Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.13.3 (histidine kinase)
 2,405 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The proportion of hexokinase (HK; EC 2.7.1.1) isozyme 1 (HK1) that is bound to the outer mitochondrial membrane is tissue specific and developmentally regulated. HK activity is known to be markedly elevated in many cancer cells and a significant fraction is mitochondrial bound. This study examined the role of the 15-amino acid N-terminal domain of HK1 in binding to liver and hepatoma mitochondria. A chimeric reporter construct, pCMVHKCAT, encoding this HK1 domain coupled to the chloramphenicol acetyltransferase (CAT) gene was electroporated into mouse Hepa 1-6 hepatoma cells. After digitonin treatment, cell fractions were assayed for HK, lactate dehydrogenase, and CAT activities. Digitonin (75 micrograms/mg of protein) caused cytosolic leak but 70% of HK remained with the pellet. HKCAT, like HK, remained predominantly with the pellet; CAT form the control, pCMVCAT, remained mostly unbound. Binding of membrane-free cell extracts to rat liver mitochondria in vitro showed 91% of the HKCAT bound, whereas only 12% of CAT bound. Specificity of HKCAT binding to mitochondria was demonstrated by competition of HK1 for HKCAT binding sites on rat liver mitochondria as well as by blockage of HKCAT binding by N,N'-dicyclohexylcarbodiimide, which covalently binds to porin and blocks HK1 binding. Deletional mutant constructs of HKCAT showed reduced binding with increasing deletion size. In summary, these studies demonstrate that the 15-amino acid N-terminal domain of HK1 is necessary and sufficient to confer mitochondrial binding properties to CAT and that there is specificity for this binding to the mitochondria.
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PMID:Targeting of hexokinase 1 to liver and hepatoma mitochondria. 130 5

A long-term cell culture epithelioid cell line was established from a recurrent squamous carcinoma of the nasopharynx of a Chinese male 17 1/2 years after radiation therapy. The cell line, designated NPC/HK1, has been passed 72 times over a period 1 year. The cells have been shown by light and electron microscopies to be of the squamous epithelial type. When they were transplanted subcutaneously into the back of athymic nude BALB/c (nu/nu) mice, tumors developed at the sites of inoculation, which on histological examination were shown to be well-differentiated squamous carcinomas, similar in morphology to the recurrent human tumor from which they were derived. Karyotypic analysis of cells from the cell line demonstrates an aneuploid human type with a modal chromosome number of 74 with both numerical and structural aberrations. Viral particles or Epstein-Barr viral nuclear antigen (EBNA) has not been demonstrated in the cells from the primary culture or several of the subcultures tested. The presence of EBNA in touch smears prepared from the biopsy tissue was inconclusive. Infection of the subcultured cells with EBV from P3HR1 and B95-8 cells was unsuccessful.
Int J Cancer 1980 Aug
PMID:Establishment of a cell line (NPC/HK1) from a differentiated squamous carcinoma of the nasopharynx. 625 64

Transgenic mice that expressed v-fos exclusively in the epidermis by means of a human keratin K1-based targeting vector (HK1.fos) developed preneoplastic epidermal hyperplasia and hyperkeratosis after long latency and an associated wound promotion stimulus. To assess the requirements for papilloma formation and malignant conversion and determine the sensitivity to a chemical promotion stimulus, HK1.fos mice were promoted with 12-O-tetradecanoylphorbol-13-acetate (TPA). HK1.fos mice were sensitive to TPA promotion but developed papillomas only after long latency (20-30 weeks of promotion) and in relatively few numbers per animal, suggesting the necessity of an additional genetic event prior to overt lesion formation. Consistent with this idea, at 60 weeks, on cessation of TPA promotion, these HK1.fos TPA-papillomas were found to be autonomous, TPA-independent tumors which persisted, grew larger, and converted to malignancy. Analysis of HK1.fos tumor RNA and DNA identified endogenous c-rasHa mutations at codons 12 and 61 in papillomas and carcinomas; however, no p53 tumor suppressor gene mutations were detected. These data indicate that epidermal expression of v-fos induces sensitivity to TPA promotion, but since additional genetic events, such as endogenous c-rasHa activation, appear to be required in tumorigenesis, v-fos may predominantly play a role in the mechanism of promotion to achieve papilloma autonomy and TPA independence. Furthermore, spontaneous malignant conversion in this model does not appear to involve mutations in the p53 tumor suppressor gene.
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PMID:12-O-tetradecanoylphorbol-13-acetate promotion of transgenic mice expressing epidermal-targeted v-fos induces rasHA-activated papillomas and carcinomas without p53 mutation: association of v-fos expression with promotion and tumor autonomy. 754 54

Hexokinase plays an important role in glucose-utilizing tissues like normal brain and cancers. In these tissues, hexokinase (HK) is mainly bound to mitochondria (mHK). Our objectives were to evaluate total HK (tHK) activity and mHK fraction in gliomas and to determine whether mHK binding could be targeted for therapy. Tumors were obtained from 26 patients and 13 were xenografted. HK, lactate and ATP were measured in cytosol and mitochondria extracts. The tHK expressed in mU/mg protein were 147 +/- 19 and 78 +/- 12, in fresh gliomas and xenografts, respectively, and of 489 in the normal brain. The mHK fraction was 76% in normal brain, 74 +/- 4% in fresh tumors and 53 +/- 6% in xenografts. Lactate/mHK ratios were higher in gliomas than in normal brain. The ATP was 10, 52 +/- 31 and 19 +/- 8 nmol/mg protein in normal brain, xenografts and fresh gliomas respectively. Loss of one copy of chromosome 10 which carries the HK1 gene, was evidenced in 11 of the 13 xenografted gliomas. The anti-tumor effect of lonidamine (LND), which affects glycolysis in interfering with mHK activity, was tested in nude mice bearing 4 gliomas. LND (125 mg/kg, given i.p., twice daily for 5 days) led to a growth inhibition of TG-7-RO of 72%, with 2-fold growth retardation, and had no effect for TG-8-OZ. Intermediate LND-sensitivities for TG-11-DU and TG-10-PY were noted. The LND-sensitivity was correlated with the mHK activity (R2 = 0.73) and mHK fraction (R2 = 0.88). HK binding to mitochondria is a key of glycolysis in malignant gliomas, and targetting this binding with appropriate agents could be an effective therapeutic approach.
Int J Cancer 1995 Jul 17
PMID:Mitochondria-bound hexokinase as target for therapy of malignant gliomas. 762 99

To investigate the effect of p53 tumor suppressor gene loss in the mouse skin model of multistage carcinogenesis, p53 knockout mice, generated by gene targeting (p53 -/-), were mated to transgenic mice expressing v-rasHa (HK1.ras), v-fos (HK1.fos), or human transforming growth factor alpha+HK1.TGFalpha) exclusively in the epidermis, by means of a keratin K1-based targeting vector (HK1). HK1-p53 transgenic progeny expressing wild-type p53 alleles (p53 +/+) or hemizygous for the p53 knockout allele (p53+/-) were identical to parental HK1 lines and exhibited neonatal epidermal hyperplasia or wound-associated hyperplasia in adults, together with spontaneous or 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced benign papillomas. Mating to p53-/- did not lead to the expected tumorigenesis in adults. Instead, whereas HK1.ras or HK1.TGFalpha transgenic mice null for p53 (HK1.ras-p53-/- and HK1.TGFalpha-p53-/-, respectively) retained the neonatal epidermal hyperplasia phenotype, in adults, spontaneous and TPA-promoted papilloma formation was blocked. Similarly, wound-associated epidermal hyperplasia/hyperkeratosis, a hallmark of adult HK1.fos phenotypes, was completely absent in HK1.fos-p53 -/- mice. Histological, immunofluorescence, and bromodeoxyuridine labeling analysis of neonatal or adult epidermis in HK1-p53 transgenic genotypes +/+, +/-, and -/- for p53 revealed no obvious differences in morphology, expression of keratinocyte differentiation markers, or mitotic index attributed to p53 loss. To determine whether the paradoxical absence of papillomas centered on up-regulation of p53 target genes, WAF1/CIP1/p21 RNA expression levels were examined in TPA promotion experiments. WAF1/CIP1/p21 expression increased in response to TPA promotion in all HK1-p53 transgenic genotypes regardless of p53 status. However, in HK1-p53 null genotypes, although TPA-induced, p53-independent WAF1/CIP1/p21 expression was observed, no large increase in expression was associated with the observed paradoxical tumorigenesis block. These data suggest that epidermis is somewhat resistant to the neoplastic effects of p53 loss, possibly possessing several compensatory systems. Alternatively, there may be a requirement forp53 expression in response to TPA or a wound-promotion stimulus in mouse epidermis.
Cancer Res 1996 Oct 01
PMID:Paradoxical tumor inhibitory effect of p53 loss in transgenic mice expressing epidermal-targeted v-rasHa, v-fos, or human transforming growth factor alpha. 881 35

Nonmelanoma skin cancers (NMSC) are among the most common malignancies in the world. Typically, these neoplasms grow slowly and are comparatively indolent in their clinical behavior. The most frequent molecular alterations implicated in the pathogenesis of these neoplasms involve genes known to be regulators of cell death including p53, Ha-ras and bcl-2. In order to evaluate the significance cell death deregulation during skin carcinogenesis, we generated a transgenic mouse model (HK1.bcl-2) using the human keratin 1 promoter to target the expression of a human bcl-2 minigene to the epidermis. Transgenic HK1.bcl-2 protein was expressed at high levels specifically in the epidermis extending from the stratum basale through the stratum granulosum. The epidermis of HK1.bcl-2 mice exhibited multifocal hyperplasia without associated hyperkeratosis and aberrant expression of keratin 6. The rate of proliferation was similar in HK1.bcl-2 and control epidermis although suprabasal BrdUrd incorporating cells were present only in HK1.bcl-2 skin. Keratinocytes from the HK1.bcl-2 mice were significantly more resistant to cell death induction by U.V.-B, DMBA, and TPA, compared to control keratinocytes. Furthermore, papillomas developed at a significantly greater frequency and shorter latency in the HK1.bcl-2 mice compared to control littermates following initiation with DMBA and promotion with TPA. Together these results support a role for bcl-2 in the pathogenesis of NMSC.
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PMID:Human keratin-1.bcl-2 transgenic mice aberrantly express keratin 6, exhibit reduced sensitivity to keratinocyte cell death induction, and are susceptible to skin tumor formation. 948 76

To develop an in vivo model for studying the role of the p53 tumor suppressor in skin carcinogenesis, a murine p53(172H) mutant (equivalent to human p53(175H)) was expressed in the epidermis of transgenic mice, utilizing a targeting vector based on the human keratin 1 gene (HK1.p53m). HK1.p53m mice developed normally and did not exhibit an obvious epidermal phenotype or develop spontaneous tumors. However, these mice demonstrated an increased susceptibility to a two-stage chemical carcinogenesis protocol, with the rate of formation and number of papillomas being dramatically increased as compared to non-transgenic controls. The majority of papillomas in control mice regressed after termination of 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment, whereas p53m papillomas progressed to carcinomas and metastases. In addition, more advanced malignancy, i.e., undifferentiated spindle cell carcinomas, were exclusively observed in p53m mice. Increased bromodeoxyuridine (BrdU) labeling, accompanied by decreased expression of p21, was observed in HK1.p53m papillomas. In situ examination of centrosomes in HK1.p53m papillomas also revealed marked abnormalities, with 75% of the cells containing > or = 3 centrosomes/cell, whereas centrosome numbers in papillomas from control animals remained normal. These data suggest that the accelerated tumorigenesis observed in chemically-treated p53m mice is most likely due to increased genomic instability resulting from an inhibition of G1 arrest and abnormal amplification of centrosomes.
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PMID:Expression of a p53 mutant in the epidermis of transgenic mice accelerates chemical carcinogenesis. 967 12

The p16 gene, encodes a key checkpoint protein p16 in the cell cycle, has been reported inactivation in a wide variety of human cancers. We have previously demonstrated high frequency of p16 alterations in primary nasopharyngeal carcinoma (NPC), xenografts and cell lines. The finding implied that inactivation of the p16 gene may play an important role in the NPC development. To investigate the tumour suppressor function of p16 in NPC, we transfected p16-deficient NPC cell line, NPC/HK-1, with a wild-type p16 expression construct, and evaluated growth and tumorigenic properties of the clones stably expressing exogenous p16. Expression of the exogenous wild-type p16 significantly inhibited cell growth by more than 70% when compared to that of the parental and empty vector-transfected cells. This growth inhibition was attributable to a significant proportion of p16-expressing cells arrested at G1 phase in the cell cycle as revealed by flow cytometric analysis. By anchorage-independent colony forming assay, we found that the ability to form colonies in soft agar was highly reduced in cells expressing p16. NPC/HK1 cells expressing functional p16 also showed suppressed tumorigenicity in athymic nude mice. Taken together, our results provide strong evidence for a tumour suppressor role of p16 in NPC.
Br J Cancer 1999 Dec
PMID:Inhibiting tumorigenic potential by restoration of p16 in nasopharyngeal carcinoma. 1058 71

Photodynamic therapy (PDT) is a new approach to cancer treatment for a variety of malignant tumors. In this study, two clinical photosensitizers, Temoporfin (meta-tetra-hydroxyl-phenyl-chlorin; mTHPC) and merocyanine 540 (MC540), were selected to explore for their photocytotoxic and genotoxic effects on nasopharyngeal carcinoma cells (NPC/HK1 and CNE2). Results of tetrazolium reduction assay showed that 80% cell killing were achieved for both cell lines at 0.4 microg/ml mTHPC for 24 h incubation and then with 40 kJ/m2 light irradiation, whereas 40 microg/ml MC540 with 50 kJ/m2 light dosage was required to attain the same level of phototoxicity for NPC/HK1. On the contrary, NPC/CNE2 was quite resistant to MC540. Hence, mTHPC-mediated PDT exerted a more potent effect than MC540-mediated PDT, even though the molar extinction coefficient of the main absorption peak for MC540 is much higher than that of mTHPC. Dark cytotoxicity remained negligible for both sensitizers. Comet assay was used to evaluate the DNA strand break and potential genotoxic effect induced by mTHPC and MC540 on the NPC cells. No DNA strand break was detected in the absence of light, and under sublethal treatment (LD25) for either sensitizer-loaded cells. Confocal laser scanning microscopy showed that mTHPC and MC540 localized in the cytoplasm but not in the nucleus of the tumor cells, which provided evidence for undetectable DNA damage under dark and low photodynamic dose.
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PMID:Photocytotoxic and DNA damaging effect of temoporfin (mTHPC) and merocyanine 540 (MC540) on nasopharyngeal carcinoma cell. 1081 31

The phosphorylation of glucose, a crucial step in cellular metabolism, is catalysed by hexokinases (HK), of which there are four (HKI-IV) in mammalian tissues. The brain HK, (HK1), like HKII and HKIII, has a molecular weight of approximately 100 kDa. HKII is insulin-sensitive and found in adipose and muscle cells. HKIV, also known as glucokinase, has a molecular weight of 50 kDa and is specific to liver and pancreas. Most brain HK is bound to mitochondria via porins, enabling coordination between glucose consumption and oxidation. Tumour cells are known to be highly glycolytic, and correspondingly increased expression of glycolytic enzymes, including HK, have been detected in resected tumours from patients with lung, gastrointestinal and breast cancer. In the latter group, further increases in HK activity were associated with metastatic disease. Some studies have demonstrated increased HK activity in renal tumours, and also have reported changes in the isoenzymic expression of HK. Experimental studies of the initiation and progression of liver tumours have demonstrated a shift in expression from that of HKIV to HKI and HKII, with increased HK binding to mitochondria and a > 100-fold increase in HK activity. However, studies using xenografts derived from gliomas found decreased HK activity corresponding with loss of chromosome 10, the carrier of the HKI gene. Compared with normal tissues, a number of mechanisms are associated with changes in HK activity seen in tumours of the liver and other sites, and these include HK gene dosage, increased transcription, modulation of HK promoter activity by a broader range of effectors, and increased mitochondrial binding of HK. Increased HK activity, together with increased glucose transport by tumour cells, has been exploited in cancer imaging using the positron-labelled glucose analogue (18F)fluoro-2-deoxy-D-glucose (FDG), which is transported into cells and then phosphorylated, but undergoes little further metabolism. Accumulated FDG then can be detected using positron emission tomography (PET).
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PMID:Mammalian hexokinases and their abnormal expression in cancer. 1091 95


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