Methylation of CpG islands of p16 associated with progression of primary gastric carcinomas

• Published in: Laboratory investigation Vol. 86; no. 6; pp. 591 - 598
• Main Authors: Luo, Daya, Zhang, Baozhen, Lv, Lingbo, Xiang, Shengyan, Liu, Yahang, Ji, Jiafu, Deng, Dajun
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.06.2006; Nature Publishing; Nature Publishing Group
• Subjects: Adult; Aged; Aged, 80 and over; Biological and medical sciences; Biological Assay; Biotechnology; Carcinoma - metabolism; Carcinoma - pathology; Carcinoma - surgery; Cell Line, Tumor; Chromatography, High Pressure Liquid; Colonic Neoplasms - pathology; CpG Islands; DHPLC; Disease Progression; DNA Methylation; DNA, Neoplasm - genetics; Female; Fundamental and applied biological sciences. Psychology; gastric carcinoma; Genes, p16; Humans; Investigative techniques, diagnostic techniques (general aspects); Male; Medical sciences; methylation; Middle Aged; Neoplasm Metastasis; Neoplasm Staging; p16; quantification; Reproducibility of Results; Sequence Analysis, DNA; Stomach Neoplasms - metabolism; Stomach Neoplasms - pathology; Stomach Neoplasms - surgery; Sulfites - chemistry; CpG Islands; DHPLC; quantification; p16; gastric carcinoma; methylation; Biotechnology; Nucleotide sequence; Malignant tumor; Denaturing HPLC chromatogrphy; Stomach cancer; CDKN2 gene; Stomach carcinoma; GC rich sequence; Clinical biology; Primary; Digestive diseases; Methylation; Gastric disease; Quantitative analysis
• ISSN: 0023-6837; 1530-0307
• DOI: 10.1038/labinvest.3700415

Inactivation of p16 by methylation of CpG islands is a frequent early event in gastric carcinogenesis. The positive relationship between p16 methylation and the clinical characteristics of gastric carcinomas (GC) has not been reported to date. In the present study, a DHPLC assay to quantify p16 methylation was established (detection limit by fluorescence detector: 1:255 (Methlyated vs Unmethylated)). The proportion of methylated p16 in the representative samples was confirmed and standardized by clone sequencing. Then, the DHPLC and two regular methylation-specific PCR (MSP) assays were used to detect p16 methylation in 82 paired, resected GCs and their adjacent normal tissues. Results showed that the average proportion of methylated p16 in GCs was significantly higher than that in their adjacent samples (12.90 vs 0.63%; t-test P=0.005). A much higher proportion of methylated p16 was detected in GCs with metastases (local or distant) than without metastases (14.76 vs 2.61%; t-test P=0.014). A proportional relationship was observed between clinical stages and positive rates of p16 methylation in GCs and/or adjacent tissues: 27.3, 37.5, and 58.8% (by DHPLC) for stage-I, -II, -III–IV of GCs, respectively (two-sided Fisher's exact test P=0.016). To confirm the data obtained by DHPLC, two MSP primer sets (p16-M and p16-M2) were also used to analyze p16 methylation in the same set of samples simultaneously. Data of MSP assay using the primer set p16-M2, but not p16-M, correlated with that of DHPLC. These results imply that the primer set p16-M2 might be more suitable than p16-M to detect p16 methylation in gastric tissues. In conclusion, the present data indicates that p16 methylation correlates with progression of GCs significantly.