Genetics of colorectal polyps

Oncogene and Tumor Suppressor Gene Expression Changes in the Peripheral Blood Leukocytes of Patients with Colorectal Cancer

Aims and background

The mortality of colorectal cancer continues to stagnate despite the development of new therapeutic approaches. Therefore, identifying high-risk population groups could contribute to the prevention of a considerable part of deaths caused by colorectal tumors.

Methods

Fifty patients with colon cancer and 50 patients with other, nonmalignant diseases were selected for the study. Expression of the c-myc, Ha-ras and p53 genes was determined in the peripheral leukocytes of the participants.

Results

Marked elevations of the expression of all three investigated genes were seen in the colon cancer patients when compared to the controls.

Conclusions

Our investigations showed that increases in the expression of c-myc, Ha-ras and p53 genes can be demonstrated in the peripheral leukocytes of colon cancer patients. By applying our method to clinical investigations, individuals with a high risk of having developed colon cancer may be identified and early diagnosis may be established.

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.

Management of colorectal T1 carcinoma treated by endoscopic resection from the Western perspective

Detection of early colorectal cancer is expected to rise in light of national colorectal cancer screening programs. This The present review article delineates current endoscopic risk assessments, differentiating invasive from non-invasive neoplasia, for high likelihood of lymph node metastasis in early colorectal cancer, also termed high-risk early colorectal cancer, and endoscopic and surgical resection methods from a Western hemisphere perspective.

Genome-wide copy number changes and CD133 expression characterized distinct subset of colon polyps: differentiation between incidental polyps and cancer-associated polyps

PURPOSE

Colorectal polyps are generally believed to be the precursors of colorectal cancers (CRC); however, the proportion and speed of progression differed widely in different subsets of polyps. Using microarray-based comparative genomic hybridization (aCGH) platform and CD133 immunostaining, we characterized colon polyps according to their association with CRC that developed in the same individual.

PATIENTS AND METHODS

aCGH was performed to unveil genomic changes in 18 cancer-synchronous polyps (CSP), and 9 cancer-preceding polyps (CPP), together with their corresponding cancers and 16 cases of incidental polyps (IP), were examined for comparison. aCGH profiles were analyzed to determine the clonal relationship (CR) between the paired adenoma and carcinoma. CD133 expressions in each subset of polyps were quantified by immunohistochemistry (IHC) staining.

RESULTS

Progressive genomic changes were observed from IP, CSP/CPP to CRC; they encompass an entire chromosomal region in IP and sub-chromosomal region in CSP/CPP and CRC. CR analyses demonstrated that 50 % of CSP and 67 % of CPP were clonally related to the concurrent or later developed carcinomas, respectively. The CD133 expression levels were significantly higher in CSP/CPP than those in IP (P < 0.0001) and even higher in CSP/CPP that were clonally related to their corresponding carcinomas than CSP/CPP that were unrelated (P < 0.05).

CONCLUSIONS

There were more genomic changes in CSP/CPP than IP; more than half of the CSP/CPP were clonally related to the corresponding carcinomas. Genomic changes at sub-chromosomal regions and/or high CD133 expression were associated with CSP/CPP and highlighted their carcinogenic potential.

Management of malignant colon polyps: Current status and controversies

Colon cancer remains a significant clinical problem worldwide and in the United States it is the third most common cancer diagnosed in men and women. It is generally accepted that most malignant neoplasms of the colon arise from precursor adenomatous polyps. This stepwise progression of normal epithelium to carcinoma, often with intervening dysplasia, occurs as a result of multiple sequential, genetic mutations-some are inherited while others are acquired. Malignant polyps are defined by the presence of cancer cells invading through the muscularis mucosa into the underlying submucosa (T1). They can appear benign endoscopically but the presence of malignant invasion histologically poses a difficult and often controversial clinical scenario. Emphasis should be initially focused on the endoscopic assessment of these lesions. Suitable polyps should be resected en-bloc, if possible, to facilitate thorough evaluation by pathology. In these cases, proper attention must be given to the risks of residual cancer in the bowel wall or in the surrounding lymph nodes. If resection is not feasible endoscopically, then these patients should be referred for surgical resection. This review will discuss the important prognostic features of malignant polyps that will most profoundly affect this risk profile. Additionally, we will discuss effective strategies for their overall management.

Clinicopathological significance of PTEN loss and the phosphoinositide 3-kinase/Akt pathway in sporadic colorectal neoplasms: is PTEN loss predictor of local recurrence?

BACKGROUND

PTEN is a tumor-suppressor gene located on chromosome 10. Deficient PTEN expression leads to activation of the phosphoinositide 3-kinase (PI3K)/Akt (pAkt) signaling pathway, which may contribute to multiple human cancers. The relation between PTEN expression and Akt activation is still unclear in colorectal cancers and adenomatous polyps. Moreover, PTEN and pAkt expression in relation to demographic, tumoral, and outcome variables remains to be elucidated.

METHODS

PTEN and pAkt expression were evaluated in 76 primary colorectal cancers and 25 adenomatous colorectal polyp tissues using immunohistochemical staining on paraffin-embedded sections. PTEN and pAkt expression were compared with clinicopathologic features of colorectal cancers. The relationship between PTEN and pAkt expression was also investigated.

RESULTS

In colorectal cancers, pAkt expression was found to be significantly higher than polyps (P = .007). On the other hand, PTEN expression was significantly lower in polyps (P <.0001). In colorectal cancer patients, PTEN expression showed a negative correlation with young age, female sex, and left-sided (distal) tumors. On multivariate analysis, low PTEN expression (PTEN loss) was noted as an independent parameter for local recurrence (P = .024). There was significant association between pAkt expression and stage (P = .008), and preoperative serum carcinoembryonic antigen (CEA) levels (P = .017) in colorectal cancers. A negative correlation between PTEN and pAkt expression was found in colon cancer patients (P = .010), whereas no significiant association was found in adenomatous polyps (P = .403). No correlation of PTEN expression or pAkt expression was observed in Kaplan-Meier survival statistics and multivariate analyses for disease-free and overall survival.

CONCLUSIONS

The current study suggests that the PTEN loss-PI3K/pAkt pathway may play an important role in sporadic colon carcinogenesis and that reduced PTEN expression may predict relapse in colorectal cancer patients.

Association of colorectal adenoma with other malignancies in Swedish families

Using the Swedish Family-Cancer Database covering over 11.5 million individuals, estimated relative risks (RRs) for colorectal adenoma were using Poisson's regression. The RR of colorectal adenoma was found to be increased among first-degree relatives of patients with colorectal cancer (2.72; 95% confidence interval=2.46-3.00) and among the offspring and siblings of patients with endometrial and prostate cancers. We also found an increased risk of colorectal adenoma for the offspring of individuals with stomach cancer and leukaemia, and for siblings of those with pancreatic cancer and multiple myeloma. Our results suggest that colorectal adenoma may share a genetic aetiology with cancer even at extracolorectal sites. Increases of colorectal adenoma in families affected by prostate cancer and acute leukaemia cannot be attributed to known cancer syndromes, although the play of chance cannot be excluded.

Progression of tumors arising from large ACF is associated with the MUC5AC expression during rat colon MNNG carcinogenis

Aberrant crypt foci (ACF) are microscopic lesions which have been postulated to precede the development of adenomas, precursors of colon cancer. The gastric M1/MUC5AC mucin has also been described as an early marker of colon carcinogenesis in the human and in the rat. To study changes in mucin expression associated with the genesis of tumors, Wistar rats were treated by intrarectal instillations of MNNG, twice a week for 2 weeks, and were sacrificed 10 (n = 20), 14 (n = 20), 22 (n = 20), 30 (n = 10) and 66 (n = 16) weeks after the beginning of the treatment. In the treated rats, the MUC5AC mucin was mainly expressed in ACF compared with the histologically normal mucosae, which showed few isolated MUC5AC-positive normal crypts. During carcinogenesis, the percentage of large ACF [> or =10 aberrant crypts] increased and the number of MUC5AC-positive (NCs) decreased. At Week 30, small tumors were observed arising from large ACF, both types of lesions expressing MUC5AC. At Week 66, large tumors showed remnants of MUC5AC-positive ACF in their adjacent mucosae. This observation suggests that the expression of MUC5AC is associated with the ACF/adenoma sequence and supports the notion of large ACF as precursors of adenomas/adenocarcinomas. Moreover, the expression of MUC5AC in the transitional mucosa adjacent to both rat and human colon tumors suggests that some human tumors could arise from large ACF, and reinforces the concept of the premalignant potential of these lesions.