[Molecular mechanism of cisplatin to enhance the ability of TRAIL in reversing multidrug resistance in gastric cancer cells].

OBJECTIVE: To study the molecular mechanism of cisplatin to enhance the ability of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in reversing multidrug resistance in vincristine-resistant human gastric cancer SGC7901/VCR cells. METHODS: MTT assay was used to measure the 50% inhibiting concentration (IC50) and cell survival in SGC7901 and SGC7901/VCR cells after different treatments. SGC7901/VCR cells were treated with different concentrations of DDP, different concentrations of TRAIL alone or in combination, and then the mRNA and protein levels of several genes were determined by RT-PCR, RT-qPCR and Western-blot analysis. After targeted silencing with specific siRNA and transfection of recombinant plasmid c-myc into the SGC7901/VCR cells, the mRNA and protein levels of DR4, DR5 and c-myc were determined by RT-PCR and Western-blot analysis. RESULTS: After combined treatment with TRAIL and DDP of the SGC7901/VCR cells, the IC50 of VCR, DDP, ADM, and 5-Fu treatment was significantly decreased compared with the control group or TRAIL-treated group (P < 0.05). After treatment with 0, 10, 50 ng/ml TRAIL in combination with 0.4 µg/ml DDP, the SGC7901/VCR cells showed significantly higher activation of caspase 3, down-regulation of DNA-PKcs/Akt/GSK-3ß signaling pathway, and higher inhibition of MDR1(P-gp) and MRP1 than those treated with TRAIL alone (P < 0.01 for all). The mRNA and protein levels of DR4, DR5, c-myc were significantly decreased after silencing c-myc with specific siRNA in the SGC7901/VCR cells (P < 0.01 for all), and were significantly increased after transfection of recombinant plasmid c-myc into the SGC7901/VCR cells (P < 0.01 foe all). After the treatment with 10 ng/ml TRAIL, 0.25 µg/ml DDP + 10 ng/ml TRAIL and 0.5 µg/ml DDP + 10 ng/ml TRAIL, the relative expression level of c-myc protein in the SGC7901/VCR cells was 0.314 ± 0.012, 0.735 ± 0.026, and 0.876 ± 0.028, respectively, and the relative expression of cytochrome C was 0.339 ± 0.036, 0.593 ± 0.020 and 0.735 ± 0.031, respectively, and the relative expression levels of DR4, DR5, active-caspase 3 and active-caspase 9 in the SGC7901/VCR cells were also increased along with increasing DDP concentrations. CONCLUSIONS: The activation of DNA-PKcs/Akt/GSK-3ß signaling pathway and high expression of MDR1 and MRP1 play an important role in the multi-drug resistance properties of SGC7901/VCR cells. After combining with TRAIL, DDP can enhance the expression of DR4 and DR5 through up-regulating c-myc and enhancing the activation of caspase 3 and caspase 9 by facilitating mitochondrial release of cytochrome C. It may be an important molecular mechanism of DDP-induced sensitization of TRAIL to reverse the multidrug resistancein SGC7901/VCR cells.

Inhibition of cannabinoid degradation enhances hippocampal contextual fear memory and exhibits anxiolytic effects.

Recent studies have demonstrated the pivotal involvement of endocannabinoids in regulating learning and memory, but the conclusions obtained from different paradigms or contexts are somewhat controversial, and the underlying mechanisms remain largely elusive. Here, we show that JZL195, a dual inhibitor of fatty acid amide hydrolase and monoacylglycerol lipase, can enhance the performance of mice in a contextual fear conditioning task and increase the time spent in open arms in the elevated zero maze (EZM). Although the effect of JZL195 on fear memory could not be inhibited by antagonists of cannabinoid receptors, the effect on the EZM seems to be mediated by CB1R. Simultaneously, hippocampal neurons are hyperactive, and theta oscillation power is significantly increased during the critical period of memory consolidation upon treatment with JZL195. These results suggest the feasibility of targeting the endocannabinoid system for the treatment of various mental disorders.

HES1 promotes aerobic glycolysis and cancer progression of colorectal cancer via IGF2BP2-mediated GLUT1 m6A modification.

Aerobic glycolysis has been shown to play a key role in tumor cell proliferation and metastasis. However, how it is directly regulated is largely unknown. Here, we found that HES1 expression was significantly higher in CRC tissues than that in adjacent normal tissues. Moreover, high HES1 expression is associated with poor survival in CRC patients. HES1 knockdown markedly inhibited cell growth and metastasis both in vitro and in vivo. Additionally, silencing of HES1 suppressed aerobic glycolysis of CRC cells. Mechanistic studies revealed that HES1 knockdown decreased the expression of GLUT1, a key gene of aerobic glycolysis, in CRC cells. GLUT1 overexpression abolished the effects of HES1 knockdown on cell aerobic glycolysis, proliferation, migration and invasion. ChIP-PCR and dual-luciferase reporter gene assay showed that HES1 directly bound the promoter of IGF2BP2 and promoted IGF2BP2 expression. Furthermore, our data indicated that IGF2BP2 recognized and bound the m6A site in the GLUT1 mRNA and enhanced its stability. Taken together, our findings suggest that HES1 has a significant promotion effect on CRC aerobic glycolysis and progression by enhancing the stability of m6A-modified GLUT1 mRNA in an IGF2BP2-dependent manner, which may become a viable therapeutic target for the treatment of CRC in humans. The mechanism of HES1 regulating glycolysis in CRC.

Cisplatin-mediated c-myc overexpression and cytochrome c (cyt c) release result in the up-regulation of the death receptors DR4 and DR5 and the activation of caspase 3 and caspase 9, likely responsible for the TRAIL-sensitizing effect of cisplatin.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) reverses multidrug resistance (MDR) and induces apoptosis in MDR gastric carcinoma cells. In our previous study, cisplatin proved to be a sensitizing agent for TRAIL. To study the synergistic effects of cisplatin and TRAIL, we investigated the mechanism by which TRAIL reverses multidrug resistance, the role of c-myc in modulating the death receptors DR4 and DR5 and the relationship between cisplatin and cytochrome c (cyt c) release in SGC7901/VCR and SGC7901/DDP cells. We found that after treatment with TRAIL, the DNA-PKcs/Akt/GSK-3ß pathway, which is positively correlated with the levels of MDR1 and MRP1, was significantly inhibited and that this tendency can be abolished by Z-DEVD-FMK (a specific caspase 3 inhibitor). We also found that suppression of c-myc by siRNA reduced the expression of DR4 and DR5 and that transfection with a pAVV-c-myc expression vector increased the expression of DR4 and DR5. Moreover, cisplatin increased the expression of c-myc in the presence of TRAIL, and there is a clear increase in cyt c release from mitochondria with the increasing concentrations of cisplatin. Meanwhile, the intrinsic death receptor pathway of caspase 9, as well as the common intrinsic and extrinsic downstream target, caspase 3, was potently activated by the release of cyt c. Together, we conclude that in TRAIL-treated MDR gastric carcinoma cells, cisplatin induces the death receptors DR4 and DR5 through the up-regulation of c-myc and strengthens the activation of caspases via promoting the release of cyt c. These effects would then be responsible for the TRAIL sensitization effect of cisplatin.