Intravesical immunotherapy with bacillus Calmette-Guérin (BCG) has been used for nearly four decades to treat non-muscle-invasive bladder cancer. Despite treatment, a significant proportion of patients fails to respond and ultimately require more aggressive treatment. Early identification of high-risk patients who might not benefit from BCG treatment is critical, since delaying radical surgery definitely worsens patient outcome. Although the exact mechanism of action of BCG is not completely understood, it is now recognized that the antitumor effects of BCG are produced by the complex interplay between the direct effects on tumor cells by BCG infection and the host immune response. It is now well recognized that a competent immune system and functional T-cells subsets amongst other immune cells are required for response to BCG. Immune checkpoint molecules play a critical role in regulating T cell functionality after TCR/MHC signaling, to prevent bystander damage from unrestrained T-cell activity. Inhibitory T cell co-receptors, such as CTLA-4 and PD-1, cause T cell anergy and apoptosis, impeding anti-tumor immunity. Cancers use the PD-L1 pathway to inhibit immune responses by the ectopic expression of inhibitory ligands that regulate T cell activation. PD-L1 on bladder cancer cells is increasingly expressed with advancing local tumor stage, and a strong association has been described between PD-L1 overexpression and cancer progression, perhaps facilitating the eventual loss of BCG effectiveness over time. Whether the upregulation of PD-L1 expression in tumor tissues might be induced in response of BCG instillations, and whether it may contribute to unresponsiveness or relapse following BCG therapy represent the main aims of the present proposal. PD-L1 expression on circulating tumor cells through serial liquid biopsies will be also analysed as an hypothetical biomarker of treatment resistance.
The modalities of combination between BCG intravesical therapy and PD1/PD-L1 axis inhibitors that are currently being explored in early phase clinical trials might be suboptimal. Indeed, the inflammatory microenvironment that is generated locally after BCG instillations requires adequate time to be established and to trigger molecular events determinant for BCG failure. We envisage that alternative combination regimens with BCG and checkpoint inhibitors, such as an intermittent schedule, might better resemble the molecular immune-mediated background of BCG resistance and possibly delay the recurrence of disease. Several lines of evidence exist around the bidirectional crosstalk between PD-L1 expression and epithelial to mesenchymal transition, which has been increasingly recognized as a crucial event in cancer progression. We hypothesize that PD-L1 inhibitors might reverse the EMT program. If confirmed, we might anticipate that combining intravesical BCG and checkpoint inhibitors in NMIBC we might reduce the rate of progression to muscle invasive disease.
Results from this project could have major implications in NMIBC bladder cancer and potential therapeutic application.
Aim 1. If demonstrated, the upregulation of tumor PD-L1 expression at failure of BCG might be a step forward in the understanding of the mechanism of action of intravesical immunotherapy. This might support the use of combination therapy to maximize the efficacy of the current standard of care BCG, which could in turn markedly improve outcomes in patients with high-risk non-muscle invasive disease.
Aim 2. If confirmed, the ability to discriminate patients progressing to muscle invasive disease after BCG from those who will experience non-muscle invasive recurrence, through the evaluation of the concomitant expression of PD-L1 and EMT markers in TURBT specimens, might pave the way to the discovery of a new marker for risk stratification of NMIBC
Aim 3 There is a lot of excitement around checkpoint inhibitors, as we are seeing durable and rapid responses to these therapies across a broad range of tumor types. Nevertheless, we are still only getting responses in a minority of patients and the finding of reliable predictors of benefit seems unex-pectedly complex. Liquid biopsy, as a minimally invasive and easily repeatable analysis, might allow the real-time monitoring of PD-L1 status and overcome the intrinsic limits of tissue biopsy in the evaluation of a dynamic parameter such as PD-L1.
References
1) Kamat AM, Colombel M, Sundi D, Lamm D, Boehle A, Brausi M, Buckley R, Persad R, Palou J, Soloway M, Witjes JA. BCG-unresponsive non-muscle-invasive bladder cancer: recommendations from the IBCG. Nat Rev Urol. ;14(4):244-255 (2017).
2)Meeks JJ, Carneiro BA, Pai SG, Oberlin DT, Rademaker A, Fedorchak K, Balasubramanian S, Elvin J, Beaubier N, Giles FJ. Genomic characterization of high-risk non-muscle invasive bladder cancer. Oncotarget; 7(46):75176-75184 (2016)
3) Patel SG, Cohen A, Weiner AB, Steinberg GD. Intravesical therapy for bladder cancer.
Expert Opin Pharmacother. ;16(6):889-901(2015)
4) Redelman-Sidi G, Glickman MS, Bochner BH. The mechanism of action of BCG therapy for bladder cancer--a current perspective. Nat Rev Urol. ;11(3):153-62 (2014)
5)Dempsey, P.W., Vaidya, S.A., Cheng, G. The art of war: Innate and adaptive immune responses. Cell Mol Life Sci. 60, 2604-21 (2003).
6)Pardoll DM. The blockade of immune checkpoints in cancer immunotherapy. Nat Rev Cancer ;12:252-64 (2012)
7) Zhou TC, Sankin AI, Porcelli SA, Perlin DS, Schoenberg MP, Zang X.A review of the PD-1/PD-L1 checkpoint in bladder cancer: From mediator of immune escape to target for treatment. Urol Oncol. ;35(1):14-20 (2017)
8)Pichler R, Gruenbacher G, Culig Z, Brunner A, Fuchs D, Fritz J, Gander H, Rahm A, Thurnher M. Intratumoral Th2 predisposition combines with an increased Th1 functional phenotype in clinical response to intravesical BCG in bladder cancer.
Cancer Immunol Immunother. ;66(4):427-440 (2017)
9) Wu Y, Enting D, Rudman S, Chowdhury S. Immunotherapy for urothelial cancer: from BCG to checkpoint inhibitors and beyond.Expert Rev Anticancer Ther. ;15(5):509-23 (2015)
10)Raimondi C, Carpino G., Nicolazzo C, Gradilone A, Gianni W, Gaudio E, Cortesi E, Gazzaniga P 1.PD-L1 and epithelial-mesenchymal transition in circulating tumor cells from non-small cell lung cancer patients: a molecular shield to evade immune system? Oncoimmunology, in press (2017)
11)Nicolazzo C, Raimondi C, Mancini M, Caponnetto S, Gradilone A, Gandini O, Mastromartino M, Del Bene G, Prete A, Longo F, Cortesi E, Gazzaniga P.Monitoring PD-L1 positive circulating tumor cells in non-small cell lung cancer patients treated with the PD-1 inhibitor Nivolumab.Sci Rep. Aug 24;6:31726. doi: 10.1038/srep31726 (2016)