p16 gene methylation in colorectal cancers associated with Duke′s staging

DNA methylation and cancer: transcriptional regulation, prognostic, and therapeutic perspective

DNA methylation is one among the major grounds of cancer progression which is characterized by the addition of a methyl group to the promoter region of the gene thereby causing gene silencing or increasing the probability of mutations; however, in bacteria, methylation is used as a defense mechanism where DNA protection is by addition of methyl groups making restriction enzymes unable to cleave. Hypermethylation and hypomethylation both pose as leading causes of oncogenesis; the former being more frequent which occurs at the CpG islands present in the promoter region of the genes, whereas the latter occurs globally in various genomic sequences. Reviewing methylation profiles would help in the detection and treatment of cancers. Demethylation is defined as preventing methyl group addition to the cytosine DNA base which could cause cancers in case of global hypomethylation, however, upon further investigation; it could be used as a therapeutic tool as well as for drug design in cancer treatment. In this review, we have studied the molecules that induce and enzymes (DNMTs) that bring about methylation as well as comprehend the correlation between methylation with transcription factors and various signaling pathways. DNA methylation has also been reviewed in terms of how it could serve as a prognostic marker and the various therapeutic drugs that have come into the market for reversing methylation opening an avenue toward curing cancers.

Aberrant Promoter Hypermethylation of p16 and RASSF1a Genes in Colorectal Cancer - Significance in Young Patients

OBJECTIVE

The clinical profile of colorectal cancers (CRC) in India is different from that described in western countries. Microsatellite instability and APC mutation explain the molecular biology of up to 50% of colorectal cancers. Global genome hypermethylation may be the cause in at least 20% of cases. Few studies from India have examined the epigenetic profile of colorectal cancers. This study was designed to study aberrant promoter hypermethylation of two select tumour suppressor genes (p16, RASSF1a) in patients with colorectal cancer and their association with clinicopathologic features.

METHODS

A total of 41 samples including controls were collected from colorectal cancer patients. DNA was isolated from tumour tissue, and methylation-specific PCR was performed for the 2 genes.

RESULTS

p16 and RASSF1a promoter hypermethylation was found in 26% and 48% of CRC cases, respectively. RASSF1a promoter hypermethylation was more often seen in young CRC patients aged 40 years or less, and this was found to be statistically significant (p value = 0.037).

CONCLUSION

RASSF1a hypermethylation is peculiar to rectal cancers and left-sided colonic tumours in young patients. Large-scale population-based studies with extensive genetic and epigenetic characterization are required for a better understanding and further validation of our findings. For individuals diagnosed with sporadic CRC, these studies on specimen might help predict prognosis and response to therapy.

Sex and Race-Related DNA Methylation Changes in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the sixth most common cancer and fourth leading cause of cancer-related death worldwide. The number of HCC cases continues to rise despite advances in screening and therapeutic inventions. More importantly, HCC poses two major health disparity issues. First, HCC occurs more commonly in men than women. Second, with the global increase in non-alcoholic fatty liver diseases (NAFLD), it has also become evident that HCC is more prevalent in some races and/or ethnic groups compared to others, depending on its predisposing etiology. Most studies on HCC in the past have been focused on genetic factors as the driving force for HCC development, and the results revealed that genetic mutations associated with HCC are often heterogeneous and involve multiple pathogenic pathways. An emerging new research field is epigenetics, in which gene expression is modified without altering DNA sequences. In this article, we focus on reviewing current knowledge on HCC-related DNA methylation changes that show disparities among different sexes or different racial/ethnic groups, in an effort to establish a point of departure for resolving the broader issue of health disparities in gastrointestinal malignancies using cutting-edge epigenetic approaches.

Prognostic and clinicopathological value of p16 protein aberrant expression in colorectal cancer: A PRISMA-compliant Meta-analysis

PURPOSE

Several studies have examined the potential role of p16 protein expression as a diagnostic and prognostic biomarker in various cancers. However, it remains unclear whether p16 protein expression is a prognostic and diagnostic factor for colorectal cancer. Therefore, this meta-analysis is conducted to evaluate the associations of p16 protein expression with overall survival (OS) and clinicopathological characteristics of colorectal cancer.

METHODS

According to PRISMA guideline, relevant literatures were identified by searching Medicine, Web of Science, WanFang, and CNKI databases. The pooled hazard ratios (HRs) with 95% confidence intervals (CIs) were extracted from included studies to assess the association between p16 protein expression and OS of patients with colorectal cancer. Other relevant data were extracted to evaluate the correlations of p16 protein expression with risk and clinicopathological characteristics of colorectal cancer. Stata 12.0 software was applied to calculate the strength of association between p16 protein expression and colorectal cancer.

RESULTS

Forty-one studies were included to evaluate the association between p16 protein expression and colorectal cancer. Nine studies involving 1731 patients with colorectal cancer found that there was no association between p16 protein expression and OS of colorectal cancer in the overall analysis (HR = 0.78, 95% CI: 0.55-1.10). However, p16 protein overexpression was significantly associated with a better prognosis in patients with colorectal cancer when cut-off value of p16 protein expression was <10% (HR = 0.23, 95% CI: 0.08-0.66). The results of subgroup analysis based on ethnicity indicated that p16 protein overexpression was a risk factor for the occurrence of colorectal cancer in Caucasians (odds ratio = 28.95, 95% CI: 6.08-137.89), but not in Asians. Furthermore, p16 protein overexpression was significantly associated with the Dukes stage, lymph node metastasis, tumor location, and Tumor Lymph Node Metastasis-stage of colorectal cancer.

CONCLUSIONS

p16 protein overexpression might be a useful biomarker to predict the clinicopathological progress and prognosis of colorectal cancer.

p16 protein is upregulated in a stepwise fashion in colorectal adenoma and colorectal carcinoma

BACKGROUND/AIMS

p16 is tumor suppressor gene acting as a cell cycle regulator. The present study was conducted to compare p16 expression in normal, dysplastic, and malignant colonic mucosae, and to explore its relation to clinicopathological variables and follow-up data in colorectal carcinoma (CRC).

PATIENTS AND METHODS

Tissue microarrays were performed from 25 normal colonic mucosae, 41 colonic adenomas, and 191 CRC, with corresponding 50 nodal metastases. Immunohistochemistry was performed using anti-p16 antibody, sections were scored, and statistical analysis was performed. K-ras mutation detection was also performed.

RESULTS

Immunoexpression of p16 was significantly higher in CRC than in adenomas (P = 0.033) and normal colonic mucosa (P = 0.005). There was no statistically significant difference between p16 expression in CRC and nodal metastasis. There was no significant association between p16 immunoexpression in CRC and all clinicopathological data and survival probability. K-ras mutations were detected in 34% of CRC. However, there was no correlation between K-ras status and p16 expression (P = 0.325).

CONCLUSION

Absence of p16 expression is correlated to a benign course of CRC adenomas. p16 has a key role in CRC progression and can be used as a marker for colorectal adenoma. On the other hand, it has no role as a predictive and/or prognostic factor in CRC. Further extended studies are required to explore the role of p16 as indicator of premalignant lesions in the colon and to test its relation with CRC histological grade, as well as to test its value as a new therapeutic target.

Relationships between p16 gene promoter methylation and clinicopathologic features of colorectal cancer: a meta-analysis of 27 cohort studies

Many existing studies have demonstrated that p16 promoter methylation might be correlated with the clinicopathologic features of colorectal cancer (CRC), but individually published results are inconclusive. This meta-analysis aimed to derive a more precise estimation of the relationships between p16 promoter methylation and the clinicopathologic features of CRC. We searched the CISCOM, CINAHL, Web of Science, PubMed, Google Scholar, EBSCO, Cochrane Library, and CBM databases from inception through August 1, 2013. Meta-analysis was performed using the STATA 12.0 software. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated under fixed- or random-effects models. Twenty-seven clinical cohort studies were included with a total of 3311 CRC patients. Our meta-analysis results revealed that p16 promoter methylation was associated with pathological characteristics of CRC (tumor, nodes, metastasis stage: OR=1.55, 95% CI: 1.14-2.13, p=0.006; lymph node metastasis: OR=2.40, 95% CI: 1.37-4.19, p=0.002; histologic grade: OR=2.72, 95% CI: 1.63-4.54, p<0.001; Dukes stage: OR=2.06, 95% CI: 1.57-2.71, p=0.002; tumor size: OR=1.99, 95% CI: 1.03-3.85, p=0.041; location: OR=2.49, 95% CI: 1.95-3.18, p<0.001, respectively). Subgroup analysis by ethnicity suggested that there were also significant correlations between p16 gene promoter methylation and pathological characteristics of CRC among both Caucasian and Asian populations (all p<0.05). Our meta-analysis suggests that promoter methylation of the p16 gene may be strongly correlated with the clinicopathologic features of CRC. Thus, p16 gene promoter methylation may be a potential biomarker for CRC.

Determining the effect of DNA methylation on gene expression in cancer cells

DNA methylation, a DNA modification by adding methyl group to cytosine, has an important role in the regulation of gene expression. DNA methylation is known to be associated with gene transcription by interfering with DNA-binding proteins, such as transcription factors. DNA methylation is closely related to tumorigenesis, and the methylation state of some genes can be used as a biomarker for tumorigenesis. Aberrant DNA methylation of genomic regions, including CpG islands, CpG shores, and first exons, is related to the altered gene expression pattern characteristics of all human cancers. Subheading 1 surveys recent developments on DNA methylation and gene expressions in cancer. Then we provide analysis of DNA methylation and gene expression in 30 breast cancer cell lines representing different tumor phenotypes. This study conducted an integrated analysis to identify the relationship between DNA methylation in various genomic regions and expression levels of downstream genes, using MethylCapseq data (affinity purification followed by next-generation sequencing of eluted DNA) and Affymetrix gene expression microarray data. The goal of this study was to assess genome-wide methylation profiles associated with different molecular subtypes of human breast cancer (luminal, basal A, and basal B) and to comprehensively investigate the effect of DNA methylation on gene expression in breast cancer phenotypes. This showed that methylation of genomic regions near transcription start sites, CpG island, CpG shore, and first exon was strongly associated with gene repression, and the effects of the regions on gene expression patterns were different for different molecular subtypes of breast cancer. The results further indicated that aberrant methylation of specific genomic regions was significantly associated with different breast cancer subtypes.

The blues of P(16)INK(4a): aberrant promoter methylation and association with colorectal cancer in the Kashmir valley

Hypermethylation of the promoter region of the p16INK4a (p16) gene plays a significant role in the development and progression of colorectal cancer (CRC). The aim of the present study was to establish the role of the methylation status of the p16 gene in 114 CRC cases and to correlate it with the various clinicopathological parameters. Analysis of p16 promoter methylation was performed by methylation-specific PCR. Forty-eight (42.1%) of the CRC cases were found to be methylated for the p16 gene in our population. The methylation status was found to be associated with the gender, lymph node status, tumour stage, smoking status and tumour grade of the CRC patients. p16 plays a pivotal role in tumour development and progression to advanced stages.

Prognostic significance of regulators of cell cycle and apoptosis, p16(INK4a), p53, and bcl-2 in primary mucosal melanomas of the head and neck

Abnormalities in cell cycle regulation, tumor suppressor gene functions and apoptosis are frequent events in tumorigenesis. Their role in the pathogenesis and prognosis of primary mucosal melanomas (MM) of the upper aerodigestive tract remains unknown. Sixty-four patients (40 men, 24 women, median age 64 years) with MM were included in this study; 32 had tumors in the nasal/paranasal cavities, 28 in the oral cavity and 4 in the pharynx. Archival tissues from 47 initial mucosal tumors, 17 mucosal recurrences, and 13 nodal/distant metastases were subjected to immunohistochemistry using antibodies against p16, p53, and bcl-2. The results were correlated with histological features and survival data. Expressions of p16, p53, and bcl-2 proteins were seen in 25% (N=19/76), 21% (N=16/76), and 74% (N=56/76) of all tumors, respectively. bcl-2 expression in the initial tumors was associated with significantly longer overall and disease specific survival (3.3 vs. 1.5 years, P ≤ 0.05). Expression of p16 was increasingly lost, from 32% in initial tumors to 12% in recurrent and 15% in metastatic tumors (P=0.06). Tumors comprised of undifferentiated cells were significantly more p53 positive than epithelioid or spindle cells (80% vs. 33%, P=0.02). Expression of these markers did not correlate with necrosis, or vascular and/or deep tissue invasion. Expression of bcl-2 is associated with better survival in MM. Loss of p16 was seen with tumor progression whereas aberrant p53 expression was frequent in undifferentiated tumor cells.

Promoter methylation and loss of p16(INK4a) gene expression in head and neck cancer

BACKGROUND

Silencing of tumor suppressor genes plays a vital role in head and neck carcinogenesis. In this study we aimed to evaluate aberrant p16(INK4a) gene promoter methylation in patients with head and neck cancer.

METHODS

Methylation of the gene was investigated by bisulfite modification/methylation-specific polymerase chain reaction and gene expression levels were analyzed by quantitative reverse transcription-polymerase chain reaction in tumors and matched normal tissue samples from Turkish patients with head and neck cancer.

RESULTS

The promoter region of the p16(INK4a) gene was methylated in 67.5% and 28.6% of the primary tumors and the corresponding normal tissue, respectively. This difference was highly significant. In concordance, p16(INK4a) gene expression was downregulated in 67.5% of the tumor samples. Methylation and the absence of expression in the tumors were observed in 48% of the patients.

CONCLUSIONS

Our data indicate that methylation of the p16(INK4a) gene is a frequent event in primary head and neck cancer and that it plays a major role in the silencing of p16(INK4a) gene expression during tumor development.

Aberrant methylation of hMLH1 and p16INK4a in Tunisian patients with sporadic colorectal adenocarcinoma

The methylation of CpG islands in the promoters is associated with loss of protein via repression of gene transcription. Several studies have demonstrated that tumour suppressor and DNA repair genes are often aberrantly hypermethylated in colorectal cancer. The present study was conducted to examine whether the methylation profile of p16INK4a and hMLH1 (human mutL homologue 1) promoters was associated with clinical features and patients’ survival in CRC (colorectal carcinoma). Aberrant methylation of p16INK4a and hMLH1 promoters was found in 47.2 and 53.4% of tumours respectively. For adjacent non-tumoral mucosa, p16INK4a was fully unmethylated in 30% of the cases, whereas hMLH1 was predominantly unmethylated (76%). Methylation of p16INK4a correlated with gender and tumour size (P=0.005 and 0.035 respectively), whereas those of hMLH1 significantly correlated with overall survival (P log rank = 0.007). Concomitant methylation of p16INK4a and hMLH1 was associated with TNM (tumour, lymph node and metastases) stage and tumour size (P=0.024 and 0.021 respectively). Our data show that loss of hMLH1 expression through aberrant methylation could be used as a marker of poor prognosis in CRC.

Aberrant promoter methylation of p16 in colorectal adenocarcinoma in North Indian patients

AIM: To investigate p16 gene methylation and its expression in 30 patients with sporadic colorectal adenocarcinoma in a North Indian population.

METHODS: Methylation specific polymerase chain reaction was used to detect p16 gene methylation and immunohistochemistry was used to study the p16 expression in 30 sporadic colorectal tumors as well as adjoining and normal tissue specimens.

RESULTS: Aberrant promoter methylation of p16 gene was detected in 12 (40%) tumor specimens, whereas no promoter methylation was observed in adjoining and normal tissue. Immunohistochemistry showed expression of p16 protein in 26 (86.6%) colorectal tumors whereas complete loss of expression was seen in 4 (13.3%) and reduced expression was observed in 12 (40%) tumors. In the adjoining mucosa, expression of p16 was in 11 (36.6%) whereas no clear positivity for p16 protein was seen in normal tissue. There was a significant difference in the expression of p16 protein in tumor tissue and adjoining mucosa (P < 0.001). The methylation of the p16 gene had a significant effect on the expression of p16 protein (P = 0.021). There was a significant association of methylation of p16 gene with the tumor size (P = 0.015) and of the loss/reduced expression of p16 protein with the proximal site of the tumor (P = 0.047). Promoter methylation and expression of p16 had no relation with the survival of the patients (P > 0.05).

CONCLUSION: Our study demonstrated that promoter hypermethylation of the p16 gene results in loss/reduced expression of p16 protein and this loss/reduced expression may contribute to tumor enlargement.

Aberrant p16((INK4a)) methylation is a frequent event in colorectal cancers: prognostic value and relation to mRNA expression and immunoreactivity

PURPOSE

Aberrant p16((INK4a)) promoter methylation is common in colorectal cancer (CRC), but its clinicopathological significance remains controversial. The present study was therefore conducted to analyze p16((INK4a)) methylation and its relationship to clinicopathological features, mRNA levels and immunoreactivity in a series of lesions.

METHODS

p16((INK4a)) methylation was assessed for normal mucosa (n = 30) and CRC samples (n = 212) by methylation-specific real-time quantitative PCR, and p16((INK4a)) expression by immunostaining in formalin-fixed paraffin-embedded specimens. In addition, fresh DNA (n = 61) was analyzed for relationships to p16((INK4a)) mRNA by reverse-transcription PCR.

RESULTS

The p16((INK4a)) methylation index of normal mucosa samples ranged from 0 to 2% (mean, 0.23%; median, 0.02%), while the values for tumor samples varied widely from 0 to 100% (mean, 25.7%; median, 7.1%), the difference being statistically significant (P < 0.001). Of 151 paraffin-embedded CRC tissue samples, 51 (34%), 54 (36%), and 46 (30%) were classified as low, intermediate, and high for aberrant methylation of p16((INK4a)). High p16((INK4a)) methylation was significantly associated with large tumor size (P = 0.025). Patients with higher methylation further showed more frequent recurrence as compared with the low-methylation group, and shortened cancer-related survival (Hazard ratio [HR], 3.379; P < 0.001) and recurrence-free survival (HR, 3.962; P < 0.001 on multivariate analysis). A significant inverse relationship was apparent between the p16((INK4a)) methylation and immunoreactivity (P = 0.017). A similar tendency was also observed for the methylation status and the mRNA level (P = 0.195).

CONCLUSIONS

We conclude that p16((INK4a)) methylation results in transcriptional silencing and defines a group of CRCs with a poor prognosis.

Epigenetic events in normal colonic mucosa surrounding colorectal cancer lesions

Gene inactivation by promoter hypermethylation has been demonstrated in the colonic mucosa of colorectal cancer (CRC) patients. However, current data do not prove direct involvement of this epigenetic modification in the early stages of CRC. Promoter methylation profiles of E-cadherin, hMLH1, MGMT, p16(INK4a), p15(INK4b) and p14(ARF); mutations of K-ras, B-raf and TP53 and microsatellite instability (MSI) were examined in normal and cancerous colonic mucosal tissue in 82 CRC patients using methylation-specific PCR assays. Methylation of hMLH1 and MGMT in normal mucosa correlated significantly with MSI and K-ras activation in neighbouring cancerous mucosal tissues. Similarly, poorly differentiated tumours were associated with methylated p16(INK4a) and E-cadherin in neighbouring normal colonic tissues (NCTs). Our results indicate that epigenetic changes in mucosa surrounding colorectal neoplastic lesions may describe a 'field cancerisation' phenomenon that may occur previous to genetic alterations in early stages of carcinogenesis.

Comethylation of p16 and MGMT genes in colorectal carcinoma: Correlation with clinicopathological features and prognostic value

AIM: To investigate the significance of p16 and O⁶-methylguanine-DNA methyltransferase (MGMT) genes promoter hypermethylation and K-ras mutations on colorectal tumorigenesis and progression.

METHODS: p16 and MGMT methylation status was examined on 47 tumor samples, and K-ras mutational status was examined on 85 tumor samples. For methylation analysis, a methylation specific PCR (MS-PCR) method was used.

RESULTS: p16 and MGMT promoter methylation was found in 51% (24/47) and 43% (20/47) of CRCs, respectively, and the K-ras mutation was found in 44% (37/85) of CRCs. Comethylation of p16 and MGMT genes was significantly associated with lower aggressiveness of the disease within a two-year period of observation. Only 27% of patients with simultaneous p16 and MGMT methylation showed the detectible occurrence of metastasis and/or death, compared to 67% of patients without double methylation or with no methylation (3/11 vs 22/33, P < 0.05, χ²-test). In addition, p16 and MGMT comethylation showed a trend toward an association with longer survival in patients with CRCs (35.5 ± 6.0 mo vs 23.1 ± 3.2 mo, P = 0.072, Log-rank test). Progression of the disease within a two-year period was observed in 66% of patients carrying the K-ras mutation, compared to only 19% of patients with wild type K-ras (29/44 vs 7/37, P < 0.001, χ²-test). The presence of the K-ras mutation significantly correlated to shortened overall survival (20.0 ± 1.9 mo vs 37.0 ± 1.8 mo, P < 0.001, Log-rank test). The comethylation of p16 and MGMT genes was significantly associated with lower aggressiveness of the disease even when K-ras mutations were included in the analysis as an independent variable.

CONCLUSION: Our data suggest that comethylation of promoters of p16 and MGMT genes could have a prognostic value in patients with CRC. Specifically, concurrent methylation of both genes correlates with better prognosis.

Relationship between point gene mutation, chromosomal abnormality, and tumour suppressor gene methylation status in colorectal adenomas

Epigenetic mechanisms in carcinogenesis may have a significant role in the development of colorectal cancer. To investigate this phenomenon in early-stage disease, promoter methylation status in the tumour suppressor genes APC, MGMT, hMLH1, P14/P14ARF, and CDKN2A/P16 was investigated in 78 colorectal adenomas. These had previously been characterized for mutations of APC, KRAS, and TP53 genes and for chromosomal abnormality by comparative genomic hybridization (CGH). APC hypermethylation was seen in 52 tumours (66.7%). APC showed either methylation or mutation in 66 lesions (84.6%), but these events were not statistically associated. MGMT methylation was detected in 39 cases (50%). Adenomas with this abnormality showed a significantly lower number of chromosomal changes by CGH (p < 0.02), confirming that DNA repair defect of this type is associated with a lower level of chromosomal instability. An hMLH1 methylation defect was seen in only one adenoma (1.3%), from a patient who had a synchronous cancer showing the same defect. Methylation of P14 (P14ARF) was seen in 31 adenomas (39.7%) and CDKN2A (P16) abnormality in 25 (32.1%). DNA methylation at two or more loci was seen in 46 tumours (59%), while 11 lesions (14.1%) showed no evidence of hypermethylation at any of the loci studied. Methylation at any or all of MGMT, P14 or P16 was significantly associated with APC methylation (p = 0.01). Those neoplasms with more than two methylated genes showed significantly fewer chromosomal abnormalities than adenomas with one or no methylated loci (p < 0.001). There was no association between specific individual chromosomal abnormalities, APC, KRAS or TP53 mutations and any pattern of methylation abnormality. We conclude that methylation abnormality is very common in pre-invasive colorectal neoplasia, and that high level methylation is associated with low level chromosomal instability.

Genetic and epigenetic changes in primary metastatic and nonmetastatic colorectal cancer

Colorectal cancer (CRC) develops as multistep process, which involves genetic and epigenetic alterations. K-Ras, p53 and B-Raf mutations and RASSF1A, E-Cadherin and p16INK4A promoter methylation were investigated in 202 CRCs with and without lymph node and/or liver metastasis, to assess whether gene abnormalities are related to a metastogenic phenotype. K-Ras, B-Raf and p53 mutations were detected in 27, 3 and 32% of the cases, with K-Ras mutations significantly associated with metastatic tumour (P=0.019). RASSF1A, E-Cadherin and p16INK4A methylation was documented in 20, 44 and 33% of the cases with p16INK4A significantly associated with metastatic tumours (P=0.001). Overall, out of 202 tumours, 34 (17%) did not show any molecular change, 125 (62%) had one or two and 43 (21%) three or more. Primary but yet metastatic CRCs were prevalent in the latter group (P=0.023) where the most frequent combination was one genetic (K-Ras in particular) and two epigenetic alterations. In conclusion, this analysis provided to detect some molecular differences between primary metastatic and nonmetastatic CRCs, with K-Ras and p16INK4A statistically altered in metastatic tumours; particular gene combinations, such as coincidental K-Ras mutation with two methylated genes are associated to a metastogenic phenotype.

Immunohistochemical analysis of thymidylate synthase, p16(INK4a), cyclin-dependent kinase 4 and cyclin D1 in colorectal cancers receiving preoperative chemotherapy: significance of p16(INK4a)-mediated cellular arrest as an indicator of chemosensitivity to 5-fluorouracil

High expression of thymidylate synthase (TS) is allegedly associated with the chemoresistance to 5-fluorouracil (5-FU) in colorectal cancers. However, low TS expression does not necessarily imply chemosensitivity. Inactivation of p16(INK4a) correlates with poor prognosis in various cancers. We immunohistochemically evaluated the relationship between the expression of TS, p16(INK4a), CDK4 and cyclin D1 and the effect of 5-FU-based chemotherapy in colorectal cancers. After antigen retrieval, immunoperoxidase staining was performed on the paraffin-embedded, biopsy and surgical specimens of 37 advanced colorectal cancers preoperatively treated with peroral administration of 5-FU derivatives. As a control group, 31 colorectal cancers without preoperative treatment were analyzed. High TS expression was found in 23 (74%) of 31 tumors resected from histological non-responders and in 19 (61%) of 31 controls but in none of six responders. High p16(INK4a) expression was seen in 83% of the responders, 52% of the non-responders and 32% of the controls. The TS-low/p16(INK4a)-high phenotype was noted in 83% of the responders, but only in 3% of the non-responders (P = 0.0001). Induction of p16(INK4a) expression after chemotherapy was predominantly seen in the responders. Neither CDK4 nor cyclin D1 expression was related to the chemotherapeutic effects. In conclusion, the combination of low expression of TS and induction of p16(INK4a) after chemotherapy can be important indicators of the sensitivity to 5-FU-based chemotherapy in colorectal cancers.

DNA methylation and cancer

DNA methylation is an important regulator of gene transcription, and its role in carcinogenesis has been a topic of considerable interest in the last few years. Alterations in DNA methylation are common in a variety of tumors as well as in development. Of all epigenetic modifications, hypermethylation, which represses transcription of the promoter regions of tumor suppressor genes leading to gene silencing, has been most extensively studied. However, global hypomethylation has also been recognized as a cause of oncogenesis. New information concerning the mechanism of methylation and its control has led to the discovery of many regulatory proteins and enzymes. The contribution of dietary folate and methylene terahydrofolate reductase polymorphisms to methylation patterns in normal and cancer tissues is under intense investigation. As methylation occurs early and can be detected in body fluids, it may be of potential use in early detection of tumors and for determining the prognosis. Because DNA methylation is reversible, drugs like 5'-azacytidine, decitabine, and histone deacetylase inhibitors are being used to treat a variety of tumors. Novel demethylating agents such as antisense DNA methyl transferase and small interference RNA are being developed, making the field of DNA methylation wider and more exciting.

Reduced expression of cell cycle regulator p18(INK4C) in human hepatocellular carcinoma

Cyclins, cyclin-dependent kinases (Cdks), and Cdk inhibitors (CdkIs) are frequently altered in human cancer. p18INK4C, a member of the INK4 family of CdkIs, is a potential tumor-suppressor gene product. However, the expression of p18INK4C in hepatocellular carcinoma (HCC) remains unknown. The aim of this study was to examine the expression of p18INK4C in various liver diseases including HCC and to assess its clinical significance in HCC. To that end, we examined the expression of p18INK4C by immunohistochemistry in various liver diseases, including 51 HCCs, and also studied the relationship between p18INK4C expression, the phosphorylation of retinoblastoma protein (pRb), and the activity level of Cdk4 and Cdk6. Immunohistochemical analysis revealed the frequent loss of p18INK4C expression in HCC, especially in poorly differentiated HCC. The loss of p18INK4C expression was shown to be associated with a poor prognosis compared with that associated with p18INK4C- positivity. Further, the kinase activity of Cdk4 was found to be higher in p18INK4C-negative HCCs than in p18INK4C- positive HCCs. However, the level of Cdk6 activity was similar in the 2 groups of HCCs. In p18INK4C- positive HCCs, p18INK4C dominantly interacted with Cdk4 rather than with Cdk6. pRb phosphorylated at serine(Ser) 780 was detected more frequently in p18INK4C - negative than in p18INK4C - positive HCCs. In conclusion, the loss of p18INK4C expression may play a role in the differentiation and development of HCC through the up-regulation of Cdk4 activity.

Physical activity interventions in the prevention and treatment of paediatric obesity: systematic review and critical appraisal

Interventions for prevention and treatment of childhood obesity typically target increases in physical activity and, more recently, reductions in physical inactivity (sedentary behaviour such as television viewing). However, the evidence base for such strategies is extremely limited. The main aim of the present review was to update the systematic review and critical appraisal of evidence in the light of the recent rapid expansion of research in this area. Randomised controlled trials (RCT) that targeted activity or inactivity, that followed up children or adolescents for at least 1 year and that included an objective weight-related outcome measure were included. Trials were appraised using previously published criteria (Harbour & Miller, 2001), and literature search strategies described previously (Reilly et al. 2002) were updated to May 2002. A total of four new RCT, two new systematic reviews and one meta-analysis were identified. The evidence base has increased markedly since the completion of earlier reviews, although high-quality evidence is still lacking. The evidence on childhood obesity prevention is not encouraging, although promising targets for prevention are now clear, notably reduction in sedentary behaviour. There is stronger evidence that targeting activity and/or inactivity might be effective in paediatric obesity treatment, but doubts as to the generalisability of existing interventions, and the clinical relevance of the interventions is unclear. Further research in settings outside the USA is urgently needed, and two ongoing RCT in Scotland are summarised.

Anatomic site distribution and clinic pathologic characteristics of colorectal cancer in young Chinese

AIM

To study the anatomic site distribution and pathologic characteristics of colorectal cancer (CRC) in young Chinese.

METHODS

A retrospective study was undertaken. Data were collected from 1 370 patients in Nan Fang Hospital from 1974 to 1999, including 309 patients younger than 40 years and 1 061 patients older than 40 years. The median age was 54 years. All patients with colorectal adenocarcinomas were diagnosed by histology and underwent surgery.

RESULTS

Overall, 22.3% (309/1370) of CRC patients were young people. The proportion of males in the young group was 57.0% vs 58.3% in the aged group (P>0.05, x² = 0.16). 24.1% of young group vs 25.1% of aged group had lesions in the proximal colon and 72.4% vs 71.2% had cancers located in distal colorectum (P>0.05, x² = 0.42). Adenocarcinoma was the most common histologic type in both groups. 71.5% of young group vs 83.4% of aged group was adenocarcinoma (P <0.01, x² = 18.09), 17.4% vs 12.0% was mucinous adenocarcinoma (P<0.05, x²=4.70) and 5.5% vs 1.1% was signet-ring cell carcinoma (P<0.01, x² = 30.20). 18.2% of young group vs 24.9% of aged group was early stage (Duke's stage A) and 81.9% vs 75.1% was advanced stage (Duke's stage B, C, D) (P <0.05, x² = 5.13). 20.9% of young group vs 11.1% of aged group was poor differentiation (P<0.01, x² = 14.75) and 59.5% vs 34.3% had lymphatic metastasis (P<0.01, x² = 53.25).

CONCLUSION

CRC of young people has no significant difference from middle-aged and old people in either gender distribution or anatomic site distribution, but the former has some clinical pathologic characteristics that are different from the latter. CRC in young people has relatively worse prognosis. The therapeutic effects depend on paying attention to these clinical pathologic characteristics and early diagnosis and early treatment.

Prognostic factors in 165 elderly colorectal cancer patients

AIM: To analyse the prognostic factors in 165 colorectal patients aged ≥ 70.

METHODS: One hundred and sixty-five elderly patients with colorectal cancer diagnosed by histology were entered into the retrospective study between 1994 and 2001. Patients were given optimal operation alone, chemotherapy after operation, or chemotherapy alone according to tumor stage, histology, physical strength, and co-morbid problems. Survival rate was calculated by Kaplan-Meier method, and compared with meaningful variances by Log-rank method. Prognostic factors were analyzed by Cox regression.

RESULTS: The 1, 2, 3, 4, 5 year survival rate (all-cause mortality) was 87.76%, 65.96%, 52.05%, 42.77%, 40.51%, respectively. The mean survival time was 41.89 ± 2.33 months (95%CI: 37.33-46.45 months), and the median survival time was 37 months. Univariate analysis showed that factors such as age, nodal metastasis, treatment method, Duke’s stage, gross findings, kind of histology, and degree of differentiation had influences on the survival rate. Multivariate analysis showed that factors such as treatment method, Duke’s stage, kind of histology and degree of differentiation were independent prognostic factors.

CONCLUSION: This study suggests that the prognosis of elderly colorectal cancer patients is influenced by several factors. Most of elderly patients can endure surgery and/or chemotherapy, and have a long-time survival and good quality of life.

Screening of human colorectal carcinoma associated antigen genes by SEREX

AIM

To screen and identify the human colorectal carcinoma associated antigen genes.

METHODS

Three human colorectal carcinoma cDNA phage expression libraries were constructed. They were screened from autologous and allogeneic sera of colorectal cancer patients by SEREX (serological identification of antigens by recombinant expression cloning). The sera were pre-absorbed by the extract E. coli XL1-blue. Four different serum-reactive cDNA clones were isolated by immunoscreening from a colon cancer-derived cDNA expression library. Positive clones were amplified by plate culture, the purified lambda phage DNA was cut by Sfi I restriction endonucleases and amplified with PCR in order to identify the insert size of cDNA by electrophresis.

RESULTS

Three cDNA phage expression libraries were constructed. The titer of library was 2.39×10⁶ nfu/L, 2.07×10⁶ nfu/L and 1.86×10⁶ nfu/L respectively, The range of the fragment length of exogenously inserted cDNA was between 0.5-4 kb, the average was 1.4 kb, 1.6 kb and 1.3 kb, respectively. Four gene clones were obtained by SEREX screening, the length of their insert fragments was 2.4 kb, 1.8 kb, 2.3 kb and 2.2 kb, respectively.

CONCLUSION

To screen and identify human colorectal carcinoma cDNA phage expression libraries by SEREX is a useful method to search for human colorectal carcinoma associated antigen genes. It is important for early diagnosis and research of recombinant vaccine for colorectal cancer.

Methylation and mutation analysis of p16 gene in gastric cancer

AIM: To study methylation, frequencies of homozygous deletion and mutation of p16 gene in gastric carcinoma.

METHODS: The methylation pattern in exon 1 and exon 2 of p16 gene was studied with polymerase chain reaction (PCR), using methylation sensitive restriction endonuclease HpaII and methylation insensitive restriction endonuclease MspI. PCR technique was used to detect homozygous deletions of exon 1 and exon 2 of p16 gene and single strand conformation polymorphism (SSCP) technique was used to detect the mutation of the gene.

RESULTS: Hypermethylation changes in exon 1 and exon 2 of p16 gene were observed in 25% and 45% of 20 gastric cancer tissues, respectively, while no methylation abnormality was found in normal tissues. The homozygous deletion frequency of exon 1 and exon 2 of p16 gene in 20 gastric cancer tissues was 20% and 10%, respectively. No mutation was found in exon 1 of p16 gene, while abnormal single strands were found in 2 (10%) cases in exon 2 as detected by SSCP.

CONCLUSION: The results suggest that hypermethylation and abnormality of p16 gene may play a key role in the progress of gastric cancer. Hypermethylation of exon 2 of p16 gene may have effects on the carcinogenesis of gastric mucosa and may be a later event.

Effects of p16 gene on biological behavious in hepatocellular carcimoma cells

AIM: To investigate the effects of p16 gene on biological behavious in hepatocellular carcinoma cells.

METHODS: HCC cell lines SNU-449 and HepG2.2.15 were infected respectively by a replication defective, recombinant retrovirus capable of producing a high level of p16 protein expression (pCLXSN-p16). G418 resistant stable p16 protein expression cell lines were selected. And the biological behaviours of the p16 gene transfected HCC cells were observed.

RESULTS: Initial in vitro experiments in HCC cell line SNU-449 with loss of p16 protein expression demonstrated the pCLXSN-p16 treatment significantly inhibited cell growth. But there was no treatment effect when the pCLXSN-p16 was used in another HCC cell line HepG2.2.15 which has positive p16 protein expression. Subsequent study in a nude mouse model demonstrated that the p16 gene transfected SNU-449 had a lower succeeding rate in the first time establishment of tumors and grew more slowly in the nude mice when compared with non-transfected SNU-449. Moreover, the nude mice inoculated with transfected SNU-449 had a longer surviving time than those inoculated with non-transfected SNU-449.

CONCLUSION: Our results show that the p16INK4a gene transfer can inhibit the proliferation and reduce the invasion ability of hepatocellular carcinoma.

Hypermethylation pathways to colorectal cancer. Implications for prevention and detection

Epigenetic changes play an important role in the development and progression of colorectal cancer. The best characterized of these changes is the promoter region methylation of CpG islands of genes that play key roles in this disease. These changes compliment and lead to genetic changes that are well established as central to colorectal cancer progression. They may also prove useful in molecular detection approaches.

Arterial chemotherapy of 5-fluorouracil and mitomycin C in the treatment of liver metastases of colorectal cancer

AIM: Regional chemotherapy using hepatic artery catheters is a good method of treating patients with colorectal cancer liver metastases. We investigated the survival of patients with liver metastases from colorectal cancer using 5-fluorouracil (5-FU) and mitomycin C Cthrough implantable hepatic arterial infusion port.

METHODS: Seventy-five patients with inoperable liver metastases from colorectal cancer were included between March, 1992 and November, 2001. We placed implantable hepatic arterial catheter (HAC) port by laparotomy.5-FU, 1000 mg/m²/d continuous infusion for five days every four weeks, was delivered in the hepatic arterial catheter through the port. Mitomycin C, 30 mg/m²/d infusion in the first day every cycle through the port. Response to the treatment was evaluated by serial determinations of plasma CEA and imaging techniques consisting of computerized tomography and sonography of liver.

RESULTS: Sixty-eight were performed hepatic artery chemotherapy and fifty-six were followed up among seventy-five HAC patients. Twenty-six patients (46.4%) have responded and 4 complete remission were achieved. Eight patients (14.3%) had stable liver metastases. Twenty-two patients (39.3%) were progressed with increased tumor size and number. Twenty-nine patients (51.8%) had a decreased serum CEA level, while 10 patients (17.9%) were stable and 17 patients (30.4%) had an increased serum CEA level. There were no operative death in this series. Complications, which occurred in 18 patients (32.1%), were as followed: hepatic artery thrombosis in 11, Upper gastric and intestinal bleeding in 3, liver abscess in 1, pocket infection in 1, cholangitis in 1, and hepatic artery pseudo-aneurysm in one patient.

CONCLUSION: Combined infusion of 5-FU and mitomycin C by hepatic artery catheter port is an effective treatment for liver metastases from colorectal cancer. The high response and lower complication rates prove the adjuvant treatment of colorectal cancer with this treatment.