Spheroid-selected skin tumor cells retain properties during <i>in</i><i>vivo</i> growth.

<p><b>A</b> Morphology of tumors derived following injection of 100,000 spheroid-selected and non-selected (monolayer) cells after growth for four weeks. <b>B/C</b> Cells derived from spheroid-selected and non-selected tumors were dissociated and ability to form spheroids in culture was monitored. Spheroid formation is significantly greater for tumors formed from spheroid-selected cells. The values are mean <u>+</u> SEM, n = 4 independent tumors per group (p < 0.005). The bars = 100 μm. The photographs were taken after 10 d of spheroid growth. <b>D</b> Spheroid growth rate is identical for tumor cells derived from spheroid-selected and monolayer cells. Forty thousand cells, harvested from the tumors derived from spheroid-selected and non-selected cells, were plated in spheroid selection medium to monitor the rate of spheroid growth. Values are the mean <u>+</u> SEM (n = 4 independent tumors per group). No significant difference is observed in spheroid growth rate for cells derived from monolayer and spheroid tumors.