Tumor dormancy in a murine B cell lymphoma

Tumor dormancy has been well recognized clinically (^1-5) but there is a paucity of experimental studies (^6-14) concerning this important aspect of host-tumor interaction. Early in our investigations of a murine lymphoma/1eukemia (BCL¹) we encountered dormancy. BCL¹ was the first B cell lymphoma described in mice (¹⁵). It arose spontaneously in a two-year old BALB/c mouse and is characterized by early and massive enlargement of the spleen followed later by leukemia and infiltration of the liver. The clinical characteristics of BCL¹ resemble the prolymphocytic form of chronic lymphocytic leukemia in humans (¹⁶). The tumor cells express IgMλ and IgDλ; these two isotypes share a common idiotype (Id) which has been defined both serologically and by sequence analysis (¹⁷). This is an attractive model for the study of dormancy because the immunoglobulin Id is a clonal marker; the DNA VH region gene rearrangements will facilitate detection of minimal disease by polymerase chain reaction; the tumor grows rapidly and primarily in the spleen so that tumor growth can be followed by palpation; and tumor cells can also be quantified by both Id-analysis and transfer of graded number of splenocytes from tumor bearing animals to syngeneic recipients. A single BCL1 cell can transfer tumor to a naive animal (¹⁶).