A Novel B-cell Line (U-2932) Established from a Patient with Diffuse Large B-cell Lymphoma Following Hodgkin Lymphoma

Abstract

Little is known about mechanisms leading to secondary non-Hodgkin lymphomas (NHL) in patients treated for Hodgkin lymphoma (HL). Our aim was to characterise in detail a cell line derived from a diffuse large B-cell lymphoma (DLBCL) that had developed in a patient with relapsing HL. The cell line U-2932 was established from ascites in a patient suffering from DLBCL previously treated for HL with multiple chemotherapy regimens. Characterisation was based on morphology, immunophenotype, Epstein-Barr virus (EBV)-status, IgH gene rearrangement status, tumourigenicity, p53 sequencing, and immunohistochemical expression of p53, BCL-2 and BCL-6. The karyotype was investigated using G-banding, comparative genomic hybridisation (CGH) and spectral karyotype (SKY) analysis. This cell line shows typical morphological features of a DLBCL and grows as colonies in nude mice. It expresses a B-cell phenotype with a somatically hypermutated V H 4-39 gene and is negative for EBV. The origin of U-2932 was confirmed by demonstrating an identical V H 4 rearrangement in ascites from the patient. A point mutation of the tumour-suppressor gene p53 was detected in amino acid position 176 and immunohistochemical over-expression of the p53 protein was also demonstrated. U-2932 carries a complex karyotype including high-level amplifications of the chromosomal bands 18q21 and 3q27 and expresses aberrant BCL-2 and BCL-6 immunohistochemically. We were unable to investigate the clonal relationship between the original HL and U-2932. In conclusion, U-2932 is a unique B cell line established from a patient suffering from HL followed by NHL. Overexpression of BCL-2, BCL-6 and p53 may play a role in the tumourigenesis and drug resistance. This cell line may become a useful tool to better understand the mechanisms responsible for development of secondary NHL in patients treated for HL.