Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

AMPK is a serine/threonine protein kinase family and we recently identified a novel member, ARK5. The activation of ARK5 is triggered by Akt, and ARK5 induces tumor cell survival during nutrient starvation. In the current study, we investigated the mechanisms of induction of cell survival by ARK5. Human hepatoma HepG2 cells undergo necrotic cell death within 24 h after the start of glucose starvation, and the cell death signaling has been found to be mediated by death-receptor-independent activation of caspase 8. When HepG2 cells were transfected with ARK5 expression vector and subjected to several cell death stimuli, ARK5 was found to suppress cell death by glucose starvation, TRAIL, and TNF-alpha, but not by ultraviolet irradiation, camptothecin, or doxorubicin. Western blotting analysis revealed that both TRAIL and glucose starvation induced Bid cleavage and FLIP degradation following caspase 8 activation in a time-dependent manner, and ARK5 overexpression clearly delayed Bid cleavage, FLIP degradation, and caspase 8 activation. On the basis of the results of this study, we report that cell survival induced by ARK5 is, at least in part, due to inhibition of caspase 8 activation.
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PMID:ARK5 suppresses the cell death induced by nutrient starvation and death receptors via inhibition of caspase 8 activation, but not by chemotherapeutic agents or UV irradiation. 1367 56

The role of c-Kit in the development of melanoma was studied in line 304/B6 of RET-transgenic mice, in which melanoma spontaneously develops. In Wv/Wv-RET (304/B6)-transgenic mice, in which c-Kit function was severely impaired, development of melanoma was strongly suppressed. Although 31 of the 44 original RET-transgenic mice died of rapidly growing melanoma within 12 months after birth, only 8 of the 44 Wv/Wv-RET-transgenic mice developed slowly growing melanocytic tumors with a greatly prolonged mean tumor-free period, 2 of which died of melanoma at a late stage. Even Wv/+-RET-transgenic mice had a clearly prolonged tumor-free period and definitely reduced frequency (6 of 61) of tumor death within 12 months after birth. Melanin production in the skin of these mice was not strongly impaired, suggesting that c-Kit affects the development of melanomas in these mice with only minor effects in melanin production. c-Kit expression in skin soon after birth was promoted in RET-transgenic mice, and c-Kit was expressed at high levels at the benign but not malignant stage of the tumor. A single injection of anti-c-Kit antibody (ACK2) into RET-transgenic mice soon after birth caused a surprisingly long-lasting suppression of development of melanoma, greatly prolonging the tumor-free period, and none of the 28 ACK2-treated RET-transgenic mice died from tumors at 12 months of age. The c-Kit function needed for melanin production was also suppressed for an unusually long time in ACK2-treated, RET-transgenic mice. These results suggest that c-Kit can be a unique target molecule for melanoma treatment.
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PMID:c-Kit-targeting immunotherapy for hereditary melanoma in a mouse model. 1487 2

We investigated regulation of various signal transduction pathways during oxidative stresses in the kidney of young and aged rats. Menadione-induced regulation of molecules in PI 3-kinase, MAPK, and AMPK pathways was determined in the young (2 months) and old (24 months) groups. PI 3-kinase activity and Akt phosphorylation were significantly reduced in the old compared with the young. PTEN tumor suppressor was also lower in its expression and phosphorylation levels in the old. Response of the molecules in PI 3-kinase pathway to menadione was minimized. In contrast, over 5-fold induction of ERK1/2 phosphorylation by menadione was observed in both groups. On the other hand, basal activities as well as menadione-induced activities of JNK1 and AMPK were higher in the old than in the young. While p27(Kip1), p53, and p21(Waf1) were slightly increased by menadione in both groups, the basal induction level in the old was considerably higher. In conclusion, the results suggest that the age-related down-regulation of PI 3-kinase/Akt pathway and up-regulation of JNK1, AMPK, and p53 pathways may be responsible for the increased susceptibility to oxidative stress.
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PMID:Differential regulation of phosphatidylinositol 3-kinase/Akt, mitogen-activated protein kinase, and AMP-activated protein kinase pathways during menadione-induced oxidative stress in the kidney of young and old rats. 1497 36

A novel member of the human AMPK family, ARK5, was recently discovered to be a key molecule in mediating cancer cell migration activity in human pancreas cancer cell line PANC-1, and its activation was found to be induced by Akt-dependent phosphorylation at Ser 600. DNA array analysis with 241 paired cDNAs from 13 different types of tumors and corresponding normal tissues derived from cancer patients revealed ARK5 overexpression in the samples of colorectal cancer. ARK5 expression was measured and an in vitro invasion assay was performed in six human colorectal cancer cell lines, WiDr, HCT-15, DLD-1, SW620, LoVo, and SW480, and since high invasion activity was concordant with higher ARK5 expression, ARK5 expression was examined in relation to tumor progression and metastatic activity in clinical samples. In 56 clinical samples of primary colorectal cancers and their liver metastases, higher ARK5 expression was observed in the samples from more advanced cases, and much higher expression was observed in the liver metastases. In situ hybridization analysis showed ARK5 overexpression in tumor cells. Based on these findings, we propose that ARK5 overexpression is involved in tumor progression of colon cancer clinically.
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PMID:ARK5 expression in colorectal cancer and its implications for tumor progression. 1498 52

The LKB1 tumor suppressor protein controls the activity of the TSC1/TSC2 tumor suppressor complex. Mutations in LKB1 cause Peutz-Jeghers syndrome (PJS), and mutations in either TSC1 or TSC2 cause tuberous sclerosis complex--two syndromes characterized by the development of hamartomas. LKB1 activation by energy deprivation activates AMPK, which in turn phosphorylates and activates TSC2. TSC2 activation results in the inactivation of mTOR, a critical regulator of protein translation. How mTOR dysregulation after inactivation of LKB1 or TSC1/2 contributes to hamartoma development is not known. However, hypoxia-inducible factor (HIF) and VEGF are regulated by mTOR and are likely to play a contributory role.
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PMID:Dysregulation of HIF and VEGF is a unifying feature of the familial hamartoma syndromes. 1526 Nov 37

The study of hereditary tumor syndromes has laid a solid foundation toward understanding the genetic basis of cancer. One of the latest examples comes from the study of tuberous sclerosis complex (TSC). As a member of the phakomatoses, TSC is characterized by the appearance of benign tumors, most notably in the central nervous system, kidney, heart, lung, and skin. While classically described as "hamartomas," the pathology of the lesions has features suggestive of abnormal cellular proliferation, size, differentiation, and migration. Occasionally, tumors progress to become malignant (i.e., renal cell carcinoma). The genetic basis of this disease has been attributed to mutations in one of two unlinked genes, TSC1 and TSC2. Cells undergo bi-allelic inactivation of either gene to give rise to tumors in a classic tumor suppressor "two-hit" paradigm. The functions of the TSC1 and TSC2 gene products, hamartin and tuberin, respectively, have remained ill defined until recently. Genetic, biochemical, and biologic analyses have highlighted their role as negative regulators of the mTOR signaling pathway. Tuberin, serving as a substrate of AKT and AMPK, mediates mTOR activity by coordinating inputs from growth factors and energy availability in the control of cell growth, proliferation, and survival. Emerging evidence also suggests that the TSC 1/2 complex may play a role in modulating the activity of beta-catenin and TGFbeta. These findings provide novel functional links between the TSC genes and other tumor suppressors responsible for Cowden's disease (PTEN), Peutz-Jeghers syndrome (LKB1), and familial polyposis (APC). Common sporadic cancers such as prostate, lung, colon, endometrium, and breast have ties to these genes, highlighting the potential role of the TSC proteins in human cancers. Rapamycin, a specific mTOR inhibitor, has potent antitumoral activities in preclinical models of TSC and is currently undergoing phase I/II clinical studies.
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PMID:The tuberous sclerosis complex genes in tumor development. 1556 17

5-Fluorouracil (5-FU) is one of the widely used chemotherapeutic drugs targeting various cancers, but its chemo-resistance remains as a major obstacle in clinical settings. In the present study, HT-29 colon cancer cells were markedly sensitized to apoptosis by both 5-FU and genistein compared to the 5-FU treatment alone. There is an emerging evidence that genistein, soy-derived phytoestrogen, may have potential as a chemotherapeutic agent capable of inducing apoptosis or suppressing tumor promoting proteins such as cyclooxygenase-2 (COX-2). However, the precise mechanism of cellular cytotoxicity of genistein is not known. The present study focused on the correlation of AMPK and COX-2 in combined cytotoxicity of 5-FU and genistein, since AMPK is known as a primary cellular homeostasis regulator and a possible target molecule of cancer treatment, and COX-2 as cell proliferation and anti-apoptotic molecule. Our results demonstrated that the combination of 5-FU and genistein abolished the up-regulated state of COX-2 and prostaglandin secretion caused by 5-FU treatment in HT-29 colon cancer cells. These appear to be followed by the specific activation of AMPK and the up-regulation of p53, p21, and Bax by genistein. Under same conditions, the induction of Glut-1 by 5-FU was diminished by the combination treatment with 5-FU and genistein. Furthermore, the reactive oxygen species (ROS) was found as an upstream signal for AMPK activation by genistein. These results suggested that the combination of 5-FU and genistein exert a novel chemotherapeutic effect in colon cancers, and AMPK may be a novel regulatory molecule of COX-2 expression, further implying its involvement in cytotoxicity caused by genistein.
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PMID:Combination of 5-fluorouracil and genistein induces apoptosis synergistically in chemo-resistant cancer cells through the modulation of AMPK and COX-2 signaling pathways. 1589 11

Because survival and growth of human hepatoma cells are maintained by nutrient, especially glucose, glucose starvation induces acute cell death. The cell death is markedly suppressed by hypoxia, and we have reported involvement of AMP-activated protein kinase-alpha (AMPK-alpha), Akt, and ARK5 in hypoxia-induced tolerance. In the current study we investigated the mechanism of hypoxia-induced tolerance in human hepatoma cell line HepG2. ARK5 expression was induced in HepG2 cells when they were subjected to glucose starvation, and we found that glucose starvation transiently induced Akt and AMPK-alpha phosphorylation and that hypoxia prolonged phosphorylation of both protein kinases. We also found that hypoxia-induced tolerance was partially abrogated by blocking the Akt/ARK5 system or by suppressing AMPK-alpha expression and that suppression of both completely abolished the tolerance, suggesting that AMPK-alpha activation signaling and the Akt/ARK5 system play independent essential roles in hypoxia-induced tolerance. By using chemical compounds that specifically inhibit kinase activity of type I-transforming growth factor-beta (TGF-beta) receptor, we showed an involvement of TGF-beta in hypoxia-induced tolerance. TGF-beta1 mRNA expression was induced by hypoxia in an hypoxia-inducible factor-1alpha-independent manner, and addition of recombinant TGF-beta suppressed cell death during glucose starvation even under normoxic condition. AMPK-alpha, Akt, and ARK5 were activated by TGF-beta1, and Akt and AMPK-alpha phosphorylation, which was prolonged by hypoxia, was suppressed by an inhibitor of type I TGF-beta receptor. Based on these findings, we propose that hypoxia-induced tumor cell tolerance to glucose starvation is caused by hypoxia-induced TGF-beta1 through AMPK-alpha activation and the Akt/ARK5 system.
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PMID:Involvement of transforming growth factor-beta 1 signaling in hypoxia-induced tolerance to glucose starvation. 1601 25

The Peutz-Jegher syndrome tumor-suppressor gene encodes a protein-threonine kinase, LKB1, which phosphorylates and activates AMPK [adenosine monophosphate (AMP)-activated protein kinase]. The deletion of LKB1 in the liver of adult mice resulted in a nearly complete loss of AMPK activity. Loss of LKB1 function resulted in hyperglycemia with increased gluconeogenic and lipogenic gene expression. In LKB1-deficient livers, TORC2, a transcriptional coactivator of CREB (cAMP response element-binding protein), was dephosphorylated and entered the nucleus, driving the expression of peroxisome proliferator-activated receptor-gamma coactivator 1alpha (PGC-1alpha), which in turn drives gluconeogenesis. Adenoviral small hairpin RNA (shRNA) for TORC2 reduced PGC-1alpha expression and normalized blood glucose levels in mice with deleted liver LKB1, indicating that TORC2 is a critical target of LKB1/AMPK signals in the regulation of gluconeogenesis. Finally, we show that metformin, one of the most widely prescribed type 2 diabetes therapeutics, requires LKB1 in the liver to lower blood glucose levels.
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PMID:The kinase LKB1 mediates glucose homeostasis in liver and therapeutic effects of metformin. 1630 21

Tuberous sclerosis is an autosomal-dominant disorder caused by the mutation of one of the two tumor suppressor genes: TSC1 or TSC2, encoding protein products, hamartin, and tuberin, respectively. Both proteins form intracellular complexes exerting inhibitory activity on mammalian target of rapamycin (mTOR) kinase. It has been demonstrated that signal transduction from tuberin to mTOR is mediated by a G protein, Ras homologue enriched in brain (Rheb). In normal cells, tuberin having GTPase-activating protein properties toward Rheb controls signals of nutrient depletion, hypoxia, or stress, not allowing activation of mTOR and subsequent protein translation and cell proliferation. However, when environmental conditions change, tuberin is phosphorylated and it forms a complex with hamartin is degraded, and downstream targets of mTOR, S6K, and eEF2K, can be activated. In this review, we summarize very recent information contributing to our knowledge of TSC2 regulation by four cellular signaling pathways: PI3K/Akt, Ras/MAPK, LKB1/AMPK, and REDD1.
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PMID:Positive and negative regulation of TSC2 activity and its effects on downstream effectors of the mTOR pathway. 1639 86


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