Transcription Factors in Prostate Cancer: Insights for Disease Development and Diagnostic and Therapeutic Approaches

Transcription factors (TFs) are proteins essential for the regulation of gene expression, and they regulate the genes involved in different cellular processes, such as proliferation, differentiation, survival, and apoptosis. Although their expression is essential in normal physiological conditions, abnormal regulation of TFs plays critical role in several diseases, including cancer. In prostate cancer, the most common malignancy in men, TFs are known to play crucial roles in the initiation, progression, and resistance to therapy of the disease. Understanding the interplay between these TFs and their downstream targets provides insights into the molecular basis of prostate cancer pathogenesis. In this review, we discuss the involvement of key TFs, including the E26 Transformation-Specific (ETS) Family (ERG and SPDEF), NF-κB, Activating Protein-1 (AP-1), MYC, and androgen receptor (AR), in prostate cancer while focusing on the molecular mechanisms involved in prostate cancer development. We also discuss emerging diagnostic strategies, early detection, and risk stratification using TFs. Furthermore, we explore the development of therapeutic interventions targeting TF pathways, including the use of small molecule inhibitors, gene therapies, and immunotherapies, aimed at disrupting oncogenic TF signaling and improving patient outcomes. Understanding the complex regulation of TFs in prostate cancer provides valuable insights into disease biology, which ultimately may lead to advancing precision approaches for patients.

DCUN1D1 Is an Essential Regulator of Prostate Cancer Proliferation and Tumour Growth That Acts through Neddylation of Cullin 1, 3, 4A and 5 and Deregulation of Wnt/Catenin Pathway

Defective in cullin neddylation 1 domain containing 1 (DCUN1D1) is an E3 ligase for the neddylation, a post-translational process similar to and occurring in parallel to ubiquitin proteasome pathway. Although established as an oncogene in a variety of squamous cell carcinomas, the precise role of DCUN1D1 in prostate cancer (PCa) has not been previously explored thoroughly. Here, we investigated the role of DCUN1D1 in PCa and demonstrated that DCUN1D1 is upregulated in cell lines as well as human tissue samples. Inhibition of DCUN1D1 significantly reduced PCa cell proliferation and migration and remarkably inhibited xenograft formation in mice. Applying both genomics and proteomics approaches, we provide novel information about the DCUN1D1 mechanism of action. We identified CUL3, CUL4B, RBX1, CAND1 and RPS19 proteins as DCUN1D1 binding partners. Our analysis also revealed the dysregulation of genes associated with cellular growth and proliferation, developmental, cell death and cancer pathways and the WNT/β-catenin pathway as potential mechanisms. Inhibition of DCUN1D1 leads to the inactivation of β-catenin through its phosphorylation and degradation which inhibits the downstream action of β-catenin, reducing its interaction with Lef1 in the Lef1/TCF complex that regulates Wnt target gene expression. Together our data point to an essential role of the DCUN1D1 protein in PCa which can be explored for potential targeted therapy.

The Role of the Receptor Tyrosine Kinase Axl in Carcinogenesis and Development of Therapeutic Resistance: An Overview of Molecular Mechanisms and Future Applications

Resistance to chemotherapeutic agents by cancer cells has remained a major obstacle in the successful treatment of various cancers. Numerous factors such as DNA damage repair, cell death inhibition, epithelial-mesenchymal transition, and evasion of apoptosis have all been implicated in the promotion of chemoresistance. The receptor tyrosine kinase Axl, a member of the TAM family (which includes TYRO3 and MER), plays an important role in the regulation of cellular processes such as proliferation, motility, survival, and immunologic response. The overexpression of Axl is reported in several solid and hematological malignancies, including non-small cell lung, prostate, breast, liver and gastric cancers, and acute myeloid leukaemia. The overexpression of Axl is associated with poor prognosis and the development of resistance to therapy. Reports show that Axl overexpression confers drug resistance in lung cancer and advances the emergence of tolerant cells. Axl is, therefore, an important candidate as a prognostic biomarker and target for anticancer therapies. In this review, we discuss the consequence of Axl upregulation in cancers, provide evidence for its role in cancer progression and the development of drug resistance. We will also discuss the therapeutic potential of Axl in the treatment of cancer.

In silico characterization of microRNAs-like sequences in the genome of Paracoccidioides brasiliensis

Eukaryotic cells have different mechanisms of post-transcriptional regulation. Among these mechanisms, microRNAs promote regulation of targets by cleavage or degradation of the mRNA. Fungi of the Paracoccidioides complex are the etiological agents of the main systemic mycosis of Latin America. These fungi present a plasticity to adapt and survive in different conditions, and the presence of microRNAs-like molecules could be part of the mechanisms that provide such plasticity. MicroRNAs produced by the host influence the progression of this mycosis in the lungs besides regulating targets involved in apoptosis in macrophage, activation of T and B cells and the production of cytokines. Therefore, this work analyzed the presence of regions in the genome of this fungus with a potential to encode microRNAs-like molecules. Here we show by analysis of sequence similarity the presence of 18 regions, putatively coding for microRNAs-like molecules in the Paracoccidioides brasiliensis genome. We also described the conservation of dicer and argonaut proteins and the cognate transcripts induced in the yeast parasitic phase. This work represents a starting point for the analysis of the presence of those molecules in the morphological stages of the fungus and their role in fungal development.

Cell Wall Synthesis, Development of Hyphae and Metabolic Pathways Are Processes Potentially Regulated by MicroRNAs Produced Between the Morphological Stages of Paracoccidioides brasiliensis

MicroRNAs are molecules involved in post-transcriptional gene regulation. In pathogenic fungi, microRNAs have been described at different morphological stages by regulating targets involved in processes such as morphogenesis and energy production. Members of the Paracoccidioides complex are the main etiological agents of a systemic mycosis in Latin America. Fungi of the Paracoccidioides complex present a wide range of plasticity to colonize different niches. In response to environmental changes these fungi undergo a morphological switch, remodel their cellular metabolism and modulate structural cell wall components. However, the underlying mechanisms regulating the gene expression is not well understood. By using high performance sequencing and bioinformatics analyses, this work characterizes microRNAs produced by Paracoccidioides brasiliensis. Here, we demonstrated that the transcript encoding proteins involved in microRNA biogenesis were differentially expressed in each morphological stage. In addition, 49 microRNAs were identified in cDNA libraries with 44 differentially regulated among the libraries. Sixteen microRNAs were differentially regulated in comparison to the mycelium in the mycelium-to-yeast transition phase. The yeast parasitic phase revealed a complete remodeling of the expression of these small RNAs. Analyses of targets of the induced microRNAs, from the different libraries, revealed that these molecules may potentially regulate in the cell wall, by repressing genes involved in the synthesis and degradation of glucans and chitin. Furthermore, mRNAs involved in cellular metabolism and development were predicted to be regulated by microRNAs. Therefore, this work describes a putative post transcriptional regulation, mediated by microRNAs in P. brasiliensis and its influence on the adaptive processes of thermal dimorphic fungus.

GADD45α and γ interaction with CDK11p58 regulates SPDEF protein stability and SPDEF-mediated effects on cancer cell migration

The epithelium-specific Ets transcription factor, SPDEF, plays a critical role in metastasis of prostate and breast cancer cells. While enhanced SPDEF expression blocks migration and invasion, knockdown of SPDEF expression enhances migration, invasion, and metastasis of cancer cells. SPDEF expression and activation is tightly regulated in cancer cells; however, the precise mechanism of SPDEF regulation has not been explored in detail. In this study we provide evidence that the cell cycle kinase CDK11p58, a protein involved in G2/M transition and degradation of several transcription factors, directly interacts with and phosphorylates SPDEF on serine residues, leading to subsequent ubiquitination and degradation of SPDEF through the proteasome pathway. As a consequence of CDK11p58 mediated degradation of SPDEF, this loss of SPDEF protein results in increased prostate cancer cell migration and invasion. In contrast, knockdown of CDK11p58 protein expression by interfering RNA or SPDEF overexpression inhibit migration and invasion of cancer cells. We demonstrate that CDK11p58 mediated degradation of SPDEF is attenuated by Growth Arrest and DNA damage-inducible 45 (GADD45) α and, two proteins inducing G2/M cell cycle arrest. We show that GADD45 α and γ, directly interact with CDK11p58 and thereby inhibit CDK11p58 activity, and consequentially SPDEF phosphorylation and degradation, ultimately reducing prostate cancer cell migration and invasion. Our findings provide new mechanistic insights into the complex regulation of SPDEF activity linked to cancer metastasis and characterize a previously unidentified SPDEF/CDK11p58/GADD45α/γ pathway that controls SPDEF protein stability and SPDEF-mediated effects on cancer cell migration and invasion.

Potential role of P2X7R in esophageal squamous cell carcinoma proliferation

Esophageal cancer is an aggressive tumor and is the sixth leading cause of cancer death worldwide. ATP is well known to regulate cancer progression in a variety of models by different mechanisms, including P2X7R activation. This study aimed to evaluate the role of P2X7R in esophageal squamous cell carcinoma (ESCC) proliferation. Our results show that treatment with high ATP concentrations induced a decrease in cell number, cell viability, number of polyclonal colonies, and reduced migration of ESCC. The treatment with the selective P2X7R antagonist A740003 or siRNA for P2X7 reverted this effect in the KYSE450 cell line. In addition, results showed that P2X7R is highly expressed, at mRNA and protein levels, in KYSE450 lineage. Additionally, KYSE450, KYSE30, and OE21 cells express P2X3R, P2X4R, P2X5R, P2X6R, and P2X7R genes. P2X1R is expressed by KYSE30 and KYSE450, and only KYSE450 expresses the P2X2R gene. Furthermore, esophageal cancer cell line KYSE450 presented higher expression of E-NTPDases 1 and 2 and of Ecto-5'-NT/CD73 when compared to normal cells. This cell line also exhibits ATPase, ADPase, and AMPase activity, although in different levels, and the co-treatment of apyrase was able to revert the antiproliferative effects of ATP. Moreover, results showed high immunostaining for P2X7R in biopsies of patients with esophageal carcinoma, indicating the involvement of this receptor in the growth of this type of cancer. The results suggest that P2X7R may be a potential pharmacological target to treat ESCC and can lead us to further investigate the effect of this receptor in cancer cell progression.

Discovery of novel candidate urinary protein biomarkers for prostate cancer in a multiethnic cohort of South African patients via label-free mass spectrometry

PURPOSE

Improvement in diagnostic accuracy of prostate cancer (PCa) progression using MS-based methods to analyze biomarkers in our African, Caucasian, and Mixed Ancestry patients can advance early detection and treatment monitoring.

EXPERIMENTAL DESIGN

MS-based proteomic analysis of pooled (N = 36) and individual samples (N = 45) of PCa, benign prostatic hyperplasia, normal healthy controls, and patients with other uropathies was used to identify differences in proteomics profile. Samples were analyzed for potential biomarkers and proteome coverage in African, Caucasian, and Mixed Ancestry PCa patients.

RESULTS

A total of 1102 and 5595 protein groups and nonredundant peptides, respectively, were identified in the pooling experiments (FDR = 0.01). Twenty potential biomarkers in PCa were identified and fold differences ± 2SD were observed in 17 proteins using intensity-based absolute quantification. Analysis of 45 individual samples yielded 1545 and 9991 protein groups and nonredundant peptides, respectively. Seventy-three (73) proteins groups, including existing putative PCa biomarkers, were found to be potential biomarkers of PCa by label-free quantification and demonstrated ethnic trends within our PCa cohort.

CONCLUSION AND CLINICAL RELEVANCE

Urinary proteomics is a promising route to PCa biomarker discovery and may serve as source of ethnic-related biomarkers of PCa.

Inactivation of GSK3β and activation of NF-κB pathway via Axl represents an important mediator of tumorigenesis in esophageal squamous cell carcinoma

Deregulation of Axl in esophageal squamous cell carcinoma (OSCC) with potential therapeutic implications is described for the first time. This paper also sheds light on the understanding of how Axl regulates OSCC development in vitro and in vivo. Axl expression leads to an Akt-dependent regulation of glycogen synthase kinase 3β activity and the nucluear factor kappaB (NF-κB) pathway, affecting the epithelial–mesenchymal transition.

The receptor tyrosine kinase Axl has been described as an oncogene, and its deregulation has been implicated in the progression of several human cancers. While the role of Axl in esophageal adenocarcinoma has been addressed, there is no information about its role in esophageal squamous cell carcinoma (OSCC). In the current report, we identified, for the first time, deregulation of Axl expression in OSCC. Axl is consistently overexpressed in OSCC cell lines and human tumor samples, mainly in advanced stages of the disease. Blockage of Axl gene expression by small interfering RNA inhibits cell survival, proliferation, migration, and invasion in vitro and esophageal tumor growth in vivo. Additionally, repression of Axl expression results in Akt-dependent inhibition of pivotal genes involved in the nuclear factor-kappaB (NF-κB) pathway and in the induction of glycogen synthase kinase 3β (GSK3β) activity, resulting in loss of mesenchymal markers and induction of epithelial markers. Furthermore, treatment of esophageal cancer cells with the Akt inhibitor wortmannin inhibits NF-κB signaling, induces GSK3β activity, and blocks OSCC cell proliferation in an Axl-dependent manner. Taken together, our results establish a clear role for Axl in OSCC tumorigenesis with potential therapeutic implications.

Aberrant methylation of the MSH3 promoter and distal enhancer in esophageal cancer patients exposed to first-hand tobacco smoke

PURPOSE

Polymorphisms in MSH3 gene confer risk of esophageal cancer when in combination with tobacco smoke exposure. The purpose of this study was to investigate the methylation status of MSH3 gene in esophageal cancer patients in order to further elucidate possible role of MSH3 in esophageal tumorigenesis.

METHODS

We applied nested methylation-specific polymerase chain reaction to investigate the methylation status of the MSH3 promoter in tumors and matching adjacent normal-looking tissues of 84 esophageal cancer patients from a high-risk South African population. The Cancer Genome Atlas data were used to examine DNA methylation profiles at 17 CpG sites located in the MSH3 locus.

RESULTS

Overall, promoter methylation was detected in 91.9 % of tumors, which was significantly higher compared to 76.0 % in adjacent normal-looking esophageal tissues (P = 0.008). When samples were grouped according to different demographics (including age, gender and ethnicity) and smoking status of patients, methylation frequencies were found to be significantly higher in tumor tissues of Black subjects (P = 0.024), patients of 55-65 years of age (P = 0.032), males (P = 0.037) and tobacco smokers (P = 0.015). Furthermore, methylation of the MSH3 promoter was significantly more frequent in tumor samples from smokers compared to tumor samples from non-smokers [odds ratio (OR) = 31.9, P = 0.031]. The TCGA data confirmed significantly higher DNA methylation level at the MSH3 promoter region in tumors (P = 0.0024). In addition, we found evidence of an aberrantly methylated putative MSH3-associated distal enhancer element.

CONCLUSION

Our results suggest that methylation of MSH3 together with exposure to tobacco smoke is involved in esophageal carcinogenesis. Due to the active role of the MSH3 protein in modulating chemosensitivity of cells, methylation of MSH3 should further be examined in association with the outcome of esophageal cancer treatment using anticancer drugs.

Computational repositioning and preclinical validation of pentamidine for renal cell cancer

Although early stages of clear cell renal cell carcinoma (ccRCC) are curable, survival outcome for metastatic ccRCC remains poor. We previously established a highly accurate signature of differentially expressed genes that distinguish ccRCC from normal kidney. The purpose of this study was to apply a new individualized bioinformatics analysis (IBA) strategy to these transcriptome data in conjunction with Gene Set Enrichment Analysis of the Connectivity Map (C-MAP) database to identify and reposition FDA-approved drugs for anticancer therapy. Here, we demonstrate that one of the drugs predicted to revert the RCC gene signature toward normal kidney, pentamidine, is effective against RCC cells in culture and in a RCC xenograft model. ccRCC-specific gene expression signatures of individual patients were used to query the C-MAP software. Eight drugs with negative correlation and P-value <0.05 were analyzed for efficacy against RCC in vitro and in vivo. Our data demonstrate consistency across most patients with ccRCC for the set of high-scoring drugs. Most of the selected high-scoring drugs potently induce apoptosis in RCC cells. Several drugs also demonstrate selectivity for Von Hippel-Lindau negative RCC cells. Most importantly, at least one of these drugs, pentamidine, slows tumor growth in the 786-O human ccRCC xenograft mouse model. Our findings suggest that pentamidine might be a new therapeutic agent to be combined with current standard-of-care regimens for patients with metastatic ccRCC and support our notion that IBA combined with C-MAP analysis enables repurposing of FDA-approved drugs for potential anti-RCC therapy.

The receptor tyrosine kinase Axl in cancer: biological functions and therapeutic implications

The receptor tyrosine kinase Axl has been implicated in the malignancy of different types of cancer. Emerging evidence of Axl upregulation in numerous cancers, as well as reports demonstrating that its inhibition blocks tumor formation in animal models, highlight the importance of Axl as a new potential therapeutic target. Furthermore, recent data demonstrate that Axl plays a pivotal role in resistance to chemotherapeutic regimens. In this review we discuss the functions of Axl and its regulation and role in cancer development, resistance to therapy, and its importance as a potential drug target, focusing on acute myeloid leukemia, breast, prostate and non-small cell lung cancers.

JunD-mediated repression of GADD45α and γ regulates escape from cell death in prostate cancer

The AP-1 transcription factor complex has been implicated in a variety of biological processes including cell differentiation, proliferation, apoptosis and oncogenic transformation. We previously established that activation of the AP-1 family member JunD contributes to deregulated expression of the anti-apoptotic IL-6 gene in prostate cancer cells. We now show that inhibition of JunD in prostate cancer cells results in GADD45α- and γ-dependent induction of cell death and inhibition of tumor growth that is mediated at least partially via c-Jun N-terminal kinase (JNK) and p38 kinase activation. Apoptosis induction by dominant negative JunD and JNK and p38 kinase activation are impeded upon knock down of GADD45α and γ expression by small interfering RNA, most vividly demonstrating the central role of GADD45α and γ in JunD-mediated escape of prostate cancer cells from programmed cell death.

Abstract 3053: Receptor tyrosine kinase AXL as a new target for prostate cancer therapy

Axl is a receptor tyrosine kinase of the family of TAM receptors (which includes TYRO3 and MER) and plays roles in different types of cancer. It is highly expressed in metastatic colon carcinoma, gastric, uterine endometrial and certain types of breast cancer, and sarcoma. As Axl is upregulated in several metastatic cell types it may play a role during invasion and metastasis. Tyrosine kinases (TKs) represent a major class of proto-oncogenes and are involved in tumor growth as well as progression and metastasis of cancer cells. TKs are being actively studied as targets for therapeutic intervention and several of this tyrosine kinase have shown efficacy in clinical trials. Prostate cancer has become the most common solid cancer in older men and is one of the most frequent causes of cancer deaths. Although androgen ablation therapy, surgery and radiation therapy are effective for the treatment of local prostate cancer, there is no effective treatment available for patients with the metastatic androgen-independent disease.

In this work we demonstrated the role of Axl in prostate cancer progression. Using real time PCR to access the level of several tyrosine kinase receptors expression in prostate cancer cell and human tissue, we have identified the tyrosine kinase receptor Axl as a potential target for prostate cancer therapy. Axl has consistent overexpression across prostate cancer cell lines and human prostate tumor tissue providing a model for testing the targeting of Axl. Preliminary data shows a significant increase of Axl expression was found in metastatic PCa cells and clinical samples (48% of adenocarcinomas of prostate when compared with normal prostate tissue). Interestingly, microarray analysis in addition to pathway analysis of PCa cells infected with lentivirus encoding siRNA against Axl revealed that some survival pathways are inhibited, but strikingly all members of the NF-κB pathway are down regulated. Furthermore, the blockage of Axl gene expression strongly inhibits proliferation, migration and invasion of PCa cells. Pilot studies in animal models demonstrate that inhibition of Axl reduces dramatically tumor formation. since our xenograft subcutaneous model in MF5 nude mice demonstrate that blockage of Axl reduces tumor formation by 49.5%.

Taken together these data demonstrated that Axl plays role for migration, invasion and tumor development and can be used as marker for invasive and metastatic tumors. Our data also indicates that Axl can be used as a target for drug therapies since its inhibition leads to induction of apoptosis and blocks cell proliferation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3053. doi:10.1158/1538-7445.AM2011-3053

cdk11p58 regulation of cell cycle progression in cancer development

The Cdk11 protein kinases are members of the cyclin-dependent kinase superfamily. There exist two distinct but closely related human CDK11 genes (p110 and p58). Cdk11p58 is a Ser/Thr kinase involved in cell cycle progression, promoting the centrosome maturation; apoptotic signaling and tumorigenesis.

Using immunoprecipitation and mass spectrometry approaches we demonstrate that GADD45, PDEF and cdk11p58 interact in a complex that might be involved in cell cycle regulation in cancer. GADD45 protein family members (α, β, and γ) are involved in the induction or prevention of apoptosis, cell cycle arrest and participate in the DNA repair machinery. Arrest at the G2/M phase mediated by GADD45 have been identified to rely on its capacity to inhibit the kinase activities such as the CDK1/cyclinB1 complex and the Aurora A, a serine/threonine kinase that play critical roles in the regulation of mitotic events. PDEF (prostate-derived ETS factor) is a transcriptional factor that plays a major role in cancer development and metastasis.

In this study, the kinase activity of cdk11p58 over PDEF as well as the importance of the cdk11p58 binding to the GADD45 family members were evaluated and we demonstate that cdk11p58 phosphorilate PDEF and the phosphorilation process is inhibited by GADD45.

Co-expression of PDEF and cdk11p58 in 293T cells leads to PDEF ubiquitination and degradation, which can be reverted by MG132, a proteasome inhibitor. Corroborating this data, confocal microscope analysis revealed that cdk11p58 co-localized with PDEF and ubiquitin into the nucleus. However, the process is partially blockage by the presence of GADD45 gene, which seems to prevent PDEF degradation mediated by cdk11p58. Deregulation of the ETS factors leads to altered expression of key genes required for cancer progression. PDEF acts as a negative regulator of tumor progression by modulating the expression of growth and migration promoting genes. The degradation of PDEF by cdk11p58 may be a critical step in cancer cell tumorigenesis and more experiments are under way to unravel the importance of this event in cancer cell migration and invasion.

In order to gain further insights about the role of cdk11p58 and GADD45 in cell cycle regulation of cancer cells, we developed DU145 cell lines overexpressing the GADD45α (DU145-GADD45+) and the cdk11p58 (DU145-p58+) proteins. Additionally, DU145 with the cdk11p58 knocked-down (DU145-p58si) was obtained by transduction of lentivirus containing siRNA against the cdk11p58 gene sequence (Sigma).

The biological effect of overexpression or know-down of the cdk11p58 gene in the cell cycle phase was assessed by flow cytometry (FACS) analysis of propidium iodide stained cells. FACS analysis revealed that DU145-p58+ cells progress faster when compared to a control DU145 cell line, while DU145-GADD45+ and DU145-p58si induced cell cycle arrest at the G2/M phase. Furthemore, overexpression of GADD45 in the DU145-p58+ cell line induced an arrest at the G2/M phase, comparable to the control group. Preliminary result of transient transfection of PDEF indicates that ovexpression of PDEF in 293T cells leads to arrest at the G1/S phase.

Transient tranfections of cdk11p58 leads to induction of proliferation when compared with control cells while cells expressing the GADD45 α and PDEF genes demonstrate slower proliferation rates.

In conclusion, PDEF was identified to be a novel target for the kinase activity of cdk11p58. Cdk11p58 induced cell cycle progression and cell proliferation of a prostate cancer cell line that can be inhibited by GADD45 contributing to cell cycle arrest at the G2/M phase.

Induction of neutralizing antibodies in mice immunized with an amino-terminal polypeptide of Streptococcus mutans P1 protein produced by a recombinant Bacillus subtilis strain

The oral pathogen Streptococcus mutans expresses a surface protein, P1, which interacts with the salivary pellicle on the tooth surface or with fluid-phase saliva, resulting in bacterial adhesion or aggregation, respectively. P1 is a target of protective immunity. Its N-terminal region has been associated with adhesion and aggregation functions and contains epitopes recognized by efficacious antibodies. In this study, we used Bacillus subtilis, a gram-positive expression host, to produce a recombinant N-terminal polypeptide of P1 (P1(39-512)) derived from the S. mutans strain UA159. Purified P1(39-512) reacted with an anti-full-length P1 antiserum as well as one raised against intact S. mutans cells, indicating preserved antigenicity. Immunization of mice with soluble and heat-denatured P1(39-512) induced antibodies that reacted specifically with native P1 on the surface of S. mutans cells. The anti-P1(39-512) antiserum was as effective at blocking saliva-mediated aggregation of S. mutans cells and better at blocking bacterial adhesion to saliva-coated plastic surfaces compared with the anti-full-length P1 antiserum. In addition, adsorption of the anti-P1 antiserum with P1(39-512) eliminated its ability to block the adhesion of S. mutans cells to abiotic surfaces. The present results indicate that P1(39-512), expressed and purified from a recombinant B. subtilis strain, maintains important immunological features of the native protein and represents an additional tool for the development of anticaries vaccines.

Antibody responses elicited in mice immunized with Bacillus subtilis vaccine strains expressing Stx2B subunit of enterohaemorragic Escherichia coli O157:H7

No effective vaccine or immunotherapy is presently available for patients with the hemolytic uremic syndrome (HUS) induced by Shiga-like toxin (Stx) produced by enterohaemorragic Escherichia coli (EHEC) strains, such as those belonging to the O157:H7 serotype. In this work we evaluated the performance of Bacillus subtilis strains, a harmless spore former gram-positive bacterium species, as a vaccine vehicle for the expression of Stx2B subunit (Stx2B). A recombinant B. subtilis vaccine strain expressing Stx2B under the control of a stress inducible promoter was delivered to BALB/c mice via oral, nasal or subcutaneous routes using both vegetative cells and spores. Mice immunized with vegetative cells by the oral route developed low but specific anti-Stx2B serum IgG and fecal IgA responses while mice immunized with recombinant spores developed anti-Stx2B responses only after administration via the parenteral route. Nonetheless, serum anti-Stx2B antibodies raised in mice immunized with the recombinant B. subtilis strain did not inhibit the toxic effects of the native toxin, both under in vitro and in vivo conditions, suggesting that either the quantity or the quality of the induced immune response did not support an effective neutralization of Stx2 produced by EHEC strains.

Boosting systemic and secreted antibody responses in mice orally immunized with recombinant Bacillus subtilis strains following parenteral priming with a DNA vaccine encoding the enterotoxigenic Escherichia coli (ETEC) CFA/I fimbriae B subunit

Recombinant Bacillus subtilis strains, either spores or vegetative cells, may be employed as safe and low cost orally delivered live vaccine vehicles. In this study, we report the use of an orally delivered B. subtilis vaccine strain to boost systemic and secreted antibody responses in mice i.m. primed with a DNA vaccine encoding the structural subunit (CfaB) of the CFA/I fimbriae encoded by enterotoxigenic Escherichia coli (ETEC), an important etiological agent of diarrhea among travelers and children living in endemic regions. DBA/2 female mice submitted to the prime-boost immunization regimen developed synergic serum (IgG) and mucosal (IgA) antibody responses to the target CfaB antigen. Moreover, in contrast to mice immunized only with one vaccine formulation, sera harvested from prime-boosted vaccinated individuals inhibited adhesion of ETEC cells to human red blood cells. Additionally, vaccinated dams conferred full passive protection to suckling newborn mice challenged with a virulent ETEC strain. Taken together the present results further demonstrate the potential use of recombinant B. subtilis strains as an alternative live vaccine vehicle.

Evaluation of different promoter sequences and antigen sorting signals on the immunogenicity of Bacillus subtilis vaccine vehicles

Recombinant Bacillus subtilis strains, either in the form of spores or vegetative cells, may be employed as safe and low-cost vaccine vehicles. In this study, we studied the role of promoter sequences and antigen-sorting signals on the immunogenicity based on previously constructed B. subtilis episomal expression systems. Mice orally immunized with spores or cells encoding the B subunit of the heat labile toxin (LTB), originally expressed by some enterotoxigenic Escherichia coli (ETEC) strains, under control of the stress-inducible gsiB promoter developed higher anti-LTB serum IgG and fecal IgA responses with regard to vaccine strains transformed with plasmids encoding the antigen under control of IPTG-inducible (Pspac) or constitutive (PlepA) promoters. Moreover, surface expression of the vaccine antigen under the control of the PgsiB promoter enhanced the immunogenicity of vegetative cells, while intracellular accumulation of LTB led to higher antibody responses in mice orally immunized with recombinant B. subtilis spores. Specific anti-LTB antibodies raised in vaccinated mice recognized and neutralized in vitro the native toxin produced by ETEC strains. Nonetheless, only mice orally immunized with recombinant B. subtilis strains, either as vegetative cells or spores, expressing intracellular LTB under the control of the gsiB promoter conferred partial protection to lethal challenges with purified LT. The present report further demonstrates that B. subtilis plasmid-based heterologous protein expression systems are adequate for antigen delivery via the oral route.

Stable episomal expression system under control of a stress inducible promoter enhances the immunogenicity of Bacillus subtilis as a vector for antigen delivery

Bacillus subtilis has been successfully engineered to express heterologous antigens genetically fused to surface-exposed spore coat proteins as a vaccine vehicle endowed with remarkable heat resistance and probiotic effects for both humans and animals. Nonetheless, the immunogenicity of passenger antigens expressed by B. subtilis spores is low particularly following oral delivery. In this work, we describe a new episomal expression system promoting enhanced immunogenicity of heterologous antigens carried by B. subtilis strains, either in the form of spores or vegetative cells, following oral or parenteral delivery to mice. Based on a bi-directional replicating multicopy plasmid, the gene encoding the B subunit of the heat-labile toxin (LTB), produced by enterotoxigenic Escherichia coli (ETEC) strains, was cloned under the control of the B. subtilis glucose starvation inducible (gsiB) gene promoter, active in vegetative cells submitted to heat and other stress conditions. The recombinant plasmid proved to be structurally and segregationally stable in both cells and spores under in vitro and in vivo conditions. Moreover, BALB/c mice orally immunized with B. subtilis cells or spores elicited enhanced anti-LTB systemic (serum IgG) and secreted (fecal IgA) antibody responses, thus, suggesting that antigen expression occurred during in vivo transit. These results indicate that the new episomal expression system may improve the performance of B. subtilis as a live orally-delivered vaccine carrier.