Recombinant bacillus Calmette-Guérin (BCG) expressing interferon-alpha 2B enhances human mononuclear cell cytotoxicity against bladder cancer cell lines in vitro

BCG therapy in bladder cancer and its tumor microenvironment interactions

SUMMARYBacillus Calmette-Guérin (BCG) has been the standard treatment for non-muscle-invasive bladder cancer for over 30 years. Despite its proven efficacy, challenges persist, including unclear mechanisms of action, resistance in 30%-50% of patients, and significant side effects. This review presents an updated and balanced discussion of the antitumor mechanisms of BCG, focusing on its direct effects on bladder cancer and its interactions with various cell types within the bladder tumor microenvironment. Notably, recent research on the interactions between BCG and the bladder microbiome is also incorporated. We further summarize and analyze the latest preclinical and clinical studies regarding both intrinsic and adaptive resistance to BCG in bladder cancer. Based on the current understanding of BCG's therapeutic principles and resistance mechanisms, we systematically explore strategies to improve BCG-based tumor immunotherapy. These include the development of recombinant BCG, combination therapy with different drugs, optimization of therapeutic regimens and management, and the exploration of new approaches by targeting changes in the bladder microbiota and its metabolites. These measures aim to effectively address the BCG resistance in bladder cancer, reduce its toxicity, and ultimately enhance the clinical anti-tumor efficacy. Bacterial therapy, represented by genetically engineered oncolytic bacteria, has gradually emerged in the field of cancer treatment in recent years. As the only bacterial drug successfully approved for oncology use, BCG has provided decades of clinical experience. By consolidating lessons from BCG's successes and limitations, we hope to provide valuable insights for the development and application of bacterial therapies in cancer treatment.

Mycobacterium bovis BCG reverses deleterious effects of H. pylori components towards gastric barrier cells in vitro

Mycobacterium bovis (M. bovis) Bacillus Calmette-Guerin (BCG) strain used in immunotherapy of bladder cancer (onco-BCG) due to its acid tolerance can be a candidate for prevention or reversion of deleterious effects towards gastric cell barrier initiated by gastric pathogen Helicobacter pylori (Hp) with high resistance to commonly used antibiotics. Colonization of gastric mucosa by Hp promotes oxidative stress, apoptosis resulting in the gastric barrier damage. The aim of this study was to examine the ability of onco-BCG bacilli to control the Hp driven gastric damage using the model of Cavia porcellus primary gastric epithelial cells or fibroblasts in vitro. These cells were treated with Hp surface antigens (glycine acid extract-GE or lipopolysaccharide-LPS) alone or with onco-BCG bacilli and evaluated for cell apoptosis and proliferation in conjunction with the level of soluble lipid peroxidation marker (s4HNE). The cell migration was determined by "wound healing assay", while cytokine response of cells, including interleukin (IL)-33, IL-1β, IL-8 and tumor necrosis factor alpha (TNF-α), by the ELISA. The apoptosis of cells pulsed in vitro with Hp surface components present in GE or with LPS was reduced after exposure of cells to mycobacteria. Similarly, the cell regeneration which was diminished by Hp LPS has been improved in response to mycobacteria. This study reveals that vaccine mycobacteria may reduce gastric barrier damage induced by Hp infection.

Recombinant BCG to Enhance Its Immunomodulatory Activities

The bacillus Calmette-Guérin (BCG) is an attenuated Mycobacterium bovis derivative that has been widely used as a live vaccine against tuberculosis for a century. In addition to its use as a tuberculosis vaccine, BCG has also been found to have utility in the prevention or treatment of unrelated diseases, including cancer. However, the protective and therapeutic efficacy of BCG against tuberculosis and other diseases is not perfect. For three decades, it has been possible to genetically modify BCG in an attempt to improve its efficacy. Various immune-modulatory molecules have been produced in recombinant BCG strains and tested for protection against tuberculosis or treatment of several cancers or inflammatory diseases. These molecules include cytokines, bacterial toxins or toxin fragments, as well as other protein and non-protein immune-modulatory molecules. The deletion of genes responsible for the immune-suppressive properties of BCG has also been explored for their effect on BCG-induced innate and adaptive immune responses. Most studies limited their investigations to the description of T cell immune responses that were modified by the genetic modifications of BCG. Some studies also reported improved protection by recombinant BCG against tuberculosis or enhanced therapeutic efficacy against various cancer forms or allergies. However, so far, these investigations have been limited to mouse models, and the prophylactic or therapeutic potential of recombinant BCG strains has not yet been illustrated in other species, including humans, with the exception of a genetically modified BCG strain that is now in late-stage clinical development as a vaccine against tuberculosis. In this review, we provide an overview of the different molecular engineering strategies adopted over the last three decades in order to enhance the immune-modulatory potential of BCG.

Gmcsf and Ifnα gene therapy improves the response to BCG immunotherapy in a murine model of bladder cancer

Aim: To develop a strategy to improve response to bacillus Calmette-Gueri (BCG) using cytokine gene therapy (Gmcsf + Ifnα). Materials & methods: MB49-PSA tumor-bearing C57BL/6N mice were assigned into four groups: control; Gmcsf + Ifnα therapy; BCG therapy or combined therapy (Gmcsf + Ifnα and BCG). In schedule 1, cytokine gene therapy was delivered before BCG therapy (eight instillations). In schedule 2, cytokine gene and BCG therapy were instilled alternatively (eight instillations). Tumors were analyzed by immunohistochemistry and mRNA analysis and urinary immune cells by flow cytometry. Results: Combined therapy in schedule 2 reduced tumor growth, increased immune cell recruitment and was associated with reduced inflammation when compared with BCG therapy. Conclusion: Alternating cytokine gene delivery with BCG therapy modulates the tumor environment increasing receptivity to BCG.

In vitro Evidence of Human Immune Responsiveness Shows the Improved Potential of a Recombinant BCG Strain for Bladder Cancer Treatment

The live attenuated mycobacterial strain BCG, in use as vaccine against tuberculosis, is considered the gold standard for primary therapy of carcinoma in situ of the bladder. Despite its limitations, to date it has not been surpassed by any other treatment. Our group has developed a recombinant BCG strain expressing the detoxified S1 pertussis toxin (rBCG-S1PT) that proved more effective than wild type BCG (WT-BCG) in increasing survival time in an experimental mouse model of bladder cancer, due to the well-known adjuvant properties of pertussis toxin. Here, we investigated the capacity of rBCG-S1PT to stimulate human immune responses, in comparison to WT-BCG, using an in vitro stimulation assay based on human whole blood cells that allows for a comprehensive evaluation of leukocyte activation. Blood leukocytes stimulated with rBCG-S1PT produced increased levels of IL-6, IL-8, and IL-10 as compared to WT-BCG, but comparable levels of IL-1β, IL-2, IFN-γ, and TNF-α. Stimulation of blood cells with the recombinant BCG strain also enhanced the expression of CD25 and CD69 on human CD4+ T cells. PBMC stimulated with rBCG-S1PT induced higher cytotoxicity to MB49 bladder cancer cells than WT-BCG-stimulated PBMC. These results suggest that the rBCG-S1PT strain is able to activate an immune response in human leukocytes that is higher than that induced by WT-BCG for parameters linked to better prognosis in bladder cancer (regulation of immune and early inflammatory responses), while fully comparable to WT-BCG for classical inflammatory parameters. This establishes rBCG-S1PT as a new highly effective candidate as immunotherapeutic agent against bladder cancer.

A Bivalent Recombinant Mycobacterium bovis BCG Expressing the S1 Subunit of the Pertussis Toxin Induces a Polyfunctional CD4+ T Cell Immune Response

Background

A recombinant BCG strain expressing the genetically detoxified S1 subunit of pertussis toxin 9K/129G (rBCG-S1PT), previously constructed by our research group, demonstrated the ability to develop high protection in mouse models of pertussis challenge which correlated with the induction of a Th1 immune response pattern. The Th1 immune response induced by rBCG-S1PT treatment was also confirmed in the murine orthotopic bladder cancer model, in which the intravesical instillation of rBCG-S1PT resulted in an improved antitumor effect. Based on these observations, we hypothesize that the reengineering of the S1PT expression in BCG could increase the efficiency of the protective Th1 immune response in order to develop a new alternative of immunotherapy in bladder cancer treatment.

Objectives

To construct rBCG strains expressing S1PT from extrachromosomal (rBCG-S1PT) and integrative vectors (rBCG-Sli), or their combination, generating the bivalent strain (rBCG-S1+S1i), and to evaluate the respective immunogenicity of rBCG strains in mice.

Methods

Mycobacterial plasmids were constructed by cloning the s1pt gene under integrative and extrachromosomal vectors and used to transform BCG, individually or in combination. Antigen expression and localization were confirmed by Western blot. Mice were immunized with wild-type BCG or the rBCG strains, and cytokines quantification and flow cytometry analysis were performed in splenocytes culture stimulated with mycobacterial-specific proteins.

Findings

S1PT expression was confirmed in all rBCG strains. The extrachromosomal vector directs S1PT to the cell wall-associated fraction, while the integrative vector directs its expression mainly to the intracellular fraction. Higher levels of IFN-γ were observed in the splenocytes culture from the group immunized with rBCG-S1i in comparison to BCG or rBCG-S1PT. rBCG-S1+S1i showed higher levels of CD4⁺ IFN-γ⁺ and double-positive CD4⁺ IFN-γ⁺ TNF-α⁺ T cells.

Conclusions

rBCG-S1+S1i was able to express the two forms of S1PT and elicited higher induction of polyfunctional CD4⁺ T cells, indicating enhanced immunogenicity and suggesting its use as immunotherapy for bladder cancer.

BCG-induced cytokine release in bladder cancer cells is regulated by Ca2+ signaling

Bacillus Calmette-Guérin (BCG) is widely used in the clinic to effectively treat superficial urinary bladder cancer. However, a significant proportion of patients who fail to respond to BCG risk cystectomy or death. Though more than 3 million cancer treatments with BCG occur annually, surprisingly little is known about the initial signaling cascades activated by BCG. Here, we report that BCG induces a rapid intracellular Ca²⁺ (calcium ion) signal in bladder cancer cells that is essential for activating the transcription factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and for synthesizing and secreting proinflammatory cytokines, including interleukin 8 (IL-8). A similar Ca²⁺ response was observed when cells were exposed to the supernatant of BCG. Studying cellular molecular mechanisms involved in the BCG signaling event, we found pivotal roles for phospholipase C and the Toll-like receptor 4. Further assessment revealed that this signaling pathway induces synthesis of IL-8, whereas exocytosis appeared to be controlled by global Ca²⁺ signaling. These results shed new light on the molecular mechanisms underlying BCG treatment of bladder cancer, which can help in improving therapeutic efficacy and reducing adverse side effects.

Toll-like receptor agonist rMBP-NAP enhances antitumor cytokines production and CTL activity of peripheral blood mononuclear cells from patients with lung cancer

Toll-like receptor (TLR) agonists are known for their ability to inhibit tumor progression via enhancing antitumor cytokines production and cytotoxic T lymphocyte (CTL) activity. Recombinant Helicobacter pylori neutrophil-activating protein fused with maltose-binding protein (rMBP-NAP) has been reported as a novel TLR agonist for antitumor treatment in murine models. The present study aimed to determine the potential and efficacy of the rMBP-NAP for antitumor treatment prior to further clinical trials. The rMBP-NAP was expressed and purified for subsequent experiments. Peripheral blood mononuclear cells (PBMCs) from health donors and patients with lung cancer (LC) were incubated with PBS and 0.2 mg/ml rMBP-NAP. Antitumor cytokines production was assayed using ELISA and reverse transcription-quantitative polymerase chain reaction analysis. The cytolytic activity of PBMCs and the number of Interferon-γ (IFN-γ)-secreting cells were assayed using lactate dehydrogenase and Enzyme-linked ImmunoSpot assays, respectively. The results from the present study revealed that the expression of IFN-γ, interleukin (IL)-2, tumor necrosis factor-α and IL-12 of PBMCs from patients with LC and healthy donors were significantly increased following treatment with rMBP-NAP (P<0.05). Additionally, rMBP-NAP significantly upregulated the number of IFN-γ-secreting cells in PBMCs and prominently increased the cytotoxic activity of PBMCs (P<0.05). Furthermore, the expression of TLR2 was significantly enhanced following rMBP-NAP stimulation (P<0.05), which indicated that rMBP-NAP may serve an antitumor role via TLR2 signaling pathways. Overall, these results demonstrated that rMBP-NAP possesses the potential to be a novel immunomodulatory candidate drug and requires further evaluation in clinical trials.

Nonmuscle invasive bladder cancer: a primer on immunotherapy

Intravesical Bacillus Calmette-Guérin (BCG) has long been the gold standard treatment of nonmuscle invasive bladder cancer. Recently, there has been an emergence of novel immunotherapeutic agents, which have shown promise in the treatment of urothelial cell carcinoma. These agents aim to augment, modify, or enhance the immune response. Such strategies include recombinant BCG, monoclonal antibodies, vaccines, gene therapy, and adoptive T-cell therapy. Here, we review the emerging immunotherapeutics in the treatment of nonmuscle invasive bladder cancer.

Novel immunotherapeutic approaches to the treatment of urothelial carcinoma

Immunotherapy has long played a role in urothelial cancers with the use of bacille Calmette Guérin (BCG) being a mainstay in the treatment of nonmuscle invasive bladder cancer. Novel therapeutic approaches have not significantly impacted mortality in this population and so a renaissance in immunotherapy has resulted. This includes recombinant BCG, oncolytic viruses, monoclonal antibodies, vaccines, and adoptive T-cell therapy. Herein, we provide a review of the current state of the art and future therapies regarding immunotherapeutic strategies for urothelial carcinoma.

Future directions in bladder cancer immunotherapy: towards adaptive immunity

The clinical management of bladder cancer has not changed significantly in several decades. In particular, intravesical bacillus Calmette-Guérin (BCG) immunotherapy has been a mainstay for high-risk nonmuscle invasive bladder cancer since the late 1970s/early 1980s. This is despite the fact that bladder cancer has the highest recurrence rates of any cancer and BCG immunotherapy has not been shown to induce a tumor-specific immune response. We and others have hypothesized that immunotherapies capable of inducing tumor-specific adaptive immunity are needed to impact bladder cancer morbidity and mortality. This article summarizes the preclinical and clinical development of bladder cancer immunotherapies with an emphasis on the last 5 years. Expected progress in the near future is also discussed.

Evolving immunotherapy strategies in urothelial cancer

The treatment of nonmuscle-invasive urothelial carcinoma with bacillus Calmette-Guérin (BCG) represents the importance of immunotherapy in the treatment of cancer. Despite its clinical efficacy, up to 30% of patients will ultimately experience progression to muscle-invasive disease. This, along with an improved understanding of the biologic pathways involved, has led to efforts to improve, enhance, or alter the immune response in the treatment of urothelial carcinoma. A number of novel therapeutic approaches currently are being pursued, including recombinant BCG to induce T helper type 1 (Th1) immune responses, nonlive Mycobacterium agents, targeted agents toward cancer-associated antigens, immune-modulating vaccines, and adoptive T-cell therapies. Here, we review the current and future immunotherapy treatment options for patients with urothelial cancer.

The role of inflammation in bladder cancer

The aim of this book chapter is to present the latest basic research developments on the role of inflammation in bladder cancer and provide insights into their future clinical significance in preventing bladder carcinogenesis and progression. Bladder cancer is a highly immunogenic malignancy. Urothelial cancer cells aim to manipulate the immune system by inhibiting its cytotoxic function while stimulating the secretion of growth promoting factors. Cytokine-induced imbalances in the distribution and differentiation of tumor-infiltrating cytotoxic cells can boost bladder cancer cell proliferation. Tumor-induced release of excessive amount of cytokines causes an "inflammatory storm" which drives metastasis formation via degradation of extracellular matrix proteins. Tumor-related selective cyclooxygenase-2 (COX-2) upregulation suppresses the cell-mediated immune response via aberrant prostaglandin metabolism resulting in failure of differentiation of myeloid cell progenitors into mature antigen-presenting cells. T cells are capable of increasing the oxidative stress on bladder cancer cells via induction of COX-2 and STEAP expression. Some evidence also suggests that COX-2 activation may be also involved in inflammation-mediated cancer stem cell proliferation. Antibodies against the VEGF-co-receptor neuropilin decrease the angiogenetic potential of bladder cancer cells. Inflammation-based predictive bladder cancer models have demonstrated to accurately predict response to treatment both in the curative and palliative setting. While randomized trials do not support a clinical benefit for the use of anti-inflammatory drugs (i.e., celecoxib, atorvastatin) in preventing recurrence of low-grade bladder cancer, further investigations are warranted in the setting of high-grade tumors since the immune response to cancer stimuli is most probably more pronounced in advanced stages.

Recombinant bacillus Calmette-Guérin in urothelial bladder cancer immunotherapy: current strategies

Bacillus Calmette-Guérin (BCG) has been used in the intravesical treatment of urothelial bladder cancer (UBC) for three decades. Despite its efficacy, intravesical BCG therapy is associated with some limitations such as side effects and BCG failure, which have inspired multiple ways to improve it. Recent advances have focused on recombinant BCG (rBCG) which provides a novel tactic for modification of BCG. To date, a number of rBCG strains have been developed and demonstrated to encourage efficacy and safety in preclinical and clinical studies. This review summarizes current rBCG strategies, concerns and future directions in UBC immunotherapy with an intention to encourage further research and eventually to inform clinical decisions.

Construction of a recombinant-BCG containing the LMP2A and BZLF1 genes and its significance in the Epstein-Barr virus positive gastric carcinoma

The signal peptide Ag85B of Bacillus Chalmette-Guerin (BCG) was used to construct a recombinant plasmid of BCG. The BCG-Ag85B gene and fused EBV LMP2A and BZLF1 genes were amplified and successively inserted into the Escherichia coli-BCG shuttle-vector pMV261. The recombinant plasmids were then amplified in E. coli DH5α and transformed into competent BCG. The expression of BZLF1 and LMP2A fusion proteins in recombinant-BCG (rBCG) was shown by Western blot. After the injection of recombinant-BCG into mice, antibodies against the fusion protein BZLF1 and LMP2A were measured by ELISA, and the cellular immune effects were determined by the lactate dehydrogenate (LDH) release assays. The results confirmed that the cloned genes of BCG-Ag85B and Z2A were correctly inserted into the vector pMV261. The recombinant plasmid pMVZ2A expressed Z2A in BCG effectively after transformation. The rBCG proteins were recognized by the BZLF1 (LMP2A) antibody. An ELISA demonstrated that rBCG could stimulate the generation of antibody against the fusion protein. The fusion gene was constructed successfully, and the rBCG induced humoral and cellular immune response in mice.

The mechanism of action of BCG therapy for bladder cancer--a current perspective

Bacillus Calmette-Guérin (BCG) has been used to treat non-muscle-invasive bladder cancer for more than 30 years. It is one of the most successful biotherapies for cancer in use. Despite long clinical experience with BCG, the mechanism of its therapeutic effect is still under investigation. Available evidence suggests that urothelial cells (including bladder cancer cells themselves) and cells of the immune system both have crucial roles in the therapeutic antitumour effect of BCG. The possible involvement of bladder cancer cells includes attachment and internalization of BCG, secretion of cytokines and chemokines, and presentation of BCG and/or cancer cell antigens to cells of the immune system. Immune system cell subsets that have potential roles in BCG therapy include CD4(+) and CD8(+) lymphocytes, natural killer cells, granulocytes, macrophages, and dendritic cells. Bladder cancer cells are killed through direct cytotoxicity by these cells, by secretion of soluble factors such as TRAIL (tumour necrosis factor-related apoptosis-inducing ligand), and, to some degree, by the direct action of BCG. Several gaps still exist in our knowledge that should be addressed in future efforts to understand this biotherapy of cancer.

The mannose-sensitive hemagglutination pilus strain of Pseudomonas aeruginosa shift peritoneal milky spot macrophages towards an M1 phenotype to dampen peritoneal dissemination

Peritoneal dissemination (PD) of tumor cells is the most frequent pattern of gastric cancer recurrence and the leading cause of death. Peritoneal milky spots are deemed as the site of origin of gastric cancer PD wherein the main cellular components are macrophages. A vaccine derived from the mannose-sensitive hemagglutination pilus strain of Pseudomonas aeruginosa (PA-MSHA) has exhibit strong immune modulatory properties. In the present study, we tested the hypothesis whether the PA-MSHA vaccine activated peritoneal milky spot macrophages (PMSM) in a manner that would attenuate PD. It was observed that PA-MSHA activated PMSM towards a classical activation phenotype via a toll-like receptor4/9-dependent mechanism, which increased interleukin-12 levels and promoted the expression of co-stimulatory and antigen-presenting molecules like CD80, CD86, and MHC-II (P < 0.05). In addition, PA-MSHA-treated PMSM exhibited strong nonspecific antitumor effects in both contact-dependent and contact-independent modes of action (P < 0.05). In mice treated with PA-MSHA before inoculating gastric cancer cells, we noted alleviated PD toward the untreated mice. In conclusion, our findings demonstrated that PA-MSHA can stimulate PMSM towards an M1 phenotype and that activated PMSM inhibit gastric cancer growth and PD both in vitro and in vivo. The results of the current study provide a mechanistic insight that is relevant to the potential application of PA-MSHA in the treatment of gastric cancer-mediated PD.

Killed but metabolically active Mycobacterium bovis bacillus Calmette-Guérin retains the antitumor ability of live bacillus Calmette-Guérin

PURPOSE

Mycobacterium bovis bacillus Calmette-Guérin is the most effective treatment for high risk noninvasive bladder cancer. Although bacillus Calmette-Guérin immunotherapy clearly decreases recurrence and progression rates, side effects are common and infection with the bacillus has been described. For these reasons it is necessary to find safer alternatives to the live bacillus. We explored the possibility of using killed but metabolically active bacillus Calmette-Guérin.

MATERIALS AND METHODS

T24, J82 and RT4 bladder tumor cell lines were cultured with live and irradiation or heat treated bacillus Calmette-Guérin Connaught. We measured the inhibition of cell proliferation and the production of cytokines in cell culture supernatants. Peripheral mononuclear blood cells were also infected and the production of different cytokines in cell culture supernatants was analyzed. Peripheral blood mononuclear cell and cell culture supernatants activated by mycobacteria were then cultured with T24 cells to analyze whether they showed cytotoxic activity.

RESULTS

Compared to the other bacillus Calmette-Guérin treatments, γ irradiated bacillus Calmette-Guérin showed activity similar to that of the live bacillus for inhibiting tumor growth and inducing cytokine production. Irradiated bacillus Calmette-Guérin showed metabolic activity and, thus, was considered killed but metabolically active. This is the treatment that most accurately preserved the mycobacterial structure. Killed but metabolically active bacillus Calmette-Guérin induced cytokine production by infected peripheral mononuclear blood cells. Mycobacteria activated peripheral blood mononuclear cell and cell supernatants showed cytotoxic activity against tumor cells, retaining the antitumor capacity of the live bacillus.

CONCLUSIONS

Our results suggest that killed but metabolically active bacillus Calmette-Guérin could be considered a safer immunotherapy alternative to treatment with the live bacillus.

From infection to immunotherapy: host immune responses to bacteria at the bladder mucosa

The pathogenesis of urinary tract infection and mechanisms of the protective effect of Bacillus Calmette-Guerin (BCG) therapy for bladder cancer highlight the importance of studying the bladder as a unique mucosal surface. Innate responses to bacteria are reviewed, and although our collective knowledge remains incomplete, we discuss how adaptive immunity may be generated following bacterial challenge in the bladder microenvironment. Interestingly, the widely held belief that the bladder is sterile has been challenged recently, indicating the need for further study of the impact of commensal microorganisms on the immune response to uropathogen infection or intentional instillation of BCG. This review addresses the aspects of bladder biology that have been well explored and defines what still must be discovered about the immunobiology of this understudied organ.

Antitumor effects of human interferon-alpha 2b secreted by recombinant bacillus Calmette-Guérin vaccine on bladder cancer cells

OBJECTIVE

Our objective was to construct a recombinant bacillus Calmette-Guérin vaccine (rBCG) that secretes human interferon-alpha 2b (IFNα-2b) and to study its immunogenicity and in vitro antitumor activity against human bladder cancer cell lines T24 and T5637.

METHODS

The signal sequence BCG Ag85B and the gene IFNα-2b were amplified from the genome of BCG and human peripheral blood, respectively, by polymerase chain reaction (PCR). The two genes were cloned in Escherichia coli-BCG shuttle-vector pMV261 to obtain a new recombinant plasmid pMV261-Ag85B-IFNα-2b. BCG was transformed with the recombinant plasmid by electroporation and designated rBCG-IFNα-2b. Mononuclear cells were isolated from human peripheral blood (PBMCs) and stimulated with rBCG-IFNα-2b or wild type BCG for 3 d, and then cultured with human bladder cancer cell lines T24 and T5637. Their cytotoxicities were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.

RESULTS

BCG was successfully transformed with the recombinant plasmid pMV261-Ag85B-IFNα-2b by electroporation and the recombinant BCG (rBCG-IFNα-2b) was capable of synthesizing and secreting cytokine IFNα-2b. PBMC proliferation was enhanced significantly by rBCG-IFNα-2b, and the cytotoxicity of PBMCs stimulated by rBCG-IFNα-2b to T24 and T5627 was significantly stronger in comparison to wild type BCG.

CONCLUSIONS

A recombinant BCG, secreting human IFNα-2b (rBCG-IFNα-2b), was constructed successfully and was superior to control wild type BCG in inducing immune responses and enhancing cytotoxicity to human bladder cancer cell lines T24 and T5637. This suggests that rBCG-IFNα-2b could be a promising agent for bladder cancer patients in terms of possible reductions in both clinical dosage and side effects of BCG immunotherapy.

Bladder Cancer Immunotherapy: BCG and Beyond

Mycobacterium bovis bacillus Calmette-Guérin (BCG) has become the predominant conservative treatment for nonmuscle invasive bladder cancer. Its mechanism of action continues to be defined but has been shown to involve a T helper type 1 (Th1) immunomodulatory response. While BCG treatment is the current standard of care, a significant proportion of patients fails or do not tolerate treatment. Therefore, many efforts have been made to identify other intravesical and immunomodulating therapeutics to use alone or in conjunction with BCG. This paper reviews the progress of basic science and clinical experience with several immunotherapeutic agents including IFN-α, IL-2, IL-12, and IL-10.

Th1 cytokine-secreting recombinant Mycobacterium bovis bacillus Calmette-Guérin and prospective use in immunotherapy of bladder cancer

Intravesical instillation of Mycobacterium bovis bacillus Calmette-Guérin (BCG) has been used for treating bladder cancer for 3 decades. However, BCG therapy is ineffective in approximately 30–40% of cases. Since evidence supports the T helper type 1 (Th1) response to be essential in BCG-induced tumor destruction, studies have focused on enhancing BCG induction of Th1 immune responses. Although BCG in combination with Th1 cytokines (e.g., interferon-α) has demonstrated improved efficacy, combination therapy requires multiple applications and a large quantity of cytokines. On the other hand, genetic manipulation of BCG to secrete Th1 cytokines continues to be pursued with considerable interest. To date, a number of recombinant BCG (rBCG) strains capable of secreting functional Th1 cytokines have been developed and demonstrated to be superior to BCG. This paper discusses current rBCG research, concerns, and future directions with an intention to inspire the development of this very promising immunotherapeutic modality for bladder cancer.

Immunotherapy for urothelial carcinoma: current status and perspectives

Intravesical instillation of bacillus Calmette Guérin (BCG) for the treatment of urothelial carcinoma (UC) of the bladder is based on the BCG-induced immune response, which eradicates and prevents bladder cancer. The results of recent studies have suggested that not only major histocompatibility complex (MHC)-nonrestricted immune cells such as natural killer cells, macrophages, neutrophils, etc., but also MHC-restricted CD8⁺ T cells play an important role and are one of the main effectors in this therapy. Better understanding of the mechanism of BCG immunotherapy supports the idea that active immunotherapy through its augmented T cell response can have great potential for the treatment of advanced UC. In this review, progress in immunotherapy for UC is discussed based on data from basic, translational and clinical studies. We also review the escape mechanism of cancer cells from the immune system, and down-regulation of MHC class I molecules.

Intravesical therapy for urothelial carcinoma of the urinary bladder: a critical review

The management of non-muscle-invasive urothelial carcinoma of the bladder (UCB) is a challenge for physicians and patients alike. This is largely due to the heterogeneous natural history of this disease, in which tumors range from indolent to rapidly progressive and eventually fatal. Moreover, the high rate of recurrence and progression cause significant morbidity, expense, and detriment to quality of life. The advent of effective and safe intravesical therapies has improved the management of non-muscle-invasive UCB. Nevertheless, despite over 30 years of research and clinical experience, the mechanism, risks, benefits, and optimal regimens and treatment algorithms remain unclear. Although immunotherapy with bacillus Calmette-Guerin (BCG) has been the mainstay of intravesical treatment and represents a significant advance in the interaction of immunology and oncology, its clinical effectiveness is accompanied by a wide range of adverse events. Here, we review the literature on intravesical immunotherapy and chemotherapy with the aim of evaluating the clinical utility of the different treatments and providing recommendations. Many studies over the years have compared efficacy and toxicities of different agents and regimens, and certain conclusions are now well supported by high-level evidence. Future perspectives and promising advances in drug development are discussed and areas of improvement are identified in order to promote better cancer control and decrease the rate and severity of side-effects.

MUC1-based recombinant Bacillus Calmette-Guerin vaccines as candidates for breast cancer immunotherapy

IMPORTANCE OF THE FIELD

The challenge in breast cancer vaccine development is to find the best combination of antigen, adjuvant and delivery system to produce a strong and long-lasting immune response. Mucin 1 (MUC1) is a potential candidate target for breast cancer immunotherapy. Bacillus Calmette-Guerin (BCG) is used widely in human vaccines. Furthermore, it can potentially offer unique advantages for developing a safe and effective multi-vaccine vehicle. Due to these properties, the development of MUC1 based recombinant BCG (rBCG) vaccines for breast cancer immunotherapy has gained great momentum in recent years.

AREAS COVERED IN THIS REVIEW

Our aim is to discuss the recent progress in MUC1-based breast cancer immunotherapy and to highlight the advantages of MUC1-based rBCG vaccines as the new breast cancer vaccines.

WHAT THE READER WILL GAIN

Several promising MUC1-based rBCG vaccines have been shown to induce MUC1-specific antitumor immune responses in pre-clinical studies. This review updates and evaluates this very important and rapidly developing field, and provides a critical perspective and information source for its potential clinical applications.

TAKE HOME MESSAGE

MUC1-based rBCG vaccines have been shown to elicit an effective anti-tumor immune response in vivo demonstrating its potential utility in breast cancer treatment.

Mycobacterium bovis bacillus Calmette-Guérin-induced macrophage cytotoxicity against bladder cancer cells

Many details of the molecular and cellular mechanisms involved in Mycobacterium bovis bacillus Calmette-Guérin (BCG) immunotherapy of bladder cancer have been discovered in the past decades. However, information on a potential role for macrophage cytotoxicity as an effector mechanism is limited. Macrophages play pivotal roles in the host innate immunity and serve as a first line of defense in mycobacterial infection. In addition to their function as professional antigen-presenting cells, the tumoricidal activity of macrophages has also been studied with considerable interest. Studies have shown that activated macrophages are potent in killing malignant cells of various tissue origins. This review summarizes the current understanding of the BCG-induced macrophage cytotoxicity toward bladder cancer cells with an intention to inspire investigation on this important but underdeveloped research field.

Loss of heterozygosis on IFN-alpha locus is a prognostic indicator of bacillus Calmette-Guerin response for nonmuscle invasive bladder cancer

PURPOSE

We evaluated the role of loss of heterozygosity on the interferon-alpha locus to predict the response to bacillus Calmette-Guerin therapy in patients with nonmuscle invasive bladder cancer.

MATERIALS AND METHODS

A total of 117 consecutive patients were selected, including 77 with nonmuscle invasive bladder cancer and 40 controls. Loss of heterozygosity on the interferon-alpha locus (chromosome 9p21) was assessed in blood and urine samples before transurethral resection. All patients underwent transurethral resection and then 6 weekly bacillus Calmette-Guerin instillations. Those with nonmuscle invasive bladder cancer were assigned to groups 1 and 2 with and without loss of heterozygosity on the interferon-alpha locus, respectively.

RESULTS

Of the 77 patients with nonmuscle invasive bladder cancer 39 (50.6%) had loss of heterozygosity on the interferon-alpha locus (group 1) and 38 (49.4%) had no alteration (group 2). Only 1 of 40 controls showed loss of heterozygosity on the interferon-alpha locus. At the end of followup 13 patients in group 1 and 27 in group 2 were alive without recurrence. We noted a significant difference between loss of heterozygosity on interferon-alpha and followup status (dF 01, LR 11.252, p = 0.003). Kaplan-Meier analysis revealed a significant difference in recurrence probability (response to bacillus Calmette-Guerin) and loss of heterozygosity on interferon-alpha (p <0.0001). On multivariate analysis loss of heterozygosity (HR 4.09, 95% CI 2.59-6.28, p = 0.002), grade (grade 3 HR 3.31, 95% CI 1.38-3.35, p = 0.03) and the number of lesions (3 or greater HR 2.31, 95% CI 1.38-3.25, p = 0.03) were independent predictors of the bacillus Calmette-Guerin response.

CONCLUSIONS

This study highlights the predictive value of loss of heterozygosity analysis on interferon-alpha in patients with nonmuscle invasive bladder cancer treated with bacillus Calmette-Guerin.

Interleukin-10 inhibits Mycobacterium bovis bacillus Calmette-Guérin (BCG)-induced macrophage cytotoxicity against bladder cancer cells

The mechanisms underlying bacillus Calmette-Guérin (BCG) immunotherapy of bladder cancer currently remain elusive. Previously, we demonstrated that macrophages were cytotoxic to bladder cancer cells upon BCG stimulation in vitro. However, macrophages from C57BL/6 mice were less potent than those from C3H/HeN mice for the killing of bladder cancer cells. This study was to determine whether interleukin (IL)-10 produced by macrophages in response to BCG is a causative factor for the reduced cytotoxicity in BCG-stimulated C57BL/6 macrophages. Thioglycollate-elicited peritoneal macrophages were prepared and analysed for the BCG induction of cytotoxicity, cytokines and nitric oxide (NO) in vitro. Compared to BCG-stimulated C3H/HeN macrophages, BCG-stimulated C57BL/6 macrophages exhibited reduced killing of bladder cancer MBT-2 cells and MB49 cells. Studies demonstrated further that BCG-stimulated C57BL/6 macrophages produced a high level of IL-10, which correlated with reduced production of tumour necrosis factor (TNF)-alpha, IL-6 and NO. Neutralizing endogenous IL-10 during BCG stimulation increased C57BL/6 macrophage cytotoxicity against MB49 cells by 3.2-fold, along with increased production of TNF-alpha by 6.4-fold and NO by 3.6-fold, respectively. Macrophages from C57BL/6 IL-10(-/-) mice also exhibited increased killing of MB49 cells and production of TNF-alpha and NO upon BCG stimulation. In addition, supplementation of exogenous recombinant IL-10 reduced BCG-induced C3H/HeN macrophage cytotoxicity against both MBT-2 cells and MB49 cells in a dose-dependent manner. These results reveal the inhibitory role of IL-10 in BCG-induced macrophage cytotoxicity, suggesting that blockage of IL-10 may potentially enhance the effect of BCG in the treatment of bladder cancer patients.

Recombinant Mycobacterium bovis BCG

The Bacillus Calmette-Guerin (BCG) is an attenuated strain of Mycobacterium bovis that has been broadly used as a vaccine against human tuberculosis. This live bacterial vaccine is able to establish a persistent infection and induces both cellular and humoral immune responses. The development of mycobacterial genetic systems to express foreign antigens and the adjuvanticity of BCG are the basis of the potential use of this attenuated mycobacterium as a recombinant vaccine. Over the years, a range of strategies has been developed to allow controlled and stable expression of viral, bacterial and parasite antigens in BCG. Herein, we review the strategies developed to express heterologous antigens in BCG and the immune response elicited by recombinant BCG constructs. In addition, the use of recombinant BCG as an immunomodulator and future perspectives of BCG as a recombinant vaccine vector are discussed.