Fig. 1.

Tumor cell lines isolated from both symptomatic and asymptomatic mice form tumors subcutaneously and intracranially and maintain the growth characteristics of their tumor grade. Tumor lines are isolated by cutting the dissected brain along the sagittal plane (A=anterior; P=posterior), fixing one half for histology, and dividing the other half into culture wells based on brain location (A). K1861-10 and 1410-4 are grade II astrocytomas (see Supplemental Fig. S1 for histological sections of primary tumors) and grow more slowly than the KR158 grade III anaplastic astrocytoma line (B) over a 5-week time frame. Four grade III lines (1395, K1492, K5001, and KR158) and 3 grade II lines (1410, K1861, and K4622) were injected subcutaneously, and the resulting tumor measurements over 3 weeks were averaged for grade III and grade II, showing significant differences in tumor growth (C) (Wilcoxon matched-pairs test, P=.031). KR158 cells on the inbred C57BL/6J background grow intracranially in both C57BL/6J (D) and immunocompromised (E) mouse brains.