GPS2 promotes erythroid differentiation in K562 erythroleukemia cells primarily via NCOR1.

G protein pathway suppressor 2 (GPS2) has been shown to play a pivotal role in human and mouse definitive erythropoiesis in an EKLF-dependent manner. However, whether GPS2 affects human primitive erythropoiesis is still unknown. This study demonstrated that GPS2 positively regulates erythroid differentiation in K562 cells, which have a primitive erythroid phenotype. Overexpression of GPS2 promoted hemin-induced hemoglobin synthesis in K562 cells as assessed by the increased percentage of benzidine-positive cells and the deeper red coloration of the cell pellets. In contrast, knockdown of GPS2 inhibited hemin-induced erythroid differentiation of K562 cells. GPS2 overexpression also enhanced erythroid differentiation of K562 cells induced by cytosine arabinoside (Ara-C). GPS2 induced hemoglobin synthesis by increasing the expression of globin and ALAS2 genes, either under steady state or upon hemin treatment. Promotion of erythroid differentiation of K562 cells by GPS2 mainly relies on NCOR1, as knockdown of NCOR1 or lack of the NCOR1-binding domain of GPS2 potently diminished the promotive effect. Thus, our study revealed a previously unknown role of GPS2 in regulating human primitive erythropoiesis in K562 cells.

BRISC is required for optimal activation of NF-κB in Kupffer cells induced by LPS and contributes to acute liver injury.

BRISC (BRCC3 isopeptidase complex) is a deubiquitinating enzyme that has been linked with inflammatory processes, but its role in liver diseases and the underlying mechanism are unknown. Here, we investigated the pathophysiological role of BRISC in acute liver failure using a mice model induced by D-galactosamine (D-GalN) plus lipopolysaccharide (LPS). We found that the expression of BRISC components was dramatically increased in kupffer cells (KCs) upon LPS treatment in vitro or by the injection of LPS in D-GalN-sensitized mice. D-GalN plus LPS-induced liver damage and mortality in global BRISC-null mice were markedly attenuated, which was accompanied by impaired hepatocyte death and hepatic inflammation response. Constantly, treatment with thiolutin, a potent BRISC inhibitor, remarkably alleviated D-GalN/LPS-induced liver injury in mice. By using bone marrow-reconstituted chimeric mice and cell-specific BRISC-deficient mice, we demonstrated that KCs are the key effector cells responsible for protection against D-GalN/LPS-induced liver injury in BRISC-deficient mice. Mechanistically, we found that hepatic and circulating levels of TNF-α, IL-6, MCP-1, and IL-1ß, as well as TNF-α- and MCP-1-producing KCs, in BRISC-deleted mice were dramatically decreased as early as 1 h after D-GalN/LPS challenge, which occurred prior to the elevation of the liver injury markers. Moreover, LPS-induced proinflammatory cytokines production in KCs was significantly diminished by BRISC deficiency in vitro, which was accompanied by potently attenuated NF-κB activation. Restoration of NF-κB activation by two small molecular activators of NF-κB p65 effectively reversed the suppression of cytokines production in ABRO1-deficient KCs by LPS. In conclusion, BRISC is required for optimal activation of NF-κB-mediated proinflammatory cytokines production in LPS-treated KCs and contributes to acute liver injury. This study opens the possibility to develop new strategies for the inhibition of KCs-driven inflammation in liver diseases.

VPS37C facilitates erythroid differentiation by promoting EKLF stability.

The process of erythroid differentiation is orchestrated at the molecular level by a complex network of transcription factors. Erythroid Krüppel-like factor (EKLF/KLF1) is a master erythroid gene regulator that directly regulates most aspects of terminal erythroid differentiation. However, the underlying regulatory mechanisms of EKLF protein stability are still largely unknown. In this study, we identified Vacuolar protein sorting 37 C (VPS37C), a core subunit of the Endosomal sorting complex required for transport-I (ESCRT-I) complex, as an essential regulator of EKLF stability. Our study showed that VPS37C interacts with EKLF and prevents K48-linked polyubiquitination of EKLF and proteasome-mediated EKLF degradation, thus enhancing EKLF protein stability and transcriptional activity. VPS37C overexpression in murine erythroleukemia (MEL) cells promotes hexamethylene bisacetamide (HMBA)-induced erythroid differentiation manifested by up-regulating erythroid-specific EKLF target genes and increasing benzidine-positive cells. In contrast, VPS37C knockdown inhibits HMBA-induced MEL cell erythroid differentiation. Particularly, the restoration of EKLF expression in VPS37C-knockdown MEL cells reverses erythroid-specific gene expression and hemoglobin production. Collectively, our study demonstrated VPS37C is a novel regulator of EKLF ubiquitination and degradation, which plays a positive role in erythroid differentiation of MEL cells by enhancing EKLF protein stability.

Hemgn Protects Hematopoietic Stem and Progenitor Cells Against Transplantation Stress Through Negatively Regulating IFN-γ Signaling.

Hematopoietic stem and progenitor cells (HSPCs) possess the remarkable ability to regenerate the whole blood system in response to ablated stress demands. Delineating the mechanisms that maintain HSPCs during regenerative stresses is increasingly important. Here, it is shown that Hemgn is significantly induced by hematopoietic stresses including irradiation and bone marrow transplantation (BMT). Hemgn deficiency does not disturb steady-state hematopoiesis in young mice. Hemgn-/- HSPCs display defective engraftment activity during BMT with reduced homing and survival and increased apoptosis. Transcriptome profiling analysis reveals that upregulated genes in transplanted Hemgn-/- HSPCs are enriched for gene sets related to interferon gamma (IFN-γ) signaling. Hemgn-/- HSPCs show enhanced responses to IFN-γ treatment and increased aging over time. Blocking IFN-γ signaling in irradiated recipients either pharmacologically or genetically rescues Hemgn-/- HSPCs engraftment defect. Mechanistical studies reveal that Hemgn deficiency sustain nuclear Stat1 tyrosine phosphorylation via suppressing T-cell protein tyrosine phosphatase TC45 activity. Spermidine, a selective activator of TC45, rescues exacerbated phenotype of HSPCs in IFN-γ-treated Hemgn-/- mice. Collectively, these results identify that Hemgn is a critical regulator for successful engraftment and reconstitution of HSPCs in mice through negatively regulating IFN-γ signaling. Targeted Hemgn may be used to improve conditioning regimens and engraftment during HSPCs transplantation.

Pharmacological targeting of NLRP3 deubiquitination for treatment of NLRP3-associated inflammatory diseases.

Pharmacologically inhibiting nucleotide-binding domain and leucine-rich repeat-containing (NLR) family, pyrin domain-containing protein 3 (NLRP3) inflammasome activation results in potent therapeutic effects in a wide variety of preclinical inflammatory disease models. NLRP3 deubiquitination is essential for efficient NLRP3 inflammasome activity, but it remains unclear whether this process can be harnessed for therapeutic benefit. Here, we show that thiolutin (THL), an inhibitor of the JAB1/MPN/Mov34 (JAMM) domain-containing metalloprotease, blocks NLRP3 inflammasome activation by canonical, noncanonical, alternative, and transcription-independent pathways at nanomolar concentrations. In addition, THL potently inhibited the activation of multiple NLRP3 mutants linked with cryopyrin-associated periodic syndromes (CAPS). Treatment with THL alleviated NLRP3-related diseases in mouse models of lipopolysaccharide-induced sepsis, monosodium urate-induced peritonitis, experimental autoimmune encephalomyelitis, CAPS, and methionine-choline-deficient diet-induced nonalcoholic fatty liver disease. Mechanistic studies revealed that THL inhibits the BRCC3-containing isopeptidase complex (BRISC)-mediated NLRP3 deubiquitination and activation. In addition, we show that holomycin, a natural methyl derivative of THL, displays an even higher inhibitory activity against NLRP3 inflammasome than THL. Our study validates that posttranslational modification of NLRP3 can be pharmacologically targeted to prevent or treat NLRP3-associated inflammatory diseases. Future clinical development of derivatives of THL may provide new therapies for NLRP3-related diseases.

Toll-like receptor 5-mediated signaling enhances liver regeneration in mice.

BACKGROUND: Toll-like receptor 5 (TLR5)-mediated pathways play critical roles in regulating the hepatic immune response and show hepatoprotective effects in mouse models of hepatic diseases. However, the role of TLR5 in experimental models of liver regeneration has not been reported. This study aimed to investigate the role of TLR5 in partial hepatectomy (PHx)-induced liver regeneration. METHODS: We performed 2/3 PHx in wild-type (WT) mice, TLR5 knockout mice, or TLR5 agonist CBLB502 treated mice, as a model of liver regeneration. Bacterial flagellin content was measured with ELISA, and hepatic TLR5 expression was determined with quantitative PCR analyses and flow cytometry. To study the effects of TLR5 on hepatocyte proliferation, we analyzed bromodeoxyuridine (BrdU) incorporation and proliferating cell nuclear antigen (PCNA) expression with immunohistochemistry (IHC) staining. The effects of TLR5 during the priming phase of liver regeneration were examined with quantitative PCR analyses of immediate early gene mRNA levels, and with Western blotting analysis of hepatic NF-κB and STAT3 activation. Cytokine and growth factor production after PHx were detected with real-time PCR and cytometric bead array (CBA) assays. Oil Red O staining and hepatic lipid concentrations were analyzed to examine the effect of TLR5 on hepatic lipid accumulation after PHx. RESULTS: The bacterial flagellin content in the serum and liver increased, and the hepatic TLR5 expression was significantly up-regulated in WT mice after PHx. TLR5-deficient mice exhibited diminished numbers of BrdU- and PCNA-positive cells, suppressed immediate early gene expression, and decreased cytokine and growth factor production. Moreover, PHx-induced hepatic NF-κB and STAT3 activation was inhibited in Tlr5-/- mice, as compared with WT mice. Consistently, the administration of CBLB502 significantly promoted PHx-mediated hepatocyte proliferation, which was correlated with enhanced production of proinflammatory cytokines and the recruitment of macrophages and neutrophils in the liver. Furthermore, Tlr5-/- mice displayed significantly lower hepatic lipid concentrations and smaller Oil Red O positive areas than those in control mice after PHx. CONCLUSION: We reveal that TLR5 activation contributes to the initial events of liver regeneration after PHx. Our findings demonstrate that TLR5 signaling positively regulates liver regeneration and suggest the potential of TLR5 agonist to promote liver regeneration.

ABRO1 stabilizes the deubiquitinase BRCC3 through inhibiting its degradation mediated by the E3 ubiquitin ligase WWP2.

BRCA1/BRCA2-containing complex subunit 3 (BRCC3) is a lysine 63-specific deubiquitinase involved in multiple biological processes, such as DNA repair and immune responses. However, the regulation mechanism for BRCC3 protein stability is still unknown. Here, we demonstrate that BRCC3 is mainly degraded through the ubiquitin-proteasome pathway. The HECT-type E3 ubiquitin ligase WWP2 modulates BRCC3 ubiquitination and degradation. ABRO1, a subunit of the BRCC36 isopeptidase complex (BRISC), competes with WWP2 to bind to BRCC3, thereby preventing WWP2-mediated BRCC3 ubiquitination and enhancing BRCC3 stability. Functionally, we show that lentivirus-mediated overexpression of WWP2 in murine macrophages inhibits NLRP3 inflammasome activation by decreasing BRCC3 protein level. This study provides the first insights into the regulation of BRCC3 stability and expands our knowledge about the physiological function of WWP2.

NLRP3 is dispensable for d-galactosamine/lipopolysaccharide-induced acute liver failure.

The nucleotide-binding domain and leucine-rich repeat-containing family pyrin domain containing 3 (NLRP3) inflammasome is involved in various acute and chronic liver diseases, however, it is not clear whether NLRP3 contributes to d-Galactosamine (D-GalN) plus lipopolysaccharide (LPS)-induced acute liver failure (ALF). This study aims to investigate the role of NLRP3 inflammasome in D-GalN/LPS-induced fatal hepatitis. We found that Nlrp3-/- and WT mice showed similar mortality against a lethal dose of D-GalN/LPS treatment. Serum ALT and AST levels, as well as liver necrosis area and hepatocyte apoptosis, were not significantly different between Nlrp3-/- and WT mice at 6 h after D-GalN/LPS injection. Moreover, the numbers of intrahepatic F4/80+ cells and Ly6G+ cells were comparable in two genotype mice following D-GalN/LPS treatment. Besides, Nlrp3-/- mice had reduced IL-1ß levels but similar TNF-α, IL-6, and MCP-1 levels compared with WT mice upon D-GalN/LPS administration. Our findings revealed that NLRP3 ablation does not protect mice from D-GalN/LPS-induced fatal hepatitis and has a marginal effect on intrahepatic inflammatory response upon D-GalN/LPS treatment. This suggests that NLRP3 inflammasome does not appear to be a major contributor to D-GalN/LPS-induced ALF.

GPS2 promotes erythroid differentiation by control of the stability of EKLF protein.

Erythropoiesis is a complex multistage process that involves differentiation of early erythroid progenitors to enucleated mature red blood cells, in which lineage-specific transcription factors play essential roles. Erythroid Krüppel-like factor (EKLF/KLF1) is a pleiotropic erythroid transcription factor that is required for the proper maturation of the erythroid cells, whose expression and activation are tightly controlled in a temporal and differentiation stage-specific manner. Here, we uncover a novel role of G-protein pathway suppressor 2 (GPS2), a subunit of the nuclear receptor corepressor/silencing mediator of retinoic acid and thyroid hormone receptor corepressor complex, in erythrocyte differentiation. Our study demonstrates that knockdown of GPS2 significantly suppresses erythroid differentiation of human CD34+ cells cultured in vitro and xenotransplanted in nonobese diabetic/severe combined immunodeficiency/interleukin-2 receptor γ-chain null mice. Moreover, global deletion of GPS2 in mice causes impaired erythropoiesis in the fetal liver and leads to severe anemia. Flow cytometric analysis and Wright-Giemsa staining show a defective differentiation at late stages of erythropoiesis in Gps2-/- embryos. Mechanistically, GPS2 interacts with EKLF and prevents proteasome-mediated degradation of EKLF, thereby increasing EKLF stability and transcriptional activity. Moreover, we identify the amino acids 191-230 region in EKLF protein, responsible for GPS2 binding, that is highly conserved in mammals and essential for EKLF protein stability. Collectively, our study uncovers a previously unknown role of GPS2 as a posttranslational regulator that enhances the stability of EKLF protein and thereby promotes erythroid differentiation.

EDAG mediates Hsp70 nuclear localization in erythroblasts and rescues dyserythropoiesis in myelodysplastic syndrome.

During human erythroid maturation, Hsp70 translocates into the nucleus and protects GATA-1 from caspase-3 cleavage. Failure of Hsp70 to localize to the nucleus was found in Myelodysplastic syndrome (MDS) erythroblasts and can induce dyserythropoiesis, with arrest of maturation and death of erythroblasts. However, the mechanism of the nuclear trafficking of Hsp70 in erythroblasts remains unknown. Here, we found the hematopoietic transcriptional regulator, EDAG, to be a novel binding partner of Hsp70 that forms a protein complex with Hsp70 and GATA-1 during human normal erythroid differentiation. EDAG overexpression blocked the cytoplasmic translocation of Hsp70 induced by EPO deprivation, inhibited GATA-1 degradation, thereby promoting erythroid maturation in an Hsp70-dependent manner. Furthermore, in myelodysplastic syndrome (MDS) patients with dyserythropoiesis, EDAG is dramatically down-regulated, and forced expression of EDAG has been found to restore the localization of Hsp70 in the nucleus and elevate the protein level of GATA-1 to a significant extent. In addition, EDAG rescued the dyserythropoiesis of MDS patients by increasing erythroid differentiation and decreasing cell apoptosis. This study demonstrates the molecular mechanism of Hsp70 nuclear sustaining during erythroid maturation and establishes that EDAG might be a suitable therapeutic target for dyserythropoiesis in MDS patients.

EDAG promotes the expansion and survival of human CD34+ cells.

EDAG is multifunctional transcriptional regulator primarily expressed in the linloc-kit+Sca-1+ hematopoietic stem cells (HSC) and CD34+ progenitor cells. Previous studies indicate that EDAG is required for maintaining hematopoietic lineage commitment balance. Here using ex vivo culture and HSC transplantation models, we report that EDAG enhances the proliferative potential of human cord blood CD34+ cells, increases survival, prevents cell apoptosis and promotes their repopulating capacity. Moreover, EDAG overexpression induces rapid entry of CD34+ cells into the cell cycle. Gene expression profile analysis indicate that EDAG knockdown leads to down-regulation of various positive cell cycle regulators including cyclin A, B, D, and E. Together these data provides novel insights into EDAG in regulation of expansion and survival of human hematopoietic stem/progenitor cells.

Toll-like receptor 5 signaling restrains T-cell/natural killer T-cell activation and protects against concanavalin A-induced hepatic injury.

Toll-like receptor-5 (TLR5) signaling regulates the immune privileged status of the liver and is involved in hepatic immune disorders. However, the role of TLR5 has not yet been investigated in experimental models of concanavalin A (Con A)-mediated liver injury. Here, we show that TLR5 is highly up-regulated in the hepatic mononuclear cells of mice during Con A-induced hepatitis. Increased mortality and liver histopathology of TLR5-deficient mice correlated with excessive production of proinflammatory cytokines, suggesting that TLR5 knockout mice were more susceptible to Con A-induced hepatitis. We also report that administration of CBLB502, an exogenous TLR5 agonist, substantially alleviated Con A-mediated hepatitis in wild-type mice as shown by increased survival rates, reduced aminotransferase and proinflammatory cytokine production, impaired lymphocyte infiltration, and ameliorated hepatocyte necrosis and/or apoptosis. Mechanistic studies revealed that CBLB502 acts as a negative regulator in limiting T-cell/natural killer T-cell activity and cytokine production in the Con A-hepatitis model. Bone marrow transplantation experiments showed that TLR5 in bone marrow-derived cells contributed to the hepatoprotective efficacy of CBLB502 against Con A-induced liver injury. Moreover, interleukin-6 elevation induced by CBLB502 is an important protective factor against Con A-induced liver injury. In addition, we demonstrate that CBLB502 suppresses α-galactosylceramide-induced natural killer T cell-dependent inflammatory liver injury. CONCLUSION: The TLR5 signaling pathway plays an important role in T cell-mediated hepatic injury and may be exploited for therapeutic treatment of inflammatory liver diseases. (Hepatology 2017;65:2059-2073).

[Construction of Protein Phosphatase 2A Catalytic Subunit ß (PPP2Cß) Overexpression Lentiviral Vector and Its Effect on K562 Erythroid Differentiation].

OBJECTIVE: To construct the ovexpression lentivirus vector of PPP2Cß, the catalytic subunit of protein phosphatase 2A, so as to obtain high-titer packaged lentivirus particles, and to examine the effect of PPP2Cß on the erythroid differentiation Methods: The CDS of PPP2Cß was cloned into the second generation of lentivirus vector FUGW, which should be used to co-transfect HEK 293T cells with the lentiviral expression vector and packaging vectors including pMD2G and pSPAX2. Lentiviruses were harvested at 36 and 48 hours after transfection. Titers of viral stock were determined by using flow cytometric analysis. The Western blot was performed to detect the expression level of PPP2Cß in K562 cells transinfected with the lentiviruses. Benzidine staining and real-time PCR analysis were used to assess the erythroid differentiation of K562 cells. RESULTS: The PPP2Cß overexpressing lentivirus vectors were constructed, the high-titer lentiviral particles were obtained, and then the PPP2Cß overexpression K562 cell line was established and promote erythroid differentiation of K562 cells. CONCLUSION: This study suggests that overexpression PPP2Cß can promote K562 cell erythroid differentiation.

G protein pathway suppressor 2 (GPS2) acts as a tumor suppressor in liposarcoma.

Liposarcoma(LPS) is the most common type of soft tissue sarcoma accounting for 20 % of all adult sarcomas. However, the molecular pathogenesis of this malignancy is still poorly understood. Here, we showed that GPS2 expression was downregulated in LPS and correlated with the prognosis of this disease. In vitro study showed that knockdown of GPS2 resulted in enhanced proliferation and migration of LPS cell line SW872, without significant influence of cell death. Conclusively, our results suggest that GPS2 may act as a tumor suppressor in LPS and serve as a potential prognosis marker for this disease.

EWSR1 regulates mitosis by dynamically influencing microtubule acetylation.

EWSR1, participating in transcription and splicing, has been identified as a translocation partner for various transcription factors, resulting in translocation, which in turn plays crucial roles in tumorigenesis. Recent studies have investigated the role of EWSR1 in mitosis. However, the effect of EWSR1 on mitosis is poorly understood. Here, we observed that depletion of EWSR1 resulted in cell cycle arrest in the mitotic phase, mainly due to an increase in the time from nuclear envelope breakdown to metaphase, resulting in a high percentage of unaligned chromosomes and multipolar spindles. We also demonstrated that EWSR1 is a spindle-associated protein that interacts with α-tubulin during mitosis. EWSR1 depletion increased the cold-sensitivity of spindle microtubules, and decreased the rate of spindle assembly. EWSR1 regulated the level of microtubule acetylation in the mitotic spindle; microtubule acetylation was rescued in EWSR1-depleted mitotic cells following suppression of HDAC6 activity by its specific inhibitor or siRNA treatment. In summary, these results suggest that EWSR1 regulates the acetylation of microtubules in a cell cycle-dependent manner through its dynamic location on spindle MTs, and may be a novel regulator for mitosis progress independent of its translocation.

Two new compounds from Xanthium strumarium.

One new lignan, fructusol A (1), and one new thiazine derivative, 2-hydroxy-xanthiazone (2), along with eight known ones, were isolated from the seeds of Xanthium strumarium. The structures of new compounds were elucidated on the basis of extensive spectroscopic methods. Meanwhile, compounds 1-3 were tested for their antifungal activities against Candida albicans (ATCC 10231) in vitro. No one showed obvious inhibitions (MIC90 > 128 µg/ml).

GIT2 deficiency attenuates concanavalin A-induced hepatitis in mice.

G protein-coupled receptor kinase interactor 2 (GIT2) is a signaling scaffold protein involved in regulation of cytoskeletal dynamics and the internalization of G protein-coupled receptors (GPCRs). The short-splice form of GIT2 is expressed in peripheral T cells and thymocytes. However, the functions of GIT2 in T cells have not yet been determined. We show that treatment with Con A in a model of polyclonal T-lymphocyte activation resulted in marked inhibitions in the intrahepatic infiltration of inflammatory cells, cytokine response and acute liver failure in Git2 (-/-) mice. CD4(+) T cells from Git2 (-/-) mice showed significant impairment in proliferation, cytokine production and signal transduction upon TCR-stimulated activation. Our results suggested that GIT2 plays an important role in T-cell function in vivo and in vitro.

Hepassocin is required for hepatic outgrowth during zebrafish hepatogenesis.

BACKGROUND & AIMS: Hepassocin (HPS) is a hepatotrophic growth factor that specifically stimulates hepatocyte proliferation and promotes liver regeneration after liver damage. In this paper, zebrafish were used to investigate the role of HPS in liver development. METHODS AND RESULTS: During zebrafish development, HPS expression is enriched in liver throughout hepatogenesis. Knockdown of HPS using its specific morpholino leads to a smaller liver phenotype. Further results showed that the HPS knockdown has no effect on the expression of the early endoderm marker gata6 and early hepatic marker hhex. In addition, results showed that the smaller-liver phenotype in HPS morphants was caused by suppression of cell proliferation, not induction of cell apoptosis. CONCLUSIONS: Current findings indicated that HPS is essential to the later stages of development in vertebrate liver organogenesis.

Chain terpenoids isolated from cultures of basidiomycete Phellinus sp.

Two new sesquiterpenoids (phellinuins H and I), together with five known compounds, were isolated from cultures of mushroom Phellinus sp. Their structures were elucidated based on comparison of nuclear magnetic resonance and MS data and those reported in the literature. All of these compounds were tested for cytotoxicity against five cancer cell lines (HL-60, SMMC-721, A-549, MCF-7, and SW-480).

Two new triterpenoids from fruiting bodies of fungus Ganoderma lucidum.

Two new triterpenoids, (24E)-9α,11α-epoxy-3ß-hydroxylanosta-7,24-dien-26-al (1) and (22Z,24Z)-13-hydroxy-3-oxo-14(13 â†’ 12)abeo-lanosta-8,22,24-trien-26,23-olide (2) were isolated from dried fruiting bodies of fungus Ganoderma lucidum. The structures of these two new compounds were elucidated on the basis of extensive spectroscopic analyses. Compound 1 possessed a lanostane skeleton, while compound 2 was based on a rare 14 (13 â†’ 12)abeo-lanostane skeleton with a 26,23-olide moiety. Both of them were evaluated for their antifungal and cytotoxic activities. Neither of them displayed obvious inhibition on Candida albicans and five human cancer cell lines.