The essential role of interferon-gamma during interleukin-12 therapy for murine transitional cell carcinoma of the bladder

The past, present, and future of immunotherapy for bladder tumors

Bladder cancer is a prominent cancer worldwide with a relatively low survival rate for patients with increased stage and metastasis. Current treatments are based on surgical removal, bacillus Calmette-Guerin (BCG) Immunotherapy, and platinum-based chemotherapy. However, treatment resistance due to genetic instability of bladder tumors, as well as intolerance to treatment adverse effects leads to the necessity to further treatment options. New advancements in immunotherapy are on the rise for treatment of various cancers and specifically has shown promise in the treatment of bladder cancer. This review summarizes these new advancements in treatment options involving cytokines and cytokine blockade. Such a study might be helpful for urologists to manage patients with bladder cancer more effectively.

Non-stem bladder cancer cell-derived extracellular vesicles promote cancer stem cell survival in response to chemotherapy

BACKGROUND

Chemosenstive non-stem cancer cells (NSCCs) constitute the bulk of tumors and are considered as part of the cancer stem cell (CSC) niche in the tumor microenvironment (TME). Tumor-derived extracellular vesicles (EVs) mediate the communication between tumors and the TME. In this study, we sought to investigate the impacts of EVs released by NSCCs on the maintenance of CSC properties and chemoresistance.

METHODS

We employed murine MB49 bladder cancer (BC) sub-lines representing CSCs and NSCCs as a model system. Chemotherapy drugs were used to treat NSCCs in order to collect conditioned EVs. The impacts of NSCC-derived EVs on CSC progression were evaluated through sphere formation, cytotoxicity, migration, and invasion assays, and by analyzing surface marker expression on these BC cells. Differential proteomic analyses were conducted to identify cargo protein candidates involved in the EV-mediated communication between NSCCs and CSCs.

RESULTS

NSCC-derived EVs contained cargo proteins enriched in proteostasis-related functions, and significantly altered the development of CSCs such that they were more intrinsically chemoresistant, aggressive, and better able to undergo self-renewal.

CONCLUSIONS

We thus identified a novel communication mechanism whereby NSCC-EVs can alter the relative fitness of CSCs to promote disease progression and the acquisition of chemoresistance.

Enhanced metastatic potential in the MB49 urothelial carcinoma model

Recent data suggest that patients with a basal/stem-like bladder cancer (BC) subtype tend to have metastatic disease, but this is unconfirmed. Here we report the identification of murine MB49 cell line sub-clones with stem-like characteristics in culture. Subcutaneous implantation of S2 and S4 MB49 sub-clones into immunocompetent mice resulted in lung metastases in 50% and 80% of mice respectively, whereas none of the mice implanted with the parental cells developed metastasis. Gene profiling of cells cultured from S2 and S4 primary and metastatic tumors revealed that a panel of genes with basal/stem-like/EMT properties is amplified during metastatic progression. Among them, ITGB1, TWIST1 and KRT6B are consistently up-regulated in metastatic tumors of both MB49 sub-clones. To evaluate clinical relevance, we examined these genes in a human public dataset and found that ITGB1 and KRT6B expression in BC patient tumor samples are positively correlated with tumor grade. Likewise, the expression levels of these three genes are correlated with worse clinical outcomes. This MB49 BC metastatic pre-clinical model provides a unique opportunity to validate and recapitulate results discovered in patient studies and to pursue future mechanistic therapeutic interventions for BC metastasis.

Interdependent IL-7 and IFN-γ signalling in T-cell controls tumour eradication by combined α-CTLA-4+α-PD-1 therapy

Combination therapy with α-CTLA-4 and α-PD-1 has shown significant clinical responses in different types of cancer. However, the underlying mechanisms remain elusive. Here, combining detailed analysis of human tumour samples with preclinical tumour models, we report that concomitant blockade of CTLA-4 and PD-1 improves anti-tumour immune responses and synergistically eradicates tumour. Mechanistically, combination therapy relies on the interdependence between IL-7 and IFN-γ signalling in T cells, as lack of either pathway abrogates the immune-boosting and therapeutic effects of combination therapy. Combination treatment increases IL-7Rα expression on tumour-infiltrating T cells in an IFN-γ/IFN-γR signalling-dependent manner, which may serve as a potential biomarker for clinical trials with immune checkpoint blockade. Our data suggest that combining immune checkpoint blockade with IL-7 signalling could be an effective modality to improve immunotherapeutic efficacy. Taken together, we conclude that combination therapy potently reverses immunosuppression and eradicates tumours via an intricate interplay between IFN-γ/IFN-γR and IL-7/IL-7R pathways.

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.

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.

Intravesical immunotherapy of superficial bladder cancer with chitosan/interleukin-12

Intravesical BCG has been used successfully to treat superficial bladder cancer for three decades. However, 20% to 30% of patients will fail initial BCG therapy and 30% to 50% of patients will develop recurrent tumors within 5 years. Alternative or complementary strategies for the management of superficial bladder cancer are needed. Interleukin-12 (IL-12) is a potent T(H)1 cytokine with robust antitumor activity and the ability to potentiate immunologic memory. Unfortunately, intravesical IL-12 did not show antitumor efficacy in a recent clinical study of patients with recurrent superficial bladder cancer. We hypothesized that coformulation of IL-12 with chitosan, a biocompatible, mucoadhesive polysaccharide, could improve intravesical IL-12 delivery and provide an effective and durable alternative for the treatment of superficial bladder cancer. In antitumor studies, 88% to 100% of mice bearing orthotopic bladder tumors were cured after four intravesical treatments with chitosan/IL-12. In contrast, only 38% to 60% of mice treated with IL-12 alone and 0% treated with BCG were cured. Antitumor responses following chitosan/IL-12 treatments were durable and provided complete protection from intravesical tumor rechallenge. Urinary cytokine analysis showed that chitosan/IL-12 induced multiple T(H)1 cytokines at levels significantly higher than either IL-12 alone or BCG. Immunohistochemistry revealed moderate to intense tumor infiltration by T cells and macrophages following chitosan/IL-12 treatments. Bladder submucosa from cured mice contained residual populations of immune cells that returned to baseline levels after several months. Intravesical chitosan/IL-12 is a well-tolerated, effective immunotherapy that deserves further consideration for testing in humans for the management of superficial bladder cancer.

Role of Th1-stimulating cytokines in bacillus Calmette-Guérin (BCG)-induced macrophage cytotoxicity against mouse bladder cancer MBT-2 cells

Previously, we have demonstrated that macrophages exhibited cytotoxicity toward mouse bladder cancer MBT-2 cells upon bacille Calmette-Guérin (BCG) stimulation. In this study, we have investigated the role of Th1-stimulating cytokines in BCG-induced macrophage cytotoxicity. Thioglycollate-elicited peritoneal exudate cells (PECs) were used as a conventional source for macrophages and the induction of PEC effector functions (cytolytic activity and cytokine production) by BCG was evaluated in vitro. The BCG-activated PECs showed potent cytotoxicity and killed MBT-2 cells in a dose-dependent manner. Depletion of T cells, natural killer (NK) cells, or both, in PEC preparations exhibited a marginal or small reduction of MBT-2 cell killing, suggesting that macrophages played a primary role in PEC cytotoxicity. Transwell assays indicated that the maximal PEC cytotoxicity required both direct cell-cell contact and soluble factors such as interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha. Neutralizing endogenous cytokines interleukin (IL)-12, IL-18, IFN-gamma or TNF-alpha reduced PEC cytotoxicity by 38%, 22%, 15% and 94%, respectively. Supplementation of BCG with recombinant (r)IL-2, rIL-12 or rIL-18 increased PEC cytotoxicity by approximately twofold. Compared with control BCG for PEC stimulation, rBCGs expressing IL-2 or IL-18 showed enhanced MBT-2 cell killing by PECs. Increased cytokine production (IFN-gamma, TNF-alpha and IL-6) was also observed in rBCG-stimulated PEC cultures. Taken together, these results suggest that Th1-stimulating cytokines play an important role in BCG-induced macrophage cytotoxicity and that combination of BCG with selected Th1-stimulating cytokines, either supplemented or expressed by BCG, may enhance the effect of BCG in the treatment of bladder cancer patients.

Use of prostate specific antigen to measure bladder tumor growth in a mouse orthotopic model

PURPOSE

Animal orthotopic tumor models are commonly used in bladder cancer studies. However, to our knowledge there is currently no accurate method to quantify tumor growth inside the bladder in living animals. We used prostate specific antigen (PSA) as a marker to cope with this limitation.

MATERIALS AND METHODS

Infectious but replication incompetent retroviral particles carrying PSA coding sequence were constructed and infected into MB49 cells, a mouse bladder transitional cell carcinoma line of C57BL/6 origin. Syngeneic mice were intravesically implanted with the novel MB49-PSA transfectants. Tumor burden was evaluated by enzyme-linked immunosorbent assay measurement for PSA in urine and bladder tissues.

RESULTS

The MB49-PSA line actively secreted PSA in culture as well as in urine (18 to 2,062 pg/ml) depending on tumor mass. Immunofluorescence staining confirmed PSA expression in MB49-PSA derived orthotopic tumors. Urinary PSA production paralleled tumor growth and was detectable prior to the development of a palpable tumor. Although urinary PSA did not tightly correlate with tumor mass, all bladders (total of 16 tested) weighing 34 mg or greater (18 to 21 mg for age and sex matched normal bladders) showed 18 pg/ml or greater urinary PSA. In contrast, bladder tissue PSA correlated more with tumor mass in general and it was measurable even before the detection of urinary PSA. This MB49-PSA orthotopic tumor model also demonstrated its usefulness for evaluating the antibladder cancer agents gemcitabine and mitomycin.

CONCLUSIONS

This novel MB49-PSA line may serve as a useful tool for bladder cancer study because its growth inside the bladder can be noninvasively measured in living animals even during early stages of tumor growth.

Intravesical interleukin-12 gene therapy in an orthotopic bladder cancer model

OBJECTIVES

To evaluate the antitumor effect of intravesical cationic liposome-mediated interleukin-12 (IL-12) gene delivery in an orthotopic murine bladder cancer model, and to investigate the immunologic memory against tumors between IL-12 gene therapy and bacille Calmette-Guérin (BCG) therapy.

METHODS

Orthotopic murine bladder tumors were established by implanting 5 x 10(5) MBT-2 cells into the bladder of syngeneic female C3H mice. Intravesical IL-12 gene therapy was evaluated at varying doses: 0 microg (control) and 3, 5, and 10 microg (n = 8 for each group). Intravesical treatments were performed every 3 days and repeated six times beginning 5 days after tumor implantation. To compare the long-term, tumor-specific immunity between IL-12-treated mice (n = 18) and BCG-treated mice (n = 20), the animals surviving at day 60 and 10 new control mice were rechallenged with MBT-2 cells and received no additional treatment. On day 120, all surviving mice were killed and underwent necropsy.

RESULTS

In the IL-12 groups at doses of 0, 3, 5, and 10 microg, 0, 2, 3, and 3 mice survived, respectively. Mice in the 5-microg and 10-microg IL-12 groups survived significantly longer than did the control group. All mice cured by IL-12 treatment successfully rejected the rechallenge with MBT-2 cells; however, mice cured by BCG and the new control mice died of the rechallenged bladder tumors.

CONCLUSIONS

Intravesical IL-12 gene therapy, which induced long-lasting tumor-specific immunologic memory compared with BCG therapy, improved survival in an orthotopic bladder cancer model.

Molecular markers for predicting recurrence, progression and outcomes of bladder cancer (do the poster boys need new posters?)

PURPOSE OF REVIEW

Molecular markers for bladder cancer recurrence and progression continue to drive many research programmes. Translating the laboratory findings into the clinical environment where these markers are used in clinical decision making has proved problematic. In the clinical arena, stage and grade are still the main focus for decisions about patient management. There is however an evolution in bladder cancer research from single-marker/single-pathway research to a more global assessment of the tumour cell with DNA microarrays and proteomics.

RECENT FINDINGS

In the last year, DNA microarray assessment has revealed several interesting molecular markers such as p33ING1 and DEK. Parallel "conventional" single-pathway research has focused on new novel markers such as HER2/neu, survivin and matrix metalloproteinase 2 (MMP-2). Molecular markers that have a long-standing association with bladder cancer progression such as p53, E-cadherin and Ki-67 have been reviewed by both single-marker studies and by microarray studies and their status remains important.

SUMMARY

It is an exciting time in the molecular biology research of bladder cancer as the focus changes to assess the global genetic and protein expression within tumour cells. From such a wealth of information it is likely that molecular markers will make the translation from benchside to bedside.