Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A procedure of reversible immortalization of primary cells was devised by retrovirus-mediated transfer of an oncogene that could be subsequently excised by site-specific recombination. This study focused on the early stages of immortalization: global induction of proliferation and life span extension of cell populations. Comparative analysis of Cre/LoxP and FLP/FRT recombination in this system indicated that only Cre/LoxP operates efficiently in primary cells. Pure populations of cells in which the oncogene is permanently excised were obtained, following differential selection of the cells. Cells reverted to their preimmortalized state, as indicated by changes in growth characteristics and p53 levels, and their fate conformed to the telomere hypothesis of replicative cell senescence. By permitting temporary and controlled expansion of primary cell populations without retaining the transferred oncogene, this strategy may facilitate gene therapy manipulations of cells unresponsive to exogenous growth factors and make practical gene targeting by homologous recombination in somatic cells. The combination of retroviral transfer and site-specific recombination should also extend gene expression studies to situations previously inaccessible to experimentation.
 ...
PMID:Reversible immortalization of mammalian cells mediated by retroviral transfer and site-specific recombination. 879 38

The staurosporine derivative PKC412 was originally identified as an inhibitor of protein kinase C (PKC) and subsequently shown to inhibit other kinases including the kinase insert domain receptor (KDR) (vascular endothelial growth factor receptor, VEGF-R2), the receptor of platelet-derived growth factor, and the receptor for the stem cell factor, c-kit. PKC412 showed a broad antiproliferative activity against various tumor and normal cell lines in vitro, and was able to reverse the Pgp-mediated multidrug resistance of tumor cells in vitro. Exposure of cells to PKC412 resulted in a dose-dependent increase in the G2/M phase of the cell cycle concomitant with increased polyploidy, apoptosis and enhanced sensitivity to ionizing radiation. PKC412 displayed a potent antitumor activity as single agent and was able to potentiate the antitumor activity of some of the clinically used cytotoxins (Taxol and doxorubicin) in vivo. The combined treatment of PKC412 with loco-regional ionizing irradiation showed significant antitumor activity against tumors which are resistant to both ionizing radiation and chemotherapeutic agents (dysfunctional p53). The finding that PKC412 is an inhibitor of the VEGF-mediated cellular signaling via inhibition of KDR and PKC in vitro is consistent with the in vivo inhibition of VEGF-dependent angiogenesis in a growth factor implant model. Orally administered PKC412 also strongly inhibited retinal neovascularization as well as laser-induced choroidal neovascularization in murine models. In summary, PKC412 may suppress tumor growth by inhibiting tumor angiogenesis in addition to directly-inhibiting tumor cell proliferation via its effects on PKC and/or other protein kinases. PKC412 is currently in Phase I clinical trials for treatment of advanced cancer as well as for the treatment of ischemic retinopathy.
 ...
PMID:PKC412--a protein kinase inhibitor with a broad therapeutic potential. 1088 33

Vascular endothelial growth factor (VEGF) and its receptors, Flt-1 and flk-1(KDR), constitute an important angiogenic pathway which, under hypoxic conditions, is up-regulated in many solid tumours. We used the monoclonal antibody 11B5, specific for recognizing VEGF expression and the 'VEGF/flk-1(KDR) complex' on tumour endothelium, to assess free VEGF protein expression and VEGF/receptor activated microvessel density (aMVD) in a series of 104 inoperable locally advanced squamous cell carcinomas of the head and neck, treated with chemo-radiotherapy. High VEGF expression in cancer cells was strongly associated with high VEGF/receptor expression in the vasculature. The high VEGF expression and the aMVD were not associated with the standard microvessel density (sMVD), as assessed with the monoclonal antibody anti-CD31 and, were not detected in normal tissue. An increased sMVD, however, was significantly related with the expression thymidine phosphorylase (TP), and also with the nuclear accumulation of the oncoprotein p53, but neither p53 nor TP was associated with VEGF expression by cancer cells or VEGF/receptor complex aMVD. In 35% of cancer cases examined, more than 20% of the microvessels assessed with anti-CD31 also expressed the VEGF/KDR complex. The vasculature of the normal head and neck mucosa did not express the VEGF/KDR complex. There was no association between VEGF expression or VEGF/receptor complex aMVD and response to chemo-radiotherapy or patient's survival. It is concluded that activation of the angiogenic pathway VEGF/flk-1(KDR) is tumor specific in a subgroup of locally advanced squamous cell carcinomas of the head and neck. Selective destruction of this type of vasculature, using immunoconjugates directed against the VEGF/receptor complex, may prove therapeutically useful for patients with a high tumoral VEGF/flk-1(KDR) activated microvessel fraction.
 ...
PMID:Tumor specific activation of the VEGF/KDR angiogenic pathway in a subset of locally advanced squamous cell head and neck carcinomas. 1144 62

Vascular endothelial growth factor (VEGF), an important angiogenic factor, regulates cell proliferation, differentiation, and apoptosis through activation of its tyrosine-kinase receptors, such as Flt-1 and Flk-1/Kdr. Human malignant mesothelioma cells (HMC), which have wild-type p53, express VEGF and exhibit cell growth increased by VEGF. Here, we demonstrate that early transforming proteins of simian virus (SV) 40, large tumor antigen (Tag) and small tumor antigen (tag), which have been associated with mesotheliomas, enhanced HMC proliferation by inducing VEGF expression. SV40-Tag expression potently increased VEGF protein and mRNA levels in several HMC lines. This effect was suppressed by the protein synthesis inhibitor, cycloheximide. Inactivation of the VEGF signal transduction pathway by expression of soluble form of Flt-1 inhibited Flk-1/Kdr activation and HMC proliferation induced by SV40 early genes. Experiments with SV40 mutants revealed that SV40-Tag, but not -tag, is involved in the VEGF promoter activation. However, concomitant expression of SV40-tag enhanced Tag function. In addition, SV40-Tag expression sustained VEGF induction in colon carcinoma cell line (CCL)-233, which have wild-type p53, but not in CCL-238, which lack functional p53. These data indicate that VEGF regulation by SV40 transforming proteins can represent a key event in SV40 signaling relevant for tumor progression.
 ...
PMID:Enhanced expression of vascular endothelial growth factor (VEGF) plays a critical role in the tumor progression potential induced by simian virus 40 large T antigen. 1197 50

The tumour suppressor ING1 shares many biological functions with p53, such as cell cycle arrest, DNA repair, apoptosis, and chemosensitivity. Since p53 inhibits invasion and angiogenesis of melanoma cells, we sought to investigate if p33ING1 (one of ING1 isoforms) is also involved in these biological processes. We first overexpressed p33ING1 in melanoma cells and assessed the protein levels in MMP-1, MMP-2, and MMP-9. Results from Western blot analysis showed no significant difference in these matrix metalloproteinase levels between cells transfected with vector, p33ING1, and antisense p33ING1. Wound healing assay was performed to examine if p33ING1 plays a role in migration and invasion. Results showed that there was no difference between vector, p33ING1, and antisense p33ING1 groups in melanoma cell migration across the wound. Western blot analysis also indicated that there is no difference in the levels of proteins which are directly involved in angiogenesis, such as VEGF, Flt-1, and Flk-1, between cells transfected with vector, p33ING1, and antisense p33ING1. Furthermore, functional studies indicated that cultured medium derived from p33ING1-transfected melanoma cells did not stimulate the growth of HUVEC cells, compared to controls, providing support to the lack of functional role of p33ING1 in angiogenesis. In conclusion, we demonstrate in vitro that p33ING1, unlike p53, does not play a role in angiogenesis and migration in melanoma cells.
 ...
PMID:The tumour suppressor p33ING1 does not regulate migration and angiogenesis in melanoma cells. 1242 89

Papillary thyroid carcinomas (PTC) are the most common thyroid cancers in children. Most are successfully treated with surgery and radioactive iodine, but some persist. PTC express high levels of vascular endothelial growth factor (VEGF) and VEGF receptor (Flt-1). PTC with the most intense expression of VEGF have the greatest recurrence risk. We hypothesized that blockade of VEGF would inhibit PTC growth. To test this, we used systemic VEGF monoclonal antibody (VEGF-MAb) to treat PTC xenografts in nude mice. Treated animals (n = 9) received 200 microg VEGF-MAb by daily i.p. injection for 10 wk, while control animals (n = 9) received vehicle alone. Tumor size was significantly reduced in the treatment group (0.28 +/- 0.06 vs 1.05 +/- 0.25 g, p = 0.008). VEGF immunostaining was more intense (2.57 +/- 0.30 vs 1.75 +/- 0.25, p = 0.06) and the number of p53 positive cells was increased (1.66 +/- 0.24 vs 0.83 +/- 0.31, p = 0.048) in treated tumors. Animal weight was similar in both groups (29.1 +/- 1.1 vs 27.4 +/- 1.1 g, p = 0.30). In conclusion, systemic VEGF-MAb significantly reduced the growth of PTC, suggesting that VEGF-MAb might be useful for treatment of resistant PTC.
 ...
PMID:Systemic administration of vascular endothelial growth factor monoclonal antibody reduces the growth of papillary thyroid carcinoma in a nude mouse model. 1281 24

The VEGF system is essential for angiogenesis. VEGF overexpression frequently correlates with increased microvascularity and metastasis and decreased spontaneous apoptosis. Although a precise mechanism has not been established, studies suggest that VEGF expression is negatively regulated by p53, a master regulator and tumor suppressor. There are no reports of additional components of the VEGF signal transduction pathway being part of the p53 transcriptional network. A target of VEGF, the VEGF receptor 1/flt-1, can regulate growth and migration of endothelial cells and modulate angiogenesis. VEGF appears to be up-regulated in various cancers in which flt-1 may have a role in tumor progression and metastasis. We identified a C-to-T SNP upstream of the transcriptional start site in approximately 6% of the people examined. The SNP is located within a putative p53 response element. Only the promoter with the T SNP (FLT1-T) was responsive to p53 when examined with reporter assays or by endogenous gene expression analysis in cell lines with different SNP status. In response to doxorubicin-induced DNA damage, there was clear allele discrimination based on p53 binding at the FLT1-T but not FLT1-C promoters as well as p53-dependent induction of flt-1 mRNA, which required the presence of FLT1-T. Our results establish that p53 can differentially stimulate transcription at a polymorphic variant of the flt-1 promoter and directly places the VEGF system in the p53 stress-response network via flt-1 in a significant fraction of the human population. We suggest that the p53-VEGF-flt-1 interaction is relevant to risks in angiogenesis-associated diseases, including cancer.
 ...
PMID:A SNP in the flt-1 promoter integrates the VEGF system into the p53 transcriptional network. 1643 14

Age-related macular degeneration is the leading cause of blindness in people over the age of 55. In addition to an increased risk of vision loss due to macular degeneration, aging results in a substantial loss of sympathetic nerve activity. We have previously shown that loss of sympathetic nerve activity to the eye causes significant remodeling of the choroidal vasculature. The hypothesis of the present study was that the choroidal remodeling noted after sympathectomy was due to alterations in key angiogenic growth factors. To test this hypothesis, female Sprague-Dawley rats underwent superior cervical ganglionectomy, which eliminates all sympathetic innervation to the eye. Six weeks after surgery, eyes were removed, and the choroidal tissue was processed for real-time PCR to measure gene expression and western blot analysis to assess protein expression. Gene and protein expression were significantly increased for vascular endothelial growth factor (VEGF) and pigment epithelial-derived growth factor (PEDF) in the sympathectomized eye, as compared to the contralateral eye (P < 0.05). Protein expression was increased 4-fold for angiopoietin1, with no change in steady-state gene expression. For both p53 and placental growth factor, steady-state mRNA levels were significantly decreased, while protein expression was significantly increased. Protein expression for Flt-1 was decreased significantly, with reduced gene expression. These results suggest that the vascular remodeling noted in the choroidal blood vessels after sympathectomy is a complex process involving numerous growth factor families. Therefore, modulation of sympathetic nerve activity may be a suitable mechanism to prevent the vascular growth associated with macular degeneration.
 ...
PMID:Cervical sympathectomy regulates expression of key angiogenic factors in the rat choroid. 1648 69

Paradoxical induction of apoptosis by estrogen has been described previously for estrogen-deprived and antiestrogen-resistant breast cancer cells. In this study we analyzed the possible interrelations between cell sensitization to estrogen apoptotic action and cell ability to (anti)estrogen-independent growth. Using tamoxifen-resistant sublines derived from the parent MCF-7 breast cancer cells by long-term tamoxifen treatment we demonstrated that resistant cells are characterized by increased level of EGF receptor and unexpected increase of VEGF receptor 2 (Flk-1/KDR) and its specific ligand, VEGF-A. The importance of the VEGF signaling in the autocrine regulation of cell growth was indicated by the ability of VEGF inhibitor, soluble fragment of Flt-1/Fc chimera, to suppress the phosphorylation of MAP kinases as well as to inhibit the estrogen-independent growth of MCF-7 cells. Sensitization of tamoxifen-resistant cells to estrogen-induced apoptosis required the additional continuous cultivation in steroid-depleted medium and did not depend on the activity of both EGF and VEGF pathways. Finally, we showed that treatment of the cells with 17beta-estradiol (10(-9) M) resulted in a marked increase in p53 level both in the resistant cells undergoing apoptosis and in the parent MCF-7 cells insensitive to apoptotic estrogen action. These data provide an important support for the existence of a disbalance between pro- and anti-apoptotic machinery in the resistant breast cancer cells that forms independently of the acquired ability to estrogen-independent growth.
 ...
PMID:Activation of mitogenic pathways and sensitization to estrogen-induced apoptosis: two independent characteristics of tamoxifen-resistant breast cancer cells? 1699 Sep 91

Interactions between master regulatory pathways provide higher-order controls for cellular regulation. Recently, we reported a C-->T single-nucleotide polymorphism (SNP) in the vascular endothelial growth factor receptor 1 (VEGFR-1/Flt1) promoter that merges human VEGF and p53 pathways. This finding suggested a new layer in environmental controls of a pathway relevant to several diseases. The Flt1-T SNP created what appeared to be a half-site p53 target response element (RE). The absence of information about p53 gene responsiveness mediated by half-site REs led us to address how it influences Flt1 expression. We now identify a second regulatory sequence comprising a partial RE for estrogen receptors (ERs) upstream of the p53 binding site. Surprisingly, this provides for synergistic stimulation of transcription specifically at the Flt1-T allele through the combined action of ligand-bound ER and stress-induced p53. In addition to demonstrating direct control of Flt1 expression by ER and p53 proteins acting as sequence-specific transcription factors at half-site REs, we establish a new interaction between three master regulatory pathways, p53, ER, and VEGF. The mechanism of joint regulation through half-sites is likely relevant to transcriptional control of other targets and expands the number of genes that may be directly controlled in master regulatory networks.
 ...
PMID:A single-nucleotide polymorphism in a half-binding site creates p53 and estrogen receptor control of vascular endothelial growth factor receptor 1. 1724 90


1 2 3 4 Next >>