Differential tumor growth of blood-borne B16 melanoma variants in cerebral dura mater is related to tumor-host cell reactions.

Intracarotid injection of B16-B14b or B16-B15b melanoma cells, previously established from B16-F1 melanoma by in vivo selection fourteen- or fifteen-times, respectively, for brain surface colonization, preferentially produced tumor nodules in mice at brain surface sites, most frequently in the dura mater, followed by the leptomeninges and cerebral cortex. There was a marked difference, however, in tumor growth at these sites using the two B16 sublines. Intracarotid injection of B16-B14b cells rarely produced visible tumors, whereas B16-B15b cells formed deeply pigmented tumors up to 7 mm in diameter in the brain menings of almost all mice examined. Histologic and electron microscopic investigation revealed that B16-B14b tumors evoked dramatic immunocyte cell infiltration and granulomatous reactions, while B16-B15b tumors were accompanied by much less tumor-host cell reactions. Splenectomy or laparotomy 1-2 weeks before or after intracarotid injection of B16-B14b cells dramatically enhanced tumor growth in the dura mater without extensive tumor-host cell reactions. The results suggest that the differential growth of B16-B14b and B16-B15b tumor cells in the cerebral dura mater is based, in part, on the abilities of these melanoma cells to elicit host cell reactions.