Evans blue-mediated white-light detection of non-muscle-invasive bladder cancer: A preclinical feasibility and safety study using a rat bladder urothelial cell carcinoma model

Photodynamic diagnosis (PDD) improves the detection of non-muscle-invasive bladder cancer (NMIBC). However, white-light (WL) cystoscopy remains the technique routinely used in urological clinics. A more cost-effective but equally performant alternative to PDD may encompass the use of an intense tumoritropic dye in combination with WL cystoscopy. Using a preclinical setting, we investigated the practical aspects of the use of Evans blue (EB) dye for the possible future detection of NMIBC using WL cystoscopy. A solution of 1 and 5 mM EB was instilled into healthy and AY-27 tumor-bearing rat bladders. The bladders were then rapidly dissected and the inner walls were inspected for EB using WL stereomicroscopy. EB present in the bladders and the plasma was also quantified using high performance liquid chromatography. To assess the effects of repeated instillations on normal rat bladders, EB was instilled for 7 consecutive days, after which time the bladder wall was investigated histologically. To gain insight into the mechanisms underlying the selective accumulation of EB in malignant urothelium, RNA sequencing of urothelial tissue and subsequent comparative analysis were performed, with a specific focus on cell adhesion. The concentrations of EB were substantially higher in malignant bladders compared with those in healthy bladders, matching the blue staining of the inner bladder wall observed by stereomicroscopy. EB was equally present in the plasma of healthy and tumor-bearing subjects, although at low concentrations. Importantly, EB did not cause any abnormalities in the urothelium after 7 days of repeated instillation in normal rats. RNA sequencing of the urothelium indicated an abnormal expression of several genes related to cell adhesion in malignant urothelium compared with the normal urothelium. Our findings may be important for future clinical developments in the field of diagnostics for bladder cancer. Implementing the more cost-effective protocol of EB instillations in combination with WL cystoscopy may offer a benefit to patients as well as the healthcare system.

Resistance to anticancer vaccination effect is controlled by a cancer cell-autonomous phenotype that disrupts immunogenic phagocytic removal

Immunogenic cell death (ICD) is a well-established instigator of ‘anti-cancer vaccination-effect (AVE)’. ICD has shown considerable preclinical promise, yet there remain subset of cancer patients that fail to respond to clinically-applied ICD inducers. Non-responsiveness to ICD inducers could be explained by the existence of cancer cell-autonomous, anti-AVE resistance mechanisms. However such resistance mechanisms remain poorly investigated. In this study, we have characterized for the first time, a naturally-occurring preclinical cancer model (AY27) that exhibits intrinsic anti-AVE resistance despite treatment with ICD inducers like mitoxantrone or hypericin-photodynamic therapy. Further mechanistic analysis revealed that this anti-AVE resistance was associated with a defect in exposing the important ‘eat me’ danger signal, surface-calreticulin (ecto-CRT/CALR). In an ICD setting, this defective ecto-CRT further correlated with severely reduced phagocytic clearance of AY27 cells as well as the failure of these cells to activate AVE. Defective ecto-CRT in response to ICD induction was a result of low endogenous CRT protein levels (i.e. CRT^low-phenotype) in AY27 cells. Exogenous reconstitution of ecto-rCRT (recombinant-CRT) improved the phagocytic removal of ICD inducer-treated AY27 cells, and importantly, significantly increased their AVE-activating ability. Moreover, we found that a subset of cancer patients of various cancer-types indeed possessed CALR^low or CRT^low-tumours. Remarkably, we found that tumoural CALR^high-phenotype was predictive of positive clinical responses to therapy with ICD inducers (radiotherapy and paclitaxel) in lung and ovarian cancer patients, respectively. Furthermore, only in the ICD clinical setting, tumoural CALR levels positively correlated with the levels of various phagocytosis-associated genes relevant for phagosome maturation or processing. Thus, we reveal the existence of a cancer cell-autonomous, anti-AVE or anti-ICD resistance mechanism that has profound clinical implications for anticancer immunotherapy and cancer predictive biomarker analysis.

Biodistribution of Evans blue in an orthotopic AY-27 rat bladder urothelial cell carcinoma model: implication for the improved diagnosis of non-muscle-invasive bladder cancer (NMIBC) using dye-guided white-light cystoscopy

OBJECTIVES

To investigate the possibility of using Evans blue (EB) as a novel diagnostic tool to detect bladder tumours with white-light (WL) cystoscopy, in this preclinical study we examine the biodistribution of EB in the different layers (urothelium, submucosa, muscle) of a normal rat bladder and a rat bladder bearing a malignant urothelium composed of syngeneic AY-27 tumour cells.

MATERIALS AND METHODS

EB was instilled into both normal as well as tumour-bearing rat bladders. After instillation, bladders were removed and snap frozen in liquid nitrogen. The distribution of EB in the different layers was quantified using fluorescence microscopy. To gain more insight into the mechanism underlying the selective accumulation of EB in tumour tissue, bladder sections were prepared for ultrastructural investigations by means of transmission electron microscopy (TEM). In addition, we also examined the expression of E-cadherin, claudin-1 and desmoglein-1 by immunohistochemistry to study the integrity of the bladder wall, as these molecules are key constituents of adherens junctions, tight junctions and desmosomes, respectively.

RESULTS

In most cases, the accumulation of EB in malignant bladders was substantially higher than in healthy bladders, at least when 1 mm EB instillations were used. In case of a 1 mm EB instillation for 2 h, the EB-associated fluorescence in malignant urothelial tissue was 55-times higher than the fluorescence found in normal urothelium. Ultrastructurally, malignant tissue displayed wider intercellular spaces and a decreased number of cell junction components compared with normal tissue, pointing to defects in the urothelial barrier. There were no differences in the expression of E-cadherin, whereas desmoglein-1 staining was stronger in the membranes of healthy bladder urothelium compared with tumour tissue. Claudin-1 expression was negative in all samples tested.

CONCLUSION

EB is selectively taken up by tumour tissue after intravesical instillations in rats bearing bladder tumours. The lower expression of desmoglein-1 in tumour samples, together with the reduced presence of desmosomes seen with TEM, likely imply that desmosomes play an important role in the ultrastructural differences between healthy rat urothelium and tumour tissue, and secondary to that, to the differential uptake of EB in both tissues. We consider that our findings could be useful for future clinical developments in the field of diagnostics for bladder cancer.

Sequential inactivation of Rho GTPases and Lim kinase by Pseudomonas aeruginosa toxins ExoS and ExoT leads to endothelial monolayer breakdown

Pseudomonas aeruginosa is a major human opportunistic pathogen and one of the most important causal agents of bacteremia. For non-blood-borne infection, bacterial dissemination requires the crossing of the vascular endothelium, the main barrier between blood and the surrounding tissues. Here, we investigated the effects of P. aeruginosa type 3 secretion effectors, namely ExoS, ExoT, and ExoY, on regulators of actin cytoskeleton dynamics in primary endothelial cells. ExoS and ExoT similarly affected the Lim kinase-cofilin pathway, thereby promoting actin filament severing. Cofilin activation was also observed in a mouse model of P. aeruginosa-induced acute pneumonia. Rho, Rac, and Cdc42 GTPases were sequentially inactivated, leading to inhibition of membrane ruffling, filopodia, and stress fiber collapse, and focal adhesion disruption. At the end of the process, ExoS and ExoT produced a dramatic retraction in all primary endothelial cell types tested and thus a rupture of the endothelial monolayer. ExoY alone had no effect in this context. Cell retraction could be counteracted by overexpression of actin cytoskeleton regulators. In addition, our data suggest that moesin is neither a direct exotoxin target nor an important player in this process. We conclude that any action leading to inhibition of actin filament breakdown will improve the barrier function of the endothelium during P. aeruginosa infection.

Transcriptional regulation of the uptake [NiFe]hydrogenase genes in Rhodobacter capsulatus

Transcription of the hupSL genes, which encode the uptake [NiFe]hydrogenase of Rhodobacter capsulatus, is specifically activated by H(2). Three proteins are involved, namely the H(2)-sensor HupUV, the histidine kinase HupT and the transcriptional activator HupR. hupT and hupUV mutants have the same phenotype, i.e. an increased level of hupSL expression (assayed by phupS::lacZ fusion) in the absence of H(2); they negatively control hupSL gene expression. HupT can autophosphorylate its conserved His(217), and in vitro phosphotransfer to Asp(54) of its cognate response regulator, HupR, was demonstrated. The non-phosphorylated form of HupR binds to an enhancer site (5'-TTG-N(5)-CAA) of phupS localized at -162/-152 nt and requires integration host factor to activate fully hupSL transcription. HupUV is an O(2)-insensitive [NiFe]hydrogenase, which interacts with HupT to regulate the phosphorylation state of HupT in response to H(2) availability. The N-terminal domain of HupT, encompassing the PAS domain, is required for interaction with HupUV. This interaction with HupT, leading to the formation of a (HupT)(2)-(HupUV)(2) complex, is weakened in the presence of H(2), but incubation of HupUV with H(2) has no effect on the stability of the heterodimer/tetramer, HupUV-(HupUV)(2), equilibrium. HupSL biosynthesis is also under the control of the global two-component regulatory system RegB/RegA, which controls gene expression in response to redox. RegA binds to a site close to the -35 promoter recognition site and to a site overlapping the integration host factor DNA-binding site (5'-TCACACACCATTG, centred at -87 nt) and acts as a repressor.

Oxidant-dependent phosphorylation of p40phox in B lymphocytes

As with the neutrophil NADPH oxidase, the B lymphocyte NADPH oxidase consists of a membrane-bound flavocytochrome b and regulatory factors including Rac and the cytosolic phox protein triad p67phox, p47phox, and p40phox. Here we demonstrate by phosphoamino acid analysis and the use of the potent PKC inhibitor GFX that, in response to stimulation of B lymphocytes with sodium orthovanadate and H(2)O(2), the p40phox component of the cytosolic phox triad is selectively phosphorylated on serine and threonine residues by a PKC-type protein kinase. The pattern of p40phox phosphorylation was closely related to the kinetics of tyrosine phosphorylation of PKC-delta, the main PKC isotype of B lymphocytes. Blocking H(2)O(2)-dependent tyrosine phosphorylation of PKC by genistein resulted in inhibition of p40phox phosphorylation. The correlation between the tyrosine phosphorylation of PKC-delta and the serine/threonine phosphorylation of p40phox, together with the inhibition of p40phox phosphorylation by rottlerin, a selective inhibitor of PKC-delta, makes the activated PKC-delta a likely candidate in the process of the oxidant-dependent phosphorylation of p40phox in B cells.

The RegB/RegA two-component regulatory system controls synthesis of photosynthesis and respiratory electron transfer components in Rhodobacter capsulatus

Recently, we demonstrated that the RegB/RegA two-component regulatory system from Rhodobacter capsulatus functions as a global regulator of metabolic processes that either generate or consume reducing equivalents. For example, the RegB/RegA system controls expression of such energy generating processes as photosynthesis and hydrogen utilization. In addition, RegB/RegA also control nitrogen and carbon fixation pathways that utilize reducing equivalents. Here, we use a combination of DNase I protection and plasmid-based reporter expression studies to demonstrate that RegA directly controls synthesis of cytochrome cbb3 and ubiquinol oxidases that function as terminal electron acceptors in a branched respiratory chain. We also demonstrate that RegA controls expression of cytochromes c2, c(y) and the cytochrome bc1 complex that are involved in both photosynthetic and respiratory electron transfer events. These data provide evidence that the RegB/RegA two-component system has a major role in controlling the synthesis of numerous processes that affect reducing equivalents in Rhodobacter capsulatus.

Expression of uptake hydrogenase and molybdenum nitrogenase in Rhodobacter capsulatus is coregulated by the RegB-RegA two-component regulatory system

Purple photosynthetic bacteria are capable of generating cellular energy from several sources, including photosynthesis, respiration, and H(2) oxidation. Under nutrient-limiting conditions, cellular energy can be used to assimilate carbon and nitrogen. This study provides the first evidence of a molecular link for the coregulation of nitrogenase and hydrogenase biosynthesis in an anoxygenic photosynthetic bacterium. We demonstrated that molybdenum nitrogenase biosynthesis is under the control of the RegB-RegA two-component regulatory system in Rhodobacter capsulatus. Footprint analyses and in vivo transcription studies showed that RegA indirectly activates nitrogenase synthesis by binding to and activating the expression of nifA2, which encodes one of the two functional copies of the nif-specific transcriptional activator, NifA. Expression of nifA2 but not nifA1 is reduced in the reg mutants up to eightfold under derepressing conditions and is also reduced under repressing conditions. Thus, although NtrC is absolutely required for nifA2 expression, RegA acts as a coactivator of nifA2. We also demonstrated that in reg mutants, [NiFe]hydrogenase synthesis and activity are increased up to sixfold. RegA binds to the promoter of the hydrogenase gene operon and therefore directly represses its expression. Thus, the RegB-RegA system controls such diverse processes as energy-generating photosynthesis and H(2) oxidation, as well as the energy-demanding processes of N(2) fixation and CO(2) assimilation.

Mechanisms for redox control of gene expression

This review discusses various mechanisms that regulatory proteins use to control gene expression in response to alterations in redox. The transcription factor SoxR contains stable [2Fe-2S] centers that promote transcription activation when oxidized. FNR contains [4Fe-4S] centers that disassemble under oxidizing conditions, which affects DNA-binding activity. FixL is a histidine sensor kinase that utilizes heme as a cofactor to bind oxygen, which affects its autophosphorylation activity. NifL is a flavoprotein that contains FAD as a redox responsive cofactor. Under oxidizing conditions, NifL binds and inactivates NifA, the transcriptional activator of the nitrogen fixation genes. OxyR is a transcription factor that responds to redox by breaking or forming disulfide bonds that affect its DNA-binding activity. The ability of the histidine sensor kinase ArcB to promote phosphorylation of the response regulator ArcA is affected by multiple factors such as anaerobic metabolites and the redox state of the membrane. The global regulator of anaerobic gene expression in alpha-purple proteobacteria, RegB, appears to directly monitor respiratory activity of cytochrome oxidase. The aerobic repressor of photopigment synthesis, CrtJ, seems to contain a redox responsive cysteine. Finally, oxygen-sensitive rhizobial NifA proteins presumably bind a metal cofactor that senses redox. The functional variability of these regulatory proteins demonstrates that prokaryotes apply many different mechanisms to sense and respond to alterations in redox.

Aerobic repression of the Rhodobacter capsulatus bchC promoter involves cooperative interactions between CrtJ bound to neighboring palindromes

Previous studies demonstrated that bacteriochlorophyll, carotenoid, and light harvesting gene expression in Rhodobacter capsulatus is repressed under aerobic growth conditions by the repressor CrtJ. Isolated CrtJ is known to bind to the palindrome TGTN12ACA, which is present in two copies in the bchC promoter, one of which spans the -35 and the other the -10 sigma-70 recognition sequences. In this study, we demonstrate that CrtJ binds to the two palindromic sites in the bchC promoter in a cooperative manner. The level of cooperativity of CrtJ binding to the -35 palindrome was shown to be 26-fold. A distance of 8 base pairs between the two palindromic sites was shown to be critical for cooperative binding, as evidenced by the disruption of binding that resulted when +6 and +11 base pairs were inserted between the palindromes.

CrtJ bound to distant binding sites interacts cooperatively to aerobically repress photopigment biosynthesis and light harvesting II gene expression in Rhodobacter capsulatus

Expression of light harvesting II genes and of bacteriochlorophyll and carotenoid biosynthesis genes in Rhodobacter capsulatus is repressed under aerobic growth conditions by the transcription factor CrtJ. In this study, we demonstrate that the crtA-crtI intergenic region contains divergent promoters that initiate transcription 116 base pairs apart, based on primer extension analyses. DNase I protection assays demonstrate that purified CrtJ binds to one palindrome that overlaps the crtA -10 promoter recognition sequence as well as to a second palindrome that overlaps the -35 crtI promoter recognition sequence. Similar analyses also show that the puc promoter region contains two distant CrtJ palindromes, with one near the -35 promoter recognition sequence and the other located 240 base pairs upstream. Gel mobility shift and filter retention assays indicate that CrtJ binds in a cooperative manner to these distantly separated palindromes. In vivo expression assays with puc and crtI promoter reporter plasmids further demonstrate that aerobic repression of puc and crtI expression requires both CrtJ palindromes. These in vitro and in vivo results indicate that aerobic repression of puc, crtA, and crtI expression involves cooperative interactions between CrtJ bound to distant palindromes. A DNA looping model is discussed.

Rhodobacter capsulatus HypF is involved in regulation of hydrogenase synthesis through the HupUV proteins

The photosynthetic bacterium Rhodobacter capsulatus contains a membrane-bound [NiFe]hydrogenase encoded by the hupSL genes. We show in this study that hypF mutants are devoid of hydrogenase activity and lack the HupL protein. We also observed that, in contrast to the wild-type strain B10, transcription of the hupSL genes was not stimulated by H2 in the hypF mutants RS13 and BSE19. Complementation of the hypF mutants with the plasmid borne hypF gene restored hydrogenase activity to wild-type levels and inducibility by H2. The R. capsulatus hupU and hupV gene products share significant similarities with the small (HupS) and the large (HupL) hydrogenase subunits, respectively. Active HupUV proteins can catalyze the hydrogen-deuterium exchange reaction. In whole cells, this H-D exchange is distinguishable from the H-D exchange catalyzed by the membrane-bound HupSL proteins by its insensitivity to O2 and to acetylene. By measuring the formation of H2 and HD in exchange with D2 uptake, we demonstrated that the hypF mutants have no active HupUV nor HupSL proteins. H-D exchange activity, of both HupUV and HupSL, was restored by hypF gene complementation. These data indicate that the HypF protein participates not only in the maturation of HupSL, but also in the maturation of the HupUV proteins and that the latter are involved in the cellular response to H2.

The Rhodobacter capsulatus hupSLC promoter: identification of cis-regulatory elements and of trans-activating factors involved in H2 activation of hupSLC transcription

The [NiFe]hydrogenase of the photosynthetic bacterium Rhodobacter capsulatus is encoded by the structural hupSLC operon, the expression of which is induced by H2. H2 activation was no longer observable in chromosomal hupR mutants, an indication that HupR is implicated directly in the activation by H2 of hupS gene expression. The transcriptional start site of the hupS promoter, determined by primer extension mapping, was located 55 nucleotides upstream from the translational start codon of the hupS gene. Regulatory sequences were identified by serial 5' deletions of the 300bp hupS promoter-regulatory region (phupS) and phupS-lacZ translational fusions. Cis-regulatory sequences capable of interacting with two transcription factors, IHF and HupR, a response regulator of the NtrC subfamily, were studied by electrophoretic mobility shift assays (EMSAs). The R. capsulatus IHF and HupR proteins were overexpressed in Escherichia coli and purified by affinity chromatography. IHF binds to a site, 5'-TCACACACCATTG, centred at -87 nt from the transcription start site. The HupR protein binds to one site within the -162 to -152 nt region, which contains the palindromic sequence 5'-TTG-R5-CAA. By the use of 5' deletions and site-directed mutagenesis of the -162/-152 region, this palindrome was shown to be required for in vivo hupS transcriptional activation by H2.

Purification and in vitro phosphorylation of HupT, a regulatory protein controlling hydrogenase gene expression in Rhodobacter capsulatus

The HupT protein of Rhodobacter capsulatus, involved in negative regulation of hydrogenase gene expression, is predicted to be a histidine kinase on the basis of sequence comparisons. The protein was overproduced in Escherichia coli, purified to homogeneity, and demonstrated to autophosphorylate in vitro in the presence of [gamma-32P]ATP. An H217N hupt mutant was constructed, and the mutant protein was shown to have lost kinase activity. This result, and the fact that the phosphoryl group in phosphorylated HupT appeared to be bound to an N atom, support the suggestion from sequence comparisons that HupT is a histidine kinase, which can autophosphorylate on the His217 residue.

HupUV proteins of Rhodobacter capsulatus can bind H2: evidence from the H-D exchange reaction

The H-D exchange reaction has been measured with the D2-H2O system, for Rhodobacter capsulatus JP91, which lacks the hupSL-encoded hydrogenase, and R. capsulatus BSE16, which lacks the HupUV proteins. The hupUV gene products, expressed from plasmid pAC206, are shown to catalyze an H-D exchange reaction distinguishable from the H-D exchange due to the membrane-bound, hupSL-encoded hydrogenase. In the presence of O2, the uptake hydrogenase of BSE16 cells catalyzed a rapid uptake and oxidation of H2, D2, and HD present in the system, and its activity (H-D exchange, H2 evolution in presence of reduced methyl viologen [MV+]) depended on the external pH, while the H-D exchange due to HupUV remained insensitive to external pH and O2. These data suggest that the HupSL dimer is periplasmically oriented, while the HupUV proteins are in the cytoplasmic compartment.

The hupTUV operon is involved in negative control of hydrogenase synthesis in Rhodobacter capsulatus

The hupT, hupU, and hupV genes, which are located upstream from the hupSLC and hypF genes in the chromosome of Rhodobacter capsulatus, form the hupTUV operon expressed from the hupT promoter. The hupU and hupV genes, previously thought to belong to a single open reading frame, encode HupU, of 34.5 kDa (332 amino acids), and HupV, of 50.4 kDa (476 amino acids), which are >/= 50% identical to the homologous Bradyrhizobium japonicum HupU and HupV proteins and Rhodobacter sphaeroides HupU1 and HupU2 proteins, respectively; they also have 20 and 29% similarity with the small subunit (HupS) and the large subunit (HupL), respectively, of R. capsulatus [NiFe]hydrogenase. HupU lacks the signal peptide of HupS and HupV lacks the C-terminal sequence of HupL, which are cleaved during hydrogenase processing. Inactivation of hupV by insertional mutagenesis or of hupUV by in-frame deletion led to HupV- and Hup(UV)- mutants derepressed for hydrogenase synthesis, particularly in the presence of oxygen. These mutants were complemented in trans by plasmid-borne hupTUV but not by hupT or by hupUV, except when expressed from the inducible fru promoter. Complementation of the HupV- and Hup(UV)- mutants brought about a decrease in hydrogenase activity up to 10-fold, to the level of the wild-type strain B10, indicating that HupU and HupV participate in negative regulation of hydrogenase expression in concert with HupT, a sensor histidine kinase involved in the repression process. Plasmid-borne gene fusions used to monitor hupTUV expression indicated that the operon is expressed at a low level (50- to 100-fold lower than hupS).

Sequence analysis and interposon mutagenesis of the hupT gene, which encodes a sensor protein involved in repression of hydrogenase synthesis in Rhodobacter capsulatus

The hupT gene, which represses hydrogenase gene expression in the purple photosynthetic bacterium Rhodobacter capsulatus, has been identified and sequenced. The nucleotide sequence of hupT and of the contiguous downstream open reading frame, hupU, is reported. The HupT protein of 456 amino acids (48,414 Da) has sequence similarity with the FixL, DctB, NtrB, and ArcB proteins and is predicted to be a soluble sensor kinase. Insertional inactivation of the hupT gene led to deregulation of transcriptional control, so that the hydrogenase structural operon hupSLC became overexpressed in cells grown anaerobically or aerobically. The HupT- mutants were complemented in trans by a plasmid containing an intact copy of the hupT gene. The hupU open reading frame, capable of encoding a protein of 84,879 Da, shared identity with [NiFe]hydrogenase subunits; the strongest similarity was observed with the periplasmic hydrogenase of Desulfovibrio baculatus.