Cell-of-Origin Subtyping Diffuse Large B-Cell Lymphoma (DLCBL) by Using a 32-Gene Expression Assay in Formalin-Fixed Paraffin-Embedded Tissues

Objection: To evaluate a qPCR-based 32-gene expression assay to determine the cell-of-origin (COO) of diffuse large B-cell lymphoma (DLBCL) with formalin-fixed paraffin-embedded (FFPE) tissue. Methods: The most established subtyping algorithm, the COO model, categorizes DLBCL into activated B-cell (ABC) and germinal center B-cell (GCB)-like subgroups through gene expression profiling. Biopsy of DLBCL patients with paired FFPE and fresh frozen tissue were collected to assign COO based on the immunohistochemistry (IHC) algorithm (Han’s algorithm), qPCR-based 32-gene expression assay (DLBCL-COO assay) and global gene expression profiling with RNA-seq. Results: The DLBCL-COO assay demonstrated a significantly superior concordance of COO determination with the “gold standard” RNA-seq, comparing with the IHC assignment with Han’s algorithm (91.9% versus 77.5%; P = 0.005). Furthermore, overall survival of GCB patients defined by DLBCL-COO assay was superior significantly towards the ABC patients (Figure 2B, P = 0.023). This effect was not seen when tumors were classified by IHC algorithm. Conclusions: The DLBCL-COO assay provides flexibility and accuracy in DLBCL subtype characterization. These subtype distinctions should help guiding prognostic and therapeutic options for the patients in our daily practice. RNA-seq results of 111 DLBCL specimens were generated by paired-end sequencing on Illumina NovaSeq 6000 system