CRISPR single base-editing: in silico predictions to variant clonal cell lines

Engineering single base edits using CRISPR technology including specific deaminases and single-guide RNA (sgRNA) is a rapidly evolving field. Different types of base edits can be constructed, with cytidine base editors (CBEs) facilitating transition of C-to-T variants, adenine base editors (ABEs) enabling transition of A-to-G variants, C-to-G transversion base editors (CGBEs) and recently adenine transversion editors (AYBE) that create A-to-C and A-to-T variants. The base-editing machine learning algorithm BE-Hive predicts which sgRNA and base editor combinations have the strongest likelihood of achieving desired base edits. We have used BE-Hive and TP53 mutation data from The Cancer Genome Atlas (TCGA) ovarian cancer cohort to predict which mutations can be engineered, or reverted to wild-type (WT) sequence, using CBEs, ABEs or CGBEs. We have developed and automated a ranking system to assist in selecting optimally designed sgRNA that considers the presence of a suitable protospacer adjacent motif (PAM), the frequency of predicted bystander edits, editing efficiency and target base change. We have generated single constructs containing ABE or CBE editing machinery, an sgRNA cloning backbone and an enhanced green fluorescent protein tag (EGFP), removing the need for co-transfection of multiple plasmids. We have tested our ranking system and new plasmid constructs to engineer the p53 mutants Y220C, R282W and R248Q into WT p53 cells and shown that these mutants cannot activate four p53 target genes, mimicking the behaviour of endogenous p53 mutations. This field will continue to rapidly progress, requiring new strategies such as we propose to ensure desired base-editing outcomes.

Three-Dimensional Modelling of Ovarian Cancer: From Cell Lines to Organoids for Discovery and Personalized Medicine

Ovarian cancer has the highest mortality of all of the gynecological malignancies. There are several distinct histotypes of this malignancy characterized by specific molecular events and clinical behavior. These histotypes have differing responses to platinum-based drugs that have been the mainstay of therapy for ovarian cancer for decades. For histotypes that initially respond to a chemotherapeutic regime of carboplatin and paclitaxel such as high-grade serous ovarian cancer, the development of chemoresistance is common and underpins incurable disease. Recent discoveries have led to the clinical use of PARP (poly ADP ribose polymerase) inhibitors for ovarian cancers defective in homologous recombination repair, as well as the anti-angiogenic bevacizumab. While predictive molecular testing involving identification of a genomic scar and/or the presence of germline or somatic BRCA1 or BRCA2 mutation are in clinical use to inform the likely success of a PARP inhibitor, no similar tests are available to identify women likely to respond to bevacizumab. Functional tests to predict patient response to any drug are, in fact, essentially absent from clinical care. New drugs are needed to treat ovarian cancer. In this review, we discuss applications to address the currently unmet need of developing physiologically relevant in vitro and ex vivo models of ovarian cancer for fundamental discovery science, and personalized medicine approaches. Traditional two-dimensional (2D) in vitro cell culture of ovarian cancer lacks critical cell-to-cell interactions afforded by culture in three-dimensions. Additionally, modelling interactions with the tumor microenvironment, including the surface of organs in the peritoneal cavity that support metastatic growth of ovarian cancer, will improve the power of these models. Being able to reliably grow primary tumoroid cultures of ovarian cancer will improve the ability to recapitulate tumor heterogeneity. Three-dimensional (3D) modelling systems, from cell lines to organoid or tumoroid cultures, represent enhanced starting points from which improved translational outcomes for women with ovarian cancer will emerge.

An organotypic model of high-grade serous ovarian cancer to test the anti-metastatic potential of ROR2 targeted Polyion complex nanoparticles

High-grade serous ovarian cancer (HGSOC) is the most lethal gynaecological malignancy. Most patients are diagnosed at late stages when the tumour has metastasised throughout the peritoneal cavity. The Wnt receptor ROR2 has been identified as a promising therapeutic target in HGSOC, with limited targeting therapeutic options currently available. Small interfering RNA (siRNA)-based therapeutics hold great potential for inhibiting the function of specific biomarkers, however major challenges remain in efficient delivery and stability. The aim of this study was to investigate the ability of nanoparticles to deliver ROR2 siRNA into HGSOC cells, including platinum resistant models, and estimate the anti-metastatic effect via a 3D organotypic model for ovarian cancer. The nanoparticles were generated by conjugating poly[2-(dimethylamino) ethyl methacrylate] (PDMAEMA) of various chain length to bovine serum albumin (BSA), followed by the condensation of ROR2 siRNA into polyplexes, also termed polyion complex (PIC) nanoparticles. The toxicity and uptake of ROR2 siRNA PIC nanoparticles in two HGSOC cell lines, CaOV3 as well as its cisplatin resistant pair (CaOV3CisR), in addition to primary cells used for the 3D organotypic model were investigated. ROR2 knockdown at both transcriptional and translational levels were evaluated via real-time PCR and western blot analysis, respectively. Following 24 h incubation with the nanoparticles, functional assays were performed including proliferation (IncuCyte S3), transwell migration and 3D co-cultured transwell invasion assays. The PICs nanoparticles exhibited negligible toxicity in the paired CaOV3 cell lines or primary cells. Treating CaOV3 and CaOV3CisR cells with ROR2 siRNA containing PICs nanoparticles significantly inhibited migration and invasion ability. The biocompatible ROR2 siRNA conjugated PICs nanoparticles provide an innovative therapeutic option. ROR2 targeting therapy shows potential in treating HGSOC including platinum resistant forms.

PARP Inhibitors Display Differential Efficacy in Models of BRCA Mutant High-Grade Serous Ovarian Cancer

Several poly (adenosine diphosphate-ribose) polymerase (PARP) inhibitors are now in clinical use for tumours with defects in BReast CAncer genes BRCA1 or BRCA2 that result in deficient homologous recombination repair (HRR). Use of olaparib, niraparib or rucaparib for the treatment of high-grade serous ovarian cancer, including in the maintenance setting, has extended both progression free and overall survival for women with this malignancy. While different PARP inhibitors (PARPis) are mechanistically similar, differences are apparent in their chemical structures, toxicity profiles, PARP trapping abilities and polypharmacological landscapes. We have treated ovarian cancer cell line models of known BRCA status, including the paired cell lines PEO1 and PEO4, and UWB1.289 and UWB1.289+BRCA1, with five PARPis (olaparib, niraparib, rucaparib, talazoparib and veliparib) and observed differences between PARPis in both cell viability and cell survival. A cell line model of acquired resistance to veliparib showed increased resistance to the other four PARPis tested, suggesting that acquired resistance to one PARPi may not be able to be rescued by another. Lastly, as a proof of principle, HRR proficient ovarian cancer cells were sensitised to PARPis by depletion of BRCA1. In the future, guidelines will need to emerge to assist clinicians in matching specific PARPis to specific patients and tumours.

Abstract 1062: Inhibition of ovarian and endometrial cancer cell proliferation by an anti-ROR1 monoclonal antibody

The non-canonical Wnt signalling receptor ROR1 has been shown to be aberrantly expressed in numerous cancers, including ovarian and endometrial cancer (EC). Cirmtuzumab is a humanised monoclonal antibody against ROR1 that blocks Wnt5a-induced ROR1 signalling. It has demonstrated safety and efficacy in several Phase I/II clinical trials for chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL) and Her2-negative breast cancer. The aim of this study was to investigate any anti-proliferative effect of cirmtuzumab in combination with commonly-used gynaecological cancer therapies (cisplatin, paclitaxel and the PARP inhibitor, olaparib) on high grade serous ovarian cancer (HGSOC) and EC cell lines including models of platinum resistance. The ROR1 positive HGSOC cells lines CaOV3, CaOV3CisR PEO1, PEO4 and EC cell lines Ishikawa, KLE were used in this study. First, IC50 for cisplatin, paclitaxel and olaparib in each cell line at 72h was determined using the cell counting kit 8 (CCK-8). Then, cells were seeded in 12-well plates and treated with cirmtuzumab at 25µg/ml or 50µg/ml for 4h prior to the addition of the chemotherapeutic agents at IC70 concentration. The effect of cirmtuzumab +/- agents was quantified using the IncuCyte S3 Live Cell Analysis System. Phase contrast cell images were obtained using a 10x objective lens within the instrument every 3h for 72h in total. The average confluence of each well was calculated and normalised against the baseline (time 0). Two-way ANOVA followed by Bonferroni post-test was performed to evaluate the effect of treatments. RNA and protein were extracted at the end of the incubation for qRTPCR and Western blot analysis. Single dose cirmtuzumab at both 25µg/ml and 50µg/ml significantly inhibited proliferation of CaOV3, CaOV3cisR, PEO1 and Ishikawa cells. 50µg/ml of cirmtuzumab decreased proliferation of KLE. Compared to paclitaxel alone, addition of 50µg/ml of cirmtuzumab significantly inhibited proliferation of CaOV3, CaOV3CisR, PEO1 and PEO4. Compared to cisplatin alone, addition of 25µg/ml of cirmtuzumab significantly inhibited proliferation of CaOV3CisR, PEO4; addition of 50µg/ml of cirmtuzumab significantly inhibited proliferation of CaOV3, CaOV3CisR, PEO4. Compared to olaparib alone, addition of 25µg/ml of cirmtuzumab significantly inhibited proliferation of CaOV3CisR; addition of 50µg/ml of cirmtuzumab significantly inhibited proliferation of CaOV3 and CaOV3CisR. No significant change in ROR1 or ROR2 expression levels was observed following cirmtuzumab treatment, however treatment did result in alterations to markers of epithelial-mesenchymal transition (EMT). Cirmtuzumab alone inhibited proliferation of ovarian cancer and EC cells in vitro, and could enhance the activity of commonly-used chemotherapeutic agents. This study supports the potential of cirmtuzumab or other ROR1 targeting therapies for treating women with HGSOC and EC.

Citation Format: Dongli Liu, Gunnar F. Kaufmann, James B. Breitmeyer, Kristie-Ann Dickson, Deborah J. Marsh, Caroline E. Ford. Inhibition of ovarian and endometrial cancer cell proliferation by an anti-ROR1 monoclonal antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1062.

Ubiquitin chromatin remodelling after DNA damage is associated with the expression of key cancer genes and pathways

Modification of the cancer-associated chromatin landscape in response to therapeutic DNA damage influences gene expression and contributes to cell fate. The central histone mark H2Bub1 results from addition of a single ubiquitin on lysine 120 of histone H2B and is an important regulator of gene expression. Following treatment with a platinum-based chemotherapeutic, there is a reduction in global levels of H2Bub1 accompanied by an increase in levels of the tumor suppressor p53. Although total H2Bub1 decreases following DNA damage, H2Bub1 is enriched downstream of transcription start sites of specific genes. Gene-specific H2Bub1 enrichment was observed at a defined group of genes that clustered into cancer-related pathways and correlated with increased gene expression. H2Bub1-enriched genes encompassed fifteen p53 target genes including PPM1D, BTG2, PLK2, MDM2, CDKN1A and BBC3, genes related to ERK/MAPK signalling, those participating in nucleotide excision repair including XPC, and genes involved in the immune response and platinum drug resistance including POLH. Enrichment of H2Bub1 at key cancer-related genes may function to regulate gene expression and influence the cellular response to therapeutic DNA damage.

Histone Monoubiquitination in Chromatin Remodelling: Focus on the Histone H2B Interactome and Cancer

Chromatin remodelling is a major mechanism by which cells control fundamental processes including gene expression, the DNA damage response (DDR) and ensuring the genomic plasticity required by stem cells to enable differentiation. The post-translational modification of histone H2B resulting in addition of a single ubiquitin, in humans at lysine 120 (K120; H2Bub1) and in yeast at K123, has key roles in transcriptional elongation associated with the RNA polymerase II-associated factor 1 complex (PAF1C) and in the DDR. H2Bub1 itself has been described as having tumour suppressive roles and a number of cancer-related proteins and/or complexes are recognised as part of the H2Bub1 interactome. These include the RING finger E3 ubiquitin ligases RNF20, RNF40 and BRCA1, the guardian of the genome p53, the PAF1C member CDC73, subunits of the switch/sucrose non-fermenting (SWI/SNF) chromatin remodelling complex and histone methyltransferase complexes DOT1L and COMPASS, as well as multiple deubiquitinases including USP22 and USP44. While globally depleted in many primary human malignancies, including breast, lung and colorectal cancer, H2Bub1 is selectively enriched at the coding region of certain highly expressed genes, including at p53 target genes in response to DNA damage, functioning to exercise transcriptional control of these loci. This review draws together extensive literature to cement a significant role for H2Bub1 in a range of human malignancies and discusses the interplay between key cancer-related proteins and H2Bub1-associated chromatin remodelling.

Writing Histone Monoubiquitination in Human Malignancy-The Role of RING Finger E3 Ubiquitin Ligases

There is growing evidence highlighting the importance of monoubiquitination as part of the histone code. Monoubiquitination, the covalent attachment of a single ubiquitin molecule at specific lysines of histone tails, has been associated with transcriptional elongation and the DNA damage response. Sites function as scaffolds or docking platforms for proteins involved in transcription or DNA repair; however, not all sites are equal, with some sites resulting in actively transcribed chromatin and others associated with gene silencing. All events are written by E3 ubiquitin ligases, predominantly of the RING (really interesting new gene) finger type. One of the most well-studied events is monoubiquitination of histone H2B at lysine 120 (H2Bub1), written predominantly by the RING finger complex RNF20-RNF40 and generally associated with active transcription. Monoubiquitination of histone H2A at lysine 119 (H2AK119ub1) is also well-studied, its E3 ubiquitin ligase constituting part of the Polycomb Repressor Complex 1 (PRC1), RING1B-BMI1, associated with transcriptional silencing. Both modifications are activated as part of the DNA damage response. Histone monoubiquitination is a key epigenomic event shaping the chromatin landscape of malignancy and influencing how cells respond to DNA damage. This review discusses a number of these sites and the E3 RING finger ubiquitin ligases that write them.

Abstract A06: Cisplatin-induced DNA damage modifies the chromatin landscape of histone H2B monoubiquitination in a p53-dependent manner

Post-translational modifications (PTMs) of histone tails can function as epigenomic regulators of the cellular response to DNA damage. Monoubiquitination of histone H2B at lysine 120 (H2Bub1) is a central histone PTM involved in the DNA damage response. H2Bub1 localizes to double-strand breaks where it functions to decondense chromatin, making it accessible to DNA repair factors. H2Bub1 is also known to be enriched at coding sequences of highly expressed genes, demonstrating the fundamental importance of H2Bub1 for an open chromatin structure that facilitates transcription. H2Bub1 is a dynamic process, written predominantly by the E3 ubiquitin ligase complex of the ring finger proteins RNF20 and RNF40 and erased by multiple deubiquitinases, including those from the ubiquitin-specific peptidase subfamily USP7 and USP44. RNF20 is reported to interact with p53. Platinum drugs are used as standard-of-care for the treatment of high-grade serous ovarian cancer (HGSOC) based on their capacity to damage DNA. We sought to determine the response of ubiquitinated histone tails to a platinum drug with the goal of improving the efficacy of current best practice therapy for HGSOC.

Following treatment of a wild-type p53 cell line with an IC75 dose of cisplatin, we combined H2Bub1 chromatin immunoprecipitation with massively parallel sequencing (ChIP-seq) to determine genomic enrichment of H2Bub1 in response to DNA damage. Further, we coupled this with RNA-seq (RNA sequencing) to enable correlation of genomic enrichment of H2Bub1 with levels of gene expression. KEGG pathway and gene ontology analyses demonstrated greatest H2Bub1 enrichment in response to DNA damage in p53 signalling pathway genes, including CDKN1A, BBC3, MDM2 and BAX. This correlated with increased expression of p53 target genes in response to DNA damage. Wild-type TP53 itself did not show H2Bub1 enrichment upon treatment with cisplatin.

H2Bub1 ChIP experiments were repeated in HGSOC mutant p53 cell line models, specifically OVCAR-3 with the known gain-of-function TP53 mutation R248Q and Kuramochi with the missense TP53 mutation D281Y. H2Bub1 was not enriched in response to DNA damage at wild-type p53 gene targets in these cell lines, nor were these genes highly expressed. We therefore propose that DNA damage induced H2Bub1-enrichment in mutant p53 cell lines will have an entirely distinct genomic profile compared to wild-type p53 cell lines, with important roles in enabling the expression of mutant p53 target genes in HGSOC. Experiments are currently under way to directly address this hypothesis. Lastly, we have used clonogenic cell survival assays to demonstrate that downregulation of RNF20, either transiently using short interfering (si) RNA or stably,using short hairpin (sh) RNA, decreased the ability of HGSOC cells to survive treatment with cisplatin. Down-regulation of H2Bub1 by downregulation of its E3 ubiquitin ligase RNF20 may represent a novel treatment strategy to increase the efficacy of DNA damage-based therapy for HGSOC.

Citation Format: Alexander J. Cole, Kristie-Ann Dickson, Christopher Liddle, Clare Stirzaker, Roderick Clifton-Bligh, Deborah J. Marsh. Cisplatin-induced DNA damage modifies the chromatin landscape of histone H2B monoubiquitination in a p53-dependent manner. [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr A06.

Abstract 3538: Targeting the E3 ubiquitin ligase RNF20 in ovarian cancer

E3 ubiquitin ligases are responsible for the final stage of the enzymatic ubiquitination cascade, where they transfer ubiquitin from an E2 conjugating enzyme to a lysine on the recognized substrate. The most common family of E3 ligases are RING (Really Interesting New Gene) domain proteins. Using immunohistochemistry, we have shown that the ring finger protein RNF20 is strongly expressed in 87% (379 of 424) of high-grade serous ovarian cancer (HGSOC) (1). In contrast, other tumors, including breast, metastatic prostate and colorectal cancer, have been reported to show a decrease in RNF20 transcript levels. The Cancer Genome Atlas has reported < 1% (3 of 316) HGSOCs with RNF20 missense variants of unknown pathogenicity. Given the high level of RNF20 expression in HGSOC, it is unlikely that RNF20 transcript levels are reduced in these tumors.

RNF20 functioning in a heterodimer with RNF40 is the main E3 ligase complex responsible for monoubiquitination of histone H2B at lysine 120 (H2Bub1) (2). This active histone mark leads to an open chromatin configuration favouring DNA access by transcriptional complexes and DNA repair proteins. The RNF20/RNF40 complex also monoubiquitinates and stabilizes the Eg5 motor protein that functions in spindle assembly during mitosis, preventing spindle assembly defects, cell cycle arrest and apoptosis. RNF20 has also been implicated in polyubiquitination of the tumor suppressor Ebp1, promoting its degradation via the 26S proteasome in malignant cells.

We have down-regulated RNF20 in ovarian cancer cell lines to investigate the potential of targeting this E3 ligase to overcome resistance to platinum therapies that is a major problem for the clinical management of women with ovarian cancer. Cell lines studied included the HGSOC lines; COV318, OVCAR-3, OVCAR-4, CaOV3, HEY and OVSAHO, as well as the endometrioid line A2780. Cells were studied as monolayers and spheroid cultures. We have shown that down-regulation of RNF20 leads to lower levels of H2Bub1, consistent with a more closed chromatin configuration. Clonogenic cell survival assays following the treatment of ovarian cancer cell lines with cisplatin showed an impaired ability of cells in which RNF20 had been down-regulated to form colonies. This work provides preliminary evidence that developing strategies to therapeutically down-regulate RNF20 may increase the efficacy of standard-of-care chemotherapy for women with ovarian cancer.

(1) Dickson KA et al., Hum Mol Genet (2016)

(2) Cole AJ et al., Endocr Relat Cancer (2015)

Citation Format: Alexander J. Cole, Kristie-Ann Dickson, Roderick Clifton-Bligh, Deborah J. Marsh. Targeting the E3 ubiquitin ligase RNF20 in ovarian cancer [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 3538.

The RING finger domain E3 ubiquitin ligases BRCA1 and the RNF20/RNF40 complex in global loss of the chromatin mark histone H2B monoubiquitination (H2Bub1) in cell line models and primary high-grade serous ovarian cancer

Enzymatic factors driving cancer-associated chromatin remodelling are of increasing interest as the role of the cancer epigenome in gene expression and DNA repair processes becomes elucidated. Monoubiquitination of histone H2B at lysine 120 (H2Bub1) is a central histone modification that functions in histone cross-talk, transcriptional elongation, DNA repair, maintaining centromeric chromatin and replication-dependent histone mRNA 3'-end processing, as well as being required for the differentiation of stem cells. The loss of global H2Bub1 is seen in a number of aggressive malignancies and has been linked to tumour progression and/or a poorer prognosis in some cancers. Here, we analyse a large cohort of high-grade serous ovarian cancers (HGSOC) and show loss of global H2Bub1 in 77% (313 of 407) of tumours. Loss of H2Bub1 was seen at all stages (I-IV) of HGSOC, indicating it is a relatively early epigenomic event in this aggressive malignancy. Manipulation of key H2Bub1 E3 ubiquitin ligases, RNF20, RNF40 and BRCA1, in ovarian cancer cell line models modulated H2Bub1 levels, indicative of the role of these RING finger ligases in monoubiquitination of H2Bub1 in vitro. However, in primary HGSOC, loss of RNF20 protein expression was identified in just 6% of tumours (26 of 424) and did not correlate with global H2Bub1 loss. Similarly, germline mutation of BRCA1 did not show a correlation with the global H2Bub1 loss. We conclude that the regulation of tumour-associated H2Bub1 levels is complex. Aberrant expression of alternative histone-associated 'writer' or 'eraser' enzymes are likely responsible for the global loss of H2Bub1 seen in HGSOC.

Host-Guest Complexes of Carboxylated Pillar[n]arenes With Drugs

Pillar[n]arenes are a new family of nanocapsules that have shown application in a number of areas, but because of their poor water solubility their biomedical applications are limited. Recently, a method of synthesizing water-soluble pillar[n]arenes was developed. In this study, carboxylated pillar[n]arenes (WP[n], n = 6 or 7) have been examined for their ability to form host-guest complexes with compounds relevant to drug delivery and biodiagnostic applications. Both pillar[n]arenes form host-guest complexes with memantine, chlorhexidine hydrochloride, and proflavine by ¹H nuclear magnetic resonance and modeling. Binding is stabilized by hydrophobic effects within the cavities, and hydrogen bonding and electrostatic interactions at the portals. Encapsulation within WP[6] results in the complete and efficient quenching of proflavine fluorescence, giving rise to "on" and "off" states that have potential in biodiagnostics. The toxicity of the pillar[n]arenes was examined using in vitro growth assays with the OVCAR-3 and HEK293 cell lines. The pillar[n]arenes are relatively nontoxic to cells except at high doses and after prolonged continuous exposure. Overall, the results show that there could be a potentially large range of medical applications for carboxylated pillar[n]arene nanocapsules.

Assessing mutant p53 in primary high-grade serous ovarian cancer using immunohistochemistry and massively parallel sequencing

The tumour suppressor p53 is mutated in cancer, including over 96% of high-grade serous ovarian cancer (HGSOC). Mutations cause loss of wild-type p53 function due to either gain of abnormal function of mutant p53 (mutp53), or absent to low mutp53. Massively parallel sequencing (MPS) enables increased accuracy of detection of somatic variants in heterogeneous tumours. We used MPS and immunohistochemistry (IHC) to characterise HGSOCs for TP53 mutation and p53 expression. TP53 mutation was identified in 94% (68/72) of HGSOCs, 62% of which were missense. Missense mutations demonstrated high p53 by IHC, as did 35% (9/26) of non-missense mutations. Low p53 was seen by IHC in 62% of HGSOC associated with non-missense mutations. Most wild-type TP53 tumours (75%, 6/8) displayed intermediate p53 levels. The overall sensitivity of detecting a TP53 mutation based on classification as ‘Low’, ‘Intermediate’ or ‘High’ for p53 IHC was 99%, with a specificity of 75%. We suggest p53 IHC can be used as a surrogate marker of TP53 mutation in HGSOC; however, this will result in misclassification of a proportion of TP53 wild-type and mutant tumours. Therapeutic targeting of mutp53 will require knowledge of both TP53 mutations and mutp53 expression.

Abstract B05: Assessment of TP53 mutation status in primary high-grade serous ovarian cancer and cell line models: Comparison between immunohistochemistry and next-generation sequencing

Mutations in TP53 have been shown to occur in around 96% of high-grade serous ovarian cancer (HGSOC). Different TP53 mutations can lead to accumulation of mutant p53 in the cell that support gain of function effects, or loss or abrogation of both wild-type and mutant p53. Success of new therapeutic strategies for HGSOC that target mutant p53 will likely depend on detailed knowledge of the type of TP53 mutation present and its influence on mutant p53 levels in the cell. The aim of this study was to identify the spectrum of TP53 mutations in a cohort of primary HGSOCs and compare this with p53 immunostaining patterns. In addition, we sought to identify TP53 mutations in the previously uncharacterised HGSOC cell line models OV167 and OV202, as well as the clear cell adenocarcinoma line OV207.

DNA from fresh frozen tumors and cell line samples were processed for next generation sequencing using The Fluidigm Access TP53 Array System run on the Fluidigm Biomark HD™ Real-Time PCR fluidics system (Fluidigm Corporation). Amplicon libraries were pooled and analyses performed in a single massively parallel sequencing run using the MiSeq Sequencing System (Illumina Inc.). Unaligned BAM files were analyzed within the Broad Institute's Genome Analysis Toolkit (GATK) best practice pipeline. The ANNOVAR software tool was used to generate an annotated variants list. Variants were further filtered based on their frequency in the 1000 Genome Database and predicted SIFT scores. Mutations were visualized using the Broad Institute's Integrative Genomics Viewer. All samples in which a mutation was identified underwent Sanger sequencing using primers recommended in the International Agency for Research on Cancer TP53 database. Immunohistochemistry for p53 was performed on formalin fixed paraffin embedded tissue sections using a commercially available mouse monoclonal anti-human antibody (Protein Clone DO-7, cat. #M7001, Dako) on an automated staining platform (Leica BOND-III™ autostainer). The percentage of cells showing positive nuclear staining for p53 was reported.

A mutation in TP53 was identified in 94% (68 of 72) of HGSOC. The majority of mutations identified (62%, 42 of 68) were missense, with all except one of these mutations located in the p53 DNA binding domain. Overall, 82% (56 of 68) of mutations occurred within the DNA binding domain. Frameshift, stop or splice mutations (38%, 26 of 68) were identified in exons or flanking intronic sequence between exons 4 – 10. The presence or location of a TP53 mutation did not influence overall survival. Sanger sequencing was unable to reliably detect variants at an allele frequency less than 25%. TP53 mutations were identified in all cell lines at a mutant allele frequency ≥99%.

Based on percent of nuclei positive for p53, tumors were immunohistochemically graded as High, Intermediate or Low for p53. All missense mutations scored High for expression of the p53 protein. Considerable variability was observed in p53 staining levels in samples containing stop, frameshift or splice mutations, with samples in all of High, Intermediate and Low categories. Furthermore, a single sample shown to be wild-type for TP53 was graded as High for p53, raising the possibility that p53 had been activated in this tumor via an alternative mechanism. The level of p53 did not affect overall survival.

Taken together, these results suggest that caution needs to be exercised when using p53 immunohistochemistry as a surrogate marker for either presence or type of TP53 mutation. A combination of next generation sequencing and p53 immunohistochemistry is required to robustly define both mutation type and effect on mutant p53 levels in the cell.

Citation Format: Alexander J. Cole, Trisha Dwight, Ying Zhu, Anthony J. Gill, Kristie-Ann Dickson, Adele Clarkson, Gregory B. Gard, Jayne Maidens, Susan Valmadre, Roderick J. Clifton-Bligh, Deborah J. Marsh. Assessment of TP53 mutation status in primary high-grade serous ovarian cancer and cell line models: Comparison between immunohistochemistry and next-generation sequencing. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr B05.

Maximum sustainable speed, energetics and swimming kinematics of a tropical carangid fish, the green jack Caranx caballus

Maximum sustained swimming speeds, swimming energetics and swimming kinematics were measured in the green jack Caranx caballus (Teleostei: Carangidae) using a 41 l temperature-controlled, Brett-type swimming-tunnel respirometer. In individual C. caballus [mean ±s.d. of 22·1 ± 2·2 cm fork length (L(F) ), 190 ± 61 g, n = 11] at 27·2 ± 0·7° C, mean critical speed (U(crit)) was 102·5 ± 13·7 cm s⁻¹ or 4·6 ± 0·9 L(F) s⁻¹. The maximum speed that was maintained for a 30 min period while swimming steadily using the slow, oxidative locomotor muscle (U(max,c)) was 99·4 ± 14·4 cm s⁻¹ or 4·5 ± 0·9 L(F) s⁻¹. Oxygen consumption rate (M in mg O₂ min⁻¹) increased with swimming speed and with fish mass, but mass-specific M (mg O₂ kg⁻¹ h⁻¹) as a function of relative speed (L(F) s⁻¹) did not vary significantly with fish size. Mean standard metabolic rate (R(S) ) was 170 ± 38 mg O₂ kg⁻¹ h⁻¹, and the mean ratio of M at U(max,c) to R(S) , an estimate of factorial aerobic scope, was 3·6 ± 1·0. The optimal speed (U(opt) ), at which the gross cost of transport was a minimum of 2·14 J kg⁻¹ m⁻¹, was 3·8 L(F) s⁻¹. In a subset of the fish studied (19·7-22·7 cm L(F) , 106-164 g, n = 5), the swimming kinematic variables of tailbeat frequency, yaw and stride length all increased significantly with swimming speed but not fish size, whereas tailbeat amplitude varied significantly with speed, fish mass and L(F) . The mean propulsive wavelength was 86·7 ± 5·6 %L(F) or 73·7 ± 5·2 %L(T) . Mean ±s.d. yaw and tailbeat amplitude values, calculated from lateral displacement of each intervertebral joint during a complete tailbeat cycle in three C. caballus (19·7, 21·6 and 22·7 cm L(F) ; 23·4, 25·3 and 26·4 cm L(T) ), were 4·6 ± 0·1 and 17·1 ± 2·2 %L(T) , respectively. Overall, the sustained swimming performance, energetics, kinematics, lateral displacement and intervertebral bending angles measured in C. caballus were similar to those of other active ectothermic fishes that have been studied, and C. caballus was more similar to the chub mackerel Scomber japonicus than to the kawakawa tuna Euthynnus affinis.

Abstract 2167: The tumor suppressor CDC73/parafibromin is required for the maintenance of histone 2B monoubiquitination both in vitro and in vivo

CDC73 (cell division cycle 73), also known as parafibromin, is a ubiquitously expressed tumor suppressor that is mutated in the germline of patients with the familial disorder Hyperparathyroidism Jaw Tumor syndrome, as well as somatically mutated in sporadic parathyroid cancer. Furthermore, CDC73 has been implicated in breast, gastric, renal and colorectal tumorigenesis. CDC73 is a member of the PAF1 (RNA polymerase II-associated factor 1) transcriptional complex (PAF1c), along with PAF1, CTR9, LEO1, and SKI8. Consistent with roles in transcription, CDC73 is localized to the nucleus, and has also been reported in the nucleolus. This tumor suppressor has been shown to function as a negative regulator of cell cycle progression and to promote apoptosis, as well as have a role in the regulation of 3′ processing of histone mRNA. We used CDC73 as bait in a yeast two-hybrid assay and identified the E3 ubiquitin ligase ring finger proteins RNF20 and RNF40 as CDC73 binding partners. RNF20 and RNF40 exist in a heterodimeric complex that functions to monoubiquitinate histone H2B at lysine 120 (H2B-K120). Monoubiquitination of H2B-K120 is associated with transcription in undamaged cells, is induced after DNA damage, and has a role in the maintenance of replication-dependent histone mRNA 3′ - end processing. We have confirmed the interaction of CDC73 with both RNF20 and RNF40 in mammalian cells by co-immunoprecipitation of overexpressed and endogenous proteins from human embryonic kidney (HEK293) cells. Down-regulation of endogenous CDC73 by siRNA in HEK293 cells and the breast cancer cell line MCF7 led to a significant reduction of monoubiquitinated H2B-K120. Furthermore, in a series of eleven parathyroid carcinomas harboring mutations in CDC73 that led to loss of nuclear CDC73, monoubiquitinated H2B-K120 was either absent or significantly reduced relative to benign parathyroid tumors that expressed nuclear CDC73. siRNA down-regulation of other PAF1c members in MCF7 cells also led to reduction in levels of monoubiquitinated H2B-K120. Given that CDC73 is the only PAF1c member in which cancer-associated mutations have been reported, the translational significance of these findings are unclear. Loss of the CTR9 locus has been reported in pancreatic cancer, as well as overexpression of PAF1. PAF1c members may have a greater role in malignancy than previously described. This is the first report to demonstrate pathogenic mutations affecting monoubiquitination of a histone. We propose that loss of H2B-K120 monoubiquitination is a major mechanism whereby CDC73 mutations exert their tumorigenic effect.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2167. doi:1538-7445.AM2012-2167

Abstract 3150: miR-100 in ovarian cancer cell lines

MicroRNA (miRNA), small non-coding RNA sequences that regulate gene expression, have the potential to function as tumor suppressors or oncogenes. To determine the contribution of miRNA to ovarian oncogenesis this project sought to identify dysregulated miRNA and their targets in ovarian cancer cell lines. miRNA expression profiling was performed on 6 serous epithelial ovarian cancer (SEOC) cell lines and normal ovarian surface epithelial (OSE) cells. miRNAs differentially expressed between SEOC and OSEs were selected for further analyses and candidate target genes identified by prediction algorithms. miRNA expression was restored by transient transfection of miRNA mimics or stable transduction of lentiviral vectors expressing miRNA precursors. The effects on the expression of 2 predicted targets, SMARCA5 and FRAP1, were investigated using a luciferase reporter system, quantitative RT-PCR (qPCR) and immunoblotting. The effect of miRs on cellular proliferation was also explored. Expression profiling identified miR-100 as having >5-fold lower expression in SEOC vs OSE cells. Seed sequences or binding sites for miR-100 were identified in the 3′UTRs of SMARCA5 and FRAP1. Using a luciferase expression system in OVCAR-3 cells, a miR-100 mimic repressed expression of SMARCA5 3′UTR by 40 % (p<0.0001), and FRAP1 3′UTR by 30% (p<0.0005). No effect of the mimic was observed when the predicted miR-100 binding sites in each gene's 3′UTR were mutated. Stable transduction of OV202 cells with pre-miR-100 resulted in a 3-5 fold increase in miR-100 expression. This stably transduced SEOC cell line showed decreased cellular proliferation, and repressed transcript and protein levels of SMARCA5/SNF2H and FRAP1/mTOR compared with the cell line transduced with the empty lentiviral vector. We identified miR-100 as a modulator of cellular proliferation in OV202 cells, possibly through regulation of SNF2H, a chromatin remodelling factor, and mTOR a phosphatidylinositol kinase-related kinase. miR-100 is located in an area of frequent chromosomal loss in aggressive SEOC suggesting a mechanism for reduced expression in these cells. Future work will investigate the potential of miR-100 as a novel therapeutic target for the treatment of ovarian cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3150. doi:1538-7445.AM2012-3150

The tumor suppressor CDC73 interacts with the ring finger proteins RNF20 and RNF40 and is required for the maintenance of histone 2B monoubiquitination

Monoubiquitination of histone H2B is a dynamic post-translational histone modification associated with transcriptional elongation and the DNA damage response. To date, dysregulation of histone monoubiquitination has not been linked to pathogenic mutations in genes encoding proteins, or co-factors, catalyzing this modification. The tumor suppressor cell division cycle 73 (CDC73) is mutated and/or down-regulated in parathyroid carcinoma, renal, breast, gastric and colorectal tumors, as well as in the germline of patients with the familial disorder-hyperparathyroidism jaw tumor syndrome. Using CDC73 as bait in a yeast two-hybrid assay, we identified the ring finger proteins RNF20 and RNF40 as binding partners of this tumor suppressor. These polypeptides constitute a heterodimeric complex that functions as the E3 ubiquitin ligase for monoubiquitination of histone H2B at lysine 120 (H2B-K120). We show that RNF20 and RNF40 bind to discrete, but closely located, residues on CDC73. Monoubiquitinated H2B-K120 was significantly reduced after loss of nuclear CDC73, both in vitro upon down-regulation of CDC73, and in CDC73 mutant parathyroid tumors. A second histone modification, trimethylation of histone 3 at lysine 4 (H3-K4me3), remained unchanged in the presence of mutant or down-regulated CDC73, suggesting that H3-K4me3 is not always tightly linked to H2B-K120 monoubiquitination for transcription as previously described. This is the first report of pathogenic mutations affecting histone monoubiquitination. We conclude that CDC73 is required for the maintenance of H2B-K120 monoubiquitination and propose that reduction in levels of monoubiquitinated H2B-K120 is a major mechanism whereby mutations in CDC73 exert their tumorigenic effect.

Bacterially derived 400 nm particles for encapsulation and cancer cell targeting of chemotherapeutics

Systemic administration of chemotherapeutic agents results in indiscriminate drug distribution and severe toxicity. Here we report a technology potentially overcoming these shortcomings through encapsulation and cancer cell-specific targeting of chemotherapeutics in bacterially derived 400 nm minicells. We discovered that minicells can be packaged with therapeutically significant concentrations of chemotherapeutics of differing charge, hydrophobicity, and solubility. Targeting of minicells via bispecific antibodies to receptors on cancer cell membranes results in endocytosis, intracellular degradation, and drug release. This affects highly significant tumor growth inhibition and regression in mouse xenografts and case studies of lymphoma in dogs despite administration of minute amounts of drug and antibody; a factor critical for limiting systemic toxicity that should allow the use of complex regimens of combination chemotherapy.

Metabolic indicators in the skeletal muscles of harbor seals (Phoca vitulina)

The goal of this study was to determine the distribution of citrate synthase (CS), beta-hydroxyacyl coenzyme A dehydrogenase (HOAD), and lactate dehydrogenase (LDH) activities and myoglobin (Mb) concentration in the locomotor muscles (epaxial muscles) and heart of harbor seals. The entire epaxial musculature, which produces most of the power for submerged swimming, was removed and weighed, and three transverse sections (cranial, middle, and caudal) were taken along the muscle bundle. Multiple samples were taken along points on a circular grid using a 6-mm biopsy. A single sample was taken from the left ventricle of the heart. Muscle groups of similar function were taken from three dogs as a control. Mean values were calculated for four roughly equal quadrants in each transverse section of the epaxial muscles. There were no significant differences among the quadrants within any of the transverse sections for the three enzymes or Mb. However, there were significant differences in the mean enzyme activities and Mb concentrations along the length of the muscle. The middle and caudal sections had significantly higher mean levels of CS, LDH, and Mb than the cranial section, which may be correlated with power production during swimming. The enzyme ratios CS/HOAD and LDH/CS exhibited no variation within transverse sections or along the length of the epaxial muscles. Relative to the dog, the epaxial muscles and heart of the harbor seal had higher HOAD levels and lower CS/HOAD, which, taken together, indicate an increased capacity for aerobic lipid metabolism during diving.

Swimming performance studies on the eastern Pacific bonito Sarda chiliensis, a close relative of the tunas (family Scombridae) I. Energetics

A large swim tunnel respirometer was used to quantify the swimming energetics of the eastern Pacific bonito Sarda chiliensis (tribe Sardini) (45-50 cm fork length, FL) at speeds between 50 and 120 cm s(-1) and at 18+/-2 degrees C. The bonito rate of oxygen uptake ((O(2)))-speed function is U-shaped with a minimum (O(2)) at 60 cm s(-1), an exponential increase in (O(2)) with increased speed, and an elevated increase in (O(2)) at 50 cm s(-1) where bonito swimming is unstable. The onset of unstable swimming occurs at speeds predicted by calculation of the minimum speed for bonito hydrostatic equilibrium (1.2 FL s(-1)). The optimum swimming speed (U(opt)) for the bonito at 18+/-2 degrees C is approximately 70 cm s(-1) (1.4 FL s(-1)) and the gross cost of transport at U(opt) is 0.27 J N(-1) m(-1). The mean standard metabolic rate (SMR), determined by extrapolating swimming (O(2)) to zero speed, is 107+/-22 mg O(2) kg(-1) h(-1). Plasma lactate determinations at different phases of the experiment showed that capture and handling increased anaerobic metabolism, but plasma lactate concentration returned to pre-experiment levels over the course of the swimming tests. When adjustments are made for differences in temperature, bonito net swimming costs are similar to those of similar-sized yellowfin tuna Thunnus albacares (tribe Thunnini), but the bonito has a significantly lower SMR. Because bonitos are the sister group to tunas, this finding suggests that the elevated SMR of the tunas is an autapomorphic trait of the Thunnini.

Review: Analysis of the evolutionary convergence for high performance swimming in lamnid sharks and tunas

Elasmobranchs and bony fishes have evolved independently for more than 400 million years. However, two Recent groups, the lamnid sharks (Family Lamnidae) and tunas (Family Scombridae), display remarkable similarities in features related to swimming performance. Traits separating these two groups from other fishes include a higher degree of body streamlining, a shift in the position of the aerobic, red, locomotor muscle that powers sustained swimming to a more anterior location in the body and nearer to the vertebral column, the capacity to conserve metabolic heat (i.e. regional endothermy), an increased gill surface area with a decreased blood-water barrier thickness, a higher maximum blood oxygen carrying capacity, and greater muscle aerobic and anaerobic enzyme activities at in vivo temperatures. The suite of morphological, physiological, and biochemical specializations that define "high-performance fishes" have been extensively characterized in the tunas. This review examines the convergent features of lamnid sharks and tunas in order to gain insight into the extent that comparable environmental selection pressures have led to the independent origin of similar suites of functional characteristics in these two distinctly different taxa. We propose that, despite differences between teleost and elasmobranch fishes, lamnid sharks and tunas have evolved morphological and physiological specializations that enhance their swimming performance relative to other sharks and most other high performance pelagic fishes.

Enzyme activities support the use of liver lipid-derived ketone bodies as aerobic fuels in muscle tissues of active sharks

Few data exist to test the hypothesis that elasmobranchs utilize ketone bodies rather than fatty acids for aerobic metabolism in muscle, especially in continuously swimming, pelagic sharks, which are expected to be more reliant on lipid fuel stores during periods between feeding bouts and due to their high aerobic metabolic rates. Therefore, to provide support for this hypothesis, biochemical indices of lipid metabolism were measured in the slow-twitch, oxidative (red) myotomal muscle, heart, and liver of several active shark species, including the endothermic shortfin mako, Isurus oxyrinchus. Tissues were assayed spectrophotometrically for indicator enzymes of fatty acid oxidation (3-hydroxy-o-acyl-CoA dehydrogenase), ketone-body catabolism (3-oxoacid-CoA transferase), and ketogenesis (hydroxy-methylglutaryl-CoA synthase). Red muscle and heart had high capacities for ketone utilization, low capacities for fatty acid oxidation, and undetectable levels of ketogenic enzymes. Liver demonstrated undetectable activities of ketone catabolic enzymes but high capacities for fatty acid oxidation and ketogenesis. Serum concentrations of the ketone beta-hydroxybutyrate varied interspecifically (means of 0.128-0.978 micromol mL(-1)) but were higher than levels previously reported for teleosts. These results are consistent with the hypothesis that aerobic metabolism in muscle tissue of active sharks utilizes ketone bodies, and not fatty acids, derived from liver lipid stores.

Ontogenetic changes in characteristics required for endothermy in juvenile black skipjack tuna (Euthynnus lineatus)

To characterize better the development of endothermy in tunas, we assessed how the abilities to generate heat and to conserve heat within the aerobic, slow-twitch (red) myotomal muscle using counter-current heat exchangers (retia) change with size in juvenile black skipjack tuna (Euthynnus lineatus) above and below the hypothesized minimum size for endothermy of 207 mm fork length (FL). Early juvenile scombrids (10–77 mm FL) collected off the Pacific coast of Panama were raised to larger sizes at the Inter-American Tropical Tuna Commission Laboratory at Achotines Bay, Panama. Evidence of central and lateral rete blood vessels was found in E. lineatus as small as 95.9 mm FL and 125 mm FL, respectively. In larger E. lineatus juveniles (up to 244 mm FL), the capacity for heat exchange increased with fork length as a result of increases in rete length, rete width and the number of vessel rows. The amount (g) of red muscle increased exponentially with fork length in both E. lineatus (105–255 mm FL) and a closely related ectothermic species, the sierra Spanish mackerel Scomberomorus sierra (151–212 mm FL), but was greater in E. lineatus at a given fork length. The specific activity (international units g(−)(1)) of the enzyme citrate synthase in red muscle, an index of tissue heat production potential, increased slightly with fork length in juvenile E. lineatus (84. 1–180 mm FL) and S. sierra (122–215 mm FL). Thus, total red muscle heat production capacity (red muscle citrate synthase activity per gram times red muscle mass in grams) increased with fork length, primarily because of the increase in red muscle mass. Below 95.9 mm FL, E. lineatus cannot maintain red muscle temperature (T(m)) above the ambient water temperature (T(a)) because juveniles of this size lack retia. Above 95.9 mm FL, the relationship between T(x) (T(m)-T(a)) and FL for E. lineatus diverges from that for the ectothermic S. sierra because of increases in the capacities for both heat production and heat retention that result in the development of endothermy.

Maximum sustainable speeds and cost of swimming in juvenile kawakawa tuna (Euthynnus affinis) and chub mackerel (Scomber japonicus)

Tunas (Scombridae) have been assumed to be among the fastest and most efficient swimmers because they elevate the temperature of the slow-twitch, aerobic locomotor muscle above the ambient water temperature (endothermy) and because of their streamlined body shape and use of the thunniform locomotor mode. The purpose of this study was to test the hypothesis that juvenile tunas swim both faster and more efficiently than their ectothermic relatives. The maximum sustainable swimming speed (U(max), the maximum speed attained while using a steady, continuous gait powered by the aerobic myotomal muscle) and the net cost of transport (COT(net)) were compared at 24 degrees C in similar-sized (116–255 mm fork length) juvenile scombrids, an endothermic tuna, the kawakawa (Euthynnus affinis) and the ectothermic chub mackerel (Scomber japonicus). U(max) and COT(net) were measured by forcing individual fish to swim in a temperature-controlled, variable-speed swimming tunnel respirometer. There were no significant interspecific differences in the relationship between U(max) and body mass or fork length or in the relationship between COT(net) and body mass or fork length. Muscle temperatures were elevated by 1.0-2.3 degrees C and 0.1-0.6 degrees C above water temperature in the kawakawa and chub mackerel, respectively. The juvenile kawakawa had significantly higher standard metabolic rates than the chub mackerel, because the total rate of oxygen consumption at a given swimming speed was higher in the kawakawa when the effects of fish size were accounted for. Thus, juvenile kawakawa are not capable of higher sustainable swimming speeds and are not more efficient swimmers than juvenile chub mackerel.

Swimming kinematics of juvenile kawakawa tuna (Euthynnus affinis) and chub mackerel (Scomber japonicus)

The swimming kinematics of two active pelagic fishes from the family Scombridae were compared to test the hypothesis that the kawakawa tuna (Euthynnus affinis) uses the thunniform mode of locomotion, in which the body is held more rigid and undergoes less lateral movement in comparison with the chub mackerel (Scomber japonicus), which uses the carangiform swimming mode. This study, the first quantitative kinematic comparison of size-matched scombrids, confirmed significantly different swimming kinematics in the two species. Ten kawakawa (15.1-25.5 cm fork length, FL) and eight chub mackerel (14.0-23.4 cm FL), all juveniles, were videotaped at 120 Hz while swimming at several speeds up to their maximum sustained speed at 24 degrees C. Computerized motion analysis was used to digitize specific points on the body in sequential video frames, and kinematic variables were quantified from the progression of the points over time. At a given speed, kawakawa displayed a significantly greater tailbeat frequency, but lower stride length, tailbeat amplitude and propulsive wavelength, than chub mackerel when size effects were accounted for. Midline curvatures subdivided on the basis of X-rays into individual vertebral elements were used to quantify axial bending in a subset of the fish studied. Maximum intervertebral lateral displacement and intervertebral flexion angles were significantly lower along most of the body in kawakawa than in chub mackerel, indicating that the kawakawa undergoes less axial flexion than does the chub mackerel, resulting in lower tailbeat amplitudes. However, lateral movement at the tip of the snout, or yaw, did not differ significantly interspecifically. Despite these differences, the net cost of transport was the same in the two species, and the total cost was higher in the kawakawa, indicating that the tuna juveniles are not more efficient swimmers.

Tail kinematics of the chub mackerel Scomber japonicus: testing the homocercal tail model of fish propulsion

Scombrid fishes possess a homocercal caudal fin with reduced intrinsic musculature and dorso-ventrally symmetrical external and internal morphology. Because of this symmetrical morphology, it has often been assumed that scombrid caudal fins function as predicted by the homocercal tail model. According to that model, the caudal fin moves in a dorso-ventrally symmetrical manner and produces no vertical lift during steady swimming. To test this hypothesis, we examined the tail kinematics of chub mackerel, Scomber japonicus (24.8+/−1.3 cm total length, L). Markers were placed on the caudal fin to identify specific regions of the tail, and swimming chub mackerel were videotaped from lateral and posterior views, allowing a three-dimensional analysis of tail motion. Analysis of tail kinematics suggests that, at a range of swimming speeds (1.2-3.0 L s(−)(1)), the dorsal lobe of the tail undergoes a 15 % greater lateral excursion than does the ventral lobe. Lateral excursion of the dorsal tail-tip also increases significantly by 32 % over this range of speeds, indicating a substantial increase in tail-beat amplitude with speed. In addition, if the tail were functioning in a dorso-ventrally symmetrical manner, the tail should subtend an angle of 90 degrees relative to the frontal (or xz) plane throughout the tail beat. Three-dimensional kinematic analyses reveal that the caudal fin actually reaches a minimum xz angle of 79.8 degrees. In addition, there is no difference between the angle subtended by the caudal peduncle (which is anterior to the intrinsic tail musculature) and that subtended by the posterior lobes of the tail. Thus, asymmetrical movements of the tail are apparently generated by the axial musculature and transmitted posteriorly to the caudal fin. These results suggest that the caudal fin of the chub mackerel is not functioning symmetrically according to the homocercal model and could produce upward lift during steady swimming.

Effects of endurance training in the leopard shark, Triakis semifasciata

This study is the first to examine the effects of endurance training in an elasmobranch fish. Twenty-four leopard sharks (Triakis semifasciata) were divided randomly into three groups. Eight sharks were killed immediately, eight were forced to swim continuously for 6 wk against a current of 35 cm s-1 (60%-65% of maximal sustainable swimming speed), and eight were held for 6 wk in a tank without induced current. There were no changes due to training in maximal sustainable speed, oxygen consumption rates, percentage of the myotome composed of red and white muscle fibers, blood oxygen-carrying capacity, liver mass, liver lipid, glycogen, and protein concentrations, white muscle protein content, heart ventricle mass, or the specific activities of the enzymes citrate synthase, pyruvate kinase, and lactate dehydrogenase in the heart ventricle. In red myotomal muscle, citrate synthase activity increased 17% as a result of training, but there was no change in muscle fiber diameter. The greatest effects occurred in white myotomal muscle, in which a 34% increase in fiber diameter and a 36% increase in the activities of citrate synthase and lactate dehydrogenase occurred as a result of training. The conditioned fish also had significantly higher growth rates. The observed effects within the myotomal muscle may reflect the higher growth rates of the trained leopard sharks, or they may be a specific response to the increased energetic demands of the training activity, indicating characteristics that limit swimming performance in leopard sharks.

Fetal and maternal fluid balance in sheep during hyperthermia with and without water deprivation

Our aim was to determine the effect of maternal hyperthermia, both with and without maternal water deprivation, on fetal fluid balance. Seven pregnant ewes (131.8 +/- 1.0 days gestation) were studied during a control period and periods of maternal heating (MH, 42-44 degrees C for 8 h, water freely available), maternal water deprivation (MWD, 30 h) and maternal heating combined with water deprivation (MH + MWD, 30 h deprivation with heating during last 8 h). Relative to control values, MH increased maternal water intake and urine output, and [K+] in fetal plasma and fetal urine. Relative to control values, MH decreased maternal plasma osmolality, [Na+] and [K+]; fetal plasma osmolality and [Na+]; fetal lung liquid [Na+] and [Cl-]; and fetal production rates of lung liquid and urine. In response to MH + MWD, the osmolality, [Na+] and [Cl-] of maternal and fetal plasma, fetal lung liquid and fetal urine (excluding urinary [Cl-]) increased compared with control values. In the fetus, MH + MWD increased plasma and urinary [K+], and decreased production rates of lung liquid and urine compared with control values. During MH + MWD, compared with MH alone, greater alterations were seen in maternal rectal temperature, water input and urine output; osmolality, [Na+] and [Cl-] of maternal and fetal plasma, fetal lung liquid and fetal urine (excluding urinary [Cl-]); and fetal urinary [K+]. During MH + MWD, compared with MWD alone, greater alterations were seen in maternal plasma [Cl-] and [K+]; fetal urinary osmolality and [K+]; and fetal plasma [K+]. Our results show that, when water is available, maternal hyperthermia stimulates ewes to drink substantially more than under normal conditions, thereby decreasing their plasma osmolality; water transfer to the fetus may increase, thereby decreasing fetal plasma osmolality. When drinking water is unavailable, maternal hyperthermia and associated dehydration may decrease water transfer to the fetus. Thus, the fetus becomes not only hyperthermic, but also hyperosmotic and possibly hypovolaemic. Maternal hyperthermia, irrespective of the availability of drinking water, decreases production rates of lung liquid and urine in the fetus.

Role of fetal sac fluids during maternal water deprivation in sheep

Our aim was to determine the importance of amniotic and allantoic fluids for the maintenance of fetal plasma composition during maternal dehydration when water transfer from mother to fetus is likely to be reduced. Eight pregnant ewes were studied before, during and after water deprivation (36 h), firstly with the fetal fluid sacs intact and then with them drained of fluid for 5 days. When water deprivation was combined with drainage, the increases in the osmolalities, [Na+] and [Cl-] in maternal plasma, in fetal plasma and in lung liquid; the increases in fetal urinary osmolality and [Na+]; and the increases in maternal plasma and fetal plasma arginine vasopressin concentrations were greater than those resulting from water deprivation alone. Our results show that during maternal water deprivation, an absence of fluid in the fetal sacs increases both the osmotic stimulus to the fetus and the fetal responses resulting in conservation of water and salt. We conclude that, when the mother is deprived of water, fluid in the fetal sacs is used to limit the degree of maternal and fetal dehydration.

Compliances of the liquid-filled lungs and chest wall during development in fetal sheep

Our aim was to measure the compliance of the liquid-filled lungs (CL), and the compliance of the chest wall (CW) in fetal sheep in utero. CL and CW were measured in 6 fetuses. The compliance of the lungs and chest wall combined (respiratory system, Crs) was measured in 9 fetuses. Pressure differences across the lungs (PL), chest wall (PW) and respiratory system (Prs) were measured while the lungs were deflated and inflated with liquid from their resting lung liquid volume (V1). V1 was measured using an indicator dilution technique. Specific compliance values were obtained by normalizing the values of CL, CW and Crs with respect to values of V1. From values obtained during stepwise inflation from V1, specific compliances (ml/cm H2O/ml of lung liquid) were: lungs, 0.22 +/- 0.02; chest wall, 0.41 +/- 0.07; respiratory system, 0.13 +/- 0.01. Specific compliances of the lungs, chest wall and respiratory system did not change significantly with advancing gestational age from 120 to 143 days. Our baseline data will be valuable in assessing the in utero progress of the structural development of the lungs following manipulations known to cause altered lung growth.

Fetal breathing and pressures in the trachea and amniotic sac during oligohydramnios in sheep

Oligohydramnios commonly leads to fetal lung hypoplasia, but the mechanisms are not fully understood. Our aim was to determine, in fetal sheep, the effects of prolonged oligohydramnios on the incidence and amplitude of tracheal pressure fluctuations associated with fetal breathing movements (FBM), on tracheal flow rate during periods of FBM (VtrFBM) and periods of apnea (Vtrapnea), on tracheal pressure relative to amniotic sac pressure, and on amniotic sac pressure relative to atmospheric pressure. In five sheep, oligohydramnios was induced by draining amniotic and allantoic fluids from 107 to 135 days of gestation (411.8 +/- 24.4 ml/day), resulting in fetal lung hypoplasia. In five control sheep, amniotic fluid volume was 732.3 +/- 94.4 ml. Oligohydramnios increased the incidence of FBM by 14% at 120 and 125 days and the amplitude of FBM by 30-34% at 120-130 days compared with controls. From 120 days onward, VtrFBM was 35-55% lower in experimental fetuses than in controls. Influx of lung liquid during FBM was 87% lower in experimental fetuses than in controls. Vtrapnea, tracheal pressure, and amniotic sac pressure were not significantly altered by oligohydramnios. Our tracheal flow rate data suggest that transient changes in lung liquid volume during periods of FBM and periods of apnea were diminished by oligohydramnios. We conclude that the primary factor in the etiology of oligohydramnios-induced lung hypoplasia is not an inhibition of FBM (as measured by tracheal pressure fluctuations) or a reduction in amniotic fluid pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

A mechanism leading to reduced lung expansion and lung hypoplasia in fetal sheep during oligohydramnios

Our aim was to determine the mechanism whereby oligohydroamnios causes reduced fetal lung expansion and eventual lung hypoplasia. We studied 20 fetal sheep during 2 to 9 days of oligohydramnios produced by drainage of amniotic and allantoic fluids during the last third of gestation. Oligohydramnios led to a reversible reduction in lung liquid volume of 19.5% within 48 hours. During oligohydramnios tracheal pressure, relative to amniotic pressure, rose by 1.7 mm Hg (p less than 0.001); pressures also tended to rise in the fetal pleural space and abdomen, relative to amniotic pressure, and to fall in the amniotic sac. Pressure increments, relative to amniotic pressure, which normally occur in the fetal trachea, pleural cavity, and abdomen during nonlabor uterine contractions, were significantly increased by 1.9 to 2.5 mm Hg during oligohydramnios. Oligohydramnios increased flexion of the fetal thoracolumbar spine, quantified as a reduction in the ratio of spinal radius of curvature to spine length (0.76 in controls vs 0.40 after oligohydramnios, p less than 0.001). In three sets of twins, only the fetus exposed to oligohydramnios was affected. A similar degree of spinal flexion imposed on normal fetal sheep cadavers increased abdominal (1.6 mm Hg), pleural (1.5 mm Hg), and tracheal (2.0 mm Hg) pressure, and caused a significant reduction in fetal lung expansion. We conclude that oligohydramnios in fetal sheep increases spinal flexion, leading to compression of abdominal contents, upward displacement of the diaphragm, and lung compression, favoring loss of fetal lung liquid. These changes, which are accentuated during nonlabor uterine contractions and are reversible, may lead to pulmonary hypoplasia if prolonged.

Endocrine and fluid-balance responses to amniotic and allantoic fluid loss in sheep

Our aim was to determine fetal and maternal endocrine and fluid-balance responses to prolonged loss of amniotic and allantoic fluids in sheep. In seven sheep, amniotic and allantoic fluids were drained [379.1 +/- 20.1 (SE) ml/day] from 107 to 135.3 +/- 0.6 days of gestation (term: 145 days). The results from these sheep were compared with those from seven control sheep. Maternal water intake, urine production, and urine osmolality were not altered by fluid drainage, nor were fetal and maternal arterial blood gases, pH, or plasma osmolalities. Fluid drainage increased amniotic, but not allantoic, fluid osmolality. Maternal plasma cortisol concentration increased with fluid drainage, but maternal plasma concentrations of prolactin and arginine vasopressin were unchanged. Fluid drainage increased prolactin concentrations in fetal plasma and amniotic fluid, but fetal plasma concentrations of cortisol (hydrocortisone), arginine vasopressin, norepinephrine, and epinephrine were unchanged. Our results show that the fetus is capable of maintaining its plasma osmolality despite prolonged loss of fluid from its amniotic and allantoic sacs and that this is associated with alterations in the production rate and the composition of amniotic fluid.

Decline in lung liquid volume and secretion rate during oligohydramnios in fetal sheep

Reduced amniotic fluid volume often results in fetal lung hypoplasia. Our aim was to examine the effects of prolonged drainage of amniotic and allantoic fluids on lung liquid volume (Vl), secretion rate (Vs), and tracheal flow rate (Vtr) in fetal sheep. In five experimental animals, amniotic and allantoic fluids were drained from 107 to 135 days of gestation. The volume of fluid drained from the experimental animals was 411.8 +/- 24.4 ml/day (n = 140). In six control animals, amniotic fluid volume was 747.7 +/- 89.7 ml (n = 15). Wet and dry lung weights were 20-25% lower in experimental fetuses than in control fetuses. Fetal hemoglobin, O2 saturation, arterial PO2, pH, and hematocrit were unchanged by drainage. During the drainage period, Vl was up to 65% lower, Vs was up to 35% lower, and Vtr was up to 40% lower in experimental fetuses than in control fetuses. We conclude that prolonged drainage of amniotic and allantoic fluids decreases Vl, Vs, and Vtr in fetal sheep. These findings indicate that fetal lung hypoplasia associated with oligohydramnios may be the result of a prolonged reduction in Vl.

Lung liquid secretion, flow and volume in response to moderate asphyxia in fetal sheep

The effects of moderate fetal asphyxia, induced by constriction of the maternal common internal iliac artery, on lung liquid secretion, tracheal fluid efflux and lung liquid volume have been investigated in unanaesthetized fetal sheep (111-142 days) in utero. During periods of fetal asphyxia the percent oxygen saturation, PO2, pH, and PCO2 of fetal carotid arterial blood changed from 57.2 +/- 1.3% (mean +/- SEM), 22.9 +/- 0.6 mmHg, 7.35 +/- 0.01 and 45.6 +/- 1.0 mmHg to 26.3 +/- 0.5% (P less than 0.001), 14.7 +/- 0.2 mmHg (P less than 0.001), 7.28 +/- 0.02, (P less than 0.001) and 47.8 +/- 0.4 mmHg (P less than 0.02), respectively. Fetal asphyxia, over 6 h, decreased the efflux of tracheal fluid from 7.07 +/- 0.47 ml/h to 3.97 +/- 0.36 ml/h (P less than 0.01) and, over 4 h, decreased the rate of lung liquid secretion from 9.42 +/- 1.76 ml/h to 4.91 +/- 1.54 ml/h (P less than 0.005), whereas it had no significant effect on lung liquid volume. The incidence of fetal breathing movements decreased from 52.9 +/- 2.5% to 22.6 +/- 3.5% during 6-h periods of fetal asphyxia. Thus, although fetal asphyxia decreased the net production of lung liquid, lung liquid volume was maintained probably, because the net efflux of fluid from the lungs via the trachea decreased to a similar extent.

Restoration of lung liquid volume following its acute alteration in fetal sheep

1. The experiments were aimed at determining the means by which lung liquid volume is controlled in fetal sheep. Six unanaesthetized chronically catheterized fetuses between 121 and 144 days of gestation were used in experiments in which lung liquid volume was acutely reduced or increased. 2. The effects on lung liquid volume, secretion and flow in the trachea were continuously monitored until the original volume was restored. Tracheal pressure, breathing activity, electrocortical activity and laryngeal adductor muscle activity were also monitored. 3. Following a mean reduction in lung liquid volume of 54.1% (40.0 +/- 4.3 ml) there was a reduction in tracheal pressure of 1.91 +/- 0.26 mmHg. There was no change in the rate of lung liquid secretion and there was a near cessation in its rate of efflux from the trachea. Influx of liquid from the upper airway was rarely seen. 4. 5 h after its reduction, lung liquid volume had returned to control values. Tracheal pressure and the rate of liquid flow in the trachea returned to control values over 7-8 h. 5. In the hour following the reduction in lung liquid volume the incidence and amplitude of fetal inspiratory muscle electromyogram (e.m.g.) activity were reduced by 19% and 28% respectively. There was no change in laryngeal adductor muscle activity or in the duration of fetal sleep states. 6. When lung liquid volume was increased by 25.4 +/- 3.1 ml tracheal pressure increased by 2.01 +/- 0.17 mmHg. Although there was no change in the rate of liquid secretion there was a rapid efflux of liquid from the trachea principally during epochs of fetal breathing activity thus returning lung liquid volume to its control value. 7. Following the increase in lung liquid volume there were no changes in the incidence or amplitude of fetal inspiratory muscle activity, the activity of laryngeal adductor muscles or in the duration of sleep states. 8. It is concluded that following its alteration in fetal sheep lung liquid volume is restored by passive means. There was no evidence of volume-receptive neural reflexes being activated in defence of lung liquid volume.

State-related changes in lung liquid secretion and tracheal flow rate in fetal lambs

The volume of liquid in the fetal lungs depends on the rate of liquid secretion (Vs) across the pulmonary epithelium and the rate of flow out of the trachea (Vtr). We measured Vs, by an isotope-dilution technique, and Vtr, with a bubble flowmeter, during low-voltage (LV) and high-voltage (HV) electrocortical activity. In nine chronically instrumented fetal lambs, Vtr was greater during the transition to and at LV (16.98 +/- 1.98 ml/h, mean +/- SE, n = 23) than values during the transition to and at HV (8.69 +/- 0.8 ml/h). A pronounced peak in Vtr of 22.3 +/- 1.8 ml/h (n = 197) occurred at the transition to LV and early in the LV state. Ten minutes or more into LV, Vtr had declined to 10.3 +/- 1.8 ml/h (n = 235). Vtr remained low throughout the HV state. Vs values were not significantly different throughout the LV (11.83 +/- 1.34 ml/h, n = 216) and the HV (13.61 +/- 2.34 ml/h, n = 174) states. Diaphragmatic burst rate during LV (146.9 +/- 6.7 bursts/5 min, n = 432) was greater than during HV (26.5 +/- 4.6 bursts/5 min, n = 348), but burst rate was not correlated with Vtr. In summary, Vtr reaches a peak during the early part of LV when breathing commences and Vs remains constant throughout the behavioral cycle. As a result, lung liquid volume increases slightly during HV and decreases by a similar amount in the early part of LV.

Decline in lung liquid volume before labor in fetal lambs

The volume of liquid in the fetal lung depends on the amount of liquid secreted across the pulmonary epithelium and the amount flowing through the trachea. Lung liquid volume (V1) and secretion rate Vs) were determined using an indicator-dilution technique, while tracheal flow rate (Vtr) was measured simultaneously with a bubble flowmeter. Least-squares regression analysis showed that in 10 chronically instrumented fetal lambs, V1 increased from 51.0 ml at 119 days to 104.6 ml at 135 days (V1 = -347.65 + 3.35 X days; 95% confidence limits on slope: 1.89-4.81) before declining to 70.2 ml at 142 days gestation (V1 = 768.8 - 4.92 X days; 95% confidence limits on slope: -2.55 to -7.30). Similarly Vs increased from 7.4 ml/h at 119 days to 16.8 ml/h at 133 days (Vs = -72.35 + 0.67 X days; 95% confidence limits on slope: 0.21-1.14), before declining to 7.1 ml/h at 142 days (Vs = 159.07 - 1.07 X days; 95% confidence limits on slope: -0.56 to -1.57). Vtr did not change significantly with gestation. We conclude that V1 increases until 135 days gestation, after which it falls substantially. This fall in volume, which occurs well before the onset of labor, results predominantly from the decline in Vs.