Dissemination of MDAY-D2 cells and S1 transfectants to liver, spleen, and bone marrow.

Whole (A) liver and (C) spleen from mice killed 17 days after tail vein injection of control MDAY-D2 transfectants (empty vector). Multiple foci are visible in the liver, and the spleen is greatly enlarged and consists mainly of β-galactosidase–positive MDAY-D2 cells. Whole (B) liver and (D) spleen from mice injected with the S1 1.4 transfectant and killed after 17 days. No tumor cells can be detected. (E) A smear preparation of MDAY-D2 cells, stained with May-Grünwald Giemsa. Note the presence of granules (G). Histology of tissues in mice injected with control (empty vector) transfectants: (F) Liver. In the panel, LP indicates liver parenchyma; IT, intravascular tumor cells; and TF, tumor focus. (G) Spleen. RP indicates red pulp; WP, white pulp; and T, tumor cells. (H) Bone marrow. In mice injected with S1 transfected cells, the bone marrow is similarly affected, whereas the liver and spleen are tumor-free. SC indicates spinal cord; V, vertebral body; ID, intervertebral disc; and T, tumor cells. Note tumor infiltration into the spinal cord (top) and muscle (below).