An antisense oligonucleotide efficiently suppresses splicing of an alternative exon in vascular smooth muscle in vivo

Targeting alternative exons for therapeutic gain has been achieved in a few instances and potentially could be applied more broadly. The myosin phosphatase (MP) enzyme is a critical hub upon which signals converge to regulate vessel tone. Alternative exon 24 of myosin phosphatase regulatory subunit (Mypt1 E24) is an ideal target as toggling between the two isoforms sets smooth muscle sensitivity to vasodilators such as nitric oxide (NO). This study aimed to develop a gene-based therapy to suppress splicing of Mypt1 E24 thereby switching MP enzyme to the NO-responsive isoform. CRISPR/Cas9 constructs were effective at editing of Mypt1 E24 in vitro; however, targeting of vascular smooth muscle in vivo with AAV9 was inefficient. In contrast, an octo-guanidine conjugated antisense oligonucleotide targeting the 5' splice site of Mypt1 E24 was highly efficient in vivo. It reduced the percent splicing inclusion of Mypt1 E24 from 80% to 10% in mesenteric arteries. The maximal and half-maximal effects occurred at 12.5 and 6.25 mg/kg, respectively. The effect persisted for at least 1 mo without toxicity. This highly effective splice-blocking antisense oligonucleotide could be developed as a novel therapy to reverse vascular dysfunction common to diseases such as hypertension and heart failure.NEW & NOTEWORTHY Alternative exon usage is a major driver of phenotypic diversity in all cell types including smooth muscle. However, the functional significance of most of the hundreds of thousands of alternative exons has not been defined, nor in most cases even tested. If their importance to vascular function were known these alternative exons could represent novel therapeutic targets. Here, we present injection of Vivo-morpholino splice-blocking antisense oligonucleotides as a simple, efficient, and cost-effective method for suppression of alternative exon usage in vascular smooth muscle in vivo.

Depressed Proximal Glycolysis in Myocardium Of Human Heart Failure with Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) accounts for >50% of all heart failure world-wide and remains a major unmet medical need. The most effective recently approved treatments were first developed for diabetes, suggesting metabolic defects are paramount. Myocardial metabolomics in human HFpEF has identified reduced fatty acid and branched chain amino acid catabolism, but the status of glycolysis is unknown. Here we performed targeted metabolomics and protein analysis of glycolytic pathway enzymes in myocardial biopsies of patients with HFpEF versus HF with reduced ejection fraction (HFrEF0 or non-failing controls. Glucose was increased in HFpEF myocardium, but immediate downstream glycolytic metabolites (glucose-6 phosphate, fructose 1,6 diphosphate), were more reduced in HFpEF than the other groups, as were their associated synthetic enzymes hexokinase and phosphofructokinase. Pyruvate was also reduced in HFpEF versus controls. These changes were either not present or substantially less so in HFrEF. Suppression of proximal glycolysis was also coupled to lower metabolites and proteins in the pentose phosphate pathway but was independent of diabetes or obesity. These findings support marked metabolic inflexibility in HFpEF and identifies very proximal blockade in glucose metabolism. Efforts to improve metabolic use of carbohydrates in HFpEF will likely need to target these proximal glycolytic enzymes.

Prospective Observational Study of Bisphosphonate-Related Osteonecrosis of the Jaw in Multiple Myeloma: Microbiota Profiling and Cytokine Expression

PURPOSE

Define incidence and risk factors of osteonecrosis of the jaw (ONJ) and explore oral microbial signatures and host immune response as reflected by cytokine changes in saliva and serum in multiple myeloma (MM) patients on bisphosphate (BP) therapy.

PATIENTS AND METHODS

A single center observational prospective study of MM patients (n = 110) on >2 years of BP, none had ONJ at enrollment. Patients were followed every 3 months for 18 months with clinical/dental examination and serial measurements of inflammatory cytokines, bone turnover markers, and angiogenic growth factors. Oral microbiota was characterized by sequencing of 16S rRNA gene from saliva.

RESULTS

Over the study period 14 patients (13%) developed BRONJ, at a median of 5.7 years (95% CI: 1.9-12.0) from MM diagnosis. Chronic periodontal disease was the main clinically observed risk factor. Oral microbial profiling revealed lower bacterial richness/diversity in BRONJ. Streptococcus intermedius, S. mutans, and S. perioris were abundant in controls; S. sonstellatus and S anginosus were prevalent in BRONJ. In the saliva, at baseline patients who developed BRONJ had higher levels of MIP-1β; TNF-α and IL-6 compared to those without BRONJ, cytokine profile consistent with M-1 macrophage activation. In the serum, patients with BRONJ have significantly lower levels of TGF beta and VEGF over the study period.

CONCLUSION

Periodontal disease associated with low microbial diversity and predominance of invasive species with a proinflammatory cytokine profile leading to tissue damage and alteration of immunity seems to be the main culprit in pathogenesis of BRONJ.

Dominant vector changes during early wavebreak/spiral wave (Wiggers stage 1) in ventricular fibrillation: insights from the analysis of 100 electrophysiology studies

PURPOSE

To describe electrocardiographic vector patterns during early VF transition (Wiggers stage 1).

METHODS

In 100 electrophysiology studies with VF induction, the first 3 beats of VF were analyzed in lead I for left/right axis (LA/RA), V1 for left/right bundle (LB/RB), and aVF for superior/inferior axis (SA/IA). Correlation with demographic/clinical factors was performed using regression analyses and mixed effect modeling.

RESULTS

VF initiated more likely with LA than RA (P < 0.001) and LB than RB (P = 0.04) suggesting original wavebreak in the right ventricle. The 3-dimensional morphology changed in 69% of VF during the first 3 beats, with predominant increase in RB, suggesting a transition of QRS-originating vector to septum/left ventricle. Conservation of morphology (31%) was favored by initial RB (P = 0.002) and LA morphology (P = 0.01). Initiation of VF with LA vs RA was more likely in African-Americans (P = 0.016) and increasing age (P = 0.032). Ischemic cardiomyopathy favored VF initiation with RB 6.7-fold (P = 0.025), possibly linking LV myocardial scar to initial VF wavebreak location. Male gender and ischemic cardiomyopathy prolonged time-to-loss of predominant vector by 119% (P = 0.002) and 71% (P = 0.017), respectively, suggesting more preserved anatomic/functional reentry.

CONCLUSION

The predominant QRS vectors during early Wiggers stage 1 VF are not random and suggest an initial wavebreak more commonly in the right ventricle, followed by a transitional shift to the septum/left ventricle. Ethnicity, male gender, age, and co-morbidities result in directional preservation of initiating VF vectors possibly due to myocardial mass/fibrosis. Findings may allow new treatment/ablation approaches.

P4477Editing of myosin phosphatase as a novel approach for sensitization of vascular smooth muscle to vasodilators (NO/cGMP/ROS) and lowering of blood pressure in hypertension

Background

Despite the many drugs for treatment of hypertension, it remains inadequately treated in >50% of patients and the number one contributor to cardiovascular mortality world-wide. Thus new targets and treatment strategies are badly needed. Myosin Phosphatase (MP) is a viable target: it is the primary effector of vascular smooth muscle relaxation and a critical mediator of signaling pathways regulating vessel tone.

Purpose

We are using complementary/ translatable approaches to test the hypothesis: editing of the Myosin Phosphatase Regulatory (Targeting) subunit (MYPT1), by shifting the expression of naturally occurring isoforms, will sensitize vascular smooth muscle to NO/cGMP/ROS mediated vasorelaxation and thereby lower BP in models of hypertension. A further goal is to determine mechanisms by which these signals activate MP thereby causing vasorelaxation.

Methods

LoxP sites were inserted in introns flanking alternative Exon24 (E24) of Mypt1. Mice were crossed with smMHCCreER mice and treated with Tamoxifen for smooth muscle specific deletion of E24 (SMcKO E24).Skipping E24 codes for a Mypt1 isoform that contains a C-terminal leucine zipper (LZ) motif required for cGMP-dependent protein kinase (cGK1) binding and NO/cGMP/ROS activation of MP. Second, we developed and tested guide RNAs for the purpose of AAV-CRISPR/CAS9 editing of Mypt1 E24 as a treatment for hypertension. Effect of editing is tested in otherwise normal mice and in the AngII sub-pressor model of hypertension.

Results

SMcKO E24 mice had mean BP that was 15+3 mmHg lower than control (n=5; p<0.05). Mesenteric arteries from these mice were significantly more sensitive to DEA/NO mediated relaxation (EC50: 2.1+0.5 nM vs 18.2+5.6 mM; n=5–6, p<0.05). Experiments testing response to AngII infusion are in progress and will be presented at the meeting. Preliminary biochemical assays support a 2-pool model, in which NO/cGMP/ROS activates the LZ+ pool, while contractile agonists inhibit the LZ- pool of MP, in the control of BP/ blood flow. We have generated a number of AAV Crispr/Cas9 gRNAs and validated their efficacy of editing of Mypt1 E24 in vitro. Experiments are in progress to test their efficacy and effect on BP in vivo.

Conclusion

These studies support that editing of Mypt1 E24 could be a novel strategy for vasodilator sensitization and effective lowering of blood pressure in humans with hypertension, thereby having a substantial impact on CV mortality world-wide.

Acknowledgement/Funding

NIH

Neutralizing Antibody-Mediated Response and Risk of BK Virus-Associated Nephropathy

BK virus-associated nephropathy (BKVAN) causes renal allograft dysfunction. The current management of BKVAN relies on pre-emptive adaptation of immunosuppression according to viral load monitoring. However, this empiric strategy is not always successful. Therefore, pretransplant predictive markers are needed. In a prospective longitudinal study, we enrolled 168 kidney transplant recipients and 69 matched donors. To assess the value of BKV genotype-specific neutralizing antibody (NAb) titers as a predictive marker for BKV replication, we measured BKV DNA load and NAb titers at transplant and followed patients for 24 months. After transplant, 52 (31%) patients displayed BKV replication: 24 (46%) patients were viruric and 28 (54%) patients were viremic, including 13 with biopsy-confirmed BKVAN. At any time, patients with high NAb titers against the replicating strain had a lower risk of developing BKV viremia (hazard ratio [HR], 0.44; 95% confidence interval [95% CI], 0.26 to 0.73; P=0.002). Each log₁₀ increase in NAb titer decreased the risk of developing viremia by 56%. Replicating strains were consistent with donor transmission in 95% of cases of early BKV replication. Genotype mismatch between recipients' neutralization profiles before transplant and their subsequently replicating strain significantly increased the risk of developing viremia (HR, 2.27; 95% CI, 1.06 to 4.88; P=0.04). A NAb titer against the donor's strain <4 log₁₀ before transplant significantly associated with BKV replication after transplant (HR, 1.88; 95% CI, 1.06 to 3.45; P=0.03). BKV genotype-specific NAb titers may be a meaningful predictive marker that allows patient stratification by BKV disease risk before and after transplant.

Abstract P501: Editing of Myosin Phosphatase Gene as a Novel Approach for Vasodilator Sensitization and Lowering of Blood Pressure

Myosin Phosphatase (MP) is the primary effector of vascular smooth muscle (VSM) relaxation and a key end target of signaling pathways that regulate vessel tone. Regulated splicing of alternative Exon24 (E24) of Myosin Phosphatase Regulatory/ Targeting subunit (MYPT1) sets vasodilator sensitivity. Skipping E24 codes for a Mypt1 isoform that contains a C-terminal leucine zipper (LZ) motif required for cGK1α binding and NO/cGMP activation of MP resulting in vasodilation. Inclusion of 31 nt E24 shifts the reading frame coding for a Mypt1 isoform with a distinct C-terminus (LZ-) that is unresponsive to NO/cGMP. We are using two editing approaches to test the function of Mypt1 E24 splice variants in the control of BP in vivo. First, LoxP sites were inserted in introns flanking E24, crossed with smMHCCre ER , and treated with Tamoxifen to achieve smooth muscle-specific cKO of E24 (SMcKO E24), thereby converting Mypt1 to the LZ+ isoform. E24 cKO mice had mean BP that was 15 + 3 mmHg lower than control (n=3-5; p<0.05). Mesenteric arteries from these mice were significantly more sensitive to DEA/NO mediated relaxation (EC 50 : 2.1+0.5 nM vs 18.2+5.6 μM; n=5-6, p<0.05). We now are developing CRISPR/CAS9 editing of Mypt1 for translation into humans with hypertension. Guide(g)RNAs targeting E24 were designed using Benchling.com and selected for further study based on predicted efficacy, specificity (>10%,>60%) and cross-species conservation. Plasmids were generated by sub-cloning of oligonucleotides into the parent pX601 plasmid for the purpose of co-expression of gRNA and saCas9. These plasmids were transfected into HEK293 cells singly and in combinations and Mypt1 gene editing assayed by PCR, Surveyor nuclease assays and sequencing of genomic DNA. Single gRNAs yielded deletions of 1-3 nt. Combinations yielded deletions of 104-334 nt that removed >80% of E24 with an efficiency of editing that varied from 10% (gRNAs 6+9 and 5+9) to 40% (gRNAs 6+11 and 5+11). We have now generated AAVgE24 and are testing their efficiency of editing of VSM in vivo. These studies support that AAV mediated CRISPR/Cas9 editing of Mypt1 E24 could be a novel strategy for vasodilator sensitization and effective lowering of blood pressure in humans.

Homogeneous Inflammatory Gene Profiles Induced in Human Dermal Fibroblasts in Response to the Three Main Species of Borrelia burgdorferi sensu lato

In Lyme borreliosis, the skin is the key site for bacterial inoculation by the infected tick and for cutaneous manifestations. We previously showed that different strains of Borrelia burgdorferi sensu stricto isolated from tick and from different clinical stages of the Lyme borreliosis (erythema migrans, and acrodermatitis chronica atrophicans) elicited a very similar transcriptional response in normal human dermal fibroblasts. In this study, using whole transcriptome microarray chips, we aimed to compare the transcriptional response of normal human dermal fibroblasts stimulated by 3 Borrelia burgdorferi sensu lato strains belonging to 3 main pathogenic species (B. afzelii, B. garinii and B. burgdorferi sensu stricto) in order to determine whether “species-related” inflammatory pathways could be identified. The three Borrelia strains tested exhibited similar transcriptional profiles, and no species-specific fingerprint of transcriptional changes in fibroblasts was observed. Conversely, a common core of chemokines/cytokines (CCL2, CXCL1, CXCL2, CXCL6, CXCL10, IL-6, IL-8) and interferon-related genes was stimulated by all the 3 strains. Dermal fibroblasts appear to play a key role in the cutaneous infection with Borrelia, inducing a homogeneous inflammatory response, whichever Borrelia species was involved.

Comparison between a Broad-Range Real-Time and a Broad-Range End-Point PCR Assays for the Detection of Bacterial 16S rRNA in Clinical Samples

Broad range PCR targeting the 16S rRNA gene is widely used to test clinical samples for the presence of bacterial DNA. End-point 16S PCR is both time-consuming and at high risk of cross-contamination. Prior to the replacement of the 16S end-point PCR assay routinely used in our clinical laboratory by a new 16S real-time PCR assay, we aimed to compare the performances of both techniques for the direct diagnosis of bacterial infections in clinical samples. In this prospective study, 129 clinical samples were included for direct comparison of both techniques. The sensitivity of 16S real-time PCR assay (76%) was significantly higher than that of end-point 16S PCR assay (41%) (p<0.01). Specificities of both PCR assays did not differ significantly (p=0.43). The 16S real-time PCR assay yielded an etiological diagnosis in 19% of culture-negative samples. It constitutes a reliable and complementary diagnostic tool to the bacterial culture.

Increased urinary type II collagen C-telopeptide levels in Tunisian patients with knee osteoarthritis

Osteoarthritis is characterized by a progressive degeneration of articular cartilage and loss of joint function. Clinical assessment of osteoarthritis is hampered by the lack of accurate measures of disease and disease progression, especially during the early stage.

BACKGROUND

To investigate urinary C-telopeptide fragments of type II collagen (CTX-II) levels in knee osteoarthritis in the Tunisian population compared with controls and to assess the association between this biomarker and radiological signs.

METHODS

One hundred and twenty five female patients with knee osteoarthritis, aged 53.6 +/- 7.6 years with disease duration of 3.6 +/- 3.8 years and 57 female age-matched controls underwent Lyon Schuss X-ray exams. Two experienced readers independently measured the joint space width (JSW) and classified each knee for severity using the Kellgren/Lawrence scale. The urinary concentration of CTX-II was measured by a competitive ELISA.

RESULTS

The levels of urinary CTX-II were significantly higher in knee osteoarthritis patients compared with controls (323.98 vs 218.04 microg/mol creatinine). A weak and non significant association between the CTX-II level and JSW was found. The significant correlations were observed between age and CTX-II in both groups and between BMI and CTX-II only in controls.

CONCLUSIONS

Analysis of CTX-II in urine samples of Tunisian patients with knee osteoarthritis provided a sensitive method to detect increased degradation of collagen type II in patients with osteoarthritis.

Monosomy 10q26-qter and trisomy 11q13-qter as a result of de novo unbalanced translocation

A male infant with partial monosomy 10 q and partial trisomy 11q as a result of de novo unbalanced translocation between the long arms of chromosomes 10 and 11: der(10)t(10;11)(q26;q13) is described. He had craniofacial dysmorphy, congenital heart defects, urogenital and cerebral anomalies, and severe developmental delay. To the best of our knowledge, this is the first report of this combination of chromosomal abnormalities.

Chromosomal abnormalities in liver cell dysplasia detected by comparative genomic hybridisation

BACKGROUND/AIM

The pathogenetic relation between liver cell dysplasia and hepatocellular carcinoma (HCC) is poorly understood. The aim of this study was to determine whether there is a genetic link between liver cell dysplasia and HCC that could support the role of dysplasia as a tumour precursor lesion.

METHODS

Microdissection from paraffin wax embedded sections and degenerate oligonucleotide primed polymerase chain reaction (DOP-PCR) were combined to analyse chromosomal imbalances by comparative genomic hybridisation (CGH) in nine HCCs and nodules containing liver cell dysplasia and cirrhosis adjacent to the tumours. Seven cases of large cell changes (LCC) and three cases of small cell changes (SCC) were analysed. The genetic abnormalities detected in liver cell dysplasia were then compared with those present in the corresponding HCC.

RESULTS

No abnormalities were detected in LCC and cirrhotic nodules, arguing against the preneoplasic nature of these cell foci. In contrast, a subset of chromosomal alterations present in HCCs was found in the adjacent SCC.

CONCLUSIONS

These findings support the preneoplastic status of SCC in human hepatocarcinogenesis.

Molecular characterization and phylogenetic analysis of a human T cell leukemia virus type 2 strain from French Guiana

Extensive studies have been carried out on native Amerindian populations living in French Guiana in an attempt to detect human T cell leukemia virus type 2 (HTLV-2). However, the first strain of this virus identified in this region was not detected in these populations, but in a Brazilian woman of Amerindian origin. Comparative analyses of the nucleotide sequences of 589 bp of the gp21 env gene and of 625 bp of the long terminal repeat (LTR) showed that this new HTLV-2 strain (HTLV-2 GUY) was of subtype A. Sequence comparison and phylogenetic analyses demonstrated that HTLV-2 GUY was closely related to a group of distinct variants of HTLV-2 subtype A strains originating mostly from Brazilian inhabitants and formerly called HTLV-2 subtype C. As there is a high level of immigration from Brazil in French Guiana, we carried out a seroepidemiological study of 175 Brazilians, mostly women (obtained from a serum databank) and 72 female Brazilian prostitutes living in French Guiana to determine whether HTLV-2 is likely to become an emerging infection in this area. No HTLV-2 infection was detected, indicating that this virus is unlikely to become prevalent in the near future.

Distinct chromosomal abnormality pattern in primary liver cancer of non-B, non-C patients

To discriminate among the chromosomal abnormalities associated with the etiology of hepatocellular carcinoma (HCC), we performed a comparative genomic hybridization (CGH) analysis on 34 HCCs resected on non-cirrhotic livers from patients serologically negative for both hepatitis B (HBV) and C (HCV) viruses. The results were compared to those of a previous analysis of 50 HCCs selected on the basis of their positivity for HBV infection. The majority of the abnormalities found in the HBV positive cases (losses of chromosome arms 1p, 8p, 6q, 13q and 14q and gains of 1q, 8q, 6p and 17q) were similarly detected in the virus negative specimens. In contrast, a significant decrease (40% on average) was observed for losses at 4q, 16q and 17p in non-viral HCC samples, suggesting that these abnormalities are tightly associated with HBV infection. Thus, in addition to a common pathway towards malignancy, a subset of alterations may preferentially contribute to virus-induced carcinogenesis. In a parallel CGH study of 10 fibrolamellar carcinomas, a rare subtype of HCC, we found in six out of the seven informative cases, gains of chromosome arm 1q. This region, which is also preferentially amplified in non fibrolamellar tumors (58%), may contain an essential proto-oncogene commonly implicated in liver carcinogenesis.

Effect of TT virus infection on hepatocellular carcinoma development: results of a Euro-Asian survey

A small percentage of persons with hepatocellular carcinoma (HCC) lack identifiable causes of liver pathology. The single-stranded DNA virus, TT virus (TTV), has been found in persons with acute and chronic liver injury. Nested polymerase chain reaction was used to search for both TTV and parvoviruses in 293 HCC samples from Asia and Europe. TTV was found in >30% of Chinese and Italian samples but in only 13% of French samples. No clinicopathologic differences were found between TTV-positive and -negative populations. A significant association was found between TTV infection and hepatitis B virus (P<.01) and herpesviruses (P<.02) in HCC patients, suggesting that factors promoting these infections are associated with enhanced TTV positivity. Parvovirus B19 and adeno-associated virus were found in only 7.5% of the tumors. Taken together, these data suggest that TTV infection is unlikely to be associated with the induction or acceleration of the hepatocarcinogenic process in humans.

Gain of chromosome arm 17q and adverse outcome in patients with neuroblastoma

BACKGROUND

Gain of genetic material from chromosome arm 17q (gain of segment 17q21-qter) is the most frequent cytogenetic abnormality of neuroblastoma cells. This gain has been associated with advanced disease, patients who are > or =1 year old, deletion of chromosome arm 1p, and amplification of the N-myc oncogene, all of which predict an adverse outcome. We investigated these associations and evaluated the prognostic importance of the status of chromosome 17.

METHODS

We compiled molecular cytogenetic analyses of chromosome 17 in primary neuroblastomas in 313 patients at six European centers. Clinical and survival information were collected, along with data on 1p, N-myc, and ploidy.

RESULTS

Unbalanced gain of segment 17q21-qter was found in 53.7 percent of the tumors, whereas the chromosome was normal in 46.3 percent. The gain of 17q was characteristic of advanced tumors and of tumors in children > or =1 year of age and was strongly associated with the deletion of 1p and amplification of N-myc. No tumor showed amplification of N-myc in the absence of either deletion of 1p or gain of 17q. Gain of 17q was a significant predictive factor for adverse outcome in univariate analysis. Among the patients with this abnormality, overall survival at five years was 30.6 percent (95 percent confidence interval, 21 to 40 percent), as compared with 86.0 percent (95 percent confidence interval, 78 to 91 percent) among those with normal 17q status. in multivariate analysis, gain of 17q was the most powerful prognostic factor, followed by the presence of stage 4 disease and deletion of 1p (hazard ratios, 3.4, 2.3, and 1.9, respectively).

CONCLUSIONS

Gain of chromosome segment 17q21-qter is an important prognostic factor in children with neuroblastoma.

Comparative genomic hybridization analysis of sporadic neuroendocrine tumors of the digestive system

Little information is available on the molecular mechanisms underlying neuroendocrine tumorigenesis. To obtain an overview of the genomic imbalances characterizing these tumors, we studied 20 benign or malignant sporadic endocrine gastroenteropancreatic tumors by comparative genomic hybridization. Chromosomal imbalances were found in all tumors. Gains of chromosomal material were more frequent than losses. The most frequent gains were of chromosomes and chromosome arms 5 (55%), 14 (55%), 17q (55%), and 7 (50%). Losses were most frequent from 11q (30%) and 16p (30%). Gains of chromosome 5 did not occur in nonmetastatic tumors, whereas losses of 9p were observed exclusively in intestinal tumors. In addition, we found two high-level amplifications, of 17q11-21 and 19q13. A complementary FISH analysis revealed that the gain in 17q11-21 included amplification of the protooncogene HER2/neu. As in multiple endocrine neoplasia type-1-associated tumors, deletions of chromosome band 11q13 appear to be involved in the development of sporadic digestive tract neuroendocrine tumors, but our results suggest that other chromosomal regions are also involved.

Overrepresentation of 7q31 and 17q in renal cell carcinomas

Xenografts from four metastatic renal cell carcinomas (RCCs) were established in immunodeficient mice. All tumors exhibited cytogenetic features specific for the papillary subtype, namely, partial or total polysomy of chromosomes 7 and 17 and integrity of 3p. Cytogenetic analysis of the initial and xenografted tumors indicated that although clonal characteristics were consistently maintained in xenografts derived from metastases, a minor clone had been selected for in the xenografts derived from the primary tumors. Reverse painting and comparative genomic hybridization (CGH) allowed us to localize minimal overrepresented genomic regions to 7q31, where the MET protooncogene is located, and to 17q. Other overrepresented regions were 8q in all xenografts and Xq22-qter in three of them. The gain of genetic material from these regions may be a key factor ensuring the papillary nature of RCCs and their survival in xenografts.

Comparative genomic hybridization analysis of sporadic neuroendocrine tumors of the digestive system

Little information is available on the molecular mechanisms underlying neuroendocrine tumorigenesis. To obtain an overview of the genomic imbalances characterizing these tumors, we studied 20 benign or malignant sporadic endocrine gastroenteropancreatic tumors by comparative genomic hybridization. Chromosomal imbalances were found in all tumors. Gains of chromosomal material were more frequent than losses. The most frequent gains were of chromosomes and chromosome arms 5 (55%), 14 (55%), 17q (55%), and 7 (50%). Losses were most frequent from 11q (30%) and 16p (30%). Gains of chromosome 5 did not occur in nonmetastatic tumors, whereas losses of 9p were observed exclusively in intestinal tumors. In addition, we found two high-level amplifications, of 17q11-21 and 19q13. A complementary FISH analysis revealed that the gain in 17q11-21 included amplification of the protooncogene HER2/neu. As in multiple endocrine neoplasia type-1-associated tumors, deletions of chromosome band 11q13 appear to be involved in the development of sporadic digestive tract neuroendocrine tumors, but our results suggest that other chromosomal regions are also involved.

Recurrent chromosomal abnormalities in hepatocellular carcinoma detected by comparative genomic hybridization

Comparative genomic hybridization (CGH) was used to evaluate and map genomic aberrations in 50 hepatocellular carcinomas (HCCs) from patients chronically infected with hepatitis B virus (HBV). CGH clearly detected nonrandom genomic imbalances. Losses were most prevalent on chromosome regions 4q (70%), 8p (65%), 16q (54%), 17p (51%), 13q and 6q (37% each), and lp (30%). The most frequent gains occurred on 8q (60%), 1q (58%), and 6p and 17q (33% each). In a few cases, sequence amplifications were detected that were mapped to bands 11q12, 12p11, 14q12, and 19q13.1. This study represents the first analysis of primary liver cancers by CGH, and it confirms the presence of previously known chromosomal aberrations in HCC and highlights new quantitative abnormalities and sequence amplifications. These findings should lead to the characterization of new loci involved in liver cancer pathogenesis.

Emergence and scattering of multiple neurofibromatosis (NF1)-related sequences during hominoid evolution suggest a process of pericentromeric interchromosomal transposition

Type 1 neurofibromatosis (NF1) gene encodes for a member of the GTPase activating protein family and is considered to be a tumor suppressor gene. Its very high rate of de novo mutation in humans led us to study a specific feature of this gene: the presence of numerous NF1-related sequences. According to our results, the human genome contains at least 11 NF1-related sequences, nine of which are scattered near centromeric sequences of seven different chromosomes. These NF1-related sequences, whose extent is quite varied according to loci, are unprocessed copies of the NF1 gene, and bear numerous mutations. A phylogenetic analysis of the six largest sequences indicates that they are all derived from a common ancestor, which would have appeared 22-33 million years ago, and was subsequently duplicated several times during hominoid evolution. The most recent duplication and interchromosomal transposition occurred in the last million years suggesting that the process could still be ongoing. Intriguing similarities between the evolution of alpha-satellite DNA and NF1-related sequences suggest the involvement of a common genetic mechanism for the generation and pericentric spreading of these NF1 partial copies.

Additional copies of a 25 Mb chromosomal region originating from 17q23.1-17qter are present in 90% of high-grade neuroblastomas

Neuroblastoma shows remarkable heterogeneity, ranging from spontaneous regression to progression toward highly malignant tumors. In search of genetic abnormalities that could explain this variability, we have characterized neuroblastoma tumors by using multiple fluorescent hybridizations. Our results indicate that chromosome 17 is rearranged very frequently in the form of unbalanced translocations with numerous chromosomal partners, all leading to the presence of supernumerary copies of a 25 Mb chromosomal region originating from 17q23.1-qter. Additional 17q material was detected in more than 90% of untreated high-grade neuroblastomas and, along with 1p36 deletion, should represent the most frequent genetic abnormality of neuroblastoma observed until now.

Assignment of the NTRK4 (trkE) gene to chromosome 6p21

Reverse transcriptase-polymerase chain reactions using foetal brain RNA with reverse and forward primers of the first, second and third NTRK4 region allowed us to obtain three amplified NTRK4 fragments. The specificity of amplified fragments was checked by digestion with restriction endonucleases AvrII, HindIII and PspII for the first, second and third regions, respectively. Each restriction site was specific for each amplified fragment. The fragment of the NTRK4 first region was also sequenced and the sequence determined was identical to the human NTRK4 sequence. The three amplified fragments were cloned in pBS. For the Southern technique, plasmid pBS-NTRK4a (with an insert of 1052 bp) detected a human 9-kb HindIII sequence which was localised unambiguously on chromosome 6. For fluorescence in situ hybridisation, the three plasmids, pBS-NTRK4a, pBS-NTRK4b (insert 924 bp) and pBS-NTRK4c (insert 1114 bp) were pooled and used as a probe. This NTRK4 probe was localised on 6p21. Of 50 metaphases analysed, 49 contained twin spot signals on both sister chromatids.

MDM2 amplification in a primary alveolar rhabdomyosarcoma displaying a t(2;13)(q35;q14)

This report describes a case of rhabdomyosarcoma associated with a 2;13 translocation and multiple double minute chromosomes. The origin of the amplified DNA was identified using comparative genomic hybridization, which pinpointed a unique spot at 12q13-->q14. Band 12q13 has been shown to contain several genes that are occasionally amplified in other sarcomas. Fluorescene in situ hybridization to tumor metaphases with probes specific for this region indicated that the double minutes contained the MDM2 gene but not the CDK4 gene. MDM2 amplification was further quantified by Southern hybridization, which showed a mean value of 25 copies per haploid genome. This is the first example of MDM2 amplification in a rhabdomyosarcoma.