Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Anti-oestrogen is effective for the treatment of oestrogen receptor (ER)-positive breast carcinomas, but most of these tumours become resistant to anti-oestrogen. It has been suggested that anti-oestrogen therapy may induce a HER2 signalling pathway in breast cancer cells and this may cause resistance to anti-oestrogen. Thus, it is conceivable that combined therapy with anti-oestrogen and anti-HER2 antibody might be more effective. In the present study, we investigated the effect of combined treatment with a humanized anti-HER2 monoclonal antibody, rhumAbHER2 (trastuzumab), and an anti-oestrogen, ICI 182,780, on the cell growth of three human breast cancer cell lines which respectively express different levels of ER and HER2. The combined treatment enhanced the growth inhibitory effect on ML-20 cells, which express a high level of ER and a moderate level of HER2, but showed no additive effect on either KPL-4 cells, which express no ER and a moderate level of HER2, or MDA-MB-231 cells, which express no ER and a low level of HER2. It is also suggested that both the antibody and anti-oestrogen induce a G1-S blockade and apoptosis. These findings indicate that combined treatment with anti-HER2 antibody and anti-oestrogen may be useful for the treatment of patients with breast cancer expressing both ER and HER2.
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PMID:Anti-HER2 antibody enhances the growth inhibitory effect of anti-oestrogen on breast cancer cells expressing both oestrogen receptors and HER2. 1063 65

Transcription of the ERBB2 oncogene is repressed by oestrogen in human breast cancer cells. We show that a 218 bp fragment of the human ERBB2 gene promoter is responsive to oestrogen in transient transfection in ZR75.1 and SKBR.3 cells when the oestrogen receptor is expressed. Deletion analysis of this fragment shows that a sequence located at the 5' end, which is known to mediate ERBB2 overexpression in breast cancer, is also responsible for the oestrogen response. This sequence binds AP-2 transcription factors and appears functionally identical to an element of the oestrogen-dependent enhancer described in the first intron of human ERBB2. We observed that oestrogen treatment down-regulates expression of AP-2 proteins but does not affect the DNA binding activity of AP-2. Constitutive expression of AP-2beta or AP-2gamma, but not AP-2alpha, abrogates the estrogenic repression. Our results demonstrate that AP-2 transcription factors are implicated in the oestrogenic regulation of ERBB2 gene expression and suggest a complex interplay involving the different AP-2 isoforms and other unidentified factors.
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PMID:AP-2 transcription factors in the regulation of ERBB2 gene transcription by oestrogen. 1064 7

Overexpression of the ERBB2 proto-oncogene in breast tumours, which occurs in 25-30% of patients, correlates with poor prognosis. In oestrogen receptor (ER) positive breast epithelial cells oestrogens reduce ERBB2 mRNA and protein levels, an effect that is reversed in the presence of anti-oestrogens such as tamoxifen and ICI 182780. Our previous studies have shown that the major effect of oestrogen on ERBB2 expression is at the level of transcription and that this is mediated through a region within the ERBB2 first intron which can act as an oestrogen-suppressible enhancer in ER positive breast cells. In vitro footprinting of the smallest DNA fragment that retained full activity revealed four transcription factor binding sites. We report here that two of these sites are recognized by AP-2 proteins and the other two are bound by a variety of bZIP factors, including CREB and ATFI, with a major complex containing ATFa/ JunD. However, by using ER mutants it is clear that repression occurs essentially off the DNA. Indeed, the essential domain of the ER responsible for repression of the ERBB2 enhancer is a region termed AF2 which is required for the ligand-dependent association of non-DNA binding cofactors. We further demonstrate that one of these ER cofactors, SRC-1, can relieve oestrogen repression of the ERBB2 enhancer and conclude that these data fit with a model whereby the ER and the ERBB2 enhancer compete for this limiting, non-DNA binding cofactor. Thus, in oestrogenic conditions SRC-1 preferentially binds to the ER which effectively sequesters it thereby reducing enhancer activity, but in antioestrogenic media the cofactor is released from the ER and is therefore available to activate the ERBB2 enhancer.
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PMID:Cofactor competition between the ligand-bound oestrogen receptor and an intron 1 enhancer leads to oestrogen repression of ERBB2 expression in breast cancer. 1069 18

We are investigating novel, non-transcriptionally mediated mechanisms that may contribute to the differentiative effects of oestrogen in developing forebrain neurons. Recent findings in the cerebral cortex document that 17 alpha- and 17 beta-oestradiol elicit rapid and sustained activation of the Ras-Raf-MAP kinase cascade, a major growth factor signalling pathway. Using oestrogen receptor (ER) alpha knockout (ERKO) mice, we addressed the identity of the receptor mediating activation of the MAP kinase cascade. 17 beta-oestradiol increased B-Raf activity and MEK-dependent ERK phosphorylation in explants of wild-type and ERKO cerebral cortex. Although neither the ER alpha-selective ligand, 16 alpha-iodo-17 beta-oestradiol (16 alpha-IE2) nor the ER beta-selective ligand, genistein, elicited ERK phosphorylation, as little as 0.1 nM 17 beta-oestradiol did so. Moreover, 16 alpha-IE2 acted as an inhibitory modulator of ERK activation, and the ER antagonist ICI 182 780 blocked oestradiol action only in wild-type cultures. These data suggest that neither ER alpha nor ER beta mediate activation of the MAP kinase cascade. A putative, novel, oestradiol-sensitive and ICI 182 780-insensitive receptor, designated ER-X may, rather, be involved. Association of ER-X with flotillin, the neuronal homologue of the caveolar protein, caveolin, places ER-X within plasma membrane caveolae and supports the hypothesis that a membrane-associated ER may mediate rapid oestrogen activation of the MAP kinase cascade.
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PMID:Novel sites and mechanisms of oestrogen action in the brain. 1096 2

Activation of the heregulin/HER2 pathway in oestrogen receptor (ER)-positive breast-cancer cells leads to suppression of oestrogen-receptor element (ERE)-driven transcription and disruption of oestradiol responsiveness, and thus contributes to progression of tumours to more invasive phenotypes. Here we report the identification of metastatic-associated protein 1 (MTA1), a component of histone deacetylase (HDAC) and nucleosome-remodelling complexes, as a gene product induced by heregulin-beta1 (HRG). Stimulation of cells with HRG is accompanied by suppression of histone acetylation and enhancement of deacetylase activity. MTA1 is also a potent corepressor of ERE transcription, as it blocks the ability of oestradiol to stimulate ER-mediated transcription. The histone-deacetylase inhibitor trichostatin A blocks MTA1-mediated repression of ERE transcription. Furthermore, MTA1 directly interacts with histone deacetylase-1 and -2 and with the activation domain of ER-alpha. Overexpression of MTA1 in breast-cancer cells is accompanied by enhancement of the ability of cells to invade and to grow in an anchorage-independent manner. HRG also promotes interaction of MTA1 with endogenous ER and association of MTA1 or HDAC with ERE-responsive target-gene promoters in vivo. These results identify ER-mediated transcription as a nuclear target of MTA1 and indicate that HDAC complexes associated with the MTA1 corepressor may mediate ER transcriptional repression by HRG.
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PMID:Transcriptional repression of oestrogen receptor by metastasis-associated protein 1 corepressor. 1114 23

Angiogenesis is essential for tumour growth and metastasis. It is regulated by numerous angiogenic factors, one of the most important being vascular endothelial growth factor (VEGF). Recently VEGF-B, a new VEGF family member that binds to the tyrosine kinase receptor flt-1, has been identified. Although the importance of VEGF has been shown in many human tumour types, the contribution of VEGF-B to tumour neovascularization is unknown in any tumour type. This study therefore measured the mRNA level of VEGF-B and its receptor flt-1 by ribonuclease protection assay and the pattern of VEGF-B expression by immunohistochemistry in 13 normal breast samples and 68 invasive breast cancers. Flt-1 expression was significantly higher in tumours than in normal breast (p=0.02) but no significant difference was seen in VEGF-B between normal and neoplastic breast (p=0.3). There was a significant association between VEGF-B and node status (p=0.02) and the number of involved nodes (p=0.01), but not with age (p=0.7), size (p=0.6), oestrogen receptor (ER) (p=0.2), grade (p=0.5) or vascular invasion (p=0.16). No significant relationship was present between VEGF-B and flt-1 (p=0.2) or tumour vascularity (p=0.4). VEGF-B was expressed mostly in the cytoplasm of tumour cells, although occasional stromal components including fibroblasts and endothelial cells were also positive. No difference in VEGF-B expression was observed adjacent to regions of necrosis, in keeping with this VEGF family member not being hypoxically regulated. These findings suggest that VEGF-B may contribute to tumour progression by a non-angiogenic mechanism, possibly by increasing plasminogen activators and hence metastasis, as has been described in vitro. Measurement of VEGF-B together with other angiogenic factors may identify a poor prognostic patient group, which may benefit from anti-VEGF receptor therapy targeted to flt-1 (VEGFR1) as well as kdr (VEGFR2).
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PMID:VEGF-B expression in human primary breast cancers is associated with lymph node metastasis but not angiogenesis. 1124 11

Overexpression of G1-S regulators cyclin D1 or cyclin A is frequently observed in breast cancer and is also to result in ligand-independent activation of oestrogen receptor in vitro. This might therefore, provide a mechanism for failure of tamoxifen treatment. We examined by immunohistochemical staining the effect of deregulation of these, and other cell cycle regulators on tamoxifen treatment in a group of 394 patients with early stage breast cancer. In univariate analysis, expression of cyclin A, Neu, Ki-67 index, and lack of OR expression were significantly associated with worse prognosis. When adjusted by the clinical model (for lymph node status, age, performance status, T-classification, grade, prior surgery, oestrogen receptor status and tamoxifen use), only overexpression of cyclin A and Neu were significantly associated with worse prognosis with hazard ratios of, respectively, 1.709 (P=0.0195) and 1.884 (P=0.0151). Overexpression of cyclin A was found in 86 out of the 201 OR-positive cases treated with tamoxifen, and was the only independent marker associated with worse prognosis (hazard ratio 2.024, P=0.0462). In conclusion, cyclin A is an independent predictor of recurrence of early stage breast cancer and is as such a marker for response in patients treated with tamoxifen.
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PMID:Cyclin A is a prognostic indicator in early stage breast cancer with and without tamoxifen treatment. 1187 7

Most breast cancer patients receive chemotherapy at some phase of their illness but only about half of them benefit from it. Identifying the factors predicting response to chemotherapy would also assist the clinician in selection of appropriate patients for chemotherapy, thus saving others from unnecessary exposure to toxic agents. At the present time, there is no tumour biological factor available for clinical use in the prediction of chemotherapy response in advanced breast cancer apart from oestrogen receptor status, which predicts response to hormonal therapy, or the HER2 receptor, which predicts response to trastuzumab. Interestingly, they both are also targets for those therapies. Several groups have tried to find such predictive factors for chemotherapy in advanced breast cancer but the results are so far disappointing. This review collects the rapidly expanding data published so far on the predictive value of tumour biological factors for chemotherapy response in advanced breast cancer. In conclusion, none of them is yet good enough for clinical use in advanced breast cancer.
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PMID:Predictive factors for response to chemotherapy in advanced breast cancer. 1223 24

Neoadjuvant/pre-surgical medical therapy of breast cancer provides a unique opportunity to derive biological information related to tumour response. Large clinical trials of neoadjuvant chemotherapy have established that pathological complete remission is an independent predictor of improved disease-free survival. Clinical response has been found to parallel substantial reductions in the proliferation of breast cancer cells. Increased apoptosis also occurs, but it is not closely associated with response. Numerous biological markers such as p53, bcl-2, oestrogen receptor (ER) and HER2 have been assessed for their possible role in chemoresistance/response, but the data are not clear at this stage. Continuing work using cDNA microarrays may yield new, more reliable indices of likely response and an improved insight into biological processes related to chemotherapeutic response.
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PMID:The biology of neoadjuvant chemotherapy for breast cancer. 1223 46

The growth dependence of many breast cancers on oestrogen has been exploited therapeutically by oestrogen deprivation, but almost all patients eventually develop resistance largely by unknown mechanisms. Wild-type (WT) MCF-7 cells were cultured in oestrogen-deficient medium for 90 weeks in order to establish a long-term oestrogen-deprived MCF-7 (LTED) which eventually became independent of exogenous oestrogen for growth. After 15 weeks of quiescence (LTED-Q), basal growth rate increased in parallel with increasing oestrogen sensitivity. While 10(-9)M oestradiol (E2) maximally stimulated WT growth, the hypersensitive LTED (LTED-H) were maximally growth stimulated by 10(-13)M E2. By week 50, hypersensitivity was apparently lost and the cells became oestrogen independent (LTED-I), although the pure antioestrogen ICI182780 still inhibited cell growth and reversed the inhibitory effect of 10(-9)M E2 at 10(-12) to 10(-7)M. Tamoxifen (10(-7) to 10(-6)M) had a partial agonist effect on WT, but had no stimulatory effect on LTED. Whilst LTED cells have a low progesterone receptor (PgR) expression in all phases, oestrogen receptor (ER) a expression was, on average, elevated five- and seven-fold in LTED-H and LTED-I, respectively, and serine118 was phosphorylated. ERbeta expression was up-regulated and the levels of insulin receptor substrate 1 (IRS-1) remained low throughout all phases. The levels of RIP140mRNA appeared to decrease to approximately 50% of the WT message in LTED-Q and remained constant into the hypersensitive phase. No significant changes were observed in the expression of SUG-1, TIF-1 and SMRT in LTED. The overall changes in nuclear receptor interacting proteins do not appear to be involved in the hypersensitivity. Thus, the resistance of these human breast cancer cells to oestrogen-deprivation appears to be due to acquired hypersensitivity which may be explained in part by increased levels of and phosphorylated ERalpha.
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PMID:Molecular changes associated with the acquisition of oestrogen hypersensitivity in MCF-7 breast cancer cells on long-term oestrogen deprivation. 1236 23


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