[Ethics of (big) data applications in psychiatric practice]. / Ethiek van (big)datatoepassingen in de psychiatrische praktijk.

BACKGROUND: Due to rapid digitalization, an increasing amount of data is available in healthcare settings; big data and artificial intelligence (AI) have also made their appearance. AIM: To provide insight into various ethical dilemmas that need to be considered when applying big data in clinical practice. METHOD: Description and analyses of the ethical aspects associated with the use of clinical data in the context of psychiatric care. RESULTS: Various ethical aspects play a role in four phases; data collection, analysis, dissemination and application of results. In order to use clinical data and AI in a responsible manner, these aspects must be taken into account. CONCLUSION: The use of big data and AI in healthcare should aim to stimulate learning and improving care together with patients and professionals. Big data and AI should not be seen as the holy grail, but as a supporting tool in healthcare - a field in which many of the aspects that play a role in clinical care cannot be converted into measurable data.

Responsible data sharing in a big data-driven translational research platform: lessons learned.

BACKGROUND: To foster responsible data sharing in health research, ethical governance complementary to the EU General Data Protection Regulation is necessary. A governance framework for Big Data-driven research platforms will at least need to consider the conditions as specified a priori for individual datasets. We aim to identify and analyze these conditions for the Innovative Medicines Initiative's (IMI) BigData@Heart platform. METHODS: We performed a unique descriptive case study into the conditions for data sharing as specified for datasets participating in BigData@Heart. Principle investigators of 56 participating databases were contacted via e-mail with the request to send any kind of documentation that possibly specified the conditions for data sharing. Documents were qualitatively reviewed for conditions pertaining to data sharing and data access. RESULTS: Qualitative content analysis of 55 relevant documents revealed overlap on the conditions: (1) only to share health data for scientific research, (2) in anonymized/coded form, (3) after approval from a designated review committee, and while (4) observing all appropriate measures for data security and in compliance with the applicable laws and regulations. CONCLUSIONS: Despite considerable overlap, prespecified conditions give rise to challenges for data sharing. At the same time, these challenges inform our thinking about the design of an ethical governance framework for data sharing platforms. We urge current data sharing initiatives to concentrate on: (1) the scope of the research questions that may be addressed, (2) how to deal with varying levels of de-identification, (3) determining when and how review committees should come into play, (4) align what policies and regulations mean by "data sharing" and (5) how to deal with datasets that have no system in place for data sharing.

[Euthanasia of Dutch psychiatric patients in 2015-2017]. / Euthanasie van Nederlandse psychiatrische patiënten in 2015-2017.

BACKGROUND: The Netherlands is one of the few countries in the world that allows euthanasia and assisted suicide (EAS) due to psychiatric suffering. METHODS In 2015-2017 the Dutch regional euthanasia review committees published 43 case summaries online. Of these, 35 were suitable for analysis regarding patient characteristics and physician involvement, and 3 cases were described in detail.
RESULTS: In total, 77% of the patients were women and 51% were aged 50-70 years. Major depression disorder and personality disorders were present in almost half of the patients. All patients were considered mentally competent. CONCLUSIONS Although the incidence of psychiatric EAS cases is rising, we found no shift in patient characteristics. The division between psychiatric and somatic suffering may prove more complicated than expected. Patients dying from suicide differ in various ways from patients dying through EAS. The fact that all patients are considered competent could mean that they are unjustly seen as being vulnerable or that the competence assessment lacks due diligence.

[Is psychiatry ready to let patients review their own files? Inventory of initial experiences]. / Is de psychiatrie klaar voor de meelezende patiënt? Inventarisatie van eerste ervaringen.

BACKGROUND: Dutch patients will be granted the right to digitally access their own medical records, an option already available to the patients at the University Medical Center Utrecht since 2015. AIM: To start a conversation about the development of readily accessible online patient records. METHODS Describe the experiences of a University department of psychiatry with an online patient portal, obtained through discussions and questionnaires. RESULTS: During the next few years three legal developments will enable patients to acquire direct, remote, digital access to their medical files. Immediate online review of medical records improves accessibility and empowers the patient. Some therapists experienced a change in patient interaction. Furthermore, during documentation psychiatrists took into account that patients could review the contents at a later point. CONCLUSION: Patients' accessibility of online records will influence the patient-therapist dynamic. More research on the patient perspective and a discussion among professionals are necessary to further streamline broad implementation of online patient portals.

Monocytes of patients with amyotrophic lateral sclerosis linked to gene mutations display altered TDP-43 subcellular distribution.

AIMS: Cytoplasmic accumulation of the nuclear protein transactive response DNA-binding protein 43 (TDP-43) is an early determinant of motor neuron degeneration in most amyotrophic lateral sclerosis (ALS) cases. We previously disclosed this accumulation in circulating lymphomonocytes (CLM) of ALS patients with mutant TARDBP, the TDP-43-coding gene, as well as of a healthy individual carrying the parental TARDBP mutation. Here, we investigate TDP-43 subcellular localization in CLM and in the constituent cells, lymphocytes and monocytes, of patients with various ALS-linked mutant genes. METHODS: TDP-43 subcellular localization was analysed with western immunoblotting and immunocytofluorescence in CLM of healthy controls (n = 10), patients with mutant TARDBP (n = 4, 1 homozygous), valosin-containing protein (VCP; n = 2), fused in sarcoma/translocated in liposarcoma (FUS; n = 2), Cu/Zn superoxide dismutase 1 (SOD1; n = 6), chromosome 9 open reading frame 72 (C9ORF72; n = 4), without mutations (n = 5) and neurologically unaffected subjects with mutant TARDBP (n = 2). RESULTS: TDP-43 cytoplasmic accumulation was found (P < 0.05 vs. controls) in CLM of patients with mutant TARDBP or VCP, but not FUS, in line with TDP-43 subcellular localization described for motor neurons of corresponding groups. Accumulation also characterized CLM of the healthy individuals with mutant TARDBP and of some patients with mutant SOD1 or C9ORF72. In 5 patients, belonging to categories described to carry TDP-43 mislocalization in motor neurons (3 C9ORF72, 1 TARDBP and 1 without mutations), TDP-43 cytoplasmic accumulation was not detected in CLM or in lymphocytes but was in monocytes. CONCLUSIONS: In ALS forms characterized by TDP-43 mislocalization in motor neurons, monocytes display this alteration, even when not manifest in CLM. Monocytes may be used to support diagnosis, as well as to identify subjects at risk, of ALS and to develop/monitor targeted treatments.

Integrated surveillance of human respiratory viruses in addition to SARS-CoV-2 in a public testing facility in the Netherlands.

BACKGROUND: SARS-CoV-2 prevention measures impact the circulation of other respiratory viruses. Surveillance in the network of general practitioners is hampered by widespread testing for SARS-CoV-2 in public testing facilities. OBJECTIVES: To evaluate integrated community surveillance of SARS-CoV-2 and other respiratory viruses and describe epidemiological trends. STUDY DESIGN: Respiratory surveillance was set up within an existing SARS-CoV-2 public testing facility. Community-dwelling (a)symptomatic persons provided consent for completion of a questionnaire and additional testing on residual material from swabs taken for SARS-CoV-2 RT-PCR (Allplex Seegene). Daily, a random subset was tested for sixteen respiratory viruses by multiplex realtime PCRs (Seegene). RESULTS: Between October 6th (week 40) 2021 and April 22nd (week 16) 2022, 3,969 subjects were tested. The weekly median age ranged from 23 to 39 years. The prevalence of respiratory symptoms ranged from 98.5% (week 40) to 27.4% (week 1). The prevalence of detection of any respiratory virus (including SARS-CoV-2), ranged from 19.6% in week 49 to 75.3% in week 14. SARS-CoV-2 prevalence ranged from 2.2% (week 40) to 63.3% (week 14). Overall, SARS-CoV-2 was detected most frequently (27.3%), followed by rhinoviruses (14.6%, range 3.5-47.8%) and seasonal coronaviruses (3.7%, range 0-10.4%, mostly 229E and OC43). Influenzavirus was detected in 3.0% of participants from week 6 onwards. CONCLUSIONS: Integrated respiratory viral surveillance within public testing facilities is feasible and informative. Prevalences may be affected by changes in SARS-CoV-2 prevention and testing policies. Population characteristics help to interpret trends over time. Integrated surveillance may inform policymakers and hospitals for adequate response measures during respiratory seasons.

Pregnancy induces molecular alterations reflecting impaired insulin control over glucose oxidative pathways that only in women with a family history of Type 2 diabetes last beyond pregnancy.

In circulating lymphomonocytes (CLM) of patients with Type 2 diabetes (DM2) pyruvate dehydrogenase (PDH), the major determinant of glucose oxidative breakdown, is affected by a cohort of alterations reflecting impaired insulin stimulated glucose utilization. The cohort is also expressed, although incompletely, in 40% of healthy young subjects with a DM2-family history (FH). Pregnancy restrains glucose utilization in maternal peripheral tissues to satisfy fetal requirements. Here we explore whether pregnant women develop the PDH alterations and, if so, whether there are differences between women with and without FH (FH+, FH-). Ten FH+ and 10 FH- were evaluated during pregnancy (12-14, 24-26, and 37-39 weeks) and 1 yr after (follow-up) for fasting plasma glucose and insulin as well as body mass index (BMI), and for the PDH alterations. Twenty FH- and 20 FH+ non-pregnant women served as controls. All FH+ and FH- controls exhibited normal clinical parameters and 8 FH+ had an incomplete cohort of PDH alterations. In FH- and FH+ pregnant women at 12-14 weeks clinical parameters were normal; from 24-26 weeks, with unvaried glucose, insulin and BMI rose more in FH- and only in the latter recovered the 12-14 weeks values at follow-up. In all FH-, the cohort of PDH alterations was incomplete at 24-26 weeks, complete at 37-39 weeks, and absent at follow-up but complete from 12-14 weeks including follow-up in all FH+. In FH-, the cohort is an acquired trait restricted to pregnancy signaling transiently reduced insulin-stimulated glucose utilization; in FH+, instead, it unveils the existence of an inherited DM2-related background these women all have, that is awakened by pregnancy and as such lastingly impairs insulin-stimulated glucose utilization.

[Chronic hepatitis B virus (HBV) infection: usefulness of the combination of HBeAg and ALT determination to predict a high HBV-DNA level and therefore the necessity of referral to a specialist for possible antiviral treatment]. / Chronische hepatitis B-virus(HBV)-infectie: bruikbaarheid van de combinatie van HBeAg- en ALAT-bepaling als voorspeller van een hoog HBV-DNA-niveau en voor verwijzing naar de 2e lijn voor eventuele antivirale behandeling.

OBJECTIVE: To assess the usefulness of a simple practical guideline based on hepatitis B e-antigen (HBeAg) status and a single alanine aminotransferase (ALT) determination to predict hepatitis B virus (HBV) load in chronic HBV patients as a criterion for referral to a specialist for possible antiviral therapy. DESIGN: Prospective observational study. METHOD: 420 patients with chronic HBV infection were seen at the Municipal Health Service (MHS) in Rotterdam between 2002 and 2005. The usefulness ofa guideline based on HBeAg positivity and/or elevated ALT levels to predict high HBV DNA levels (defined as more than 10(5) copies/ml) was determined. Patients with HBeAg or an elevated ALT level were referred to a specialist according to the practical guideline. Positive and negative predictive value, sensitivity, and specificity of the referral guideline for a high HBV-DNA level were calculated. RESULTS: Less than half, 43% (181/420) of the patients, were eligible for referral to specialist care. The positive predictive value of the referral guideline was 45% (82/181, 95% CI: 38-53). The negative predictive value, i.e. the proportion of patients with low viral loads who were (rightly) not selected for referral, was 95% (227/239; 95% CI: 71-97). The sensitivity was 87% (95% CI: 80-93): the patients selected included 82 of 94 patients with a high HBV DNA level. Of the 12 patients with high viral loads not referred according to the guideline, 11 had a viral load of between 10(5)-10(6) copies/ml. CONCLUSION: A referral guideline based on HBeAg status and a single ALT determination can successfully predict viral load in chronic HBV patients and can be used in primary care to select patients for referral to specialist care. This guideline may limit the number of unnecessarily referred patients, enhancing the efficiency of the care for patients with chronic HBV infection.

[Hepatitis B virus transmission patterns in the Netherlands, 2004]. / Transmissiepatronen van hepatitis B-virus in Nederland, 2004.

OBJECTIVE: To gain insight into hepatitis B virus (HBV) transmission in the Netherlands. DESIGN: Descriptive. METHOD: During 2004, epidemiological data and blood samples (if available) were collected for all reported cases of acute HBV infections in the Netherlands. Following DNA isolation and amplification a 648 base pairs fragment of the HBV S gene was sequenced and subjected to phylogenetic analysis. The sequencing details were also linked to epidemiological information. RESULTS: In 2004, 291 cases ofacute HBV infections were reported. Blood samples were received from 171 patients (59%), and the genotype could be determined for 158 patients (54%). 6 genotypes were identified: A (64%), B (3%), C (3%), D (21%), E (5%) and F (4%). Of all patients with genotype A, 52% had been infected via homosexual or bisexual contact and 16% via heterosexual contact. Of all patients with genotype D, 42% had been infected via heterosexual contact and 15% via homosexual or bisexual contact. The genotype A cluster was extremely homogeneous with many identical sequences, while genotype B-E clusters were more heterogeneous. 4 identical sequences were found within genotype F, but the patients could not be epidemiologically linked. CONCLUSION: Sexual transmission, particularly via homosexual or bisexual contact in men, formed the most important risk factor for acquiring an acute HBV infection. Genotype A was predominant in the Netherlands, especially among homosexual or bisexual men. Most infections within genotype D occurred as a result of heterosexual contact. The results show that there was ongoing transmission of HBV in homosexual or bisexual men, while in heterosexuals more cases of new introduction were seen, possibly via chronic carriers from areas where HBV is endemic.

Privacy in Big Data psychiatric and behavioural research: A multiple-case study.

In Big Data health research, concerns have risen about privacy and data protection. While the ethical and legal discussion about these issues is ongoing, so is research practice. The aim of this qualitative case study is to gain more insight into how these concerns are currently dealt with in practice. For this multiple-case study, the YOUth cohort, a longitudinal cohort focusing on psychosocial development, and Big Data Psychiatry, a pilot study in Big Data analytics on psychiatric health data, were selected. A broad range of relevant documents were collected and semi-structured interviews with stakeholders were conducted. Data were coded, studied and divided into themes during an iterative analytical process. Three themes emerged: abandoning anonymisation, reconfiguring participant control, and the search for guidance and expertise. Overall, the findings show that it takes considerable effort to take privacy and data protection norms into account in a Big Data health research initiative, especially when individual participant level data need to be linked or enriched. By embracing the complexity of the law in an early phase, setbacks could be prevented, the existing flexibility within the law could be utilised, and systems or organisations could be designed and constructed to take relevant rules into account. Our paper illustrates that a close collaboration of experts with different backgrounds within the initiative may be necessary to be able to successfully navigate this process.

Oral supplementation with Lactobacillus casei subspecies rhamnosus prevents enteric colonization by Candida species in preterm neonates: a randomized study.

BACKGROUND: Colonization by Candida species is the most important predictor of the development of invasive fungal disease in preterm neonates, and the enteric reservoir is a major site of colonization. We evaluated the effectiveness of an orally supplemented probiotic (Lactobacillus casei subspecies rhamnosus; Dicoflor [Dicofarm spa]; 6 x 10(9) cfu/day) in the prevention of gastrointestinal colonization by Candida species in preterm, very low birth weight (i.e., < 1500-g) neonates during their stay in a neonatal intensive care unit. METHODS: Over a 12-month period, a prospective, randomized, blind, clinical trial that involved 80 preterm neonates with a very low birth weight was conducted in a large tertiary neonatal intensive care unit. During the first 3 days of life, the neonates were randomly assigned to receive either an oral probiotic added to human (maternal or pooled donors') milk (group A) or human milk alone (group B) for 6 weeks or until discharge from the NICU, if the neonate was discharged before 6 weeks. On a weekly basis, specimens obtained from various sites (i.e., oropharyngeal, stool, gastric aspirate, and rectal specimens) were collected from all patients for surveillance culture, to assess the occurrence and intensity of fungal colonization in the gastrointestinal tract. RESULTS: The incidence of fungal enteric colonization (with colonization defined as at least 1 positive culture result for specimens obtained from at least 1 site) was significantly lower in group A than in group B (23.1% vs. 48.8%; relative risk, 0.315 [95% confidence interval, 0.120-0.826]; P = .01). The numbers of fungal isolates obtained from each neonate (P = .005) and from each colonized patient (P = .005) were also lower in group A than in group B. L. casei subspecies rhamnosus was more effective in the subgroup of neonates with a birth weight of 1001-1500 g. There were no changes in the relative proportions of the different Candida strains. No adverse effects potentially associated with the probiotic were recorded. CONCLUSIONS: Orally administered L. casei subspecies rhamnosus significantly reduces the incidence and the intensity of enteric colonization by Candida species among very low birth weight neonates.

Fungal and bacterial sepsis and threshold ROP in preterm very low birth weight neonates.

OBJECTIVE: To determine whether an association exists between either fungal or bacterial sepsis and retinopathy of prematurity (ROP). STUDY DESIGN: Retrospective cohort study on all neonates with birth weight <1500 g admitted to a large Italian third Level Neonatal Intensive Care Unit in the years 1997-2001 and screened for ROP. Univariate analysis and multiple logistic regression were used to detect significant associations with ROP (all grades and threshold) in neonates with birth weight<1000 g (extremely low birth weight (ELBW)) and 1000-1500 g. RESULTS: Among 301 enrolled neonates, ROP (all grades), threshold ROP, fungal and bacterial sepsis occurred in 31.9, 12.9, 11.6 and 40.5% of the infants, respectively. At multivariate analysis, only gestational age (P=0.03), colonization by Candida non-albicans spp (P=0.03) and fungal sepsis (P=0.03) were independent predictors of threshold ROP, and only in ELBW neonates. CONCLUSIONS: Fungal (but not bacterial) sepsis is significantly and independently associated with ROP, but only in ELBW neonates and only with threshold ROP.

Identification of the critical region of 12p over-representation in testicular germ cell tumors of adolescents and adults.

Cytogenetically, testicular germ cell tumors of adolescents and adults (TGCTs) are characterized by gain of 12p-sequences, most often through isochromosome formation (i(12p)). Fluorescence in situ hybridization (FISH) has shown that i(12p))-negative TGCTs also cryptically contain extra 12p-sequences. The consistency of 12p-over-representation in all histological subtypes of TGCTs, including their preinvasive stage, suggests that gain of one or more genes on 12p is crucial in the development of this cancer. So far, studies aimed at the identification of the relevant gene(s) were based on the 'candidate-gene approach'. No convincing evidence in favor of or against a particular gene has been reported. We combined conventional karyotyping, comparative genomic hybridization, and FISH to identify TGCTs with amplifications of restricted regions of 12p. Out of 49 primary TGCTs (23 without i(12p), 13 with and 13 unknown), eight tumors (six without i(12p) and two unknown) showed amplifications corresponding to 12p11.1-p12.1. Using bicolour-FISH, physical mapping, and semi-quantitative polymerase chain reactions, the size of the shortest region of overlap of amplification (SROA) was estimated to be between 1750-3000 kb. In addition, we mapped a number of genes in and around this region. While fourteen known genes could be excluded as candidates based on their location outside this region, we demonstrate that KRAS2, JAW1 and SOX5 genes are localized within the SROA. While KRAS2 and JAW1 map to the proximal border of the SROA, SOX5 maps centrally in the SROA. KRAS2 and JAW1 are expressed in all TGCTs, whereas one 12p amplicon-positive TGCT lacks expression of SOX5. The critical region of 12p over-represented in TGCTs is less than 8% of the total length of the short arm of chromosome 12. It will be helpful in the identification of the gene(s) involved in TGCT-development.

Cloning and expression of interleukin-3 genes of chimpanzee and New World monkeys.

Interleukin-3 (IL-3) genes were cloned from chimpanzee (Pan troglodytes), tamarin (Saguinus oedipus) and marmoset (Callithrix jacchus) and expressed in COS cells. Although the IL-3 gene structure is well conserved in these primate species, sequence analysis revealed extensive base substitutions. The chimpanzee IL-3 protein, which is highly homologous (98.5% identity) to human IL-3, stimulated proliferation of human cells dependent on IL-3. In contrast, due to the numerous amino acid substitutions in the New World monkey IL-3 species, no stimulation of human cells was observed, illustrating the extensive evolutionary divergence of IL-3.

Intermittent vs maintenance medication in schizophrenia. Two-year results.

This is a 2-year, double-blind, placebo-controlled study of 101 patients, evaluating the relative efficacy of intermittent medication (given only when the patient shows early signs of relapse) compared with moderate doses of maintenance medication for stable schizophrenic outpatients. Patients were dropped from the study if they had three prodromal episodes in 1 year or if an episode lasted more than 9 weeks. Fourteen percent of patients given maintenance treatment were dropped from the study compared with 46% of intermittently treated patients. Relapse rates were 16% for patients given maintenance treatment and 30% for intermittently treated patients, a nonsignificant difference. Intermittently treated patients were receiving significantly less medication, but there were no differences found in drug side effects. There appears to be no advantage in using the intermittent approach, but we found that the use of an early intervention strategy reduced the relapse and rehospitalization rates for these patients.

Update on the management of Candida infections in preterm neonates.

Invasive fungal infections in preterm neonates in the neonatal intensive care unit are predominantly caused by Candida spp, and have a high burden of morbidity and mortality. Effective prophylactic strategies have recently become available, but the identification of the best possible strategies to manage high-risk infants is still a priority. Choice and use of appropriate antifungal drugs needs careful assessment of neonatal characteristics, the epidemiology and drug pharmacokinetics. Ideally, antifungal drugs for preterm neonates should target fungal bio-films, prevent or effectively treat end-organ localisations, be active against fluconazole-resistant Candida species, and have reliable safety and tolerability profiles. The paper reviews the state-of-the-art in the area of neonatal fungal infections, and addresses some open questions related to the best possible prophylactic and therapeutic strategies to be implemented in such unique patients.

G proteins and regulation of pyruvate dehydrogenase activity by insulin in human circulating lymphocytes.

Pertussis toxin (PT) catalyzes ADP-ribosylation of G protein alpha subunits, thus preventing their role as transducers of external signals targeting metabolic pathways. In vitro, in human circulating lymphocytes insulin at physiological concentrations (5 microU/ml) determines sharp activation of pyruvate dehydrogenase (PDH), the rate limiting enzyme in glucose oxidative breakdown. This study evaluates whether the above-described effects of insulin over PDH are mediated through G proteins. Human circulating lymphocytes (six samples from different donors) were exposed to insulin (5 microU/ml), PT (1-2 micrograms/ml) or PT-9K, a mutated PT void of catalytic activity (1-10 micrograms/ml), and to insulin in combination with the two toxins, and then assessed for PDH activity. Plasma membranes from cells incubated with and without PT or PT-9K were subjected to ADP-ribosylation in the presence of [32P] NAD+ and activated PT. In circulating lymphocytes exposed to PT alone, or in combination with insulin, PDH activity falls significantly below basal values (P < 0.001); PT-9K instead has no effect on basal or on insulin-stimulated PDH activity. ADP-ribosylation of a plasma membrane component with apparent molecular mass (42 kDa) comparable to that of the Gi (inhibitory) protein alpha subunit takes place in cells exposed to PT but not in those exposed to PT-9K. In human circulating lymphocytes Gi proteins or Gi protein-like components appear to be involved in preserving basal PDH activity as well as in the mechanism by which insulin exerts its control over PDH.

Structural and functional characterization of 20S and 26S proteasomes from bovine brain.

Two proteins were isolated, in a stable form, from bovine brain by ion exchange chromatography, gel filtration and ultracentrifugation on glycerol gradient. They were identified as 20S and 26S proteasomes on the basis of molecular mass, migration velocity on non-denaturing gels, immunoreactivity, multipeptidase activity and the 26S proteasome also for dependence on ATP for the degradation of short peptides and ubiquitinylated proteins. However, the 26S proteasome has some properties not yet described for its counterpart of other tissues and from brain of this and other species. In particular, the ATP concentration required by the 26S proteasome to reach maximal peptidase activity was approximately 40-fold lower than the one required for maximal proteolytic activity on polyubiquitinylated substrates. Moreover, plots of substrate concentration vs. velocity gave a saturation curve for the 26S proteasome only, which, for the trypsin-like and post-glutamyl peptide hydrolase activities fitted the Michaelis-Menten equation, whereas for the chymotrypsin-like activity indicated multibinding site kinetics with positive cooperativity (n = 2.32+/-0.38). As concerns the 20S proteasome, its electrophoretic pattern on native gel revealed a single protein band, a feature, to our knowledge, not yet described for the brain particle of any species.

Fluorescence in situ hybridization-based approaches for detection of 12p overrepresentation, in particular i(12p), in cell lines of human testicular germ cell tumors of adults.

Overrepresentation of the short arm of chromosome 12 is frequently detected in human testicular germ cell tumors of adolescents and adults (TGCT). This overrepresentation mostly results from the formation of an isochromosome: i(12p). Whether the overrepresentation consistently involves the complete 12p arm including the centromere is still unclear. We studied five TGCT-derived cell lines (NT2, 2102Ep, H12.1, NCCIT, and S2), combining conventional chromosome banding, fluorescence in situ hybridization (FISH), and comparative genomic hybridization (CGH) to investigate the suitability of each of these techniques to detect aberrations involving chromosome 12. Karyotyping showed one or more i(12p)s in NT2, 2102Ep, H12.1, and S2. However, FISH with a centromere-specific probe (p alpha 12H8), a 12p "paint" and a 12p11.2--p12.1 region-specific probe yeast artificial chromosome (YAC)#5 and CGH could not confirm the presence of an i(12p) in S2. Additional randomly distributed 12p sequences were detected by FISH in H12.1, NCCIT, and S2. In most of these cases, (a part of) the centromere was included. All overrepresented 12p regions, except for those in S2, showed hybridization with YAC#5. CGH showed increased copy numbers of the complete 12p arm in the cell lines with one or more i(12p)s but no overrepresentation was noted in the cell lines without i(12p). In metaphase spreads, the centromeric block of the i(12p)s differed in size as compared with those of normal chromosomes 12. This was rarely noted in interphase nuclei. A decrease in size of the centromeric block in 2102Ep and H12.1 caused a weak FISH signal, which was difficult to detect, especially in interphase nuclei. The ratio between p alpha 12H8- and YAC#5-derived signals reflected the presence or absence of one or more i(12p)s. Our results indicate that double FISH with a centromere- and a 12p-specific probe can be used to detect 12p overrepresentation [including i(12p)] in TGCT both in metaphase spreads and interphase nuclei. CGH confirmed the relative overrepresentation of 12p sequences as detected by FISH and showed that in these cell lines the complete 12p was involved.