Table 4.

Methylation frequency (%) of SFRP CpG islands at different cutaneous SCC pathological levels

Gene	CpG Site	Stage I		Stage II		Stage III		H	P-value
		N	$\overline{x}\pm s$	N	$\overline{x}\pm s$	N	$\overline{x}\pm s$
SFRP1	CpG1_5	0	0.4012 ± 0.098	0	0.4521 ± 0.115	9	0.4952 ± 0.109	6.157	0.024*
	CpG1_7	9	0.4011 ± 0.134	6	0.4811 ± 0.024	2	0.5121 ± 0.124	5.103	0.031
	CpG2_1	7	0.4141 ± 0.19	0	0.4267 ± 0.314	2	0.4013 ± 0.217	2.136	0.021
	CpG2_8	5	0.4231 ± 0.824	7	0.4501 ± 0.224	4	0.5011 ± 0.523	8.514	0.017
SFRP2	CpG1_5	44	0.3329 ± 0.101	29	0.3796 ± 0.170	19	0.4241 ± 0.183	6.142	0.015
	CpG2_1	47	0.4094 ± 0.036	48	0.4367 ± 0.316	17	0.4713 ± 0.107	6.136	0.023
	CpG2_3.4	55	0.4017 ± 0.098	42	0.4406 ± 0.194	18	0.4891 ± 0.153	5.218	0.015
SFRP4	CpG1_3	2	0.3029 ± 0.089	3	0.3496 ± 0.012	2	0.3867 ± 0.083	7.158	0.009
	CpG2_2	9	0.2994 ± 0.037	2	0.3367 ± 0.016	5	0.4113 ± 0.086	7.156	0.023
SFRP5	CpG1_5	40	0.3014 ± 0.052	33	0.3834 ± 0.021	18	0.4345 ± 0.037	5.54	0.031
	CpG2_1	32	0.2941 ± 0.098	19	0.3167 ± 0.314	34	0.4013 ± 0.057	3.136	0.021

N: number of samples; H: the Kruskal-Wallis H test

*p ≤ 0.05 indicates statistical significance