Spatial profiling of non-muscle invasive bladder cancer (NMIBC) tumors reveals distinct molecular signatures predictive of response to pembrolizumab, offering insights into patient stratification and treatment optimization. The study, published in PMC, compared spatial transcriptomic data from patients treated with intravenous pembrolizumab monotherapy to those receiving intravesical BCG plus pembrolizumab.
Inflammatory Tumor Microenvironment Predicts Pembrolizumab Response
Researchers analyzed PanCK+ tumor segments and PanCK- stromal segments to identify predictive markers. Pretreatment tumor segments from responders to intravenous pembrolizumab showed elevated levels of claudin-low and squamous differentiation markers, along with upregulation of genes related to IFN-α and IFN-γ response, TNF-alpha signaling, and the IL6-JAK-STAT signaling pathways. This suggests that a heightened inflammatory tumor epithelium before treatment may enhance responsiveness to pembrolizumab.
In contrast, PanCK+ segments from non-responders exhibited elevated markers of p53 pathway genes, as well as estrogen response. Applying previously identified gene signatures from muscle-invasive bladder cancer (MIBC), researchers found that Cluster1-MIBC-CPI signatures, associated with resistance to pembrolizumab, were upregulated in pretreatment PanCK+ segments from non-responders. Conversely, Cluster3 and Cluster2-MIBC-CPI signatures, linked to immune infiltration and favorable response to immunotherapy, were upregulated in pretreatment PanCK+ segments from responders.
Dynamic Changes Post-Treatment
Longitudinal analysis of specimens collected pre- and post-therapy revealed that responsive tumors exhibited a net increase in inflammation-related pathways after pembrolizumab treatment. Non-responsive tumors, however, upregulated cell cycle gene sets such as G2M checkpoint and E2F targets.
Stromal Features and Immune Cell Infiltration
Analysis of the tumor microenvironment (TME) showed that pretreatment TME AOIs from responders had elevated levels of neutrophils, T cells, and NK cells compared to non-responders. Additionally, exhaustion markers were elevated in the pretreatment stromal compartment from responders. These findings were further validated in a proteomics digital spatial profiling dataset of muscle invasive tumors treated with neo-adjuvant pembrolizumab (PURE-01 study), where complete responders had elevated levels of cytotoxic T cell marker CD8, immune checkpoint markers LAG3, Tim-3, and PD-L1.
Comparison of Response Strategies
Comparing urothelial gene expression profiles between intravesical pembrolizumab and BCG versus intravenous pembrolizumab, the study found that responders to the combination intravesical therapy exhibited low levels of inflammation in the PanCK+ segments, whereas responders to the intravenous pembrolizumab monotherapy showed elevated levels of inflammation in the pretreatment PanCK+ segments. Responders in both cohorts exhibited elevated levels of immune infiltration in the stroma.
These findings suggest that inflamed tumor segments might benefit more from intravenous pembrolizumab, while non-inflamed BCG unresponsive tumors might be better candidates for treatment with a combination therapy of BCG and pembrolizumab.
