A subpopulation of SCC-13 cells grow as spheroids.

<p><b>A</b> SCC-13 monolayer cultures, maintained in growth medium, were harvested and plated at 40,000 cells per 9.5 cm² in poly-HEMA coated dishes or in standard tissue culture plates and grown in spheroid medium. Monolayer and P1 spheroid cultures were monitored for growth. The bars = 50 μm. <b>B</b> SCC-13 spheroid growth rate. SCC-13 cells were plated on poly-HEMA coated dishes and the diameter of P1 spheroids was monitored for 0 - 9 d. The values are mean <u>+</u> SEM, n = 3. <b>C</b> Spheroids are formed from a subset of SCC-13 cells. SCC-13 cells (40,000 single cells) were plated on poly-HEMA coated dishes and the total number of P1 spheroids was monitored for 0 - 10 d. Care was taken to assure that spheroid formation was not due to cell aggregation. A small percentage of cells (0.15%) are able to form spheroids. The values are mean <u>+</u> SEM, n = 4. The asterisks indicate a significant increase in spheroid number as compared to the day 2 data point (p < 0.05). <b>D</b> Selection of spheroid-forming cells. SCC-13 monolayer cultures were dissociated and plated into 96 well non-attachment plates at one cell per well. At the indicated times after plating, the cells were photographed. The upper panel shows on of the 0.15% of cells that survived and formed a spheroid. The bottom panel shows one of the non-surviving cells undergoing cell death.