Extended data table 3.

Treatment with the anti-oxidant N-acetyl-cysteine increased tumour formation by intravenously transplanted melanoma cells.Limiting dilution analysis of tumour formation by intravenously transplanted efficiently metastasizing (a, M405, M481, UT10) or inefficiently metastasizing (b, M528 and M597) melanoma cells. In half the mice, the cells were pre-treated with NAC prior to transplantation and the mice were maintained on water supplemented with NAC after transplantation (n=5 mice/treatment/melanoma for a total of 110 mice in 5 independent experiments). Statistical significance was assessed by a chi-square test using ELDA software⁴⁶

a
Efficient Metastasizers
		Cell Dose	Mice Injected	Mice that formed tumours	Frequency of tumour-forming cells
Total	With NAC	1000	15	13	1/443	*
		100	15	4		*
	Without NAC	1000	15	3	1/4983	*
		100	15	0		*

b
Inefficient Metastasizers
		Cell Dose	Mice Injected	Mice that formed tumours	Frequency of tumour-forming cells
Total	With NAC	10000	5	2	1/16157
		1000	10	1
		100	10	0
	Without NAC	10000	5	0	-
		1000	10	0
		100	10	0

^****p<0.00005.