Aberrant p16 methylation, a possible epigenetic risk factor in familial esophageal squamous cell carcinoma

AIM: Detection of methylation in the p16 gene, an inhibitor of cyclin D-dependent protein kinase, as a new tumor marker for early detection of esophageal squamous cell carcinoma (ESCC) in DNA derived from blood and serum. METHOD: A large family with clustering of ESCC was assessed in Khorasan province in northeastern Iran. The family had three histologically proven cases of ESCC in two consecutive generations and several other deceased cases with histories of ESCC. DNA from blood of 28 living family members in three consecutive generations, 30 sporadic ESCC cases (from serum, blood, and tumor tissues), and 30 healthy volunteers (from blood) were examined for the methylation status of p16 promoter using methylation-specific PCR (MSP). RESULTS: Aberrant p16 promoter methylation was found in 64.3% (n = 28) of ESCC family members and none (n = 30) of our normal volunteers. Five of the 28 family members with esophageal cancer symptoms had negative endoscopy results for ESCC, while four of these members had p16 hypermethylation in their blood. The family members with negative endoscopy and positive p16 promoter methylation are being monitored closely for signs of ESCC development through regular check-ups and chromoendoscopies. In sporadic ESCC in northeastern Iran, 73.3% (n = 30) of tumor tissue samples had p16 hypermethylation. Serum and blood samples from the same patients showed p16 hypermethylation in 26.6% and 43.3% of the samples, respectively. CONCLUSION: Aberrant p16 methylation may be a valuable diagnostic tool as a tumor marker for the early identification of individuals in high risk ESCC families.     

PTEN hypermethylation profiles of Chinese Kazakh patients with esophageal squamous cell carcinoma

Aberrant DNA methylation of promoter region CpG islands may serve as an alternative mechanism to genetic defects in the inactivation of tumor suppressor genes (TSGs) in human malignancies. The aim of this study was to examine the promoter methylation status of the PTEN TSG and its association with esophageal squamous cell carcinoma (ESCC) carcinogenesis in a Chinese Kazakh population, which is known to have a relatively high ESCC incidence and mortality. The methylation status of the PTEN promoter region was determined in patients with ESCC (n = 95) and healthy individuals (n = 65) using highly sensitive Sequenom Epityper assays. The methylation level of the PTEN gene was significantly higher in patients with ESCC than in healthy controls. The median methylation level was 10.0% (interquartile range [IQR]: 7.0–11.0%) in patients with ESCC and 6.0% in controls (IQR: 4.0–9.0%; P = 0.001). PTEN methylation levels were higher in male patients with ESCC than in male controls, whereas a trend toward significance was observed between female patients with ESCC and female controls (P = 0.005 and P = 0.086, respectively). The PTEN methylation level was associated with histopathological grade and lymph node metastasis in patients with ESCC (P = 0.002 and P = 0.009, respectively). To our knowledge, this is the first report to show the presence of PTEN promoter CpG hypermethylation in ESCC and its association with tumor metastasis.     

Hypermethylation of p16 gene promoter correlates with loss of p16 expression that results in poorer prognosis in esophageal squamous cell carcinomas

SUMMARY.  The purpose of this study was to analyze loss of p16 expression and its relationship to hypermethylation, clinicopathological parameters and prognosis in patients with esophageal squamous cell carcinoma (ESCC). Tissue samples from 60 ESCC were subjected to histological analysis. Immunohistochemical staining for p16 expression was performed. DNA was extracted from these primary esophageal tumors and from sera from another 38 ESCC patients. The DNA was modified with bisulfite and analyzed for p16 promoter methylation by methylation-specific polymerase chain reaction. Twelve out of the 60 tumors (20%) were methylated at the p16 promoter and 48 tumors (80%) were unmethylated. There were no significant correlations between the methylation of the p16 promoter and clinicopathological parameters. Immunohistochemical staining revealed that 41 of the 60 tumors (68.3%) were p16-negative and 19 tumors (31.7%) were p16-positive. The correlation between negative p16 immunohistochemical staining and methylation was statistically significant ( P =  0.0084). No instances of p16 methylation and p16 positive immunostaining were found. There was a close correlation between loss of p16 expression and poorer prognosis in ESCC ( P =  0.0517 in overall survival, P  = 0.0478 in disease-free survival). The p16 gene promoter hypermethylation was detected in the serum of two of 38 (5.2%) patients with ESCC. This indicates that p16 promoter methylation suppresses p16 expression and that the loss of expression has a close relationship with poor prognosis in patients with ESCC. The present results may lead to the development of new therapeutic strategies, such as p16 ^INK4A gene therapy, to treat patients with ESCC.     

Methylation status of p16INK4A tumor suppressor gene in Iranian patients with sporadic breast cancer

Introduction   p16 ^INK4A is a tumor suppressor encoding the Cdk inhibitor protein, which acts to repress Cdk4/6 and pRb phosphorylation. p16 ^INK4A gene can be inactivated by a variety of events, including promoter hypermethylation. Materials and methods  To investigate the methylation status of the p16 ^INK4A gene in Iranian patients with breast carcinoma, promoter methylation was studied by methylation-specific PCR (MSP) and restriction enzyme-related PCR (REP). In addition, p16 ^INK4A promoter was analyzed by PCR-SSCP in order to detection of mutation and single nucleotide polymorphisms. Results  Analysis of 70 patients by MPS and REP showed hypermethylation of p16 ^INK4A promoter in 35.7% (25/70) and 40% (28/70) of samples, respectively. Comparison of the molecular data and pathological information of the samples suggested that p16 ^INK4A gene might be inactivated at the early stages in breast cancer. Conclusion  Therefore, it could be suggested that hypermethylation of p16 ^INK4A promoter is one of the epigenetic factors affecting the progress of sporadic breast carcinogenesis in Iranian patients.     

Aberrant promoter hypermethylation of p16 and MGMT genes in oral squamous cell carcinomas and the surrounding normal mucosa

Purpose Several genetic alterations have been reported to contribute to the development of oral squamous cell carcinoma (OSCC). Recent studies have shown roles of promoter hypermethylation of tumor suppressor genes, including p16 and MGMT, in several types of cancers. The purpose of this study is to examine the hypermethylation status of p16 and MGMT genes in both oral cancers and normal mucosa, surrounding the cancers.Methods Promoter hypermethylation status of p16 and MGMT genes were examined by the methylation-specific PCR (MSP) in OSCC (n = 51), verrucous carcinoma (n = 2), and carcinoma in situ (n = 2) tissues. Moreover, normal mucosa surrounding the cancers were also examined in 22 cases out of the 51 OSCCs. As a normal control, oral mucosa from healthy volunteers (n = 18) was used.Results Aberrant promoter hypermethylation of p16 and MGMT genes was detected in 50.9% (28 of 55) and 56.4% (31 of 55) of the total malignant cases, respectively. As for the 22 OSCC cases, in which paired cancerous tissues and the surrounding normal mucosa were examined simultaneously, promoter hypermethylation of p16 and MGMT genes was confirmed in 72.73% (16 of 22) and 68.18% (15 of 22), respectively. In contrast, as for the surrounding normal mucosa, promoter hypermethylation of p16 and MGMT genes was recognized in 27.27% (6 of 22) cases and 40.91% (9 of 22), respectively. Conclusions Hypermethylation of both p16 and MGMT genes was frequently detected in not only OSCC tissues, but also the surrounding normal mucosa around the cancerous tissues. Thus promoter hypermethylation of p16 and MGMT genes are an important, probably early event in oral carcinogenesis.     

Hypermethylation of p14 (ARF) may be predictive of colitic cancer in patients with ulcerative colitis

Purpose The microsatellite instability and CpG island hypermethylation of p14 ^ARF and p16 ^INK4a are related to the pathogenesis of neoplasia in ulcerative colitis. This study was designed to assess the significance of those genetic or epigenetic alterations for cancer surveillance in ulcerative colitis. Methods During surveillance colonoscopy in 39 patients with ulcerative colitis, biopsy specimens were obtained from the cecum and the rectum as well as from any other areas suspected of being neoplasia by chromoscopy. Using DNA extracts, the methylation status of p14 ^ARF and p16 ^INK4a and the microsatellite status were determined. Results Microsatellite instability was positive in one of five dysplasias, but it was negative in the cecum and the rectum. The incidence of hypermethylation of p14 ^ARF was 0 percent in the cecum, 26 percent in the rectum, and 100 percent in dysplasia, whereas that of p16 ^INK4a was 10, 10, and 0 percent, respectively. Patients who were positive for the hypermethylation of p14 ^ARF in the rectum had a longer duration of ulcerative colitis than those who were negative for such hypermethylation. Two of 10 patients who were positive for p14 ^ARF hypermethylation in the rectum and 1 of 29 patients who were negative for the hypermethylation had dysplasia. During the subsequent surveillance of 36 patients, dysplasia was detected in 2 of 8 patients with p14 ^ARF hypermethylation and in none of 28 patients without hypermethylation (P = 0.044). Conclusions In patients with ulcerative colitis, hypermethylation of p14 ^ARF seems to be associated with an early stage of dysplasia. The hypermethylation may be one of candidates for potential biomarker to identify patients at a high risk of dysplasia.     

<Emphasis Type="Italic">p16</Emphasis><Superscript><Emphasis Type="Italic">INK4A</Emphasis></Superscript> Alterations are accompanied by aberrant protein immunostaining in endometrial carcinomas

Purpose To date, the significance of p16^INK4A tumor suppressor gene inactivation in sporadic endometrial cancer (EC) has only rarely been described. In this study, we examined the alteration type and frequency of gene alterations [point mutations, aberrant promoter methylation and loss of heterozygosity (LOH)] in 50 sporadic ECs, and correlated the genetic findings with the immunohistochemical expression of the p16^INK4A protein and the classical clinicopathological features.Methods Gene mutations were detected by PCR-SSCP-sequencing analysis, promoter hypermethylation by methylation-specific PCR (MSP), and LOH by PCR of the STS-marker c5.1.Results In total, p16^INK4A alterations were found in 14 of 50 (28%) sporadic ECs. In six (12%) cases, two alterations occurred simultaneously. Partial p16^INK4A deletions were found in four of 50 (8%) samples. There was one missense mutation (codon 70; CCCGCC) and one frameshift mutation (1-bp deletion in exon 2). Only 2 of 47 (4.2%) tumors exhibited aberrant promoter methylation. An allelic loss was detected in 12 of 50 (24%) carcinomas with a higher incidence in advanced endometrial carcinomas than in early-stage uterine tumors. p16^INK4A alterations were generally accompanied by gene silencing, confirmed by aberrant protein immunostaining (r=-0.442; P=0.001). There was a significant difference in the frequency of p16^INK4A alterations between early (stage I; 18%) and advanced (stages II–IV; 58%) ECs (P=0.022). One case showed complete protein loss, but absence of genetic alterations.Conclusions Our data indicate that p16^INK4A inactivation plays a role in the tumorigenesis of the subset of sporadic ECs, particularly in cases exhibiting an aggressive clinical behavior. We demonstrate that p16^INK4A methylation can act efficiently and similarly to other genetic alterations as one of the two necessary hits according to the Knudson two-hit hypothesis of tumor suppressor gene inactivation.     

Preproenkephalin hypermethylation in the pure pancreatic juice compared with p53 mutation in the diagnosis of pancreatic carcinoma

Background Aberrant methylation of CpG islands is a common mechanism for the dysregulation of tumor suppressor genes in a variety of human malignancies. Preproenkephalin ppENK) hypermethylation is recognized in 90% of pancreatic carcinoma (PCa) tissues, but not in normal pancreas. We analyzed ppENK hypermethylation in pure pancreatic juice (PPJ) in patients with PCa, intraductal papillary mucinous neoplasms (IPMN), and chronic pancreatitis (CP), and elucidated its usefulness as a marker in the diagnosis of PCa compared with p53 mutation. Methods PPJ was collected endoscopically from 28 patients with PCa, 15 patients with IPMN, and 20 patients with CP. DNA was extracted from the supernatant and the sediment of PPJ. Methylation-specific polymerase chain reaction was performed for hypermethylation analysis of ppENK. In addition, single-strand conformation polymorphism and direct sequencing were performed simultaneously to identify p53 mutations. Results The incidence of ppENK hypermethylation in the supernatant and/or the sediment of PPJ was 50% (14 of 28) in patients with PCa. In contrast, the incidence of ppENK hypermethylation was 26.7% (4 of 15) in patients with IPMN, and 5% (1 of 20) in patients with CP (P < 0.002). The incidence of p53 mutations in the PPJ was 42.9% (12 of 28) in patients with PCa and 0% (0 of 20) in patients with CP. Furthermore, the incidence of ppENK hypermethylation and/or p53 mutations in the PPJ was enhanced to 67.9% (19 of 28) in patients with PCa in the combination assay. Conclusions These results suggest that ppENK hypermethylation in PPJ is specific for cancer, and the combination assay with p53 enhances the genetic diagnosis of PCa.     

p16基因启动子区甲基化在人嗜铬细胞瘤和副神经节瘤中的变化

目的 检测嗜铬细胞瘤(PHEO)和副神经节瘤(PGL)中p16基因突变和启动子区DNA甲基化改变,分析其与患者临床特征之间的关系.方法收集34例(PHEO 20例、PGL14例)组织标本及患者临床资料,通过甲基化特异性PCR(MSP)测定p16基因启动子区甲基化状态,DNA测序检测基因序列以及RT-PCR方法测定其mRNA表达.结果 (1)34例肿瘤组织中未发现p16基因纯合缺失及点突变;(2)35.3%(12/34)的患者存在p16基因高甲基化,p16基因甲基化阳性标本中,PHEO和PGL分别占25%和75%,两者差异有统计学意义(P=0.005);p16基因甲基化在恶性、单发肿瘤、发病年龄早的亚组中有增高趋势(P＞0.05);(3)甲基化与非甲基化肿瘤组织之间p16 mRNA表达无统计学差异;不同特点的肿瘤中其mRNA表达亦无统计学差异,但恶性肿瘤p16 mRNA表达与良性肿瘤相比有下降的趋势(0.83±0.65对1.12±0.81,P=0.278).结论人PHEO和PGL中,p16基因纯合缺失和突变并不常见,但p16基因启动子区甲基化是其失活的主要形式.     

Progression of Hypermethylation of the p16 INK4A Gene from Normal Liver to Nontumorous Liver and Hepatocellular Carcinoma: An Evaluation Using Quantitative PCR Analysis

The aim of this study was to determine to what extent hypermethylation of the p16 ^INK4A (p16) gene promoter is increased in nontumorous liver tissues compared with in normal liver, using two quantitative methylation-specific polymerase chain reaction (MS-PCR) methods and a bisulfite sequencing method. Methylation of the p16 gene was detected more frequently in nontumorous liver than in normal liver using the TaqMan PCR method. Methylation indices also were significantly higher in nontumorous than in normal liver. However, the bisulfite sequencing method did not detect significantly more methylation of the p16 gene in nontumorous than normal liver, nor was there a significant difference in the level of p16 mRNA. There may be a greater proportion of cells which contain methylated p16 in nontumorous than in normal liver. However, the difference was so small that the functional relevance to hepatocarcinogenesis remains elusive.     

Associations of risk factors obesity and occupational airborne exposures with CDKN2A/p16 aberrant DNA methylation in esophageal cancer patients

It is known that obesity and occupational airborne exposure such as dust are among risk factors of esophageal cancer development, in particular squamous cell carcinoma (SCC) of esophagus. Here, we tested whether these factors could also affect aberrant DNA methylation. DNAs from 44 fresh tumor tissues and 19 non‐tumor adjacent normal tissues, obtained from 44 patients affected by SCC of esophagus (SCCE), were studied for methylation at the CDKN2A/p16 gene promoter by methylation‐specific polymerase chain reaction assay. Statistical methods were used to assess association of promoter methylation with biopathological, clinical, and personal information data, including obesity and airborne exposures. Methylation at the CDKN2A/p16 gene promoter was detected in 12 out of 44 tumor samples. None of the non‐tumor tissues exhibited the aberrant methylation. Our results confirmed previously described significant association with low tumor stage (P= 0.002); in addition, we found that obesity (P= 0.001) and occupational exposure (P= 0.008) were both significantly associated with CDKN2A/p16 promoter methylation. This study provides evidence that obesity and occupational exposure increase the risk of developing esophageal cancer through an enhancement of CDKN2A/p16 promoter methylation.     

Abnormalities of tumor suppressor gene <Emphasis Type="Italic">p16</Emphasis>in pancreatic carcinoma: immunohistochemical and genetic findings compared with clinicopathological parameters

Background. Abnormalities of the tumor suppressor gene p16 have been reported in a variety of human tumors but are rare in pancreatic carcinoma except for cancer cell lines and xenografts. Their clinicopathological significance remains unknown. The purpose of this study was to examine immunohistochemical and genetic alterations of p16 in primary pancreatic carcinoma tissues and to investigate the relation between abnormalities of p16 and clinicopathological parameters to elucidate their clinicopathological significance. Methods. We investigated p16 expression in 60 pancreatic carcinoma cases by immunohistochemistry using a monoclonal antibody clone G175-405. In addition, we analyzed genetic alterations of the p16 gene using DNA extracted from microdissected tissue of pancreatic carcinoma, by polymerase chain reaction, nonradioisotopic single-strand conformation polymorphism (non-RI-SSCP), DNA sequencing, and hypermethylation analyses using restriction enzymes. We compared the abnormalities of p16 alterations with clinicopathological parameters to elucidate their significance. Results. On immunohistochemical study, staining for p16 protein was strongly positive in 22 (37%) of 60 pancreatic carcinoma cases, weakly positive in 24 (40%), and negative in 14 (23%). In contrast, p16 mutations were recognized in 9 (15%) of the 60 pancreatic carcinoma cases. The incidence of p16 mutations was 2 (9%) in 22 cases of pancreatic carcinoma with strongly positive staining, 4 (17%) in 24 with weakly positive staining, and 3 (21%) in 14 with negative staining. Hypermethylation of p16 was detected in the two pancreatic carcinoma cases with weakly positive staining, although homozygous deletions were not found in any case. There was no significant correlation between the expression of p16 protein and any of the clinicopathological parameters. However, there was a tendency for the tumor to be larger in patients with decreased expression of p16 protein than in those with normal expression levels. In contrast, the tumor was significantly larger and the survival period significantly shorter for patients with pancreatic carcinoma with p16 mutation or hypermethylation than for those with pancreatic carcinoma with an intact p16 gene (P 0.05). Conclusions. These findings suggest that p16 alterations may participate in the aggressiveness of pancreatic carcinoma.     

Promoter methylation profile in gallbladder cancer

Background Methylation in the promoter region of genes is an important mechanism of inactivation of tumor suppressor genes. Our objective was to analyze the methylation pattern of some of the genes involved in carcinogenesis of the gallbladder, examining the immunohistochemical expression of proteins, clinical features, and patient survival time. Methods Twenty cases of gallbladder cancer were selected from the frozen tumor bank. The DNA extracted was analyzed by means of a methylation-specific polymerase chain reaction test for the CDKN2A (p16), MLH1, APC, FHIT, and CDH1 (E-cadherin) genes. Morphological and clinical data and follow-up information were obtained. Results All cases were in an advanced stage: histologically moderate or poorly differentiated tumors (95%). Methylation of the promoter area of genes was observed in 5%, 20%, 30%, 40%, and 65% of cases, and an altered immunohistochemical pattern (AIP) in 5%, 35%, 21%, 25%, and 66% for the MLH1, CDKN2A, FHIT, APC, and CDH1 genes, respectively. The Kappa concordance index between methylation of the promoter area and AIP for the MLH1 and CDH1 genes was very high (K > 0.75) and substantial for APC (K > 0.45). No correlation was found between survival time and the methylation of the genes studied. Conclusions The high frequency of gene methylation (with the exception of MLH1) and the high agreement between AIP and methylation of the gene promoter area for the MLH1, APC, and CDH1 genes suggest that the inactivation of tumor suppressor genes and of the genes related to the control of cellular proliferation through this mechanism is involved in gallbladder carcinogenesis.     

The hypermethylation and protein expression of p16 INK4A and DNA repair gene O6-methylguanine-DNA methyltransferase in various uterine cervical lesions

Purpose This study is aimed at investigating the significance of gene promoter methylation status and protein expression of p16 ^INK4A and O⁶-methylguanine-DNA methyltransferase (MGMT) in the various uterine cervical lesions.Materials and methods Methylation status by using methylation-specific polymerase chain reaction (MS-PCR) and protein expression by using immunohistochemistry for p16 ^INK4A and MGMT genes were performed in cervical squamous intraepithelial neoplasms (CIN), invasive squamous cell carcinomas (SCC), adenocarcinomas and non-neoplastic cervices.Results None of 20 non-neoplastic cervices showed p16 ^INK4A and MGMT gene hypermethylation, whereas at least one of these genes was hypermethylated with 50.0% (5/10) of CIN I, 65.0% (13/20) of CIN II–III, 70.2% (33/47) of SCC and 85.0% (17/20) of adenocarcinoma. p16 ^INK4A protein was totally negative in non-neoplastic cervices, but positive with 90.0% of CIN I, 100% of CIN II–III and adenocarcinoma, and 78.7% of SCC. MGMT protein was expressed in 10% of non-neoplastic cervices, but significantly increased in SCC (42.5%) and adenocarcinoma (70.0%). The protein expression of p16 ^INK4A and MGMT was not related to their gene promoter methylation status.Conclusions The hypermethylation of p16 ^INK4A and MGMT genes in the uterine cervix may indicate the presence of malignant cells, and p16 ^INK4A immunostaining is useful in grading CIN and diagnosing invasive SCC and adenocarcinoma.     

食管鳞癌组织p16基因调控区甲基化及其蛋白表达研究

目的探讨p16基因在食管癌变过程中表达缺失与其启动子区甲基化的关系。方法采用MSP免疫组化方法,检测环太行山地区45例食管鳞癌患者癌组织p16基因启动子区甲基化状态及蛋白表达情况。结果p16基因在癌组织中表达异常41例（91．1％）,间变组织中表达异常38例（84．4％）,发生纯合型甲基化的组织分别为33例（73．3％）（癌组织）和32例（71．1％）（间变组织）,而其周围正常组织26例（57．8％）均发生了p16启动子区的杂合型甲基化。p16基因纯合型甲基化与癌组织、间变组织、p16蛋白表达缺失相关（P〈0．05）。结论该地区食管癌组织p16基因在癌前病变中p16启动子区即发生了纯合型甲基化、食管癌变的早期事件。p16基因启动子区甲基化可单独影响p16蛋白的正常表达。     

Aberrant methylation of <Emphasis Type="Italic">p16</Emphasis> predicts candidates for 5-fluorouracil-based adjuvant therapy in gastric cancer patients

Background Aberrant methylation of some cancer-related genes has been reported to correlate with sensitivity to chemotherapeutic agents. The present study was designed to determine whether DNA methylation in six cancer-related genes affects recurrence of gastric cancer in patients who received 5-fluorouracil-based adjuvant chemotherapy. Methods The methylation status of six genes, MGMT, CHFR, hMLH1, p16INK4a, E-cadherin, and Runx3, was analyzed in 56 surgically resected gastric cancer tissue specimens by methylation-specific polymerase chain reaction. Of the 56 patients who underwent surgical resection, 38 received 5-fluorouracil (5-FU)-based adjuvant chemotherapy postoperatively (adjuvant group), whereas the other 18 (32%) did not (surgery group). Results There were no significant differences between the two groups with respect to sex, cancer differentiation, depth of tumor invasion, lymph node metastasis, lymphatic invasion, vascular invasion and tumor stage. Among the genes, methylation of p16INK4a showed a significant correlation with longer survival in the 38 patients of the adjuvant group, but not in the 18 patients of the surgery group. A multivariate analysis identified p16INK4a methylation to be an independent factor predicting a longer recurrence-free period under 5-FU-based adjuvant chemotherapy. Conclusions The present study demonstrated for the first time that gastric cancer patients with p16INK4a methylation specifically benefit from 5-FU-based adjuvant chemotherapy.     

Hypermethylation of the CDKN2/p16 promoter during neoplastic progression in Barrett's esophagus

Background & Aims: Inactivation of the CDKN2/p16^INK4A tumor-suppressor gene is one of the most frequent genetic alterations in human malignancies. In esophageal adenocarcinomas, mutations of the p16 gene or homozygous deletions of the gene locus 9p21 are rare. This study investigated whether p16 promoter hypermethylation is an alternative mechanism for p16 gene inactivation during neoplastic progression in Barrett's esophagus. Methods: A methylation-specific polymerase chain reaction protocol was applied. A total of 95 specimens from 14 patients with Barrett's esophagus were analyzed longitudinally. The p16 promoter status was compared with histomorphological findings. Results: p16 promoter hypermethylation was detected in 9 of the 10 patients who had displayed dysplasia at some time during surveillance, whereas none of the patients who had not displayed dysplasia during surveillance had p16 promoter hypermethylation. p16 promoter hypermethylation was detected in 3% (2 of 67) of the samples without dysplasia, 60% (3 of 5) of the samples with lesions indefinite for dysplasia, 55.6% (10 of 18) of the specimens with low-grade dysplasia, and 75% (3 of 4) of the specimens with high-grade dysplasia. Conclusions: These data suggest that p16 promoter hypermethylation is a common mechanism of p16 gene inactivation during neoplastic progression in Barrett's esophagus.GASTROENTEROLOGY 1998;115:1381-1386