Clonal drift of cell surface, melanogenic, and experimental metastatic properties of in vivo-selected, brain meninges-colonizing murine B16 melanoma.

Abstract

Abstract Using the B16 melanoma cell line B16-F1 of low lung colonization potential, sublines were selected for blood-borne implantation, survival, and growth in the brain by cycles of tumor cell injection, harvesting of brain surface tumor nodules, and in vitro tissue culture growth. After 14 sequential selections for brain colonization, subline B16-B14b was established which showed enhanced abilities to form brain tumor colonies compared to line B16-F1. The B16-B14b melanoma brain tumor colonies formed after i.v. tumor cell inoculations were located mainly in the cerebral arteries of the arachnoid tissue and grew generally in the blood vessels, invaded the vessel walls, and formed tumor foci in perivascular tissue. The subline B16-B14b was relatively stable in its brain colonization, growth, and other cellular properties. However, cell clones derived from subline B16-B14b were heterogeneous in their cellular properties (melanin contents, cell morphologies, and cell surface proteins) and also in their brain colonization abilities. In addition, the cell clones were also heterogeneous with respect to the stabilities of these in vitro and in vivo properties during growth in tissue culture. An equal mixture of three unstable B16-B14b clones was allowed to grow in tissue culture for approximately 30 passages, and the cell mixture was found to be stabilized in its brain colonization properties compared to the cell clones grown individually for a similar number of passages and mixed just prior to inoculation. Examination of exposed cell surface proteins by lactoperoxidase-catalyzed 125I iodination and sodium dodecyl sulfate:polyacrylamide slab gel electrophoresis autoradiography revealed increased exposures of a component with an approximate molecular weight of 90,000 on B16 sublines and clones with high brain colonization potentials. When the unstable B16-B14b clones were examined during tissue culture growth for the presence of the Mr 90,000 component, it was found to decrease in exposure as the clones lost their brain colonization abilities.