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L Hughes-Davies

Publications and source records attributed to L Hughes-Davies.

18 recordsLinked to original sources
PubMed2001

Inhibiting mutations in the transforming growth factor beta type 2 receptor in recurrent human breast cancer.

Members of the transforming growth factor beta (TGF-beta) family are potent inhibitors of the growth of many epithelial cell types. Transmembrane signaling by TGF-beta occurs via a complex of the serine/threonine kinases TGF-beta type 1 receptor and TGF-beta type 2 receptor (TGFBR2), and inactivating mutations in the latter have recently been detected in some primary tumors and in several types of tumor-derived cell lines. The most common mutations that have been identified in TGFBR2 are frameshifts in a repetitive polyadenine region in replication error-positive colorectal carcinomas that result in a truncated protein and absence of receptor expression at the cell surface. A number of point mutations in the highly conserved serine/threonine kinase domain of TGFBR2 have also been reported, some of which have been correlated with either loss of trans-phosphorylation of TGF-beta type 1 receptor or constitutive activation of trans-phosphorylation. No TGFBR2 mutations have been reported in human breast tumors, but anomalous expression of TGF-beta in breast carcinomas suggests that TGF-beta signaling may be defective. We have therefore systematically examined unmatched sets of 17 primary and 17 recurrent breast tumor samples for mutations in TGFBR2, restricted to those regions of the gene in which mutations have previously been reported. None of the previously reported mutations was detected, but four novel mutations (V387M, N435S, V447A, and L452M) were found in the kinase domain in recurrent tumors. No mutations were detected in primary tumors. TGF-beta signaling was significantly inhibited by each of the N435S, V447A, and L452M mutations.

Animals↗
PubMed2000

The BRCA2 activation domain associates with and is phosphorylated by a cellular protein kinase.

A substantial proportion of familial breast cancers have mutations within the BRCA2 gene. The product of this gene has been implicated in DNA repair and in the regulation of transcription. We have previously identified at the amino-terminus of BRCA2 a transcriptional activation domain whose importance is highlighted by the presence of predisposing mutations and in-frame deletions in breast cancer families. This activation domain shows sequence similarity to a region of c-Jun which has been defined as a binding site for the c-Jun N-terminal kinase. Here, we show that the analogous region in BRCA2 is also a binding site for a cellular kinase, although this kinase is distinct from JNK. The BRCA2 associated enzyme is able to phosphorylate residues within the BRCA2 activation domain. Consistent with this observation, we find that the activation domain of BRCA2 is phosphorylated in vivo. Our results indicate that the BRCA2 activation domain possesses a binding site for a kinase that may regulate BRCA2 activity by phosphorylation.

Amino Acid Sequence↗
PubMed2000

DNA methyltransferase Dnmt1 associates with histone deacetylase activity.

The DNA methyltransferase Dnmt1 is responsible for cytosine methylation in mammals and has a role in gene silencing. DNA methylation represses genes partly by recruitment of the methyl-CpG-binding protein MeCP2, which in turn recruits a histone deacetylase activity. Here we show that Dnmt1 is itself associated with histone deacetylase activity in vivo. Consistent with this association, we find that one of the known histone deacetylases, HDAC1, has the ability to bind Dnmt1 and can purify methyltransferase activity from nuclear extracts. We have identified a transcriptional repression domain in Dnmt1 that functions, at least partly, by recruiting histone deacetylase activity and shows homology to the repressor domain of the trithorax-related protein HRX (also known as MLL and ALL-1). Our data show a more direct connection between DNA methylation and histone deacetylation than was previously considered. We suggest that the process of DNA methylation, mediated by Dnmt1, may depend on or generate an altered chromatin state via histone deacetylase activity.

Animals↗
PubMed1997

Stage IA-IIB Hodgkin's disease: management and outcome of extensive thoracic involvement.

PURPOSE: To examine the presentation, management, and outcome of patients with extensive intrathoracic involvement in early-stage Hodgkin's disease. PATIENTS AND METHODS: One hundred seventy-two patients with clinical Stage IA-IIB Hodgkin's disease and extensive intrathoracic involvement were studied. Extensive intrathoracic disease was defined as either large mediastinal adenopathy (LMA, defined as the width of the mass greater than one-third the maximum thoracic diameter, n = 154) or as extensive (> 10 cm) cephalocaudad intrathoracic disease that did not fulfill formal chest radiograph criteria for LMA (n = 18). Patients were divided into three groups based on staging and extent of treatment. Forty-seven patients were treated with radiation alone after a laparotomy (RT-lap), 47 patients received combined modality therapy after laparotomy (CMT-lap), and 78 patients were treated with combined modality therapy without staging laparotomy (CMT-no lap). MOPP was used in 82% of the CMT patients. Low-dose whole-cardiac RT was used in nearly 50% of patients treated either with RT or CMT. RESULTS: The 10-year actuarial freedom from relapse rates were 54% with RT alone and 88% with CMT (p = 0.001); overall survival rates were 84 and 89%, respectively (p = NS). The median time to relapse was only 17 months. Over 80% of relapses occurred within the first 3 years. The most common site of relapse in all patients was the mediastinum. Relapses below the diaphragm were rare, even in CMT patients who did not receive abdominal radiation treatment. The principal acute morbidity was symptomatic pneumonitis, which occurred in 29% of patients receiving any part of their chemotherapy after RT, compared to 13% if all the chemotherapy was given before RT and 11% if RT alone was administered. There was a low late risk of myocardial infarction (3%) in the two groups with the longest follow up (RT-lap, CMT-lap), but a higher risk of second malignancy in the CMT-lap group (21%) compared with the RT-lap group (2%). CONCLUSION: Extensive intrathoracic involvement is a distinctive presentation of early-stage HD that has a high relapse risk if treated with RT alone. The introduction of CMT has been associated with improvements in freedom from relapse. The low rate of peripheral relapse with CMT suggests that reductions in field size may be achievable. The use of low-dose whole-heart RT with modern techniques is not associated with a high risk of late cardiac complications and should be used in patients who present with extensive pericardial disease or cardiophrenic lymphadenopathy. The high rate of second malignancy in the CMT group with the longest follow-up suggests that careful long-term surveillance for such patients is warranted.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

Suramin increases p53 protein levels but does not activate the p53-dependent G1 checkpoint.

Suramin is an antineoplastic agent which has a cytostatic effect on both normal and tumor-derived cells. We have investigated whether the induction of growth arrest by suramin requires the p53 protein, a tumor suppressor gene product involved in the initiation of growth arrest following DNA damage. Activation of the p53 protein by genotoxic agents causes increased p53 protein levels and p53-dependent transcription of the p21 gene. The p21 protein then inhibits cyclin-dependent kinases, initiating G1 arrest. Exposure of NIH-3T3 cells to suramin caused a rapid (1-2 h) increase in the level of p53-DNA-binding activity. Flow cytometric analysis indicated that suramin arrested NIH-3T3 cells in G0-G1. However, suramin did not increase the p53-dependent transcription of the p21 gene or inhibit cyclin-dependent kinase 2 kinase activity. If NIH-3T3 cells were exposed to radiation or suramin plus radiation, p21 mRNA levels were increased and cyclin-dependent kinase 2 kinase activity was inhibited, indicating that suramin does not block the cells' ability to increase p21 levels. To determine whether the G0-G1 arrest induced by suramin required p53, NIH-3T3 cells transfected with a dominant negative mutant p53 gene to eliminate wild-type p53 function (NMP cells) were exposed to suramin. NMP cells still exhibited G0-G1 arrest after suramin treatment. Suramin increases p53 protein levels, but fails to increase p21 mRNA levels or to activate the G1 checkpoint. These data suggest that suramin induces growth arrest in NIH-3T3 cells by a mechanism that is independent of cellular p53 status.

3T3 Cells↗
PubMed1995

Cdk2 kinase phosphorylates serine 315 of human p53 in vitro.

DNA damage increases p53 protein levels and activates transcription of the p21 gene. The p21 protein binds to and inhibits cdk2 kinase, causing G1 arrest. Here, we have investigated if a p53 fusion protein is a substrate for cdk2 kinase in vitro. Cdk2 kinase was immunoprecipitated from NIH3T3 cells and allowed to phosphorylate a human p53-GST (glutathione-s-transferase) fusion protein. Cdk2 and cyclin E-cdk2 efficiently phosphorylated both wild-type (wt) and mutant p53-GST. Cdk2 immunoprecipitated from cells in Go and early G1 exhibited minimal p53 kinase activity, whereas cells in S-phase displayed high levels of p53 kinase activity. If NIH3T3 cells were X-ray irradiated to induce DNA damage, cdk2 p53 kinase activity was rapidly inhibited within 1 h, but had recovered by 4 h post irradiation. Mutation of serine 315 of p53 to alanine (p53-S315A) abolished phosphorylation by cdk2 kinase. However, wtp53 and p53-S315A were equally effective at activating transcription when cotransfected with a p53 reporter construct. The results demonstrate that ser 315 of p53 is phosphorylated by cdk2 in vitro. However, ser 315 of wtp53 is not required for transcriptional activity in vivo, suggesting that cdk2 phosphorylation of p53 may be involved in regulating other cellular functions of wtp53.

3T3 Cells↗
PubMed1995

Parametrial interstitial brachytherapy for advanced or recurrent pelvic malignancy: the Harvard/Stanford experience.

In this study we evaluate the long-term efficacy and safety of transperineal interstitial implants for advanced pelvic malignancy. A total of 139 patients were treated at Stanford University Medical Center and the Joint Center for Radiation Therapy with transperineal template interstitial brachytherapy for locally advanced or recurrent cancers arising in the pelvic organs. Most patients received whole pelvis external beam irradiation to a median dose of 4200 cGy followed by an implant for a median duration of 48 hr to a median implant dose of 3000 cGy (range 600-6000 cGy). Complete follow-up was obtained for 91% of the patients. Median follow-up for survivors is 57 months (range, 10-173 months). The crude disease-free survival rate was 22% at 5 years. The 5-year crude local tumor control rate was 25%. No dose-response relationship could be demonstrated for tumor control or complications. There were no acute treatment-related deaths. Three late deaths were seen which were directly related to treatment. Major bowel complications requiring surgery were seen in 17% of patients without locally recurrent disease, and fistulas were reported in 4% of these patients. We conclude that template parametrial implant brachytherapy offers a modest chance of cure for women with locally advanced pelvic malignancy. However, this treatment causes significant late morbidity.

Adolescent↗
PubMed1995

Serum cardiac troponin T levels during treatment of early-stage breast cancer.

PURPOSE: To measure serum troponin T concentrations in patients with early-stage left breast cancer during breast-conserving radiation therapy. Troponin T has been introduced recently as a sensitive and specific marker for acute myocardial injury. PATIENTS AND METHODS: We compared pretreatment and posttreatment serum troponin T values in 50 patients undergoing radiation therapy to the entire left breast following conservative surgery for stage I and II breast cancer. RESULTS: No changes in troponin T concentrations were found after 45 to 46 Gy whole-breast irradiation. All women had undetectable or normal troponin T on the first and last day of treatment. There was no evidence of an upward trend during treatment. CONCLUSION: Radiation therapy to the left breast does not affect serum cardiac troponin T levels, despite the fact that a portion of the myocardium lies within the high-dose region. This suggests that the acute effects of radiation on the myocardium are minor. Long-term evaluation of these patients is necessary to rule out the possibility of late cardiac morbidity due to accelerated atherosclerosis. This study also suggests that an elevated troponin T level during or shortly after left breast irradiation should not be attributed to treatment.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1992

Occult alveolar haemorrhage in bronchopulmonary Kaposi's sarcoma.

Evidence of occult alveolar haemorrhage was sought by Perls's staining of bronchoalveolar lavage fluid to detect haemosiderin laden macrophages in 63 human immunodeficiency virus positive (HIV-1) men who underwent bronchoscopy. Twenty three patients had bronchopulmonary Kaposi's sarcoma; occult alveolar haemorrhage was present in 16 of these (including two in whom no tracheobronchial lesions were evident at bronchoscopy, but in whom the diagnosis was confirmed at necropsy). Forty patients had other diagnoses including Pneumocystis carinii pneumonia and bacterial pneumonia; 18 had occult haemorrhage. Occult alveolar haemorrhage seems to be a non-specific finding in HIV-1 positive men undergoing bronchoscopy.

Adult↗