Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Oxaliplatin, a chemotherapeutic drug, induces DNA strand breaks leading to apoptosis in colorectal cancer cells. gamma-H2AX is a phosphorylated histone H2AX that can act as a marker of DNA double-strand breaks (DSBs). It has been shown that securin proteins were over-expressed in a variety of cancer cells. However, the roles of gamma-H2AX and securin on the oxaliplatin-induced apoptosis in human colorectal cancer cells remain unclear. Treatment of oxaliplatin (1-10 microM for 6-24h) persistently induced gamma-H2AX formation and inhibited securin protein expression via a time- and concentration-dependent manner in HCT116 securin-wild type colorectal cancer cells. Compared with HCT116 securin-wild type cells, the induction of apoptosis and persistent gamma-H2AX formation by oxaliplatin was reduced in the HCT116 securin-null colorectal cancer cells. Furthermore, the blockage of caspases by specific caspase inhibitors reduced the levels of gamma-H2AX proteins and cytotoxicity but increased securin protein expression in the oxaliplatin-exposed cells. The gene knockdown of H2AX by transfection with a short interfering RNA of H2AX enhanced the oxaliplatin-induced cell death. Interestingly, the phosphorylation of p38 mitogen-activated protein kinase (MAPK) was markedly increased by oxaliplatin. Pre-treatment of a specific p38 MAPK inhibitor SB202190 reduced gamma-H2AX proteins and increased securin protein expression in the oxaliplatin-treated cells. Our findings suggest that p38 MAPK may oppositely regulate securin protein expression and gamma-H2AX formation in the oxaliplatin-induced apoptosis of human colorectal cancer cells.
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PMID:Regulation of gamma-H2AX and securin contribute to apoptosis by oxaliplatin via a p38 mitogen-activated protein kinase-dependent pathway in human colorectal cancer cells. 1866 57

Histone H2A variant H2AX is a dose-dependent suppressor of oncogenic chromosome translocations. H2AX participates in DNA double-strand break repair, but its role in other DNA repair pathways is not known. In this study, role of H2AX in cellular response to alkylation DNA damage was investigated. Cellular sensitivity to two monofunctional alkylating agents (methyl methane sulfonate and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)) was dependent on H2AX dosage, and H2AX null cells were more sensitive than heterozygous cells. In contrast to wild-type cells, H2AX-deficient cells displayed extensive apoptotic death due to a lack of cell-cycle arrest at G(2)/M phase. Lack of G(2)/M checkpoint in H2AX null cells correlated well with increased mitotic irregularities involving anaphase bridges and gross chromosomal instability. Observation of elevated poly(ADP) ribose polymerase 1 (PARP-1) cleavage suggests that MNNG-induced apoptosis occurs by PARP-1-dependent manner in H2AX-deficient cells. Consistent with this, increased activities of PARP and poly(ADP) ribose (PAR) polymer synthesis were detected in both H2AX heterozygous and null cells. Further, we demonstrate that the increased PAR synthesis and apoptotic death induced by MNNG in H2AX-deficient cells are due to impaired activation of mitogen-activated protein kinase pathway. Collectively, our novel study demonstrates that H2AX, similar to PARP-1, confers cellular protection against alkylation-induced DNA damage. Therefore, targeting either PARP-1 or histone H2AX may provide an effective way of maximizing the chemotherapeutic value of alkylating agents for cancer treatment.
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PMID:Histone H2AX is a critical factor for cellular protection against DNA alkylating agents. 1854 54

Phosphorylation of H2AX is believed to be associated with the repair of damaged DNA. Recent findings suggest a novel function of H2AX in cellular apoptosis. Specifically, it was shown that ultraviolet A-activated JNK phosphorylates H2AX to regulate apoptosis. Here we show that serum starvation induces H2AX phosphorylation and apoptosis independent of the JNK pathway. Serum starvation induced p38 phosphorylation, whereas it did not affect the phosphorylation of ERK or JNK. Inhibition of p38 reduced H2AX phosphorylation and apoptosis. Furthermore, p38 was found to phosphorylate H2AX directly in vitro and was colocalized with H2AX in vivo. Finally, we demonstrate that H2AX phosphorylation is required for serum starvation-induced apoptosis. Taken together, these data elucidate a novel signaling pathway (p38/H2AX) to regulate apoptosis.
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PMID:Serum starvation induces H2AX phosphorylation to regulate apoptosis via p38 MAPK pathway. 1861 40

Arsenic trioxide (As2O3) has been introduced to the treatment of acute promyelocytic leukemia (APL), and has also been shown to induce apoptosis in a variety of solid tumor cell lines, including non-small cell lung cancer. However, the prohibitively high concentration required for the induction of apoptotic cell death in many solid tumor cells is unacceptable for clinical utilization due to the excessive toxicity associated with this dose. Sulindac is known to enhance the cellular responsiveness of tumors toward chemotherapeutic drugs. Herein, we demonstrated that combination treatment with As2O3 and sulindac resulted in a synergistic augmentation of cytotoxicity in H157 lung cancer cells, which was revealed by apoptotic induction as demonstrated by an increase in the sub-G0/G1 fraction. In addition, combination treatment with As2O3 and sulindac increased reactive oxygen species (ROS) and oxidative stress, as evidenced by the heme oxygenase-1 (HO-1) expression and mitogen-activated protein kinase (MAPK) phosphorylation. MAPK inhibitors blocked the induction of HO-1 by combination treatment. Inhibitors of p38 and JNK partially inhibited the augmented cell death whereas the ERK inhibitor showed poor inhibition. Combination treatment with As2O3 and sulindac induced oxidative DNA damage in a time-dependent fashion, which was evaluated by H2AX phosphorylation along with HO-1 induction.
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PMID:Combination treatment with arsenic trioxide and sulindac enhances apoptotic cell death in lung cancer cells via activation of oxidative stress and mitogen-activated protein kinases. 1863 1

As demonstrated recently, ionizing radiation (IR) can mediate phosphorylation of DNA-PKcs in human tumor cells through stimulation of the PI3K/Akt pathway. It is also known that DNA-PKcs directly interacts the X-ray repair cross-complementing group 1 protein (XRCC1) involved in base excision repair (BER). Therefore, in the present study we investigated the role of PI3K/Akt activity and DNA-PKcs on XRCC1 expression/stabilization. In contrast to the DNA-PKcs-deficient glioblastoma cell line MO59J, the DNA-PKcs-proficient counterpart MO59K as well as human lung adenocarcinoma A549 cells presented a high basal level of XRCC1 expression. Radiation doses of 3-12Gy did not stimulate a further enhanced expression of XRCC1 in DNA-PKcs-proficient cells (MO59K and A549) within 180min post-irradiation. However, a marked induction of XRCC1 expression was apparent in DNA-PKcs-deficient MO59J cells. Targeting of DNA-PKcs as well as PI3K/Akt pathway by specific kinase inhibitors and/or siRNA reduced basal XRCC1 expression in un-irradiated DNA-PKcs-proficient cells to the level observed in DNA-PKcs-deficient cells. Reduction of basal expression of XRCC1 by XRCC1-siRNA, AKT-siRNA as well as DNA-PKcs inhibitor facilitated IR-induced XRCC1 expression. XRCC1 expression induced by irradiation, however, was independent of PI3K/Akt signaling, but dependent of MAPK-ERK1/2. By immuno-precipitation experiments and confocal microscopy a complex formation of XRCC1 and DNA-PKcs was shown. Applying gamma-H2AX foci analysis it was shown that basal expression of XRCC1 is important for the repair of IR-induced DNA-double strand breaks (DNA-DSBs). These data indicate that IR-induced XRCC1 expression is dependent on the expression level of DNA-PKcs and basal activity status of PI3K/Akt signaling. Likewise, potential of IR-induced XRCC1 expression depends on its basal expression level.
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PMID:PI3K-Akt signaling regulates basal, but MAP-kinase signaling regulates radiation-induced XRCC1 expression in human tumor cells in vitro. 1867 86

Esophageal squamous cell carcinoma (ESCC) is an exceptionally drug-resistant tumor with a 5-year survival rate <5%. From an initial drug screen, we identified bortezomib as having robust activity in ESCC lines. Mechanistically, bortezomib induced a G2-M-phase cell cycle arrest and p53-independent apoptosis associated with caspase cleavage and Noxa induction. Bortezomib also showed excellent activity in organotypic culture and in vivo models of ESCC. Biochemically, bortezomib treatment activated the p38 and c-Jun NH2-termnial kinase stress-activated mitogen-activated protein kinase (MAPK) pathways and induced phospho-H2AX activity. Although H2AX is known to cooperate with c-Jun NH2-termnial kinase to induce apoptosis following UV irradiation, knockdown of H2AX did not abrogate bortezomib-induced apoptosis. Instead, blockade of p38 MAPK signaling, using either small interfering RNA or a pharmacologic inhibitor, reversed bortezomib-induced apoptosis and the up-regulation of Noxa. Radiation therapy is known to activate the p38 MAPK pathway and is a mainstay of ESCC treatment strategies. In a final series of studies, we showed that the coadministration of bortezomib with irradiation led to enhanced p38 MAPK activity and a significant reduction in colony formation. We therefore suggest that p38 MAPK pathway activation is an excellent potential therapeutic strategy in ESCC. It is further suggested that bortezomib could be added to existing ESCC therapeutic regimens.
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PMID:Bortezomib induces apoptosis in esophageal squamous cell carcinoma cells through activation of the p38 mitogen-activated protein kinase pathway. 1879 Jul 67

Autophagy is a self-eating process to eradicate damaged proteins or organelles in cells. This process begins with formation of a double-membrane structure, called an autophagosome, which can sequester soluble proteins and organelles eventually degraded by lysosomal proteases after fusion with the lysosome. Autophagy was initially identified as a cell survival mechanism under stress conditions such as nutrient deprivation. More recently, it is also considered as type-II programmed cell death. In our recent report, we observed that overexpression of TrkA caused massive cell death via both apoptosis and autophagy. Overexpression of TrkA abated catalase activity and subsequently resulted in the production of a large amount of reactive oxygen species in cells. These consequences led to autophagic cell death. The autophagic cell death in TrkA-overexpressing cells was validated by GFP-LC3 dot formation, production of autophagosomes or acidic vacuoles, LC3 lipidation, and depletion of autopahgy-related genes. In addition, we also observed some evidence for apoptosis in TrkA-expressing cells. Many cells expressing TrkA exhibited annexin V-positive staining, activation of caspase-7 and BAX. Moreover, TrkA activated the JNK pathway, leading to phosphorylation of H2AX. In this report, we suggest that two cell death mechanisms occur simultaneously and interlink with each other. The JNK-calpain pathway might be a central process to mediate the two processes in TrkA-overexpressing cells, although further study still remains to prove the interplay between autophagy and apoptosis.
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PMID:Interplay between autophagy and apoptosis in TrkA-induced cell death. 1911 84

We recently identified a novel human AlkB homologue, ALKBH8, which is expressed in various types of human cancers including human urothelial carcinomas. In examining the role and function of ALKBH8 in human bladder cancer development in vitro, we found that silencing of ALKBH8 through small interfering RNA transfection reduced reactive oxygen species (ROS) production via down-regulation of NAD(P)H oxidase-1 (NOX-1) and induced apoptosis through subsequent activation of c-jun NH(2)-terminal kinase (JNK) and p38. However, we also found that JNK and p38 activation resulted in phosphorylation of H2AX (gammaH2AX), a variant of mammalian histone H2A, which contributes to the apoptosis induced by silencing ALKBH8 and NOX-1. Silencing of ALKBH8 significantly suppressed invasion, angiogenesis, and growth of bladder cancers in vivo as assessed both in the chorioallantoic membrane assay and in an orthotopic mouse model using green fluorescent protein-labeled KU7 human urothelial carcinoma cells. Immunohistochemical examination showed high expression of ALKBH8 and NOX-1 proteins in high-grade, superficially and deeply invasive carcinomas (pT(1) and >pT(2)) as well as in carcinoma in situ, but not in low-grade and noninvasive phenotypes (pT(a)). These findings indicate an essential role for ALKBH8 in urothelial carcinoma cell survival mediated by NOX-1-dependent ROS signals, further suggesting new therapeutic strategies in human bladder cancer by inducing JNK/p38/gammaH2AX-mediated cell death by silencing of ALKBH8.
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PMID:A novel human AlkB homologue, ALKBH8, contributes to human bladder cancer progression. 1929 82

Resistance to chemotherapy is a major obstacle for successful treatment of breast cancer patients. Given that prolactin (PRL) acts as an anti-apoptotic/survival factor in the breast, we postulated that it antagonizes cytotoxicity by chemotherapeutic drugs. Treatment of breast cancer cells with PRL caused variable resistance to taxol, vinblastine, doxorubicin and cisplatin. PRL prevented cisplatin-induced G(2)/M cell cycle arrest and apoptosis. In the presence of PRL, significantly less cisplatin was bound to DNA, as determined by mass spectroscopy, and little DNA damage was seen by gamma-H2AX staining. PRL dramatically increased the activity of glutathione-S-transferase (GST), which sequesters cisplatin in the cytoplasm; this increase was abrogated by Jak and mitogen-activated protein kinase inhibitors. PRL upregulated the expression of the GSTmu, but not the pi, isozyme. A GST inhibitor abrogated antagonism of cisplatin cytotoxicity by PRL. In conclusion, PRL confers resistance against cisplatin by activating a detoxification enzyme, thereby reducing drug entry into the nucleus. These data provide a rational explanation for the ineffectiveness of cisplatin in breast cancer, which is characterized by high expression of both PRL and its receptor. Suppression of PRL production or blockade of its actions should benefit patients undergoing chemotherapy by allowing for lower drug doses and expanded drug options.
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PMID:Prolactin confers resistance against cisplatin in breast cancer cells by activating glutathione-S-transferase. 1944 5

Activation of the nuclear transcription factor-kappaB (NF-kappaB) has been implicated in liver tumorigenesis. We evaluated the effects of a novel NF-kappaB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), in two human liver cancer cell lines HA22T/VGH and HuH-6. DHMEQ treatment dose dependently decreased the DNA-binding capacity of the NF-kappaB p65 subunit, inhibited cell growth and proliferation, and increased apoptosis as shown by caspase activation, release of cytochrome c, poly(ADP-ribose) polymerase cleavage, and down-regulation of survivin. DHMEQ also induced a dose-dependent activation of mitogen-activated protein kinase kinase/extracellular signal-regulated kinase signaling, and inhibition of this pathway significantly reduced cell growth. It is noteworthy that we observed that DHMEQ stimulated reactive oxygen species (ROS) production in a dose-dependent manner and that pretreatment of the cells with the antioxidant N-acetyl-L-cysteine (NAC) significantly reduced DHMEQ-induced ROS generation. Accordingly, NAC completely reversed the DHMEQ-induced growth inhibition, caspase activation, and cell death. DHMEQ-treated cells exhibited DNA damage, as evaluated by accumulation in nuclear foci of phospho-H2AX, which was completely reversed by NAC. Moreover, DHMEQ induced the expression of genes involved in the endoplasmic reticulum stress response (GRP78, CHOP, TRB3) and promoted the splicing of XBP1 mRNA in a dose-dependent fashion in both cell lines, which was reversed in the presence of NAC. Knockdown of TRB3 mRNA expression by small interference RNA significantly decreased DHMEQ-induced cell growth inhibition. These data suggest that DHMEQ antitumor effects are primarily mediated through ROS generation. Thereby, considering that cancer cells are under increased ER stress and oxidative stress conditions, DHMEQ may greatly improve various anticancer strategies.
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PMID:Antitumor effects of dehydroxymethylepoxyquinomicin, a novel nuclear factor-kappaB inhibitor, in human liver cancer cells are mediated through a reactive oxygen species-dependent mechanism. 1946 Oct 54


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