Plumbagin Triggers ER Stress-Mediated Apoptosis in Prostate Cancer Cells via Induction of ROS.

BACKGROUND/AIMS: Prostate cancer (PCa) is the second most frequently diagnosed cancer in men worldwide. Currently available therapies for hormone-refractory PCa are only marginally effective. Plumbagin (PLB), a natural naphthoquinone isolated from the traditional folk medicine Plumbago zeylanica, is known to selectively kill tumor cells. Nevertheless, antitumor mechanisms initiated by PLB in cancer cells have not been fully defined. METHODS: MTT assay was used to evaluate the effect of PLB on the viability of cancer cells. Cell apoptosis and reactive oxygen species (ROS) production were determined by flow cytometry. Protein expression was detected by western blotting. In vivo anti-tumor effect was measured by using tumor xenoqraft model in nude mice. RESULTS: In the present study, we found that PLB decreases cancer cell growth and induces apoptosis in DU145 and PC-3 cells. In addition, by increasing intracellular ROS levels, PLB induced a lethal endoplasmic reticulum stress response in PCa cells. Importantly, blockage of ROS production significantly reversed PLB-induced ER stress activation and cell apoptosis. In vivo, we found that PLB inhibits the growth of PCa xenografts without exhibiting toxicity Treatment of mice bearing human PCa xenografts with PLB was also associated with induction of ER stress activation. CONCLUSION: Inducing ER stress by PLB thus discloses a previously unrecognized mechanism underlying the biological activity of PLB and provides an in-depth insight into the action of PLB in the treatment of hormone-refractory PCa.

Curcumin analog L48H37 induces apoptosis through ROS-mediated endoplasmic reticulum stress and STAT3 pathways in human lung cancer cells.

Lung cancer is the leading cause of cancer-related deaths. Curcumin is a well-known natural product with anticancer ability, however, its poor bioavailability and pharmacokinetic profiles have limited its application in anticancer therapy. Previously, we reported that L48H37, a novel analog of curcumin with higher bioavailability, ameliorated LPS-induced inflammation, but the anticancer effect of L48H37 is still unknown. In the present study, we have investigated the effects of L48H37 in human lung cancer cells. Our results show that L48H37 decreases lung cancer cell growth and colony formation. These alterations were mediated through induction of G2/M cell cycle arrest and apoptosis in lung cancer cells. After L48H37 treatment, ER stress-related proteins were increased, and the expression of p-STAT3 was decreased in a dose-dependent manner. L48H37 also induced the accumulation of ROS in lung cancer cells, and pretreatment with NAC could fully reverse L48H37-induced reactive oxygen species (ROS) increase. Blocking ROS was able to reverse L48H37-induced endoplasmic reticulum (ER) stress, cell cycle arrest, and apoptosis. Finally, we show that L48H37 inhibits the growth of lung cancer xenografts without exhibiting toxicity. Treatment of mice bearing human lung cancer xenografts with L48H37 was also associated with indices of ER stress activation. In summary, our results provide evidence for a novel anti-tumor candidate for the treatment of lung cancer.

Selective killing of gastric cancer cells by a small molecule targeting ROS-mediated ER stress activation.

Gastric cancer is one of the leading causes of cancer mortality in the world. Curcumin is a natural product with multiple pharmacological activities, while its clinical application has been limited by the poor chemical stability. We have previously designed a series of curcumin derivatives with high stability and anticancer potentials. The present study aims to identify the anti-cancer effects and mechanisms of WZ26, an analog of curcumin, in gastric cancer cells. In vitro, WZ26 showed higher chemical stability and much stronger anti-proliferative effects than curcumin, accompanied by dose-dependent induction of cell cycle arrest and apoptosis in gastric cancer cells. Mechanistically, the novel compound WZ26 induced ROS production, resulting in the activation of JNK-mitochondrial and ER stress apoptotic pathways. Blockage of ROS production totally reversed WZ26-induced JNK activation, Bcl-2/Bax decrease, ER stress activation, and final cell apoptosis in SGC-7901 cells. WZ26 also exhibited potent anti-tumor effects in human gastric cancer cell xenograft models. WZ26 could be considered as a potential chemotherapeutic agent for the treatment of advanced gastric cancer. In addition, this study also demonstrated that ROS production could be act as a vital candidate pathway for inducing tumor cell apoptosis by targeting mitochondrial and ER stress-related death pathway. © 2015 Wiley Periodicals, Inc.

W346 inhibits cell growth, invasion, induces cycle arrest and potentiates apoptosis in human gastric cancer cells in vitro through the NF-κB signaling pathway.

The therapeutic agent selectively killing cancer cells is urgently needed for gastric cancer treatment. Curcumin has been investigated for its effect on the cancer treatment because of its significant therapeutic potential and safety profile. A synthetic unsymmetry mono-carbonyl compound termed W346 was developed from curcumin. In this study, we investigated the potential antineoplastic effect and mechanism of W346 against human gastric cancer cells. W346 suppressed the proliferation and invasion, blocked cell cycle arrest at G2/M phase, and increased apoptosis in gastric cancer cells, and it presented obviously improved anticancer activity than curcumin. Moreover, W346 effectively inhibited tumor necrosis factor (TNF-α)-induced NF-κB activation by suppressing IKK phosphorylation, inhibiting IκB-α degradation, and restraining the accumulation of NF-κB subunit p65 nuclear translocation. W346 also affected NF-κB-regulated downstream products involved in cycle arrest and apoptosis. In a word, W346 exhibited significantly improved anti-gastric cancer activity over curcumin by targeting NF-κB signaling pathway, and it is likely to be a promising starting point for the development of curcumin-based therapeutic agent.

The therapeutic potential of a novel non-ATP-competitive fibroblast growth factor receptor 1 inhibitor on gastric cancer.

Previous studies showed that fibroblast growth factor receptor 1 (FGFR1) is an attractive target in gastric cancer therapy. In the current study, we aimed to investigate whether the compound L6123, a novel non-ATP-competitive FGFR1 inhibitor, could show better antitumor activity than the leading compound, nordihydroguaiaretic acid (NDGA), in FGFR1-overexpressing gastric cancer cells. Using an MTT assay, we investigated the inhibitory effect of L6123 on the viability of three gastric cancer cells (MGC-803, SGC-7901, and BGC-823) overexpressing FGFR1, wild-type mouse embryonic fibroblast (MEF), and MEF expressing FGFR1, FGFR2, and FRS2α gene knockout (MEF). We studied the antitumor mechanism of L6123 against the gastric cancer cell line SGC-7901 by western blot analysis. The antitumor effects of L6123 on the gastric cancer cell line SGC-7901 were detected by flow cytometry, Hoechst staining, western blot analysis, and Transwell invasion assay. L6123 had lower IC50 in all three gastric cancer cells than NDGA and showed better inhibitory activity against MEF cells than against MEF cells. In the SGC-7901 gastric cell, L6123 inhibited the FGF2-induced phosphorylation of FGFR1/FRS2α/ERK1/2 in a dose-dependent manner, induced the activation of the apoptosis-related proteins, cleaved-PARP and cleaved-caspase-3, decreased the expression of pro-caspase-3 and Bcl-2, and induced tumor cell apoptosis. L6123 also dose-dependently reduced cell invasion ability, and showed better activity than NDGA at the same concentration. A novel non-ATP-competitive inhibitor L6123 showed excellent antigastric cancer activity by inhibiting the FGFR1 signaling pathway. Thus, we discovered a potential agent for the treatment of FGFR1-overexpressing gastric cancer.

Combination of TrxR1 inhibitor and lenvatinib triggers ROS-dependent cell death in human lung cancer cells.

Lung cancer is one of the most lethal diseases in the world. Although there has been significant progress in the treatment of lung cancer, there is still a lack of effective strategies for advanced cases. Lenvatinib, a multi-targeted tyrosine kinase inhibitor, has achieved much attention due to its antitumor properties. Nevertheless, the use of lenvatinib is restricted by the characteristics of poor efficacy and drug resistance. In this study, we assessed the effectiveness of lenvatinib combined with thioredoxin reductase 1 (TrxR1) inhibitors in human lung cancer cells. Our results indicate that the combination therapy involving TrxR1 inhibitors and lenvatinib exhibited significant synergistic antitumor effects in human lung cancer cells. Moreover, siTrxR1 also showed significant synergy with lenvatinib in lung cancer cells. Mechanically, we demonstrated that ROS accumulation significantly contributes to the synergism between lenvatinib and TrxR1 inhibitor auranofin. Furthermore, the combination of lenvatinib and auranofin can activate endoplasmic reticulum stress and JNK signaling pathways to achieve the goal of killing lung cancer cells. Importantly, combination therapy with lenvatinib and auranofin exerted a synergistic antitumor effect in vivo. To sum up, the combination therapy involving lenvatinib and auranofin may be a potential strategy for treating lung cancer.

Synergistic targeting of TrxR1 and ATM/AKT pathway in human colon cancer cells.

Thioredoxin reductase 1 (TrxR1) has emerged as a promising target for cancer therapy. In our previous research, we discovered several new TrxR1 inhibitors and found that they all have excellent anti-tumor activity. At the same time, we found these TrxR1 inhibitors all lead to an increase in AKT phosphorylation in cancer cells, but the detailed role of AKT phosphorylation in TrxR1 inhibitor-mediated cell death remains unclear. In this study, we identified the combination of AKT and TrxR1 inhibitor displayed a strong synergistic effect in colon cancer cells. Furthermore, we demonstrated that the synergistic effect of auranofin (TrxR1 inhibitor) and MK-2206 (AKT inhibitor) was caused by ROS accumulation. Importantly, we found that ATM inhibitor KU-55933 can block the increase of AKT phosphorylation caused by auranofin, and exhibited a synergistic effect with auranofin. Taken together, our study demonstrated that the activation of ATM/AKT pathway is a compensatory mechanism to cope with ROS accumulation induced by TrxR1 inhibitor, and synergistic targeting of TrxR1 and ATM/AKT pathway is a promising strategy for treating colon cancer.

Combination therapy with HSP90 inhibitors and piperlongumine promotes ROS-mediated ER stress in colon cancer cells.

Colon cancer is a major cause of cancer-related death. Despite recent improvements in the treatment of colon cancer, new strategies to improve the overall survival of patients are urgently needed. Heat shock protein 90 (HSP90) is widely recognized as a promising target for treating various cancers, including colon cancer. However, no HSP90 inhibitor has been approved for clinical use due to limited efficacy. In this study, we evaluated the antitumor activities of HSP90 inhibitors in combination with piperlongumine in colon cancer cells. We show that combination treatment with HSP90 inhibitors and piperlongumine displayed strong synergistic interaction in colon cancer cells. These agents synergize by promoting ER stress, JNK activation, and DNA damage. This process is fueled by oxidative stress, which is caused by the accumulation of reactive oxygen species. These studies nominated piperlongumine as a promising agent for HSP90 inhibitor-based combination therapy against colon cancer.

Compensatory combination of mTOR and TrxR inhibitors to cause oxidative stress and regression of tumors.

Background: Cancer is a leading cause of death worldwide. Extensive research over decades has led to the development of therapies that inhibit oncogenic signaling pathways. The mammalian target of rapamycin (mTOR) signaling pathway plays an important role in the development of many cancers. Several mTOR inhibitors are approved for the treatment of cancers. However, the anticancer efficacies of mTOR inhibitor monotherapy are still limited. Methods: Western blot was used to detect the expression of indicated molecules. Thioredoxin reductase (TrxR) activity in cells was determined by the endpoint insulin reduction assay. Immunofluorescence staining was used to analyze precise location and expression of target proteins. Nude mice were used for xenograft tumor models. Results: We identified a synergistic lethal interaction of mTOR and TrxR inhibitors and elucidated the underlying molecular mechanisms of this synergism. We demonstrated that mTOR and TrxR inhibitors cooperated to induce cell death by triggering oxidative stress, which led to activation of autophagy, endoplasmic reticulum (ER) stress and c-Jun N-terminal Kinase (JNK) signaling pathway in cancer cells. Remarkably, we found that auranofin (AF) combined with everolimus significantly suppressed tumor growth in HCT116 and SGC-7901 xenograft models with no significant signs of toxicity. Conclusion: Our findings identify a promising therapeutic combination for cancer and has important implications for developing mTOR inhibitor-based combination treatments.

Curcumin analog, WZ37, promotes G2/M arrest and apoptosis of HNSCC cells through Akt/mTOR inhibition.

Head and neck squamous cell carcinoma (HNSCC) is a leading form of malignancy arising from the head and neck region. Existing conventional therapies are toxic and induce resistance to advanced HNSCC, therefore, new highly efficient therapeutic agents are urgently needed. The present study investigated the anti-cancer efficacy of WZ37, a curcumin analog, in HNSCC cell lines, and defined the mechanism of this activity. Results indicated that WZ37 inhibited proliferation of several HNSCC cell types by G2/M cycle arrest, promoted expression of a pro-apoptotic protein profile, and induced ROS-dependent mitochondrial injury and ER stress. Pre-treatment with NAC, an ROS scavenger, lowered the anti-cancer activity of WZ37 in HEP-2 cells. Long-term treatment of WZ37 (24 h) decreased Akt/mTOR phosphorylation which was accompanied by increased expression of BAD and PTEN. Moreover, co-treatment of WZ37 with MK-2206 (Akt inhibitor) promoted cancer cell apoptosis. Our findings indicated that the anti-cancer potential of WZ37 was attributed to ROS-dependent cell cycle arrest, mitochondrial injury, and ER stress, leading to apoptosis. The basis of the HNSCC cell apoptosis was through a mechanism of inhibition of the oxidant-sensitive Akt/mTOR pathway. We conclude that WZ37 can be a promising anti-cancer agent for the treatment of HNSCC.

Isodeoxyelephantopin Inactivates Thioredoxin Reductase 1 and Activates ROS-Mediated JNK Signaling Pathway to Exacerbate Cisplatin Effectiveness in Human Colon Cancer Cells.

Colon cancer is one of the leading causes of cancer-related death in the world. The development of new drugs and therapeutic strategies for patients with colon cancer are urgently needed. Isodeoxyelephantopin (ESI), a sesquiterpene lactone isolated from the medicinal plant Elephantopus scaber L., has been reported to exert antitumor effects on several cancer cells. However, the molecular mechanisms underlying the action of ESI is still elusive. In the present study, we found that ESI potently suppressed cell proliferation in human colon cancer cells. Furthermore, our results showed that ESI treatment markedly increased cellular reactive oxygen species (ROS) levels by inhibiting thioredoxin reductase 1 (TrxR1) activity, which leads to activation of the JNK signaling pathway and eventually cell death in HCT116 and RKO cells. Importantly, we found that ESI markedly enhanced cisplatin-induced cytotoxicity in HCT116 and RKO cells. Combination of ESI and cisplatin significantly increased the production of ROS, resulting in activation of the JNK signaling pathway in HCT116 and RKO cells. In vivo, we found that ESI combined with cisplatin significantly suppressed tumor growth in HCT116 xenograft models. Together, our study provide a preclinical proof-of-concept for ESI as a potential strategy for colon cancer treatment.

Piperlongumine potentiates the antitumor efficacy of oxaliplatin through ROS induction in gastric cancer cells.

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.

Enhancement of oxaliplatin-induced colon cancer cell apoptosis by alantolactone, a natural product inducer of ROS.

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.

Curcuminoid WZ35 synergize with cisplatin by inducing ROS production and inhibiting TrxR1 activity in gastric cancer cells.

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.

Potent inhibition of gastric cancer cells by a natural compound via inhibiting TrxR1 activity and activating ROS-mediated p38 MAPK pathway.

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.

Curcuminoid WZ26, a TrxR1 inhibitor, effectively inhibits colon cancer cell growth and enhances cisplatin-induced cell death through the induction of ROS.

Colon cancer is one of the leading causes of cancer-related deaths. Chemotherapy has improved survival in patients with colon cancer, but has a narrow therapeutic window due to its toxicity. Therefore, novel therapies for colon cancer are urgently needed. We previously developed a curcumin analog WZ26 as an anti-cancer agent in pre-clinical evaluation. In the present study, we further explored the mechanism and target of WZ26 in colon cancer cells. Our results show that WZ26 targets thioredoxin reductase 1 (TrxR1) and increases cellular reactive oxygen species (ROS) levels, which results in the activation of JNK signaling pathway in human colon cancer cells. Furthermore, we found that WZ26 significantly enhances cisplatin-induced cell growth inhibition in colon cancer cells. WZ26 combined with cisplatin markedly increases the accumulation of ROS, and thereby induces DNA damage and activation of JNK signaling pathway. Pretreatment with antioxidant N-acetyl-l-cysteine (NAC) significantly abrogates the combined treatment-induced ROS generation, DNA damage and cell death. In addition, the activation of JNK signaling pathway prompted by WZ26 and cisplatin was also reversed by NAC pretreatment. In vivo, WZ26 combined with cisplatin significantly inhibits tumor growth in a colon cancer xenograft model. Remarkably, WZ26 attenuates the body weight loss evoked by cisplatin treatment. This study discloses a previously unrecognized mechanism underlying the biological activity of WZ26, and reveals that WZ26 and cisplatin combinational treatment might potentially become a more effective regimen in colon cancer therapy.

Piperlongumine as a direct TrxR1 inhibitor with suppressive activity against gastric cancer.

Piperlongumine (PL), a natural alkaloid isolated from the fruit of long pepper, is known to selectively kill tumor cells while sparing their normal counterparts. However, the cellular target and potent anticancer efficacy of PL in numerous types of human cancer cells have not been fully defined. We report here that PL may interact with the thioredoxin reductase 1 (TrxR1), an important selenocysteine (Sec)-containing antioxidant enzyme, to induce reactive oxygen species (ROS)-mediated apoptosis in human gastric cancer cells. By inhibiting TrxR1 activity and increasing intracellular ROS levels, PL induces a lethal endoplasmic reticulum stress and mitochondrial dysfunction in human gastric cancer cells. Importantly, knockdown of TrxR1 sensitizes cells to PL treatment, and PL displays synergistic lethality with GSH inhibitors (BSO and Erastin) against gastric cancer cells. In vivo, PL treatment markedly reduces the TrxR1 activity and tumor cell burden. Remarkably, TrxR1 was significantly overexpressed in gastric cancer cell lines and human gastric cancer tissues. Targeting TrxR1 with PL thus discloses a previously unrecognized mechanism underlying the biological activity of PL and provides an in-depth insight into the action of PL in the treatment of gastric cancer.

Da0324, an inhibitor of nuclear factor-κB activation, demonstrates selective antitumor activity on human gastric cancer cells.

BACKGROUND: The transcription factor nuclear factor-κB (NF-κB) is constitutively activated in a variety of human cancers, including gastric cancer. NF-κB inhibitors that selectively kill cancer cells are urgently needed for cancer treatment. Curcumin is a potent inhibitor of NF-κB activation. Unfortunately, the therapeutic potential of curcumin is limited by its relatively low potency and poor cellular bioavailability. In this study, we presented a novel NF-κB inhibitor named Da0324, a synthetic asymmetric mono-carbonyl analog of curcumin. The purpose of this study is to research the expression of NF-κB in gastric cancer and the antitumor activity and mechanism of Da0324 on human gastric cancer cells. METHODS: The expressions between gastric cancer tissues/cells and normal gastric tissues/cells of NF-κB were evaluated by Western blot. The inhibition viability of compounds on human gastric cancer cell lines SGC-7901, BGC-823, MGC-803, and normal gastric mucosa epithelial cell line GES-1 was assessed with the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. Absorption spectrum method and high-performance liquid chromatography method detected the stability of the compound in vitro. The compound-induced changes of inducible NF-κB activation in the SGC-7901 and BGC-823 cells were examined by Western blot analysis and immunofluorescence methods. The antitumor activity of compound was performed by clonogenic assay, matrigel invasion assay, flow cytometric analysis, Western blot analysis, and Hoechst 33258 staining assay. RESULTS: High levels of p65 were found in gastric cancer tissues and cells. Da0324 displayed higher growth inhibition against several types of gastric cancer cell lines and showed relatively low toxicity to GES-1. Moreover, Da0324 was more stable than curcumin in vitro. Western blot analysis and immunofluorescence methods showed that Da0324 blocked NF-κB activation. In addition, Da0324 significantly inhibited tumor proliferation and invasion, arrested the cell cycle, and induced apoptosis in vitro. CONCLUSION: The asymmetric mono-carbonyl analog of curcumin Da0324 exhibited significantly improved antigastric cancer activity. Da0324 may be a promising NF-κB inhibitor for the selective targeting of cancer cells. However, further studies are needed in animals to validate these findings for the therapeutic use of Da0324.

EF24 induces ROS-mediated apoptosis via targeting thioredoxin reductase 1 in gastric cancer cells.

Gastric cancer (GC) is one of the leading causes of cancer mortality in the world, and finding novel agents for the treatment of advanced gastric cancer is of urgent need. Diphenyl difluoroketone (EF24), a molecule having structural similarity to curcumin, exhibits potent anti-tumor activities by arresting cell cycle and inducing apoptosis. Although EF24 demonstrates potent anticancer effïcacy in numerous types of human cancer cells, the cellular targets of EF24 have not been fully defined. We report here that EF24 may interact with the thioredoxin reductase 1 (TrxR1), an important selenocysteine (Sec)-containing antioxidant enzyme, to induce reactive oxygen species (ROS)-mediated apoptosis in human gastric cancer cells. By inhibiting TrxR1 activity and increasing intracellular ROS levels, EF24 induces a lethal endoplasmic reticulum stress in human gastric cancer cells. Importantly, knockdown of TrxR1 sensitizes cells to EF24 treatment. In vivo, EF24 treatment markedly reduces the TrxR1 activity and tumor cell burden, and displays synergistic lethality with 5-FU against gastric cancer cells. Targeting TrxR1 with EF24 thus discloses a previously unrecognized mechanism underlying the biological activity of EF24, and reveals that TrxR1 is a good target for gastric cancer therapy.

ROS generation mediates the anti-cancer effects of WZ35 via activating JNK and ER stress apoptotic pathways in gastric cancer.

Gastric cancer is one of the leading causes of cancer mortality in the world, and finding novel agents and strategies for the treatment of advanced gastric cancer is of urgent need. Curcumin is a well-known natural product with anti-cancer ability, but is limited by its poor chemical stability. In this study, an analog of curcumin with high chemical stability, WZ35, was designed and evaluated for its anti-cancer effects and underlying mechanisms against human gastric cancer. WZ35 showed much stronger anti-proliferative effects than curcumin, accompanied by dose-dependent induction of cell cycle arrest and apoptosis in gastric cancer cells. Mechanistically, our data showed that WZ35 induced reactive oxygen species (ROS) production, resulting in the activation of both JNK-mitochondrial and ER stress apoptotic pathways and eventually cell apoptosis in SGC-7901 cells. Blockage of ROS production totally reversed WZ35-induced JNK and ER stress activation as well as cancer cell apoptosis. In vivo, WZ35 showed a significant reduction in SGC-7901 xenograft tumor size in a dose-dependent manner. Taken together, this work provides a novel anticancer candidate for the treatment of gastric cancer, and importantly, reveals that increased ROS generation might be an effective strategy in human gastric cancer treatment.