Recently, several studies have shown that piperlongumine (PL) can selectively kill cancer cells by targeting reactive oxygen species (ROS). However, the potential therapeutic effects and detailed mechanism of PL in gastric cancer are still not clear. In the current report, we found that PL significantly suppressed gastric cancer both in vitro and in vivo. PL obviously increased ROS generation in gastric cancer cells. Anti-oxidant glutathione (GSH) and N-acetyl-L-cysteine (NAC) can abrogate PL-induced gastric cancer cell death and proliferation inhibition. GADD45α was induced in PL-treated cancer cells and led to G2/M phase arrest, whereas genetic depletion of GADD45α by small interfering RNAs (siRNAs) could partly reverse PL-induced cell cycle arrest in gastric cancer cells. Interestingly, we also found that PL treatment decreased the expression of telomerase reverse transcriptase (TERT) gene, which plays an essential role in cancer initiation and progression. Our findings thus revealed a potential anti-tumor effect of PL on gastric cancer cells and may have therapeutic implications.

Cucurbitacin-I (Cu-I, also known as Elatericin B or JSI-124) is developed to inhibit constitutive and abnormal activation of STAT3 in many cancers, demonstrating a potent anticancer activity by targeting disruption of STAT3 function. Here, we for the first time systematically studied the underlying molecular mechanisms of Cu-I-induced gastric cancer cell death both in vitro and in vivo. In our study, we show that Cu-I markedly inhibits gastric cancer cell growth by inducing G2/M phase cell cycle arrest and apoptosis at low nanomolar concentrations via a STAT3-independent mechanism. Notably, Cu-I significantly decreases intracellular GSH/GSSG ratio by inhibiting NRF2 pathway to break cellular redox homeostasis, and subsequently induces the expression of GADD45α in a p53-independent manner, and activates JNK/p38 MAPK signaling. Interestingly, Cu-I-induced GADD45α and JNK/p38 MAPK signaling form a positive feedback loop and can be reciprocally regulated by each other. Therefore, the present study provides new insights into the mechanisms of antitumor effects of Cu-I, supporting Cu-I as an attractive therapeutic drug in gastric cancer by modulating the redox balance.

In many gastric cancer patients, the disease is diagnosed in an advanced stage and therefore the mortality levels are high. Because there is a need to identify novel early diagnostic and prognostic biomarkers, we tested whether SIRT1 and STAT3 are good candidates. Towards this, we used patient tissues representing different stages of gastric cancer including gastric pre-cancerous lesions, early gastric cancer, and advanced gastric cancer, and probed SIRT1, STAT3 and phosphorylated STAT3 (pSTAT3) levels using immunohistochemistry. Our results revealed upregulated expression of SIRT1 in all stages of gastric cancer compared with noncancerous gastric mucosa, suggesting that high SIRT1 levels are likely involved in establishing gastric neoplasticity. However, STAT3 and pSTAT3 levels remained low until the gastric mucosa reached the tumor stage. Moreover, co-ordinated high expression of SIRT1 and STAT3 predicted poor overall survival for advanced gastric cancer patients. In addition, through analysis of gastric cancer patients from the TCGA dataset, we identified SIRT2 as an independent prognostic factor in gastric cancer patients. We postulate that SIRT1 and STAT3 are potential early diagnostic and prognostic markers of gastric cancer. Our study also shows that SIRT1 acts a gatekeeper during gastric tumorigenesis.

Background Ulcerative colitis (UC) is a common inflammatory bowel disease, during which cell necroptosis plays key roles in driving inflammation initiation and aggravation. Previous studies reported Receptor Interacting Protein Kinase 3 (RIP3)-mediated necroptosis in multiple diseases, and RIP3 protein in Paneth cells significantly enriched in the intestines of both humans and mice. Therefore, we hypothesized targeting RIP3 to inhibit necroptosis may depress UC. Methods We classified clinical UC samples according to the modified Truelove & Witts criterion. The expression of RIP3 was measured by western blot and immunohistochemistry. Cell proliferation and apoptosis were analyzed by MTT assay and flow cytometry. ROS production and the secretion of inflammatory cytokines were measured by DCFH-DA probe and ELISA assay. TLR4/MyD88/NF-κB signaling pathway was analyzed by western blot. We established experimental colitis model in RIP3 knockout and wild-type mice and disease activity index (DAI) score was calculated. The expression and distribution of tight junction protein were analyzed by immunofluorescence. The ratio of CD4+Foxp3+ T cells in the spleen was detected by flow cytometry. Oxidative damage of mouse colon was assessed by detecting the levels of SOD, MDA and MPO. Data were analyzed by one-way ANOVA or student’s t test. Results The expression of RIP3 in human colon is positively associated with the severity of UC. RIP3 inhibitor GSK872 or RIP3 knockdown reverses the inhibitory effect of TNF-α on proliferation and the promoting effect of TNF-α on apoptosis and necrosis in human intestinal epithelial cells. In addition, RIP3 deficiency inhibits the secretion of inflammatory cytokines (IL-16, IL-17 and IFN-γ) and ROS production induced by TNF-α. In vivo, RIP3 inhibitor Nec-1 effectively improves DSS-induced colitis in mice. In mechanism, RIP3 depression could upregulate the proportion of CD4+Foxp3+ immunosuppressive Treg cells in the spleen while suppressed TLR4/MyD88/NF-κB signaling pathway and ROS generation, and all these anti-inflammation factors together suppress the secretion of inflammatory cytokines and necroptosis of intestinal epithelial cells. Conclusions This study preliminarily explored the regulating mechanism of RIP3 on UC, and Nec-1 may be a promising drug to alleviate the inflammation and necroptosis of the colon in UC patients.