Table 1. The mRNA expression of Per2, p53, Cyclin D1, CDK1 and Cyclin B1 in groups I, II and III at 6 different time points over 24 h (means ± SD, n = 5).

Gene	Tissue	4HALO	8HALO	12HALO	16HALO	20HALO	24HALO	P-value
Per2	I	0.86 ± 0.06	0.77 ± 0.10	1.89 ± 0.14	2.80 ± 0.11	1.18 ± 0.09	1.54 ± 0.19	0.000
	II	0.73 ± 0.18	1.33 ± 0.10	1.33 ± 0.19	1.46 ± 0.24	1.12 ± 0.26	0.29 ± 0.18	0.000
	III	0.35 ± 0.14	1.02 ± 0.13	1.13 ± 0.24	1.47 ± 0.24	1.49 ± 0.25	0.35 ± 0.07	0.000
p53	I	1.09 ± 0.26	1.86 ± 0.27	2.64 ± 0.21	3.82 ± 0.61	4.44 ± 1.40	6.20 ± 1.59	0.000
	II	2.64 ± 0.63	2.06 ± 0.33	1.22 ± 0.28	2.15 ± 0.20	2.63 ± 0.62	2.94 ± 1.45	0.001
	III	1.37 ± 0.14	0.84 ± 0.03	0.71 ± 0.10	1.63 ± 0.17	1.82 ± 0.69	1.40 ± 0.34	0.003
Cyclin D1	I	0.86 ± 0.12	0.90 ± 0.12	1.28 ± 0.37	2.51 ± 0.03	1.80 ± 1.40	1.17 ± 0.40	0.000
	II	2.40 ± 0.14	1.44 ± 0.29	1.36 ± 0.15	1.76 ± 0.16	2.14 ± 0.19	1.67 ± 0.09	0.000
	III	2.38 ± 0.11	2.20 ± 0.08	2.90 ± 0.16	3.19 ± 0.10	2.64 ± 0.26	2.83 ± 0.24	0.000
CDK1	I	5.91 ± 0.95	5.10 ± 0.45	1.70 ± 0.51	2.40 ± 0.44	1.21 ± 0.33	1.69 ± 0.32	0.000
	II	5.39 ± 0.55	6.55 ± 0.36	1.33 ± 0.11	2.08 ± 0.54	1.68 ± 0.28	10.0 ± 0.82	0.000
	III	2.92 ± 0.49	1.68 ± 0.18	3.74 ± 0.36	6.69 ± 0.48	6.36 ± 0.61	7.24 ± 0.87	0.011
Cyclin B1	I	1.16 ± 0.29	1.84 ± 0.12	0.39 ± 0.14	0.61 ± 0.23	1.06 ± 0.10	3.00 ± 0.37	0.000
	II	1.68 ± 0.27	1.92 ± 0.72	1.51 ± 0.72w	2.00 ± 0.25	1.70 ± 0.25	1.94 ± 0.75	0.53
	III	2.16 ± 0.64	1.79 ± 0.15	2.14 ± 0.16	2.48 ± 0.78	4.21 ± 1.00	2.55 ± 0.79	0.011

A value of P < 0.05 represents a significant difference ( I: normal buccal mucosa, II: precancerous lesion, and III: carcinoma; HALO: hour after light onset; SD: standard deviation; n: numbers).