Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have demonstrated previously that D-myo-inositol 4-(hexadecyloxy)-3(S)-methoxybutanephosphonate (C4-PI), an isosteric phosphonate analog of phosphatidylinositol developed to inhibit inositol lipid metabolism, was unable to inhibit phosphatidylinositol (PI) 3-kinase activity. We now report the effects of the compound on other aspects of inositol metabolism. We demonstrated that C4-PI inhibits the activity of purified recombinant PI-phospholipase C-beta (PLC-beta) at all concentrations tested; it enhanced the activity of PI-PLC-gamma and PI-PLC-delta at low concentrations (10 microM), while severely inhibiting their activities at higher concentrations. In the breast cancer cell lines MCF-7 (estrogen receptor positive) and MDA-MB-468 (estrogen receptor negative), C4-PI had no effect on the uptake of D-myo-inositol but severely inhibited its incorporation into PI. In spite of the drastic decrease in PI synthesis, C4-PI did not affect the levels of inositol incorporated into phosphatidylinositol 4,5-bisphosphate (PIP2) in the cells. In vitro assays showed that C4-PI inhibited PI synthase activity (inhibition of 35% at 50 microM) but had little effect on PI 4-kinase activity (inhibition of 13% at 150 microM). C4-PI inhibited the proliferation of MCF-7 and MDA-MB-468 cell lines with IC(50) values of 12 and 18 microM. Taken together, the results suggest that the accumulation of [3H]inositol in PIP2 in cells incubated with C4-PI may be due to the inhibition of PIP2 hydrolysis in the cells with no effect on its synthesis. The role of these C4-PI-induced effects in the mechanism of growth inhibition by C4-PI remains to be established.
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PMID:Effects of a water-soluble antitumor ether phosphonoinositide, D-myo-inositol 4-(hexadecyloxy)-3(S)-methoxybutanephosphonate (C4-PI), on inositol lipid metabolism in breast epithelial cancer cell lines. 1123 Aug 3

This study examined the effect of tamoxifen, an anti-breast cancer drug, on Ca2+ handling in bladder female transitional cancer cells. Changes in cytosolic free Ca2+ levels were recorded by using the Ca2+-sensitive dye fura-2. In a dose-dependent manner, tamoxifen induced intracellular free Ca2+ concentrations ([Ca2+]i) increases between 5 and 20 microM with an EC50 of 10 microM. External Ca2+ removal reduced the response by 60+/-6%. Addition of 3 mM Ca2+ caused a [Ca2+]i increase after pretreatment with 10 microM tamoxifen in Ca2+-free medium. In Ca2+-free medium, pretreatment with 10 microM tamoxifen abolished the [Ca2+]i increase induced by 1 microM thapsigargin, an endoplasmic reticulum Ca2+ pump inhibitor. Conversely, pretreatment with 1 microM thapsigargin prevented tamoxifen from releasing more Ca2+. Inhibition of phospholipase C-dependent inositol 1,4,5-tris-phosphate formation with 2 microM U73122 did not alter 10 microM tamoxifen-induced Ca2+ release. The [Ca2+]i increase induced by 5 microM tamoxifen was not altered by 10 microM La3+, nifedipine, verapamil, and diltiazem. Collectively, it was found that tamoxifen increased [Ca2+]i in bladder cancer cells by releasing Ca2+ from the endoplasmic reticulum Ca2+ stores in a manner independent of phospholipase C activity, and by inducing Ca2+ entry from external medium.
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PMID:Tamoxifen-induced Ca2+ mobilization in bladder female transitional carcinoma cells. 1140 40

Tamoxifen has been shown to increase cytoplasmic free Ca2+ levels [Ca2+]i in renal tubular cells and bladder cancer cells, and to after Ca2+ signaling in MCF-7 breast cancer cells. The present study examined the effect of tamoxifen on [Ca2+], in ZR-75-1 human breast cancer cells using fura-2 as an indicator. Tamoxifen increased [Ca2+]i at a concentration above 2 microM with an EC50 of 5 microM. Removing extracellular Ca2+ reduced the response by 48+/-2%. In Ca2+-free medium, after tamoxifen-induced [Ca2+]i increased had returned to baseline, adding 3 mM Ca2+ increased [Ca2+]i in a concentration-dependent manner. Further, pretreatment with 10 microM tamoxifen abolished the [Ca2+]i increase induced by 1 microM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor); and conversely, pretreatment with thapsigargin prevented tamoxifen from releasing more Ca2+. Tamoxifen (10 microM)-induced Ca2+ release was not changed by inhibiting phospholipase C activity with 2 microM U73122. Trypan blue exclusion assay revealed that tamoxifen (1-10 microM) did not alter viability after 1 min of incubation, but killed 10% of cells after 3-10 min of incubation. Together, this study shows that tamoxifen (>2 microM) induced a significant, immediate increase in [Ca2+]i in ZR-75-1 breast cancer cells. Tamoxifen acted by releasing Ca2+ from the endoplasmic reticulum Ca2+ stores in a manner independent of phospholipase C activity, and by inducing Ca2+ entry from extracellular medium. Tamoxifen may be of mild cytotoxicity after acute exposure.
Breast Cancer Res Treat 2002 Jan
PMID:Tamoxifen-induced increases in cytoplasmic free Ca2+ levels in human breast cancer cells. 1188 10

The pineal hormone, melatonin, has been shown to inhibit the proliferation of the estrogen receptor alpha (ERalpha)-positive macrophage chemotactic factor (MCF)-7 human breast cancer cells. Previous studies from other systems indicate that melatonin modulates the calcium (Ca2+)/calmodulin (CaM) signaling pathway either by changing intracellular calcium concentration ([Ca2+]i) via activation of its G-protein coupled membrane receptors, or through a direct interaction with CaM. In this study, although melatonin alone had no effect on basal [Ca2+]i in MCF-7 cells, it significantly enhanced the elevation of [Ca2+]i induction by extracellular adenosine triphosphate (ATP), which increases [Ca2+]i via the G protein-coupled P2y-purinoceptor and the phospholipase C (PLC) pathway. Pretreatment of MCF-7 cells with 10(-7) M melatonin increased the 10(-5) M ATP-induced [Ca2+]i peak change from 79.4 +/- 11.6 nM to 146.2 +/- 22.3 nM. Furthermore, without changing total cellular CaM levels, melatonin markedly increased the amount of membrane-bound CaM to 237 and 162% of control levels after I and 6 hr of treatment, respectively. Cytosolic CaM levels were also elevated to 172% of control after 6 hr of melatonin treatment. Correlative growth studies demonstrated that ATP (10(-5) M) can stimulate MCF-7 cell growth, that melatonin can suppress MCF-7 cell proliferation, but that pretreatment of MCF-7 cells with melatonin followed by ATP(10(-5) M), like 10(-4) M ATP can further suppress MCF-7 cell proliferation; this indicates that melatonin's potentiation of ATP induced [Ca2+]i may be above the threshold for cell growth. Given the important role of [Ca2+]i and CaM in tumor cell homeostasis and proliferation and melatonin's modulation of [Ca2+]i, melatonin's effects on the Ca2+/CaM signaling pathway may play an important role in mediating the growth-inhibitory effect of melatonin on MCF-7 human breast cancer cells.
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PMID:Modulation of intracellular calcium and calmodulin by melatonin in MCF-7 human breast cancer cells. 1207 68

The anti-breast cancer drug tamoxifen has recently been shown to cause an increase in [Ca(2+)]i in renal tubular cells, breast cells and bladder cells. Because tamoxifen is known to interact with oestrogens leading to modulation of bone metabolism, the present study was aimed at exploring whether tamoxifen could alter Ca(2+) signaling in human osteoblast-like MG63 cells. Cytosolic free Ca(2+) levels were recorded by using the Ca(2+)-sensitive dye fura-2. Tamoxifen induced a sustained [Ca(2+)]i increase at concentrations above 1 microM with an EC(50) of 8 microM. Removal of extracellular Ca(2+) reduced the response by 40%, suggesting that tamoxifen induced both Ca(2+) influx and store Ca(2+) release. Tamoxifen-induced Ca(2+) influx was confirmed as tamoxifen caused Mn(2+) influx-induced quench of fura-2 fluorescence. In Ca(2+)-free medium, pretreatment with 10 microM tamoxifen abolished the [Ca(2+)]i increase induced by 1 microM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor), and by 2 microM carbonylcyanide m-chlorophenylhydrazone (a mitochondrial uncoupler). Conversely, pretreatment with thapsigargin and carbonylcyanide m-chlorophenylhydrazone only reduced 64% of tamoxifen-induced [Ca(2+)]i increases. Addition of 2 microM U73122 to inhibit phospholipase C activity abolished the [Ca(2+)]i increase induced by 1 microM histamine, a phospholipase C-dependent Ca(2+) mobilizer, without affecting 10 microM tamoxifen-induced Ca(2+) release. The [Ca(2+)]i increase induced by 10 microM tamoxifen was not altered by 10 microM of nifedipine, verapamil and diltiazem. Together, the data show that tamoxifen induced a lasting increase in [Ca(2+)]i in human osteoblast-like cells by causing Ca(2+) influx and releasing Ca(2+) from multiple stores in a phospholipase C-independent manner.
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PMID:Effect of the anti-breast cancer drug tamoxifen on Ca(2+) movement in human osteosarcoma cells. 1219 59

Induction of tumor cell migration is a key step in invasion and metastasis. Here we report that the epidermal growth factor (EGF)-induced cell migration of breast cancer cells is attributed to a transient, rather than a sustained, activation of phospholipase C (PLC)-gamma1 due to c-erbB-2 signaling. EGF stimulation of EGF receptor (EGFR) overexpressing cells resulted in long-term PLC-gamma1 tyrosine phosphorylation and sustained levels of inositol-1,4,5-triphosphate (IP3) and diacylglycerol (DAG) producing sinusoidal calcium oscillations. In contrast, c-erbB-2/EGFR expressing cells displayed baseline transient calcium oscillations after EGF treatment due to short-term PLC-gamma1 tyrosine phosphorylation and short-term IP3 and DAG turnover. A third cell line expressing a point-mutated c-erbB-2 receptor that lacks the autophosphorylation Y1248 was generated to investigate whether the different PLC-gamma1 activation was attributed to this structure. Neither PLC-gamma1 tyrosine phosphorylation nor IP3 and DAG turnover and calcium oscillations were observed in this cell line, indicating the modulation of the PLC-g1 activation time course by c-erbB-2 signaling. Induction of cell migration was solely observable in the c-erbB-2-positive cell line as proved by the mode of actin reorganization and a cell migration assay, using a 3D-collagen lattice. In summary, c-erbB-2 up-regulation switches on the cell migration program by modulating the time course of PLC-gamma1 activation.
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PMID:Induction of cancer cell migration by epidermal growth factor is initiated by specific phosphorylation of tyrosine 1248 of c-erbB-2 receptor via EGFR. 1235 93

Little is known about the regulation of cytosolic calcium Ca(2+) levels ([Ca(2+)](i)) in breast cancer cells. We investigated the existence of capacitative calcium entry (CCE) in the tumorigenic cell line MCF-7 and its responsiveness to ATP. MCF-7 cells express purinergic receptors as well as estrogen receptors (ER). Depletion of calcium stores with thapsigargin (TG, 500 nM) or ATP (10 microM) in the absence of extracellular Ca(2+), resulted in a rapid and transient elevation in [Ca(2+)](i). After recovery of basal levels, Ca(2+) readmission (1.5 mM) to the medium increased Ca(2+) influx (twofold over basal), reflecting pre-activation of a CCE pathway. Cells pretreated with TG were unable to respond to ATP, thus indicating that the same Ca(2+) store is involved in their response. Moreover, IP(3)-dependent ATP-induced calcium mobilization and CCE were completely blocked using compound U-73122, an inhibitor of phospholipase C. Compound 2-APB (75 microM) and Gd(3+) (10 microM), antagonists of the CCE pathway, completely prevented ATP-stimulated capacitative Ca(2+) entry. CCE in MCF-7 cells was highly permeable to Mn(2+) and to the Ca(2+) surrogate Sr(2+). Mn(2+) entry sensitivity to Gd(3+) matched that of the Ca(2+) entry pathway. 17Beta-estradiol blocked ATP-induced CCE, but was without effect on TG-induced CCE. Besides, the estrogen blockade of the ATP-induced CCE was completely abolished by preincubation of the cells with an ER monoclonal antibody. ER alpha immunoreactivity could also be detected in a purified plasma membrane fraction of MCF-7 cells. These results represent the first evidence on the operation of a ATP-responsive CCE pathway in MCF-7 cells and also indicate that 17beta-estradiol interferes with this mechanism by acting at the cell surface level.
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PMID:Evidence on the operation of ATP-induced capacitative calcium entry in breast cancer cells and its blockade by 17beta-estradiol. 1239 14

The aim of our work was to study the influence of primary breast cancer on mature erythrocyte membranes. Blood was sampled from 29 women with primary breast cancer, aged 35-86 years, in different stages of clinical progression of the disease. In red blood cell membranes an increase of phosphatidylinositol-4-phosphate and phosphatidylinositol-4,5-diphosphate levels was observed. These changes were accompanied by a decrease in phospholipase C activity. Simultaneously, a significant decrease in concentration of phosphatidylserine, sphingomyelin, and phosphatidylinositol was found. Quantitative protein evaluation showed an increase in band 4.1 protein content with no changes in the level of constitutive PKCalpha responsible for the phosphorylation of this protein and its affinity to glycophorine C. In parallel a greater increase of PKCalpha translocation after PMA treatment compared to controls was observed. Possible oxidative damage of erythrocyte membranes indicated by an increase in malonyldialdehyde level and decrease in SH-group content as well as by an increase in the w/ ratio was documented. From the results it is concluded that primary breast cancer seems to affect the membranes of mature erythrocytes.
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PMID:Alterations in skeletal protein, distribution of PKCalpha, and level of phospholipids in erythrocyte membranes of women with primary breast cancer. 1249 Feb 89

It has been reported that overexpression of the epidermal growth factor receptor (erbB1) or its homologous receptor, HER2 (erbB2), can confer antiestrogen resistance to estrogen receptor (ER)-positive human breast cancer cells. Aberrant signaling by receptors of the erbB network up-regulates a number of signaling pathways, which include phospholipase C-gamma1, Ras-Raf-mitogen-activated protein/extracellular signal-regulated kinase kinase-mitogen-activated protein kinase, phosphatidylinositol 3'-kinase and its target, the serine/threonine kinase Akt, stress-activated protein kinases, signal transducers and activators of transcription, and c-Jun-NH(2)-terminal kinase (JNK). Akt has been reported to induce estrogen-independent transcription of ER. Here we show that transfection of ER-positive, HER2 gene-amplified BT-74 cells with an expression vector encoding dominant-negative (K179M) Akt1 partially restored the ability of tamoxifen to inhibit estradiol-stimulated ER reporter activity. Infection of MCF-7 cells with an adenovirus encoding myristoylated, constitutively active Akt induced ER reporter activity in the absence of estradiol and resulted in tamoxifen resistance of these cells in culture. Data will be presented to suggest that, in addition to mitogen-activated protein kinase, Akt is an important mediator of HER2-mediated antiestrogen resistance in human breast cancer cells.
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PMID:ErbB (HER) receptors can abrogate antiestrogen action in human breast cancer by multiple signaling mechanisms. 1253 8

Osteopontin (OPN) is a secreted, integrin-binding glycophosphoprotein that has been implicated in breast cancer. We previously showed that OPN-induced cell migration of mammary epithelial cells (MEC) depends on binding to cell surface integrins and involves activation of the hepatocyte growth factor (HGF) receptor, Met. Here, we show that OPN-induced migration of MEC also requires activation of the epidermal growth factor (EGF) pathway. Synergism was seen between EGF and OPN in inducing cell migration. Furthermore, incubation of cells with exogenous OPN increased ligand (TGFalpha> EGF) and EGF receptor (EGFR) mRNA expression, as well as EGFR kinase activity. Treatment of cells with anti-TGFalpha or anti-EGFR antibody, or with tyrphostin-25 (EGFR inhibitor), significantly impaired the cell migration response to OPN. Other more broad-spectrum tyrosine kinase inhibitors and the growth factor/ receptor interaction inhibitor, suramin, also inhibited OPN-induced migration. Using specific signal transduction pathway inhibitors, we have screened for involvement of MEK (MAP kinase kinase), phosphatidylinositol 3-kinase, phospholipase C (PLC), and protein kinase C (PKC). Results implicated all of these pathways in OPN-induced cell migration, the most pronounced effect being seen with PLC and PKC inhibitors. These results suggest that induction of MEC migration by OPN involves a cascade of events including at least two growth factor/receptor pathways and multiple downstream signal transduction pathways. A number of potential targets are thus provided for strategies aimed at blocking the malignancy-promoting effects of OPN.
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PMID:Osteopontin-induced migration of human mammary epithelial cells involves activation of EGF receptor and multiple signal transduction pathways. 1260 46


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