Colorectal advanced neoplasms occur through dual carcinogenesis pathways in individuals with coexisting serrated polyps

Expression of Parkin, APC, APE1, and Bcl-xL in Colorectal Polyps

Colorectal cancer can develop through molecular, chromosomal, and epigenetic cumulative changes that transform the normal intestinal epithelium into the colorectal polyps, called conventional adenomas (CAs) or serrated polyps (SPs), recognized as precursors of invasive colorectal neoplasia. These benign lesions need to explore the morphology, histological diagnosis, and biomarkers profile to accurately characterize lesions with potential for evolution to cancer. This study aimed to correlate the immunohistochemical expression of Parkin and Adenomatous Polyposis Coli (APC; tumor suppressors), Human Apurinic/Apyrimidinic endonuclease 1 (APE1), and B-cell lymphoma-extra-large (Bcl-xL; oncogenic proteins) in sporadic colorectal polyps with clinical, endoscopic, and diagnostic data. Immunohistochemical analysis was performed on tissue microarray samples of 306 polyps. Based on the Allred score, the expressions were graduated in the cytoplasm and nucleus of superficial and cryptic cells. There was higher Parkin nuclear expression (p=0.006 and 0.010) and APC cytoplasmic expression in cryptic cells (p<0.001) in SPs. CAs, APE1 (p<0.001) and Bcl-xL (p<0.001) were more expressed in the nuclei and cytoplasms, respectively. These results are related to the biological role proposed for these proteins in cellular functions. They can contribute to the diagnosis criteria for polyps and improve the knowledge of biomarkers that could predict cancer development.

Critical Role of p53 and K-ras in the Diagnosis of Early Colorectal Cancer: a One-year, Single-center Analysis

Background: Colorectal cancer (CRC) is strongly associated with colorectal polyps, which has become the third most common cancer in China. In the present study, we revealed the susceptible population and risk factors of colorectal polyps, and analyzed the expression of Ki-67, p53 and K-ras in the intestinal mucosa of patients with colorectal polyps in order to explore their significance in the detection and prognosis of CRC at an early stage. Materials and Methods: Total 801 cases of colorectal polyps were collected during endoscopic resection including endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD). Expression of Ki-67, p53 and K-ras in the intestinal mucosa was detected by immunohistochemistry and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. Histological analysis was performed by Hematoxylin and eosin (HE) staining. Categorical variables were compared by one-way ANOVA, Pearson test, Spearman test, Kruskal-Wallis test and analysis of regression. Results: Of all patients with colorectal polyps, 90.76% of patients (n = 727) were ≥ 50 years old. 530 cases (66.17%) were males compared with 271 females (33.83%) in all 801 cases. More importantly, 1.03% patients (n = 7) underwent polypectomy and histological examination was confirmed to be the early stage of CRC. The expression of p53 was found to be significantly decreased, while K-ras was increased in tumor tissues of CRC compared with that in hyperplastic polyps and healthy controls. Conclusions: 1.03% patients (n = 7) underwent polypectomy was confirmed to be the early stage of CRC. Histological analysis for expression of p53 and K-ras can guarantee to screen the early stage of CRC.

Tumor LINE-1 Methylation Level in Association with Survival of Patients with Stage II Colon Cancer

Genome-wide DNA hypomethylation is associated with a worse prognosis in early-stage colorectal cancer. To measure genome-wide DNA methylation levels, long interspersed nucleotide element (LINE-1) repeats are used as a surrogate marker. Cohort studies on the clinical impact of genome-wide DNA methylation level in patients with only early-stage colon cancer, are currently lacking. This study aimed to investigate the prognostic value of LINE-1 methylation in a stage II colon cancer cohort (n = 164). Manual needle microdissection of tumor areas was performed on formalin-fixed paraffin-embedded tumor tissue sections followed by DNA extraction. Bisulfite converted DNA was used to assess tumor LINE-1 methylation level by qPCR. Patients with LINE-1 hypomethylated tumors had a significantly worse overall survival compared to patients with a higher level of LINE-1 tumor DNA methylation (HR 1.68, 95% CI 1.03–2.75; p = 0.04). This effect was more prominent in patients aged over 65 years (HR 2.00, 95% CI 1.13–3.52; p = 0.02), although the test for age interaction was not significant. No significant effect on recurrence-free survival was observed. Based on these results, tumor LINE-1 hypomethylation is associated with a worse overall survival in stage II colon cancer. Whether the origin of this causation is cancer-specific or age-related can be debated.

LINE-1 hypomethylation in normal colon mucosa is associated with poor survival in Chinese patients with sporadic colon cancer

Genetic and epigenetic pathways are not independent in colorectal cancer (CRC) carcinogenesis. We aimed to determine the influence of various molecular features on Chinese patients' colon cancer-specific survival (CCSS). Various genetic and epigenetic modifications were detected in paired tumor and normal mucosa tissue samples. The prognostic variables regarding patient CCSS were determined. Overall, 127 patients, including 83 males and 44 females, completed a median follow-up of 65 (3–85) months. A mean LINE-1 methylation rate of 64.62% (range, 9.45–86.93) was observed. Hypermethylation at the hMLH1 gene promoter was detected in 26 (20.47%) patients. KRAS was mutated in 52 (40.94%) patients. Sixteen (12.60%) patients were confirmed as microsatellite instability (MSI)-High, and 76 (59.84%) were found to have loss of heterozygosity at 18q. The LINE-1 methylation level, MSI status, perineural invasion and distant metastases were confirmed as independent prognostic factors for patient CCSS. A stratified survival analysis further revealed that certain subgroups of patients with LINE-1 hypomethylation had significantly worse survival (all p < 0.05). Our data revealed that both genetic and epigenetic abnormalities can concurrently exist during colonic tumorigenesis. As a global epigenetic change, LINE-1 hypomethylation in normal colon mucosa might be associated with a worse outcome in certain Chinese patients with colon cancer.

Serrated polyposis associated with a family history of colorectal cancer and/or polyps: The preferential location of polyps in the colon and rectum defines two molecular entities

Serrated polyposis (SPP) is characterized by the development of multiple serrated polyps and an increased predisposition to colorectal cancer (CRC). In the present study, we aimed to characterize, at a clinical and molecular level, a cohort of SPP patients with or without a family history of SPP and/or polyps/CRC (SPP-FHP/CRC). Sixty-two lesions from 12 patients with SPP-FHP/CRC and 6 patients with sporadic SPP were included. The patients with SPP-FHP/CRC presented with an older mean age at diagnosis (p=0.027) and a more heterogeneous histological pattern of lesions (p=0.032) than the patients with sporadic SPP. We identified two molecular forms of SPP-FHP/CRC, according to the preferential location of the lesions: proximal/whole-colon or distal colon. Mismatch repair (MMR) gene methylation [mutS homolog 6 (MSH6)/mutS homolog 3 (MSH3)] or loss of heterozygosity (LOH) of D2S123 (flanking MSH6) were detected exclusively in the former (p=3.0×10⁻⁷), in most early lesions. Proximal/whole-colon SPP-FHP/CRC presented a higher frequency of O-6-methylguanine-DNA methyltransferase (MGMT) methylation/LOH, microsatel-lite instability (MSI) and Wnt mutations (19/29 vs. 7/17; 16/23 vs. 1/14, p=2.2×10⁻⁴; 15/26 vs. 2/15, p=0.006; 14/26 vs. 4/20, p=0.02) but a lower frequency of B-raf proto-oncogene, serine/threonine kinase (BRAF) mutations (7/30 vs. 12/20, p=0.0089) than the distal form. CRC was more frequent in cases of Kirsten rat sarcoma viral oncogene homolog (KRAS)-associated proximal/whole-colon SPP-FHP/CRC than in the remaining cases (4/4 vs. 1/8, p=0.01). Thus, SPP-FHP/CRC appears to be a specific entity, presenting two forms, proximal/whole-colon and distal, which differ in the underlying tumor initiation pathways. Early MGMT and MMR gene deficiency in the former may underlie an inherited susceptibility to genotoxic stress.

Association between nonalcoholic fatty liver disease and colorectal adenoma: a systematic review and meta-analysis

BACKGROUND AND AIMS

Several existing studies indicated that nonalcoholic fatty liver disease (NAFLD) may be associated with colorectal adenoma, but the results and risk factors are controversial. A systematic review of studies was conducted to explore these issues by meta-analysis.

METHODS

We searched the Pubmed, Embase, Cochrane library, Medline and Web of Science databases for studies published before May 30(th), 2014. A statistical analysis was performed using RevMan 5.2 software.

RESULTS

Seven studies involving 11,905 participants from different regions were included. Among them, five trials carried out subgroup of NAFLD patients in colorectal adenoma population. The result showed NAFLD was significantly correlated with adenoma of colon (Odds ratio [OR] = 1.56, 95% confidence interval [CI]: 1.22-1.99, P = 0.0003). It could be found in stratified analysis that patients had more chance to get multiple adenomas when they suffered NAFLD (Rate ratio [RR]: 1.52, 95% CI: 1.08-2.13, P = 0.02). Such risk factors of NAFLD as age, waist circumference, body mass index (BMI), disorder of lipid metabolism, hyperglycemia and high blood pressure (HBP) increased risk of colorectal adenoma (Age: mean difference [MD]: 2.81, 95% CI: 0.33-5.28; Waist: MD: 2.84, 95% CI: 2.14-3.54; BMI: MD: 0.85, 95% CI: 0.69-1.01; High-density lipoprotein: MD: -2.46, 95% CI: -3.68 to -1.24; Triglyceride: MD: 16.12, 95% CI: 8.89-23.36; Low-density lipoprotein: MD: 6.04, 95% CI: 3.60-8.48; Cholesterol: MD: 4.25, 95% CI: 0.87-7.63; Fasting glucose: MD: 2.27, 95% CI: 1.24-3.30; HBP: OR = 1.51, 95% CI: 1.22-1.88), while diabetes had no significant association with it (OR = 1.43, 95% CI: 0.94-2.17, P = 0.09). Besides, NAFLD didn't affect the location, size and advanced type of colorectal adenoma (P > 0.05).

CONCLUSION

The present systematic review and meta-analysis demonstrated NAFLD was closely associated with great risk of colorectal adenoma and its number, but not with its location, size and advanced type. Waist, obesity, lipid profiles, glucose, hypertension played roles in the process of colorectal adenoma.

LINE-1 hypomethylation is neither present in rectal aberrant crypt foci nor associated with field defect in sporadic colorectal neoplasia

Background

Aberrant crypt foci (ACF) are considered the first identifiable preneoplastic lesion in colorectal cancer (CRC), and have been proposed as a potential biomarker for CRC risk. Global DNA hypomethylation is an early event in colorectal carcinogenesis, and long interspersed nuclear element-1 (LINE-1) methylation status is a well-known surrogate marker for genome-wide DNA methylation levels. Despite the gradual increase in DNA hypomethylation in the adenoma–carcinoma sequence, LINE-1 methylation in ACF has never been studied. Moreover, recent studies have reported a field defect for LINE-1 hypomethylation, suggesting that LINE-1 methylation status in normal mucosa could be used to stratify CRC risk and tailor preventive strategies. Thus, we assessed LINE-1 status by pyrosequencing in rectal ACF and paired normal colorectal mucosa from individuals with sporadic colon cancer (CC) (n = 35) or adenoma (n = 42), and from healthy controls (n = 70).

Findings

Compared with normal mucosa, LINE-1 in ACF were hypermethylated across all groups (P < 0.0001). Furthermore, LINE-1 methylation status in normal colorectal mucosa was independent of the presence of adenoma or CC (P = 0.1072), and did not differ depending on the distance to the adenoma or CC. Interestingly, when we compared the LINE-1 methylation status in normal mucosa from different segments of the colorectum, we found higher hypomethylation in the rectum compared with the descending colon (P < 0.0001).

Conclusions

Overall, our results suggest that global hypomethylation is not present in rectal ACF and argues against the existence of LINE-1 methylation field defect in sporadic colon cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/1868-7083-6-24) contains supplementary material, which is available to authorized users.