Fig. 1

Repeated implantation of lung cancer cells potentiates their brain colonization ability. A Establishment of brain-colonized lung cancer cells. A549 human lung cancer cells (M0 cells) were injected into the brain of a mouse via the carotid artery. After 60 days, brain-colonized tumor was isolated and dissociated into single cells (M1 cells). Cultured and expanded M1 cells were re-injected into the brain. The second-round brain-colonized tumor was isolated and dissociated into single cells, which were expanded to establish M2 cells. B Cell morphology of M0 and M2 cells. Representative phase-contrast and fluorescence microscopic images of M0 and M2 cells. Cells were stained with phalloidin conjugated to Alexa 594 (red) and DAPI (blue). C In vivo bioluminescence images of athymic nude mice injected with M0 and M2 cells. M0 and M2 cells were injected into brains of BALB/c nude mice via carotid arteries. Brain-colonized tumors were visualized by bioluminescence imaging at 30, 44, and 58 days after injection. The graph denotes average radiance measured by using bioluminescence imaging