PubMed Health⌕ Search

Biomedical subjects

Robert Brown

Publications and source records attributed to Robert Brown.

At least 19 recordsLinked to original sources

Epigenetic inactivation of MCJ (DNAJD1) in malignant paediatric brain tumours.

MCJ (DNAJD1) is a recently discovered member of the DNAJ protein family whose expression is controlled epigenetically by methylation of a CpG island located within the 5' transcribed region of its gene. Methylation-dependent transcriptional silencing of MCJ has been observed in ovarian cancers and associated with increased resistance to chemotherapeutic agents; however, its role in other cancer types has not been widely investigated. We examined the status of MCJ in intracranial primitive neuroectodermal tumours [PNETs, comprising cerebellar PNETs (medulloblastomas) and supratentorial PNETs (stPNETs)] and ependymomas, together representing the most common malignant brain tumours of childhood. Evidence of MCJ hypermethylation was found in all 3 tumour types [medulloblastomas, 3/9 (33%) cell lines, 2/28 (7%) primary tumours; stPNETs, 2/2 (100%) cell lines, 3/10 (30%) primary tumours; and ependymomas, 2/20 (10%) primary tumours] but not in nonneoplastic brain tissues (n = 11), indicating that MCJ methylation is a tumour-specific event. In methylated cases, the distribution of methylated CpG sites across the CpG island could be broadly divided into 2 patterns: (i) extensive methylation of the majority of CpG sites across the island or (ii) limited methylation of individual CpG sites concentrated towards the 5' end of the island. Extensive methylation patterns were associated with the methylation-dependent transcriptional silencing of MCJ in medulloblastoma and stPNET cell lines. Further investigations of the mechanism of MCJ inactivation revealed that its loss could occur either through biallelic epigenetic methylation or by methylation in association with genetic loss of its second allele. These data indicate that epigenetic inactivation of MCJ may play a role in the development of a range of paediatric brain tumour types, and its role in disease pathogenesis and chemotherapeutic resistance should now be investigated further.

Adolescent↗

Development of nonsymmetrical 1,4-disubstituted anthraquinones that are potently active against cisplatin-resistant ovarian cancer cells.

A novel series of 1,4-disubstituted aminoanthraquinones were prepared by ipso-displacement of 1,4-difluoro-5,8-dihydroxyanthraquinones by hydroxylated piperidinyl- or pyrrolidinylalkylamino side chains. One aminoanthraquinone (13) was further derivatized to a chloropropylamino analogue by treatment with triphenylphosphine-carbon tetrachloride. The compounds were evaluated in the A2780 ovarian cancer cell line and its cisplatin-resistant variants (A2780/cp70 and A2780/MCP1). The novel anthraquinones were shown to possess up to 5-fold increased potency against the cisplatin-resistant cells compared to the wild-type cells. Growth curve analysis of the hydroxyethylaminoanthraquinone 8 in the osteosarcoma cell line U-2 OS showed that the cell cycle is not frozen, rather there is a late cell cycle arrest consistent with the action of a DNA-damaging topoisomerase II inhibitor. Accumulative apoptotic events, using time lapse photography, indicate that 8 is capable of fully engaging cell cycle arrest pathways in G2 in the absence of early apoptotic commitment. 8 and its chloropropyl analogue 13 retained significant activity against human A2780/cp70 xenografted tumors in mice.

Animals↗

DNA methyltransferase inhibitors and the development of epigenetic cancer therapies.

Epimutations, such as the hypermethylation and epigenetic silencing of tumor suppressor genes, play a role in the etiology of human cancers. In contrast to DNA mutations, which are passively inherited through DNA replication, epimutations must be actively maintained because they are reversible. In fact, the reversibility of epimutations by small-molecule inhibitors provides the foundation for the use of such inhibitors in novel cancer therapy strategies. Among the compounds that inhibit epigenetic processes, the most extensively studied are DNA methyltransferase inhibitors. In this review, we examine the literature on DNA methyltransferase inhibitors and discuss the efficacy of such compounds as antitumor agents, as evaluated in phase I-III clinical trials. We also discuss future areas of research, including the development of nonnucleoside inhibitors, the application of novel bioanalytical tools for DNA methylation analysis (which will be important for the clinical application of these compounds by allowing rational approaches to trial design), the need to optimize treatment schedules for maximal biologic effectiveness, and the need to define molecular endpoints so that changes induced by demethylating drugs in patients can be monitored during treatment. Assays for genome-wide and tumor-specific DNA methylation also need to be further developed to establish the pharmacodynamic parameters of DNA methyltransferase inhibitors in patients and to provide rational approaches to maximizing the therapeutic efficacy of these compounds.

Animals↗

Hypermethylation of 18S and 28S ribosomal DNAs predicts progression-free survival in patients with ovarian cancer.

PURPOSE: Repetitive ribosomal DNA (rDNA) genes are GC-rich clusters in the human genome. The aim of the study was to determine the methylation status of two rDNA subunits, the 18S and 28S genes, in ovarian tumors and to correlate methylation levels with clinicopathologic features in a cohort of ovarian cancer patients. EXPERIMENTAL DESIGN: 18S and 28S rDNA methylation was examined by quantitative methylation-specific PCR in 74 late-stage ovarian cancers, 9 histologically uninvolved, and 11 normal ovarian surface epithelial samples. In addition, methylation and gene expression levels of 18S and 28S rDNAs in two ovarian cancer cell lines were examined by reverse transcription-PCR before and after treatment with the demethylating drug 5'-aza-2'-deoxycytidine. RESULTS: The methylation level (amount of methylated rDNA/beta-actin) of 18S and 28S rDNAs was significantly higher (P < 0.05) in tumors than in normal ovarian surface epithelial samples. Methylation of 18S and 28S rDNA was highly correlated (R2= 0.842). Multivariate analysis by Cox regression found that rDNA hypermethylation [hazard ratio (HR), 0.25; P < 0.01], but not age (HR, 1.29; P = 0.291) and stage (HR, 1.09; P = 0.709), was independently associated with longer progression-free survival. In ovarian cancer cell lines, methylation levels of rDNA correlated with gene down-regulation and 5'-aza-2'-deoxycytidine treatment resulted in a moderate increase in 18S and 28S rDNA gene expressions. CONCLUSION: This is the first report of rDNA hypermethylation in ovarian tumors. Furthermore, rDNA methylation levels were higher in patients with long progression-free survival versus patients with short survival. Thus, rDNA methylation as a prognostic marker in ovarian cancer warrants further investigation.

Adult↗

CpG island methylation of DNA damage response genes in advanced ovarian cancer.

We have determined the methylation frequencies of 24 CpG islands of genes associated with DNA damage responses or with ovarian cancer in 106 stage III/IV epithelial ovarian tumors. We have analyzed this data for whether there is evidence of a CpG island methylator phenotype or associations of CpG island methylation with response to chemotherapy in advanced ovarian cancer. Frequent methylation was observed for OPCML, DCR1, RASSF1A, HIC1, BRCA1, and MINT25 (33.3%, 30.7%, 26.4%, 17.3%, 12.3%, and 12.0%, respectively), whereas no methylation was observed for APAF-1, DAPK, FANCF, FAS, P14, P21, P73, SOCS-3, and SURVIVIN. The remaining genes showed only a low frequency of methylation, <10%. Unsupervised gene shaving identified a nonrandom pattern of methylation for OPCML, DCR1, RASSF1A, MINT25, HIC1, and SFRP1, supporting the concept of concordant methylation of these genes in ovarian cancer. Methylation of at least one of the group of genes involved in DNA repair/drug detoxification (BRCA1, GSTP1, and MGMT) was associated with improved response to chemotherapy (P = 0.013). We have examined the frequency of a polymorphism in the DNA methyltransferase gene DNMT3b6, which has been previously reported to affect gene transcription and cancer risk. The genetic polymorphism in the DNMT3b6 gene promoter (at position -149) is not significantly associated with the concordant methylation observed, but is weakly associated with the overall frequency of methylation at the genes examined (P = 0.04, n = 56). This supports the hypothesis that genetic factors affecting function of DNMT genes may underlie the propensity of tumors to acquire aberrant CpG island methylation.

Adult↗

Multi-organ transplantation: is there a protective effect against acute and chronic rejection?

BACKGROUND: Heart-lung transplantation (Tx) is known to offer a protective effect against acute cardiac rejection. This study was undertaken to evaluate acute and chronic heart and/or lung rejection in the setting of multiple-transplanted organs from the same donor compared with single-organ transplantation. METHODS: Acute (treated rejection episodes of heart or lungs) and chronic (allograft vasculopathy in hearts and bronchiolitis obliterans syndrome [BOS] in lungs) rejection events were analyzed in 348 heart transplant (H) recipients, 24 heart-lung (HL) recipients, 82 double-lung (L) recipients and 8 heart-kidney (HK) recipients >18 years of age, who were transplanted between 1990 and 2002. RESULTS: Survival at 3 years differed among groups as follows: HK, 100%; H, 82%; HL, 74%; and L, 70%. The probability of acute rejection within the first 3 months was higher in H recipients than in HL (81% vs 22%; p < 0.0001) or HK (81% vs 12%; p = 0.00009) recipients. Acute cardiac rejection occurred more frequently during the first 2 years in isolated H recipients compared with HL (2.8 vs 0.27 episodes; p < 0.0001) and HK (2.8 vs 0.54; p < 0.001) recipients. Acute lung rejection occurred more frequently in the first 2 years in L than HL (2.4 vs 1.0 episodes; p = 0.02) recipients. Chronic cardiac rejection (allograft vasculopathy) was more likely within 3 years after H compared with HL (32% vs 16%; p = 0.04) or HK (32% vs 0%; p = 0.14). The onset of chronic lung rejection (BOS) within 3 years was similar in HL and L recipients (39% vs 40%; p = 0.9). CONCLUSIONS: Recipients of multiple organs from a single donor undergo less acute rejection of the heart or lungs compared with isolated heart or lung transplant recipients. Cardiac allograft vasculopathy is decreased significantly when cardiac transplantation is combined with a lung allograft. A lower incidence of cardiac allograft vasculopathy is observed when cardiac transplantation is combined with a renal allograft, and may prove statistically significant when more cases have been accumulated. These phenomena may result from immune modulation of the recipient by simultaneous transplant of disparate tissues or introduction of immune-modulating hematopoietic elements.

Acute Disease↗

Highly stable phenanthridinium frameworks as a new class of tunable DNA binding agents with cytotoxic properties.

A new class of cytotoxic heteroaromatic cations is presented, based on the dihydro-imidazo-phenanthridinium framework (DIP), that have affinity for DNA and cytotoxicity toward cancerous cells. The DIP framework is particularly tunable due to the flexible synthetic methodology. Furthermore, the central moiety has proved to be very stable to hydrolysis and reduction compared to other phenanthridinium-based agents.

Antineoplastic Agents↗

Multiple markers for melanoma progression regulated by DNA methylation: insights from transcriptomic studies.

The incidence of melanoma is increasing rapidly, with advanced lesions generally failing to respond to conventional chemotherapy. Here, we utilized DNA microarray-based gene expression profiling techniques to identify molecular determinants of melanoma progression within a unique panel of isogenic human melanoma cell lines. When a poorly tumorigenic cell line, derived from an early melanoma, was compared with two increasingly aggressive derivative cell lines, the expression of 66 genes was significantly changed. A similar pattern of differential gene expression was found with an independently derived metastatic cell line. We further examined these melanoma progression-associated genes via use of a tailored TaqMan Low Density Array (LDA), representing the majority of genes within our cohort of interest. Considerable concordance was seen between the transcriptomic profiles determined by DNA microarray and TaqMan LDA approaches. A range of novel markers were identified that correlated here with melanoma progression. Most notable was TSPY, a Y chromosome-specific gene that displayed extensive down-regulation in expression between the parental and derivative cell lines. Examination of a putative CpG island within the TSPY gene demonstrated that this region was hypermethylated in the derivative cell lines, as well as metastatic melanomas from male patients. Moreover, treatment of the derivative cell lines with the DNA methyltransferase inhibitor, 2'-deoxy-5-azacytidine (DAC), restored expression of the TSPY gene to levels comparable with that found in the parental cells. Additional DNA microarray studies uncovered a subset of 13 genes from the above-mentioned 66 gene cohort that displayed re-activation of expression following DAC treatment, including TSPY, CYBA and MT2A. DAC suppressed tumor cell growth in vitro. Moreover, systemic treatment of mice with DAC attenuated growth of melanoma xenografts, with consequent re-expression of TSPY mRNA. Overall, our data support the hypothesis that multiple genes are targeted, either directly or indirectly, by DNA hypermethylation during melanoma progression.

Animals↗

Mechanical signals and IGF-I gene splicing in vitro in relation to development of skeletal muscle.

It has been shown that the insulin-like growth factor (IGF-I) gene is spliced in response to mechanical signals producing forms of IGF-I which have different actions. In order to study how mechanical signals influence this gene splicing in developing muscle, C2C12 cells were grown in three-dimensional (3D) culture and subjected to different regimens of mechanical strain. IGF-IEa which initiates the fusion of myoblasts to form myotubes was found to be constitutively expressed in myoblasts and myotubes (held under endogenous tension) and its expression upregulated by a single ramp stretch of 1-h duration but reduced by repeated cyclical stretch. In contrast, mechano growth factor (MGF), which is involved in the proliferation of mononucleated myoblasts that are required for secondary myotube formation and to establish the muscle satellite (stem) cell pool, showed no significant constitutive expression in static cultures, but was upregulated by a single ramp stretch and by cycling loading. The latter types of force simulate those generated in myoblasts by the first contractions of myotubes. These data indicate the importance of seeking to understand the physiological signals that determine the ratios of splice variants of some growth factor/tissue factor genes in the early stages of development of skeletal muscle.

Alternative Splicing↗

Dyspnea during daily activities in chronic spinal cord injury.

OBJECTIVE: To assess factors associated with breathlessness in chronic spinal cord injury (SCI) during daily activities. DESIGN: Cross-sectional survey. SETTINGS: Veterans Affairs SCI service and the community. PARTICIPANTS: Four hundred forty-one participants 1 or more years post-SCI, and without acute illness, were recruited between 1994 and 2003 and were categorized according to their ability to walk unassisted, walk with an aid, or to move about by either hand-propelled wheelchair or motorized wheelchair (MWC). INTERVENTIONS: Assessment of injury extent, respiratory symptoms, cigarette smoking, comorbid medical conditions, and spirometry. MAIN OUTCOME MEASURES: Breathlessness during talking, eating, or dressing. RESULTS: Breathlessness was more common in MWC users (20/85 users, 24%) than in nonusers (20/356, 6%). The main activity associated with breathlessness in 15 MWC users was talking (18%). In MWC users, the risk of breathlessness was related to lifetime cigarette smoking (odds ratio [OR]=1.02; 95% confidence interval [CI], 1.00-1.03 per pack year), and reports of chronic cough (OR=7.8; 95% CI, 2.0-32.7), and wheeze (OR=3.5; 95% CI, 1.04-13.6). SCI level, percentage of predicted forced vital capacity and forced expiratory volume in 1 second, and maximal inspiratory pressures were not related to breathlessness. CONCLUSIONS: Breathlessness during selected daily activities (most commonly talking) was greatest in SCI participants who were most impaired with regard to mobility and was associated with reports of coughing, wheezing, and cigarette smoking.

Activities of Daily Living↗

The case for selective re-issuance of medical certificates to allow pilots who have received a heart transplant to resume flying.

BACKGROUND: Cardiac transplant recipients have been regarded as not medically fit to fly an airplane. Recently, the Federal Aviation Administration decided to re-examine this policy and, in response, this study was undertaken to determine the risk of death from any cause and sudden-onset death in heart transplant recipients during the 12 months after an annual evaluation. METHODS: Of 6,510 patients undergoing primary orthotopic cardiac transplantation enrolled in the Cardiac Transplant Research Database (CTRD), 4,978 patients survived for at least 1 year and formed the basis of this study. Risk factors for death from any causes and sudden-onset death (a composite of causes of death that could conceivably result in a pilot's incapacitation) were determined during the 12-month period after an anniversary evaluation. Patients were re-entered into the analysis at each evaluation, resulting in a total of 23,575 anniversary evaluations. RESULTS: The presence of coronary allograft vasculopathy (CAV), left ventricular systolic dysfunction, history of rejection, malignancy, infection and pre-transplant insulin-dependent diabetes were associated with an increased risk of death from any cause and sudden-onset death during the 12-month period after an evaluation. Based on the absence of these risk factors, a group of heart transplant recipients could be defined with a 12-month risk of death from any cause of 1.0% and of sudden-onset death of 0.3% (which is identical to the mortality rate of a matched population from the U.S. life-table). CONCLUSION: Using these identified risk factors, a group of heart transplant recipients can be defined that are potentially medically certifiable to fly without compromising aviation safety.

Adolescent↗

Demethylation of the MCJ gene in stage III/IV epithelial ovarian cancer and response to chemotherapy.

OBJECTIVE: Methylation of a CpG island within the Methylation controlled DNAJ (MCJ) gene results in loss of expression in normal and neoplastic cells. Normal ovarian surface epithelial cells are methylated at the MCJ CpG island and do not express the MCJ gene. Furthermore, re-expression of the MCJ gene, in ovarian cancer cell lines, has been correlated with increased sensitivity to several important chemotherapeutic drugs. The objective of this study was to determine the extent of MCJ promoter methylation in epithelial ovarian cancer patients and address the possible role of MCJ methylation levels in response to chemotherapy in ovarian cancer patients. METHODS: The methylation status of 35 CpG sites within the MCJ CpG island was determined by sequencing of sodium bisulfite modified tumor DNA in 41 patients with stage III/IV epithelial ovarian tumors. Levels of methylation of the MCJ CpG island were then compared with response to therapy and overall survival in the patients. RESULTS: The analysis identified frequent loss of MCJ methylation in ovarian tumors, with only a subset retaining high methylation levels. While 93% (38/41) of tumors examined showed some level of MCJ methylation, only 17% (7/41) retained very high levels (>90% methylation). The presence of such high levels of CpG island methylation correlated significantly with poor response of patients' tumors to therapy (P = 0.027) and poor overall survival (P = 0.023, hazard ratio = 2.9). CONCLUSIONS: These results suggest that MCJ methylation may be useful as a marker of response to chemotherapy in ovarian cancer and are consistent with previous in vitro data linking loss of MCJ expression with drug resistance.

Base Sequence↗

Bilateral oculosympathetic paresis associated with loss of nocturnal melatonin secretion in patients with spinal cord injury.

BACKGROUND: Lesions along the sympathetic pathway to the eye produce oculosympathetic paresis (OSP, Horner's syndrome). The oculosympathetic pathway descends from the hypothalamus through the cervical spinal cord and ascends to the superior cervical ganglion (SCG), which innervates sympathetic targets in the ipsilateral face and eye. This pathway appears to closely co-localize with a similar retino-pineal neural pathway from the hypothalamus through the cervical spinal cord and SCG to the pineal gland. As such, lesions along this shared pathway, such as occur in neurologically complete injury to the cervical spinal cord (tetraplegia), would be predicted to result in simultaneous OSP and loss of pineal melatonin production. Loss of melatonin production may contribute to the pervasive sleep disruption observed in patients with tetraplegia. METHODS: We assessed the presence of OSP by photographic documentation of ptosis and pupillary dilation response to cocaine eye drops in 5 individuals with neurologically complete damage to their upper thoracic or lower cervical spinal cord. We correlated these results with an analysis of the pattern of melatonin production in these same individuals. RESULTS: Bilateral OSP was present in individuals with cervical spinal cord injury; each also lacked significant production of melatonin. No evidence of OSP was observed in the 2 individuals with thoracic spinal cord injury below the level of the oculosympathetic pathway. Both had normal circadian rhythms of melatonin production, with timing and amplitude of the rhythm within normal parameters. CONCLUSION: The presence of bilateral oculosympathetic paresis can be predictive of the complete loss of the nocturnal production of melatonin.

Adult↗

Utilization of extended donor criteria liver allografts maximizes donor use and patient access to liver transplantation.

OBJECTIVE: The objective of this study was to evaluate the effect of systematic utilization of extended donor criteria liver allografts (EDC), including living donor allografts (LDLT), on patient access to liver transplantation (LTX). SUMMARY BACKGROUND DATA: Utilization of liver allografts that do not meet traditional donor criteria (EDC) offer immediate expansion of the donor pool. EDC are typically allocated by transplant center rather than regional wait-list priority (RA). This single-institution series compares outcomes of EDC and RA allocation to determine the impact of EDC utilization on donor use and patient access to LTX. METHODS: The authors conducted a retrospective analysis of 99 EDC recipients (49 deceased donor, 50 LDLT) and 116 RA recipients from April 2001 through April 2004. Deceased-donor EDC included: age >65 years, donation after cardiac death, positive viral serology (hepatitis C, hepatitis B core antibody, human T-cell lymphotrophic), split-liver, hypernatremia, prior carcinoma, steatosis, and behavioral high-risk donors. Outcome variables included patient and graft survival, hospitalization, initial graft function, and complication categorized as: biliary, vascular, wound, and other. RESULTS: EDC recipients were more frequently diagnosed with hepatitis C virus or hepatocellular carcinoma and had a lower model for end-stage liver disease (MELD) score at LTX (P < 0.01). Wait-time, technical complications, and hospitalization were comparable. Log-rank analysis of Kaplan-Meier survival estimates demonstrated no difference in patient or graft survival; however, deaths among deceased-donor EDC recipients were frequently the result of patient comorbidities, whereas LDLT and RA deaths resulted from graft failure (P < 0.01). EDC increased patient access to LTX by 77% and reduced pre-LTX mortality by over 50% compared with regional data (P < 0.01). CONCLUSION: Systematic EDC utilization maximizes donor use, increases access to LTX, and significantly reduces wait-list mortality by providing satisfactory outcomes to select recipients.

Adolescent↗

The impact of pre-operative loco-regional therapy on outcome after liver transplantation for hepatocellular carcinoma.

No prior studies have shown that pre-operative loco-regional therapy for hepatocellular carcinoma (HCC) improves survival following orthotopic liver transplantation (OLT). We performed subgroup analyses according to pathologic HCC stage among 168 patients who underwent OLT to test the hypothesis that pre-operative loco-regional therapy confers a survival advantage in a subgroup at intermediate risk for HCC recurrence. Patients with pathologic T3 HCC meeting the proposed UCSF expanded criteria (single lesion not exceeding 6.5 cm or two to three lesions none > 4.5 cm with total tumor diameter within 8 cm) had a similar 5-year recurrence-free survival as patients with pathologic T2 HCC (88.5% vs. 93.8%; p = 0.56). In the subgroup with pathologic T2 or T3 HCC, the 5-year recurrence-free survival was 93.8% for the 85 patients who received pre-operative loco-regional therapy, versus 80.6% for the other 41 patients without treatment (p = 0.049). The treatment benefit, according to 5-year recurrence-free survival, appeared greater for pathologic T3 (85.9% vs. 51.4%; p = 0.05) than T2 HCC (96.4% versus 87.1%; p = 0.12). In conclusion, although the lack of a randomized controlled design precludes drawing firm conclusions, our results suggest that pre-operative loco-regional therapy may confer a survival benefit after OLT in the subgroup with pathologic T2 and T3 HCC.

Adult↗

The dl1520 virus is found preferentially in tumor tissue after direct intratumoral injection in oral carcinoma.

PURPOSE: dl1520 (also known as Onyx-015) is an E1B-deleted adenovirus designed to selectively lyse p53-deficient cancer cells. Clinical trials involving patients with recurrent squamous cell carcinoma of the head and neck have shown clinical efficacy, but no direct evidence as to the tumor or p53 selectivity of the virus was demonstrated. We wanted to determine whether dl1520 is selective for survival and replication within tumor tissue after direct injection and whether this is determined by p53 status of the tissues. We also wanted to ascertain whether the virus has any macroscopic effect on normal tissue. EXPERIMENTAL DESIGN: An open-label Phase II trial was devised in which a fixed dose of the virus was administered to 15 patients via a direct intertumoral injection before surgery for untreated oral squamous cell carcinoma. The agent was also delivered into an area of adjacent normal buccal mucosa. Specimens of the excised tumor and of biopsies of the injected normal tissue were assessed for viral presence and p53 status. RESULTS: We demonstrated that the virus replicates selectively in tumor as opposed to normal tissue after this direct injection. It was not possible to determine whether this selectivity was p53 related. It was found that dl1520 triggers an early rise in apoptosis levels in injected normal tissues. No adverse effects of viral injection were noted. CONCLUSIONS: This is the first report of injection of dl1520 into previously untreated squamous cell cancer. The data support the concept that dl1520 is replication deficient in normal, compared with cancerous, tissues and has potential as a selective anticancer agent against tumor tissues.

Adenoviridae↗