Quinone oxidoreductase 1 is overexpressed in gastric cancer and associated with outcome of adjuvant chemotherapy and survival.

BACKGROUND: Quinine oxidoreductase 1 (NQO1) plays a vital role in protecting normal cells against oxidative damage and electrophilic attack. It is highly expressed in many solid tumors, suggesting a role in cancer development and progression. However, the role of NQO1 in gastric cancer and its effect on cancer development and prognosis have not been fully investigated. AIM: To investigate the clinical relevance of NQO1 protein expression in gastric cancer and to explore the potential of NQO1 to serve as a prognostic biomarker and therapeutic target. METHODS: In this retrospective study, gastric cancer specimens of 175 patients who were treated between 1995 and 2011 were subjected to immunohistochemistry analyses for NQO1. The correlation of NQO1 expression with gastric cancer prognosis and clinical and pathological parameters was investigated. RESULTS: NQO1 protein was overexpressed in 59.43% (104/175) of the analyzed samples. Overexpression of NQO1 was associated with a significantly inferior prognosis. In addition, multivariate analysis suggested that NQO1 overexpression, along with tumor stage and patient age, are prominent prognostic biomarkers for gastric cancer. Moreover, NQO1 overexpression was correlated to a better response to 5-fluorouracil (5-FU)-based adjuvant chemotherapy. CONCLUSION: NQO1 overexpression is associated with a significantly poor prognosis and better response to 5-FU in patients with gastric cancer. These findings are relevant for improving therapeutic approaches for gastric cancer patients.

Luteolin sensitizes two oxaliplatin-resistant colorectal cancer cell lines to chemotherapeutic drugs via inhibition of the Nrf2 pathway.

Oxaliplatin is a first-line therapy for colorectal cancer, but cancer cell resistance to the drug compromises its efficacy. To explore mechanisms of drug resistance, we treated colorectal cancer cells (HCT116 and SW620) long-term with oxaliplatin and established stable oxaliplatin-resistant lines (HCT116-OX and SW620-OX). Compared with parental cell lines, IC50s for various chemotherapeutic agents (oxaliplatin, cisplatin and doxorubicin) were increased in oxaliplatin-resistant cell lines and this was accompanied by activation of nuclear factor erythroid-2 p45-related factor 2 (Nrf2) and NADPH quinone oxidoreductase 1 (NQO1). Furthermore, luteolin inhibited the Nrf2 pathway in oxaliplatin-resistant cell lines in a dose-dependent manner. Luteolin also inhibited Nrf2 target gene [NQO1, heme oxygenase-1 (HO-1) and GSTα1/2] expression and decreased reduced glutathione in wild type mouse small intestinal cells. There was no apparent effect in Nrf2-/- mice. Luteolin combined with other chemotherapeutics had greater anti-cancer activity in resistant cell lines (combined index values below 1), indicating a synergistic effect. Therefore, adaptive activation of Nrf2 may contribute to the development of acquired drug-resistance and luteolin could restore sensitivity of oxaliplatin-resistant cell lines to chemotherapeutic drugs. Inhibition of the Nrf2 pathway may be the mechanism for this restored therapeutic response.

[Nrf2 as a chemoprevention target in gastrointestinal carcinoma].

Gastrointestinal tract carcinoma is one of the leading causes of cancer-related death in China. Chemoprevention has been considered as a potential approach to control this type of disease. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a redox-sensitive transcription factor that protects cells from oxidative/electrophilic stresses by activating the expression of a battery of cytoprotective genes through the antioxidant response element (ARE). Recently, Nrf2 has emerged as a novel target for chemoprevention. Several natural or synthetic chemicals, which activate Nrf2/ARE signaling pathway, have showed effect in animal models, and promises in many ongoing clinical trials. This review summarizes the recent findings on the regulation of Nrf2/ARE signaling pathway, and the developments in both preclinical and clinical studies.

[Research progress on MKP-1 in tumor drug resistance].

The main obstacle for chemotherapy is tumor drug resistance. Studying the mechanisms of drug resistance and reversing drug resistance is the key to improve the effectiveness of chemotherapy. It has been reported that MKP-1 plays an important role in tumor drug resistance. MKP-1, as a negative regulator of MAPKs, is involved in the MAPKs mediated drug resistance and is regulated by ERK and p38 signaling pathways.However, the relationship between MKP-1 and other drug resistance-related signaling pathways is not clear and requires further investigation.

[Anti-proliferation and chemo-sensitization effects of apigenin on human lung cancer cells].

OBJECTIVE: To investigate the antitumor effect of apigenin on human lung cancer cells. METHODS: The anti-proliferation and sensitization effects of apigenin on human lung cancer cells was accessed by counting cells after Trypan blue staining and MTS assay. RESULTS: (1) Apigenin significantly suppressed the proliferation of four types of human lung cancer cells (A549:P=0.041, H460:P=0.050, LTEP-a2:P=0.039, H292:P=0.016); (2) Apigenin significantly increased the susceptibility of human lung cancer cells to antitumor drugs (P<0.05 or P<0.01) in a synergistic way (almost all of the combination index values are less than 1). CONCLUSION: Apigenin widely inhibits cell proliferation of various lung cancer cell lines in a dose-dependent manner and the combination treatment of apigenin and antitumor drugs is very effective in human lung cancer cells, and Nrf2-ARE pathway may contribute to the mechanism.

[Study on the optical properties of semiconductor nanocrystalline powder using photoacoustic technology].

The optical properties of semiconductor nanocrystalline powder were studied by using photoacoustic spectroscopy technique. The band gap and the optical absorption coefficient of semiconductor nanocrystalline powder of TiO2, ZnO and Al-doped ZnO were measured by normalized photoacoustic spectroscopy technique. The results show that the optical properties of semiconductor nanocrystalline powder relate to particle size and particle shape. The band gap and the optical absorption coefficient of semiconductor nanocrystalline powder can be controlled by its fabricating techniques. By doping and changing the size and the shape of nanocrystals, changing the optical and electrical properties was achieved.

[Nrf2 down-regulated cell line H460-N5 with Keap1 over-expression increased sensitivity to anti-cancer drugs].

OBJECTIVE: To maked a Nrf2 down-regulated cell line by over-expressing Keap1 in H460 cells to study the role of Nrf2 in drug resistance. METHODS: Transfecting H460 cells with mKeap1-pEGFP and screenig for Keap1 expressing clones by Western blotting with antibodies against Nrf2, HO-1, NQO1 and AKR1C. The cell line with Keap1 over-expression was further confirmed by real-time PCR. The cytotoxicity of H460-N5 to anti-cancer drugs was evaluated by MTS assay. RESULT: MTS assay results showed the enhanced cytotoxicity of anticancer drugs (Oxaliplatin, Doxorubicin and Etopside) to the H460 cell line with keap1 overexpression compared to the control cell line. In H460-N0 cells, the IC(50) values of Oxaliplation and Etopside were 93 micromol/L and 100 micromol/L respectively whereas the IC(50) values of the two drugs were 42 micromol/L and 30 micromol/L correspondingly in H460-N5 cells. A Nrf2 down-regulated cell line H460-N5 and a control cell line with GFP over-expression have been identified.Down-regulation of Nrf2 enhanced the cytotoxicity of Oxaliplatin, Doxorubicin and Etopside. The IC(50) value of Doxorubicin to H460-N0 cell was above 3 mg/L, but that to H460-N5 cell was about 2 mg/L. CONCLUSION: A Nrf2 down-regulated cell line H460-N5 and a control cell line with GFP over-expression have been identified. Down-regulation of Nrf2 enhanced the cytotoxicity of Oxaliplatin, Doxorubicin and Etopside.

[Down-regulation of Nrf2 enhances the cytotoxicity of Oxaliplatin to H460 cells].

OBJECTIVE: To establish a stable H460 cell line with Nrf2 down-regulation to study the role of Nrf2 in Oxaliplatin resistance. METHODS: Nrf2 down-regulated H460 cell line was obtained by transfecting cells with pRS-hNrf2 and followed by screening for Nrf2 expression by Western blotting. The cell lines were further characterized by analysing cellular GSH levels and cytotoxicity to anti-cancer drugs with MTS. RESULT: Nrf2 down-regulated H460 cell lines were established successfully. Cellular GSH level reduced significantly in the H460-C9 and H460-C13 compared to control cells (P(C9)= 0.00249, P(C13)= 0.03944). Down-regulation of Nrf2 in H460 sensitized the anti-cancer effect of Oxaliplatin and Doxorubicin. CONCLUSION: Nrf2 plays an important role in drug resistance. Down regulation of Nrf2 in H460 cell enhances cytotoxicity of Oxaliplatin.

[Effect of tBHQ and sulforaphane on Nrf2-ARE signaling pathway of Caco2 cells].

OBJECTIVE: To investigate the effect of tBHQ and sulforaphane on the protein expression in Nrf2-ARE signaling pathway of Caco2 cells. METHODS: Human colorectal carcinoma Caco2 cells were treated with 20 micromol/L tBHQ and 5 micromol/L sulforaphane (SFN) respectively. Real time PCR, Western blotting and immunoflourescence staining (IF) were performed to measure the target gene expression. RESULTS: Nrf2, AKR1C1 and NQO1 protein expressions were increased time-dependently in Caco2 cells after treatment with tBHQ and SFN. Time-course experiments showed that tBHQ and SFN increased the accumulation of Nrf2, and concomitantly increased the protein levels of AKR1C1 and NQO1. Real-time PCR and Western blotting showed that tBHQ and SFN significantly increased the expression of Nrf2 at 8h after the treatment, and AKR1C1 and NQO1 at 16 h. Confocal microscopy technique showed that Nrf2 accumulated in the nucleus at 6-8 h after treatment with tBHQ. After 1 h treatment with tBHQ the nuclear Nrf2 maintained at elevated level for at least 4 h with tBHQ withdrawn. CONCLUSION: tBHQ and SFN induced nuclear accumulation of Nrf2 and activated Nrf2-dependent regulation of ARE-mediated gene expression in Caco2 cells. In addition, the results provide experimental evidence for choosing the dose and frequency of the inducer in cancer chemoprevention study and in developing inhibitors of Nrf2-ARE signaling pathway.

[Effect of DRB/alpha-Amanitin on localization of Nrf2 in A549 cells].

OBJECTIVE: To investigate the effects of transcriptional inhibitors 5, 6-dichloro-1-b-D-ribofuranosylbenzimidazole (DRB) and alpha-Amanitin on the localization of Nrf2 in the nucleus. METHODS: A549 cells were treated with DRB (50 mg/L) or alpha-Amanitin (2.5 mg/L)for 1 h and 6 h in serum-free medium, respectively. The expressions of Nrf2, HO-1, NQO1 and AKR1C were detected by Western blotting analysis. The localization of Nrf2 was determined by laser scanning confocal microscopy after cells were treated with either DRB or agr:-Amanitin for 1 h. RESULTS: The expressions of Nrf2 and Nrf2-ARE gene batteries HO-1, AKR1C and NQO1 were decreased after 6 h treated with either DRB or alpha-Amanitin. The expression of SC35 was up-regulated but RNA Pol II was down-regulated; Y12 and NPC did not significantly change. The localization of Nrf2 in the cell nucleus did not change significantly. CONCLUSION: DRB and alpha-Amanitin can down-regulate the expression of Nrf2 and its targeting proteins HO-1, AKR1C and NQO1, but may have no effect on the localization of Nrf2.

[Effect of Luteolin and its combination with chemotherapeutic drugs on cytotoxicity of cancer cells].

OBJECTIVE: To investigate the effect of Luteolin alone or combination with chemotherapentic drugs on the cytoxicity of cancer cells. METHODS: Cultured A549, Hela, MCF-7, AGS, MGC-803, Caco2 and HepG2 cells were treated with Luteolin or the combination of Luteolin with other chemotherapeutic agents (Bexarotene, Cisplatin and Bleomycin). Cell viability was measured by MTS assay and IC(50) was calculated. RESULTS: The IC(50) of Bexarotene to Hela cells was 2 micromol/L, but with the combination of 5 micromol/L of Luteolin that reduced to 0.2 micromol/L. However, the combination of Bexarotene and Luteolin did not show significant benefit in MGC-803, HepG2 cells, Caco2 and MCF-7 cells. The IC(50) of Cisplatin to Hela cells was over 30 micromol/L,but it decreased to 3 micromol/L in the presence of 5 micromol/L Luteolin; Luteolin also sensitized Cisplatin in MGC-803, HepG2 and A549 cells studied. The IC(50) of Bleomycin to Hela cells was over 100 micromol/L, but it was about 1 micromol/L in the presence of 5 micromol/L Luteolin. A549 cells were resistant to Bleomycin with an IC(50) of 100 micromol/L, 10 micromol/L Luteolin greatly enhanced the cytotoxicity of Bleomycin to the cells with the IC(50) of about 10 micromol/L. The inhibitions of MGC-803, HepG2, A549 and AGS cells didn't change by combination of Luteolin. CONCLUSION: Low concentration of Luteolin has little toxic effect on the cancer cell lines tested in the study, but it can sensitize chemotherapeutic drugs in various cancer cell lines.