Association Between T Cell Exhaustion, Urinary Tumor DNA Levels, and BCG Failure in Bladder Cancer - Expert Commentary

Treatment for high-risk non-muscle invasive bladder cancer (NMIBC) typically includes intravesical administration of bacillus Calmette-Guérin (BCG) as a form of immunotherapy. BCG is thought to activate both innate and adaptive immune responses with anti-tumor effects.

However, chronic antigen stimulation eventually leads to a state of ‘exhaustion’ in T cells, during which inhibitory receptors are expressed, cytokine secretion drops, and reduced proliferation. Strandgaard et al. sought to identify factors associated with BCG failure in NMIBC.

The retrospective cohort consisted of 156 patients with NMIBC who had received at least five BCG instillations. The median time of follow-up after BCG treatment was 5.5 years. Urine samples were collected before and after treatment in a subset of patients (124 total, 66 were paired). Researchers conducted a proteomic analysis on the samples and found upregulation in various proteins after treatment, including CXCL9, CXCL11, CXCL10, PD1, and TRAIL. Protein changes after treatment also reflected immune system activation. Patients with high- grade recurrence had significantly higher levels of CD70 after treatment, which is known to inhibit T cell-mediated inflammation.

Strandgaard et al. subsequently classified patients according to the UROMOL2021 system. Most pre-BCG tumors were designated high-risk class 2a, while most post-BCG tumors were designated high-risk class 2b, representing the immune infiltration subtype. Patients with either of these subtypes had worse post-BCG high-grade recurrence-free survival. After BCG treatment, 43.6% of patients remained in or shifted to subtype 2b. RNA-sequencing data revealed that patients with post-BCG high-grade recurrence also had a higher total immune infiltration score after BCG. This recurrence was associated with a larger quantity of dendritic cells, mast cells, and exhausted CD8 T-cells post-BCG. In fact, all post-BCG tumors with high levels of CD8 T cell exhaustion were associated with recurrence. Moreover, these patients exhibited higher expression of immune inhibitory genes such as PD1, KLRG1, HAVCR2, CTLA4, and LAG3. Genomic analysis showed fewer insertions and deletions in tumors from patients who did not exhibit post-BCG high-grade recurrence than those who did.

The most frequent mutation was MUC4 in the post-BCG group with high T cell exhaustion and FGFR3 in the post-BCG group with low T cell exhaustion. Tumors with a high neoantigen load pre- BCG exhibited significantly higher T cell exhaustion post-BCG. Post-BCG urinary tumor- derived DNA levels were also significantly higher in the recurrence group and were associated with exhaustion status. Clearance of tumor-derived DNA levels was associated with better post-BCG recurrence-free survival. Researchers then used differentially expressed genes in the samples to generate a post-BCG exhaustion predictor. This scoring system distinguished patients with high post-BCG T cell exhaustion and lower high-grade recurrence-free survival.

This study provides evidence for the link between T-cell exhaustion and high-grade recurrence in NMIBC patients treated with BCG. The findings also point towards a potential benefit from monitoring urinary tumor-derived DNA levels to predict patient outcomes and alter management as needed. Moreover, combining BCG treatment with immunomodulators may be essential for avoiding T-cell exhaustion and maintaining anti-tumor activity.

Written by: Bishoy M. Faltas, MD, Director of Bladder Cancer Research, Englander Institute for Precision Medicine, Weill Cornell Medicine

References:

  1. Strandgaard T, Lindskrog SV, Nordentoft I, et al. Elevated T-cell Exhaustion and Urinary Tumor DNA Levels Are Associated with Bacillus Calmette-Guérin Failure in Patients with Non-muscle-invasive Bladder Cancer [published online ahead of print, 2022 Oct 6]. Eur Urol. 2022;S0302-2838(22)02636-7. doi:10.1016/j.eururo.2022.09.008

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