ABSTRACT
PURPOSE: Oxaliplatin is one of the most commonly used chemotherapeutic agents in the treatment of various cancers, including gastric cancer. It has, however, a narrow therapeutic index due to its toxicity and the occurrence of drug resistance. Therefore, there is a pressing need to develop novel therapies to potentiate the efficacy and reduce the toxicity of oxaliplatin. Piperlongumine (PL), an alkaloid isolated from Piper longum L., has recently been identified as a potent agent against cancer cells in vitro and in vivo. In the present study, we investigated whether PL can potentiate the antitumor effect of oxaliplatin in gastric cancer cells. METHODS: Cellular apoptosis and ROS levels were analyzed by flow cytometry. Thioredoxin reductase 1 (TrxR1) activity in gastric cancer cells or tumor tissues was determined using an endpoint insulin reduction assay. Western blotting was used to analyze the expression levels of the indicated proteins. Nude mice xenograft models were used to test the effects of PL and oxaliplatin combinations on gastric cancer cell growth in vivo. RESULTS: We found that PL significantly enhanced oxaliplatin-induced growth inhibition in both gastric and colon cancer cells. Moreover, we found that PL potentiated the antitumor effect of oxaliplatin by inhibiting TrxR1 activity. PL combined with oxaliplatin markedly suppressed the activity of TrxR1, resulting in the accumulation of ROS and, thereby, DNA damage induction and p38 and JNK signaling pathway activation. Pretreatment with antioxidant N-acetyl-L-cysteine (NAC) significantly abrogated the combined treatment-induced ROS generation, DNA damage and apoptosis. Importantly, we found that activation of the p38 and JNK signaling pathways prompted by PL and oxaliplatin was also reversed by NAC pretreatment. In vivo, we found that PL combined with oxaliplatin significantly suppressed tumor growth in a gastric cancer xenograft model, and effectively reduced the activity of TrxR1 in tumor tissues. Remarkably, we found that PL attenuated body weight loss evoked by oxaliplatin treatment. CONCLUSIONS: Our data support a synergistic effect of PL and oxaliplatin and suggest that application of its combination may be more effective for the treatment of gastric cancer than oxaliplatin alone.
Subject(s)
Antineoplastic Agents/pharmacology , Dioxolanes/pharmacology , Oxaliplatin/pharmacology , Reactive Oxygen Species/metabolism , Stomach Neoplasms/pathology , Animals , Apoptosis/drug effects , Cell Line, Tumor , Cell Proliferation/drug effects , DNA Damage , Drug Synergism , Female , Humans , MAP Kinase Signaling System/drug effects , Mice, Inbred BALB C , Mice, Nude , Models, Biological , Thioredoxin Reductase 1/metabolism , Xenograft Model Antitumor Assays , p38 Mitogen-Activated Protein Kinases/metabolismABSTRACT
Colon cancer is a malignant type of cancer with high prevalence and is one of the primary causes of cancer-related deaths. Oxaliplatin plays a significant role in the treatment of cancer, but the application of oxaliplatin is restricted due to its toxic side effects and drug resistance in clinical practice. Therefore, there is an urgent need for new strategies that can synergize with oxaliplatin for confronting colon cancer. Alantolactone (ALT), a natural sesquiterpene lactone, possesses antitumor properties in a number of cancer cell lines. In the present study, we investigated how ALT acts synergistically with oxaliplatin on human colorectal cancer HCT116 and RKO cells in vitro and in vivo. We observed that ALT strengthened the effect of oxaliplatin-induced growth restrain and apoptosis in HCT116 and RKO cells. It is through a mechanism concerning remarkable accumulation of intracellular reactive oxygen species (ROS) and activation of JNK and p38 MAPK signaling pathways. These changes ultimately induced apoptosis of HCT116 and RKO cells. Pretreatment of cells with the ROS reversal agent NAC significantly blocked the apoptosis induced by the combination treatment, and suppressed expression of JNK and p38 phosphorylation in HCT116 and RKO cells. In the xenograft model, the combination therapy displayed stronger antitumor activity compared with single agents. Immunohistochemistry of subsequent treatment tumors showed a significant decrease in proliferation as compared to either of the treatments alone. These results suggest that the combination treatment with ALT and oxaliplatin may become a potential therapeutic strategy for colon cancer.
Subject(s)
Apoptosis/drug effects , Colonic Neoplasms/metabolism , Lactones/pharmacology , Oxaliplatin/pharmacology , Reactive Oxygen Species/metabolism , Sesquiterpenes, Eudesmane/pharmacology , Cell Line, Tumor , Cell Proliferation/drug effects , Cell Survival/drug effects , Colorectal Neoplasms/metabolism , HCT116 Cells , Humans , MAP Kinase Signaling System/drug effectsABSTRACT
BACKGROUND: Cisplatin is one of the most widely used chemotherapeutic agents, but its efficacy is limited by its side effects. Hence, it is of great significance to develop novel agents to synergize with cisplatin and decrease side effects. In our previous study, we demonstrated that WZ35, a novel curcumin analogue, exhibited potent anti-cancer effects in vitro and in vivo. Here, we investigated whether WZ35 synergize to potentiate cisplatin activity in gastric cancer cells. METHODS: Cell apoptosis and cellular ROS levels were analyzed by flow cytometry. TrxR1 activity in gastric cells or tumor tissues was determined by the endpoint insulin reduction assay. Western blot was used to analyze the levels of indicated molecules. Nude mice xenograft model was used to test the effects of WZ35 and cisplatin combination on gastric cancer cell growth in vivo. RESULTS: We found that WZ35 significantly enhanced cisplatin-induced cell growth inhibition and apoptosis in gastric cancer cells. Further mechanism study showed that WZ35 synergized the anti-tumor effects of cisplatin by inhibiting TrxR1 activity. By inhibiting TrxR1 activity, WZ35 combined with cisplatin markedly induced the production of ROS, activated p38 and JNK signaling pathways, and eventually induced apoptosis of gastric cancer cells. In vivo, WZ35 combined with cisplatin significantly suppressed tumor growth in a gastric cancer xenograft model, and effectively reduced the activity of TrxR1 in tumor tissues. Remarkably, WZ35 attenuated the body weight loss evoked by cisplatin treatment. CONCLUSION: This study elucidated the underlying mechanisms of synergistic effect of WZ35 and cisplatin, and suggest that such a combinational treatment might potentially become a more effective regimen in gastric cancer therapy.
Subject(s)
Cell Proliferation/drug effects , Curcumin/analogs & derivatives , Curcumin/pharmacology , Stomach Neoplasms/drug therapy , Thioredoxin Reductase 1/genetics , Animals , Apoptosis/drug effects , Cell Line, Tumor , Cell Survival/drug effects , Cisplatin/pharmacology , Curcumin/therapeutic use , Endoplasmic Reticulum Stress , Gene Expression Regulation, Neoplastic/drug effects , Humans , MAP Kinase Signaling System/drug effects , Membrane Potential, Mitochondrial/drug effects , Mice , Proto-Oncogene Proteins c-bcl-2/genetics , Reactive Oxygen Species/metabolism , Stomach Neoplasms/genetics , Stomach Neoplasms/pathology , Xenograft Model Antitumor AssaysABSTRACT
Thioredoxin reductase 1 (TrxR1) has emerged as a potential target for cancer therapy, because it is overexpressed in several types of cancers and associated with increased tumour growth and poor patient prognosis. Alantolactone (ALT), a natural sesquiterpene lactone originated from traditional folk medicine Inula helenium L., has been reported to exert antitumor activity in various tumours. However, the effect of ALT on human gastric cancer cells and its underlying mechanism remains unknown. In this study, we showed that ALT inhibited cell proliferation and induced cell apoptosis in gastric cancer cells. Mechanistically, our data found that ALT induced reactive oxygen species (ROS) production by inhibiting TrxR1 activity, resulting in the activation of p38 mitogen-activated protein kinase (MAPK) pathway and eventually cell apoptosis in gastric cancer cells. And the effects of ALT were reversed by pre-treatment with NAC (a scavenger of ROS). Further investigation revealed that ALT displayed synergistic lethality with erastin against gastric cancer cells, which demonstrating combined inhibition of TrxR1 and glutathione (GSH) leads to a synergistic effect in gastric cancer cells. More importantly, ALT treatment markedly reduced the activity of TrxR1 in vivo and inhibited the growth of gastric cancer xenografts without exhibiting significant toxicity. Taken together, these findings suggest that ALT may be used as a novel therapeutic agent against human gastric cancer.
Subject(s)
Antineoplastic Agents, Phytogenic/pharmacology , Lactones/pharmacology , MAP Kinase Signaling System/drug effects , Reactive Oxygen Species/metabolism , Sesquiterpenes, Eudesmane/pharmacology , Stomach Neoplasms/drug therapy , Stomach Neoplasms/pathology , Thioredoxin Reductase 1/antagonists & inhibitors , p38 Mitogen-Activated Protein Kinases/metabolism , Animals , Antineoplastic Agents, Phytogenic/chemistry , Antineoplastic Agents, Phytogenic/isolation & purification , Apoptosis/drug effects , Cell Proliferation/drug effects , Cell Survival/drug effects , Dose-Response Relationship, Drug , Drug Screening Assays, Antitumor , Female , Humans , Inula/chemistry , Lactones/chemistry , Lactones/isolation & purification , Mice , Mice, Inbred BALB C , Mice, Nude , Neoplasms, Experimental/drug therapy , Neoplasms, Experimental/metabolism , Neoplasms, Experimental/pathology , Sesquiterpenes, Eudesmane/chemistry , Sesquiterpenes, Eudesmane/isolation & purification , Stomach Neoplasms/metabolism , Structure-Activity Relationship , Thioredoxin Reductase 1/metabolism , Tumor Cells, CulturedABSTRACT
Gastric cancer is one of the leading causes of cancer-related deaths. Chemotherapy has improved long-term survival of patients with gastric cancer. Unfortunately, cancer readily develops resistance to apoptosis-inducing agents. New mechanisms, inducing caspase-independent paraptosis-like cell death in cancer cells is presently emerging as a potential direction. We previously developed a curcumin analog B63 as an anti-cancer agent in pre-clinical evaluation. In the present study, we evaluated the effect and mechanism of B63 on gastric cancer cells. Our studies show that B63 targets TrxR1 protein and increases cellular reactive oxygen species (ROS) level, which results in halting gastric cancer cells and inducing caspase-independent paraptotic modes of death. The paraptosis induced by B63 was mediated by ROS-mediated ER stress and MAPK activation. Either overexpression of TrxR1 or suppression of ROS normalized B63-induced paraptosis in gastric cancer cells. Furthermore, B63 caused paraptosis in 5-fluorouracil-resistant gastric cancer cells, and B63 treatment reduced the growth of gastric cancer xenografts, which was associated with increased ROS and paraptosis. Collectively, our findings provide a novel strategy for the treatment of gastric cancer by utilizing TrxR1-mediated oxidative stress generation and subsequent cell paraptosis.
