An overview of RB1 transcript alterations detected during retinoblastoma genetic screening

Identification of pathogenic RB1 variants aids in the clinical management of families with retinoblastoma. We routinely screen DNA for RB1 variants, but transcript analysis can also be used for variant screening, and to help decide variant pathogenicity. DNA was screened by conformation analysis followed by Sanger sequencing. Large deletion/insertions were detected by polymorphism analysis, MLPA and quantitative-PCR. Methylation-specific PCR was used to detect hypermethylation. RNA screening was performed when a DNA pathogenic variant was missing, or to determine effects on splicing.Two hundred and thirteen small coding variants were predicted to affect splicing in 207 patients. Splice donor (sd) variants were nearly twice as frequent as splice acceptor (sa) with the most affected positions being sd + 1 and sa-1. Some missense and nonsense codons altered splicing, while some splice consensus variants did not. Large deletion/insertions can disrupt splicing, but RNA analysis showed that some of these are more complex than indicated by DNA testing. RNA screening found pathogenic variants in 53.8% of samples where DNA analysis did not. RB1 splicing is altered by changes at consensus splice sites, some missense and nonsense codons, deep intronic changes and large deletion/insertions. Common alternatively spliced transcripts may complicate analysis. An effective molecular screening strategy would include RNA analysis to help determine pathogenicity.

MYCN amplification levels in primary retinoblastoma tumors analyzed by Multiple Ligation-dependent Probe Amplification

Background: Retinoblastoma (Rb) is a childhood tumor of the developing retina where predisposition is caused by RB1 pathogenic variants. MYCN amplification (MYCN^A) has been implicated in around 2% of sporadic unilateral Rb tumors with no detectable RB1 variants. We audited data from tumors collected between 1993 and 2019 to determine if this is the case for patients treated at Barts Health NHS Trust, and how often it occurred alongside RB1 variants. Materials and methods: Screening for MYCN^A was carried out by Multiple Ligation Probe Analysis of tumor and blood samples collected for RB1 genetic screening. The cohort consisted of 149 tumors, of which 114 had matched blood samples. Results: 10/149 (6.7%) tumors were positive for MYCN^A in a population containing a disproportionate number of cases negative for RB1 pathogenic variants. Of 65 unbiased tumors collected from 2014 to 2019, 2 (3.1%) had MYCN^A. All MYCN^A samples were from sporadic, unilateral patients and 3/10 (30%) had RB1 pathogenic variants. MYCN^A was not detected in any blood sample. No MYCN^A tumor had 6p gain which is usually a common alteration in Rbs. Conclusions: MYCN^A occurs in a small fraction of Rbs and can occur in the presence of pathogenic RB1 variants. However, where it occurs alongside RB1 alterations, the age of onset appears to be later. MYCN^A has yet to be seen as a heritable change. In sporadic cases with early diagnosis, Rbs with no RB1 pathogenic variant identified should be tested for MYCN^A. Conversely, tumors with MYCN^A should still be screened for RB1 pathogenic variants.

Whole-Genome Sequencing of Retinoblastoma Reveals the Diversity of Rearrangements Disrupting RB1 and Uncovers a Treatment-Related Mutational Signature

The development of retinoblastoma is thought to require pathological genetic changes in both alleles of the RB1 gene. However, cases exist where RB1 mutations are undetectable, suggesting alternative pathways to malignancy. We used whole-genome sequencing (WGS) and transcriptomics to investigate the landscape of sporadic retinoblastomas derived from twenty patients, sought RB1 and other driver mutations and investigated mutational signatures. At least one RB1 mutation was identified in all retinoblastomas, including new mutations in addition to those previously identified by clinical screening. Ten tumours carried structural rearrangements involving RB1 ranging from relatively simple to extremely complex rearrangement patterns, including a chromothripsis-like pattern in one tumour. Bilateral tumours obtained from one patient harboured conserved germline but divergent somatic RB1 mutations, indicating independent evolution. Mutational signature analysis showed predominance of signatures associated with cell division, an absence of ultraviolet-related DNA damage and a profound platinum-related mutational signature in a chemotherapy-exposed tumour. Most RB1 mutations are identifiable by clinical screening. However, the increased resolution and ability to detect otherwise elusive rearrangements by WGS have important repercussions on clinical management and advice on recurrence risks.

Prognostic Information for Known Genetic Carriers of RB1 Pathogenic Variants (Germline and Mosaic)

PURPOSE

To compare the number of tumors per eye for mosaic carriers of RB1 pathogenic variants with full germline variants and the conversion from unilateral to bilateral disease.

DESIGN

Retrospective cohort study comparing patients with retinoblastoma and different genetic subtypes: high penetrance (HP), low penetrance (LP), and mosaicism.

PARTICIPANTS

Data were analyzed between 1992 and 2018 at the Retinoblastoma Unit, Royal London Hospital, London, United Kingdom. All familial patients had a parent with a known pathogenic variant even if the parent did not manifest the disease.

MAIN OUTCOME MEASURES

Number of tumors per eye in children who developed retinoblastoma in that eye. Other outcomes included total number of tumors per patient, age at diagnosis, laterality at presentation and later, sex, and stage according to International Intraocular Retinoblastoma Classification.

RESULTS

A total of 111 patients were included: 64 full germline, familial patients (53 HP and 11 LP) and 47 mosaic patients. Twelve HP patients (23%) were unilateral, and 8 of 12 patients (67%) developed tumors in their previously unaffected eye. A total of 34 mosaic patients (72%) were unilateral, and only 2 (6%) developed tumors in their unaffected eye. Age at diagnosis was higher in mosaic patients (median, 22 months) than in HP patients (median 7) (P < 0.00002). The number of tumors per eye was fewer in patients with mosaic alleles (median, 1.0; range, 1-6) compared with patients with HP alleles (median, 3.0; range, 1-8) (P < 0.0003). All 3 children (4 eyes) with mosaicism and more than 2 tumors per eye had high levels of mosaicism.

CONCLUSIONS

Children with mosaic alleles have fewer tumors per eye compared with those with known high-penetrant pathogenic variants and are more likely to remain unilateral. The level of mosaicism has an impact on laterality and number of tumors.

RUNX3 levels in human hematopoietic progenitors are regulated by aging and dictate erythroid-myeloid balance

Healthy bone marrow progenitors yield a co-ordinated balance of hematopoietic lineages. This balance shifts with aging toward enhanced granulopoiesis with diminished erythropoiesis and lymphopoiesis, changes which likely contribute to the development of bone marrow disorders in the elderly. In this study, RUNX3 was identified as a hematopoietic stem and progenitor cell factor whose levels decline with aging in humans and mice. This decline is exaggerated in hematopoietic stem and progenitor cells from subjects diagnosed with unexplained anemia of the elderly. Hematopoietic stem cells from elderly unexplained anemia patients had diminished erythroid but unaffected granulocytic colony forming potential. Knockdown studies revealed human hematopoietic stem and progenitor cells to be strongly influenced by RUNX3 levels, with modest deficiencies abrogating erythroid differentiation at multiple steps while retaining capacity for granulopoiesis. Transcriptome profiling indicated control by RUNX3 of key erythroid transcription factors, including KLF1 and GATA1 These findings thus implicate RUNX3 as a participant in hematopoietic stem and progenitor cell aging, and a key determinant of erythroid-myeloid lineage balance.

Number, frequency and time interval of examinations under anesthesia in bilateral retinoblastoma

PURPOSE

Current practice in retinoblastoma (Rb) has transformed this malignancy into a curable disease. More attention should therefore be given to quality of life considerations, including measures related to examinations under anesthesia (EUAs). We aimed to investigate EUA measures in bilateral Rb patients and compare the findings to EUAs in unilateral Rb.

METHODS

A retrospective analysis of bilateral Rb patients that presented to the London Rb service from 2006 to 2013, were treated and had long-term follow-up.

RESULTS

A total of 62 Rb patients, 15 (24.2%) of which had International Intraocular Retinoblastoma Classification (IIRC) group A/B/no Rb at presentation, 26 (41.9%) C/D, and 21 (33.9%) were E in at least one eye. The mean number of EUAs was 35.8 ± 21.5, mean time from first to last EUA was 50.6 ± 19.9 months, and mean EUA frequency was 0.715 ± 0.293 EUAs/month. IIRC group was found not to correlate with any of the EUA measures. Age at presentation inversely correlated with time interval from first to last EUA and to EUA frequency (p ≤ 0.029). Rb family history correlated with the latter measure (p = 0.005) and intraophthalmic artery chemotherapy and brachytherapy correlated with all EUA measures (p ≤ 0.029). Mean follow-up time was 80.1 ± 24.3 months. When compared with a previously reported cohort of unilateral Rb, the present group underwent 3× more EUAs (p < 0.001) over nearly double the time (p < 0.001).

CONCLUSIONS

Families should be counselled on anticipated EUA burden associated with bilateral Rb. In this respect, age at presentation and family history were found to have a predictive role, whereas IIRC group did not.

Detection and reporting of RB1 promoter hypermethylation in diagnostic screening

BACKGROUND

RB1 gene screening aids clinical management and genetic counselling in retinoblastoma families. Here we present epigenetic changes identified during routine molecular RB1 screening of tumor and blood samples. Complications in interpreting RB1 methylation are discussed.

MATERIALS AND METHODS

Screening for RB1 promoter hypermethylation was carried out by Methylation Specific PCR (MS-PCR) after bisulphite modification of DNA. The cohort consisted of 315 tumors, and 204 blood samples, from 497 retinoblastoma patients (22 patients had both blood and tumor screened).

RESULTS

11.4% of retinoblastoma tumors had promoter hypermethylation. It was not routinely detected in blood samples, or in tumors with two other oncogenic RB1 changes. One blood sample had promoter hypermethylation due to an X;13 translocation. One tumor had low level methylation as well as two other oncogenic changes. Histopathological analysis of a small subset of age-matched tumors was similar regardless of promoter hypermethylation status.

CONCLUSIONS

Promoter hypermethylation was detected in 11.4% of the retinoblastoma tumors and should be tested for in routine RB1 screening programmes. Constitutional samples are not expected to display RB1 hypermethylation. In a small proportion of cases it may not be possible to use this somatic change in patient management.

Spectrum of RB1 mutations identified in 403 retinoblastoma patients

BACKGROUND

Retinoblastoma (RB) is a malignant, childhood tumour of the developing retina that occurs with an estimated frequency of 1 in 20 000. Identification of oncogenic mutations in the RB1 gene aids in the clinical management of families with a heritable predisposition to RB. Here we present the spectrum of genetic and epigenetic changes identified in 194 tumours and 209 blood samples, from 403 unrelated RB patients.

METHODS

Mutation screening was carried out across all 27 RB1 exons and their associated splice sites. Small coding sequence changes were detected using fluorescent conformation analysis followed by sequencing. Large exonic deletions were detected by quantitative fluorescent PCR. Methylation specific PCR of the RB1 promoter was performed to detect epigenetic alterations. Polymorphism analysis was used to determine loss of heterozygosity in tumour samples.

RESULTS

95% of the expected mutations were identified in the tumour samples, with 16 samples exhibiting only one mutation, while two samples had no detectable RB1 mutation. 96% of bilateral/familial RB blood samples and 9.5% of unilateral sporadic blood samples, yielded mutations. 111 were novel mutations.

CONCLUSIONS

The full range of screening techniques is required to achieve a high screening sensitivity in RB patients.

Discordant aPTT and Anti-Xa Values and Outcomes in Hospitalized Patients Treated with Intravenous Unfractionated Heparin

BACKGROUND:

Both the activated partial thromboplastin time (aPTT) and anti-Xa assay can be used to monitor unfractionated heparin (UFH). Following implementation of an anti-Xa method for heparin dosing protocols in our hospital, we became aware of many patients with discordant aPTT and anti-Xa values.

OBJECTIVE:

To determine the frequency of discordant aPTT and anti-Xa values in a large cohort of hospitalized patients treated with UFH, as well as the demographics, coagulation status, indication for UFH, and clinical outcomes in this population.

METHODS:

All aPTT and anti-Xa values from adults hospitalized between February and August 2009 at Stanford Hospital who were treated with UFH were analyzed. All samples were drawn simultaneously. A polynomial fit correlating aPTT and anti-Xa with a 99% confidence limit was designed. Paired aPTT/anti-Xa values were grouped according to whether the paired values fell within or outside of the concordant area. Patients were placed into groups based on concordance status, and clinical outcomes were assessed.

RESULTS:

A total of 2321 paired values from 539 patients were studied; 42% of data pairs had a high aPTT value relative to the anti-Xa value. Patients with elevated baseline prothrombin time/international normalized ratio or aPTT frequently demonstrated disproportionate relative prolongation of the aPTT. Patients with at least 2 consecutive high aPTT to anti-Xa values had increased 21-day major bleeding (9% vs 3%; p = 0.0316) and 30-day mortality (14% dead vs 5% dead at 30 days; p = 0.0202) compared with patients with consistently concordant values.

CONCLUSIONS:

aPTT and anti-Xa values are frequently discordant when used to measure UFH in hospitalized patients. A disproportionate prolongation of the aPTT relative to the anti-Xa was the most common discordant pattern in our study. Patients with relatively high aPTT to anti-Xa values appear to be at increased risk of adverse outcomes. Monitoring both aPTT and Xa values may have utility in managing such patients.

Anemia in older persons: etiology and evaluation

The aim of this study was to prospectively determine the etiology of anemia in a cohort of community-dwelling older outpatients with a comprehensive hematologic evaluation. Participants were men and women age 65 and older with anemia as defined by World Health Organization criteria recruited from outpatient hematology clinics at Stanford Hospital and Clinics (SHC) and Veterans Affairs Palo Alto Health Care System (VAPAHCS). Each participant underwent a history and physical examination, followed by a comprehensive hematologic evaluation, which in all participants included complete blood count, red cell indices, review of the blood smear, and assessment of vitamin B12, folate, iron status and renal function. Additional evaluation was obtained by clinical providers as per their discretion. 190 participants enrolled and completed the evaluation. Twelve percent of participants had iron deficiency anemia. Of those with iron deficiency in whom there was follow-up information, half normalized their hemoglobin in response to iron repletion, and half did not. Thirty-five percent of participants had unexplained anemia. Those with unexplained anemia had mildly increased inflammatory markers compared to non-anemic controls, and, at the lower hemoglobin ranges had relatively low erythropoietin levels. Sixteen percent of participants were categorized as being "suspicious for myelodysplastic syndrome." Thus, even with comprehensive hematologic evaluation, unexplained anemia is common in older anemic outpatients. Iron deficiency anemia is also common and can be difficult to diagnose, and frequently the anemia is not fully corrected with iron repletion.

Laboratory testing for heparin-induced thrombocytopenia is inconsistent in North America: a survey of North American specialized coagulation laboratories

Heparin-induced thrombocytopenia (HIT) is a serious complication of heparin therapy. As HIT is considered a clinico-pathologic entity, laboratory practices have an important role in diagnosing or excluding HIT. It was the objective of this study to assess the current status of laboratory testing for HIT in North America. An online survey consisting of 67 questions related to laboratory testing for HIT was developed by the North American Specialized Coagulation Laboratory Association (NASCOLA), and distributed to its 59 members. The survey included queries about HIT test ordering practices, HIT immunoassay and activation assays performed, and reporting practices. Data was collected from the 44 NASCOLA laboratories who responded. Of these sites, 88% performed immunoassays for HIT, commonly using commercial assays. However, sites varied in practices related to use of controls, immunoglobulin class of antibody detected, and in result interpretation and reporting. Platelet activation assays for HIT were performed by 36% of sites, commonly using assays of serotonin release (50%) or heparin-induced platelet aggregation (43%). Sites varied in the use of washed platelets versus platelet-rich plasma, controls, and heparin concentrations. This survey is the first comprehensive assessment of patterns of practice in HIT testing among diagnostic coagulation laboratories in North America. We observed site-specific variability of testing methods encompassing all stages of testing, including pre-analytical handling, testing methodologies, and result interpretation and reporting. The variability in HIT platelet activation assay methods among institutions indicates a need for proficiency testing to assess assay performance, and for consensus guidelines on HIT laboratory testing.

Genomic alterations in blastic natural killer/extranodal natural killer-like T cell lymphoma with cutaneous involvement

Natural killer and natural killer-like T cell lymphomas represent a rare type of non-Hodgkin's lymphoma originally described to involve the upper aerodigestive tract. This malignancy has been increasingly observed in other extranodal sites, particularly in the skin. Patients with cutaneous natural killer cell lymphoma generally have a poor prognosis; however, the etiology and the underlying molecular pathogenesis remain unclear. This study aimed to investigate comprehensively genomic changes in blastic natural killer and extranodal natural killer-like T cell lymphoma with cutaneous involvement. Comparative genomic hybridization showed chromosome imbalances in six of eight cases studied (75%). The mean number of chromosome imbalances per sample was 2.18+/-1.63 with similar number of gains (1.18+/-1.17) and losses (1.00+/-1.34). The most frequent DNA copy number changes observed were losses of 9/9p (83%), followed by loss of 13q and gain of 7 (67%). Similar patterns of chromosome imbalances were observed in both blastic natural killer and cutaneous natural killer-like T cell lymphomas. Loss of the RB1 gene at 13q14.2 was detected in one blastic natural killer cell lymphoma with 13q loss using a gene dosage assay, and in one cutaneous natural killer-like T cell lymphoma without 13q loss using fluorescent in situ hybridization. Genomic microarray analysis identified oncogene copy number gains of PAK1 and JUNB in three of four cases studied, and gains of RAF1, CTSB, FGFR1, and BCR in two cases. Real-time polymerase chain reaction detected amplification of CTSB and RAF1 in four of five cases analyzed, JUNB and MYCN in three cases, and REL and YES1 in two cases, respectively. In conjunction with this study, an extensive literature search for the published G-banded karyotypes of four subsets of natural killer cell lymphomas was conducted, which showed a nonrandom pattern of multiple chromosome aberrations. These results reveal consistent genetic alterations in cutaneous natural killer cell lymphomas, and provide a basis for further investigation of molecular pathogenesis in this malignancy.

Cardiopulmonary resuscitation-related injuries and homicidal blunt abdominal trauma in children

Defendants accused of inflicting fatal abdominal injuries to children occasionally raise the defense that the injuries were caused by cardiopulmonary resuscitation (CPR). The purpose of this study is to answer the question: Does closed chest CPR result in fatal blunt abdominal injuries that can be mistaken for homicidal assault? To that end, a retrospective study was conducted of all homicidal blunt abdominal injuries in children 10 years and younger from the Dade, Broward, and Palm Beach Medical Examiner's Offices from 1981 through 1997. These were compared to cases of children who died of natural causes during the same time period in Broward County who had CPR (control group 1) and to children who died of nonvehicular accidental blunt abdominal trauma (control group 2). Children with life-threatening head injuries were excluded. Medical examiner records, autopsy reports, documenting photographs, and clinical records were reviewed. The data analyzed included subject demographics, whether CPR was performed and by whom, and autopsy findings. Thirty-three child homicides with fatal abdominal injuries were reviewed. Twenty-four (73%) of the homicides received CPR. There was no difference in the nature and severity of injuries between the 24 children who received CPR and the 9 who did not. Three hundred and twenty-four cases of pediatric natural deaths were reviewed, all of which had CPR. No traumatic abdominal injuries were found in any of the children who died of natural causes. Only four children who died of natural causes had evidence of extraabdominal trauma related to CPR. No cases of nonvehicular accidental blunt abdominal trauma were identified during the 17-year period, although there were nonvehicular accidental fatalities due to extraabdominal injuries. The likelihood of CPR-related primary abdominal trauma in child homicides is very low.

Differential leukocytosis and lymphocyte mitogenic response to acute maximal exercise in the young and old

Despite the increasing use of exercise in the elderly as a means of improving muscle function, little is known regarding the effects of exercise on the senescent immune system.

PURPOSE

The purpose of this study was to determine the effects of acute maximal exercise on blood leukocyte numbers, leukocyte subsets, and the T cell mitogenic response in the elderly.

METHODS

Previously sedentary elderly (N = 33, 65.3 +/- 0.8 yr) and young (N = 14, 22.4 +/- 0.7 yr) subjects participated in a modified Balke maximal exercise treadmill test. Venous blood samples were collected pre-, immediately post-, and 20 min postexercise. Blood was analyzed for leukocyte counts, leukocyte subsets via immunofluorescence, and whole blood mitogenesis in response to various doses of mitogens.

RESULTS

Whereas VO2max was lower in the elderly, maximal RQ, age-predicted heart rates, and times to fatigue were not different, indicating that both groups achieved relative maximal exercise intensity. There were significant exercise-induced leukocytoses in both the elderly and young made up largely of a lymphocytosis and neutrophilia. The magnitude of the leukocytosis was lower in the elderly and failed to return to pre-exercise levels by 20 min postexercise. Acute maximal exercise increased CD8+ (153% vs 112% in young and old, respectively) and CD4+ (57% vs 22% in young and old, respectively) T cells when measured immediately postexercise. By 20 min postexercise, concentrations in the young were not significantly different from baseline, whereas CD8 cell number was still elevated in the old. The elderly had significantly higher percentages of memory (i.e., CD45RO+) and significantly lower percentages of naive (i.e., CD45RA+) CD4 and CD8 T cells pre-exercise, and the young and old recruited approximately equal numbers of CD8+ naive and memory cells to the blood in response to exercise. In contrast, the aged recruited significantly fewer numbers of CD4+ naive and transitional (CD45RA+RO+) cells. At most doses of Con A and PHA, the lymphoproliferative response was lower in the elderly subjects even though they had significantly higher numbers and percentages of CD3+ cells. Interestingly, immediately postexercise, young (but not old) subjects demonstrated reduced proliferative ability on a per CD3+ cell basis.

CONCLUSIONS

These data indicate that several blood leukocyte responses to maximal exercise stress are similar in the young and the old. However, the elderly demonstrate a less resilient leukocytosis and a different lympho-proliferative response following acute maximal exercise.

Chronic exercise increases macrophage-mediated tumor cytolysis in young and old mice

In this study, we determined the effects of age and chronic treadmill running (16 wk; 5 days/wk; 45 min/day; 18-22 m/min) on resident peritoneal macrophage responsiveness to interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS) in young (6 mo) and aged (22 mo) male BALB/cByJ mice by measuring cytolytic ability and production of reactive nitrogen products. Macrophages (>90% Mac-3(+)) were incubated with various concentrations of IFN-gamma and LPS for 24 h. After washing, P815 tumor cells were utilized as targets in a 16-h 51Cr release assay. We found that aging resulted in a significant reduction in the ability of macrophages to respond to the highest doses of IFN-gamma and LPS and kill P815 cells (46 +/- 4 vs. 34 +/- 2% in young and old mice, respectively). Exercise training significantly increased macrophage cytolysis in both age groups (66 + 7 vs. 44 + 2% in young and old mice, respectively); this effect was larger in the young mice. Macrophages from young exercised mice also produced significantly (50-60%) more NO-2; there was a tendency for higher NO-2 in old exercisers. The inducible nitric oxide synthase (iNOS) inhibitor NG-monomethyl-L-arginine (L-NMMA) significantly reduced macrophage cytolysis and NO-2 production and completely abrogated exercise-induced increases in these measures. RT-PCR analysis revealed significantly higher iNOS mRNA levels in macrophages obtained from the exercise-trained mice and significantly lower iNOS mRNA in old compared with young mice. We conclude that aging reduces and exercise training increases the capacity of resident peritoneal macrophages to respond to IFN-gamma and LPS with increased tumor cytolysis. Enhanced iNOS gene expression and NO-2 production are likely the contributing mechanisms of the exercise-induced enhancement of cytolysis in young mice. While L-NMMA did block the exercise-induced increase in cytolysis, exercise did not increase NO-2 or iNOS gene expression in the old mice, indicating perhaps the contribution of other cytolytic mechanisms in old mice.

An Inquiry into the Spontaneous Transfer of Problem-Solving Skill

Problem solving, by definition, involves achieving new understanding in unfamiliar contexts, and is critical to all aspects of life, especially in the educational and scientific arenas. Students learn from many experiences to develop a repertoire of abilities, including the use of logic, which enable them to spontaneously transfer their problem-solving skill to unfamiliar situations. The purpose of this study is to explore the minimum conditions necessary to facilitate the spontaneous transfer of problem solving skill in an unfamiliar context. One hundred and seventy-five subjects were presented with logically identical problems based on the Wason selection task, which differed only in the degree to which a familiar schema could be invoked to help solve the problem. In the pretest stage, only 10.5% of subjects could solve the selection problem in an unfamiliar context, whereas 57.3% could solve it in one that was familiar. The effect of three interventions, prior exposure to a familiar scenario, repeat opportunities on like problems, and process-oriented feedback, on selection task performance in an unfamiliar context was assessed in a posttest stage. Overall, none of the interventions were effective, indicating that the minimum threshold for spontaneous transfer may be above the level of intervention included in this study. Schema theory, implications for instruction, and directions for future research are discussed. Copyright 1997Academic Press

Rare microsatellite polymorphisms in the DNA repair genes XRCC1, XRCC3 and XRCC5 associated with cancer in patients of varying radiosensitivity

DNA repair defects might contribute both to cancer progression and to the extreme reactions to radiotherapy observed in approximately 5% of patients. Polymorphic microsatellites in three DNA repair genes, XRCC1, XRCC3 and XRCC5, were analyzed for possible linkage to cancer status or clinical radiosensitivity. XRCC1, 3 and 5 proteins are involved in single-strand DNA break rejoining, recombinational repair, and double-strand DNA break rejoining respectively. Mendelianly inherited microsatellite polymorphisms in these genes were analyzed in three groups: volunteers with no cancer history; radiosensitive cancer patients; cancer patients with acceptable reactions to radiotherapy. Rare heterozygous alterations in all three gene regions were found solely in the cancer subpopulation. Association testing between these rare polymorphisms and cancer status revealed a significant association for XRCC1 (P = 0.005), and XRCC3 (P = 0.004). There was also an association between these polymorphisms and clinical radiosensitivity for XRCC1 (P = 0.03), and XRCC3 (P = 0.005).

beta-1 Integrins mediate tumour cell adhesion to quiescent endothelial cells in vitro

Metastatic spread of some solid tumours is thought to depend upon the adhesion of tumour cells to the vascular endothelium followed by extravasation into surrounding tissues. We investigated the role of beta 1 integrins in the adhesion of the breast adenocarcinoma cell line MDA-MB-231 and the melanoma cell line RPMI-7951 to quiescent human umbilical vein endothelial cells (HUVEC) in vitro. In the course of adhesion assays, tumour cells were observed to adhere to quiescent HUVEC monolayers, particularly at endothelial cell-cell junctions. Immunohistochemistry revealed concentration of beta 1 integrin expression at these sites. Adhesion was reduced by pretreatment of either tumour cells or HUVEC with antibodies against beta 1 integrins. Simultaneous treatment of HUVECs and tumour cells with these antibodies produced an additive blocking effect, consistent with a heterotypic adhesion mechanism. Our data suggest that tumour cell and endothelial beta 1 integrins may play a crucial role in the arrest and migration of tumour cells through the vascular endothelium in the absence of endothelial 'activation'.

Endothelial CD44H mediates adhesion of a melanoma cell line to quiescent human endothelial cells in vitro

A critical step in the metastatic spread of tumour cells is the interaction of circulating tumour cells with the vascular endothelium. We have investigated the role of CD44 and its variants in the adhesion of a human melanoma cell line (RPMI-7951) and a breast adenocarcinoma cell line (MDA-MB-231) to quiescent human umbilical vein endothelial cells (HUVEC) in vitro. Both tumour cell lines express CD44H, CD44A and CD44v9, while HUVEC express only CD44H. Pre-treatment of endothelial cell monolayers with a blocking monoclonal antibody against CD44H (MAb 5A4) reduced the adhesion of RPMI-7951 cells but not that of MDA-MB-231. In contrast, pre-treatment of both tumour cell lines with the same antibody had no effect on adhesion. Digestion of the CD44 ligand hyaluronic acid (HA) on RPMI-7951 cells significantly reduced adhesion to endothelial monolayers, while digestion of HUVEC HA had no effect. We conclude that CD44H expressed on the surface of quiescent endothelial monolayers mediates in part the adhesion of the metastatic melanoma cell line RPMI-7951 but not that of a breast adenocarcinoma line. It does so by acting as a receptor for HA on the tumour cell surface. Tumour cell CD44H and variants CD44A and CD44v9 do not appear to be involved in adhesion to endothelial cells.

A simple fluorometric assay for quantifying the adhesion of tumour cells to endothelial monolayers

A static adhesion assay employing 6-carboxy-3',6'-diacetylfluorescein (6-CFDA) as a fluorescent marker has been developed to study the interactions of tumour cell lines with endothelial monolayers. This assay allows simple, safe quantification of cell-cell adhesion using living cells. It has been used to demonstrate that the integrin adhesion molecule VLA-4 mediates the attachment of RPMI-7951 melanoma cells to human umbilical vein endothelial cells (HUVEC) which have been activated by TNF alpha. In addition, MDA-MB-231 breast adenocarcinoma cells display greater adhesion to microvessel endothelial cells than to large vessel endothelial cells.

Osmolar gap with minimal acidosis in combined methanol and methyl ethyl ketone ingestion

Methyl ethyl ketone is a common solvent but data on overdose in humans are scarce. We report a case of co-ingestion of methyl ethyl ketone together with methanol associated with a hyperosmolar coma without anion gap metabolic acidosis. Blood levels of methyl ethyl ketone and its metabolite, 2-butanol, indicated that this solvent did contribute approximately 20 mosm/L to an observed osmolar gap of 99 mosm/L. At the levels detected, methyl ethyl ketone may have inhibited methanol metabolism, contributing to the low serum formate (1.3 mmol/L) and normal anion gap despite a blood methanol of 67 mmol/L.

Tumor aneuploidy in young patients with colorectal cancer

BACKGROUND

Colorectal cancer in young patients (40 years of age or younger) often is considered to have a worse prognosis than in older patients. The authors studied tumor DNA status and stage of disease to determine whether tumors in younger patients behaved differently from tumors in older patients.

METHODS

This retrospective study identified 33 young patients with colorectal cancer treated surgically between 1979 and 1989. The DNA content of the tumors was analyzed by DNA flow cytometry. Results were compared with 75 cases of colon cancer in patients older than 40 years of age.

RESULTS

Six of the 33 young patients had inadequate tissue for study. Four patients with ulcerative colitis were excluded. Tumor aneuploidy was present in 14 of 23 young patients (61%; mean age, 35 years) and 46 of 75 older patients (61%; mean age, 71 years). When Dukes staging was performed for the young patients, one had Stage A (4%), nine had Stage B (39%), eight had Stage C (35%), and five had Stage D (22%) disease. The control group had similar staging. The distribution of aneuploid tumors within each Dukes stage was also similar. Twenty-one young patients were available for follow-up. Four (31%) of 13 patients with aneuploid tumors died, whereas none of 8 patients with diploid tumors died. This trend was not statistically significant (P < 0.10).

CONCLUSIONS

The frequency of tumor aneuploidy, stage of disease at presentation, and distribution of tumor aneuploidy within each stage was similar when young and old patients with colorectal cancer were compared. There is a trend toward tumor aneuploidy being associated with a poorer prognosis in young patients.

Isolation and characterization of microvessel endothelial cells from human mammary adipose tissue

A method for the isolation and long-term culture of human microvessel endothelial cells from mammary adipose tissue (HuMMEC) obtained at breast reduction surgery has been developed. Pure cultures of HuMMEC were isolated by sequential digestion of the fat with collagenase and trypsin followed by specific selection of microvessel fragments with Ulex europaeus agglutinin-1 coated magnetic beads (Dynabeads). The resulting cells formed contact-inhibited monolayers on gelatin and fibronectin substrates and capillary-like "tubes" on Matrigel; they also expressed von Willebrand factor, angiotensin-converting enzyme, and accumulated acetylated low density lipoprotein. Further immunofluorescence characterization revealed the presence of antigens for the endothelial cell specific monoclonal antibodies EN4 and H4-7/33. In addition, the origin of these cells was confirmed by the demonstration of the cell adhesion molecules, platelet endothelial cell adhesion molecule-1 (CD31), and endothelial leukocyte adhesion molecule-1 (ELAM-1/E-selectin) upon stimulation with tumor necrosis factor (TNF) alpha. HuMMEC were found to express-1 ELAM-1 at lower levels of TNF alpha (< 10 ng/ml) than required by human umbilical vein endothelial cells. These cells should provide a useful in vitro model for studying various aspects of microvascular biology and pathology.

Conception rates in early postpartum ewes bred naturally or by intrauterine insemination

Ewes were treated with a medroxyprogesterone acetate (MAP) sponge for 8 d followed, at sponge removal, with 500 IU pregnant mare serum gonadotropin (PMSG) at d 30, 40 or 50 (d 0 = lambing) to induce estrus. Dry and lactating ewes were divided into equal numbers at each postpartum day and bred at estrus. Conception rates and number of accessory sperm were determined by flushing the oviducts 3 d after mating and examining the recovered ova. There was no effect (P greater than .05) of lactational status on conception rates. Conception rates increased (P less than .05) from d 30 (10%) to d 40 (45%) and from d 40 to d 50 (80%). There were fewer (P less than .05) ova with accessory sperm (5/26) in d-30 ewes compared with d-40 (10/27) or d-50 (12/24) ewes. In Exp. 2, ewes were assigned to two groups after receiving PMSG on d 30: 1) mated naturally or 2) inseminated during laparotomy near the uterotubal junction (UTJ). Dry and lactating ewes were divided evenly within each of the two treatments. Oviducts were flushed and ova were examined for cleavage. The conception rate was 60% in ewes that were inseminated in the UTJ vs 10% in ewes mated to rams (P less than .05). Lactational status had no effect on results. In conclusion, conception rates in postpartum ewes treated with MAP sponge and PMSG increased from postpartum d 30 to d 50 with natural breeding, and d-30 conception rates were increased over natural mating by insemination into the uterine horn near the UTJ.