A possible mechanism of intravesical BCG therapy for human bladder carcinoma: involvement of innate effector cells for the inhibition of tumor growth

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.

Review of BCG immunotherapy for bladder cancer

SUMMARYFor several decades, intravesical Bacillus Calmette-Guérin (iBCG) immunotherapy has been the gold standard adjuvant treatment for high-risk and selected intermediate-risk patients with non-muscle-invasive bladder cancer (NMIBC). In this review, the mechanisms of iBCG immune-mediated anti-cancer activity and resistance are presented. Furthermore, a literature review of short-term and systemic iBCG-related side effects was performed. A high incidence (75.5%) of iBCG-related short-term, self-limiting adverse events was observed, while more severe iBCG-related local/systemic complications (iBCG-rL/SCs) that required medical treatment or hospitalization occurred at a lower rate (2.35%). Disseminated was the most common form of iBCG-rSCs, while two-thirds of the cases were classified as infectious. The implementation of molecular-based techniques resulted in significantly higher diagnostic rates. Anti-tuberculous treatment (ATT) is the mainstay of treatment, while in patients with any iBCG-rL/SC form involving the vasculature, ATT should be combined with surgery. Local and osteoarticular forms have the lowest mortality, but their management necessitates severe and debilitating surgical procedures. The overall iBCG-attributed mortality in patients with iBCG-rL/SC was 7.4%, with disseminated, vascular, and lung involvements exhibiting the highest rates. Given the global shortage of BCG for the last two decades, as well as the paucity of effective options for iBCG-refractory or relapsing NMIBC patients, new therapeutic strategies are being tested with promising early results.

Macrophages directly kill bladder cancer cells through TNF signaling as an early response to BCG therapy

The Bacillus Calmette-Guérin (BCG) vaccine is the oldest cancer immunotherapeutic agent in use. Despite its effectiveness, its initial mechanisms of action remain largely unknown. Here, we elucidate the earliest cellular mechanisms involved in BCG-induced tumor clearance. We developed a fast preclinical in vivo assay to visualize in real time and at single-cell resolution the initial interactions among bladder cancer cells, BCG and innate immunity using the zebrafish xenograft model. We show that BCG induced the recruitment and polarization of macrophages towards a pro-inflammatory phenotype, accompanied by induction of the inflammatory cytokines tnfa, il1b and il6 in the tumor microenvironment. Macrophages directly induced apoptosis of human cancer cells through zebrafish TNF signaling. Macrophages were crucial for this response as their depletion completely abrogated the BCG-induced phenotype. Contrary to the general concept that macrophage anti-tumoral activities mostly rely on stimulating an effective adaptive response, we demonstrate that macrophages alone can induce tumor apoptosis and clearance. Thus, our results revealed an additional step to the BCG-induced tumor immunity model, while providing proof-of-concept experiments demonstrating the potential of this unique model to test innate immunomodulators.

Breaking Barriers: Modulation of Tumor Microenvironment to Enhance Bacillus Calmette-Guérin Immunotherapy of Bladder Cancer

The clinical management of bladder cancer continues to present significant challenges. Bacillus Calmette-Guérin (BCG) immunotherapy remains the gold standard of treatment for non-muscle invasive bladder cancer (NMIBC), but many patients develop recurrence and progression to muscle-invasive disease (MIBC), which is resistant to BCG. This review focuses on the immune mechanisms mobilized by BCG in bladder cancer tumor microenvironments (TME), mechanisms of BCG resistance, the dual role of the BCG-triggered NFkB/TNFα/PGE2 axis in the regulation of anti-tumor and tumor-promoting aspects of inflammation, and emerging strategies to modulate their balance. A better understanding of BCG resistance will help develop new treatments and predictive biomarkers, paving the way for improved clinical outcomes in bladder cancer patients.

Emerging applications of cancer bacteriotherapy towards treatment of pancreatic cancer

Pancreatic cancer is a highly aggressive form of cancer with a five-year survival rate of only ten percent. Pancreatic ductal adenocarcinoma (PDAC) accounts for ninety percent of those cases. PDAC is associated with a dense stroma that confers resistance to current treatment modalities. Increasing resistance to cancer treatments poses a challenge and a need for alternative therapies. Bacterial mediated cancer therapies were proposed in the late 1800s by Dr. William Coley when he injected osteosarcoma patients with live streptococci or a fabrication of heat-killed Streptococcus pyogenes and Serratia marcescens known as Coley's toxin. Since then, several bacteria have gained recognition for possible roles in potentiating treatment response, enhancing anti-tumor immunity, and alleviating adverse effects to standard treatment options. This review highlights key bacterial mechanisms and structures that promote anti-tumor immunity, challenges and risks associated with bacterial mediated cancer therapies, and applications and opportunities for use in PDAC management.

BCG in Bladder Cancer Immunotherapy

BCG is a live attenuated strain of Mycobacterium bovis that is primarily used as a vaccine against tuberculosis. In the past four decades, BCG has also been used for the treatment of non-muscle invasive bladder cancer (NMIBC). In patients with NMIBC, BCG reduces the risk of tumor recurrence and decreases the likelihood of progression to more invasive disease. Despite the long-term clinical experience with BCG, its mechanism of action is still being elucidated. Data from animal models and from human studies suggests that BCG activates both the innate and adaptive arms of the immune system eventually leading to tumor destruction. Herein, we review the current data regarding the mechanism of BCG and summarize the evidence for its clinical efficacy and recommended indications and clinical practice.

BCG invokes superior STING-mediated innate immune response over radiotherapy in a carcinogen murine model of urothelial cancer

Radiation and bacillus Calmette-Guérin (BCG) instillations are used clinically for treatment of urothelial carcinoma, but the precise mechanisms by which they activate an immune response remain elusive. The role of the cGAS-STING pathway has been implicated in both BCG and radiation-induced immune response; however, comparison of STING pathway molecules and the immune landscape following treatment in urothelial carcinoma has not been performed. We therefore comprehensively analyzed the local immune response in the bladder tumor microenvironment following radiotherapy and BCG instillations in a well-established spontaneous murine model of urothelial carcinoma to provide insight into activation of STING-mediated immune response. Mice were exposed to the oral carcinogen, BBN, for 12 weeks prior to treatment with a single 15 Gy dose of radiation or three intravesical instillations of BCG (1 × 108  CFU). At sacrifice, tumors were staged by a urologic pathologist and effects of therapy on the immune microenvironment were measured using the NanoString Myeloid Innate Immunity Panel and immunohistochemistry. Clinical relevance was established by measuring immune biomarker expression of cGAS and STING on a human tissue microarray consisting of BCG-treated non-muscle-invasive urothelial carcinomas. BCG instillations in the murine model elevated STING and downstream STING-induced interferon and pro-inflammatory molecules, intratumoral M1 macrophage and T-cell accumulation, and complete tumor eradication. In contrast, radiotherapy caused no changes in STING pathway or innate immune gene expression; rather, it induced M2 macrophage accumulation and elevated FoxP3 expression characteristic of immunosuppression. In human non-muscle-invasive bladder cancer, STING protein expression was elevated at baseline in patients who responded to BCG therapy and increased further after BCG therapy. Overall, these results show that STING pathway activation plays a key role in effective BCG-induced immune response and strongly indicate that the effects of BCG on the bladder cancer immune microenvironment are more beneficial than those induced by radiation. © 2021 The Pathological Society of Great Britain and Ireland.

Tumor-Associated Mast Cells in Urothelial Bladder Cancer: Optimizing Immuno-Oncology

Urothelial bladder cancer (UBC) is one of the most prevalent and aggressive malignancies. Recent evidence indicates that the tumor microenvironment (TME), including a variety of immune cells, is a critical modulator of tumor initiation, progression, evolution, and treatment resistance. Mast cells (MCs) in UBC are possibly involved in tumor angiogenesis, tissue remodeling, and immunomodulation. Moreover, tumor-infiltration by MCs has been reported in early-stage UBC patients. This infiltration is linked with a favorable or unfavorable prognosis depending on the tumor type and location. Despite the discrepancy of MC function in tumor progression, MCs can modify the TME to regulate the immunity and infiltration of tumors by producing an array of mediators. Nonetheless, the precise role of MCs in UBC tumor progression and evolution remains unknown. Thus, this review discusses some critical roles of MCs in UBC. Patients with UBC are treated at both early and late stages by immunotherapeutic methods, including intravenous bacillus Calmette–Guérin instillation and immune checkpoint blockade. An understanding of the patient response and resistance mechanisms in UBC is required to unlock the complete potential of immunotherapy. Since MCs are pivotal to understand the underlying processes and predictors of therapeutic responses in UBC, our review also focuses on possible immunotherapeutic treatments that involve MCs.

Non-Muscular Invasive Bladder Cancer: Re-envisioning Therapeutic Journey from Traditional to Regenerative Interventions

Non-muscular invasive bladder cancer (NMIBC) is one of the most common cancer and major cause of economical and health burden in developed countries. Progression of NMIBC has been characterized as low-grade (Ta) and high grade (carcinoma in situ and T1). The current surgical intervention for NMIBC includes transurethral resection of bladder tumor; however, its recurrence still remains a challenge. The BCG-based immunotherapy is much effective against low-grade NMIBC. BCG increases the influx of T cells at bladder cancer site and inhibits proliferation of bladder cancer cells. The chemotherapy is another traditional approach to address NMIBC by supplementing BCG. Notwithstanding, these current therapeutic measures possess limited efficacy in controlling NMIBC, and do not provide comprehensive long-term relief. Hence, biomaterials and scaffolds seem an effective medium to deliver therapeutic agents for restructuring bladder post-treatment. The regenerative therapies such as stem cells and PRP have also been explored for possible solution to NMIBC. Based on above-mentioned approaches, we have comprehensively analyzed therapeutic journey from traditional to regenerative interventions for the treatment of NMIBC.

Innate immune memory is associated with increased disease-free survival in bladder cancer patients treated with bacillus Calmette-Guérin

INTRODUCTION

While studies suggest that innate immune memory acquired by circulating monocytes may mediate the benefit of bacillus Calmette-Guérin (BCG) in the treatment of patients with high-risk non-muscle-invasive bladder cancer (NMIBC), prospective studies are lacking. Innate immune memory is defined by enhanced release of pro-inflammatory cytokines by innate immune cells following a secondary challenge with pattern recognition receptor (PRR) ligands.

METHODS

Peripheral blood monocytes isolated from 33 patients with intermediate- or high-risk NMIBC before and after two or five induction BCG instillations were stimulated with the PRR ligand lipopolysaccharide (LPS). Inflammatory cytokine levels in the culture medium were measured. Extent of innate immune memory acquisition was determined by dividing the levels of cytokines released after BCG instillation by the levels released prior to BCG therapy.

RESULTS

Monocytes secreted variable levels of TNFα, IL-1β, IL-6, IFNγ, IL-12, and IL-10. Compared with patients with recurrences, the post-BCG:pre-BCG ratio of IL-12 in monocyte cultures from patients without recurrences after five BCG instillations was significantly increased. Patients with no innate immune memory (based on IL-12 ratios) had significantly shorter time to recurrence than patients with innate immune memory (p<0.001). Eighty-four percent (16/19) of patients with innate immune memory vs. only 22% (2/9) of patients without memory had disease-free survival of over 500 days.

CONCLUSIONS

Results demonstrate a potential link between BCG-induced innate immune memory peripherally and local anti-tumor responses. Further validation will increase our understanding of the mode of action of BCG and, therefore, will be used to enhance its effectiveness.

Bacillus Calmette-Guerin (BCG): Its fight against pathogens and cancer

Bacillus Calmette-Guerin (BCG) is the only FDA approved first line therapy for patients with nonmuscle invasive bladder cancer. Since the turn of the 20th century BCG has been used as a vaccine for protection against Mycobacterium tuberculosis (Mtb) and has also been found to have protection against nontuberculosis related pathogens. Recently the role of "trained immunity" has been identified as a possible mechanism for BCG vaccine-mediated immunity to Mtb. Similarly, BCG has been used as an immunotherapy for bladder cancer for more than 40 years, and the underlying mechanisms for BCG-mediated anti-tumor activity is poorly characterized. Several studies have shown that multiple immune pathways contribute to the immune response, and efficacy of intravesicle BCG as a cancer therapy. It is vital that we integrate our understanding of BCG as a vaccine and as a cancer therapeutic to facilitate design of future studies in order to maximize the immunotherapeutic potential of BCG. In this review we will outline the role of BCG as a vaccine, the known immune pathways that are activated by intravesical BCG and outline a potential clinical study integrating BCG vaccination prior to intravesicle instillation of BCG.

Mycobacteria-Based Vaccines as Immunotherapy for Non-urological Cancers

The arsenal against different types of cancers has increased impressively in the last decade. The detailed knowledge of the tumor microenvironment enables it to be manipulated in order to help the immune system fight against tumor cells by using specific checkpoint inhibitors, cell-based treatments, targeted antibodies, and immune stimulants. In fact, it is widely known that the first immunotherapeutic tools as immune stimulants for cancer treatment were bacteria and still are; specifically, the use of Mycobacterium bovis bacillus Calmette-Guérin (BCG) continues to be the treatment of choice for preventing cancer recurrence and progression in non-invasive bladder cancer. BCG and also other mycobacteria or their components are currently under study for the immunotherapeutic treatment of different malignancies. This review focuses on the preclinical and clinical assays using mycobacteria to treat non-urological cancers, providing a wide knowledge of the beneficial applications of these microorganisms to manipulate the tumor microenvironment aiming at tumor clearance.

Immune Responses in Bladder Cancer-Role of Immune Cell Populations, Prognostic Factors and Therapeutic Implications

Immunosurveillance, which describes the immunologically mediated elimination of transformed cells, has been widely accepted in the context of bladder cancer for many decades with the successful use of Bacillus-Calmette Guerin for superficial bladder cancer since the 1970s. With the emergence of checkpoint inhibitor blockade in the treatment of urothelial cancers, there has been a resurgent interest in the immunology of bladder cancer. The theory of cancer immunoediting proposes that the immune system has both pro-tumorigenic and anti-tumor effects, the balance between the two determining the progression of an individual tumor. However, whilst there is evidence for the action of various immune cell populations in bladder cancer, a cohesive picture of the immune response to bladder cancer and its driving forces are still lacking. Additionally, little is still known about the normal immune landscape of the bladder. Future progress in bladder cancer therapeutic approaches will require a strong foundation in understanding the immunology of this disease. This review considers the evidence for the role of the main immune cell populations, both innate and adaptive, in the immune response to bladder cancer. Recent research and overarching themes in the immune response to bladder cancer are explored. The minimal evidence regarding the normal immune landscape of the human bladder is also summarized to contextualize downstream immune responses. Of specific interest are the innate and myeloid populations, some of which are resident in the human bladder and which have significant effects on downstream adaptive tumor immunity. We discuss factors which restrain the efficacy of populations known to have anti-tumor activity such as cytotoxic T cells, including the constraints on checkpoint blockade. Additionally, the effects on the immune response of tumor intrinsic factors such as the genomic subtype of bladder cancer and the effect of common therapies such as chemotherapy and intravesical Bacillus Calmette-Guerin are considered. A significant theme is the polarization of immune responses within the tumor by a heavily immunosuppressive tumor microenvironment which affects the phenotype of multiple innate and adaptive populations. Throughout, clinical implications are discussed with suggestions for future research directions and therapeutic targeting.

Targeting Toll-Like Receptors for Cancer Therapy

The immune system encompasses a broad array of defense mechanisms against foreign threats, including invading pathogens and transformed neoplastic cells. Toll-like receptors (TLRs) are critically involved in innate immunity, serving as pattern recognition receptors whose stimulation leads to additional innate and adaptive immune responses. Malignant cells exploit the natural immunomodulatory functions of TLRs, expressed mainly by infiltrating immune cells but also aberrantly by tumor cells, to foster their survival, invasion, and evasion of anti-tumor immune responses. An extensive body of research has demonstrated context-specific roles for TLR activation in different malignancies, promoting disease progression in certain instances while limiting cancer growth in others. Despite these conflicting roles, TLR agonists have established therapeutic benefits as anti-cancer agents that activate immune cells in the tumor microenvironment and facilitate the expression of cytokines that allow for infiltration of anti-tumor lymphocytes and the suppression of oncogenic signaling pathways. This review focuses on the clinical application of TLR agonists for cancer treatment. We also highlight agents that are undergoing development in clinical trials, including investigations of TLR agonists in combination with other immunotherapies.

Induction of tumor-specific CD8+ cytotoxic T lymphocytes from naïve human T cells by using Mycobacterium-derived mycolic acid and lipoarabinomannan-stimulated dendritic cells

The main effectors in tumor control are the class I MHC molecule-restricted CD8⁺ cytotoxic T lymphocytes (CTLs). Tumor-specific CTL induction can be regulated by dendritic cells (DCs) expressing both tumor-derived epitopes and co-stimulatory molecules. Immunosuppressive tolerogenic DCs, having down-regulated co-stimulatory molecules, are seen within the tumor mass and can suppress tumor-specific CTL induction. The tolerogenic DCs expressing down-regulated XCR1⁺CD141⁺ appear to be induced by tumor-derived soluble factors or dexamethasone, while the immunogenic DCs usually express XCR1⁺CD141⁺ molecules with a cross-presentation function in humans. Thus, if tolerogenic DCs can be reactivated into immunogenic DCs with sufficient co-stimulatory molecules, tumor-specific CD8⁺ CTLs can be primed and activated in vivo. In the present study, we converted human tolerogenic CD141⁺ DCs with enhanced co-stimulatory molecule expression of CD40, CD80, and CD86 through stimulation with non-toxic mycobacterial lipids such as mycolic acid (MA) and lipoarabinomannan (LAM), which synergistically enhanced both co-stimulatory molecule expression and interleukin (IL)-12 secretion by XCR1⁺CD141⁺ DCs. Moreover, MA and LAM-stimulated DCs captured tumor antigens and presented tumor epitope(s) in association with class I MHCs and sufficient upregulated co-stimulatory molecules to prime naïve CD3⁺ T cells to become CD8⁺ tumor-specific CTLs. Repeat CD141⁺ DC stimulation with MA and LAM augmented the secretion of IL-12. These findings provide us a new method for altering the tumor environment by converting tolerogenic DCs to immunogenic DCs with MA and LAM from Mycobacterium tuberculosis.

Bladder cancer, a unique model to understand cancer immunity and develop immunotherapy approaches

With the mechanistic understanding of immune checkpoints and success in checkpoint blockade using antibodies for the treatment of certain cancers, immunotherapy has become one of the hottest areas in cancer research, with promise of long‐lasting therapeutic effect. Currently, however, only a proportion of cancers have a good response to checkpoint inhibition immunotherapy. Better understanding of the cancer response and resistance mechanisms is essential to fully explore the potential of immunotherapy to cure the majority of cancers. Bladder cancer, one of the most common and aggressive malignant diseases, has been successfully treated both at early and advanced stages by different immunotherapeutic approaches, bacillus Calmette–Guérin (BCG) intravesical instillation and anti‐PD‐1/PD‐L1 immune checkpoint blockade, respectively. Therefore, it provides a good model to investigate cancer immune response mechanisms and to improve the efficiency of immunotherapy. Here, we review bladder cancer immunotherapy with equal weight on BCG and anti‐PD‐1/PD‐L1 therapies and demonstrate why and how bladder cancer can be used as a model to study the predictors and mechanisms of cancer immune response and shine light on further development of immunotherapy approaches and response predictive biomarkers to improve immunotherapy of bladder cancer and other malignancies. We review the success of BCG and anti‐PD‐1/PD‐L1 treatment of bladder cancer, the underlying mechanisms and the therapeutic response predictors, including the limits to our knowledge. We then highlight briefly the adaptation of immunotherapy approaches and predictors developed in other cancers for bladder cancer therapy. Finally, we explore the potential of using bladder cancer as a model to investigate cancer immune response mechanisms and new therapeutic approaches, which may be translated into immunotherapy of other human cancers. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Cationized liposomal keto-mycolic acids isolated from Mycobacterium bovis bacillus Calmette-Guérin induce antitumor immunity in a syngeneic murine bladder cancer model

Intravesical therapy using Mycobacterium bovis bacillus Calmette-Guérin (BCG) is the most established cancer immunotherapy for bladder cancer. However, its underlying mechanisms are unknown. Mycolic acid (MA), the most abundant lipid of the BCG cell wall, is suspected to be one of the essential active components of this immunogenicity. Here, we developed cationic liposomes incorporating three subclasses (α, keto, and methoxy) of MA purified separately from BCG, using the dendron-bearing lipid D22. The cationic liposomes using D22 were efficiently taken up by the murine bladder cancer cell line MB49 in vitro, but the non-cationic liposomes were not. Lip-kMA, a cationic liposome containing keto-MA, presented strong antitumor activity in two murine syngeneic graft models using the murine bladder cancer cell lines MB49 and MBT-2 in comparison to both Lip-aMA and Lip-mMA, which contained α-MA and methoxy-MA, respectively. Interestingly, Lip-kMA(D12), which was made of D12 instead of D22, did not exhibit antitumor activity in the murine syngeneic graft model using MB49 cells, although it was successfully taken up by MB49 cells in vitro. Histologically, compared to the number of infiltrating CD4 lymphocytes, the number of CD8 lymphocytes was higher in the tumors treated with Lip-kMA. Antitumor effects of Lip-kMA were not observed in nude mice, whereas weak but significant effects were observed in beige mice with natural killer activity deficiency. Thus, a cationized liposome containing keto-MA derived from BCG induced in vivo antitumor immunity. These findings will provide new insights into lipid immunogenicity and the underlying mechanisms of BCG immunotherapy.

Prognostic impact of Bacillus Calmette-Guérin interruption at the time of induction and consolidation

CONTEXT

Intravesical Bacillus Calmette-Guérin (BCG) is a cause of bladder and systemic toxicity that is difficult to prevent and is responsible for treatment drop out in bladder cancer patients. More recently, BCG shortage has become the main cause of incomplete treatment.

AIMS

The aim of this study was to examine the impact on long-term prognosis of bladder cancer patients following discontinuation of BCG instillations.

SETTINGS AND DESIGN

In this retrospective study, data were examined from 333 consecutive nonmuscle invasive bladder cancer patients treated from 2005 to 2015 by transurethral resection (TUR) and had undergone adjuvant BCG therapy after TUR.

SUBJECTS AND METHODS

Rate of complete cure, the reason for the interruption, toxicity, and the associations between discontinuance of BCG therapy, tumor characteristics, association with carcinoma in situ and tumor recurrence or progression were analyzed.

STATISTICAL ANALYSIS USED

Recurrence and progression-free survival rate curves were estimated using the Kaplan-Meier method and were compared using the log-rank test. Univariate and multivariate analyses were performed using the Cox proportional hazards model. Differences among groups were considered as statistically significant when P < 0.05.

RESULTS

Overall, 303 patients were eligible for analysis. Median follow up was 36 (confidence interval: 7-120) months. A total of 55 (18.1%) had <6 installations (Group I); 87 (28.7%) completed induction and 1-year maintenance (Group III); and 161 (53.1%) completed the induction course, but not the 1-year maintenance (Group II). Grade III-IV toxicity rates were significantly higher in Group I than Group II and III. Interruption for BCG shortage was the main cause of interrupting BCG in Group II. Multivariate analysis showed that discontinuation of BCG induction therapy was an independent predictor for tumor recurrence (P < 0.001) and 1-year BCG maintenance therapy for tumor progression (P = 0.005).

CONCLUSIONS

Discontinuation of BCG therapy has a significantly deleterious effect on tumor recurrence and progression rates. Although BCG toxicity is a major cause of drop out, BCG shortage became a major cause of discontinuation. All effort must be done today to restore normal production of BCG worldwide.

Intravesical BCG Induces CD4+ T-Cell Expansion in an Immune Competent Model of Bladder Cancer

Intravesical bacillus Calmette-Guérin (BCG) immunotherapy is the standard of care in treating non-muscle-invasive bladder cancer, yet its mechanism of action remains elusive. Both innate and adaptive immune responses have been implicated in BCG activity. Although prior research has indirectly demonstrated the importance of T cells and shown a rise in CD4+ T cells in bladder tissue after BCG, T-cell subpopulations have not been fully characterized. We investigated the relationship between effector and regulatory T cells in an immune competent, clinically relevant rodent model of bladder cancer. Our data demonstrate that cancer progression in the N-methyl-N-nitrosourea (MNU) rat model of bladder cancer was characterized by a decline in the CD8/FoxP3 ratio, consistent with decreased adaptive immunity. In contrast, treatment with intravesical BCG led to a large, transient rise in the CD4+ T-cell population in the urothelium and was both more effective and immunogenic compared with intravesical chemotherapy. Whole-transcriptome expression profiling of posttreatment intravesical CD4+ and CD8+ T cells revealed minimal differences in gene expression after BCG treatment. Together, our results suggest that although BCG induces T-cell recruitment to the bladder, the T-cell phenotype does not markedly change, implying that combining T-cell-activating agents with BCG might improve clinical activity. Cancer Immunol Res; 5(7); 594-603. ©2017 AACR.

Characterization of a human anti-tumoral NK cell population expanded after BCG treatment of leukocytes

Immunotherapy, via intra-vesical instillations of BCG, is the therapy of choice for patients with high-risk non-muscle invasive bladder cancer. The subsequent recruitment of lymphocytes and myeloid cells, as well as the release of cytokines and chemokines, is believed to induce a local immune response that eliminates these tumors, but the detailed mechanisms of action of this therapy are not well understood. Here, we have studied the phenotype and function of the responding lymphocyte populations as well as the spectrum of cytokines and chemokines produced in an in vitro model of human peripheral blood mononuclear cells (PBMCs) co-cultured with BCG. Natural killer (NK) cell activation was a prominent feature of this immune response and we have studied the expansion of this lymphocyte population in detail. We show that, after BCG stimulation, CD56^dim NK cells proliferate, upregulate CD56, but maintain the expression of CD16 and the ability to mediate ADCC. CD56^bright NK cells also contribute to this expansion by increasing CD16 and KIR expression. These unconventional CD56^bright cells efficiently degranulated against bladder cancer cells and the expansion of this population required the release of soluble factors by other immune cells in the context of BCG. Consistent with these in vitro data, a small, but significant increase in the intensity of CD16 expression was noted in peripheral blood CD56^bright cells from bladder cancer patients undergoing BCG therapy, that was not observed in patients treated with mitomycin-C instillations. These observations suggest that activation of NK cells may be an important component of the anti-tumoral immune response triggered by BCG therapy in bladder cancer.

Natural Killer Cell Immunomodulation: Targeting Activating, Inhibitory, and Co-stimulatory Receptor Signaling for Cancer Immunotherapy

There is compelling clinical and experimental evidence to suggest that natural killer (NK) cells play a critical role in the recognition and eradication of tumors. Efforts at using NK cells as antitumor agents began over two decades ago, but recent advances in elucidating NK cell biology have accelerated the development of NK cell-targeting therapeutics. NK cell activation and the triggering of effector functions is governed by a complex set of activating and inhibitory receptors. In the early phases of cancer immune surveillance, NK cells directly identify and lyse cancer cells. Nascent transformed cells elicit NK cell activation and are eliminated. However, as tumors progress, cancerous cells develop immunosuppressive mechanisms that circumvent NK cell-mediated killing, allowing for tumor escape and proliferation. Therapeutic intervention aims to reverse tumor-induced NK cell suppression and sustain NK cells’ tumorlytic capacities. Here, we review tumor–NK cell interactions, discuss the mechanisms by which NK cells generate an antitumor immune response, and discuss NK cell-based therapeutic strategies targeting activating, inhibitory, and co-stimulatory receptors.

NKG2D is a Key Receptor for Recognition of Bladder Cancer Cells by IL-2-Activated NK Cells and BCG Promotes NK Cell Activation

Intravesical instillation of bacillus Calmette–Guérin (BCG) is used to treat superficial bladder cancer, either papillary tumors (after transurethral resection) or high-grade flat carcinomas (carcinoma in situ), reducing recurrence in about 70% of patients. Initially, BCG was proposed to work through an inflammatory response, mediated by phagocytic uptake of mycobacterial antigens and cytokine release. More recently, other immune effectors such as monocytes, natural killer (NK), and NKT cells have been suggested to play a role in this immune response. Here, we provide a comprehensive study of multiple bladder cancer cell lines as putative targets for immune cells and evaluated their recognition by NK cells in the presence and absence of BCG. We describe that different bladder cancer cells can express multiple activating and inhibitory ligands for NK cells. Recognition of bladder cancer cells depended mainly on NKG2D, with a contribution from NKp46. Surprisingly, exposure to BCG did not affect the immune phenotype of bladder cells nor increased NK cell recognition of purified IL-2-activated cell lines. However, NK cells were activated efficiently when BCG was included in mixed lymphocyte cultures, suggesting that NK activation after mycobacteria treatment requires the collaboration of various immune cells. We also analyzed the percentage of NK cells in peripheral blood of a cohort of bladder cancer patients treated with BCG. The total numbers of NK cells did not vary during treatment, indicating that a more detailed study of NK cell activation in the tumor site will be required to evaluate the response in each patient.

Cytokines as effectors and predictors of responses in the treatment of bladder cancer by bacillus Calmette-Guérin

The most effective intravesical treatment of non-muscle-invasive bladder cancer is instillation of live Mycobacterium bovis bacillus Calmette-Guérin (BCG). BCG stimulates the release of cytokines, contributing directly or indirectly to its effectiveness. However, the function of specific cytokines is not well understood. We have undertaken a nonsystematic review of primary evidence regarding cytokine detection, activation and response in BCG patients. Cytokines IL-2, IL-8 and TNF-α appear to be essential for effective BCG therapy and nonrecurrence, while IL-10 may have an inhibitory effect on BCG responses. IL-2, IL-8, TRAIL and TNF-α are potentially predictive of response to BCG. Alterations in genes encoding cytokines may also affect responses. There are significant data showing the association of certain cytokines with successful BCG treatment, and which may be useful predictive markers. Isolating those cytokines mediating efficacy may hold the key to ameliorating BCG's side effects and improving efficacy and patient compliance.

Th1 cytokine-based immunotherapy for cancer

Cytokine-based immunotherapy is executed by harnessing cytokines to activate the immune system to suppress tumors. Th1-type cytokines including IL-1, IL-2, IL-12 and granulocyte-macrophage colony-stimulating factor are potent stimulators of Th1 differentiation and Th1-based antitumor response. Many preclinical studies demonstrated the antitumor effects of Th1 cytokines but their clinical efficacy is limited. Multiple factors influence the efficacy of immunotherapy for tumors. For instance immunosuppressive cells in the tumor microenvironment can produce inhibitory cytokines which suppress antitumor immune response. Most studies on cytokine immunotherapy focused on how to boost Th1 response; many studies combined cytokine-based therapy with other treatments to reverse immunosuppression in tumor microenvironment. In addition, cytokines have pleiotropic functions and some cytokines show paradoxical activities under different settings. Better understanding the physiological and pathological functions of cytokines helps clinicians to design Th1-based cancer therapy in clinical practice.

Viral warfare! Front-line defence and arming the immune system against cancer using oncolytic vaccinia and other viruses

BACKGROUND

Despite mankind's many achievements, we are yet to find a cure for cancer. We are now approaching a new era which recognises the promise of harnessing the immune system for anti-cancer therapy. Pathogens have been implicated for decades as potential anti-cancer agents, but implementation into clinical therapy has been plagued with significant drawbacks. Newer 'designer' agents have addressed some of these concerns, in particular, a new breed of oncolytic virus: JX-594, a genetically engineered pox virus, is showing promise.

OBJECTIVE

To review the current literature on the use of oncolytic viruses in the treatment of cancer; both by direct oncolysis and stimulation of the immune system. The review will provide a background and historical progression for the surgeon on tumour immunology, and the interplay between oncolytic viruses, immune cells, inflammation on tumourigenesis.

METHODS

A literature review was performed using the Medline database.

CONCLUSIONS

Viral therapeutics hold promise as a novel treatment modality for the treatment of disseminated malignancy. It provides a multi-pronged attack against tumour burden; direct tumour cell lysis, exposure of tumour-associated antigens (TAA), induction of immune danger signals, and recognition by immune effector cells.

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.

Antigen-specific CD4 T cells are induced after intravesical BCG-instillation therapy in patients with bladder cancer and show similar cytokine profiles as in active tuberculosis

Specific T cell immunity in patients with active tuberculosis is associated with a decrease in multifunctionality. However, it is unknown whether cytokine profiles differ in patients with primary infection and those with prior contact. We therefore used intravesical immunotherapy with attenuated live Bacille Calmette–Guérin (BCG) in patients with urothelial carcinoma as a model to characterise the induction of systemic immunity towards purified protein derivate (PPD) and to study whether cytokine profiles differ depending on pre-existing immunity. Eighteen patients with non-muscle invasive bladder cancer were recruited during the BCG-induction course. Fifty-four healthy individuals served as controls. Interferon (IFN)-γ and interleukin (IL)-2 producing PPD-specific CD4 T cells were analysed longitudinally before each instillation using a rapid flow-cytometric whole blood immunoassay. Baseline levels of IFN-γ producing PPD-specific T cells were comparable to controls. T cells showed a 5-fold increase to 0.23% by week 2/3, and further increased 8-fold by week 4/5 (to 0.42%, p=0.0007). Systemic immunity was induced in all patients, although the increase was less pronounced in patients with pre-existing immunity. As in active TB, cytokine profiling during therapy revealed a lower percentage of multifunctional IFN-γ/IL-2 double-positive T cells compared to controls (60.2% vs. 71.9%, p=0.0003). Of note, when comparing patients with and without pre-existing immunity, cytokine profiles in patients with primary immunity were shifted towards IL-2 single producing T cells (p=0.02), whereas those in patients with pre-existing immunity were shifted towards IFN-γ single-positivity (p=0.01). In conclusion, systemic T cell responses were induced after BCG-therapy, and their kinetics and cytokine profile depended on pre-existing immunity. Decreased functionality is a typical feature of specific immunity in both patients with active tuberculosis and BCG-therapy. Among patients with active infection, a shift towards IL-2 or IFN-γ single-positive cells may allow distinction between patients with primary infection and cases with boosted immunity after prior contact, respectively.

IMAC fractionation in combination with LC-MS reveals H2B and NIF-1 peptides as potential bladder cancer biomarkers

Improvement in bladder cancer (BC) management requires more effective diagnosis and prognosis of disease recurrence and progression. Urinary biomarkers attract special interest because of the noninvasive means of urine collection. Proteomic analysis of urine entails the adoption of a fractionation methodology to reduce sample complexity. In this study, we applied immobilized metal affinity chromatography in combination with high-resolution LC-MS/MS for the discovery of native urinary peptides potentially associated with BC aggressiveness. This approach was employed toward urine samples from patients with invasive BC, noninvasive BC, and benign urogenital diseases. A total of 1845 peptides were identified, corresponding to a total of 638 precursor proteins. Specific enrichment for proteins involved in nucleosome assembly and for zinc-finger transcription factors was observed. The differential expression of two candidate biomarkers, histone H2B and NIF-1 (zinc finger 335) in BC, was verified in independent sets of urine samples by ELISA and by immunohistochemical analysis of BC tissue. The results collectively support changes in the expression of both of these proteins with tumor progression, suggesting their potential role as markers for discriminating BC stages. In addition, the data indicate a possible involvement of NIF-1 in BC progression, likely as a suppressor and through interactions with Sox9 and HoxA1.

Alterations of dendritic cell subsets and TH1/TH2 cytokines in the peripheral circulation of patients with superficial transitional cell carcinoma of the bladder

BACKGROUND

Dendritic cells (DCs) and cytokines play an important role in the tumor growth and recurrence.

METHODS

Sixty-six patients with superficial transitional cell carcinoma of the bladder (STCCB) and 38 healthy controls were studied to investigate the percentages of DC subsets, monocyte-derived DC (MoDC) function, and alterations of Th1 and Th2 cytokines. MoDCs were generated and three-color flow cytometry was used for determining the phenotype of MoDCs and DC subsets. The ability to stimulate autologous T cells was tested in mixed leukocyte reaction (MLR). The levels of various cytokines were measured using commercially available sandwich enzyme linked immunosorbent assay (ELISA) kit.

RESULTS

The myeloid DC (mDC) counts, MoDC surface molecular expression, and stimulatory capacity to T cells were impaired in STCCB patients than in controls. The percentage of mDC and the expression of CD80, CD83, and CD86 were lower in patients showing recurrence. The serum levels of IL-2 and IFN-γ were found to be significantly lower while IL-4, IL-6, and IL-10 were significantly higher in STCCB patients than in controls. IL-6 was found to be significantly higher in recurrent patients.

CONCLUSION

The impairment of mDC counts and MoDC function with imbalance of Th1/Th2 cytokines was closely associated with proliferation and recurrence of STCCB.

Induction of T cell responses and recruitment of an inflammatory dendritic cell subset following tumor immunotherapy with Mycobacterium smegmatis

Mycobacteria and their cell wall components have been used with varying degrees of success to treat tumors, and Mycobacterium bovis BCG remains in use as a standard treatment for superficial bladder cancer. Mycobacterial immunotherapy is very effective in eliciting local immune responses against solid tumors when administered topically; however, its effectiveness in eliciting adaptive immune responses has been variable. Using a subcutaneous mouse thymoma model, we investigated whether immunotherapy with Mycobacterium smegmatis, a fast-growing mycobacterium of low pathogenicity, induces a systemic adaptive immune response. We found that M. smegmatis delivered adjacent to the tumor site elicited a systemic anti-tumor immune response that was primarily mediated by CD8(+) T cells. Of note, we identified a CD11c(+)CD40(int)CD11b(hi)Gr-1(+) inflammatory DC population in the tumor-draining lymph nodes that was found only in mice treated with M. smegmatis. Our data suggest that, rather than rescuing the function of the DC already present in the tumor and/or tumor-draining lymph node, M. smegmatis treatment may promote anti-tumor immune responses by inducing the involvement of a new population of inflammatory cells with intact function.

A Mycobacterium bovis Mycotic Abdominal Aortic Aneurysm Resulting From Bladder Cancer Treatment, Resection, and Reconstruction With a Cryopreserved Aortic Graft

Mycotic abdominal aortic aneurysms (AAAs) are a clinical challenge for vascular surgeons due to their critical location, surrounding inflammation, risk of rupture, and danger of reinfection following treatment. We present a case of Mycobacterium bovis AAA in a 69-year-old male after treatment with intravesicular bacillus Calmette-Guérin (BCG) therapy for bladder carcinoma. The classical approach for mycotic AAA entails extra-anatomic reconstruction followed by resection with oversewing of the proximal and distal aortic stumps. Alternative in-line reconstruction options have also been advocated. This case illustrates a technically straightforward, durable, in-line repair within an infected field utilizing cryopreserved aortic allograft.

Targeting pattern recognition receptors in cancer immunotherapy

Pattern recognition receptors (PRRs) are known for many years for their role in the recognition of microbial products and the subsequent activation of the immune system. The 2011 Nobel Prize for medicine indeed rewarded J. Hoffmann/B. Beutler and R. Steinman for their revolutionary findings concerning the activation of the immune system, thus stressing the significance of understanding the mechanisms of activation of the innate immunity. Such immunostimulatory activities are of major interest in the context of cancer to induce long-term antitumoral responses. Ligands for the toll-like receptors (TLRs), a well-known family of PRR, have been shown to have antitumoral activities in several cancers. Those ligands are now undergoing extensive clinical investigations both as immunostimulant molecules and as adjuvant along with vaccines. However, when considering the use of these ligands in tumor therapy, one shall consider the potential effect on the tumor cells themselves as well as on the entire organism. Recent data indeed demonstrate that TLR activation in tumor cells could trigger both pro- or antitumoral effect depending on the context. This review discusses this balance between the intrinsic activation of PRR in tumor cells and the extrinsic microenvironment activation in term of overall effect of PRR ligands on tumor development. We review recent advances in the field and underline appealing prospects for clinical development of PRR agonists in the light of our current knowledge on their expression and activation.

Cancer vaccines

While vaccines are primarily thought of in terms of their use for prevention of infectious diseases, they can potentially be used to prevent or treat cancer. This manuscript explores the rationale for vaccines and immunotherapies for cancer from both the scientific and the global needs perspectives. Pathogens that are aetiologic agents of certain cancers provide perhaps the most obvious successful examples of the prophylactic utility of vaccines (such as the hepatitis B vaccine) to prevent not just the infectious disease (hepatitis), but the potential subsequent cancer (hepatocellular carcinoma). The use of monoclonal antibodies illustrates the effectiveness of the immune system for cancer therapy. In addition, the increased understanding of the role and mechanisms of the immune system in the processes of immune surveillance, as well as of its failure during immunosuppression, have yielded better insights into how to design cancer vaccines and immunotherapies. Examples of targets for cancer vaccines will be discussed, as will the challenges and few successes in this arena.

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.

Granulomas do pênis: uma complicação rara da terapia intravesical com Bacilo Calmette-Guérin

A imunoterapia com o Bacilo Calmette-Guérin é amplamente usada no tratamento e profilaxia da neoplasia urotelial superficial. As complicações associadas ao tratamento são comuns. Os autores relatam um caso de inflamação granulomatosa do pênis, associada à terapia intravesical com Bacilo Calmette-Guérin, com múltiplos nódulos eritematosos indolores localizados na glande. É também efetuada uma revisão da literatura. A balanopostite granulomatosa é uma complicação rara associada à imunoterapia com Bacilo Calmette-Guérin, com uma apresentação clinicamente heterogênea que pode dificultar o diagnóstico. O seu reconhecimento clínico é essencial para o início precoce de tuberculostáticos e interrupção de Bacilo Calmette-Guérin

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.

The liposome-incorporating cell wall skeleton of Mycobacterium bovis bacillus Calmette-Guéin can directly enhance the susceptibility of cancer cells to lymphokine-activated killer cells through up-regulation of natural-killer group 2, member D ligands

OBJECTIVE

• To conduct a preclinical evaluation of the ability of natural killer cells to cytolyze bladder cancer cells that were modified to show enhanced expression of natural-killer group 2, member D (NKG2D) ligands by R8-liposome-bacillus Calmette-Guéin (BCG)-cell wall skeleton (CWS) treatment.

MATERIALS AND METHODS

• The T24 cells and RT-112 cells were co-cultured with R8-liposome-BCG-CWS and BCG for 2, 4, or 6 h, and then the surface expression of NKG2D ligands was analyzed using TaqMan real-time quantitative RT-PCR. • Peripheral blood mononuclear cells were obtained with a conventional preparation kit, and then lymphokine-activated killer (LAK) cells were generated from these purified peripheral blood mononuclear cells via interleukin-2 stimulation. • The anti-tumour effect of LAK cells against untreated and R8-liposome-BCG-CWS co-cultured with cells of the human bladder cancer cell lines T24 and RT-112 was analyzed using the cytotoxic WST-8 assay method at 4 h of culture at various effector/target (E : T) ratios.

RESULTS

• Major histocompatibility complex class I-related chain B (MICB) expression was increased ≈1.5-fold on T24 cells and RT-112 cells with BCG. • UL-16-binding protein (ULBP) 1 expression was also increased ≈1.5-fold on T24 cells and RT-112 cells with BCG. R8-liposome-BCG-CWS increased the surface expression of MICB 2.2-fold on T24 cells but did not increase it significantly on RT-112 cells. • ULBP1 expression was increased ≈2.2-fold on RT-112 cells, although no differences were observed between the expression of ULBP2 and 3 with R8-liposome-BCG-CWS. • T24 cells that were co-cultured with R8-liposome-BCG-CWS showed an ≈1.3-fold increase in sensitivity to cytolysis by LAK cells at an E : T ratio of 4 and RT-112 cells showed an ≈1.4-fold increase at an E : T ratio of 2.

CONCLUSIONS

• In the present study, the induction of surface NKG2D ligands by R8-liposome-BCG-CWS rendered cancer cells more susceptible to cytolysis by LAK cells. • T24 cells and RT-112 cells, even when cultured singly in the absence of immune cells, can directly respond to R8-liposome-BCG-CWS. • The results obtained in the present study may therefore indicate a novel adoptive immunotherapy against bladder cancers.

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.

Recent advances in bacillus Calmette–Guerin immunotherapy in bladder cancer

The concept of using Mycobacterium for cancer treatment goes back to the 19th Century. Today, bacillus Calmette–Guerin (BCG) vaccine is a well-established treatment for human bladder cancer that is arguably superior to intravesical chemotherapy for superficial disease and is commonly used as the first-line adjuvant treatment. Much has been learnt about the effects of BCG on bladder cancer and the immune system, but deeper understanding is required in order to improve its efficacy further, to be able to reliably predict responders and ultimately to adapt this most successful form of cancer immunotherapy for the treatment of other malignancies. This article summarizes the current understanding of BCG cancer immunotherapy mechanisms and discusses possible future developments.

Transformation of breast milk macrophages by HTLV-I: implications for HTLV-I transmission via breastfeeding

Human T cell leukemia virus type I (HTLV-I), a causative agent of adult T-cell leukemia (ATL), is transmitted from mother to child predominantly by breastfeeding. The source of HTLV-I-infected cells in breast milk has been thought to be T cells, however, the majority of cells in breast milk are CD14(+) macrophages but not CD3(+) T lymphocytes, and no data are available regarding HTLV-I transmission through breast milk macrophages (BrMMpsi). To explore the potential of BrMMpsi as a possible source of infection in mother to child transmission (MTCT) of HTLV-I, an immortalized cell line (HTLV-BrMMpsi) has been established from BrMMpsi by infection with HTLV-I. HTLV-BrMMpsi retained macrophage characteristics and did not express a complete dendritic cell (DC) phenotype; nevertheless, HTLV-BrMMpsi efficiently promoted T cell proliferation in primary allogeneic mixed lymphocyte reaction (MLR) like DC. Moreover, HTLV-I infection could be transmitted from HTLV-BrMMpsi to activated T cells in the peripheral blood. These findings suggested that BrMMpsi might be an appropriate HTLV-I reservoir involved in MTCT transmission via breastfeeding.