EXPRESSION OF L1 CELL-ADHESION MOLECULE IS ASSOCIATED WITH LYMPHOMA GROWTH AND METASTASIS

The cell adhesion molecule (CAM) L1 is involved in homotypic and heter otypic adhesion between neural cells. It has recently also been identi fied on leucocytes. We have investigated the expression of L1 on hemat opoietic tumor cell lines and found that several tumors including the ESb-MP lymphoma are positive for L1. A potential role for L1 in sponta neous metastasis formation was examined using these cells. From wild-t ype (wt) L1high lymphoma cells we selected by a fluorescence-activated cell sorter (FACS) stable L1low expression variants. Syngeneic DBA/2 mice injected subcutaneously with L1low clones showed faster primary t umor growth, developed visceral metastases significantly faster and di ed earlier than animals carrying L1high wt cells. L1high revertants fr om the L1low variants showed again a reduced metastatic capacity and a malignancy similar to the wt cells. Expression of L1 on the tumor var iants and revertants correlated directly with their homotypic aggregat ion behaviour in vitro. L1 expression correlated negatively with metas tatic capacity. These results suggest that L1 molecules may contribute to the overall malignant potential of the lymphoma cells, presumably by interfering with cell-cell interactions critical for tumor growth a nd dissemination.