J J Y Sung

Differential expression of microRNAs in plasma of patients with colorectal cancer: a potential marker for colorectal cancer screening

Objective: MicroRNAs (miRNAs) have been shown to offer great potential in the diagnosis of cancer. We investigated whether plasma miRNAs could discriminate between patients with and without colorectal cancer (CRC). Methods: This study was divided into three phases: (1) marker discovery using real-time PCR-based miRNA profiling on plasma, corresponding cancerous and adjacent non-cancerous colonic tissues of five patients with CRC, along with plasma from five healthy individuals as controls; (2) marker selection and validation by real-time quantitative RT-PCR on a small set of plasma; and (3) independent validation on a large set of plasma from 90 patients with CRC, 20 patients with gastric cancer, 20 patients with inflammatory bowel disease (IBD) and 50 healthy controls. Results: Of the panel of 95 miRNAs analysed, five were upregulated both in plasma and tissue samples. All the five miRNAs were validated on the plasma of 25 patients with CRC and 20 healthy controls. Both miR-17-3p and miR-92 were significantly elevated in the patients with CRC (p<0.0005). The plasma levels of these markers were significantly reduced after surgery in 10 patients with CRC (p<0.05). Further validation with an independent set of plasma samples (n = 180) indicated that miR-92 differentiates CRC from gastric cancer, IBD and normal subjects. This marker yielded a receiver operating characteristic curve area of 88.5%. At a cut-off of 240 (relative expression in comparison to RNU6B snRNA), the sensitivity was 89% and the specificity was 70% in discriminating CRC from control subjects. Conclusion: MiR-92 is significantly elevated in plasma of patients with CRC and can be a potential non-invasive molecular marker for CRC screening.

Alanine aminotransferase-based algorithms of liver stiffness measurement by transient elastography (Fibroscan) for liver fibrosis in chronic hepatitis B.

Summary.  The aim of this study is to know the liver stiffness measurement (LSM) cutoffs for different stages of liver fibrosis in chronic hepatitis B (CHB) and to investigate the effect of alanine aminotransferase (ALT) on LSM. We prospectively studied consecutive CHB patients undergoing liver biopsy and transient elastography examinations. Diagnostic performance of LSM for different degrees of liver fibrosis was evaluated. One hundred and sixty‐one CHB patients with adequate liver biopsy sample size were studied. Area under receiver operating characteristics curves of LSM for no fibrosis (F0 vs F1–4), bridging fibrosis (F0–2 vs F3–4) and liver cirrhosis (F0–3 vs F4) was 0.80 (95% CI: 0.68–0.92), 0.87 (95% CI: 0.82–0.93) and 0.93 (95% CI: 0.89–0.97) respectively. For liver cirrhosis, these optimal cutoff values were 8.4 kPa (98% sensitivity), 9.0 kPa (maximum sum of sensitivity and specificity), 13.4 kPa (94% specificity) and 13.4 kPa (maximum diagnostic accuracy, 85%) respectively. Patients with the same fibrosis staging but higher ALT levels tend to have higher LSM, and the diagnostic performance for low stage fibrosis was most seriously affected when ALT was elevated. Different LSM cutoff values and algorithms were derived for normal and elevated ALT levels. Based on these algorithms, liver biopsy can be avoided in 62% and 58% of patients with normal and elevated ALT respectively. In conclusion, transient elastography is a reasonable noninvasive tool to substitute liver biopsy among the lowest and highest risk patients for the assessment of liver fibrosis.

Asia Pacific consensus recommendations for colorectal cancer screening

Colorectal cancer (CRC) is rapidly increasing in Asia, but screening guidelines are lacking. Through reviewing the literature and regional data, and using the modified Delphi process, the Asia Pacific Working Group on Colorectal Cancer and international experts launch consensus recommendations aiming to improve the awareness of healthcare providers of the changing epidemiology and screening tests available. The incidence, anatomical distribution and mortality of CRC among Asian populations are not different compared with Western countries. There is a trend of proximal migration of colonic polyps. Flat or depressed lesions are not uncommon. Screening for CRC should be started at the age of 50 years. Male gender, smoking, obesity and family history are risk factors for colorectal neoplasia. Faecal occult blood test (FOBT, guaiac-based and immunochemical tests), flexible sigmoidoscopy and colonoscopy are recommended for CRC screening. Double-contrast barium enema and CT colonography are not preferred. In resource-limited countries, FOBT is the first choice for CRC screening. Polyps 5–9 mm in diameter should be removed endoscopically and, following a negative colonoscopy, a repeat examination should be performed in 10 years. Screening for CRC should be a national health priority in most Asian countries. Studies on barriers to CRC screening, education for the public and engagement of primary care physicians should be undertaken. There is no consensus on whether nurses should be trained to perform endoscopic procedures for screening of colorectal neoplasia.

NOD2/CARD15 gene polymorphisms and Crohn's disease in the Chinese population

Background: Crohns disease affects people world‐wide, but the incidence in Asia is lower than in Western countries. This difference may be due to genetic and/or environmental factors. Three single nucleotide polymorphisms (SNPs) of the NOD2/CARD15 gene have been identified to be independently associated with the development of Crohns disease in Caucasians. Whether these SNPs are involved in the pathogenesis of Crohns disease in the Chinese population is unknown.

MicroRNA dysregulation in gastric cancer: a new player enters the game

Gastric carcinogenesis is a multistep process involving genetic and epigenetic alteration of protein-coding proto-oncogenes and tumor-suppressor genes. Recent discoveries have shed new light on the involvement of a class of noncoding RNA known as microRNA (miRNA) in gastric cancer. A substantial number of miRNAs show differential expression in gastric cancer tissues. Genes coding for these miRNAs have been characterized as novel proto-oncogenes and tumor-suppressor genes based on findings that these miRNAs control malignant phenotypes of gastric cancer cells. In this connection, miRNA dysregulation promotes cell-cycle progression, confers resistance to apoptosis, and enhances invasiveness and metastasis. Moreover, certain polymorphisms in miRNA genes are associated with increased risks for atrophic gastritis and gastric cancer, whereas circulating levels of miRNAs may serve as biomarkers for early diagnosis. Several miRNAs have also been shown to correlate with gastric cancer progression, and thus may be used as prognostic markers. Elucidating the biological aspects of miRNA dysregulation may help us better understand the pathogenesis of gastric cancer and promote the development of miRNA-directed therapeutics against this deadly disease.

The autophagic paradox in cancer therapy.

Autophagy, hallmarked by the formation of double-membrane bound organelles known as autophagosomes, is a lysosome-dependent pathway for protein degradation. The role of autophagy in carcinogenesis is context dependent. As a tumor-suppressing mechanism in early-stage carcinogenesis, autophagy inhibits inflammation and promotes genomic stability. Moreover, disruption of autophagy-related genes accelerates tumorigenesis in animals. However, autophagy may also act as a pro-survival mechanism to protect cancer cells from various forms of cellular stress. In cancer therapy, adaptive autophagy in cancer cells sustains tumor growth and survival in face of the toxicity of cancer therapy. To this end, inhibition of autophagy may sensitize cancer cells to chemotherapeutic agents and ionizing radiation. Nevertheless, in certain circumstances, autophagy mediates the therapeutic effects of some anticancer agents. Data from recent studies are beginning to unveil the apparently paradoxical nature of autophagy as a cell-fate decision machinery. Taken together, modulation of autophagy is a novel approach for enhancing the efficacy of existing cancer therapy, but its Janus-faced nature may complicate the clinical development of autophagy modulators as anticancer therapeutics.

An updated Asia Pacific Consensus Recommendations on colorectal cancer screening

Objective Since the publication of the first Asia Pacific Consensus on Colorectal Cancer (CRC) in 2008, there are substantial advancements in the science and experience of implementing CRC screening. The Asia Pacific Working Group aimed to provide an updated set of consensus recommendations. Design Members from 14 Asian regions gathered to seek consensus using other national and international guidelines, and recent relevant literature published from 2008 to 2013. A modified Delphi process was adopted to develop the statements. Results Age range for CRC screening is defined as 50–75 years. Advancing age, male, family history of CRC, smoking and obesity are confirmed risk factors for CRC and advanced neoplasia. A risk-stratified scoring system is recommended for selecting high-risk patients for colonoscopy. Quantitative faecal immunochemical test (FIT) instead of guaiac-based faecal occult blood test (gFOBT) is preferred for average-risk subjects. Ancillary methods in colonoscopy, with the exception of chromoendoscopy, have not proven to be superior to high-definition white light endoscopy in identifying adenoma. Quality of colonoscopy should be upheld and quality assurance programme should be in place to audit every aspects of CRC screening. Serrated adenoma is recognised as a risk for interval cancer. There is no consensus on the recruitment of trained endoscopy nurses for CRC screening. Conclusions Based on recent data on CRC screening, an updated list of recommendations on CRC screening is prepared. These consensus statements will further enhance the implementation of CRC screening in the Asia Pacific region.

microRNA-7 is a novel inhibitor of YY1 contributing to colorectal tumorigenesis

Using microRNA (miRNA) expression array, we identified that miR-7 was deregulated in colorectal cancer (CRC). We studied the biological role and molecular target of miR-7 in CRC. miR-7 was downregulated in six out of seven colon cancer cell lines. Ectopic expression of miR-7 suppressed colon cancer cell proliferation (P<0.05), induced apoptosis (P<0.05) and caused cell-cycle arrest in G1 phase (P<0.05). The tumor suppressive function of miR-7 was further confirmed in nude mice (P<0.05). The 3′-untranslated region (3′UTR) of Yin Yang 1 (YY1) mRNA contains an evolutionarily conserved miR-7 binding site using in silico searches, luciferase reporter assay and western blot analysis confirmed that miR-7 directly bound to YY1 3′UTR to negatively regulate the protein expression of YY1 in colon cancer cell lines HCT116 and LOVO. Intriguingly, knock-down of YY1 in three colon cancer cell lines (HCT116, LOVO and DLD1) consistently suppressed cell proliferation (P<0.01) and induced apoptosis (P<0.01), indicating the opposite functions of miR-7 and YY1 in CRC. Consistent with these data, ectopic expression of YY1 promoted cell growth by increasing proliferation (P<0.01) and suppressing apoptosis (P<0.001). The tumorigenic ability of YY1 was further confirmed in vivo in xenograft-nude mouse model (P<0.01). In addition, pathway analyses revealed that the oncogenic effect by YY1 was associated with inhibiting p53 and modulating its downstream effectors p15, caspase cascades and C-Jun, and activating Wnt signaling pathway through activating β-catenin, anti-apoptotic survivin and fibroblast growth factor 4. Furthermore, multivariate analysis revealed that patients with YY1 protein high expression had a significant decrease in overall survival, and Kaplan–Meier survival curves showed that these patients had significantly shorter survival than others (P<0.0001). In conclusion, MiR-7 is a novel miRNA with tumor suppressive function in colon cancer by targeting oncogenic YY1. YY1 promotes colon cancer growth through inhibiting p53 and promoting Wnt signaling pathways and serves as an independent prognostic biomarker for CRC patients.

Frequent epigenetic inactivation of secreted frizzled-related protein 2 (SFRP2) by promoter methylation in human gastric cancer

The role of secreted frizzled-related protein (SFRP) genes in gastric cancer remains largely unknown. We determined the frequency and functional significance of SFRPs hypermethylation in human gastric cancer. The expression and methylation status of four SFRP members (SFRP1, 2, 4, and 5) in primary gastric cancer samples was screened. The biological effects of SFRP were analysed by flow cytometry, cell viability assay and in vivo tumour growth in nude mice. Among the four SFRPs, only SFRP2 was significantly downregulated in gastric cancer as compared to adjacent non-cancer samples (P<0.01). Promoter hypermethylation of SFRP2 was detected in 73.3% primary gastric cancer tissues, 37.5% of samples showing intestinal metaplasia and 20% adjacent normal gastric tissues. Bisulphite DNA sequencing confirmed the densely methylated SFRP2 promoter region. Demethylation treatment restored the expression of SFRP2 in gastric cancer cell lines. Forced expression of SFRP2 induced cell apoptosis, inhibited proliferation of gastric cancer cells and suppressed tumour growth in vivo. Moreover, methylated SFRP2 was detected in 66.7% of serum samples from cancer patients but not in normal controls. In conclusion, epigenetic inactivation of SFRP2 is a common and early event contributing to gastric carcinogenesis and may be a potential biomarker for gastric cancer.

MicroRNA dysregulation in colorectal cancer: a clinical perspective

Recent researches have shed light on the biological importance of microRNAs (miRNAs) in colorectal cancer (CRC) genesis, progression and response to treatments. The potential utility of miRNAs in the preclinical stage have been explored and investigated. In this review, we explored the literature and reviewed the cutting edge progress in the discovery of noninvasive plasma and faecal miRNAs for CRC early diagnosis, as well as their measurability and predictability. We also discussed the utility of miRNAs as novel prognostic and predictive markers, and their association with CRC clinical phenotypes including recurrence, metastasis and therapeutic outcomes. Finally, we summarised miRNA-related single-nucleotide polymorphisms and their potential influence on sporadic CRC susceptibility and therapeutic response. In conclusion, the use of miRNAs as biomarker for CRC is still in its infancy and need further characterisation and evaluation.