Sequential genomic analysis using a multisample/multiplatform approach to better define rhabdomyosarcoma progression and relapse

The genomic spectrum of rhabdomyosarcoma (RMS) progression from primary to relapse is not fully understood. In this pilot study, we explore the sensitivity of various targeted and whole-genome NGS platforms in order to assess the best genomic approach of using liquid biopsy in future prospective clinical trials. Moreover, we investigate 35 paired primary/relapsed RMS from two contributing institutions, 18 fusion-positive (FP-RMS) and 17 fusion-negative RMS (FN-RMS) by either targeted DNA or whole exome sequencing (WES). In 10 cases, circulating tumor DNA (ctDNA) from multiple timepoints through clinical care and progression was analyzed for feasibility of liquid biopsy in monitoring treatment response/relapse. ctDNA alterations were evaluated using a targeted 36-gene custom RMS panel at high coverage for single-nucleotide variation and fusion detection, and a shallow whole-genome sequencing for copy number variation. FP-RMS have a stable genome with relapse, with common secondary alterations CDKN2A/B, MYCN, and CDK4 present at diagnosis and impacting survival. FP-RMS lacking major secondary events at baseline acquire recurrent MYCN and AKT1 alterations. FN-RMS acquire a higher number of new alterations, most commonly SMARCA2 missense mutations. ctDNA analyses detect pathognomonic variants in all RMS patients within our collection at diagnosis, regardless of type of alterations, and confirmed at relapse in 86% of FP-RMS and 100% FN-RMS. Moreover, a higher number of fusion reads is detected with increased disease burden and at relapse in patients following a fatal outcome. These results underscore patterns of tumor progression and provide rationale for using liquid biopsy to monitor treatment response.

Bypassing the Need for Cell Permeabilization: Nanobody CDR3 Peptide Improves Binding on Living Bacteria

Membrane interaction constitutes to be an essential parameter in the mode of action of entities such as proteins, as well as cell-penetrating and antimicrobial peptides, resulting in noninvasive or lytic activities depending on the membrane compositions and interactions. Recently, a nanobody able to interact with the top priority, multidrug-resistant bacterial pathogen Acinetobacter baumannii was discovered, although binding took place with fixed cells only. To potentially overcome this limitation, linear peptides corresponding to the complementarity-determining regions (CDR) were synthesized and fluorescently labeled. Microscopy data indicated clear membrane interactions of the CDR3 sequence with living A. baumannii cells, indicating both the importance of the CDR3 as part of the parent nanobody paratope and the improved binding ability and thus avoiding the need for permeabilization of the cells. In addition, cyclization of the peptide with an additionally introduced rigidifying 1,2,3-triazole bridge retains its binding ability while proteolytically protecting the peptide. Overall, this study resulted in the discovery of novel peptides binding a multidrug-resistant pathogen.

Targeted long-read sequencing of the Ewing sarcoma 6p25.1 susceptibility locus identifies germline-somatic interactions with EWSR1-FLI1 binding

Ewing sarcoma (EwS) is a rare bone and soft tissue malignancy driven by chromosomal translocations encoding chimeric transcription factors, such as EWSR1-FLI1, that bind GGAA motifs forming novel enhancers that alter nearby expression. We propose that germline microsatellite variation at the 6p25.1 EwS susceptibility locus could impact downstream gene expression and EwS biology. We performed targeted long-read sequencing of EwS blood DNA to characterize variation and genomic features important for EWSR1-FLI1 binding. We identified 50 microsatellite alleles at 6p25.1 and observed that EwS-affected individuals had longer alleles (>135 bp) with more GGAA repeats. The 6p25.1 GGAA microsatellite showed chromatin features of an EWSR1-FLI1 enhancer and regulated expression of RREB1, a transcription factor associated with RAS/MAPK signaling. RREB1 knockdown reduced proliferation and clonogenic potential and reduced expression of cell cycle and DNA replication genes. Our integrative analysis at 6p25.1 details increased binding of longer GGAA microsatellite alleles with acquired EWSR-FLI1 to promote Ewing sarcomagenesis by RREB1-mediated proliferation.

Oral Etoposide and Trastuzumab Use for HER2-Positive Metastatic Breast Cancer: A Retrospective Study from the Institut Curie Hospitals

BACKGROUND

The TOP2A and ERBB2 genes are co-amplified in about 40% of HER2 positive (HER2+) breast cancers. Oral etoposide (VP16), an inhibitor of topoisomerase-II (encoded by TOP2A), has demonstrated clinical activity in metastatic breast cancer (MBC). The benefit of oral VP16 combined with trastuzumab (VP16-T) in HER2+ MBC has not yet been evaluated.

METHODS

Patients treated at the Institut Curie Hospitals with VP16-T for HER2+ MBC were retrieved by an in silico search. Progression-free survival (PFS), overall survival (OS), response rate, prolonged PFS (defined as at least 6 months), clinical benefit, and toxicity were assessed. The co-amplification of ERBB2 and TOP2A was assessed by shallow whole genome sequencing on tumor tissue whenever available.

RESULTS

Forty-three patients received VP16-T after a median number of six prior treatment lines for HER2+ MBC. Median PFS and OS were 2.9 months (95% CI [2.4-4.7]) and 11.3 months (95% CI [8.3-25.0]), respectively. Three patients had a complete response, while 12/40 (30%) experienced clinical benefit. Only three patients stopped treatment for toxicity. Seven (35%) patients displayed a TOP2A/ERBB2 co-amplification. No statistically significant correlation was found between outcome and TOP2A/ERBB2 co-amplification.

CONCLUSION

Our analysis suggests a favorable efficacy and toxicity profile for VP16-T in patients with heavily pretreated HER2+ MBC.

Germline MBD4 Mutations and Predisposition to Uveal Melanoma

Background

Uveal melanoma (UM) arises from malignant transformation of melanocytes in the uveal tract of the eye. This rare tumor has a poor outcome with frequent chemo-resistant liver metastases. BAP1 is the only known predisposing gene for UM. UMs are generally characterized by low tumor mutation burden, but some UMs display a high level of CpG>TpG mutations associated with MBD4 inactivation. Here, we explored the incidence of germline MBD4 variants in a consecutive series of 1093 primary UM case patients and a series of 192 UM tumors with monosomy 3 (M3).

Methods

We performed MBD4 targeted sequencing on pooled germline (n = 1093) and tumor (n = 192) DNA samples of UM patients. MBD4 variants (n = 28) were validated by Sanger sequencing. We performed whole-exome sequencing on available tumor samples harboring MBD4 variants (n = 9). Variants of unknown pathogenicity were further functionally assessed.

Results

We identified 8 deleterious MBD4 mutations in the consecutive UM series, a 9.15-fold (95% confidence interval = 4.24-fold to 19.73-fold) increased incidence compared with the general population (Fisher exact test, P = 2.00 × 10^–5, 2-sided), and 4 additional deleterious MBD4 mutations in the M3 cohort, including 3 germline and 1 somatic mutations. Tumors carrying deleterious MBD4 mutations were all associated with high tumor mutation burden and a CpG>TpG hypermutator phenotype.

Conclusions

We demonstrate that MBD4 is a new predisposing gene for UM associated with hypermutated M3 tumors. The tumor spectrum of this predisposing condition will likely expand with the addition of MBD4 to diagnostic panels. Tumors arising in such a context should be recognized because they may respond to immunotherapy.

Low-frequency variation near common germline susceptibility loci are associated with risk of Ewing sarcoma

BACKGROUND

Ewing sarcoma (EwS) is a rare, aggressive solid tumor of childhood, adolescence and young adulthood associated with pathognomonic EWSR1-ETS fusion oncoproteins altering transcriptional regulation. Genome-wide association studies (GWAS) have identified 6 common germline susceptibility loci but have not investigated low-frequency inherited variants with minor allele frequencies below 5% due to limited genotyped cases of this rare tumor.

METHODS

We investigated the contribution of rare and low-frequency variation to EwS susceptibility in the largest EwS genome-wide association study to date (733 EwS cases and 1,346 unaffected controls of European ancestry).

RESULTS

We identified two low-frequency variants, rs112837127 and rs2296730, on chromosome 20 that were associated with EwS risk (OR = 0.186 and 2.038, respectively; P-value < 5×10-8) and located near previously reported common susceptibility loci. After adjusting for the most associated common variant at the locus, only rs112837127 remained a statistically significant independent signal (OR = 0.200, P-value = 5.84×10-8).

CONCLUSIONS

These findings suggest rare variation residing on common haplotypes are important contributors to EwS risk.

IMPACT

Motivate future targeted sequencing studies for a comprehensive evaluation of low-frequency and rare variation around common EwS susceptibility loci.

Abstract A13: Genome-wide association study identifies multiple new loci associated with Ewing sarcoma susceptibility

Ewing sarcoma (EWS), a pediatric tumor predominantly occurring in children of European ancestry, is characterized by the EWSR1-FLI1 fusion oncogene. We performed a genome-wide association study (GWAS) of 749 EWS cases and 1,378 unaffected individuals of European ancestry. Our study replicated previously reported susceptibility loci at 1p36.22, 10q21.3, and 15q15.1 and identified new loci at 6p25.1, 8q24.23, 20p11.22, and 20p11.23 (P-values &lt;5x10-8). Effect estimates exhibited odds ratios (ORs) in excess of 1.7, which is high for cancer GWAS, and striking in light of the rarity of EWS cases in familial cancer syndromes. In expression quantitative trait locus (eQTL) analyses, we observed altered expression patterns for plausible candidate genes at 6p25.1 with RREB1, a RAS-responsive element, and at 20p11.23 with KIZ, a centrosomal stabilization protein. The 20p11.22 locus is also near NKX2-2, a highly overexpressed gene in EWS. Interestingly, most loci reside near GGAA repeat sequences where binding of the EWSR1-FLI1 fusion protein occurs. The seven EWS susceptibility loci discovered in only 749 cases make EWS one of the most productive GWAS studied cancers when considering a locus-to-case discovery ratio. The substantive estimated ORs suggest a distinctive underlying genetic architecture for EWS in which moderate-risk SNPs likely constitute a significant fraction and may interact with EWSR1-FLI1 binding.

Citation Format: Mitchell J. Machiela, Thomas G.P. Grünewald, Didier Surdez, Stephanie Reynaud, Olivier Mirabeau, Eric Karlins, Rebeca Alba Rubio, Sakina Zaidi, Sandrine Grossetete-Lalami, Stelly Ballet, Eve Lapouble, Valérie Laurence, Jean Michon, Gaelle Pierron, Heinrich Kovar, Nathalie Gaspar, Udo Kontny, Anna González-Neira, Piero Picci, Javier Alonso, Ana Patino-Garcia, Nadège Corradini, Neal D. Freedman, Nathaniel Rothman, Casey L. Dagnall, Laurie Burdett, Kristine Jones, Michelle Manning, Kathleen Wyatt, Weiyin Zhou, Meredith Yeager, David G. Cox, Robert N. Hoover, Javed Khan, Gregory T. Armstrong, Wendy M. Leisenring, Smita Bhatia, Leslie L. Robison, Uta Dirksen, Markus Metzler, Wolfgang Hartmann, Konstantin Strauch, Thomas Kirchner, Andreas E. Kulozik, Lindsay M. Morton, Lisa Mirabello, Margaret A. Tucker, Franck Tirode, Stephen Chanock, Olivier Delattre. Genome-wide association study identifies multiple new loci associated with Ewing sarcoma susceptibility [abstract]. In: Proceedings of the AACR Special Conference: Pediatric Cancer Research: From Basic Science to the Clinic; 2017 Dec 3-6; Atlanta, Georgia. Philadelphia (PA): AACR; Cancer Res 2018;78(19 Suppl):Abstract nr A13.

Abstract 2970: Multiple new susceptibility loci identified in genome-wide association study of Ewing sarcoma

Ewing sarcoma (EWS) is a rare pediatric tumor predominantly occurring in children of European ancestry and is characterized by the pathognomonic EWSR1-FLI1 fusion oncogene. To identify germline susceptibility loci associated with EWS risk, we performed a genome-wide association study (GWAS) meta-analysis of 749 EWS cases and 1,378 unaffected individuals of European ancestry from sample collections within the Institut Curie, National Cancer Institute and the Childhood Cancer Survivor Study. Our study replicated previously reported susceptibility loci at 1p36.22, 10q21.3 and 15q15.1 as well as identified novel loci at 6p25.1, 8q24.23, 20p11.22 and 20p11.23 (P-values&lt;5×10-8). These seven EWS susceptibility loci discovered in only 749 cases make EWS one of the most productive GWAS studied cancers when considering a locus to case discovery ratio. All estimated effect estimates were high for cancer GWAS with odds ratios in excess of 1.7 observed. These high per allele effects among relatively common germline variants are striking in light of the rarity of EWS cases and lack of evidence of EWS as part of a familial cancer syndrome and therefore suggest a distinctive genetic architecture for EWS. Interestingly, in silico bioinformatics analysis identified that most EWS susceptibility loci reside near GGAA nucleotide repeat sequences where binding of the EWSR1-FLI1 fusion protein occurs. ChIP-seq analyses confirmed in vivo binding of EWSR1-FLI1, suggesting germline variation in these regions could alter EWSR1-FLI1 binding and potentially deregulate neighboring genes. To identify genes with allele specific expression differences, we carried out expression quantitative trait locus (eQTL) analyses at each identified EWS susceptibility locus. We identified eQTLs for plausible candidate genes at 6p25.1 with RREB1, a RAS-responsive element, and at 20p11.23 with KIZ, a centrosomal stabilization protein. We also noted the 20p11.22 locus is near NKX2-2, a highly overexpressed gene in EWS, although no eQTL was observed in our expression data. Furthermore, knockdown of EWSR1-FLI1 in EWS cell lines indicated a more than 2-fold difference in expression of RREB1 and NKX2-2, further supporting the role of specific regulation of these genes by EWSR1-FLI1 and suggesting RREB1 and NKX2-2 may be transcription factors involved in core regulatory circuitries of EWS. Overall, our study suggests a distinctive underlying genetic architecture for EWS in which moderate risk common germline variants interact with EWSR1-FLI1 binding to alter expression of nearby target genes.

Citation Format: Mitchell J. Machiela, Thomas G. Grünewald, Didier Surdez, Stephanie Reynaud, Olivier Mirabeau, Eric Karlins, Rebeca Alba Rubio, Sakina Zaidi, Sandrine Grossetete-Lalami, Stelly Ballet, Eve Lapouble, Valérie Laurence, Jean Michon, Gaelle Pierron, Heinrich Kovar, Nathalie Gaspar, Udo Kontny, Anna González-Neira, Piero Picci, Javier Alonso, Ana Patino-Garcia, Nadège Corradini, Neal D. Freedman, Nathaniel Rothman, Casey L. Dagnall, Laurie Burdette, Kristine Jones, Michelle Manning, Kathleen Wyatt, Weiyin Zhou, Meredith Yeager, David G. Cox, Robert N. Hoover, Javed Khan, Gregory T. Armstrong, Wendy M. Leisenring, Smita Bhatia, Leslie L. Robison, Uta Dirksen, Markus Metzler, Wolfgang Hartmann, Konstantin Strauch, Thomas Kirchner, Andreas E. Kulozik, Lindsay M. Morton, Lisa Mirabello, Margaret A. Tucker, Franck Tirode, Stephen J. Chanock, Olivier Delattre. Multiple new susceptibility loci identified in genome-wide association study of Ewing sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2970.

Rapid construction of substituted 3-amino-1,5-benzothiazepin-4(5H)-one dipeptide scaffolds through an Ugi-4CR - Ullmann cross-coupling sequence

A 3-step methodology for the synthesis of 1,5-benzothiazepin-4(5H)-one dipeptidomimetics has been elaborated via an Ugi-4CR followed by a S-trityl deprotection and an intramolecular Cu(i)-catalyzed Ullmann condensation with moderate to good yields. In silico and NMR conformational studies showed that the lowest energy conformers stabilize γ- and β-turn structures.

Efficient one-pot synthesis of amino-benzotriazolodiazocinone scaffolds via catalyst-free tandem Ugi-Huisgen reactions

Herein we describe a catalyst-free, one-pot procedure employing an Ugi-4CR between propargyl glycine, functionalised 2-azidoanilines, different isocyanides and aldehydes, followed by a thermal azide-alkyne Huisgen cycloaddition to generate a 14-member set of amino-benzotriazolodiazocine-bearing dipeptides with multiple points of diversification and high atom economy. These structures were derivatized by means of Suzuki-Miyaura cross-coupling reactions at two positions with good to excellent yields, leading to conformationally constrained tricyclic structures. In silico and NMR conformational analysis studies demonstrated that turn conformations are adopted by these structures.

SMARCA4 inactivation defines a group of undifferentiated thoracic malignancies transcriptionally related to BAF-deficient sarcomas

While investigating cohorts of unclassified sarcomas by RNA sequencing, we identified 19 cases with inactivation of SMARCA4, which encodes an ATPase subunit of BAF chromatin-remodeling complexes. Clinically, the cases were all strikingly similar, presenting as compressive mediastino-pulmonary masses in 30- to 35-year-old adults with a median survival time of 7 months. To help define the nosological relationships of these tumors, we compared their transcriptomic profiles with those of SMARCA4-mutated small-cell carcinomas of the ovary, hypercalcemic type (SCCOHTs), SMARCB1-inactivated malignant rhabdoid tumors (MRTs) and lung carcinomas (of which 10% display SMARCA4 mutations). Gene profiling analyses demonstrated that these tumors were distinct from lung carcinomas but related to MRTs and SCCOHTs. Transcriptome analyses, further validated by immunohistochemistry, highlighted strong expression of SOX2, a marker that supports the differential diagnosis of these tumors from SMARCA4-deficient lung carcinomas. The prospective recruitment of cases confirmed this new category of 'SMARCA4-deficient thoracic sarcomas' as readily recognizable in clinical practice, providing opportunities to tailor their therapeutic management.

Efficient synthesis of conformationally constrained, amino-triazoloazepinone-containing di- and tripeptides via a one-pot Ugi-Huisgen tandem reaction

Herein we describe a catalyst-free procedure employing an Ugi-4CR between a β-azido-α-amino acid, propargylamine, an isocyanide and an aldehyde, followed by a thermal azide-alkyne Huisgen cycloaddition to generate a 16-member library of amino-triazoloazepinone-bearing di- and tripeptides with up to four points of diversification and high atom economy.

Oxidative α,ω-diyne coupling as an approach towards novel peptidic macrocycles

The Glaser–Hay diyne coupling proved to be an efficient cyclisation approach towards diyne containing peptidic macrocycles.

Common variants near TARDBP and EGR2 are associated with susceptibility to Ewing sarcoma

Ewing sarcoma, a pediatric tumor characterized by EWSR1-ETS fusions, is predominantly observed in populations of European ancestry. We performed a genome-wide association study (GWAS) of 401 French individuals with Ewing sarcoma, 684 unaffected French individuals and 3,668 unaffected individuals of European descent and living in the United States. We identified candidate risk loci at 1p36.22, 10q21 and 15q15. We replicated these loci in two independent sets of cases and controls. Joint analysis identified associations with rs9430161 (P = 1.4 × 10(-20); odds ratio (OR) = 2.2) located 25 kb upstream of TARDBP, rs224278 (P = 4.0 × 10(-17); OR = 1.7) located 5 kb upstream of EGR2 and, to a lesser extent, rs4924410 at 15q15 (P = 6.6 × 10(-9); OR = 1.5). The major risk haplotypes were less prevalent in Africans, suggesting that these loci could contribute to geographical differences in Ewing sarcoma incidence. TARDBP shares structural similarities with EWSR1 and FUS, which encode RNA binding proteins, and EGR2 is a target gene of EWSR1-ETS. Variants at these loci were associated with expression levels of TARDBP, ADO (encoding cysteamine dioxygenase) and EGR2.

Impact of EWS-ETS Fusion Type on Disease Progression in Ewing's Sarcoma/Peripheral Primitive Neuroectodermal Tumor: Prospective Results From the Cooperative Euro-E.W.I.N.G. 99 Trial

Purpose

EWS-ETS fusion genes are the driving force in Ewing's sarcoma pathogenesis. Because of the variable breakpoint locations in the involved genes, there is heterogeneity in fusion RNA and protein architecture. Since previous retrospective studies suggested prognostic differences among patients expressing different EWS-FLI1 fusion types, the impact of fusion RNA architecture on disease progression and relapse was studied prospectively within the Euro-E.W.I.N.G. 99 clinical trial.

Patients and Methods

Among 1,957 patients who registered before January 1, 2007, 703 primary tumors were accessible for the molecular biology study. Fusion type was assessed by polymerase chain reaction on frozen (n = 578) or paraffin-embedded materials (n = 125). The primary end point was the time to disease progression or relapse.

Results

After exclusion of noninformative patients, 565 patients were entered into the prognostic factor analysis comparing type 1 (n = 296), type 2 (n = 133), nontype 1/nontype 2 EWS-FLI1 (n = 91) and EWS-ERG fusions (n = 45). Median follow-up time was 4.5 years. The distribution of sex, age, tumor volume, tumor site, disease extension, or histologic response did not differ between the four fusion type groups. We did not observe any significant prognostic value of the fusion type on the risk of progression or relapse. The only slight difference was that the risk of progression or relapse associated with nontype 1/nontype 2 EWS-FLI1 fusions was 1.38 (95% CI, 0.96 to 2.0) times higher than risk associated with other fusion types, but it was not significant (P = .10).

Conclusion

In contrast to retrospective studies, the prospective evaluation did not confirm a prognostic benefit for type 1 EWS-FLI1 fusions.

Bradykinin analogs containing the 4-amino-2-benzazepin-3-one scaffold at the C-terminus

High affinity peptide ligands for the bradykinin (BK) B(2) subtype receptor have been shown to adopt a beta-turn conformation of the C-terminal tetrapeptide (H-Arg(1)-Pro(2)-Pro(3)-Gly(4)-Phe(5)-Ser(6)-Pro(7)-Phe(8)-Arg(9)-OH). We investigated the replacement of the Pro(7)-Phe(8) dipeptide moiety in BK or the D-Tic(7)-Oic(8) subunit in HOE140 (H-D-Arg(0)-Arg(1)-Pro(2)-Hyp(3)-Gly(4)-Thi(5)-Ser(6)-D-Tic(7)-Oic(8)-Arg(9)-OH) by 4-amino-1,2,4,5-tetrahydro-2-benzazepin-3-one templates (Aba). Binding studies to the human B(2) receptor showed a correlation between the affinities of the BK analogs and the propensity of the templates to adopt a beta-turn conformation. The L-spiro-Aba-Gly containing HOE140 analog BK10 has the best affinity, which correlates with the known turn-inducing property of this template. All the compounds did not modify basal inositolphosphate (IP) output in B(2)-expressing CHO cells up to 10 microM concentration. The antagonist properties were confirmed by the guinea pig ileum smooth muscle contractility assay. The new amino-benzazepinone (Aba) substituted BK analogs were found to be surmountable antagonists.

Incidence and prognostic value of tumour cells detected by RT-PCR in peripheral blood stem cell collections from patients with Ewing tumour

To retrospectively evaluate the incidence of tumour cell contamination of peripheral blood stem cell (PBSC) collections and to correlate these data with the clinical outcome after high-dose chemotherapy (HDCT) with stem cell rescue in patients with a high-risk Ewing tumour. Peripheral blood stem cell collections obtained from 171 patients were analysed. Tumour contamination was assessed by reverse transcriptase–polymerase chain reaction (RT–PCR). The files of 88 patients who underwent HDCT followed by PBSC reinfusion were reviewed in detail, and their outcome compared to the PBSC RT–PCR results. Seven of 88 PBSC collections (8%) contained tumour cells as detected by RT–PCR. Peripheral blood stem cells were collected after a median of five cycles of chemotherapy. No clinical factor predictive of tumour cell contamination of PBSC harvest could be identified. Event-free survival (EFS) and overall survival (OS) of the whole study population were 45.3 % and 51.8 % at 3 years from the date of the graft, respectively. Forty-five patients relapsed with a median time of 15 months after graft, only four of whom had tumour cell contamination of the PBSC harvest. Tumour cell contamination of PBSC collection is rare and does not seem to be associated with a significantly poorer EFS or OS in this high-risk population.

Synthesis and biological evaluation of constrained analogues of the opioid peptide H-Tyr-D-Ala-Phe-Gly-NH2 using the 4-amino-2-benzazepin-3-one scaffold

The synthesis of conformationally restricted dipeptidic moieties 4-amino-1,2,4,5-tetrahydro-2-benzazepin-3-one (Aba)-Gly ([(4S)-amino-3-oxo-1,2,4,5-tetrahydro-1H-2-benzazepin-2-yl]-acetic acid) and 8-hydroxy-4-amino-1,2,4,5-tetrahydro-2-benzazepin-3-one (Hba)-D-Ala ([(4S)-amino-8-hydroxy-3-oxo-1,2,4,5-tetrahydro-benzo[c]azepin-2-yl]-propionic acid) was based on a synthetic strategy that uses an oxazolidinone as an N-acyliminium precursor. Introducing these Aba scaffolds into the N-terminal tetrapeptide of dermorphin (H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2)-induced remarkable shifts in affinity and selectivity towards the opioid mu- and delta-receptors. This paper provides the synthesis and biological in vitro and in vivo evaluation of constricted analogues of the N-terminal tetrapeptide H-Tyr-D-Ala-Phe-Gly-NH2, which is the minimal subunit of dermorphin needed for dermorphin-like opiate activity.

Expression and G-protein coupling of mu-opioid receptors in the spinal cord and dorsal root ganglia of polyarthritic rats

Although chronic inflammatory pain is known to be associated with hypersensitivity to mu opioid receptor agonists, no evidence for changes in the expression and/or characteristics of central mu opioid receptors has yet been reported in relevant models of this type of pain. In the present study, both immunohistochemical and autoradiographic approaches were used to address this question in polyarthritic rats, on the 4th week after intradermal injection of complete Freund's adjuvant, when inflammatory pain was at its maximum. Immunohistochemical labeling with specific anti-mu opioid receptor antibodies and autoradiographic labeling with [3H]DAMGO showed an upregulation of mu opioid receptors in the dorsal root ganglia but no changes in the density of these receptors in the dorsal horn at the level of L4-L6 segments in polyarthritic compared to age-paired control rats. On the other hand, autoradiographic quantification of the concentration-dependent increase in [35S]GTP-gamma-S binding by the mu-opioid receptor agonist DAMGO did not show any significant differences within the lumbar dorsal horn between polyarthritic and control rats. These data indicate that chronic inflammatory pain caused by polyarthritis was associated with an increased expression of mu-opioid receptors in dorsal root ganglion sensory neurones that did not result in an increased spinal density of these receptors, in spite of their well established axonal transport in the central portion of primary afferent fibres to the dorsal horn. In contrast, axonal transport of mu-opioid receptors in the peripheral portion of these fibres probably accounts for the increased receptor density in inflamed tissues already reported in the literature.

The TXP motif in the second transmembrane helix of CCR5. A structural determinant of chemokine-induced activation

CCR5 is a G-protein-coupled receptor activated by the chemokines RANTES (regulated on activation normal T cell expressed and secreted), macrophage inflammatory protein 1alpha and 1beta, and monocyte chemotactic protein 2 and is the main co-receptor for the macrophage-tropic human immunodeficiency virus strains. We have identified a sequence motif (TXP) in the second transmembrane helix of chemokine receptors and investigated its role by theoretical and experimental approaches. Molecular dynamics simulations of model alpha-helices in a nonpolar environment were used to show that a TXP motif strongly bends these helices, due to the coordinated action of the proline, which kinks the helix, and of the threonine, which further accentuates this structural deformation. Site-directed mutagenesis of the corresponding Pro and Thr residues in CCR5 allowed us to probe the consequences of these structural findings in the context of the whole receptor. The P84A mutation leads to a decreased binding affinity for chemokines and nearly abolishes the functional response of the receptor. In contrast, mutation of Thr-82(2.56) into Val, Ala, Cys, or Ser does not affect chemokine binding. However, the functional response was found to depend strongly on the nature of the substituted side chain. The rank order of impairment of receptor activation is P84A > T82V > T82A > T82C > T82S. This ranking of impairment parallels the bending of the alpha-helix observed in the molecular simulation study.

The novel analgesic, cizolirtine, inhibits the spinal release of substance P and CGRP in rats

Although previous studies have established that cizolirtine (5-([(N,N-dimethylaminoethoxy)phenyl]methyl)-1-methyl-1H-pyrazol citrate) is a potent analgesic in rodents, its mechanism(s) of action remain(s) unclear. In vitro and in vivo approaches were used to assess whether cizolirtine could affect the spinal release of two pain-related neuropeptides, substance P (SP) and calcitonin gene-related peptide (CGRP), in rats. Cizolirtine significantly reduced the K(+)-evoked overflow of both the SP-like material (SPLM; -25% at 0.1 microM--0.1 mM) and CGRPLM (-20% at 0.1--1.0 microM) from slices of the dorsal half of the lumbar enlargement of the spinal cord. Intrathecal perfusion in halothane-anaesthetized rats showed that local application of cizolirtine markedly diminished the spinal outflow of SPLM (up to -50% at 0.1 mM) but only marginally that of CGRPLM. Systemic administration of cizolirtine at an analgesic dose (80 mg/kg i.p.) also reduced spinal SPLM outflow (-50%) but not that of CGRPLM. Under both in vitro and in vivo conditions, idazoxan (10 microM) antagonized the effects of cizolirtine on SPLM and CGRPLM release, suggesting their mediation through alpha(2) adrenoceptors.

Muscarinic and PACAP receptor interactions at pontine level in the rat: significance for REM sleep regulation

Cholinergic and PACAPergic systems within the oral pontine reticular nucleus (PnO) play a critical role in REM sleep generation in rats. In this present work, we have investigated whether REM sleep enhancement induced by carbachol (a cholinergic agonist) or PACAP, depends on an interaction between muscarinic and PACAP receptors. This hypothesis was tested by recording sleep-wake cycles in freely moving rats injected into the PnO with PACAP in combination with the muscarinic receptor antagonist atropine, or with carbachol in combination with the PACAP receptor antagonist PACAP6-27. When administered alone, PACAP (3 pmol) or carbachol (110 pmol) induced an enhancement of REM sleep during 8 h (+61%, n = 8; +70%, n = 5), which was totally prevented by infusion of atropine (290 pmol) for PACAP, or of PACAP6-27 (3 pmol) for carbachol. Quantitative autoradiographic studies indicated that (i) PACAP (10-9-10-7 M) induced in the PnO an increase (+35%) of the specific binding of the muscarinic antagonist [3H]quinuclidinyl benzylate, which could be completely prevented by PACAP6-27 (IC50 = 8 x 10-8 M) and (ii) both carbachol and PACAP enhanced [35S]GTP-gamma-S binding in a concentration-dependent manner in the PnO. The maximal increase due to carbachol was significantly higher in the presence (+126%) than in the absence (+102%) of PACAP (0.1 microM). These data showed that interactions between muscarinic and PACAP receptors do exist within the PnO and play a role in the local mechanisms of REM sleep control in the rat.

Altered opioid-mediated control of the spinal release of dynorphin and met-enkephalin in polyarthritic rats

Previous studies showed that spinal opioidergic neurotransmission is markedly altered in the polyarthritic rat, a model of chronic inflammatory pain. Present investigations aimed at assessing possible changes in opioid-mediated control of the spinal outflow of met-enkephalin (ME) and dynorphin (DYN) in these animals. Intrathecal (i.t.) perfusion under halothane anesthesia showed that polyarthritis was associated with both a 40% decrease in the spinal outflow of ME-like material (MELM) and a 90% increase in that of DYNLM. Local treatment with the mu-opioid agonist DAGO (10 microM i.t.) inhibited equally (-30%) the MELM outflow in polyarthritic and control rats, whereas the delta agonist DTLET (10 microM i.t.) also reduced the peptide outflow in controls (-27%) but enhanced it in polyarthritic animals (+56%). On the other hand, both DAGO (10 microM i.t.) and DTLET (10 microM i.t.) decreased (-40 and -49%) DYNLM outflow in polyarthritic rats, but were inactive in controls. Finally, neither MELM outflow nor that of DYNLM were affected by the kappa-agonist U50488H (10 microM i.t.) in both groups of rats. In all cases, the changes due to active agonists could be prevented by specific antagonists which were inactive on their own except the kappa antagonist nor-binaltorphimine (10 microM i.t.) that decreased (-38%) DYNLM outflow in polyarthritic rats. These data indicate that functional changes in spinal opioid receptors may promote enkephalinergic neurotransmission and reduce dynorphinergic neurotransmission in polyarthritic rats, thereby contributing to the analgesic efficacy of opioids in inflammatory pain.

The neuropeptide FF analogue, 1DME, enhances in vivo met-enkephalin release from the rat spinal cord

Behavioural studies have suggested that endogenous opioids mediate the antinociceptive action of neuropeptide FF (FLFQPQRF-NH2) at the spinal level in the rat. This hypothesis was directly assessed by investigating the effects of a NPFF analogue, 1DMe ([D-Tyr1,(NMe)Phe3]NPFF), on the spinal outflow of met-enkephalin-like material (MELM) in halothane-anaesthetised rats. Intrathecal infusion (0.1 ml/min) of 1DMe (0.1 microM-0.1 mM, for 45 min) produced a concentration-dependent increase in spinal MELM outflow which persisted for at least 90 min at the highest concentration tested. Intrathecal coadministration of the micro-opioid receptor antagonist CTOP (1 microM) did not significantly affect the spinal MELM overflow due to 0.1 mM 1DMe. In contrast, both naltrindole and nor-binaltorphimine, at concentrations (10 microM) that allow the selective blockade of alpha- and kappa-opioid receptors, respectively, significantly reduced the stimulatory effect of 1DMe on spinal MELM outflow. These data provide the first direct demonstration that met-enkephalin (among other opioid peptides) can mediate the antinociceptive action of NPFF at the spinal level in rats. In addition, they suggest that reciprocal excitatory interactions between opioids and opioid-modulatory factors (such as NPFF) participate in the physiological control of nociception.

Polyarthritis-associated changes in the opioid control of spinal CGRP release in the rat

As a model of chronic inflammatory pain, Freund's adjuvant-induced polyarthritis has been shown to be associated with marked alterations in the activity of opioid- and calcitonin gene-related peptide (CGRP)-containing neurons in the dorsal horn of the spinal cord in rats. Possible changes in the interactions between these two peptidergic systems in chronic inflammatory pain were investigated by comparing the effects of various opioid receptor ligands on the spinal outflow of CGRP-like material (CGRPLM) in polyarthritic and age-paired control rats. Intrathecal perfusion of an artificial cerebrospinal fluid in halothane-anaesthetized animals allowed the collection of CGRPLM released from the spinal cord and the application of opioid receptor ligands. The blockade of kappa-opioid receptors similarly increased CGRPLM release in both groups of rats as expected of a kappa-mediated tonic inhibitory control of CGRP-containing fibres in control, as well as in polyarthritic rats. In contrast, the higher increase in CGRPLM outflow due to the preferential blockade of mu opioid receptors by naloxone in polyarthritic rats as compared to non-suffering animals supports the idea of a reinforced mu opioid receptor-mediated tonic inhibitory control of CGRP-containing fibres in rats suffering from chronic pain. Even more strikingly, the differences observed in the effects of delta-opioid receptor ligands on CGRPLM outflow suggest that delta receptors are functionally shifted from a participation in a phasic excitatory control in non-suffering rats to a tonic inhibitory control in polyarthritic rats. These data indicate that agonists acting at the three types of opioid receptors all exert a tonic inhibitory influence on CGRP-containing nociceptive primary afferent fibres within the spinal cord of polyarthritic rats. Such a convergence probably explains why morphine and other opioids are especially potent to reduce pain in subjects suffering from chronic inflammatory diseases.

Enkephalinergic and dynorphinergic neurons in the spinal cord and dorsal root ganglia of the polyarthritic rat - in vivo release and cDNA hybridization studies

Complex and contradictory data have been reported regarding the changes in spinal opioidergic systems associated with chronic inflammatory pain in the rat. In an attempt to solve these discrepancies, the in vivo release of met-enkephalin and dynorphin and the expression of the corresponding propeptide genes were investigated at the spinal level in arthritic rats and paired controls. A dramatic increase in the concentration of prodynorphin mRNA (+300-550%) and a less pronounced elevation of that of dynorphin-like material (+40-50%) were found in the dorsal part of cervical and lumbar segments of the spinal cord in rats rendered arthritic by an intradermal injection of Freund's adjuvant four weeks prior to these measurements. In addition, the spinal release of dynorphin-like material (assessed through an intrathecal perfusion procedure in halothane-anaesthetized animals) was approximately twice as high in arthritic rats as in controls. In spite of significant elevations in the levels of both met-enkephalin (+30-70%) and proenkephalin A mRNA (+40-50%) in the dorsal part of cervical and lumbar segments, the spinal release of met-enkephalin-like material was decreased (-50%) in arthritic rats as compared to paired controls. Proenkephalin A mRNA (but not prodynorphin mRNA) could be measured in dorsal root ganglia, and its levels were dramatically reduced in ganglia at the lumbar segments in arthritic rats. Such parallel reductions in the spinal release of met-enkephalin-like material and the levels of proenkephalin A mRNA in dorsal root ganglia of arthritic rats support the idea that the activity of primary afferent enkephalinergic fibres decreases markedly during chronic inflammatory pain.