Investigating the STING Pathway to Explain Mechanisms of BCG Failures in Non-Muscle Invasive Bladder Cancer: Prognostic and Therapeutic Implications

Abstract

Background: Intravesical Bacillus Calmette Guerin (BCG) has been the gold standard immunotherapy to treat high risk non-muscle invasive bladder cancer (NMIBC) for over 40 years. Attenuation of Mycobacterium bovis for clinical use as BCG results in loss of its ability to activate the "Stimulator of Interferon Genes" (STING) pathway and potentially limits local anti-tumor immune activity and subsequent BCG responsiveness due to reduced induction of the immune cell recruiting chemokines primarily, CXCL10. We conducted the current study to determine the potential of STING pathway agonist in synergizing with BCG to enhance chemokine induction. Methods: The TICE strain of BCG (OncoTICE) was used in combination with STING agonist to determine STING pathway activation and CXCL10 production in THP-1 monocytic cell line, THP-1 defNLRP3, THP-1 dual STING knock out cells, RT112 bladder cancer cells and primary bladder epithelial cells. NanoString platform-based gene expression profiling and multiplex cytokine analysis were performed to determine induction of interferon associated genes and secreted cytokines. Results: Activation of cytosolic pattern recognition receptor and downstream IFN1 pathways demonstrated synergistic activation of STING pathway enhanced BCG induced inflammasome and STING pathway gene expression in monocytes and bladder cancer cells. The significant differences in CXCL10, CCL5, IL-8 and MIP-1a/1b amongst the knockout cell lines confirm the convergence of these pathways following combination treatment with BCG and STING agonist. Conclusions: Findings from our study are the first evidence indicating that STING pathway activators are promising new innate immune modulators with a potential to synergize with BCG therapy in the treatment of NMIBC.

100 years of Bacillus Calmette–Guérin immunotherapy: from cattle to COVID-19

“…Thus, STING agonists have the potential to induce an anti-tumour immune response. Studies have evaluated the effect of BCG in combination with a STING agonist in cell-line models representing human monocytes, the bladder cancer cell line RT112 and primary bladder epithelial cells 139 . They showed a >20-fold increase in immune cell recruiting chemokines including CXCL10 as a result of synergistic effect of BCG and the STING agonist 139 .…”

“…Studies have evaluated the effect of BCG in combination with a STING agonist in cell-line models representing human monocytes, the bladder cancer cell line RT112 and primary bladder epithelial cells 139 . They showed a >20-fold increase in immune cell recruiting chemokines including CXCL10 as a result of synergistic effect of BCG and the STING agonist 139 . In another study, use of a recombinant BCG strain overexpressing a STING agonist stimulated epigenetic changes that promoted enhanced anti-tumour immunity compared with wild-type BCG in rat NMIBC tumour models 140 .…”

Assembling a network to promote translational bladder cancer research in Canada

“…Peter Black (University of British Columbia) presented opportunities to join forces and leverage Canadian strengths in bladder cancer translational research. He noted Canadian research capabilities, including advanced in vivo modelling, 5 genomics infrastructure, 6,7 liquid biopsy programs, 8 expertise in tumor immunology, [9][10][11][12][13][14] and epigenetics, 15 and established biospecimen repositories, 16 as well as a strong track record of linking these translational resources with investigatorinitiated trials. 17,18 The growth in bladder cancer research in Canada is clearly evident from pioneering new research findings and a growing cohort of Canadian researchers with a natural inclination to collaborate.…”

BCG vaccine and COVID-19: implications for infection prophylaxis and cancer immunotherapy

“…The loss of early secretory antigenic target secretion system-1 (ESX-1), one of the immunodominant antigens, as a result of attenuation for vaccine preparation, impairs the ability of BCG to activate the cGAS-STING/ IRF3, RIG/MAVS/IRF7 cytosolic nucleic acid sensing pathways. 11 As such, there is minimal IFN-β production, while some protection is imparted through cytokine induction and downstream immunological effects via NLRP3 inflammasome activation within macrophages, dendritic cells and epithelial cells. 11 To compensate for this IFN-1 activation defect, several recombinant versions of BCG have been generated.…”

“…11 As such, there is minimal IFN-β production, while some protection is imparted through cytokine induction and downstream immunological effects via NLRP3 inflammasome activation within macrophages, dendritic cells and epithelial cells. 11 To compensate for this IFN-1 activation defect, several recombinant versions of BCG have been generated. VPM1002 is a promising recombinant BCG that activates the AIM2 inflammasome and the STING pathway and has also been demonstrated to impart significantly higher protection over conventional BCG in phase I and II trials.…”