Hereditary non-polyposis colorectal cancer: an updated review

Clinically Relevant Genes and Proteins Modulated by Tocotrienols in Human Colon Cancer Cell Lines: Systematic Scoping Review

The last decade has witnessed tremendous growth in tocotrienols (T3s) research, especially in the field of oncology, owing to potent anticancer property. Among the many types of cancers, colorectal cancer (CRC) is growing to become a serious global health threat to humans. Chemoprevention strategies in recent days are open to exploring alternative interventions to inhibit or delay carcinogenesis, especially with the use of bioactive natural compounds, such as tocotrienols. This scoping review aims to distil the large bodies of literature from various databases to identify the genes and their encoded modulations by tocotrienols and to explicate important mechanisms via which T3s combat CRC. For this scoping review, research papers published from 2010 to early 2021 related to T3s and human CRC cells were reviewed in compliance with the PRISMA guidelines. The study included research articles published in English, searchable on four literature databases (Ovid MEDLINE, PubMed, Scopus, and Embase) that reported differential expression of genes and proteins in human CRC cell lines following exposure to T3s. A total of 12 articles that fulfilled the inclusion and exclusion criteria of the study were short-listed for data extraction and analysis. The results from the analysis of these 12 articles showed that T3s, especially its γ and δ analogues, modulated the expression of 16 genes and their encoded proteins that are associated with several important CRC pathways (apoptosis, transcriptional dysregulation in cancer, and cancer progression). Further studies and validation work are required to scrutinize the specific role of T3s on these genes and proteins and to propose the use of T3s to develop adjuvant or multi-targeted therapy for CRC.

The identification of specific methylation patterns across different cancers

Abnormal DNA methylation is known as playing an important role in the tumorgenesis. It is helpful for distinguishing the specificity of diagnosis and therapeutic targets for cancers based on characteristics of DNA methylation patterns across cancers. High throughput DNA methylation analysis provides the possibility to comprehensively filter the epigenetics diversity across various cancers. We integrated whole-genome methylation data detected in 798 samples from seven cancers. The hierarchical clustering revealed the existence of cancer-specific methylation pattern. Then we identified 331 differentially methylated genes across these cancers, most of which (266) were specifically differential methylation in unique cancer. A DNA methylation correlation network (DMCN) was built based on the methylation correlation between these genes. It was shown the hubs in the DMCN were inclined to cancer-specific genes in seven cancers. Further survival analysis using the part of genes in the DMCN revealed high-risk group and low-risk group were distinguished by seven biomarkers (PCDHB15, WBSCR17, IGF1, GYPC, CYGB, ACTG2, and PRRT1) in breast cancer and eight biomarkers (ZBTB32, OR51B4, CCL8, TMEFF2, SALL3, GPSM1, MAGEA8, and SALL1) in colon cancer, respectively. At last, a protein-protein interaction network was introduced to verify the biological function of differentially methylated genes. It was shown that MAP3K14, PTN, ACVR1 and HCK sharing different DNA methylation and gene expression across cancers were relatively high degree distribution in PPI network. The study suggested that not only the identified cancer-specific genes provided reference for individual treatment but also the relationship across cancers could be explained by differential DNA methylation.

History and pathogenesis of lynch syndrome

Lynch syndrome is the familial clustering of colorectal and endometrial cancers. This syndrome is passed in an autosomal dominant fashion within families with defective mismatch repair as the genetic basis for cancer development in these patients. There remains a group of patients who fit clinical diagnostic criteria for an autosomal dominant familial cancer syndrome, which is phenotypically similar to Lynch syndrome, but for which no mismatch repair mutation is identified. Identification of alternate genetic mutations such as EPCAM and CHEK2 may explain the cancer risk in a small subset of these patients, but continuing work into the genetic basis of colorectal familial cancer syndromes is needed.

What are the best routes to effectively model human colorectal cancer?

Colorectal cancer (CRC) is the third most common cancer in the UK, with over 37,500 people being diagnosed every year. Survival rates for CRC have doubled in the last 30 years and it is now curable if diagnosed early, but still over half of all sufferers do not survive for longer than 5 years after diagnosis. The major complication to treating this disease is that of metastasis, specifically to the liver, which is associated with a 5 year survival of less than 5%. These statistics highlight the importance of the development of earlier detection techniques and more targeted therapeutics. The future of treating this disease therefore lies in increasing understanding of the mutations which cause tumourigenesis, and insight into the development and progression of this complex disease. This can only be achieved through the use of functional models which recapitulate all aspects of the human disease. There is a wide range of models of CRC available to researchers, but all have their own strengths and weaknesses. Here we review how CRC can be modelled and discuss the future of modelling this complex disease, with a particular focus on how genetically engineered mouse models have revolutionised this area of research.

Two novel germline mutations of MLH1 and investigation of their pathobiology in hereditary non-polyposis colorectal cancer families in China

AIM: To detect germline mutations of MLH1, and investigate microsatellite instability and expression of MLH1 in tumor tissues of hereditary non-polyposis colorectal cancer (HNPCC) with two novel germline mutations, and further investigate the pathobiology of the two novel mutations of MLH1.

METHODS: RNA was extracted from the peripheral blood of 12 patients from 12 different families that fulfilled the Amsterdam II Criteria for HNPCC. Germline mutations of MLH1 were determined by RT-PCR, followed by cDNA sequencing analysis. PCR-GeneScan analysis was used to investigate microsatellite instability with a panel of five microsatellite markers (BAT26, BAT25, D5S346, D2S123 and mfd15), along with immunohistochemical staining to detect the expression of MLH1 protein in two patients' tumor tissues with novel mutations.

RESULTS: Three germline mutations were found in four patients, one of the mutations has previously been reported, but the other two, CGC→TGC at codon 217 of exon 8 and CCG→CTG at codon 581 of exon 16, have not been reported. The two patients' tumor tissues with novel mutations had high-frequency microsatellite instability that showed more than two unstable loci, and both tumors lost their MLH1 protein expression.

CONCLUSION: The two novel germline mutations of MLH1 in HNPCC families i.e. CGC→TGC at codon 217 of exon 8 and CCG→CTG at codon 581 of exon 16, are very likely to have pathological significance.

Detection of germline mutations of hMLH1 and hMSH2 based on cDNA sequencing in China

AIM: To detect the germline mutations of hMLH1 and hMSH2 based on mRNA sequencing to identify hereditary non-polyposis colorectal cancer (HNPCC) families.

METHODS: Total RNA was extracted from peripheral blood of 14 members from 12 different families fulfilling Amsterdam criteria II. mRNA of hMLH1 and hMSH2 was reversed with special primers and heat-resistant reverse transcriptase. cDNA was amplified with expand long template PCR and cDNA sequencing analysis was followed.

RESULT: Seven germline mutations were found in 6 families (6/12, 50%), in 4 hMLH1 and 3 hMSH2 mutations (4/12, 33.3%); (3/12, 25%). The mutation types involved 4 missense, 1 silent and 1 frame shift mutations as well as 1 mutation in the non-coding area. Four out of the seven mutations have not been reported previously. The 4 hMLH1 mutations were distributed in exons 8, 12, 16, and 19. The 3 hMSH2 mutations were distributed in exons 1 and 2. Six out of the 7 mutations were pathological, which were distributed in 5 HNPCC families.

CONCLUSION: Germline mutations of hMLH1 and hMSH2 can be found based on cDNA sequencing so as to identify HNPCC family, which is highly sensitive and has the advantages of cost and time saving.

Risks and benefits of population-based genetic testing for Mendelian subsets of common diseases were examined using the example of colorectal cancer risk

OBJECTIVE

Genetic testing for adult-onset, common diseases is becoming more commonplace in clinical medicine. We modeled the proportions of hypothetic populations that would potentially benefit or suffer harm from widespread predisposition testing.

METHODS

Using the traditional two-by-two table from the discipline of epidemiology, we modeled three hypothetic populations using the example of genetic testing for hereditary colorectal cancer in three groups: the general population, a genetically increased-risk population, and a population at increased risk due to nongenetic factors.

RESULTS

We demonstrate that the potential benefits are increased and risks are reduced when testing is limited to those at increased genetic risk when compared with testing in the general population. Where disease incidence is increased due to nongenetic factors, genetic testing has the potential to detract from the detection and reduction of other potentially important risk factors.

CONCLUSION

While targeted testing can benefit those truly at increased risk, broadly applied genetic testing can do more harm than good.

Lynch syndrome: implications for the surgeon

Hereditary nonpolyposis colorectal cancer (HNPCC), or Lynch syndrome, is an autosomal dominant syndrome characterized by onset of colorectal cancer (CRC) at an early age, right-sided predominance, excess synchronous and metachronous colorectal neoplasms, and extracolonic neoplasms. It is the most common of the hereditary CRCs, so the practicing surgeon should expect to encounter patients with this disease. The diagnosis of HNPCC, which begins with a complete family history and a high index of suspicion by the clinician, has important implications in the management and surveillance of not only the affected individual but also for the individual's family. In this article, the diagnosis and management of Lynch syndrome will be reviewed, with emphasis on the implications for the surgeon.

Timing and extent of surgical intervention in patients from hereditary pancreatic cancer kindreds

Our knowledge of the molecular and genetic etiology of hereditary pancreatic cancer has expanded considerably and is steadily increasing. However, there are only a few hard data available regarding the clinical and surgical management of these patients. Surgery is currently performed when we detect dysplastic changes in the pancreas or when cancer is suspected. Of the available diagnostic modalities, endoscopic ultrasonography has proven so far to be the most useful for detecting dysplastic changes in the pancreases of patients from hereditary pancreatic cancer kindreds. It seems reasonable, once dysplasia has been diagnosed in a high-risk patient, to proceed to total pancreatectomy. The multifocal nature of dysplastic lesions precludes any type of operation that would leave behind pancreatic tissue. Currently, prophylactic whole-organ resection in the absence of premalignant lesions cannot be recommended since we do not know the exact risk for the development of cancer.

Familial and inherited colorectal cancer: endoscopic screening and surveillance

Familial risk of colorectal cancer is very common. The high-risk inherited syndromes are well described and much is known about the genetics and the effectiveness of registration, endoscopic surveillance, and appropriate intervention in these patients. The inherited syndromes, however, are extremely rare. There is a large group of patients in our population who can benefit from risk stratification based on the number of their relatives with colon cancer or adenomas and the age at which those relatives developed neoplasm. The GI endoscopist has a vital role in recommending and providing colonoscopic screening for this large group of patients.

Clinicopathological and molecular genetic analysis of 4 typical Chinese HNPCC families

AIM: To study the clinicopathological and mole cular genetic characteristics of typical Chinese hereditary nonpolyposis cotorectal cancer (HNPCC) families.

METHODS: Four typical Chinese HNPCC families were analyzed using microdissection, microsatellite instability analysis, immunostaining of hMSH2 and hMLH1 proteins and direct DNA sequencing of hMSH2 and hMLH1 genes.

RESULTS: All five tumor tissues of 4 probands from the 4 typical Chinese HNPCC families showed microsatellite instability at more than two loci (MSI-H or RER+ phenotype). Three out of the 4 cases lost hMSH2 protein expression and the other case showed no hMLH1 protein expression. Three pathological germline mutations (2 in hMSH2 and 1 in hMLH1), which had not been reported previously, were identified. The same mutations were also found in other affected members of two HNPCC families, respectively.

CONCLUSION: Typical Chinese HNPCC families showed relatively frequent germline mutation of mismatch repair genes. High-level microsatellite instability and loss of expression of mismatch repair genes correlated closely with germline mutation of mismatch repair genes. Microsatellite instability analysis and immunostaining of mismatch repair gene might serve as effective screening methods before direct DNA sequencing. It is necessary to establish clinical criteria and molecular diagnostic strategies more suitable for Chinese HNPCC families.