Bacillus-calmette-guerin (bcg) organisms directly alter the growth of bladder-tumor cells

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.

Advances and Controversies With Checkpoint Inhibitors in Bladder Cancer

Immune checkpoint inhibitors have revolutionized the treatment of bladder urothelial cancers and have wide application in almost all disease states. Although several drugs have initially been shown to be beneficial in the second-line metastatic setting, there are still ongoing controversies and debate, including voluntary withdrawals of durvalumab and atezolizumab, along with the approval of agents in the first-line setting in the cisplatin-ineligible state based on inconsistent confirmatory phase III trials. As novel immunotherapy drugs are discovered and studied in various phases of clinical trials, these agents will continue to change the treatment landscape for bladder cancer patients. This review will discuss current available evidence and information and key pivotal trials using checkpoint inhibitors in bladder cancer.

Mathematical model of tumor immunotherapy for bladder carcinoma identifies the limitations of the innate immune response

Treatment for non-muscle invasive carcinoma of the bladder represents one of the few examples of successful tumor immunity. Six weekly intravesical instillations of Bacillus Calmette-Guerin (BCG), often followed by maintenance schedule, result in up to 50-70% clinical response. Current models suggest that the mechanism of action involves the non-specific activation of innate effector cells, which may be capable of acting in the absence of an antigen-specific response. For example, recent evidence suggests that BCG-activated neutrophils possess anti-tumor potential. Moreover, weekly BCG treatment results in a prime-boost pattern with massive influx of innate immune cells (107-108 PMN/ml urine). Calibrating in vivo data, we estimate that the number of neutrophil degranulations per instillation is approximately 106-107, more than sufficient to potentially eliminate ~106 residual tumor cells. Furthermore, neutrophils, as well as other innate effector cells are not selective in their targeting-thus surrounding cells may be influenced by degranulation and / or cytokine production. To establish if these observed conditions could account for clinically effective tumor immunity, we built a mathematical model reflecting the early events and tissue conditioning in patients undergoing BCG therapy. The model incorporates key features of tumor growth, BCG instillations and the observed prime / boost pattern of the innate immune response. Model calibration established that each innate effector cell must kill 90-95 bystander cells for achieving the expected 50-70% clinical response. This prediction was evaluated both empirically and experimentally and found to vastly exceed the capacity of the innate immune system. We therefore conclude that the innate immune system alone is unable to eliminate the tumor cells. We infer that other aspects of the immune response (e.g., antigen-specific lymphocytes) decisively contribute to the success of BCG immunotherapy.

The efficacy and safety of intravesical gemcitabine vs Bacille Calmette-Guérin for adjuvant treatment of non-muscle invasive bladder cancer: a meta-analysis

Objective

Several studies have compared the safety and efficacy of intravesical gemcitabine (Gem) with Bacille Calmette-Guérin (BCG) for non-muscle invasive bladder cancer. However, the results are not consistent. We carried out a meta-analysis to provide a more comprehensive analysis of the efficacy and safety of these 2 drugs.

Methods

We searched PubMed, EMBASE, Cochrane Library, ClinicalTrials.gov, and reference lists. Randomized controlled trials and retrospective controlled trials comparing intravesical Gem and BCG in adjuvant therapy for non-muscle invasive bladder cancer published in Eng-lish were included in this study. The strength of association was weighed by pooled risk ratio (RR) with 95% CIs. Sensitivity analysis was performed to examine whether the findings of the meta-analysis were robust.

Results

We analyzed 386 subjects from 5 pooled trials. Compared with BCG, intravesical Gem had lower incidence of dysuria (overall RR =0.31, 95% CI: 0.16, 0.61, I²=0%, p=0.001) and hematuria (overall RR =0.27, 95% CI: 0.11, 0.71, I²=0%, p=0.008). There were no statistical differences in risk of recurrence, progression, incidence of fever, and any adverse events between intravesical Gem and BCG therapy (p>0.05). No publication bias was found.

Conclusion

This meta-analysis suggests that intravesical Gem may have similar efficacy and lower incidence of dysuria and hematuria compared with BCG. Nevertheless, we recommend additional high-quality randomized controlled trials to confirm these results.

Renal Granulomatosis Post Intravesical Bacillus Calmette-Guerin Therapy for Non-muscle-invasive Bladder Cancer

Intravesical Bacillus Calmette–Guerin (BCG) immunotherapy is a proven, effective treatment for intermediate- and high-risk non-muscle-invasive bladder cancer. Minor side effects are common and expected but systemic effects can occur in <5% of treated patients. We present a rare case of a 49-year-old male that presented with fever and chills after 3 weeks of intravesical BCG therapy post transurethral resection of bladder tumor. New renal lesions were present on contrast-enhanced computed tomography scan which was histologically proven to be necrotizing renal granulomatosis.

The Dose-Response Relationship of bacillus Calmette-Guérin and Urothelial Carcinoma Cell Biology

PURPOSE

Attenuated mycobacterium bacillus Calmette-Guérin is widely used as intravesical immunotherapy of nonmuscle invasive urothelial carcinoma. Currently there are limited data on the relationship between bacillus Calmette-Guérin dose intensity and tumor response. We evaluated the dose-response relationship of bacillus Calmette-Guérin to nonmuscle invasive bladder cancer in vitro using urothelial carcinoma cell lines and in vivo using an orthotopic mouse model.

MATERIALS AND METHODS

Two human urothelial carcinoma cell lines were used to study the effect of bacillus Calmette-Guérin dose on the tumor cell response. Internalization, activation of signaling pathways, gene transactivation, cell viability, lactate dehydrogenase and HMGB1 release were study end points. An orthotopic tumor model was used to compare the effect of different doses on the antitumor efficacy of bacillus Calmette-Guérin.

RESULTS

Bacillus Calmette-Guérin internalization by urothelial carcinoma cells increased as a function of time and dose with a plateau at higher doses and/or long exposure times. Intracellular signaling demonstrated a similar direct, dose dependent increase. Cytokine expression by urothelial carcinoma cells as a function of dose was variable. Some genes increased progressively but others showed a decrease at the highest dose. While nonviable cell number increased in proportion to dose, the number of cells undergoing necrotic cell death decreased at higher doses. A higher dose of bacillus Calmette-Guérin (1:200) showed a better antitumor effect than a standard dose (1:50) (p <0.01).

CONCLUSIONS

Bacillus Calmette-Guérin dose has a direct impact on urothelial carcinoma cell biology. Increased dose intensity, particularly in nonresponders, may represent a strategy to increase bacillus Calmette-Guérin treatment efficacy.

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.

Enhancing the immunotherapeutic potential of mycobacteria by transfection with tumour necrosis factor-alpha

In an attempt to enhance the anti-tumour properties of mycobacteria we have developed recombinant forms of Mycobacterium smegmatis which express and secrete biologically active human tumour necrosis factor-alpha (TNF-alpha). This was achieved by transfecting M. smegmatis using shuttle plasmids incorporating the cDNA sequence for the human TNF-alpha mature peptide. In vitro experiments on a panel of human bladder tumour cell lines (EJ18, MGH-U1, RT4, RT112) indicate that our genetically modified mycobacteria are more effective than wild-type at inducing or up-regulating the expression of intracellular adhesion molecule-1 and the secretion of an array of proinflammatory cytokines [interleukin-1 (IL-1), IL-6, IL-8, granulocyte-macrophage colony-stimulating factor]. We have also demonstrated increased adhesion molecule and cytokine expression in response to mycobacteria transfected with vector containing no gene insert. However, this was not as pronounced as that observed following tumour cell stimulation by the TNF-alpha-transfected strain. In contrast, in three out of four tumour cell lines all M. smegmatis strains were found to down-regulate the secretion of the anti-inflammatory cytokine transforming growth factor-beta1. Our studies have also confirmed that M. smegmatis is a powerful inhibitor of bladder tumour cell growth and revealed that its antiproliferative potency is enhanced by transfecting with human TNF-alpha and, to a lesser extent, with vector alone. All M. smegmatis strains were effective in the activation of peripheral blood leucocyte cultures. However, no differences were observed in the ability of the TNF-alpha-transfected, mock-transfected and wild-type mycobacteria to induce tumour cell killing activity. These results suggest that the immunomodulatory effects of M. smegmatis can be enhanced by transfection with vectors which allow the secretion of human TNF-alpha, thus increasing mycobacterial immunotherapeutic potential.

Production of urinary tumour necrosis factors and soluble tumour necrosis factor receptors in bladder cancer patients after bacillus Calmette-Guérin immunotherapy

Intravesical immunotherapy for bladder cancer is the most effective form of tumour immunotherapy. Following repeated instillations of bacillus Calmette-Guérin (BCG) organisms into the bladder large quantities of several cytokines are detected in the urine. These cytokines include interleukins IL-1 beta, IL-2, IL-4, IL-6, IL-8, IL-10, tumour necrosis factor alpha (TNF alpha), interferon gamma (IFN gamma) and also soluble intercellular adhesion molecule ICAM-1. In the work reported here we simultaneously quantified urinary levels of TNF alpha, TNF beta, TNF receptor I and TNF receptor II by enzyme-linked immunosorbent assay (ELISA) techniques and compared this with bioactive levels of TNF. This was undertaken with a limited number of patients throughout a course of six instillations of immunotherapy. Sequential instillations of BCG induced secretion of TNF alpha and TNF beta into urine. These cytokines were not always secreted simultaneously, perhaps suggesting differential regulation of their synthesis. Maximal concentrations of TNF alpha were 675 pg/ml and TNF beta 47 pg/ml. High levels of both species of soluble TNF receptor were readily identified in urine. Maximal levels of sTNF-RI were 6200 pg/ml (range from 0) and for sTNF-RII 7800 pg/ml (range from 0). Contrasting with earlier published observations concerning cytokine levels, the concentration of soluble receptor did not increase with repeated instillation. In apparent contrast with the ELISA data, very low levels of bioactive TNF were identified by the L929 bioassay (maximum concentration 1 U/ml) despite the elevated concentration of immunoreactive TNF. The large concentrations of soluble TNF receptor in patients' urine samples could account for the apparently low bioactivity as determined by the L929 cytotoxicity assay. The precise nature of the role of TNF in BCG immunotherapy remains undetermined; however, it is thought that proinflammatory cytokines are in part responsible for the clinical efficacy of this therapeutic approach. Whether other cytokines are antogonised by soluble binding proteins remains to be determined. Furthermore, whether TNF is bioactive in the bladder wall and only neutralised in the urine also requires investigation.