Fei Zhong

MicroRNAs as promising biomarkers for gastric cancer.

Despite promising developments of treatment, the overall outcome of gastric cancer (GC) remains poor. Current tumor markers are not ideal due to relatively low sensitivity and specificity. There is an urgent need for identifying more specific and more sensitive novel markers in the clinical management of GC. MicroRNAs (miRNAs) are non-coding RNA molecules. Recently, miRNA studies have quickly moved from basic molecular research of cancer to areas of clinical application. On the basis of recent data, the present review mainly summarizes the potential role of miRNAs as molecular biomarkers for disease susceptibility, diagnosis, prognosis and drug-response prediction in GC. This review also highlights the miRNA expression profiles in GC and their relation to cancer classification and subtype stratification. Although there are still many challenges in the research field of tumor-related miRNAs, the small molecules will definitely improve the clinical management of GC in the future.

Melatonin sensitizes human hepatoma cells to endoplasmic reticulum stress-induced apoptosis.

Abstract:  Endoplasmic reticulum stress–mediated cell apoptosis is implicated in the development of cancer. Melatonin induces apoptosis in hepatocellular carcinoma (HCC) in experimental studies, but the effects of melatonin on endoplasmic reticulum (ER) stress–induced apoptosis in HCC have not been tested. Differences in ER stress–induced apoptosis in human hepatoma cells and normal human hepatocyte were investigated by exposure to tunicamycin (ER stress inducer). Significant differences were observed in the rate of apoptosis between HepG2 cells (hepatoma cells) and HL‐7702 cells (normal human hepatocyte cells). The expression of cyclooxygenase‐2 (COX‐2) was increased in HepG2 cells but not in HL‐7702 cells. Furthermore, down‐regulation of COX‐2 expression using the COX‐2 inhibitor, celecoxib, increased tunicamycin‐induced apoptosis concomitant with the up‐regulation of pro‐apoptotic transcription factor CHOP (GADD153) and down‐regulation of B‐cell lymphoma 2/Bcl‐2–associated X protein (Bcl‐2/Bax) ratio, suggesting that inhibition of COX‐2 sensitized human hepatoma cells to ER stress–induced apoptosis. Interestingly, co‐treatment with tunicamycin and melatonin also decreased the expression of COX‐2 and significantly increased the rate of apoptosis by elevating the levels of CHOP and reducing the Bcl‐2/Bax ratio. These results demonstrate that melatonin sensitizes human hepatoma cells to ER stress–induced apoptosis by down‐regulating COX‐2 expression, increasing the levels of CHOP and decreasing the Bcl‐2/Bax ratio.

Melatonin reverses tunicamycin-induced endoplasmic reticulum stress in human hepatocellular carcinoma cells and improves cytotoxic response to doxorubicin by increasing CHOP and decreasing survivin.

Chemoresistance in hepatocellular carcinoma (HCC) is associated with multiple cellular responses to environmental stresses, such as nutrient deprivation and hypoxia. Nevertheless, whether ER stress resulting from nutrient deprivation and tumor hypoxia contributes to drug resistance remains unclear. Melatonin increased the efficacy of chemotherapeutic drugs in hepatocellular carcinoma in our previous studies. However, the effects of melatonin on endoplasmic reticulum (ER) stress‐induced resistance to chemotherapeutic agents in HCC have not been tested. The effect of the endoplasmic reticulum (ER) stress response during resistance of human hepatocellular carcinoma cells against doxorubicin was investigated in this study. Pretreatment of HepG2 and SMMC‐7721 cells (two human hepatocellular carcinoma cell lines) with tunicamycin, an ER stress inducer, drastically decreased the rate of apoptosis generated by doxorubicin. Interestingly, co‐pretreatment with tunicamycin and melatonin significantly increased apoptosis induced by doxorubicin. Simultaneously, the expression of phosphorylated AKT (p‐AKT) was elevated in HepG2 and SMMC‐7721 cells given tunicamycin but reduced in the presence of melatonin. Furthermore, consistent with inhibition of AKT activation by using the PI3K inhibitor LY294002, melatonin elevated the levels of CHOP (C/EBP‐homologous protein) and reduced the levels of Survivin (a member of the inhibitor of apoptosis protein family)suggesting that inhibition of the PI3K/AKT pathway by melatonin‐reversed ER stress‐induced resistance to doxorubicin in human hepatocellular carcinoma cells. These results demonstrate that melatonin attenuates ER stress‐induced resistance to doxorubicin in human hepatocellular carcinoma cells by down‐regulating the PI3K/AKT pathway, increasing the levels of CHOP and decreasing the levels of Survivin.

Endoplasmic reticulum stress-induced resistance to doxorubicin is reversed by paeonol treatment in human hepatocellular carcinoma cells.

Background Endoplasmic reticulum stress (ER stress) is generally activated in solid tumors and results in tumor cell anti-apoptosis and drug resistance. Paeonol (Pae, 2-hydroxy-4-methoxyacetophenone), is a natural product extracted from the root of Paeonia Suffruticosa Andrew. Although Pae displays anti-neoplastic activity and increases the efficacy of chemotherapeutic drugs in various cell lines and in animal models, studies related to the effect of Pae on ER stress–induced resistance to chemotherapeutic agents in hepatocellular carcinoma (HCC) are poorly understood. Methodology/Principal Findings In this study, we investigated the effect of the endoplasmic reticulum (ER) stress response during resistance of human hepatocellular carcinoma cells to doxorubicin. Treatment with the ER stress-inducer tunicamycin (TM) before the addition of doxorubicin reduced the rate of apoptosis induced by doxorubicin. Interestingly, co-pretreatment with tunicamycin and Pae significantly increased apoptosis induced by doxorubicin. Furthermore, induction of ER stress resulted in increasing expression of COX-2 concomitant with inactivation of Akt and up-regulation of the pro-apoptotic transcription factor CHOP (GADD153) in HepG2 cells. These cellular changes in gene expression and Akt activation may be an important resistance mechanism against doxorubicin in hepatocellular carcinoma cells undergoing ER stress. However, co-pretreatment with tunicamycin and Pae decreased the expression of COX-2 and levels of activation of Akt as well as increasing the levels of CHOP in HCC cells. Conclusions/Significance Our results demonstrate that Pae reverses ER stress–induced resistance to doxorubicin in human hepatocellular carcinoma cells by targeting COX-2 mediated inactivation of PI3K/AKT/CHOP.

Melatonin overcomes apoptosis resistance in human hepatocellular carcinoma by targeting Survivin and XIAP

Apoptosis resistance in hepatocellular carcinoma (HCC) is one of the most significant factors for hepatocarcinogenesis and tumor progression, and leads to resistance to conventional chemotherapy. It is well known that inhibitor of apoptosis proteins (IAPs) play key roles in apoptosis resistance, it has become an important target for antitumor therapy. In this study, we examined if melatonin, the main secretory product of the pineal gland, targeted IAPs, leading to the inhibition of apoptosis resistance. To accomplish this, we first observed that four members of IAPs (cIAP‐1, cIAP‐2, Survivin, and XIAP) were overexpressed in human HCC tissue. Interestingly, melatonin significantly inhibited the growth of HepG2 and SMMC‐7721 cells and promoted apoptosis along with the downregulation of Survivin and XIAP, but had no effect on the expression of cIAP‐1 and cIAP‐2. These data suggest that the inhibition of Survivin and XIAP by melatonin may play an important part in reversing apoptosis resistance. Notably, cIAP‐1, Survivin and XIAP were significantly associated with the coexpression of COX‐2 in human HCC specimens. Melatonin also reduced the expression of COX‐2 and inhibited AKT activation in HepG2 and SMMC‐7721 cells. Inhibition of COX‐2 activity with the selective inhibitor, NS398, and inhibition of AKT activation using the PI3K inhibitor, LY294002, in tumor cells confirmed that melatonin‐induced apoptosis was COX‐2/PI3K/AKT‐dependent, suggesting that the COX‐2/PI3K/AKT pathway plays a role in melatonin inhibition of IAPs. Taken together, these results suggest that melatonin overcomes apoptosis resistance by the suppressing Survivin and XIAP via the COX‐2/PI3K/AKT pathway in HCC cells.

Protective Role of Helicobacter pylori Infection in Prognosis of Gastric Cancer: Evidence from 2454 Patients with Gastric Cancer

Background A number of studies have investigated the association between Helicobacter pylori (H. pylori) infection and the prognosis of gastric cancer (GC), with inconsistent and inconclusive results. We performed a meta-analysis to derive a more precise estimation of the association. Methodology/Principal Findings A systematic search of PubMed, EMBASE, Cochrane and Chinese wanfang databases was performed with the last search updated on February 19, 2013. The hazard ratio (HR) and its 95% confidence interval (95%CI) were used to assess the strength of association. A total of 12 studies including 2454 patients with GC were involved in this meta-analysis. The pooled HR was 0.71 (95%CI: 0.57–0.87; P = 0.001) for OS and 0.60 (95%CI: 0.30–1.18; P = 0.139) for DFS in GC patients, respectively. The protective role of H. pylori infection in the prognosis of GC was also observed among different subgroups stratified by ethnicity, statistical methodology, H. pylori evaluation method and quality assessment. There was no evidence of publication bias. Conclusions/Significance This meta-analysis suggests a protective role for H. pylori infection in the prognosis of GC. The underlying mechanisms need to be further elucidated, which could provide new therapeutic approaches for GC.

Melatonin, a novel selective ATF-6 inhibitor, induces human hepatoma cell apoptosis through COX-2 downregulation

AIM To clarify the mechanisms involved in the critical endoplasmic reticulum (ER) stress initiating unfolded protein response pathway modified by melatonin. METHODS Hepatoma cells, HepG2, were cultured in vitro. Flow cytometry and TUNEL assay were used to measure HepG2 cell apoptosis. Western blotting and quantitative reverse transcription-polymerase chain reaction methods were used to determine the protein and messenger RNA levels of ER stress and apoptosis related genes’ expression, respectively. Tissue microarray construction from patients was verified by immunohistochemical analysis. RESULTS In the present study, we first identified that melatonin selectively blocked activating transcription factor 6 (ATF-6) and then inhibited cyclooxygenase-2 (COX-2) expression, leading to enhanced liver cancer cell apoptosis under ER stress condition. Dramatically increased CCAAT-enhancer-binding protein homologous protein level, suppressed COX-2 and decreased Bcl-2/Bax ratio by melatonin or ATF-6 siRNA contributed the enhanced HepG2 cell apoptosis under tunicamycin (an ER stress inducer) stimulation. In clinical hepatocellular carcinoma patients, the close relationship between ATF-6 and COX-2 was further confirmed. CONCLUSION These findings indicate that melatonin as a novel selective ATF-6 inhibitor can sensitize human hepatoma cells to ER stress inducing apoptosis.

Helicobacter pylori infection predicts favorable outcome in patients with gastric cancer.

BACKGROUND Recent studies have suggested a controversial role of Helicobacter pylori infection in gastric cancer prognosis. The aim of the present study was to investigate the potential impact of H. pylori status on the prognosis of patients with gastric cancer in a Chinese prospective cohort. METHODS Between 2007 and 2009, 261 patients with curatively resected gastric cancer were enrolled in the study. H. pylori status was defined by means of immunohistochemical staining in tumour and non-neoplastic tissues. Treatment prognosis was measured in terms of cancer-specific survival and disease-free survival (dfs). Univariate and multivariate Cox regression models were used to assess the association between H. pylori status and patient prognosis. RESULTS Positivity for H. pylori infection was observed in 188 of the 261 patients (72.0%). In patients positive for H. pylori, mean cancer-specific survival was 55.2 months [95% confidence interval (ci): 53.4 to 56.9 months] and mean dfs was 53.9 months (95% ci: 51.8 to 56.0 months); the same survivals were, respectively, 45.1 months (95% ci: 42.2 to 47.9 months) and 43.7 months (95% ci: 40.4 to 47.0 months) in patients negative for H. pylori. In univariate analysis, positive H. pylori status was associated with better cancer-specific survival [hazard ratio (hr): 0.486; 95% ci: 0.271 to 0.870; p = 0.015] and dfs (hr: 0.540; 95% ci: 0.307 to 0.950; p = 0.033). In multivariate analysis, H. pylori was an independent prognostic factor for cancer-specific survival (hr: 0.485; 95% ci: 0.265 to 0.889; p = 0.019). CONCLUSIONS Our study demonstrates that positive H. pylori status is a beneficial prognostic indicator in patients with gastric cancer and might suggest possible therapeutic approaches for gastric cancer. Further research is required to better understand inflammation mechanisms and cancer progression.