Deciphering clonal evolution and dissemination of Multiple Myeloma cells in vivo

Clonal evolution drives tumor progression, dissemination and relapse in cancer, and dissemination or metastasis of the tumor cells from primary site to other organs is the leading cause of death for cancer patients. This multi-stage process requires tumor cells to survive in the circulation, extravasate at distant sites, then colonization. The whole process involves contributions from both the tumor cells and microenvironment. Here we developed and applied a clonal tracking ‘rainbow’ system into a tumor dissemination xenograft mouse model (SCID-mu) to study the clonal behaviors with the presence of a bone marrow environment showing that only a few subclones successfully remodeled by BM environment can exit the primary site and further colonize in distant tissues. RNA-sequencing results of primary and disseminated MM tumor cells revealed a metastatic signature, which is sequentially activated during human MM progression and significantly associated with overall survival when evaluated against a public patient dataset suggesting SCID-mu model characterizes MM dissemination phenotypically and mechanistically. To explore the underlying molecular mechanisms that contribute to tumor metastasis, we performed RNA sequencing on three human cell lines MM.1S, IM9 and OPM2 that were harvested from primary bone chips and metastatic BM using SCID-mu xenograft model.