Table 2.

Cell yields at 14 days in three serial assays with MTX treatment in the 3° assay

Assay	No. SA′ cells seeded	MTX, nm (3–6 day)	2% CS in 1°	10% CS in 1°	SA′ std. pass.	A′ std. pass.
			No. of cells (×10−5)
1°	105	0	6.28	20.1*
2°	105	0	55.1	35.3
3°	105	0	50.2	38.0	5.72†	5.93†
	105	200	6.16	3.80	4.00†	—
	103 (105)‡	0	20.1	12.1
	103 (105)‡	200	3.92	3.75

The procedure was the same as that of Table 1 but counts were made of the number of cells at the end of each assay. In addition, during the 3° assay, parallel 1° assays with cell counts were made of the standard passage of the SA′ and A′ cells. 

^*The high value for cell numbers in the 10% CS 1° assay results from the high serum concentration rather than transformation. Because 2% CS is used in all subsequent assays, high cell numbers reflect the extent of cell transformation. 

^†The assays of the standard passage SA′ were 1° assays but they were made in parallel with the 3° assay of SA′ cells. 

^‡10³ (10⁵): in the 3° serial assay of SA′ cells, 10³ were mixed with 10⁵ A′ cells, which served as a background for display of focus formation by the 3° SA′ cells.