Efficient gene knockout and genetic interaction screening using the in4mer CRISPR/Cas12a multiplex knockout platform

Genetic interactions mediate the emergence of phenotype from genotype, but technologies for combinatorial genetic perturbation in mammalian cells are challenging to scale. Here, we identify background-independent paralog synthetic lethals from previous CRISPR genetic interaction screens, and find that the Cas12a platform provides superior sensitivity and assay replicability. We develop the in4mer Cas12a platform that uses arrays of four independent guide RNAs targeting the same or different genes. We construct a genome-scale library, Inzolia, that is ~30% smaller than a typical CRISPR/Cas9 library while also targeting ~4000 paralog pairs. Screens in cancer cells demonstrate discrimination of core and context-dependent essential genes similar to that of CRISPR/Cas9 libraries, as well as detection of synthetic lethal and masking/buffering genetic interactions between paralogs of various family sizes. Importantly, the in4mer platform offers a fivefold reduction in library size compared to other genetic interaction methods, substantially reducing the cost and effort required for these assays.

CRISPR screening identifies BET and mTOR inhibitor synergy in cholangiocarcinoma through serine glycine one carbon

Patients with cholangiocarcinoma have poor clinical outcomes due to late diagnoses, poor prognoses, and limited treatment strategies. To identify drug combinations for this disease, we have conducted a genome-wide CRISPR screen anchored on the bromodomain and extraterminal domain (BET) PROTAC degrader ARV825, from which we identified anticancer synergy when combined with genetic ablation of members of the mTOR pathway. This combination effect was validated using multiple pharmacological BET and mTOR inhibitors, accompanied by increased levels of apoptosis and cell cycle arrest. In a xenograft model, combined BET degradation and mTOR inhibition induced tumor regression. Mechanistically, the 2 inhibitor classes converged on H3K27ac-marked epigenetic suppression of the serine glycine one carbon (SGOC) metabolism pathway, including the key enzymes PHGDH and PSAT1. Knockdown of PSAT1 was sufficient to replicate synergy with single-agent inhibition of either BET or mTOR. Our results tie together epigenetic regulation, metabolism, and apoptosis induction as key therapeutic targets for further exploration in this underserved disease.

Efficient gene knockout and genetic interactions: the IN4MER CRISPR/Cas12a multiplex knockout platform

Genetic interactions mediate the emergence of phenotype from genotype, but initial technologies for combinatorial genetic perturbation in mammalian cells suffer from inefficiency and are challenging to scale. Recent focus on paralog synthetic lethality in cancer cells offers an opportunity to evaluate different approaches and improve on the state of the art. Here we report a meta-analysis of CRISPR genetic interactions screens, identifying a candidate set of background-independent paralog synthetic lethals, and find that the Cas12a platform provides superior sensitivity and assay replicability. We demonstrate that Cas12a can independently target up to four genes from a single guide array, and we build on this knowledge by constructing a genome-scale library that expresses arrays of four guides per clone, a platform we call 'in4mer'. Our genome-scale human library, with only 49k clones, is substantially smaller than a typical CRISPR/Cas9 monogenic library while also targeting more than four thousand paralog pairs, triples, and quads. Proof of concept screens in four cell lines demonstrate discrimination of core and context-dependent essential genes similar to that of state-of-the-art CRISPR/Cas9 libraries, as well as detection of synthetic lethal and masking/buffering genetic interactions between paralogs of various family sizes, a capability not offered by any extant library. Importantly, the in4mer platform offers a fivefold reduction in the number of clones required to assay genetic interactions, dramatically improving the cost and effort required for these studies.

Actin cytoskeleton vulnerability to disulfide stress mediates disulfidptosis

SLC7A11-mediated cystine uptake suppresses ferroptosis yet promotes cell death under glucose starvation; the nature of the latter cell death remains unknown. Here we show that aberrant accumulation of intracellular disulfides in SLC7A11high cells under glucose starvation induces a previously uncharacterized form of cell death distinct from apoptosis and ferroptosis. We term this cell death disulfidptosis. Chemical proteomics and cell biological analyses showed that glucose starvation in SLC7A11high cells induces aberrant disulfide bonds in actin cytoskeleton proteins and F-actin collapse in a SLC7A11-dependent manner. CRISPR screens and functional studies revealed that inactivation of the WAVE regulatory complex (which promotes actin polymerization and lamellipodia formation) suppresses disulfidptosis, whereas constitutive activation of Rac promotes disulfidptosis. We further show that glucose transporter inhibitors induce disulfidptosis in SLC7A11high cancer cells and suppress SLC7A11high tumour growth. Our results reveal that the susceptibility of the actin cytoskeleton to disulfide stress mediates disulfidptosis and suggest a therapeutic strategy to target disulfidptosis in cancer treatment.

PICKLES v3: the updated database of pooled in vitro CRISPR knockout library essentiality screens

PICKLES (https://pickles.hart-lab.org) is an updated web interface to a freely available database of genome-scale CRISPR knockout fitness screens in human cell lines. Using a completely rewritten interface, researchers can explore gene knockout fitness phenotypes across cell lines and tissue types and compare fitness profiles with fitness, expression, or mutation profiles of other genes. The database has been updated to include data from three CRISPR libraries (Avana, Score, and TKOv3), and includes information from 1162 whole-genome screens probing the knockout fitness phenotype of 18 959 genes. Source code for the interface and the integrated database are available for download.

Dynamic rewiring of biological activity across genotype and lineage revealed by context-dependent functional interactions

BACKGROUND

Coessentiality networks derived from CRISPR screens in cell lines provide a powerful framework for identifying functional modules in the cell and for inferring the roles of uncharacterized genes. However, these networks integrate signal across all underlying data and can mask strong interactions that occur in only a subset of the cell lines analyzed.

RESULTS

Here, we decipher dynamic functional interactions by identifying significant cellular contexts, primarily by oncogenic mutation, lineage, and tumor type, and discovering coessentiality relationships that depend on these contexts. We recapitulate well-known gene-context interactions such as oncogene-mutation, paralog buffering, and tissue-specific essential genes, show how mutation rewires known signal transduction pathways, including RAS/RAF and IGF1R-PIK3CA, and illustrate the implications for drug targeting. We further demonstrate how context-dependent functional interactions can elucidate lineage-specific gene function, as illustrated by the maturation of proreceptors IGF1R and MET by proteases FURIN and CPD.

CONCLUSIONS

This approach advances our understanding of context-dependent interactions and how they can be gleaned from these data. We provide an online resource to explore these context-dependent interactions at diffnet.hart-lab.org.

Cardiac rehabilitation and secondary prevention in COVID-19 times: Single center experience

Funding Acknowledgements

Type of funding sources: None.

Background

Cardiac rehabilitation (CR) is a class I treatment for cardiovascular disease, still, underutilization of these services remains. During the coronavirus 2019 (COVID-19) pandemic, an even greater gap in CR care has been present.

Purpose and methods

We aimed to present the cardiac rehabilitation during COVID 19 times in Belgrade. At the beginning of epidemic in Serbia the number of patients in in-house city program was 70 out of 70 beds, with 200 patients who were scheduled (on the waiting list). Similarly to the other countries, we continued to admit only urgent patients with acute coronary settings.

Results

Only one PPCI center in Belgrade (2 million inhabitants plus surrounding area; out of five centers) continue to admit COVID-negative patients with STEMI from 13of March to 11 of May, during the first pick of COVID-19 epidemic in Serbia. Out -patients cardiac rehabilitation programs were stopped. The totals of 80 patients (PCR negative) were transferred to exercised based cardiac rehabilitation secondary prevention program during the first pick of epidemic directly from acute hospital. The majority of patients were males in their 50s. All risk factors were noted and patients were with much less risk factors compared to non- epidemic era. Lipid profile was measured. Six minutes walking test was performed at the beginning and exercise plan was made. Unfortunately, exercise based three weeks in- house cardiac rehabilitation was completed in only 1% of patients while others quite the program.

Conclusion

The COVID-19 pandemic presents a time to highlight the value of home-based models as we search for ways to continue to provide care. Standardization of home based CR models is essential to provide care for a wider range of patients and circumstances in the near future.

Genome-wide In Vivo CNS Screening Identifies Genes that Modify CNS Neuronal Survival and mHTT Toxicity

Unbiased in vivo genome-wide genetic screening is a powerful approach to elucidate new molecular mechanisms, but such screening has not been possible to perform in the mammalian central nervous system (CNS). Here, we report the results of the first genome-wide genetic screens in the CNS using both short hairpin RNA (shRNA) and CRISPR libraries. Our screens identify many classes of CNS neuronal essential genes and demonstrate that CNS neurons are particularly sensitive not only to perturbations to synaptic processes but also autophagy, proteostasis, mRNA processing, and mitochondrial function. These results reveal a molecular logic for the common implication of these pathways across multiple neurodegenerative diseases. To further identify disease-relevant genetic modifiers, we applied our screening approach to two mouse models of Huntington's disease (HD). Top mutant huntingtin toxicity modifier genes included several Nme genes and several genes involved in methylation-dependent chromatin silencing and dopamine signaling, results that reveal new HD therapeutic target pathways.

Abstract B60: Functional genomic landscape of T-cell mediated cytotoxicity

The direct killing of cancer cells by cytotoxic T-lymphocytes (CTL) is critical for achieving effective antitumor immune responses. While several tumor-intrinsic mutations have been identified that promote evasion to CTL killing, there remains a paucity of data cataloging how individual genetic perturbations impact cancer cell fitness under immunotherapeutic selection pressure. Towards this, genetic screens using the CRISPR-Cas9 system have recently been employed, identifying novel intrinsic genetic regulators of cancer immunotherapy fitness. While these initial studies demonstrate the significant potential of unbiased genetic screens for discovery of novel immunotherapy targets, they have been limited in application to a small number of disease models. As such, the degree to which intrinsic genetic perturbations robustly modulate immunotherapy fitness across diverse cancer genotypes remains largely unexplored. To circumvent this knowledge gap, we performed genetic screens across a panel of commonly utilized syngeneic murine cancer cell lines to identify a core set of genes that render cancer cells more sensitive or resistant to CTL killing across diverse genetic backgrounds. An optimized genome-scale gRNA library targeting ~19,000 protein-coding genes in the murine genome (termed mTKO; mouse Toronto Knockout) was created in an analogous manner to our human library. Screens were performed in multiple murine cell lines engineered to express model tumor-associated antigens. Cells were propagated in the presence or absence of preactivated antigen-specific CTLs, and gRNA abundance was quantified by illumina sequencing to identify perturbed genes enriched or depleted in CTL treated versus untreated populations. These screens uncovered known genetic regulators of CTL killing including immune checkpoints (Cd274), antigen presentation machinery (B2m, Tap1/2) and interferon signaling components (Socs1, Jak1/2, Ifngr1/2), benchmarking the utility of this approach. Importantly, we leveraged this dataset to derive a core list of genes whose perturbation significantly modulates cancer-cell fitness to CTL killing across the majority of genotypes screened. Gene set enrichment analysis revealed critical roles for cytokine and TLR signaling, the NF-κB and MAPK pathways as well as the antiviral and antigen presentation machineries. As such, our dataset represents the first step towards a comprehensive understanding of the functional genomic landscape of CTL-mediated cytotoxicity.

Citation Format: Keith Lawson, Xiaoyu Zhang, Cris Sousa, Rummy Akthar, Zi Fan, Eiru Kim, Medina Colic, Amy Tong, Katie Chan, Qian Huang, Xiaowei Wang, Kevin Brown, Michael Aregger, Antonio Finelli, Laurie Ailles, Traver Hart, Gillian Kingsbury, Charles Kung, Jason Moffat. Functional genomic landscape of T-cell mediated cytotoxicity [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B60.

CRISPR/CAS9-based DNA damage response screens reveal gene-drug interactions

DNA damage response (DDR) is critically important for cell survival, genome maintenance, and its defect has been exploited therapeutically in cancer treatment. Many DDR-targeting agents have been generated and have entered the clinic and/or clinical trials. In order to provide a global and unbiased view of DDR network, we designed a focused CRISPR library targeting 365 DDR genes and performed CRISPR screens on the responses to several DDR inhibitors and DNA-damaging agents in 293A cells. With these screens, we determined responsive pathways enriched under treatment with different types of small-molecule agents. Additionally, we showed that POLE3/4-deficient cells displayed enhanced sensitivity to an ATR inhibitor, a PARP inhibitor, and camptothecin. Moreover, by performing DDR screens in isogenic TP53 wild-type and TP53 knock-out cell lines, our results suggest that the performance of our CRISPR DDR dropout screens is independent of TP53 status. Collectively, our findings indicate that CRISPR DDR screens can be used to identify potential targets of small-molecule drugs and reveal that TP53 status does not affect the outcome of these screens.

Chemogenetic interactions in human cancer cells

Chemogenetic profiling enables the identification of genes that enhance or suppress the phenotypic effect of chemical compounds. Using this approach in cancer therapies could improve our ability to predict the response of specific tumor genotypes to chemotherapeutic agents, thus accelerating the development of personalized drug therapy. In the not so distant past, this strategy was only applied in model organisms because there was no feasible technology to thoroughly exploit desired genetic mutations and their impact on drug efficacy in human cells. Today, with the advent of CRISPR gene-editing technology and its application to pooled library screens in mammalian cells, chemogenetic screens are performed directly in human cell lines with high sensitivity and specificity. Chemogenetic profiling provides insights into drug mechanism-of-action, genetic vulnerabilities, and resistance mechanisms, all of which will help to accurately deliver the right drug to the right target in the right patient while minimizing side effects.

Identifying chemogenetic interactions from CRISPR screens with drugZ

BACKGROUND

Chemogenetic profiling enables the identification of gene mutations that enhance or suppress the activity of chemical compounds. This knowledge provides insights into drug mechanism of action, genetic vulnerabilities, and resistance mechanisms, all of which may help stratify patient populations and improve drug efficacy. CRISPR-based screening enables sensitive detection of drug-gene interactions directly in human cells, but until recently has primarily been used to screen only for resistance mechanisms.

RESULTS

We present drugZ, an algorithm for identifying both synergistic and suppressor chemogenetic interactions from CRISPR screens. DrugZ identifies synthetic lethal interactions between PARP inhibitors and both known and novel members of the DNA damage repair pathway, confirms KEAP1 loss as a resistance factor for ERK inhibitors in oncogenic KRAS backgrounds, and defines the genetic context for temozolomide activity.

CONCLUSIONS

DrugZ is an open-source Python software for the analysis of genome-scale drug modifier screens. The software accurately identifies genetic perturbations that enhance or suppress drug activity. Interestingly, analysis of new and previously published data reveals tumor suppressor genes are drug-agnostic resistance genes in drug modifier screens. The software is available at github.com/hart-lab/drugz .

A network of human functional gene interactions from knockout fitness screens in cancer cells

The function of human genes can be strongly inferred from their knockout fitness profiles across hundreds of CRISPR screens, illuminating the modular organization of the cell.

Genetic interactions mediate the emergence of phenotype from genotype. The systematic survey of genetic interactions in yeast showed that genes operating in the same biological process have highly correlated genetic interaction profiles, and this observation has been exploited to infer gene function in model organisms. Such assays of digenic perturbations in human cells are also highly informative, but are not scalable, even with CRISPR-mediated methods. As an alternative, we developed an indirect method of deriving functional interactions. We show that genes having correlated knockout fitness profiles across diverse, non-isogenic cell lines are analogous to genes having correlated genetic interaction profiles across isogenic query strains and similarly imply shared biological function. We constructed a network of genes with correlated fitness profiles across 276 high-quality CRISPR knockout screens in cancer cell lines into a “coessentiality network,” with up to 500-fold enrichment for co-functional gene pairs, enabling strong inference of gene function and highlighting the modular organization of the cell.

Abstract 2192: Single-molecule single-cell DNA sequencing identifies ongoing copy number evolution in BRCA breast cancers

BRCA2 germline mutation carriers have a lifetime risk of 72% for developing invasive breast cancer. Although BRCA2 has been implicated in double-stranded break repair, the role of this mutation in genome evolution and maintaining genome instability during the expansion of the primary tumor mass is not well understood. To investigate these questions, we developed a novel method for single-cell, single-molecule (SCSM) sequencing. SCSM uses a Tn5 transposase to directly fragment and ligate adapters for PCR amplification, thereby omitting the whole-genome-amplification (WGA) step, which introduces technical noise into single-cell sequencing datasets. This approach provides single-molecule data by positional barcoding, reducing WGA artifacts that are typically associated with amplification bias. We further utilize a dual-barcoding approach and acoustic liquid transfer technology to increase throughput (N=384) and reduce cost to $1 per cell using nanoliter volumes. We applied SMSC to sequence copy number profiles from ~1000 single cells from two patients with BRCA2-positive breast tumors. In both cases we identified several major clonal subpopulations that shared a set of truncal CNAs, suggesting that they evolved from a single normal epithelial cell in the breast, not multiple initiating cells. We also identified many small subclonal CNAs that further diversified the major clones, which suggests that copy number evolution was ongoing during the expansion of the primary tumor mass. These data demonstrate the technical feasibility of SMSC sequencing, and further show that minor copy number evolution is ongoing in BRCA-positive breast cancer patients.

Citation Format: Haowei Du, Alexander Davis, Ruli Gao, Medina Colic, Emi Sei, Min Hu, Angelica Gutierrez Barrera, Anna Casasent, Constance Albarracin, Banu Arun, Nicholas E. Navin. Single-molecule single-cell DNA sequencing identifies ongoing copy number evolution in BRCA breast cancers [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 2192.

E-cadherin expression in acquired cholesteatoma

OBJECTIVES

The epithelial cell adhesion molecule E-cadherin is important for maintenance normal tissue architecture and for cell-cell communication and immune cell migration. E-cadherin is also present in cholesteatomas. This study determined E-cadherin expression in acquired cholesteatomas and analyzed its expression according to cholesteatoma clinical and histological characteristics.

METHODS

We investigated E-cadherin expression in 30 samples from operated patients with acquired middle ear cholesteatomas that were classified according to their clinical and histological characteristics. E-cadherin expression in cholesteatoma was determined immunohistochemically. A semi quantitative method was used to determine the index of expression of E-cadherin and t-tests, Mann-Whitney U tests and Spearman correlation analysis were used for statistical analysis.

RESULTS

We found significant expression of E-cadherin on CD1, CD3 total, CD4 (p < 0.05), high expression of E-cadherin on CD8 total and CD19/CD38 lymphocytes (p < 0.01) and very high expression of E-cadherin on mast cells and antigen-presenting cells, including Langerhans cells (p < 0.005). We graduated results as no statistically significant (p>0.05), statistically significant (0.05 > p > 0.01), highly statistically significant (0.01 > p > 0.005) and very highly statistically significant (p < 0.005).

CONCLUSION

E-cadherin expression was the same in the cholesteatoma matrix in all samples. There were no differences in expression according to the clinical and histological characteristics of the cholesteatomas.

The impact of Trichinella spiralis excretory-secretory products on dendritic cells

Parasitic nematode Trichinella spiralis exert immunomodulatory effect on the host immune response through excretory-secretory products (ES L1) released from the encysted muscle larvae. Rat bone-marrow derived dendritic cells (DCs) stimulated with ES L1 antigens acquire semi-matured status and induce Th2 and regulatory responses in vitro and in vivo. Priming naïve T cells in vitro with ES L1 pulsed DCs caused strong Th2 polarization, accompanied by elevated production of regulatory cytokines IL-10 and TGF-β and no increase in the proportion of CD4+CD25+Foxp3+ among the effector T cell population. In vivo T cell priming resulted in mixed Th1/Th2 cytokine response, with the dominance of the Th2 type and elevated levels of regulatory cytokines. Significant increase in the proportion of CD4+CD25+Foxp3+ cells was found among recipient's spleen cells. We have achieved to create immune status characteristic for the live infection by in vivo application of DCs educated with ES L1 antigens.

Personality traits and PTSD after experiencing civilian war-related trauma among women in Croatia

Introduction

Although many studies report that neuroticism and introversion predispose people to PTSD after exposure to traumatic event, the relationship between personality traits and PTSD is still vague. Also, little attention has been given to posttraumatic responses of civilians and especially women after war circumstances.

Objectives

To explore the relationships between basic personality traits and PTSD among female civilians who have experienced war- related trauma.

Aims

To investigate whether women with current PTSD, PTSD in remission, and those who did not develop PTSD differ in neuroticism, extroversion, openness to experience, agreeableness and conscientiousness.

Methods

The research is a part of a larger study „Psychobiology of PTSD”. CAPS and NEO PI-R were administrated to 395 female participants: 61 participants have current PTSD, 124 PTSD in remission and 108 never developed PTSD after experiencing at least one civilian war related traumatic event. The control group consisted of 101 women with no war related trauma.

Results

Four groups significantly differ on four out of five major domains of personality (one way ANOVA). Women with current PTSD and PTSD in remission have significantly higher scores on neuroticism (F = 25,170, p = ,000). Non PTSD group and controls show significantly higher scores on extroversion (F = 29,980, p = ,000) and on openness to experience (F = 18,421, p = ,000). Participants with current PTSD score have significantly lower scores on conscientiousness in comparison to the other three groups (5,672, p = ,001).

Conclusion

According to our results, personality traits are in significant relationship with PTSD development in female civilians with war related traumatization.

Differentiation and function of human monocyte-derived dendritic cells under the influence of leflunomide

Leflunomide is an immunosuppressive drug effective in experimental models of transplantation and autoimmune diseases and in the treatment of active rheumatoid arthritis (RA). Having in mind that it has been shown that some other immunosuppressive drugs (glucocorticoids, mycophenolate mofetil, sirolimus etc.) impair dendritic cell (DC) phenotype and function, we investigated the effect of A77 1726, an active metabolite of leflunomide, on the differentiation and function of human monocyte-derived dendritic cells (MDDC) in vitro. Immature MDDC were generated by cultivating monocytes in medium supplemented with GM-CSF and IL-4. To induce maturation, immature MDDC were cultured for 2 additional days with LPS. A77 1726 (100 ?M) was added at the beginning of cultivation. Flow cytometric analysis showed that MDDC differentiated in the presence of A77 1726 exhibited an altered phenotype, with a down-regulated surface expression of CD80, CD86, CD54 and CD40 molecules. Furthermore, the continuous presence of A77 1726 during differentiation and maturation prevented successful maturation, judging by the decreased expression of maturation marker CD83, costimulatory and adhesive molecules on A77 1726-treated mature MDDC. In addition, A77 1726-pretreated MDDC exhibited a poor stimulatory capacity of the allogeneic T cells and a low production of IL-10 and IL-18. These data suggest that leflunomide impairs the differentiation, maturation and function of human MDDC in vitro, which is an additional mechanism of its immunosuppressive effect.

Characterization of rat bone marrow dendritic cells initially primed by Trichinella spiralis antigens

Pathogen-derived products have the capacity to induce maturation of bone marrow-derived dendritic cells (BMDCs)into populations of effectors cells that polarize Th cells toward Th1 or Th2 phenotype via different mechanisms. Since those mechanisms are not entirely clear for helminths, and almost completely unknown for Trichinella spiralis(TS), we started an investigation of the effects of TS antigens (four different antigens isolated from all three life-cycle stages of parasite)on maturation of BMDCs and their potential to present TS antigens. The expression of MHC class II, costimulatory molecules CD86, CD54, IL-10 and IL-12p70 cytokine production were measured after 2 days of BMDCs cultivation with TS antigens. While parasitic antigens did not significantly alter the expression of MHC II, most of them, except crude muscle larvae antigens, up-regulated the expression of costimulatory molecules. BMDCs, primed with all TS antigens, released increased amounts of IL-10 and decreased amounts of IL-12p70. BMDCs, primed with TS antigens, induced significant proliferation of syngeneic TS sensitized lymph nodes cells and also stimulated the production of IL-4 by T cells purified from of TS infected DA rats. The results indicate that TS stimulated BMDCs leads to the polarization of the immune response towards regulatory and Th2 type.

The application of collagen sheet in open wound healing*

The aim of this paper is describe the application of desamidated collagen as a biomaterial in order to evaluate the utility of collagen, particularly as a drug delivery device, as a haemostat, and as a wound cover. We also evaluated the utility of vitamin A, vitamin C, 50% glucose, and gentamicin locally applied onto the open wound. Any biomaterial should ensure non-toxicity to the biological environment where it is applied. We point out the utility of vitamin A, vitamin C, 50% glucose, and gentamicin locally applied onto the open wound with a biological covering. Collagen sheet is becoming evident in our ongoing studies. We are convinced that collagen sheets are very useful in first- and second-degree burns. The cost factor comes down and the pain associated with dressing can be avoided. Especially in children it is very useful since the trauma of dressing can be avoided.

Mycophenolate mofetil inhibits differentiation, maturation and allostimulatory function of human monocyte-derived dendritic cells

We have studied the effect of mycophenolate mofetil (MMF), a new drug used in prevention of transplant rejection, on differentiation, maturation and allostimulatory activity of human monocyte-derived dendritic cells (MDDC). MDDC were generated in vitro with granulocyte macrophage-colony stimulating factor (GM-CSF) and interleukin (IL)-4 in the presence or absence of MMF. MMF reduced the number of immature MDDC in culture, dose-dependently, by inducing apoptosis and inhibited their stimulatory activity on allogeneic lymphocytes. These changes correlated with down-regulation of co-stimulatory and adhesion molecules such as CD40, CD54, CD80 and CD86. No differences were observed in mannose receptor (MR)-mediated endocytosis, measured by the uptake of fluorescein isothiocyanate (FITC)-dextran. MDDC differentiated in the presence of MMF showed significantly reduced maturation upon stimulation with lipopolysaccharide, as judged by lower expresson of CD83 and co-stimulatory molecules, lower production of tumour necrosis factor (TNF)-alpha, IL-10, IL-12 and IL-18 as well as lower stimulation of alloreactive T cells including naive CD4+ CD45RA+ T cells. In contrast, MDDC matured in the presence of MMF showed a more marked decrease in the FITC-dextran uptake than mature MDDC cultivated without MMF and the phenomenon correlated with down-regulation of the MR expression. These results suggest that MMF impairs differentiation, maturation and function of human MDDC in vitro, which is an additional mechanism of its immunosuppressive effect.

Molecular, cellular and medical aspects of the action of nutraceuticals and small molecules therapeutics: from chemoprevention to new drug development

Dietary supplements, functional foods and their concentrated, sometimes purified, active forms, the so-called nutraceuticals, are becoming increasingly popular throughout the world. Small molecules that regulate signal transduction cascades and gene expression are being tested by many pharmaceutical companies. A rapidly and exponentially growing industry (close to $30 billion in 1999 worldwide) exists to commercialize and exploit this interest. However, the scientific basis of the action of such unproved products is in the very early stages of development. While supporters claim they produce miracle cures, opponents argue that such unproved agents do more harm than good.

Immunostimulatory effect of natural clinoptilolite as a possible mechanism of its antimetastatic ability

PURPOSE

Many biochemical processes are closely related to ion exchange, adsorption, and catalysis. Zeolites reversibly bind small molecules such as oxygen or nitric oxide; they possess size and shape selectivity, the possibility of metalloenzyme mimicry, and immunomodulatory activity. These properties make them interesting for pharmaceutical industry and medicine.

METHODS

The experiments were performed on mice. Different biochemical and molecular methods were used.

RESULTS

Micronized zeolite (MZ) administered by gastric intubation to mice injected with melanoma cells significantly reduced the number of melanoma metastases. In mice fed MZ for 28 days, concentration of lipid-bound sialic acid (LSA) in serum increased, but lipid peroxidation in liver decreased. The lymphocytes from lymph nodes of these mice provoked a significantly higher alogeneic graft-versus-host (GVH) reaction than cells of control mice. After i.p. application of MZ, the number of peritoneal macrophages, as well as their production of superoxide anion, increased. However, NO generation was totally abolished. At the same time, translocation of p65 (NFkappaB subunit) to the nucleus of splenic cells was observed.

CONCLUSION

Here we report antimetastatic and immunostimulatory effect of MZ and we propose a possible mechanism of its action.

[Detection of B-lymphocyte clonality in samples of salivary gland tissue in patients with primary Sjogren syndrome]

Intensive lymphoplasmocytic infiltration with atrophy of glandular tissue structures is the dominant patohistological feature found in exocrine glands of patients with Sjögren syndrome (SS). The infiltrates consist of T and B lymphocyte clusters that make the structures resembling germinal centers, and numerous plasmocytes that are secreting imunoglobulines locally, including autoantibodies. By applying the polymerase chain reaction (PCR) in our study we have shown the existence of dominant B cell clone in salivary glands samples of 4 out of 6 patients with SS, in the absence of clinical, routine laboratory, and patohistological signs of the lymphoma. B lymphocyte clones were detected upon the amplification of gene segment that encoded variable heavy chain immunoglobulin CDR3 region. Finding of single, dominant B lymphocyte clone could be of predictive significance, because these patients are predisposed to non-Hodgkin lymphoma (NHL) for which there is an assumption that it originates out of salivary glands from one of the clusters of proliferating B lymphocytes.

Molecular mechanisms of anticancer activity of natural dietetic products

The efficiency of dietetic supplements in cancer prevention and treatment is a popular and controversial subject of research. New in vitro and in vivo research results indicate that some dietetic supplements do indeed show anticancer activity. The strongest anticancer action has been demonstrated by natural compounds with multifunctional activity. For instance, antioxidants, which also bind to and modulate the activity of protein kinases involved in signal transduction cascades show both cytostatic and cytotoxic activity towards cancer cells. Other activities such as angiogenesis inhibition, nitric oxide synthase inhibition, and pro-oxidants production have also been observed. Catechins and polyphenols from plant extracts such as green tea show the strongest anticancer activity. The initial clinical trials with some flavonoid molecules are already underway.

Proliferation of spleen cells in culture stimulated by 7-thia-8-oxoguanosine: evidence that both B- and T-cells are the targets of its action

7-thia-8-oxoguanosine (immunosine) is a nucleoside analog showing efficient antiviral activity in rodent models as a consequence of enhancement of the immune response. However, little is known about the mechanisms of its action. In this work the effect of immunosine on proliferation of mouse and rat splenocytes in culture was studied. It was found that the compound stimulated proliferation of lymphocytes in a dose-dependent manner without any additional stimuli. The effect is predominantly mediated by interleukin-2 (IL-2) as judged by increased IL-2 production, upregulation of IL-2 receptor alpha (IL-2R alpha) expression and by significant inhibition (60-75%) of cell proliferation by anti-IL-2R alpha monoclonal antibodies (mAbs). Immunosine also stimulated proliferation both of T- and B-cells purified by immunomagnetic sorting. The response of B-cells was much higher than that of T-cells. The stimulatory effect of immunosine on both lymphocyte subpopulations was further increased by the addition of enriched splenic antigen-presenting cells or purified dendritic cells. Proliferation of purified T-cells to immunosine was also significantly potentiated by an anti-alpha beta T-cell receptor mAb (R 73). All these data suggest that T-, B- and accessory cells in splenic cultures are the targets of immunosine action.

Plastic-to-Brittle Transition of Consolidated Bodies: Effect of Counterion Size

The effect of ion size on the force necessary to remove counterions from the surface when particles are forced into contact (primary minimum) was investigated. Alumina slurries dispersed at pH 12 and then coagulated with 0.5 M Li+, Cs+, and tetraethylammonium (TEA+) chlorides were consolidated by pressure filtration at different applied pressures. Uniaxial compression tests were performed to determine the plastic-to-brittle transition pressure for bodies formulated with each of the different counterions. Brittle bodies are produced when particles are pushed together to form a strong touching network. The force required to push particles together is related to the slope of the repulsive potential barrier, with steeper slopes requiring greater force. The consolidation pressure necessary for brittle behavior was greater for slurries with small counterions such as Li+ as compared with Cs+ and TEA+. The results presented here show that the resistance to pushing particles into contact is related to the size of the bare counterion in weakly attractive (salt-coagulated) slurries. That is, the slope of the potential barrier produced when the slurry is formulated with smaller ions is steeper. This result is consistent with the idea that smaller counterions are more strongly bound to the surface, as well as the fact that the repulsion due to the finite size of the ion occurs at smaller interparticle separation distances for the smaller counterions. Copyright 1997Academic Press

Immunosuppression with cyclosporin A alters the thymic microenvironment

The effect of cyclosporin A (CyA) immunosuppression on the murine thymic microenvironment and T lymphocyte development has been analysed using monoclonal antibodies to epithelial and lymphocyte subpopulations, macrophages and major histocompatibility complex (MHC) class II antigens in immunohistochemistry and flow cytometry. The major microenvironmental target for CyA-induced damage was the thymic medulla, where a reduction in all epithelial cell subsets, dendritic cells and macrophages was observed. In contrast, the thymic cortex appeared essentially normal. CyA had no detectable effect on the intensity of microenvironmental expression of MHC class II molecules in either cortex or medulla, although the number of MHC class II positive medullary cells was reduced after CyA treatment. CyA also had a differential effect on the thymic lymphocyte populations where there was little change in the Thy-1 bright, CD5 dull, CD4+, CD8+ cortical thymocytes but a depletion of the Thy-1 dull, CD5 bright, CD4 or CD8 single-positive medullary cells. This lymphocyte loss may be due partly to increased migration from thymus to spleen and other peripheral lymphoid organs, and partly to a block in the differentiation stage from cortical to medullary lymphocyte. The thymic microenvironment and lymphocyte subpopulations recover rapidly after cessation of CyA treatment, although there may be longer term functional defects resulting from the CyA-induced injury.

Ultrastructural study of macrophages in the rat thymus, with special reference to the cortico-medullary zone

Electron microscopic study of the normal rat thymus has demonstrated that macrophages with different ultrastructural features are positioned in the thymic cortex, in the cortico-medullary zone and in the medulla. Phagocytic cells, containing necrotic lymphocytes in various stages of degradation, are distributed throughout the thymic cortex. The cortico-medullary zone, in contrast, is populated with macrophages displaying specific ultrastructural features. These cells contain numerous vacuolar inclusions of different size, filled with homogeneous, flocculent material of very low electron density. The dense bodies, occasionally positioned to the inner side of the vacuolar membrane, selectively contrast with silver methenamine and contain polysaccharides, as demonstrated by the thiocarbohydrazide-silver proteinate method. Very rarely, these cells contain phagocytosed lymphocyte remnants. The predominant type of mononuclear phagocytic cells in the thymic medulla are the interdigitating cells.