Cardiac glycoside sensitized hepatocellular carcinoma cells to TRAIL via ROS generation,p38MAPK,mitochondrial transition,and autophagy mediation

A major concern in the clinical application of tumor necrosis factor related apoptosis‐inducing ligand (TRAIL) in tumors is the development of resistance. Therefore, agents that can potentially restore TRAIL sensitivity are important therapeutic targets for cancer treatment. Herein, we evaluated lanatoside c and digoxin, both of which are widely used cardiac glycosides (CGs), for their ability to sensitize human hepatocellular carcinoma cells (Huh‐7 and HepG2) through TRAIL‐induced apoptosis. CGs functionalize TRAIL as shown by its effect on intracellular reactive oxygen species (ROS) generation, which damages mitochondrial integrity and thereby confers intrinsic apoptotic caspase cascade during combined treatment. Caspase activation is dependent on ROS as shown by the ability of CGs to generate ROS and the ROS‐N‐acetylcysteine (NAC) relationship, which inhibits apoptosis during cotreatment by preventing the formation of caspase‐8 and ‐3. Furthermore, CGs triggered p38MAPK phosphorylation and NAC pre‐exposure blocked p38MAPK phosphorylation, which demonstrated that p38MAPK was dependent upon ROS generation. Additionally, CGs were found to be potent inducers of AMPK‐mediated protective autophagy as pharmacological and genetic autophagy inhibition reached the higher threshold of TRAIL‐mediated apoptosis. Finally, CGs downregulated the expression of the antiapoptotic protein Bcl‐2 and increased the translocation of proapoptotic protein cytochrome c, thereby inducing apoptosis. Collectively, these results indicate that CGs potentiate the enhanced cytotoxic capacity to TRAIL through ROS generation, p38MAPK phosphorylation, cell survival protein downregulation, and protective autophagy inhibition.     

OPB-31121, a novel small molecular inhibitor,disrupts the JAK2/STAT3 pathway and exhibits an antitumor activity in gastric cancer cells

We investigated the mechanisms of action and antitumor effects of OPB-31121, a novel STAT3 inhibitor, in gastric cancer cells. OPB-31121 downregulated JAK2 and gp130 expression and inhibited JAK2 phosphorylation which leads to inhibition of STAT3 phosphorylation. OPB-31121 inhibited constitutively activated and IL-6-induced JAK/STAT signaling pathway. OPB-31121 decreased cell proliferation in both gastric cancer cells and in a xenograft model, induced the apoptosis of gastric cancer cells, inhibited the expression of antiapoptotic proteins, and showed synergism with 5-fluorouracil and cisplatin. Taken together, our study suggests that STAT3 inhibition with OPB-31121 can be tested in patients with gastric cancer.     

Redox control of manumycin A-induced apoptosis in anaplastic thyroid cancer cells: involvement of the xenobiotic apoptotic pathway

Our previous studies demonstrated that manumycin A, a farnesyltransferase inhibitor, induced apoptosis of anaplastic thyroid cancer cells via the intrinsic apoptosis pathway and induced reactive oxygen species (ROS), which mediated DNA damage. In this study, we investigated the hypothesis that the mechanism of apoptosis induced by manumycin in anaplastic thyroid cancer cells fits the general pattern of the "xenobiotic apoptosis pathway," the hallmarks of which are induction of oxidative stress, mitogen-activated protein kinase (MAPK) signaling, and cytochrome c release, which activates the intrinsic apoptosis pathway. We found that manumycin reduced intracellular glutathione and generated ROS: nitric oxide and superoxide anions. Manumycin-induced apoptosis correlated with increase in ROS. Quenching of ROS with N-acetyl-L-cysteine prevented cytochrome c release by manumycin. Manumycin induced phosphorylation of p38 MAPK, which was blocked by N-acetyl-L-cysteine. p38 MAPK may be an important signaling mediator in the activation of the intrinsic apoptotic pathway by manumycin because the p38 MAPK inhibitor SB203580 inhibited cytochrome c release and activation of caspase-3 by manumycin. In conclusion, manumycin activated the intrinsic apoptosis pathway via activation of p38 MAPK by oxidative stress. The mechanism of apoptosis induced by manumycin fits the emerging general pattern for apoptosis induced by xenobiotics.     

A novel 7-bromoindirubin with potent anticancer activity suppresses survival of human melanoma cells associated with inhibition of STAT3 and Akt signaling

STAT3 and Akt signaling have been validated as potential molecular targets for treatment of cancers including melanoma. These small molecule inhibitors of STAT3 or Akt signaling are promising for developing anti-melanoma therapeutic agents. MLS-2438, a novel 7-bromoindirubin, a derivative of the natural product indirubin, was synthesized with a bromo-group at the 7-position on one indole ring and a hydrophilic group at the 3′-position on the other indole ring. We tested the anticancer activity of MLS-2438 and investigated its mechanism of action in human melanoma cell lines. Here, we show that MLS-2438 inhibits viability and induces apoptosis of human melanoma cells associated with inhibition of STAT3 and Akt signaling. Several pro-apoptotic Bcl-2 family proteins are involved in the MLS-2438 mediated apoptosis. MLS-2438 inhibits Src kinase activity in vitro and phosphorylation of JAK2, Src, STAT3 and Akt in cultured cancer cells. In contrast to the decreased phosphorylation levels of JAK2, Src, STAT3 and Akt, phosphorylation levels of the MAPK (Erk1/2) signaling protein were not reduced in cells treated with MLS-2438. These results demonstrate that MLS-2438, a novel natural product derivative, is a Src inhibitor and potentially regulates kinase activity of JAK2 and Akt in cancer cells. Importantly, MLS-2438 suppressed tumor growth with low toxicity in a mouse xenograft model of human melanoma. Our findings support further development of MLS-2438 as a potential small-molecule therapeutic agent that targets both STAT3 and Akt signaling in human melanoma cells.     

UBE2T基因通过调控ROS抑制结直肠癌细胞凋亡

目的:通过结肠癌细胞实验检测UBE2T对结肠癌细胞凋亡的影响。方法:细胞计数盒（CCK-8）法检测UBE2T基因转染对结肠癌细胞活力的影响；流式细胞仪检测UBE2T转染后对结肠癌细胞凋亡的影响；DCFDA染色流式细胞仪检测UBE2T转染对结肠癌细胞中ROS水平的影响；CCK-8法检测H2O2（增加ROS）对UBE2T基因转染降低结肠癌细胞活力的影响；流式细胞仪检测H2O2对UBE2T基因转染增加结肠癌细胞凋亡率的影响。结果:UBE2T转染能够明显增加结肠癌细胞活力（P＜0.05）；UBE2T基因转染抑制结肠癌细胞凋亡率（P＜0.05）；UBE2T转染减少结肠癌细胞ROS水平；预处理H2O2减弱UBE2T基因转染对结肠癌细胞活力的增加作用（P＜0.05）；预处理H2O2逆转UBE2T基因转染对结肠癌细胞凋亡率的抑制作用（P＜0.05）。结论:UBE2T基因转染能够抑制结肠癌凋亡，其机制是通过调节结直肠癌细胞中ROS水平。     

The JNK signaling pathway is involved in sodium-selenite-induced apoptosis mediated by reactive oxygen in HepG2 cells

Selenium compounds as effective chemopreventive agents can induce apoptosis in tumor cells, and reactive oxygen species (ROS) are important mediators in apoptosis induced by various stimuli including chemopreventive agents. The major mitogen-activated protein kinases (MAPKs), c-JUN N-terminal kinase (JNK), p38 and extracelluar signal-regulated kinase (ERK) are three kinases that have been shown to regulate apoptosis. In this study, we showed that selenite-induced apoptosis in HepG2 cells was mediated by ROS that activated JNK to regulate apoptosis. The selenite-treated HepG2 cells showed a dose- and time-dependent decrease in cell viability that was coincident with increased the levels of the apoptosis rate. The levels of selenite-induced ROS as measured by 2', 7'-dichlorofluorescein diacetate (DCFH-DA) fluorescence also showed a dose- and time-dependent increase in HepG2 cells. The kinase activity of JNK was induced by selenite in a dose-dependent manner and HepG2 cells exposed to selenite (10 microM) for 4 h showed increased levels of phosphorylated JNK, which decreased when exposed for additional 4 h. In contrast, Sp600125, a specific inhibitor of JNK, remarkably blocked the apoptosis of HepG2 exposed to selenite. Furthermore, N-acetylcysteine (NAC), a known antioxidant, increased cell viability and decreased ROS generation. Moreover, NAC effectively blocked apoptosis and decreased the levels of phosphorylated JNK induced by selenite. These results revealed that JNK might be involved in selenite-induced ROS-mediated apoptosis in HepG2 cells.     

6-Bromoindirubin-3'-oxime inhibits JAK/STAT3 signaling and induces apoptosis of human melanoma cells

STAT3 is persistently activated and contributes to malignant progression in various cancers. Janus activated kinases (JAK) phosphorylate STAT3 in response to stimulation by cytokines or growth factors. The STAT3 signaling pathway has been validated as a promising target for development of anticancer therapeutics. Small-molecule inhibitors of JAK/STAT3 signaling represent potential molecular-targeted cancer therapeutic agents. In this study, we investigated the role of JAK/STAT3 signaling in 6-bromoindirubin-3'-oxime (6BIO)-mediated growth inhibition of human melanoma cells and assessed 6BIO as a potential anticancer drug candidate. We found that 6BIO is a pan-JAK inhibitor that induces apoptosis of human melanoma cells. 6BIO directly inhibited JAK-family kinase activity, both in vitro and in cancer cells. Apoptosis of human melanoma cells induced by 6BIO was associated with reduced phosphorylation of JAKs and STAT3 in both dose- and time-dependent manners. Consistent with inhibition of STAT3 signaling, expression of the antiapoptotic protein Mcl-1 was downregulated. In contrast to the decreased levels of phosphorylation of JAKs and STAT3, phosphorylation levels of the Akt and mitogen-activated protein kinase (MAPK) signaling proteins were not inhibited in cells treated with 6BIO. Importantly, 6BIO suppressed tumor growth in vivo with low toxicity in a mouse xenograft model of melanoma. Taken together, these results show that 6BIO is a novel pan-JAK inhibitor that can selectively inhibit STAT3 signaling and induces tumor cell apoptosis. Our findings support further development of 6BIO as a potential anticancer therapeutic agent that targets JAK/STAT3 signaling in tumor cells.     

Cryptotanshinone activates p38/JNK and inhibits Erk1/2 leading to caspase-independent cell death in tumor cells

Cryptotanshinone (CPT), a natural compound isolated from the plant Salvia miltiorrhiza Bunge, is a potential anticancer agent. However, the underlying mechanism is not well understood. Here, we show that CPT induced caspase-independent cell death in human tumor cells (Rh30, DU145, and MCF-7). Besides downregulating antiapoptotic protein expression of survivin and Mcl-1, CPT increased phosphorylation of p38 mitogen-activated protein kinase (MAPK) and c-jun N-terminal kinase (JNK), and inhibited phosphorylation of extracellular signal-regulated kinases 1/2 (Erk1/2). Inhibition of p38 with SB202190 or JNK with SP600125 attenuated CPT-induced cell death. Similarly, silencing p38 or c-Jun also in part prevented CPT-induced cell death. In contrast, expression of constitutively active mitogen-activated protein kinase kinase 1 (MKK1) conferred resistance to CPT inhibition of Erk1/2 phosphorylation and induction of cell death. Furthermore, we found that all of these were attributed to CPT induction of reactive oxygen species (ROS). This is evidenced by the findings that CPT induced ROS in a concentration- and time-dependent manner; CPT induction of ROS was inhibited by N-acetyl-L-cysteine (NAC), a ROS scavenger; and NAC attenuated CPT activation of p38/JNK, inhibition of Erk1/2, and induction of cell death. The results suggested that CPT induction of ROS activates p38/JNK and inhibits Erk1/2, leading to caspase-independent cell death in tumor cells.     

Butein suppresses breast cancer growth by reducing a production of intracellular reactive oxygen species

Background

Butein has various functions in human diseases including cancer. While anti-cancer effects of butein have been revealed, it is urgent to understand a unique role of butein against cancer. In this study, we demonstrate that butein inhibition of reactive oxygen species (ROS) production results in suppression of breast cancer growth.

Methods

Different breast cancer cell lines were treated with butein and then subjected to cell viability and apoptosis assays. Butein-sensitive or -resistant breast cancer cells were injected into mammary fat pads of immunocompromised mice and then butein was injected. Breast cancer cells were categorized on the basis of butein sensitivity.

Results

Butein reduced viabilities of different breast cancer cells, while not affecting those of HER2-positive (HER2⁺) HCC-1419, SKBR-3 and HCC-2218 breast cancer cells. Butein reduction of ROS levels was correlated with apoptotic cell death. Furthermore, butein reduction of ROS level led to inhibitions of AKT phosphorylation. N-acetyl-L-cysteine (NAC), a free radical scavenger, also reduced ROS production and AKT phosphorylation, resulting in apoptotic cell death. In contrast, inhibitory effects of both butein and NAC on ROS production and AKT phosphorylation were not detected in butein-resistant HER2⁺ HCC-1419, SKBR-3 and HCC-2218 cells. In the in vivo tumor growth assays, butein inhibited tumor growth of butein-sensitive HER2⁺ BT-474 cells, while not affecting that of butein-resistant HER2⁺ HCC-1419 cells. Moreover, butein inhibition of ROS production and AKT phosphorylation was confirmed by in vivo tumor growth assays.

Conclusions

Our study first reveals that butein causes breast cancer cell death by the reduction of ROS production. Therefore, our finding provides better knowledge for butein effect on breast cancer and also suggests its treatment option.     

Hypoxia increases resistance of human pancreatic cancer cells to apoptosis induced by gemcitabine.

PURPOSE: Hypoxia, frequently found in the center of solid tumor, is associated with resistance to chemotherapy by activation of signaling pathways that regulate cell pro-liferation, angiogenesis, and apoptosis. We determined whether hypoxia can increase the resistance of human pancreatic carcinoma cells to gemcitabine-induced apoptosis by activation of phosphatidylinositol 3'-kinase (PI3K)/Akt, MEK/mitogen-activated protein kinase (extracellular signal-regulated kinase) [MAPK(Erk) kinase (MEK)], and nuclear factor kappa B (NF-kappa B) signaling pathways. EXPERIMENTAL DESIGN: We evaluated the phosphorylation of Akt and MAPK(Erk), DNA binding activity of NF-kappa B, and apoptosis induced by gemcitabine in L3.6pl human pancreatic cancer cells under normoxic and hypoxic conditions. We then examined the effects of the PI3K inhibitor LY294002, MEK inhibitor U0126, and the epidermal growth factor receptor tyrosine kinase inhibitor PKI 166 on these signaling pathways and induction of apoptosis. RESULTS: Hypoxic conditions increased phosphorylation of Akt and MAPK(Erk) and NF-kappa B DNA binding activity in L3.6pl cells. The activation of Akt and NF-kappa B was prevented by LY294002, whereas the activity of MAPK(Erk), but not NF-kappa B, was inhibited by U0126. The increased activation of Akt, NF-kappa B, and MAPK(Erk) was inhibited by PKI 166. Under hypoxic conditions, L3.6pl cells were resistant to apoptosis induced by gemcitabine. The addition of LY294002 or PKI 166 abrogated cell resistance to gemcitabine, whereas U0126 only partially decreased this resistance. CONCLUSIONS: These data demonstrate that hypoxia can induce resistance of pancreatic cancer cells to gemcitabine mainly through the PI3K/Akt/NF-kappa B pathways and partially through the MAPK(Erk) signaling pathway. Because PKI 166 prevented the activation of PI3K/Akt/NF-kappa B and MAPK(Erk) pathways, the combination of this tyrosine kinase inhibitor with gemcitabine should be an effective therapy for pancreatic cancer.     

Antitumoral activity of new polyamine-naphthoquinone conjugates

Polyamine-naphthoquinone conjugates 5a-c were synthesized by nucleophilic displacement of 2-methoxy-lawsone 3a, 2-methoxylapachol 3b and 2-methoxy-nor-lapachol 3c with the polyamine N1-Boc-N5-Bn-spermidine 4. Unprotected derivatives 6a-c were synthesized to evaluate the effect of the protective Boc group on the activity of compounds 5a-c. The colorimetric MTT assay was used to evaluate their cytotoxic activity. All compounds were active against human lines of promyelocytic leukemia (HL-60), lung cancer (GLC4), Burkitt lymphoma (Daudi) and a mouse breast tumor (Ehrlich carcinoma), but only unprotected 6a-c showed activity against the human line of melanoma (MV-3). IC50 values were obtained from dose response curves by linear regression. DNA fragmentation was measured by quantification of the subG1 peak of the cell cycle. Apoptosis of HL-60 treated with 5c was dose-dependent. The amount of DNA fragmentation observed by exposure of HL-60 to 25 microM of compounds 5a-c and 6a-c is compatible with the decrease in viability induced by the drugs at this concentration. Production of ROS was measured by H2-CFDA. Kinetics of HL-60 DNA fragmentation and ROS formation by 5c indicated that production of ROS precedes cell death. In conclusion, spermidine-1,4-naphthoquinone conjugates exhibited an increase in activity compared with the natural products and induced apoptosis of tumor cell lines by a mechanism that is mediated, at least in part, by ROS production.     

Combined effect of ALK and MEK inhibitors in EML4-ALK-positive non-small-cell lung cancer cells

Background:

Although most non-small-cell lung cancer (NSCLC) patients with the echinoderm microtubule-associated protein-like 4 (EML4) – anaplastic lymphoma kinase (ALK) fusion gene – benefit from ALK tyrosine kinase inhibitors (ALK-TKIs), the efficacy of these drugs varies greatly among individuals.

Methods:

The antitumour action of ALK-TKIs in EML4–ALK-positive NSCLC cell lines was evaluated from their effects on cell proliferation, signal transduction, and apoptosis.

Results:

The ALK-TKI TAE684 inhibited cell proliferation and induced apoptosis, in association with inhibition of STAT3 and ERK phosphorylation, in EML4–ALK-positive H3122 cells. TAE684 inhibited STAT3 phosphorylation, but not ERK phosphorylation, and it showed little effect on cell proliferation or apoptosis, in EML4–ALK-positive H2228 cells. The combination of TAE684 and a MEK inhibitor-induced marked apoptosis accompanied by inhibition of STAT3 and ERK pathways in H2228 cells. Such dual interruption of STAT3 and ERK pathways induced downregulation of the antiapoptotic protein survivin and upregulation of the proapoptotic protein BIM.

Conclusion:

Our results indicate that interruption of both STAT3-survivin and ERK–BIM pathways is required for induction of apoptosis in NSCLC harbouring EML4–ALK, providing a rationale for combination therapy with ALK and MEK inhibitors in EML4–ALK-positive NSCLC patients for whom ALK inhibitors alone are ineffective.     

A novel PP2A enhancer induces caspase-independent apoptosis of MKN28 gastric cancer cells with high MEK activity

The newly synthesized phosphatidylinositol (PI) derivative 1,2-O-bis-[8-{2-(2-pentyl-cyclopropylmethyl)-cyclopropyl}-octanoyl]-sn-glycero-3-phosphatidyl-D-1-inositol (diDCP-LA-PI) significantly enhanced protein phosphatase 2A (PP2A) activity in the cell-free assay. This prompted to assess the antitumor effect of diDCP-LA-PI. diDCP-LA-PI attenuated phosphorylation of mitogen-activated protein kinase (MAPK) kinase (MEK) in Lu65 human lung cancer and MKN28 human gastric cancer cells with high MEK activity. diDCP-LA-PI reduced cell viability in Lu65 and MKN28 cells, but otherwise such effect was not found in 786-O human renal cancer and HUH-7 human hepatoma cells with relatively low MEK activity. For Lu65 and MKN28 cells diDCP-LA-PI increased terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells, but no significant activation of caspase-3, -8, or -9 was obtained. For MKN28 cells diDCP-LA-PI-induced reduction of MEK phosphorylation and cell viability was prevented by knocking-down PP2Ac. Taken together, these results indicate that diDCP-LA-PI induces caspase-independent apoptosis of Lu65 and MKN28 human cancer cells, for the latter cells by suppressing MEK activity through PP2A-catalyzed dephosphorylation.     

Multiple signal pathways are involved in the mitogenic effect of 5(S)-HETE in human pancreatic cancer

Pancreatic carcinoma is characterized by poor prognosis and lack of response to conventional therapy. The reasons for this are not fully understood. We have reported that inhibition of 5-lipoxygenase abolished proliferation and induced apoptosis in pancreatic cancer cells while the 5-lipoxygenase metabolite, 5(S)-hydroxyeicosatetraenoic acid [5(S)-HETE] stimulated pancreatic cancer cell proliferation. The current study was designed to investigate the underlying mechanisms for 5(S)-HETE-stimulated proliferation of pancreatic cells. Two human pancreatic cancer cell lines, PANC-1 and HPAF, were used. Cell proliferation was monitored by thymidine incorporation and cell counting. Phosphorylation of P42/44(MAPK) (mitogen activated protein kinase, ERK), MEK (MAPK/ERK kinase), P38 kinase, JNK/SAPK (c-Jun N-terminal kinase/ stress-activated protein kinase), AKT and tyrosine residues of intracellular proteins was measured by Western blot using their corresponding phospho-specific antibodies. The results showed that (1) 5(S)-HETE markedly stimulated pancreatic cancer cell proliferation in a time- and concentration-dependent manner; (2) 5(S)-HETE induced tyrosine phosphorylation of multiple intracellular proteins while the tyrosine kinase inhibitor, genestein, blocked 5(S)-HETE-stimulated cell proliferation; (3) 5(S)-HETE significantly stimulated both MEK and P42/44(MAPK) phosphorylation and the MEK inhibitors, PD098059 and U0126, inhibited 5(S)-HETE-stimulated proliferation in these two cell lines; (4) 5(S)-HETE also stimulated P38 kinase phosphorylation but the P38 inhibitor, SB203580, did not effect 5(S)-HETE-stimulated cell proliferation; (5) 5(S)-HETE markedly stimulated AKT phosphorylation while the phosphatidylinositide-3 (PI3)-kinase inhibitor, wortmannin, blocked 5(S)-HETE-stimulated cell proliferation; (6) phosphorylation of JNK/SAPK was not induced by 5(S)-HETE, and (7) the general protein kinase C (PKC) inhibitor, GF109203X, did not affect 5(S)-HETE-stimulated cancer cell proliferation. These findings suggest that intracellular tyrosine kinases, MEK/ERK and PI3 kinase/AKT pathways are involved in 5(S)-HETE-stimulated pancreatic cancer cell proliferation but P38 kinase, JNK/SAPK and PKC are not involved in this mitogenic effect.