CDDP resistance is urgently needed. Here, we show that BTC cells develop CDDP resistance due, in part, to upregulation of myeloid cell leukemia 1 (Mcl-1). Phenylethyl isothiocyanate (PEITC), a natural compound found in watercress, could enhance the efficacy of CDDP by degrading Mcl-1. PEITC-CDDP co-treatment also increased the rate of apoptosis of cancer stem-like side population (SP) cells and inhibited xenograft tumor growth without obvious toxic effects. In vitro, PEITC decreased reduced glutathione (GSH), which resulted in decreased GSH/oxidized glutathione (GSSG) ratio and increased glutathionylation of Mcl-1, leading to rapid proteasomal degradation of Mcl-1. Furthermore, we identified Cys16 and Cys286 as Mcl-1 glutathionylation sites, and mutating them resulted in PEITC-mediated degradation resistant Mcl-1 protein. In conclusion, we demonstrate for the first time that CDDP resistance is partially associated with Mcl-1 in BTC cells and we identify a novel mechanism that PEITC can enhance CDDP-induced apoptosis via glutathionylation-dependent degradation of Mcl-1. Hence, our results provide support that dietary intake of watercress may help reverse CDDP resistance in BTC patients.