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

Abstract

Intravesical 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 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 to intravesical chemotherapy. Whole transcriptome expression profiling of post-treatment 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.

WITHDRAWN: Recombinant BCG overexpressing a STING agonist elicits trained immunity and improved antitumor efficacy in non-muscle invasive bladder cancer

“…S1b). To evaluate its NMIBC antitumor efficacy we tested BCG-disA-OE delivered intravesically in the rat N-methyl-N-nitrosourea (MNU) model of NMIBC [27][28][29] . In this model urothelial dysplasia develops at week 14 after the first intravesical instillation of MNU and by week 24 rats display a heterogeneous NIMBC including carcinoma-in-situ (CIS), papillary Ta, or higher-grade T1-T2 urothelial carcinoma with histopathologic and immunophenotypic features similar to those observed in human NMIBC (Fig.…”

“…For each section, Ki67 expression was scored as a percentage of positive cells in the urothelium. Dual stains for CD68/CD86 and CD68/CD206 were scored based on positive clusters of cells for each marker (0= no staining, rare isolated cells positive, 2 = clusters of up to 10 positive cells, 3= clusters of > 10 positive cells).In vivo experiments:Intravesical BCG treatment in carcinogen induced NMIBC rat model: The induction of urothelial cancer in rats and subsequent treatment of intravesical BCG were performed as previously described27 . Briefly, N-methyl-N-nitrosourea (MNU) instillations were given every other week for a total of 4 instillations.…”

“…Intravesical BCG treatment in carcinogen induced NMIBC rat model: The induction of urothelial cancer in rats and subsequent treatment of intravesical BCG were performed as previously described 27 . Briefly, N-methyl-N-nitrosourea (MNU) instillations were given every other…”

Predictive biomarkers for drug response in bladder cancer

“…One arena in which biomarkers have been evaluated is in predicting response to intravesical BCG therapy. Although the mechanism of BCG continues to be debated, BCG clearly induces an influx of both cytotoxic, and to a lesser extent memory, T cells into the tumor microenvironment, in addition to the recruitment of neutrophils and macrophages . This broad, non‐specific immune response has made the identification of single molecular biomarkers quite challenging, as the mechanisms of BCG efficacy and resistance are likely multifactorial.…”

“…Although the mechanism of BCG continues to be debated, BCG clearly induces an influx of both cytotoxic, and to a lesser extent memory, T cells into the tumor microenvironment, in addition to the recruitment of neutrophils and macrophages. [22][23][24] This broad, non-specific immune response has made the identification of single molecular biomarkers quite challenging, as the mechanisms of BCG efficacy and resistance are likely multifactorial. One effort to address this broad, non-specific immune response has been in the evaluation of urinary cytokines before and after intravesical BCG.…”