The 5T2 mouse multiple myeloma model: characterization of 5T2 cells within the bone marrow

The transplantable C57BL/KaLwRij mouse 5T2 multiple myeloma (MM) is a new animal model for studies on MM in man. Histological examination of the 5T2 MM cells revealed their morphological heterogeneity. In this study we investigated whether this heterogeneity reflects subpopulations of 5T2 MM cells with different biological properties. 5T2 MM bone marrow cells were separated according to their sedimentation velocity (s.v.). When intravenously injected into syngeneic recipient mice, cells with s.v. of 8 mm h-1 led to the development of detectable 5T2 MM after 6 weeks; in contrast, 18 weeks elapsed before the same result was achieved with cells of s.v. lower than 5 mm h-1. Flow cytometric analysis revealed that 5T2 MM cells had an aneuploid DNA content and that most cycling 5T2 MM cells were large, their s.v. rate exceeding 9 mm h-1. It was further demonstrated that about half of all aneuploid cells carried on their membrane the 5T2 MM idiotype. The majority of the idiotype-positive cells had s.v. rate exceeding 6.5 mm h-1 (16%-39%) or lower than 3 mm h-1 (16%-19%). The 5T2 MM was shown to contain subpopulations of cells of different size, proliferation capacity and expression of their membrane 5T2 idiotype; this, most likely reflects cells in different stages of differentiation. The mouse 5T2 MM corresponds also in this respect with MM in man.