Molecular pathways of senescence regulate placental structure and function

The placenta is an autonomous organ that maintains fetal growth and development. Its multinucleated syncytiotrophoblast layer, providing fetal nourishment during gestation, exhibits characteristics of cellular senescence. We show that in human placentas from pregnancies with intrauterine growth restriction, these characteristics are decreased. To elucidate the functions of pathways regulating senescence in syncytiotrophoblast, we used dynamic contrast‐enhanced MRI in mice with attenuated senescence programs. This approach revealed an altered dynamics in placentas of p53^−/−, Cdkn2a^−/−, and Cdkn2a^−/−;p53^−/− mice, accompanied by histopathological changes in placental labyrinths. Human primary syncytiotrophoblast upregulated senescence markers and molecular pathways associated with cell‐cycle inhibition and senescence‐associated secretory phenotype. The pathways and components of the secretory phenotype were compromised in mouse placentas with attenuated senescence and in human placentas from pregnancies with intrauterine growth restriction. We propose that molecular mediators of senescence regulate placental structure and function, through both cell‐autonomous and non‐autonomous mechanisms.

Impaired immune surveillance accelerates accumulation of senescent cells and aging

Cellular senescence is a stress response that imposes stable cell-cycle arrest in damaged cells, preventing their propagation in tissues. However, senescent cells accumulate in tissues in advanced age, where they might promote tissue degeneration and malignant transformation. The extent of immune-system involvement in regulating age-related accumulation of senescent cells, and its consequences, are unknown. Here we show that Prf1^-/- mice with impaired cell cytotoxicity exhibit both higher senescent-cell tissue burden and chronic inflammation. They suffer from multiple age-related disorders and lower survival. Strikingly, pharmacological elimination of senescent-cells by ABT-737 partially alleviates accelerated aging phenotype in these mice. In LMNA^+/G609G progeroid mice, impaired cell cytotoxicity further promotes senescent-cell accumulation and shortens lifespan. ABT-737 administration during the second half of life of these progeroid mice abrogates senescence signature and increases median survival. Our findings shed new light on mechanisms governing senescent-cell presence in aging, and could motivate new strategies for regenerative medicine.

Telomere Homeostasis and Senescence Markers Are Differently Expressed in Placentas From Pregnancies With Early- Versus Late-Onset Preeclampsia

BACKGROUND

Early-onset preeclampsia (EOPE; <34 weeks' gestation) usually has more severe morbidity for the mother and fetus compared to late-onset preeclampsia (LOPE). Telomere homeostasis is disrupted in preeclampsia (PE) and senescence markers are increased. The pathophysiologic differences between early and LOPE are not fully unraveled yet.

METHODS

We studied placental biopsies from 7 pregnancies with EOPE, 6 pregnancies with LOPE, and 13 healthy gestational age-matched controls. Telomere length and aggregate formation were assessed using qualitative fluorescence in situ hybridization and electronic quantitative methods. Senescence markers were evaluated including senescence-associated heterochromatin foci, β-galactosidase (SAβ-Gal), and P16 staining, as was the expression of P16 complementary DNA (cDNA) using real-time quantitative polymerase chain reaction (RT-qPCR).

RESULTS

There were no differences in maternal age, gravidity, parity, body mass index, and mode of conception between the study and the control groups. The percentage of trophoblasts with short telomeres was higher in placental samples from EOPE (52.61% [12.27%]) versus LOPE (28.72% [10.14%]); both were higher compared to controls (7.53% [5.14%], P = .03). Aggregate formation was enhanced in EOPE (8.72% [2.49%]) compared to LOPE (4.54% [1.45%]); both were higher than in healthy controls (2.72% [1.08%], P = .03). Trophoblasts from EOPE versus LOPE were more likely to stain positive for SAβ-Gal and P16 compared to controls (P < .001). P16 cDNA expression assayed by RT-qPCR was 7.51 times higher in EOPE compared to controls and 5.86 times higher than in LOPE.

CONCLUSIONS

Impaired telomere homeostasis and senescence markers are more prominent in EOPE versus LOPE. These findings may contribute to our understanding of the pathophysiology and explain their different clinical presentations and outcomes.

An oligoclonal antibody durably overcomes resistance of lung cancer to third-generation EGFR inhibitors

Epidermal growth factor receptor (EGFR) mutations identify patients with lung cancer who derive benefit from kinase inhibitors. However, most patients eventually develop resistance, primarily due to the T790M second-site mutation. Irreversible inhibitors (e.g., osimertinib/AZD9291) inhibit T790M-EGFR, but several mechanisms, including a third-site mutation, C797S, confer renewed resistance. We previously reported that a triple mixture of monoclonal antibodies, 3×mAbs, simultaneously targeting EGFR, HER2, and HER3, inhibits T790M-expressing tumors. We now report that 3×mAbs, including a triplet containing cetuximab and trastuzumab, inhibits C797S-expressing tumors. Unlike osimertinib, which induces apoptosis, 3×mAbs promotes degradation of the three receptors and induces cellular senescence. Consistent with distinct mechanisms, treatments combining 3×mAbs plus sub-inhibitory doses of osimertinib synergistically and persistently eliminated tumors. Thus, oligoclonal antibodies, either alone or in combination with kinase inhibitors, might preempt repeated cycles of treatment and rapid emergence of resistance.

Senescence and Telomere Homeostasis Might Be Involved in Placenta Percreta-Preliminary Investigation

OBJECTIVE

Placenta percreta (PP) is an abnormal condition of trophoblast maturation and terminal differentiation through the uterine wall. We opted to study telomere homeostasis and senescence expression in trophoblasts from PP, the most severe subgroup of placenta accreta.

STUDY DESIGN

Paraffin-embedded placental biopsies from pregnancies with percreta and normal placentation, matched by gestational age at delivery, were assessed for telomere length, aggregates, and senescence-associated heterochromatin foci using quantitative fluorescence in situ hybridization. Cyclin-dependent kinase inhibitors p21, p15, p16, and the tumor suppressor protein p53, known senescence-related markers, were assessed using immunohistochemical staining.

RESULTS

Short telomeres were found more often in trophoblasts from the samples of PP (n = 9) compared to controls (n = 8; 54% ± 20% vs 2.3% ± 1.16%, respectively; P < .05). More cells with telomere aggregates (18.3% ± 6.9%) were observed in the PP than in the control group (4.8% ± 5.4%; P = .0005). The percentage of nucleic senescence-associated heterochromatin foci in the PP and control samples was similar (10.9% ± 10.4% vs 10.7% ± 15%, respectively; P = .97). Immunohistochemistry of senescence markers was expressed differently in PP compared to the controls: higher p15 expression (46.42% ± 15.2% vs 36.63% ± 12.2%, P = .004), higher p21 expression (59.8% ± 22.1% vs 47.5% ± 21.9%, P = .011), lower p16 expression (54.8% ± 26.3% vs 73.4% ± 18.9%, P = .000), and lower p53 expression (24.4% ± 33.8% vs 34% ± 14.4%, P = .000).

CONCLUSION

Placenta percreta exhibits telomere alterations and changes in expression of several senescence markers. These might be related to altered trophoblast invasion maturation and placental detachment postpartum.

p21 maintains senescent cell viability under persistent DNA damage response by restraining JNK and caspase signaling

Cellular senescence is a permanent state of cell cycle arrest that protects the organism from tumorigenesis and regulates tissue integrity upon damage and during tissue remodeling. However, accumulation of senescent cells in tissues during aging contributes to age‐related pathologies. A deeper understanding of the mechanisms regulating the viability of senescent cells is therefore required. Here, we show that the CDK inhibitor p21 (CDKN1A) maintains the viability of DNA damage‐induced senescent cells. Upon p21 knockdown, senescent cells acquired multiple DNA lesions that activated ataxia telangiectasia mutated (ATM) and nuclear factor (NF)‐κB kinase, leading to decreased cell survival. NF‐κB activation induced TNF‐α secretion and JNK activation to mediate death of senescent cells in a caspase‐ and JNK‐dependent manner. Notably, p21 knockout in mice eliminated liver senescent stellate cells and alleviated liver fibrosis and collagen production. These findings define a novel pathway that regulates senescent cell viability and fibrosis.

Senescent cells communicate via intercellular protein transfer

Biran et al. show that senescent cells directly transfer proteins to neighboring cells and that this process facilitates immune surveillance of senescent cells by NK cells. The transfer is strictly dependent on cell–cell contact and CDC42-regulated actin polymerization and is mediated at least partially by cytoplasmic bridges. These findings reveal a novel mode of intercellular communication by which senescent cells regulate their immune surveillance and might impact tumorigenesis and tissue aging.

Mammalian cells mostly rely on extracellular molecules to transfer signals to other cells. However, in stress conditions, more robust mechanisms might be necessary to facilitate cell–cell communications. Cellular senescence, a stress response associated with permanent exit from the cell cycle and the development of an immunogenic phenotype, limits both tumorigenesis and tissue damage. Paradoxically, the long-term presence of senescent cells can promote tissue damage and aging within their microenvironment. Soluble factors secreted from senescent cells mediate some of these cell-nonautonomous effects. However, it is unknown whether senescent cells impact neighboring cells by other mechanisms. Here we show that senescent cells directly transfer proteins to neighboring cells and that this process facilitates immune surveillance of senescent cells by natural killer (NK) cells. We found that transfer of proteins to NK and T cells is increased in the murine preneoplastic pancreas, a site where senescent cells are present in vivo. Proteomic analysis and functional studies of the transferred proteins revealed that the transfer is strictly dependent on cell–cell contact and CDC42-regulated actin polymerization and is mediated at least partially by cytoplasmic bridges. These findings reveal a novel mode of intercellular communication by which senescent cells regulate their immune surveillance and might impact tumorigenesis and tissue aging.

Tracking global changes induced in the CD4 T-cell receptor repertoire by immunization with a complex antigen using short stretches of CDR3 protein sequence

Motivation: The clonal theory of adaptive immunity proposes that immunological responses are encoded by increases in the frequency of lymphocytes carrying antigen-specific receptors. In this study, we measure the frequency of different T-cell receptors (TcR) in CD4 + T cell populations of mice immunized with a complex antigen, killed Mycobacterium tuberculosis, using high throughput parallel sequencing of the TcRβ chain. Our initial hypothesis that immunization would induce repertoire convergence proved to be incorrect, and therefore an alternative approach was developed that allows accurate stratification of TcR repertoires and provides novel insights into the nature of CD4 + T-cell receptor recognition.

Results: To track the changes induced by immunization within this heterogeneous repertoire, the sequence data were classified by counting the frequency of different clusters of short (3 or 4) continuous stretches of amino acids within the antigen binding complementarity determining region 3 (CDR3) repertoire of different mice. Both unsupervised (hierarchical clustering) and supervised (support vector machine) analyses of these different distributions of sequence clusters differentiated between immunized and unimmunized mice with 100% efficiency. The CD4 + TcR repertoires of mice 5 and 14 days postimmunization were clearly different from that of unimmunized mice but were not distinguishable from each other. However, the repertoires of mice 60 days postimmunization were distinct both from naive mice and the day 5/14 animals. Our results reinforce the remarkable diversity of the TcR repertoire, resulting in many diverse private TcRs contributing to the T-cell response even in genetically identical mice responding to the same antigen. However, specific motifs defined by short stretches of amino acids within the CDR3 region may determine TcR specificity and define a new approach to TcR sequence classification.

Availability and implementation: The analysis was implemented in R and Python, and source code can be found in Supplementary Data.

Contact:b.chain@ucl.ac.uk

Supplementary information:Supplementary data are available at Bioinformatics online.

T-cell receptor repertoires share a restricted set of public and abundant CDR3 sequences that are associated with self-related immunity

The T-cell receptor (TCR) repertoire is formed by random recombinations of genomic precursor elements; the resulting combinatorial diversity renders unlikely extensive TCR sharing between individuals. Here, we studied CDR3β amino acid sequence sharing in a repertoire-wide manner, using high-throughput TCR-seq in 28 healthy mice. We uncovered hundreds of public sequences shared by most mice. Public CDR3 sequences, relative to private sequences, are two orders of magnitude more abundant on average, express restricted V/J segments, and feature high convergent nucleic acid recombination. Functionally, public sequences are enriched for MHC-diverse CDR3 sequences that were previously associated with autoimmune, allograft, and tumor-related reactions, but not with anti-pathogen-related reactions. Public CDR3 sequences are shared between mice of different MHC haplotypes, but are associated with different, MHC-dependent, V genes. Thus, despite their random generation process, TCR repertoires express a degree of uniformity in their post-genomic organization. These results, together with numerical simulations of TCR genomic rearrangements, suggest that biases and convergence in TCR recombination combine with ongoing selection to generate a restricted subset of self-associated, public CDR3 TCR sequences, and invite reexamination of the basic mechanisms of T-cell repertoire formation.

Cell fusion induced by ERVWE1 or measles virus causes cellular senescence

Cellular senescence limits proliferation of potentially detrimental cells, preventing tumorigenesis and restricting tissue damage. However, the function of senescence in nonpathological conditions is unknown. Here, Krizhanovsky and colleagues discover a new pathway to activate senescence cell fusion. The authors find that fusion-induced senescence occurs during embryonic development in the placenta. A counterpart of this process is also observed after infection by the measles virus. The results suggest that fusion-induced senescence is essential during development, and reuse of this program later in life protects agains viral infections.

Cellular senescence limits proliferation of potentially detrimental cells, preventing tumorigenesis and restricting tissue damage. However, the function of senescence in nonpathological conditions is unknown. We found that the human placental syncytiotrophoblast exhibited the phenotype and expressed molecular markers of cellular senescence. During embryonic development, ERVWE1-mediated cell fusion results in formation of the syncytiotrophoblast, which serves as the maternal/fetal interface at the placenta. Expression of ERVWE1 caused cell fusion in normal and cancer cells, leading to formation of hyperploid syncytia exhibiting features of cellular senescence. Infection by the measles virus, which leads to cell fusion, also induced cellular senescence in normal and cancer cells. The fused cells activated the main molecular pathways of senescence, the p53- and p16–pRb-dependent pathways; the senescence-associated secretory phenotype; and immune surveillance-related proteins. Thus, fusion-induced senescence might be needed for proper syncytiotrophoblast function during embryonic development, and reuse of this senescence program later in life protects against pathological expression of endogenous fusogens and fusogenic viral infections.

CD4(+) T Cell-Receptor Repertoire Diversity is Compromised in the Spleen but Not in the Bone Marrow of Aged Mice Due to Private and Sporadic Clonal Expansions

Reduction in T cell receptor (TCR) diversity in old age is considered as a major cause for immune complications in the elderly population. Here, we explored the consequences of aging on the TCR repertoire in mice using high-throughput sequencing (TCR-seq). We mapped the TCRβ repertoire of CD4+ T cells isolated from bone marrow (BM) and spleen of young and old mice. We found that TCRβ diversity is reduced in spleens of aged mice but not in their BM. Splenic CD4+ T cells were also skewed toward an effector memory phenotype in old mice, while BM cells preserved their memory phenotype with age. Analysis of Vβ and Jβ gene usage across samples, as well as comparison of CDR3 length distributions, showed no significant age dependent changes. However, comparison of the frequencies of amino-acid (AA) TCRβ sequences between samples revealed repertoire changes that occurred at a more refined scale. The BM-derived TCRβ repertoire was found to be similar among individual mice regardless of their age. In contrast, the splenic repertoire of old mice was not similar to those of young mice, but showed an increased similarity with the BM repertoire. Each old-mouse had a private set of expanded TCRβ sequences. Interestingly, a fraction of these sequences was found also in the BM of the same individual, sharing the same nucleotide sequence. Together, these findings show that the composition and phenotype of the CD4+ T cell BM repertoire are relatively stable with age, while diversity of the splenic repertoire is severely reduced. This reduction is caused by idiosyncratic expansions of tens to hundreds of T cell clonotypes, which dominate the repertoire of each individual. We suggest that these private and abundant clonotypes are generated by sporadic clonal expansions, some of which correspond to pre-existing BM clonotypes. These organ- and age-specific changes of the TCRβ repertoire have implications for understanding and manipulating age-associated immune decline.

CNS-specific immunity at the choroid plexus shifts toward destructive Th2 inflammation in brain aging

The adaptive arm of the immune system has been suggested as an important factor in brain function. However, given the fact that interactions of neurons or glial cells with T lymphocytes rarely occur within the healthy CNS parenchyma, the underlying mechanism is still a mystery. Here we found that at the interface between the brain and blood circulation, the epithelial layers of the choroid plexus (CP) are constitutively populated with CD4(+) effector memory cells with a T-cell receptor repertoire specific to CNS antigens. With age, whereas CNS specificity in this compartment was largely maintained, the cytokine balance shifted in favor of the T helper type 2 (Th2) response; the Th2-derived cytokine IL-4 was elevated in the CP of old mice, relative to IFN-γ, which decreased. We found this local cytokine shift to critically affect the CP epithelium, triggering it to produce the chemokine CCL11 shown to be associated with cognitive dysfunction. Partial restoration of cognitive ability in aged mice, by lymphopenia-induced homeostasis-driven proliferation of memory T cells, was correlated with restoration of the IL-4:IFN-γ ratio at the CP and modulated the expression of plasticity-related genes at the hippocampus. Our data indicate that the cytokine milieu at the CP epithelium is affected by peripheral immunosenescence, with detrimental consequences to the aged brain. Amenable to immunomodulation, this interface is a unique target for arresting age-related cognitive decline.

Glatiramer acetate reduces Th-17 inflammation and induces regulatory T-cells in the CNS of mice with relapsing-remitting or chronic EAE

The aim of this study was to identify cell populations relevant to pathogenesis and repair within the injured CNS in mice that recovered from experimental autoimmune encephalomyelitis (EAE). We demonstrate that in two EAE models, with either relapsing-remitting or chronic course, T-cells and resident activated microglia manifested extensive IL-17 expression, with apparent localization within regions of myelin loss. In mice treated with glatiramer acetate (GA, Copaxone), even when treatment started after disease exacerbation, CNS inflammation and Th-17 occurrence were drastically reduced, with parallel elevation in T-regulatory cells, indicating the immunomodulatory therapeutic consequences of GA treatment in situ.

PML, YAP, and p73 are components of a proapoptotic autoregulatory feedback loop

p73 has been identified as a structural and functional homolog of the tumor suppressor p53. The transcriptional coactivator Yes-associated protein (YAP) has been demonstrated to interact with and to enhance p73-dependent apoptosis in response to DNA damage. Here, we show the existence of a proapoptotic autoregulatory feedback loop between p73, YAP, and the promyelocytic leukemia (PML) tumor suppressor gene. We demonstrate that PML is a direct transcriptional target of p73/YAP, and we show that PML transcriptional activation by p73/YAP is under the negative control of the proto-oncogenic Akt/PKB kinase. Importantly, we find that PML and YAP physically interact through their PVPVY and WW domains, respectively, causing PML-mediated sumoylation and stabilization of YAP. Hence, we determine a mechanistic pathway in response to DNA damage that could have relevant implications for the treatment of human cancer.

MIR-451 and Imatinib mesylate inhibit tumor growth of Glioblastoma stem cells

We examined the microRNA profiles of Glioblastoma stem (CD133+) and non-stem (CD133-) cell populations and found up-regulation of several miRs in the CD133- cells, including miR-451, miR-486, and miR-425, some of which may be involved in regulation of brain differentiation. Transfection of GBM cells with the above miRs inhibited neurosphere formation and transfection with the mature miR-451 dispersed neurospheres, and inhibited GBM cell growth. Furthermore, transfection of miR-451 combined with Imatinib mesylate treatment had a cooperative effect in dispersal of GBM neurospheres. In addition, we identified a target site for SMAD in the promoter region of miR-451 and showed that SMAD3 and 4 activate such a promoter-luciferase construct. Transfection of SMAD in GBM cells inhibited their growth, suggesting that SMAD may drive GBM stem cells to differentiate to CD133- cells through up-regulation of miR-451 and reduces their tumorigenicity. Identification of additional miRs and target genes that regulate GBM stem cells may provide new potential drugs for therapy.

A rapid assay for drug sensitivity of glioblastoma stem cells

Glioblastoma (GBM) is a highly infiltrating, aggressive brain cancer with no available curative treatment. We developed a rapid assay for assessing the effect of various drugs on GBM stem cells. The assay uses a small number of separated CD133+ cells (20,000 in 0.2 ml) in 96-well plate that form neurospheres within 1-2 days. Various drugs disperse the neurospheres within 24-36 h, which can be quantified microscopically. We used the GBM cell line A-172 to develop the conditions for the assay, utilizing Gleevec, the gamma-secretase inhibitor DAPT, and the anti-bacterial peptide amph1D. The results show dispersion of the neurospheres leading to cell death, at relatively low drugs concentrations (<25 microM). Drug combination showed a synergistic effect and disruption of neurospheres under lower concentrations. We applied this assay to the CD133+ cells of surgical specimens from three patients that showed similar results. This assay facilitates a rapid test of drugs on small amounts of fractionated patient's GBM stem cells.

Gene expression profiles of AML derived stem cells; similarity to hematopoietic stem cells

Tumors contain a fraction of cancer stem cells that maintain the propagation of the disease. The CD34(+)CD38(-) cells, isolated from acute myeloid leukemia (AML), were shown to be enriched leukemic stem cells (LSC). We isolated the CD34(+)CD38(-) cell fraction from AML and compared their gene expression profiles to the CD34(+)CD38(+) cell fraction, using microarrays. We found 409 genes that were at least twofold over- or underexpressed between the two cell populations. These include underexpression of DNA repair, signal transduction and cell cycle genes, consistent with the relative quiescence of stem cells, and chromosomal aberrations and mutations of leukemic cells. Comparison of the LSC expression data to that of normal hematopoietic stem cells (HSC) revealed that 34% of the modulated genes are shared by both LSC and HSC, supporting the suggestion that the LSC originated within the HSC progenitors. We focused on the Notch pathway since Jagged-2, a Notch ligand was found to be overexpressed in the LSC samples. We show that DAPT, an inhibitor of gamma-secretase, a protease that is involved in Jagged and Notch signaling, inhibits LSC growth in colony formation assays. Identification of additional genes that regulate LSC self-renewal may provide new targets for therapy.

The UVB-induced gene expression profile of human epidermis in vivo is different from that of cultured keratinocytes

In order to obtain a comprehensive picture of the molecular events regulating cutaneous photodamage of intact human epidermis, suction blister roofs obtained after a single dose of in vivo ultraviolet (UV)B exposure were used for microarray profiling. We found a changed expression of 619 genes. Half of the UVB-regulated genes had returned to pre-exposure baseline levels at 72 h, underscoring the transient character of the molecular cutaneous UVB response. Of special interest was our finding that several of the central p53 target genes remained unaffected following UVB exposure in spite of p53 protein accumulation. We next compared the in vivo expression profiles of epidermal sheets to that of cultured human epidermal keratinocytes exposed to UVB in vitro. We found 1931 genes that differed in their expression profiles between the two groups. The expression profile in intact epidemis was geared mainly towards DNA repair, whereas cultured keratinocytes responded predominantly by activating genes associated with cell-cycle arrest and apoptosis. These differences in expression profiles might reflect differences between mature differentiating keratinocytes in the suprabasal epidermal layers versus exponentially proliferating keratinocytes in cell culture. Our findings show that extreme care should be taken when extrapolating from findings based on keratinocyte cultures to changes in intact epidermis.

Coupled two-way clustering analysis of breast cancer and colon cancer gene expression data

We present and review coupled two-way clustering, a method designed to mine gene expression data. The method identifies submatrices of the total expression matrix, whose clustering analysis reveals partitions of samples (and genes) into biologically relevant classes. We demonstrate, on data from colon and breast cancer, that we are able to identify partitions that elude standard clustering analysis.

AVAILABILITY

Free, at http://ctwc.weizmann.ac.il..

SUPPLEMENTARY INFORMATION

http://www.weizmann.ac.il/physics/complex/compphys/bioinfo2/

Inhibition of p53-induced apoptosis without affecting expression of p53-regulated genes

Using DNA microarray and clustering of expressed genes we have analyzed the mechanism of inhibition of wild-type p53-induced apoptosis by the cytokine interleukin 6 (IL-6) and the calcium mobilizer thapsigargin (TG). Clustering analysis of 1,786 genes, the expression level of which changed after activation of wild-type p53 in the absence or presence of IL-6 or TG, showed that these compounds did not cause a general inhibition of the ability of p53 to up-regulate or down-regulate gene expression. Expression of various p53 targets implicated as mediators of p53-induced apoptosis was also not affected by IL-6 or TG. These compounds thus can bypass the effect of wild-type p53 on gene expression and inhibit apoptosis. IL-6 and TG activated different p53-independent pathways of gene expression that include up-regulation of antiapoptotic genes. IL-6 and TG also activated different differentiation-associated genes. The ability of compounds such as cytokines and calcium mobilizers to inhibit p53-mediated apoptosis without generally inhibiting gene expression regulated by p53 can facilitate tumor development and tumor resistance to radiation and chemotherapy in cells that retain wild-type p53.

Genome-wide comparison of human keratinocyte and squamous cell carcinoma responses to UVB irradiation: implications for skin and epithelial cancer

To gain insight into the transformation of epidermal cells into squamous carcinoma cells (SCC), we compared the response to ultraviolet B radiation (UVB) of normal human epidermal keratinocytes (NHEK) versus their transformed counterpart, SCC, using biological and molecular profiling. DNA microarray analyses (Affymetrix), approximately 12000 genes) indicated that the major group of upregulated genes in keratinocytes fall into three categories: (i). antiapoptotic and cell survival factors, including chemokines of the CXC/CC subfamilies (e.g. IL-8, GRO-1, -2, -3, SCYA20), growth factors (e.g. HB-EGF, CTGF, INSL-4), and proinflammatory mediators (e.g. COX-2, S100A9), (ii). DNA repair-related genes (e.g. GADD45, ERCC, BTG-1, Histones), and (iii). ECM proteases (MMP-1, -10). The major downregulated genes are DeltaNp63 and PUMILIO, two potential markers for the maintenance of keratinocyte stem cells. NHEK were found to be more resistant than SCC to UVB-induced apoptosis and this resistance was mainly because of the protection from cell death by secreted survival factors, since it can be transferred from NHEK to SCC cultures by the conditioned medium. Whereas the response of keratinocytes to UVB involved regulation of key checkpoint genes (p53, MDM2, p21(Cip1), DeltaNp63), as well as antiapoptotic and DNA repair-related genes - no or little regulation of these genes was observed in SCC. The effect of UVB on NHEK and SCC resulted in upregulation of 251 and 127 genes, respectively, and downregulation of 322 genes in NHEK and 117 genes in SCC. To further analyse these changes, we used a novel unsupervised coupled two-way clustering method that allowed the identification of groups of genes that clearly partitioned keratinocytes from SCC, including a group of genes whose constitutive expression levels were similar before UVB. This allowed the identification of discriminating genes not otherwise revealed by simple static comparison in the absence of UVB irradiation. The implication of the changes in gene profile in keratinocytes for epithelial cancer is discussed.

Isolation and purification of viable Ureaplasma urealyticum cells free from medium components

A procedure was devised to produce Ureaplasma urealyticum preparations free of adsorbed components of the growth medium, which contains high concentrations of serum. The ureaplasmas were cultivated in a medium containing PPLO-serum fraction as a replacement for horse serum. High titres of ureaplasmas (greater than 10(7) c.f.u. ml-1) were obtained. Harvested cells were then purified by Urografin density gradient centrifugation. By use of 3H-labelled ureaplasma cells and 125I-labelled medium components, a distinct band of viable cells devoid of serum constituents was demonstrated. The absence of medium components was verified by immunoblotting cells from this band with antiserum to medium components. Medium components that had been present before the purification procedure were undetectable in the purified cell fraction obtained. The viability of the purified ureaplasma cells represented an 85% recovery rate and their antigenicity, examined with anti-serotype specific antiserum, remained intact. This easy and reproducible procedure can be used to prepare purified ureaplasmas for investigation of ureaplasmal antigens and their expression and/or role in disease.