Nature Reviews Urology | 2021
CDH12-expressing cell population predicts patient response to therapy
Abstract
A previously uncharacterized population of cells with an epithelial cell phenotype distinguished by high expression of cadherin 12 (CDH12), catenins and other epithelial markers has been discovered in high-grade muscle-invasive bladder cancer (MIBC). Patients with CDH12-enriched tumours had poor outcomes after receiving surgery with or with out neoadjuvant chemotherapy, but outcomes were improved for patients who received immunotherapy. Thus, assessment of CDH12 enrichment could help in treatment decision-making for patients with MIBC. “Neoadjuvant chemotherapy and immune checkpoint therapy have revolutionized bladder cancer management; however, determining which patients would benefit most from each type of therapy remains a major challenge,” says Dan Theodorescu, co-corresponding author of the paper, continuing “My hypothesis was that if we looked at the expression of individual cells within the tumour, we could define a second-generation bladder subtype architecture that would more effectively guide treatment and even perhaps find novel targets for therapies.” To this end, the research team used single-nuclei RNA sequencing (snSeq) with spatial transcriptomics and single-cell resolution spatial proteomic analysis to assess tissue samples from 25 patients with high-grade urothelial MIBC treated with surgery alone. “This process allowed us to look at different cell types in the tumour and study interactions between those cells,” says Simon Knott, co-corresponding author. snSeq analysis revealed substantial intertumoural heterogeneity in epithelial cell composition and unsupervised clustering of the epithelial compartment identified a distinct cell population that expressed CDH12. snSeq profiling of four histologically normal bladder samples showed that CDH12-enriched cells are a distinct population in healthy bladder epithelium. RNA velocity analysis showed that basal cells diverge along two differentiation paths: one travelling through the CDH12 population and one that skips it. Analysis of transcriptional similarities between CDH12 tumour cells and their non-malignant counterparts showed that the CDH12 cell population had an undifferentiated or dedifferentiated phenotype. In addition to stem-like characteristics, the CDH12 cells scored highly for neuroendocrine gene signatures. Application of gene signatures created from intervals along the identified differentiation paths to 259 samples of previously untreated high-grade urothelial MIBC tumours in TCGA and scoring of each inter val using single-sample gene set enrichment analysis showed that the interval score corresponding to the most undifferentiated phenotype predicted poor disease-specific survival (DSS). Further analysis showed CDH12 enrichment in basal or squamous and luminal infiltrated subtypes, which were enriched for CD8+ T cells. The CDH12 and macrophage signatures predicted poor DSS. Applying the signatures to bladder cancer samples before and after neoadjuvant chemotherapy showed that CDH12 score predicted overall survival (OS). CDH12 scores and expression of genes related to apoptosis and immune activation, including PDCD1LG2, tended to increase after chemotherapy in samples with an initially low score. Ligand–receptor interaction analysis revealed enriched interactions between the CDH12 cell population and fibroblasts. The strongest interaction between CDH12-enriched cells and CD8+ T cells was with ITGA1. Spatial transcriptomic analysis showed that areas enriched for CDH12 were also enriched for CD8+ T cells with markers of exhaustion. Analysis using a cellular niche detection algorithm showed that three niches were enriched for CDH12 epithelial cells, which had increased PDL1 expression; two of the niches were also enriched for CD8+ T cells, which had increased expression of CD49a, PD1 and LAG3. CDH12 levels predicted OS and the CDH12 score was associated with pathological response in postchemotherapy samples from the cohort of patients who received atezolizumab after failing to respond to chemotherapy in the IMvigor210 trial. “These high-CDH12 cells seem to paralyse the immune system by drawing T cells to them and then exhausting them,” explains Knott; “this protects the cancer cells from immune-mediated killing, but it does make them vulnerable to immune checkpoint blockade, which re-invigorates the nearby T cells and causes them to destroy the cancer.” These results seem to improve predictions based on current bladder subtypes and provide a potential method of stratifying patients with MIBC to optimal available therapy.