Amplification of 2p has been observed as a recurrent alteration in diffuse large B-cell lymphoma (DLBCL). Whereas two candidate oncogenes, REL and BCL11A, have been investigated as targets for 2p amplification, the question remains as to whether the true target gene in the amplicon is REL, BCL11A or both. We previously identified frequent genomic gains of chromosomal 2p in 25 out of 99 DLBCL cases by means of genome-wide array comparative genomic hybridization (CGH). All of these 25 cases included recurrent copy number gain at 2p15-16. In the study presented here, cases were analyzed in greater detail by means of contig bacterial artificial chromosome (BAC) array CGH for the 4.5-Mb region at 2p15-16, which contained 33 BAC clones. We confined the minimal common region to 500-kb in length, where only the candidate oncogene REL, and not BCL11A, is located. Real-time quantitative PCR was carried out to investigate the correlation between genomic gain and expression. It showed a significant correlation for both genes, indicating that these two genes are common targets for the 2p15-16 amplicon. However, given the fact that REL is more frequently amplified than BCL11A, the REL gene may play a more important role than BCL11A in the pathogenesis of DLBCL. (Cancer Sci 2006; 97: 499-504) D iffuse large B cell lymphoma (DLBCL) is the most common type of malignant lymphoma, accounting for 30% of adult non-Hodgkin's lymphoma.(1) However, clinicopathological and genetic heterogeneities in this entity have suggested that further refinement of its subgroups is required.(2-5) Array-based comparative genomic hybridization (array-CGH) analysis is a powerful tool to identify genomic imbalances characteristic of distinct subgroups in DLBCL. (6,7) It has been useful not only for genome scanning of tumor cells but also for identification of novel oncogenes and suppressor genes. (8) We previously used a genome-wide array-CGH to identify a gain of 2p15 -16 in 25 out of 99 DLBCL cases.(7) Amplification at the 2p arm has been reported in B-cell lymphomas, such as DLBCL, (9)(10)(11)(12)(13)(14)(15) classical Hodgkin's lymphoma (cHL), (16,17) follicular lymphoma (FL) (18) and primary mediastinal B-cell lymphoma (PMBCL). (11,14,15) The two candidate genes, REL and BCL11A, have been mapped within this 2p15 -16 amplicon. The REL proto-oncogene, which encodes a member of the NF-κB transcription factor family, has frequently been found amplified in B-cell lymphomas. BCL11A, which is located quite near REL on chromosome 2p15 -16, is coamplified with REL in DLBCL and cHL. (12,15,16) In spite of numerous studies of this region, the question remains whether the target gene in the 2p15-16 amplification is REL, BCL11A, or both.For the study presented here, we carried out a contig array-CGH using glass slides on which contiguously ordered bacterial artificial chromosome (BAC) clones were spotted throughout 4.5 Mb of the 2p15 -16 genome to confine the minimal common region of amplification at 2p15 -16 in DLBCL cases. Real-time quantitative-polymerase ch...