Clonal Complexity Defines Distinct Tumor‐Intrinsic Biology and Prognosis in Diffuse Large B‐Cell Lymphoma

BACKGROUND: Intratumor heterogeneity (ITH), characterized by the coexistence of genetically distinct subclones within a tumor, has been associated with adverse clinical outcomes in various cancers. However, the clinical and biological implications of ITH in diffuse large B-cell lymphoma (DLBCL) are still incompletely understood. MATERIALS & METHODS: In this study, we applied a SNP-array-based approach to assess the clonal complexity in formalin-fixed, paraffin-embedded tumor specimens obtained from newly diagnosed patients with advanced-stage DLBCL (n = 74) by calculating the clonal composition (CC) number. RSEULTS: Patients with Poly-CC tumors (CC ≥ 1), which accounted for 79.7% of the cases, had a 5-year event-free survival rate of 38.9%, compared with 69.1% in those with Mono-CC tumors (CC = 0) (Log-rank p = 0.0520). This association reached statistical significance in the activated B-cell (ABC) subtype (n = 35, Log-rank p = 0.0450) but not in the germinal center B-cell (GCB) subtype (n = 30, Log-rank p = 0.910). Gene set enrichment analysis revealed upregulation of cell cycle-related pathways in Poly-CC tumors, consistent with the significantly higher Ki-67 positivity rate than in Mono-CC tumors, as confirmed by immunohistochemistry (p = 0.00227). Within the ABC subtype, Poly-CC (Poly-ABC) tumors exhibited more differentiated transcriptional states and enrichment of IRF4-associated gene signatures as compared with Mono-CC (Mono-ABC) tumors. Conversely, IFN-γ and IFN-α response pathways and the IL-6/JAK-STAT3 signaling pathway were markedly suppressed in the Poly-ABC tumors. Furthermore, Poly-ABC tumors carried a significantly higher number of pathogenic mutations as compared with Mono-ABC tumors (p = 0.0147). CONCLUSION: These results suggest that clonal complexity captures tumor-intrinsic features and biological diversity in DLBCL, especially in the ABC subtype, offering novel insights into the disease pathogenesis.