Integrative Multi-omics Guides PD-1 Blockade Therapy in the Rare and Aggressive Colorectal Adenosquamous Carcinoma

Colorectal adenosquamous carcinoma (CRASC) is a rare and aggressive malignancy without standardized treatment, posing a grave clinical challenge. Here, we performed integrative multi-omics analysis on the largest multicenter cohort to date, to delineate its molecular and spatial architecture. Whole-exome sequencing showed that adenocarcinoma (AC) and squamous cell carcinoma (SCC) components originate from a common ancestral clone, followed by lineage specific divergence, establishing CRASC as a unified evolutionary entity. Spatially resolved transcriptomics uncovers a compartmentalized ecosystem. SCC enriched regions were embedded in a fibroblast dense, metabolically active, and immune restrictive stroma, whereas AC niches form immunogenic hubs with enhanced antigen presentation and cytotoxic T cell engagement. Clinically, we provided proof-of-concept evidence that CRASC patients can achieve sustained progression-free survival following immunotherapy-based regimens in both adjuvant and neoadjuvant settings. Our findings redefine CRASC as a spatially organized, evolutionarily unified malignancy and establish spatial lineage architecture as a biomarker for CRASC immunotherapy selection.