Cancer Stem Cell-Associated Marker Expression in Chemotherapy-Treated Wilms Tumour

BackgroundWilms tumour (WT) relapse occurs more frequently in patients with blastemal-type WTs. The presence of cancer stem cells (CSCs) is linked to tumour survival and relapse, and CSCs may be found in greater numbers in blastemal cell foci. CSC-associated phenotypes have been described in untreated WT, but their persistence, organisation and relevance after neoadjuvant chemotherapy is unknown. MethodsWe analysed 23 formalin-fixed paraffin-embedded blocks from 18 chemotherapy-treated patients where WTs were enriched for viable blastema, using human fetal kidney as developmental control. Immunohistochemistry and -fluorescence analysis determined progenitor (PAX2, SIX2, CITED1) and CSC-associated (NCAM, ALDH1, CD133) marker expression. We qualitatively and semi-quantitatively evaluated spatial expression patterns and co-localisation across tumour compartments. ResultsPAX2 and SIX2 were co-expressed in blastema in most cases (15/18), with PAX2 expression higher at the periphery of blastemal foci and SIX2 expression found uniformly in central aspects. CITED1 expression was also associated with SIX2 in blastema tissues (14/18). NCAM was blastema-enriched (15/18) with higher central intensity, frequently adjacent to PAX2-expressing peripheral zones. ALDH1 expression was present across blastema and epithelium while NCAM-, ALDH1-double-positive cells were rarely observed (4/18). CD133 expression was less commonly seen (2/18), localising near epithelial/nephrogenic structures. ConclusionsAfter neoadjuvant chemotherapy, WT blastema retained overlapping but non-identical progenitor/CSC-associated marker landscapes with reproducible peripheral-centre gradients. These spatial arrangements suggest a blastemal niche for CSCs that may sustain a therapy-resistant state. Our analysis provides the foundation for future functional validation and molecular profiling to define key lineage relationships and therapeutic vulnerabilities in post-chemotherapy WT. [250/250 words]