(UroToday.com) The 2024 Bladder Cancer Advocacy Network (BCAN) Bladder Cancer Think Tank held in San Diego, CA was host to a BCAN 2023 Patient Centered Clinical Young Investigator Awardee session. Dr. Kathryn Gessner presented the results of a study dissecting the impact of E-cadherin loss on the immune microenvironment and response to immune checkpoint blockade in plasmacytoid urothelial carcinoma.
Plasmacytoid urothelial carcinoma is a rare and aggressive histologic subtype of bladder cancer that demonstrates “"dyscohesive tumor cells with scant cytoplasm and eccentric nuclei that resemble plasma cells". These tumors demonstrate poor response to standard chemotherapy, and patients have lower median overall survivals compared to risk- and stage-matched conventional urothelial carcinoma patients.
The ’canonical’ molecular alteration in plasmacytoid urothelial carcinomas is E-cadherin loss. Limited molecular studies on plasmacytoid urothelial carcinomas have demonstrated Cadherin-1 (CDH1) mutations in 40–84% of patients and CDH1 promoter hypermethylation in a large proportion.2 These tumors are frequently identified as a mixed variant with conventional urothelial carcinoma and share additional mutations similar to conventional urothelial carcinoma (higher rates of RB1 and p53 mutations in plasmacytoid urothelial carcinoma). E-cadherin loss in these patients upregulates epithelial-to-mesenchymal transition, which has been associated with tumor immunosuppression and changes in immune microenvironment in other solid tumors.
How does E-cadherin loss impact the tumor microenvironment in plasmacytoid urothelial carcinoma? To address this, Dr. Gessner and colleagues utilized the 10X Xenium Platform for Spatial Transcriptomics. This performs spatial transcriptomic analysis of 100–5000 genes at single cell resolution via fluorescent probe-based detection of RNA transcripts on FFPE tissue. This allows for precise transcript localization, cell type mapping, and neighborhood analysis.
Dr. Gessner’s team identified a cohort of 27 patients with archival FFPE plasmacytoid urothelial carcinoma tissue housed at The University of North Carolina. The histology ranged from ‘focal’ plasmacytoid urothelial carcinoma to 100% plasmacytoid urothelial carcinoma. They performed E-cadherin immunohistochemistry on all tissue, and they then selected 3 plasmacytoid and one conventional urothelial carcinoma for their initial pilot study.
Using the 10X multi-tissue + cancer panel, they identified 377 genes, of which 100 were included in a custom bladder cancer panel.
They identified almost 26.5 million high-quality decoded transcripts in 321 thousand cells, with a median of 43 transcripts/cell.
They were able to map 10 unique cell type clusters across plasmacytoid urothelial carcinoma.
Three unique urothelial cell clusters were identified: urothelial 1, urothelial 2, and plasmacytoid urothelial carcinoma:
Next, Dr. Gessner and colleagues attempted to address the following two questions:
- What gene expression differences exist between conventional urothelial carcinoma cells and plasmacytoid urothelial carcinoma cells?
- How does E-cadherin loss alter the immune tumor microenvironment?
Plasmacytoid urothelial carcinoma cells demonstrated loss of CDH1 and increased SNAIL expression (epithelial-to-mesenchymal transition-related), compared to urothelial basal cells.
Plasmacytoid urothelial carcinoma demonstrated increased expression of epithelial-to-mesenchymal transition-related genes, including TWIST1, SNAI2, and TGF-beta.
Plasmacytoid urothelial carcinoma cells demonstrated higher overall gene expression, compared to conventional urothelial carcinoma:
- 54/477 genes upregulated in plasmacytoid
- 12/477 genes upregulated in conventional
DAVID Pathway Enrichment Analysis on genes upregulated in plasmacytoid urothelial carcinoma demonstrated the following results:
How does E-cadherin loss alter the immune tumor microenvironment? As seen in the bar graph below, plasmacytoid urothelial carcinoma cells have significantly higher macrophage infiltration.
Additionally, the plasmacytoid urothelial carcinoma region demonstrated increased PD-L1 expression:
Dr. Gessner concluded as follows:
- Spatial transcriptomics allows precise characterization of intratumoral heterogeneity within bladder cancer.
- Plasmacytoid histology is characterized by upregulation of epithelial-to-mesenchymal-related genes and signaling.
- The immune microenvironment differs between plasmacytoid and conventional urothelial carcinoma within the same tumor, which has possible therapeutic implications.
Presented by: Kathryn Gessner, MD, PhD, Assistant Professor, Department of Urology, University of North Carolina, Chapel Hill, NC
Written by: Rashid Sayyid, MD, MSc – Robotic Urologic Oncology Fellow at The University of Southern California, @rksayyid on Twitter during the 2024 BCAN Bladder Cancer Think Tank held in San Diego, CA between August 7th and 9th, 2024
References:
- Diamantopoulos LN, Khaki AR, Grivas P, et al. Plasmacytoid urothelial carcinoma: response to chemotherapy and oncologic outcomes. Bladder Cancer. 2020;6(1):71-81.
- Al-Ahmadie HA, Iyer G, Lee BH, et al. Frequent somatic CDH1 loss-of-function mutations in plasmacytoid variant bladder cancer. Nat Genet. 2016;48(4):356-8.