Up-regulation of expression and lack of 5' CpG island hypermethylation of p16 INK4ain HPV-positive cervical carcinomas

Table 1 Methylation and expression of gene p16 INK4a in HR-HPV-positive cervical carcinomas and cervical cancer cell lines

Carcinoma/cells line	Methylation status of 5' CpG island **	RT-PCR ***	Immunochemical detection
			Number of stained nuclei (%)	Cytoplasmic staining
1	1	-	0	Negative
2	3	+	<1
3	4	+
4	0	+	<5
5	0	+		Positive in the majority of cancer cells
6	4	+	<25
7	5*	+
8	7	+
9	12*	+
10	8*	+	>25
11	3	+
12	0	+
13	10	+	nt	nt
C4-I	0	+	<5
HeLa	2	+	10–15	Positive in the majority of cells
SiHa	6	+
C33A	0	+
CaSki	0	+	>25

* tumors that have methylated alleles, as determined by MSP
** number of partially methylated CpG dinucleotides out of 26 CpG dinucleotides in 5' region of p16 INK4a examined by bisulfite-modified DNA sequencing (see fig.1)
*** more than 3 fold increase of the mRNA level in tumor compared to normal tissues

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