Table 2.

Lentiviral vector integration into/near CpG islands.

Distance to CpG islands	Integration frequency (%) of reference set (n=1,000,000)	Integration frequency (%) of target set (n=874)	P value
Within CpG islands	0.84 (8384)	0.46 (4)	0.217
Within ±(0~5) kb of CpG islands	7.18 (71763)	11.78 (103)	0.000**
Within ±(5~50) kb of CpG islands	33.53 (335321)	41.30 (361)	0.000**
Within ±(50~250) kb of CpG islands	37.24 (372426)	33.98 (297)	0.050

^**Significantly different at P<0.01 for the χ² analysis as compared to the reference set.

‘+’ – downstream of CpG islands, ‘−’ – upstream of CpG islands.