Mechanistic Insight on the Mode of Action of Colletoic Acid

The natural product colletoic acid (CA) is a selective inhibitor of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which primarily converts cortisone to the active glucocorticoid (GC) cortisol. Here, CA's mode of action and its potential as a chemical tool to study intracellular GC signaling in adipogenesis are disclosed. 11β-HSD1 biochemical studies of CA indicated that its functional groups at C-1, C-4, and C-9 were important for enzymatic activity; an X-ray crystal structure of 11β-HSD1 bound to CA at 2.6 Å resolution revealed the nature of those interactions, namely, a close-fitting and favorable interactions between the constrained CA spirocycle and the catalytic triad of 11β-HSD1. Structure-activity relationship studies culminated in the development of a superior CA analogue with improved target engagement. Furthermore, we demonstrate that CA selectively inhibits preadipocyte differentiation through 11β-HSD1 inhibition, suppressing other relevant key drivers of adipogenesis (i.e., PPARγ, PGC-1α), presumably by negatively modulating the glucocorticoid signaling pathway. The combined findings provide an in-depth evaluation of the mode of action of CA and its potential as a tool compound to study adipose tissue and its implications in metabolic syndrome.

Abstract 1869: Mechanistic evaluation of ergosterol peroxide onin vitrobreast cancer models

Ganoderma lucidum extract (GLE), an extensively studied mushroom for its anti-cancer and anti-inflammatory properties, has been shown to possess physiologically active compounds such as polysaccharides, triterpenoids and sterols. In our previous studies, we reported that commercially available GLE whole mushroom extract selectively inhibits cancer cell viability, induces apoptosis, reduces invasion, and regulates key signaling molecules in various cell models of breast cancer. Hence, we sought to elucidate the compounds responsible for the observed anti-cancer activity. Among the isolated compounds from GLE, we identified a steroidal compound, Ergosterol Peroxide (EP), which has shown antiproliferative activity against cancer. EP is a member of natural endoperoxides, featuring the peroxy- warhead that can lead to hydroxyperoxy radicals or be activated and react as nucleophile, leading to significant biological cytotoxicity against various cancer models (e.g. ovarian, liver, colon). We hypothesized that EP would promote cell death mechanisms in the aggressive breast cancer phenotype. Thus, in this study, we evaluated EP’s anti-cancer potential using immunoblotting, colony formation, cell motility, cell cycle and reactive oxygen species (ROS) production assays against human breast cancer SUM-149, MCF-7, MDA-MB-231 cellular models. We show that EP displays anti-proliferative effects through cell arrest in G1 phase, and apoptosis induction via caspase 3/7 activation. EP induced ROS and decreased the migratory and invasive phenotype of these cancer cells. Moreover, it inhibited the expression of total AKT1, AKT2, BCL-2, BCL-XL, Cyclin D1 and c-Myc. Our combined results indicate that EP from GLE is a promising molecular scaffold for further exploration as an anti-cancer agent,particularly in aggressive breast cancer models.

Citation Format: Camille L. Santiago, Fatima Rivas, Taotao Ling, Ivette J. Suarez-Arroyo, Gabriela Ortiz, Mercedes Y. Lacourt, Anibal Valentin, Walter H. Lang, Michelle M. Martínez-Montemayor. Mechanistic evaluation of ergosterol peroxide onin vitrobreast cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1869.

Development of ergosterol peroxide probes for cellular localisation studies

Ergosterol peroxide selectively exhibits biological activity against a wide range of diseases; however, its mode of action remains unknown. Here, we present an efficient synthesis of ergosterol peroxide chemical probes for in vitro anticancer evaluation, live cell studies and proteomic profiling. Ergosterol peroxide analogues show promising anti-proliferation activity against triple negative breast cancer cellular models, revealing information on the structure-activity relationship of this natural product in order to develop superior analogues. The combined cellular studies demonstrate that ergosterol peroxide is distributed across the cytosol with significant accumulation in the endoplasmic reticulum (ER). These chemical probes support our efforts towards uncovering the potential target(s) of ergosterol peroxide against triple negative breast cancer cell lines.

Cytostatic and Cytotoxic Natural Products against Cancer Cell Models

The increasing prevalence of drug resistant and/or high-risk cancers indicate further drug discovery research is required to improve patient outcome. This study outlines a simplified approach to identify lead compounds from natural products against several cancer cell lines, and provides the basis to better understand structure activity relationship of the natural product cephalotaxine. Using high-throughput screening, a natural product library containing fractions and pure compounds was interrogated for proliferation inhibition in acute lymphoblastic leukemia cellular models (SUP-B15 and KOPN-8). Initial hits were verified in control and counter screens, and those with EC₅₀ values ranging from nanomolar to low micromolar were further characterized via mass spectrometry, NMR, and cytotoxicity measurements. Most of the active compounds were alkaloid natural products including cephalotaxine and homoharringtonine, which were validated as protein synthesis inhibitors with significant potency against several cancer cell lines. A generated BODIPY-cephalotaxine probe provides insight into the mode of action of cephalotaxine and further rationale for its weaker potency when compared to homoharringtonine. The steroidal natural products (ecdysone and muristerone A) also showed modest biological activity and protein synthesis inhibition. Altogether, these findings demonstrate that natural products continue to provide insight into structure and function of molecules with therapeutic potential against drug resistant cancer cell models.

Studies of Jatrogossone A as a Reactive Oxygen Species Inducer in Cancer Cellular Models

Natural products continue to provide a platform to study biological systems. A bioguided study of cancer cell models led us to a new member of the jatrophane natural products from Jatropha gossypiifolia, which was independently identified and characterized as jatrogossone A (1). Purification and structure elucidation was performed by column chromatography and high-performance liquid chromatography-mass spectrometry and NMR techniques, and the structure was confirmed via X-ray crystallography. The unique molecular scaffold of jatrogossone A prompted an evaluation of its mode of action. Cytotoxicity assays demonstrated that jatrogossone A displays selective antiproliferative activity against cancer cell models in the low micromolar range with a therapeutic window. Jatrogossone A (1) affects mitochondrial membrane potential (ΔΨm) in a time- and dose-dependent manner. This natural product induces radical oxygen species (ROS) selectively in cancer cellular models, with minimal ROS induction in noncancerous cells. Compound 1 induces ROS in the mitochondria, as determined by colocalization studies, and it induces mitophagy. It promotes also in vitro cell death by causing cell arrest at the G2/M stage, caspase (3/7) activation, and PARP-1 cleavage. The combined findings provide a potential mechanism by which 1 relies on upregulation of mitochondrial ROS to potentiate cytotoxic effects through intracellular signaling.

Identification of Biologically Active Ganoderma lucidum Compounds and Synthesis of Improved Derivatives That Confer Anti-cancer Activities in vitro

We previously reported that Ganoderma lucidum extract (GLE) demonstrate significant anti-cancer activity against triple negative inflammatory breast cancer models. Herein, we aimed to elucidate the bioactive compounds of GLE responsible for this anti-cancer activity. We performed NMR, X-ray crystallography and analog derivatization as well as anti-cancer activity studies to elucidate and test the compounds. We report the structures of the seven most abundant GLE compounds and their selective efficacy against triple negative (TNBC) and inflammatory breast cancers (IBC) and other human cancer cell types (solid and blood malignancies) to illustrate their potential as anti-cancer agents. Three of the seven compounds (ergosterol, 5,6-dehydroergosterol and ergosterol peroxide) exhibited significant in vitro anti-cancer activities, while we report for the first time the structure elucidation of 5,6-dehydroergosterol from Ganoderma lucidum. We also show for the first time in TNBC/IBC cells that ergosterol peroxide (EP) displays anti-proliferative effects through G1 phase cell cycle arrest, apoptosis induction via caspase 3/7 activation, and PARP cleavage. EP decreased migratory and invasive effects of cancer cells while inhibiting the expression of total AKT1, AKT2, BCL-XL, Cyclin D1 and c-Myc in the tested IBC cells. Our investigation also indicates that these compounds induce reactive oxygen species, compromising cell fate. Furthermore, we generated a superior derivative, ergosterol peroxide sulfonamide, with improved potency in IBC cells and ample therapeutic index (TI > 10) compared to normal cells. The combined studies indicate that EP from Ganoderma lucidum extract is a promising molecular scaffold for further exploration as an anti-cancer agent.

In-bag enzymatic splenic digestion: a novel alternative to manual morcellation?

BACKGROUND

Contained in-bag spleen morcellation is a conventional extraction technique for safe spleen removal during laparoscopic splenectomy. Existing data for the use of in-bag enzymatic splenic digestion as an alternative to morcellation are lacking. This proof-of-concept study sought to evaluate the effectiveness of single and combinatorial enzyme digestion of murine spleens.

MATERIALS AND METHODS

Murine spleens were digested with collagenase alone or with combinations of commercially available enzymes (collagenase, elastase, hyaluronidase, neutral protease) to determine their degradation effect. The primary end point was the percentage of mass reduction at 15 and 30 min.

RESULTS

For collagenase alone (n = 15), the mean reduction in mass was 14 ± 10% (range: 2%-31%) at 15 min and 30 ± 25% (range: 7%-100%) at 30 min. Using combinatorial dissolution with collagenase, hyaluronidase, and elastase (n = 8), the mean reduction in mass was 27 ± 16% (range: 6%-42%) at 15 min and 48 ± 27% (range: 3%-100%) at 30 min. Injecting the enzyme solution into whole spleens (n = 9) yielded a mean reduction in mass of 22 ± 13% (range: 9%-42%) at 15 min and 55 ± 31% (range: 9%-100%) at 30 min; mean reduction was 9 ± 13% (range: 0%-39%) at 15 min and 23 ± 13% (range: 3%-53%) with no injection (n = 12).

CONCLUSIONS

We provide the first demonstration of successful enzymatic murine spleen digestion as an alternative method for in-bag spleen removal during laparoscopic splenectomy. However, the significant cost and quantities of commercial enzyme required for clinical application dampens the enthusiasm for this novel approach.

Detection of PI3K inhibition in human neuroblastoma using multiplex luminex bead immunoassay: a targeted approach for pathway analysis

Neuroblastoma (NB) is a common solid tumor in children. Outcomes for advanced stage NB have not improved, at least in part because of multimodality therapy resistance. Better comprehension of novel molecular targets will likely lead to improved therapies with specific cytotoxic agents. For instance, the role of deregulated IGF-1R/AKT/PI3K/mTOR (PI3K) pathway activity has attracted much attention across several tumors, including NB. Thus, modulating this pathway via anti-PI3K drugs has taken center stage in many cancer clinical trials. However, varied clinical effects have hampered the precise application of these agents. Tumor PI3K pathway profiling may reveal a method to enhance the efficacy of these inhibitors. To this end, solid-phase antibody-based array platforms have emerged as a direct, rapid means of profiling intracellular signaling pathways. We tested the efficacy of four PI3K inhibitors against a panel of human NB cell lines using Luminex xMAP bead array technology to establish PI3K phosphoprotein profiles. We demonstrate the utility of the xMAP approach in following intracellular signaling signatures specific for PI3K targeted therapy. Further validation is required before xMAP is used routinely for clinical PI3K pathway evaluation, but this method may eventually be personalized by taking into account each child's basal NB pathway status.

Targeting oxidative stress in embryonal rhabdomyosarcoma

Rhabdomyosarcoma is a soft-tissue sarcoma with molecular and cellular features of developing skeletal muscle. Rhabdomyosarcoma has two major histologic subtypes, embryonal and alveolar, each with distinct clinical, molecular, and genetic features. Genomic analysis shows that embryonal tumors have more structural and copy number variations than alveolar tumors. Mutations in the RAS/NF1 pathway are significantly associated with intermediate- and high-risk embryonal rhabdomyosarcomas (ERMS). In contrast, alveolar rhabdomyosarcomas (ARMS) have fewer genetic lesions overall and no known recurrently mutated cancer consensus genes. To identify therapeutics for ERMS, we developed and characterized orthotopic xenografts of tumors that were sequenced in our study. High-throughput screening of primary cultures derived from those xenografts identified oxidative stress as a pathway of therapeutic relevance for ERMS.

Dissecting the PI3K Signaling Axis in Pediatric Solid Tumors: Novel Targets for Clinical Integration

Children with solid tumors represent a unique population. Recent improvements in pediatric solid tumor survival rates have been confined to low- and moderate-risk cancers, whereas minimal to no notable improvement in survival have been observed in high-risk and advanced-stage childhood tumors. Treatments for patients with advanced disease are rarely curative, and responses to therapy are often followed by relapse, which highlights the large unmet need for novel therapies. Recent advances in cancer treatment have focused on personalized therapy, whereby patients are treated with agents that best target the molecular drivers of their disease. Thus, a better understanding of the pathways that drive cancer or drug resistance is of critical importance. One such example is the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway, which is activated in many solid cancer patients and represents a target for therapy. PI3K/Akt/mTOR pathway activation has also been observed in tumors resistant to agents targeting upstream receptor tyrosine kinases (RTKs). Agents that target this pathway have the potential to shut down survival pathways, and are being explored both in the setting of pathway-activating mutations and for their ability to restore sensitivity to upstream signaling targeted agents. Here, we examine the role of the PI3K/Akt/mTOR pathway in pediatric solid tumors, review the novel agents being explored to target this pathway, and explore the potential role of the inhibition of this pathway in the clinical development of these agents in children.

Conformational trapping of mismatch recognition complex MSH2/MSH3 on repair-resistant DNA loops

Insertion and deletion of small heteroduplex loops are common mutations in DNA, but why some loops are prone to mutation and others are efficiently repaired is unknown. Here we report that the mismatch recognition complex, MSH2/MSH3, discriminates between a repair-competent and a repair-resistant loop by sensing the conformational dynamics of their junctions. MSH2/MSH3 binds, bends, and dissociates from repair-competent loops to signal downstream repair. Repair-resistant Cytosine-Adenine-Guanine (CAG) loops adopt a unique DNA junction that traps nucleotide-bound MSH2/MSH3, and inhibits its dissociation from the DNA. We envision that junction dynamics is an active participant and a conformational regulator of repair signaling, and governs whether a loop is removed by MSH2/MSH3 or escapes to become a precursor for mutation.

Escherichia coli rho factor induces release of yeast RNA polymerase II but not polymerase I or III

Purified RNA polymerase II (pol II) from the yeast Saccharomyces cerevisiae pauses without releasing at many locations during in vitro transcription. Pausing can be induced by intrinsic DNA sequence as well as by specific DNA bound proteins such as the RNA pol I termination factor, Reb1p, or lac repressor. Addition of rho termination factor from E. coli induces RNA pol II to release at all of these pause sites. Rho-induced release of pol II requires both a rho binding site in the transcript upstream of the pause sites as well as hydrolysis of ATP. In contrast, rho factor has no effect on either pausing or release by RNA pol I or III. When combined with previous observations, these results suggest that RNA pol II may terminate by a mechanism closely related to the rho-dependent mechanism of prokaryotes. In contrast, pol I and III appear to utilize a mechanism more related to the rho-independent terminators of prokaryotes.

Terminating transcription in eukaryotes: lessons learned from RNA polymerase I

Within the past few years, the genes encoding transcription terminator proteins for RNA polymerase I (pol I) have been cloned from organisms as diverse as yeast and mammals. The availability of terminator proteins has allowed construction of in vitro transcription systems that terminate pol I at the same sites as used in vivo and thus allows study of termination mechanisms. This has resulted in a burst of information concerning pol I termination mechanisms, which this review will attempt to summarize.

The yeast transcription terminator for RNA polymerase I is designed to prevent polymerase slippage

A transcription terminator for RNA polymerase I (polI) in the yeast, Saccharomyces cerevisiae, is composed of two essential elements, the 11bp binding site for Reb1p and an upstream T-rich element coding for the last 10-12 nucleotides of the terminated transcript. We now show that, if the upstream element is changed to homopolymer T residues, polI undergoes iterative slippage, long poly(U) tails are added to the transcript, and termination is impaired. Reinsertion of one or two non-T residues within a critical region prevents iterative slippage and reinstates termination. A survey of naturally occurring terminators reveals that many contain T-rich upstream regions with non-T residues situated appropriately to prevent slippage. We discuss the possibility that the first step in slippage, backward sliding of both the transcript and the catalytic center of the polymerase, may be an obligatory step in the normal termination process.

The release element of the yeast polymerase I transcription terminator can function independently of Reb1p

The Saccharomyces cerevisiae polymerase I (polI) transcription terminator utilizes a DNA-binding protein (Reb1p) as part of a signal that causes the polymerase to pause prior to release from the template. To study the release element of the terminator, independent of the Reb1p pause signal, we have replaced the Reb1p binding site with the binding site for the lac repressor, which acts as a self-contained heterologous pause signal for polI. Release efficiency is maximal when the lac repressor causes polI to pause in exactly the same position that Reb1p would have caused it to pause, suggesting that polI must be precisely positioned for transcript release to occur. Mutational analysis shows that the release element is a region rich in T residues which codes for the extreme 3' end of the transcript and which has no apparent ability to form hairpins when transcribed into RNA. We discuss possible mechanisms whereby this polI release element might function.

Transcription termination of RNA polymerase I due to a T-rich element interacting with Reb1p

All transcription terminators for RNA polymerase I (pol I) that have been studied so far, ranging from yeast to humans, require a specific DNA binding protein to cause termination. In yeast, this terminator protein has been identified as Reb1p. We now show that, in addition to the binding site for Reb1p, the yeast pol I terminator also requires the presence of a T-rich region coding for the last 12 nucleotides of the transcript. Reb1p cooperates with this T-rich element, both to pause the polymerase and to effect release of the transcript. These findings have implications for the termination mechanism used by all three nuclear RNA polymerases, since all three are known to pause at this terminator.

A model for transcription termination by RNA polymerase I

The transcription termination site for yeast RNA polymerase I requires not only an 11 bp binding site for Reb1p, but also about 46 bp of 5' flanking sequence. We propose that Reb1p bound to its site is part of a pause element, while the 5' flanking sequence contains a release element. Pausing requires little other than the DNA-binding domain of Reb1p and is not specific for polymerase I. The release element, however, can be polymerase specific. We propose a general model for eukaryotic transcription terminators in which termination occurs when a relatively nonspecific signal induces polymerase to pause in the context of a release element.

The REB1 site is an essential component of a terminator for RNA polymerase I in Saccharomyces cerevisiae

We have identified a terminator for transcription by RNA polymerase I in the genes coding for rRNA of the yeast Saccharomyces cerevisiae. The terminator is located 108 bp downstream of the 3' end of the mature 25S rRNA and shares several characteristics with previously studied polymerase I terminators in the vertebrates. For example, the yeast terminator is orientation dependent, is inhibited by its own sequence, and forms RNA 3' ends 17 +/- 2 bp upstream of an essential protein binding site. The recognition sequence for binding of the previously cloned REB1 protein (Q. Ju, B. E. Morrow, and J. R. Warner, Mol. Cell. Biol. 10:5226-5234, 1990) is an essential component of the terminator. In addition, the efficiency of termination depends upon sequence context extending at least 12 bp upstream of the REB1 site.

Cloning and sequencing of Octopus dofleini hemocyanin cDNA: derived sequences of functional units Ode and Odf

A number of additional cDNA clones coding for portions of the very large polypeptide chain of Octopus dofleini hemocyanin were isolated and sequenced. These data reveal two very similar coding sequences, which we have denoted "A-type" and "G-type." We have obtained complete A-type sequences coding for functional units Ode and Odf; consequently a total of three such unit sequences are now known from a single subunit of one molluscan hemocyanin. This presents the opportunity to make sequence comparisons within one hemocyanin subunit. Domains within one subunit show on the average 42% identity in amino acid residues; corresponding functional units from hemocyanins of different species show degrees of identity of 53-75%. Therefore, molluscan hemocyanins already existed before the individual molluscan classes diverged in the early Cambrian. Sequence comparisons of molluscan hemocyanins with arthropodan hemocyanins and tyrosinases allow us to identify the ligands of the "Copper B" site with high probability. Possible ligands for the "Copper A" site are proposed, based on sequence comparisons between molluscan hemocyanins and tyrosinases. Besides two histidine side chains, a methionine side chain might be involved in binding of Copper A, a result not in conflict with spectroscopic studies.

cDNA cloning of the Octopus dofleini hemocyanin: sequence of the carboxyl-terminal domain

A cDNA library was constructed in pUC 19, using poly(A+) RNA purified from Octopus dofleini branchial gland, which is the site of hemocyanin biosynthesis in cephalopods. The library was screened with an oligonucleotide probe derived from a portion of the partially known sequence of the C-terminal domain of Paroctopus dofleini dofleini. The clone with the longest insert--called pHC1--was sequenced and used as a probe for Northern blotting. It hybridized to a 9.5-kb RNA species, which was also visible as a band after ethidium bromide staining. The cDNA insert (approximately 1200 bp) of pHC1 contained an open reading frame of 1071 bp coding for 357 amino acids. In this insert, a region coding for 42 amino acids from the N-terminal end of the C-terminal domain is missing. These were obtained by sequencing a cloned primer extension product. By comparing our sequence with Helix pomatia beta c-hemocyanin unit D, we found 42.9% identical and 11.5% similar residues. One putative copper binding site (site B) was identified by homology to Helix hemocyanin and arthropodan hemocyanin. The location of a second possible site was identified.

[Differential diagnostic studies using the dermatoscope in selected diseases]

The Zeis dermatoscope can be used beyond its known applications for precise and detailed skin surface examinations of different types of dermatosis. Differential diagnostic problems are solved by comparative observation of efflorescence and efflorescence fields of similar appearance. The examination series presented, the results of which are discussed in detail, is concerned mainly with surface examinations of parapsoriasis en plaques, seborrhea en plaques and the clinically similar early forms of mycosis fungoides. Also mentioned are examinations of lichen sclerosus et atrophicus and circumscribed scleroderma, lichen planus, Hutchinson-Dubreuilh freckle and similarly appearing facial verruca seborrhoica, as well as fresh dispersions of foreign bodies. The didactic value is underlined by color photographs taken of diseased skin and nails with the dermatoscope at various magnifications. Finally, a description is given of possible instrument extensions.

New Instruments and Technique: A NEW "LOOP TRACTOR" FOR USE IN GASTRO-INTESTINAL ANASTOMOSIS

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