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Abstract Background Antitumor immune response of programmed cell death ligand (PD-L1) has shown clinical value not only in Hodgkin lymphoma and EBV-associated lymphomas but also in EBV-negative diffuse large B cell lymphoma (DLBCL) of non-germinal center B cell-like (non-GCB) subtype. Signal transducer and activator of transcription 3 (STAT3) is known to induce PD-L1 in immune cells and its activated form, phosphorylated STAT3 (pSTAT3), is also frequently expressed in non-GCB DLBCL. Herein, we investigated associations between PD-L1 expression/gene alteration, pSTAT3 expression and clinicopathologic variables in EBV-negative DLBCL. Methods In 107 cases of DLBCLs with non-GCB subtype (67%; 72/107), GCB subtype (25%; 27/107) and unclassifiable cases (8%; 8/107), we performed PD-L1 and pSTAT3 immunohistochemistry and fluorescence in situ hybridization for PD-L1 gene translocation and copy number gain/amplification. Results PD-L1 was expressed in tumor cells (PD-L1t) in 21% (23/107; 30% cutoff), immune cells (PD-L1i) in 36% (38/107; 20% cutoff), and pSTAT3 in tumor nuclei in 41% (44/107; 40% cutoff). PD-L1 gene alteration was observed in 10% (10/102) including translocation in 6% (6/102) and copy number gain/amplification in 4% (4/102). Non-GCB subtype was associated with PD-L1t and pSTAT3 (p = 0.006 and p = 0.042), and tended to have PD-L1 gene alteration (p = 0.058). Tumoral PD-L1 expression without gene alteration (PD-L1t+ GA−) correlated with pSTAT3-positive tumor cell proportions (%) (p = 0.033). In survival analysis, pSTAT3 expression independently predicted shorter PFS in total cohort (p = 0.017) and R-CHOP-treated group (p = 0.007), and in pSTAT3-negative R-CHOP-treated subset, PD-L1 expression in immune cells (PD-L1i) correlated with shorter PFS (p = 0.042). Conclusions Gene alteration and protein expression of PD-L1 and pSTAT3 expression were closely related in DLBCL and constituted features of non-GCB subtype. In addition to known clinical significance of pSTAT3, immune cell expression of PD-L1 (PD-L1i) had also clinical value in pSTAT3-dependent manner. These findings may provide an insight into immunotherapeutic strategy and risk stratification in DLBCL patients.

Abstract Background Diffuse large B cell lymphoma (DLBCL) contains heterogeneous subtypes with various molecular dysregulation at the gene, protein and microRNA levels. Compared with the GCB subtype, the non-germinal center B-like (non-GCB)/activated B cell-like (ABC) subtype exhibits frequent progression despite standard immunochemotherapy. We aimed to investigate the effects of miR-197 on the progression and chemosensitivity of DLBCL with respect to the GCB and non-GCB/ABC subtypes. Methods To screen distinctively expressed microRNAs, microRNA expression patterns were analyzed in 10 DLBCL cases by microarray chip assays. Using quantitative real-time polymerase chain reaction (qRT-PCR), associations between miR-197 expression levels and clinicopathologic variables were investigated in 51 DLBCL tissue samples. The effects of miR-197 on doxorubicin chemosensitivity were investigated using the OCI-Ly1 and SUDHL9 cell lines. Results MicroRNA expression profiling by hierarchical clustering revealed that miR-197 was one of the distinctively expressed microRNAs in DLBCL. Quantitative analysis using qRT-PCR revealed that miR-197 levels were not correlated with clinicopathologic variables, including the international prognostic index, but low miR-197 levels were significantly associated with lymphoma progression defined by refractoriness, relapse or death in the rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP)-treated subgroup (n = 43; p = 0.004). Among the three molecular groups, i.e., the GCB, non-GCB/miR-197low and non-GCB/miR-197high groups, progression was most frequently observed in the non-GCB/miR-197low group in the full cohort (p = 0.013) and the R-CHOP cohort (p = 0.008). In survival analysis, low miR-197 levels were independently predictive of shorter progression-free survival in the R-CHOP cohort (p = 0.031; HR = 27.9) and the non-GCB subgroup (p = 0.037; HR = 21.5) but not in the GCB subgroup. Using SUDHL9 (ABC type) and OCI-Ly1 (GCB type) cells, the effects of doxorubicin on reducing cell viability were enhanced by miR-197 transfection. In apoptosis assays, miR-197 transfection enhanced doxorubicin-induced apoptosis in SUDHL9 cells but not in OCI-Ly1 cells, suggesting a chemosensitizing effect of miR-197 in ABC DLBCL. Conclusions These results suggest the role of miR-197 as a biomarker with potential therapeutic implications.