[Analysis of Tumorigenesis in Mice Transplanted with Different Multiple Myeloma Cell Lines]

To investigate the tumorigenicity of several multiple myeloma (MM) cell lines transplanted in mice without γ-ray irradiation and to construct the MM disease model to facilitate in vivo experiments.

NOD/SCID or NSG mice were subcutaneously or caudally transplanted with MM cell lines (LP-1, OPM2, RPMI 8226 and MOLP8), or cell lines with luciferase (RPMI-Luc-Puro, RPMI-Luc-mCherry and MOLP8-Luc-Puro). Tumor growth was observed by measuring the tumor size with a caliper. CD138⁺ tumor cells in peripheral blood were detected by flow cytometry. The free light chain in mouse serum was detected by immunofixation electrophoresis. Tumor type was identified by immunohistochemistry.

Twenty one NOD/SCID mice were subcutaneously transplanted with LP-1 cells or OPM2 cells respectively, and no tumors formed till 7 weeks after transplantation. Fifteen NOD/SCID mice subcutaneously transplanted with RPMI 8226 cells showed tumor formation one week later. As of 7 weeks, the rate of tumorigenesis was 80% (12/15). Serum λ light chain was detected and no CD138⁺ tumor cells were detected in peripheral blood. Two NOD/SCID mice each were subcutaneously transplanted with RPMI-Luc-Puro, RPMI-Luc-mcherry and MOLP8-Luc-Puro cells respectively. No tumor signal was detected through IVIS in RPMI-Luc-mcherry cells-transplanted mice. There was tumor signal at 1 week in RPMI-Luc-Puro and MOLP8-Luc-Puro cells-transplanted mice, the former disappeared at 2 weeks and the latter persisted more than 3 weeks. NSG mice subcutaneously transplanted with both cells persistently displayed the tumor signal. Neither NOD/SCID nor NSG mice transplanted with RPMI 8226, RPMI-Luc-Puro, RPMI-Luc-mcherry or MOLP8-Luc-Puro cells through tail vein developed the tumor signal. Only one NSG mice transplanted with MOLP8-Luc-Puro cells appeared transient tumor signal.

Unirradiated mice transplanted with MM cell lines tended to develop local tumor, and failed to develop disseminated tumor. The tumorigenicity of different cell lines is quite different and the vector transfection can reduce the tumorigenic ability. NSG mice with more severe immunodeficiency are more suitable for tumor growth.