Establishment of a primary effusion lymphoma cell line (RM-P1) and in vivo growth system using SCID mice

Primary effusion lymphoma (PEL) is recognized as a unique lymphoma entity, which occurs exclusively in body cavities as a serous lymphomatous effusion without tumor formation or organ infiltration. We established a cell line of B-cell origin from a pericardial effusion of a 63-year-old Japanese PEL patient who did not have human immunodeficiency virus infection. This PEL cell line had human herpesvirus-8 (HHV-8) and Epstein-Barr virus (EBV) infection. We named this cell line RM-P1. This cell line showed complex chromosomal abnormalities that could not be identified by G-banding. However, spectral karyotyping analysis determined the origin and organization of all unidentified chromosomal abnormalities. When inoculated into the peritoneal cavity of 8 severe combined immunodeficiency (SCID) mice depleted of natural killer cells, RM-P1 cells induced solid tumor with ascites in all animals tested. These tumor and ascitic cells had the same immunogenotypic features as those of the original RM-P1. These 2 types of cells were positive for both HHV-8 and EBV as demonstrated using polymerase chain reaction. Fluorescence-activated cell sorting analyses showed that neither tumors nor ascitic cells grown in SCID mice expressed leukocyte function-associated antigen (LFA)-1alpha (CD11a), LFA-1lbeta (CD18), LFA-2 (CD2), LFA-3 (CD58), intercellular adhesion molecule (ICAM)-1 (CD54), ICAM-2 (CD102), ICAM-3 (CD50), or leukocyte endothelial adhesion molecule (LECAM)-1 (CD62L), suggesting that these cytoadhesion molecules are not involved in tumor formation of RM-P1 cells in vivo. The establishment of the RM-P1 cell line and the animal model of PEL may provide insights for understanding the relationship between these viruses and PEL and for understand the mechanism for PEL.