Reproducible doxycycline-inducible transgene expression at specific loci generated by Cre-recombinase mediated cassette exchange

Comparative analysis of mutants using transfection is complicated by clones exhibiting variable levels of gene expression due to copy number differences and genomic position effects. Recombinase-mediated cassette exchange (RMCE) can overcome these problems by introducing the target gene into pre-determined chromosomal loci, but recombination between the available recombinase targeting sites can reduce the efficiency of targeted integration. We developed a new LoxP site (designated L3), which when used with the original LoxP site (designated L2), allows highly efficient and directional replacement of chromosomal DNA with incoming DNA. A total of six independent LoxP integration sites introduced either by homologous recombination or retroviral delivery were analyzed; 70-80% of the clones analyzed in hamster and human cells were correct recombinants. We combined the RMCE strategy with a new, tightly regulated tetracycline induction system to produce a robust, highly reliable system for inducible transgene expression. We observed stable inducible expression for over 1 month, with uniform expression in the cell population and between clones derived from the same integration site. This system described should find significant applications for studies requiring high level and regulated transgene expression and for determining the effects of various stresses or oncogenic conditions in vivo and in vitro.

A membrane protein enriched in endoplasmic reticulum exit sites interacts with COPII

Although all mammalian COPII components have now been cloned, little is known of their interactions with other regulatory proteins involved in exit from the endoplasmic reticulum (ER). We report here that a mammalian protein (Yip1A) that is about 31% identical to S. cerevisiae and which interacts with and modulates COPII-mediated ER-Golgi transport. Yip1A transcripts are ubiquitously expressed. Transcripts of a related mammalian homologue, Yip1B, are found specifically in the heart. Indirect immunofluorescence microscopy revealed that Yip1A is localized to vesicular structures that are concentrated at the perinuclear region. The structures marked by Yip1A co-localized with Sec31A and Sec13, components of the COPII coat protein complex. Immunoelectron microscopy also showed that Yip1A co-localizes with Sec13 at ER exit sites. Overexpression of the hydrophilic N terminus of Yip1A arrests ER-Golgi transport of the vesicular stomatitis G protein and causes fragmentation and dispersion of the Golgi apparatus. A glutathione S-transferase fusion protein with the hydrophilic N terminus of Yip1A (GST-Yip1A) is able to bind to and deplete vital components from rat liver cytosol that is essential for in vitro vesicular stomatitis G transport. Peptide sequence analysis of cytosolic proteins that are specifically bound to GST-Yip1A revealed, among other proteins, mammalian COPII components Sec23 and Sec24. A highly conserved domain at the N terminus of Yip1A is required for Sec23/Sec24 interaction. Our results suggest that Yip1A is involved in the regulation of ER-Golgi traffic at the level of ER exit sites.

Response and progression in recurrent malignant glioma

In this article we report the results of a study of the relationship between response and progression in 375 patients with recurrent glioma enrolled in phase II chemotherapy trials. We reviewed the records of patients from 8 consecutive phase II trials, including 225 patients with recurrent glioblastoma multiforme and 150 with recurrent anaplastic astrocytoma. Median age was 45 years (range, 15-82) and median Karnofsky performance score was 80 (range, 60-100). Forty-one patients (11%) had more than two prior resections and/or more than two prior chemotherapy regimens. Best response was complete (n = 1) or partial (n = 33) in 34 patients (9%). Median time to response was 14 weeks, and median response duration was 44 weeks. Simon-Makuch estimates for 52-week progression-free survival for patients progression-free at 13 weeks were 48% for response and 28% for nonresponse. When response was treated as a time-dependent covariate in a Cox proportional hazards regression analysis, response was associated with significantly lower failure rates (hazard ratio 0.5; 95% confidence interval 0.3-0.8; P = 0.0016). This study showed that response in recurrent glioma is associated with a significant reduction in progression rates.

MAPD--an objective way to select mAs for paediatric brain CT

CT is an advanced imaging modality, but the imaging parameters are normally selected subjectively. For standard head examinations, most of the parameters used are consistent amongst different centres, with the exception of large variations in the selection of the tube current-exposure time product (mAs). As a result, CT images may contain unacceptable levels of noise, or the patient may receive excessive radiation. In this study, the maximum anteroposterior diameter (MAPD) was shown to be a good criterion for mAs selection, and could be measured in a pilot view. 200 paediatric brain CT studies were randomly selected to determine the MAPD at the mid brain level. With knowledge of MAPD distribution, a phantom study was performed to determine the relationship between MAPD and the mAs required for consistent and acceptable image noise. It was found that the required mAs increased linearly with MAPD. Assuming the manufacturer's recommended value is "appropriate" for the average MAPD, the appropriate mAs value could be estimated. Using this method, appropriate mAs values were calculated retrospectively for a group of 240 randomly selected paediatric brain CT studies and compared with the actual mAs subjectively determined by the radiographer. Although their average values were similar, the difference between the calculated and actual values deviated markedly in some cases. When the actual mAs was smaller than the calculated value, higher image noise was observed. However, reduction of image noise was barely observed when the applied mAs was larger than the calculated value. Thus, this method is more objective and appropriate for determination of the mAs value for paediatric brain CT than the traditional subjective method.

Mammalian homologues of yeast sec31p. An ubiquitously expressed form is localized to endoplasmic reticulum (ER) exit sites and is essential for ER-Golgi transport

The yeast coat protein II (COPII) is responsible for vesicle budding from the endoplasmic reticulum (ER). Mammalian functional homologues for all yeast COPII components, except for Sec31p, have been reported. We have cloned a mammalian cDNA whose product (Sec31A) is about 26% identical to Saccharomyces cerevisiae Sec31p. Data base searches also revealed another partial sequence encoding a polypeptide (Sec31B) that is 40% identical to Sec31A. Northern analysis revealed that Sec31A transcripts are ubiquitously and abundantly expressed, while Sec31B transcripts are particularly enriched in the testis and thymus, but present in very low levels in other tissues. Sec31A is localized to vesicular structures that scatter throughout the cell but are concentrated at the perinuclear region. The structures marked by Sec31A contain Sec13, a component of COPII that is well characterized to mark the ER exit sites. Immunoelectron microscopy revealed that Sec31A colocalizes with Sec13 in structures with extensive vesicular-tubular profiles. Antibodies raised against a C-terminal portion of Sec31A co-precipitate Sec13 and inhibit ER-Golgi transport of temperature-arrested vesicular stomatitis G protein in a semi-intact cell assay. Cytosol immunodepleted of Sec31A failed to support vesicular stomatitis G protein transport, which can be rescued by a high molecular weight fraction of the cytosol containing both Sec31A and Sec13. We conclude that Sec31A represents a functional mammalian homologue of yeast Sec31p.

Changes in chromatin organization at the neutrophil elastase locus associated with myeloid cell differentiation

Neutrophil elastase, proteinase-3, and azurocidin are primary components of neutrophil azurophilic granules and are encoded by closely linked genes (gene symbols ELA2, PRTN3, and AZU1, respectively) in a region of approximately 50 kb. These genes are coordinately expressed in a granulocyte-specific fashion, but the mechanisms defining this pattern of expression are unknown. To understand the role of chromatin organization in governing the expression of ELA2, PRTN3, and AZU1, we mapped this region of chromosome 19 and identified the adipsin (complement factor D) gene in proximity to the 3' end of ELA2. We then examined the changes in chromatin structure at the locus which accompany myeloid cell differentiation and identified 17 DNase I hypersensitive sites (DHS 1 to 17) in U-937 cells, an early myelomonocytic cell line expressing high levels of neutrophil elastase. Chemically induced differentiation and concomitant downregulation of AZU1, PRTN3, and ELA2 transcription in U-937 cells is not accompanied by changes in the DHS-pattern. Mature neutrophils, however, do not carry any of these hypersensitive sites, indicating a large degree of chromatin remodeling at this locus accompanying terminal granulocytic differentiation. Sixteen of the 17 DHS identified in U-937 cells are also present in the HL-60 myelomonocytic cell line. Hematopoietic cell lines representing the early erythroid and lymphocyte lineages, and a nonhematopoietic cell line display a subset of the hypersensitive sites. The altered chromatin structure specific to cells that actively transcribe the AZU1-PRTN3-ELA2 genes suggests that chromatin reorganization is an important mechanism regulating the myeloid-specific transcription of this gene cluster.

Response and progression in recurrent malignant glioma

In this article we report the results of a study of the relationship between response and progression in 375 patients with recurrent glioma enrolled in phase II chemotherapy trials. We reviewed the records of patients from 8 consecutive phase II trials, including 225 patients with recurrent glioblastoma multiforme and 150 with recurrent anaplastic astrocytoma. Median age was 45 years (range, 15-82) and median Karnofsky performance score was 80 (range, 60-100). Forty-one patients (11%) had more than two prior resections and/or more than two prior chemotherapy regimens. Best response was complete (n = 1) or partial (n = 33) in 34 patients (9%). Median time to response was 14 weeks, and median response duration was 44 weeks. Simon-Makuch estimates for 52-week progression-free survival for patients progression-free at 13 weeks were 48% for response and 28% for nonresponse. When response was treated as a time-dependent covariate in a Cox proportional hazards regression analysis, response was associated with significantly lower failure rates (hazard ratio 0.5; 95% confidence interval 0.3-0.8; P = 0.0016). This study showed that response in recurrent glioma is associated with a significant reduction in progression rates.

Outcomes and prognostic factors in recurrent glioma patients enrolled onto phase II clinical trials

PURPOSE

To determine aggregate outcomes and prognostic covariates in patients with recurrent glioma enrolled onto phase II chemotherapy trials.

PATIENTS AND METHODS

Patients from eight consecutive phase II trials included 225 with recurrent glioblastoma multiforme (GBM) and 150 with recurrent anaplastic astrocytoma (AA). Their median age was 45 years (range, 15 to 82 years) and their median Karnofsky performance score was 80 (range, 60 to 100). Prognostic covariates were analyzed with respect to tumor response, progression-free survival (PFS), and overall survival (OS) by multivariate logistic and Cox proportional hazards regression analyses.

RESULTS

Overall, 34 (9%) had complete or partial response, whereas 80 (21%) were alive and progression-free at 6 months (APF6). The median PFS was 10 weeks and median OS was 30 weeks. Histology was a robust prognostic factor across all outcomes. GBM patients had significantly poorer outcomes than AA patients. The APF6 proportion was 15% for GBM and 31% for AA, whereas the median PFS was 9 weeks for GBM and 13 weeks for AA. Results were also significantly poorer for patients with more than two prior surgeries or chemotherapy regimens.

CONCLUSION

Histology is a dominant factor in determining outcome in patients with recurrent glioma enrolled onto phase II trials. Future trials should be designed with separate histology strata.

Differential oligomerization of membrane-bound CD38/ADP-ribosyl cyclase in porcine heart microsomes

A protein fraction displaying ADP-ribosyl cyclase activity was purified from porcine heart microsomes which appeared as a major band of 45 kDa on Coomassie blue stained SDS-PAGE gel under reducing condition. Protein immunoblot analysis with antiserum to recombinant rat CD38 showed a series of bands (45-285 kDa) under nonreducing condition, while only the 45 kDa monomer under reducing condition. The high molecular weight oligomers of CD38 were found to be stable even upon treatment with various concentrations of SDS in the sample buffer and also upon incubation at lower temperature. These oligomers of CD38 also displayed higher ADP-ribosyl cyclase activity than that of the monomer.

Recurrent cystic radiation necrosis of the brain

Cystic radiation necrosis is a rare complication of radiotherapy for nasopharyngeal carcinoma. The magnetic resonance imaging (MRI) characteristics have not been described. Serial MRI images were done on a patient who developed multiple cysts in the brain as a result of irradiation for his nasopharyngeal carcinoma. The characteristic MRI features included a slightly higher T1-weighted signal than cerebrospinal fluid, surrounding white matter edema as indicated by the high T2-weighted signal, and absence of gadolinium enhancement on the cyst wall. The adjacent gray matter in the anterior temporal lobes and inferior frontal lobes, which were included in the radiation field, had gadolinium enhancement. Dosimetry data and isodose contour maps revealed that his frontal lobes and anterior temporal lobes received 7920 cGy and 5040-6480 cGy of radiation respectively. Despite placement of multiple cysto-peritoneal shunts for decompression, new cysts eventually developed and previously shunted cysts enlarged in size. The management of cystic radiation necrosis of the brain remains unsatisfactory.

Leptomeningeal disease in pre-leukemic syndrome: cytogenetic abnormality versus cellular morphology

Refractory anemia with excess blasts in transformation (RAEB-T) is a pre-leukemic syndrome that can progress to acute myelogenous leukemia (AML). Although leptomeningeal disease in AML is rare and it is commonly associated with specific cytogenetic abnormalities, it has not been documented in RAEB-T. We report a woman who experienced seizures and had subarachnoid enhancement on MRI suggestive of leukemic infiltrates in the leptomeninges. Her bone marrow aspirate revealed 6.6% blasts and the presence of Auer rods, findings consistent with a diagnosis of RAEB-T. Subsequent cytogenetic analysis detected an uncommon deletion of chromosome 11q23, and the breakpoint on chromosome 11 is identical to that seen in AML patients having leptomeningeal disease and translocation between chromosome 9 and 11. Although RAEB-T is not considered as leukemia and is thought unlikely to involve the central nervous system, the presence of leptomeningeal disease and 11q23 deletion in our patient suggests that cytogenetic abnormality may be an important determinant of neurological complications, regardless of a diagnosis of RAEB-T or AML which is based on cellular morphology.

Correlation between dynamic MRI and outcome in patients with malignant gliomas

We assessed the correlation between dynamic MRI results and clinical outcomes in patients with malignant gliomas. Rapid serial MRIs were obtained after bolus injection of gadolinium that resulted in an initial fast uptake followed by a slow uptake of contrast. The maximum rate of uptake and delayed rate of uptake were correlated with survival and prognostic covariates such as age and histology. In 121 subjects, higher maximum uptake rates, 3.6 signal intensity units per second or greater, were associated with shorter survival (p = 0.0066). The correlation of delayed rate of uptake with survival was less significant. After adjusting for age, histology, and Karnofsky performance score, the maximum rate of uptake remained more significantly correlated with survival than the delayed rate of uptake. Thirty-one patients had surgery within 1 month of dynamic MRI, and those with glioblastoma multiforme or anaplastic gliomas had higher maximum rates of uptake than those with pure necrosis or mixed tumor and necrosis (p = 0.022). No correlation between delayed rate of uptake and histology was seen in this group of patients. Our results suggest that the maximum rate of uptake in dynamic MRI can be a prognostic measure for patients with malignant gliomas. Further prospective study is needed to assess the utility of this technique for evaluating brain tumors.

Palliation of intractable cancer pain by MRI-guided cingulotomy

CASE REPORT

Three cases of intractable pain arising from widespread metastatic cancer with poor response to opioids were treated with MRI-guided cingulotomy.

RESULTS AND CONCLUSIONS

In most cases, MRI-guided cingulotomy was associated with significant pain relief and reduced opioid use. To provide insight into the role of MRI-guided cingulotomy in oncologic pain refractory to more conservative measures, the relative risks and benefits of cingulotomy are discussed, along with the course of one patient who experienced postoperative cognitive impairment. This report also describes the relevant neurosurgical and pharmacotherapeutic issues associated with management of pain in patients with widespread metastatic disease.

Chemosensitive epidural spinal cord disease in non-Hodgkins lymphoma

Epidural spinal cord disease (ESCD), an infrequent complication of systemic non-Hodgkins lymphoma (NHL), can occur at diagnosis or at relapse, and is usually treated with radiotherapy, or infrequently surgical decompression. We retrospectively analyzed 140 patients with intermediate-grade NHL (IG-NHL) who were treated on a dose-intense protocol using doxorubicin, vincristine, and high-dose cyclophosphamide (NHL-15). There were seven episodes of ESCD in six (4.3%) patients. Five episodes were asymptomatic at presentation; one patient had back pain, leg numbness, and tingling; and one had radicular pain and mild leg weakness. None had malignant cells in the CSF. One patient received high-dose dexamethasone after laminectomy for diagnostic biopsy; otherwise, dexamethasone was used only as an anti-emetic prior to chemotherapy. Patients who developed ESCD at diagnosis received the planned course of NHL-15 chemotherapy as treatment for ESCD, and those treated with NHL-15 who developed ESCD at relapse were given a regimen containing ifosfamide, carboplatin, and etoposide (ICE). After chemotherapy alone, five of seven episodes showed radiographic resolution of ESCD and improvement of neurologic deficits. One patient received consolidation radiotherapy (2,700 cGy) to the spine after ICE for relapsed ESCD and had a complete response. One patient had progression of systemic lymphoma and ESCD despite chemotherapy. These data suggest that chemotherapy may be effective as initial treatment of ESCD in IG-NHL and may reduce the potential complications of spinal surgery and radiotherapy.

Reaping the benefits of medical information systems

Increasingly, external forces affect and constrain physicians' clinical decision making and consequently their practice of medicine. Physicians are expected to achieve optimal patient outcomes at the lowest possible cost, which requires that they have quick and convenient access to comprehensive clinical information from different sources. Considerable experience to date has shown that computers can improve physicians' problem solving and decision making by presenting pertinent data, information, and knowledge when it is needed, where it is needed, and in an appropriate format. The authors advocate the use of medical information systems in the daily practice of medicine. They identify critical information-related issues affecting clinicians, provide a brief overview of computer applications in medical care, and discuss studies that indicate how medical information systems can assist physicians in the delivery of cost-effective, high-quality care. Finally they discuss how individual institutions can best reap the benefits of medical information systems.

Improving laboratory testing: can we get physicians to focus on outcome?

Managed care is changing the financing of healthcare and replacing open-ended reimbursement with fixed pricing schemes. Clinical laboratory tests will remain an important part of medical practice because laboratory information is essential for diagnosis and management of patients. The relative role of the hospital-based clinical laboratory, however, remains to be determined because healthcare organizations are reevaluating their services and attempting to drive down costs through reducing unit costs, decreasing utilization of services, and improving patient outcomes. The challenge for the clinical laboratory in managed care is to achieve appropriate utilization of laboratory tests so that clinical outcomes are optimized. The clinical laboratory at this medical center has used a number of approaches to improve utilization of thyroid function tests, isoenzyme tests for myocardial infarction, beta-human chorionic gonadotropin tests, and stat laboratory services for the emergency department. These experiences suggest that the laboratory can contribute to optimizing utilization of laboratory tests. This goal will require mutual cooperation of both the clinician and the clinical laboratory physician and (or) scientist.

Improving laboratory testing: can we get physicians to focus on outcome?

Managed care is changing the financing of healthcare and replacing open-ended reimbursement with fixed pricing schemes. Clinical laboratory tests will remain an important part of medical practice because laboratory information is essential for diagnosis and management of patients. The relative role of the hospital-based clinical laboratory, however, remains to be determined because healthcare organizations are reevaluating their services and attempting to drive down costs through reducing unit costs, decreasing utilization of services, and improving patient outcomes. The challenge for the clinical laboratory in managed care is to achieve appropriate utilization of laboratory tests so that clinical outcomes are optimized. The clinical laboratory at this medical center has used a number of approaches to improve utilization of thyroid function tests, isoenzyme tests for myocardial infarction, beta-human chorionic gonadotropin tests, and stat laboratory services for the emergency department. These experiences suggest that the laboratory can contribute to optimizing utilization of laboratory tests. This goal will require mutual cooperation of both the clinician and the clinical laboratory physician and (or) scientist.

Los Angeles County-University of Southern California Medical Center clinical pathology case conference: extreme hypermagnesemia in a neonate

A preterm male infant born at 33 weeks of gestation developed respiratory depression and apnea at approximately 20 h after birth. Laboratory tests indicated severe hypermagnesemia, acidosis, and hypercalcemia. Cord blood and maternal blood concentrations of magnesium were normal. The effects and possible causes of hypermagnesemia are reviewed. The infant recovered with treatment, although the etiology of his hypermagnesemia remains unknown.

Los Angeles County-University of Southern California Medical Center clinical pathology case conference: extreme hypermagnesemia in a neonate

A preterm male infant born at 33 weeks of gestation developed respiratory depression and apnea at approximately 20 h after birth. Laboratory tests indicated severe hypermagnesemia, acidosis, and hypercalcemia. Cord blood and maternal blood concentrations of magnesium were normal. The effects and possible causes of hypermagnesemia are reviewed. The infant recovered with treatment, although the etiology of his hypermagnesemia remains unknown.

Pharmacological and physiological properties of a putative ganglionic nicotinic receptor, alpha 3 beta 4, expressed in transfected eucaryotic cells

Neuronal nicotinic acetylcholine receptor subunits alpha 3 (PCA48E) and beta 4S (ZPC13) were expressed in human embryonic kidney (HEK)-293 cells by calcium phosphate transfection. In the presence of atropine, acetylcholine (ACh) induced fast activating currents which exhibited desensitization and inward rectification. The EC50 for ACh was 202 +/- 32 microM with a Hill coefficient of 1.9 +/- 0.4. The rank order of nicotinic agonist potency was 1,1-dimethyl-4-phenylpiperozinium (DMPP) > cytisine = nicotine approximately equal to ACh. The maximal response elicited by DMPP was substantially less than that elicited by other agonists, suggesting that DMPP is a partial agonist. ACh (500 microM) responses were very effectively blocked by equimolar concentrations (100 microM) of the ganglionic antagonists d-tubocurarine, mecamylamine and hexamethonium. Equal concentrations of the potent muscle receptor antagonist decamethonium and the competitive antagonist dihydro-beta-erythroidine were much less effective. alpha bungaro-toxin (1 microM) had little effect on ACh-induced responses. This physiological and pharmacological profile is consistent with a ganglionic nicotinic response.

Therapeutic and neurotoxic effects of 2-chlorodeoxyadenosine in adults with acute myeloid leukemia

Despite expectations that 2-chlorodeoxyadenosine (2-CdA) would prove active primarily in lymphoproliferative diseases, early reports suggested unexpected high activity of this drug in heavily pretreated children with acute myeloblastic leukemia (AML) at a maximally tolerated dose of 8.9 mg/m2/day for 5 days. In view of these findings, we conducted an escalating dose trial of 2-CdA in adult patients with relapsed or resistant AML. Thirty-six patients who had received extensive prior therapy were treated at 9 dose levels of 2-CdA at daily doses ranging from 5 to 21 mg/m2 for 5 days. 2-CdA eliminated leukemic blasts from the peripheral blood in 32 of 36 cases; however, bone marrow hypoplasia was seen only at daily dose levels > or = 15 mg/m2. We observed a total of 3 complete remissions: 1 at the 15 mg/m2/d dose level and 2 at the 21 mg/m2/d dose level; these responses persisted for 3, 2, and 3 months, respectively. Although prolonged myelosuppression would have been dose-limiting at 21 mg/m2/d for 5 days, the most important adverse effect was the development of a sensorimotor peripheral neuropathy. This reaction, whose onset was substantially delayed after completion of drug treatment, was observed in 2 of 5 patients at the 19 mg/m2/d level and in 4 of 4 evaluable patients at the 21 mg/m2/d level. Pathologically, this process was characterized by axonal degeneration and secondary demyelination. Other side effects included reactivation of a posttransplant Epstein-Barr virus-related lymphoma in 1 patient and tumor lysis syndrome. We conclude that the maximally tolerable dose of 2-CdA in adult patients (17 mg/m2/d for 5 days) in approximately twofold in excess of that previously reported in children and that the limiting toxic effect is a degenerative neuropathic disorder. We confirm that this drug has definite activity in AML, but the magnitude of this effect needs to be determined in larger numbers of patients who have received less extensive therapy. This agent deserves further evaluation in patients with both AML and acute lymphoblastic leukemia at these higher doses and perhaps as part of a preparative regimen for patients undergoing bone marrow transplantation.