Epigenetics of colorectal cancer

Forkhead box E1, frequently downregulted by promoter methylation, inhibits colorectal cancer cell growth and migration

Forkhead box E1 (FOXE1), also known as thyroid transcription factor 2 (TTF-2), belongs to a large family of forkhead transcription factors. It plays important roles in embryogenesis, cell growth, and differentiation. Cancer-specific FOXE1 hypermethylation events have been identified in several cancers. However, the expression and function of FOXE1 in the tumorigenesis of colorectal cancer remain still unknown. In this study, we examined FOXE1 expression and methylation in normal colon mucosa, colorectal cancer (CRC) cell lines, and primary tumors by immunohistochemistry, semi-quantitative RT-PCR, methylation-specific PCR, and bisulfite genomic sequencing. We found that FOXE1 was frequently methylated and silenced in CRC cell lines and was downregulated in CRC tissues compared with paired adjacent non-tumor tissues. Meanwhile, low FOXE1 expression was significantly correlated with lymph node metastasis and advanced TNM stages, indicating its potential as a tumor marker. Subsequently, we established colon cancer cell lines with stable FOXE1 expression to observe the biological effect on colorectal cancer, including cell growth, migration, actin cytoskeleton, and growth of human colorectal xenografts in nude mice. Ectopic expression of FOXE1 could suppress tumor cell growth and migration and affect the organization of the actin cytoskeleton together with suppressing tumorigenicity in vivo. FOXE1 methylation was frequently seen in association with a complete absence of or downregulated gene expression, and FOXE1 plays a suppressive role in the development and progression of colorectal cancer.

Role of HDAC6-STAT3 in immunomodulatory pathways in Colorectal cancer cells

Colorectal cancer (CRC) is one of the most common malignant neoplasms and the second leading cause of death from tumors worldwide. Therefore, there is a great need to study new therapeutical strategies, such as effective immunotherapies against these malignancies. Unfortunately, many CRC patients do not respond to current standard immunotherapies, making it necessary to search for adjuvant treatments. Histone deacetylase 6 (HDAC6) is involved in several processes, including immune response and tumor progression. Specifically, it has been observed that HDAC6 is required to activate the Signal Transducer and Activator of Transcription 3 (STAT3), a transcription factor involved in immunogenicity, by activating different genes in these pathways, such as PD-L1. Over-expression of immunosuppressive pathways in cancer cells deregulates T-cell activation. Therefore, we focused on the pharmacological inhibition of HDAC6 in CRC cells because of its potential as an adjuvant to avoid immunotolerance in immunotherapy. We investigated whether HDAC6 inhibitors (HDAC6is), such as Nexturastat A (NextA), affected STAT3 activation in CRC cells. First, we found that NextA is less cytotoxic than the non-selective HDACis panobinostat. Then, NextA modified STAT3 and decreased the mRNA and protein expression levels of PD-L1. Importantly, transcriptomic analysis showed that NextA treatment affected the expression of critical genes involved in immunomodulatory pathways in CRC malignancies. These results suggest that treatments with NextA reduce the functionality of STAT3 in CRC cells, impacting the expression of immunomodulatory genes involved in the inflammatory and immune responses. Therefore, targeting HDAC6 may represent an interesting adjuvant strategy in combination with immunotherapy.

Predictive biomarkers for colorectal cancer: a state-of-the-art systematic review

INTRODUCTION

Colorectal cancer (CRC) poses a substantial health burden, with early detection paramount for improved prognosis. This study aims to evaluate potential CRC biomarkers and detection techniques.

MATERIALS AND METHODS

This systematic review, reported in adherence to PRISMA Statement 2020 guidelines, collates the latest research on potential biomarkers and detection/prognosis methods for CRC, spanning the last decade.

RESULTS

Out of the 38 included studies, diverse biomarkers and detection methods emerged, with DNA methylation markers like SFRP2 and SDC2, microRNAs including miR-1290, miR-506, and miR-4316, and serum and plasma markers such as NTS levels and U2 snRNA fragments standing out. Methylated cfDNA and m5C methylation alteration in immune cells of the blood, along with circular RNA, showed promise as diagnostic markers. Meanwhile, techniques involving extracellular vesicles and lateral flow immunoassays exhibited potential for swift and effective CRC screening.

DISCUSSION

Our state-of-the-art review identifies potential biomarkers, including SFRP2, SDC2, miR-1290, miR-506, miR-4316, and U2 snRNA fragments, with significant potential in enhancing CRC detection. However, comprehensive validation studies and a rigorous evaluation of clinical utility and cost-effectiveness remain necessary before integration into routine clinical practice.

CONCLUSION

The findings emphasize the need for continued research into biomarkers and detection methods to improve patient outcomes.

Therapeutic efficacy of α-lactalbumin coated oleic acid based liposomes against colorectal carcinoma in Caco-2 cells and DMH-treated albino rats

Colorectal cancer (CRC) is a malignant tumor recognized as a major cause of morbidity and mortality throughout the world. Therefore, novel liposomes of oleic acid coated with camel α-lactalbumin (α-LA coated liposomes) were developed for their potential antitumor activity against CRC, both in vitro and in DMH-induced CRC-modeled animal. In vitro results indicated the high safety of α-LA coated liposomes towards normal human cells with potent antitumor activity against Caco-2 cells at an IC50 value of 57.01 ± 3.55 µM with selectivity index of 6.92 ± 0.48. This antitumor activity has been attributed to induction of the apoptotic mechanism, as demonstrated by nuclear condensation and arrest of Caco-2 cells in sub-G1 populations. α-LA coated liposomes also revealed a significant up-regulation of the p53 gene combined with a down-regulation of the Bcl2 gene. Moreover, in vivo results revealed that treatment of induced-CRC modeled animals with α-LA coated liposomes for six weeks markedly improved the CRC-disorders; this was achieved from the significant reduction in the values of AFP, CEA, CA19.9, TNF-α, IL-1β, MDA, and NO coupled with remarkable rise in SOD, GPx, GSH, CAT, and CD4+ levels. The histopathological findings asserted the therapeutic potential of α-LA coated liposomes in the treatment of CRC. Therefore, the present results proved the antitumor activity of α-LA coated liposomes against CRC through the restoration of impaired oxidative stress, improved immune response, and reduced inflammation.Communicated by Ramaswamy H. Sarma.

Identification of hub genes related to CD4+ memory T cell infiltration with gene co-expression network predicts prognosis and immunotherapy effect in colon adenocarcinoma

Background: CD4+ memory T cells (CD4+ MTCs), as an important part of the microenvironment affecting tumorigenesis and progression, have rarely been systematically analyzed. Our purpose was to comprehensively analyze the effect of CD4+ MTC infiltration on the prognosis of colon adenocarcinoma (COAD). Methods: Based on RNA-Seq data, weighted gene co-expression network analysis (WGCNA) was used to screen the CD4+ MTC infiltration genes most associated with colon cancer and then identify hub genes and construct a prognostic model using the least absolute shrinkage and selection operator algorithm (LASSO). Finally, survival analysis, immune efficacy analysis, and drug sensitivity analysis were performed to evaluate the role of the prognostic model in COAD. Results: We identified 929 differentially expressed genes (DEGs) associated with CD4+ MTCs and constructed a prognosis model based on five hub genes (F2RL2, TGFB2, DTNA, S1PR5, and MPP2) to predict overall survival (OS) in COAD. Kaplan-Meier analysis showed poor prognosis in the high-risk group, and the analysis of the hub gene showed that overexpression of TGFB2, DTNA, S1PR5, or MPP2 was associated with poor prognosis. Clinical prediction nomograms combining CD4+ MTC-related DEGs and clinical features were constructed to accurately predict OS and had high clinical application value. Immune efficacy and drug sensitivity analysis provide new insights for individualized treatment. Conclusion: We constructed a prognostic risk model to predict OS in COAD and analyzed the effects of risk score on immunotherapy efficacy or drug sensitivity. These studies have important clinical significance for individualized targeted therapy and prognosis.

Screening for Colorectal Cancer Leading into a New Decade: The "Roaring '20s" for Epigenetic Biomarkers?

Colorectal cancer (CRC) has an important bearing (top five) on cancer incidence and mortality in the world. The etiology of sporadic CRC is related to the accumulation of genetic and epigenetic alterations that result in the appearance of cancer hallmarks such as abnormal proliferation, evasion of immune destruction, resistance to apoptosis, replicative immortality, and others, contributing to cancer promotion, invasion, and metastasis. It is estimated that, each year, at least four million people are diagnosed with CRC in the world. Depending on CRC staging at diagnosis, many of these patients die, as CRC is in the top four causes of cancer death in the world. New and improved screening tests for CRC are needed to detect the disease at an early stage and adopt patient management strategies to decrease the death toll. The three pillars of CRC screening are endoscopy, radiological imaging, and molecular assays. Endoscopic procedures comprise traditional colonoscopy, and more recently, capsule-based endoscopy. The main imaging modality remains Computed Tomography (CT) of the colon. Molecular approaches continue to grow in the diversity of biomarkers and the sophistication of the technologies deployed to detect them. What started with simple fecal occult blood tests has expanded to an armamentarium, including mutation detection and identification of aberrant epigenetic signatures known to be oncogenic. Biomarker-based screening methods have critical advantages and are likely to eclipse the classical modalities of imaging and endoscopy in the future. For example, imaging methods are costly and require highly specialized medical personnel. In the case of endoscopy, their invasiveness limits compliance from large swaths of the population, especially those with average CRC risk. Beyond mere discomfort and fear, there are legitimate iatrogenic concerns associated with endoscopy. The risks of perforation and infection make endoscopy best suited for a confirmatory role in cases where there are positive results from other diagnostic tests. Biomarker-based screening methods are largely non-invasive and are growing in scope. Epigenetic biomarkers, in particular, can be detected in feces and blood, are less invasive to the average-risk patient, detect early-stage CRC, and have a demonstrably superior patient follow-up. Given the heterogeneity of CRC as it evolves, optimal screening may require a battery of blood and stool tests, where each can leverage different pathways perturbed during carcinogenesis. What follows is a comprehensive, systematic review of the literature pertaining to the screening and diagnostic protocols used in CRC. Relevant articles were retrieved from the PubMed database using keywords including: "Screening", "Diagnosis", and "Biomarkers for CRC". American and European clinical trials in progress were included as well.

CHD4 as an important mediator in regulating the malignant behaviors of colorectal cancer

Colorectal cancer (CRC) has ranked first in terms of incidence in Taiwan. Surgical resection combined with chemo-, radio-, or targeted-therapies are the main treatments for CRC patients in current clinical practice. However, many CRC patients still respond poorly to these treatments, leading to tumor recurrence and an unacceptably high incidence of metastasis and death. Therefore, appropriate diagnosis, treatment, and drug selection are pressing issues in clinical practice. The Mi-2/nucleosome remodeling and deacetylase complex is an important epigenetic regulator of chromatin structure and gene expression. An important component of this complex is chromodomain-helicase-DNA-binding protein 4 (CHD4), which is involved in DNA repair after injury. Recent studies have indicated that CHD4 has oncogenic functions that inhibit multiple tumor suppressor genes through epigenetic regulation. However, the role of CHD4 in CRC has not yet been well investigated. In this study, we compared CHD4 expression in CRC patients from The Cancer Genome Atlas database. We found higher levels of CHD4 expression in CRC patients. In a series of in vitro experiments, we found that CHD4 affected cell motility and drug sensitivity in CRC cells. In animal models, the depletion of CHD4 affected CRC tumor growth, and the combination of a histone deacetylase 1 (HDAC1) inhibitor and platinum drugs inhibited CHD4 expression and increased the cytotoxicity of platinum drugs. Moreover, CHD4 expression was also a prognostic biomarker in CRC patients. Based on the above results, we believe that CHD4 expression is a viable biomarker for predicting metastasis CRC patients, and it has the potential to become a target for drug development.

Automatic Detection of the Circulating Cell-Free Methylated DNA Pattern of GCM2, ITPRIPL1 and CCDC181 for Detection of Early Breast Cancer and Surgical Treatment Response

The early detection of cancer can reduce cancer-related mortality. There is no clinically useful noninvasive biomarker for early detection of breast cancer. The aim of this study was to develop accurate and precise early detection biomarkers and a dynamic monitoring system following treatment. We analyzed a genome-wide methylation array in Taiwanese and The Cancer Genome Atlas (TCGA) breast cancer (BC) patients. Most breast cancer-specific circulating methylated CCDC181, GCM2 and ITPRIPL1 biomarkers were found in the plasma. An automatic analysis process of methylated ccfDNA was established. A combined analysis of CCDC181, GCM2 and ITPRIPL1 (CGIm) was performed in R using Recursive Partitioning and Regression Trees to establish a new prediction model. Combined analysis of CCDC181, GCM2 and ITPRIPL1 (CGIm) was found to have a sensitivity level of 97% and an area under the curve (AUC) of 0.955 in the training set, and a sensitivity level of 100% and an AUC of 0.961 in the test set. The circulating methylated CCDC181, GCM2 and ITPRIPL1 was also significantly decreased after surgery (all p < 0.001). The aberrant methylation patterns of the CCDC181, GCM2 and ITPRIPL1 genes means that they are potential biomarkers for the detection of early BC and can be combined with breast imaging data to achieve higher accuracy, sensitivity and specificity, facilitating breast cancer detection. They may also be applied to monitor the surgical treatment response.

Relationship between nutritional status and immediate complications in patients undergoing colorectal surgery

Introduction several complications may occur during colorectal surgical procedures and factors, such as nutritional status, substantially contribute to this problem.

Objective evaluate the relationship between nutritional status (determined by different tools) and the emergence of early postoperative complications, as well as analyze social parameters, lifestyle, food intake, and time to diet reintroduction.

Methods case series study conducted in the surgical proctologic ward of the Hospital Barão de Lucena, Recife, Pernambuco, with individuals of both sexes diagnosed with colorectal cancer who underwent a surgical procedure involving at least one anastomosis. Social, demographic and clinical data, life style, dietary intake, nutritional status, and the immediate postsurgical complications were evaluated.

Results among the 31 patients studied, there was a higher prevalence of females (74.2%), mean age of 61.9 ± 12.4 years old, and the rectum was the primary site of cancer in 54.8%. Most patients came from the countryside, were retirees, had lower education, consumed too much red meat, processed meats, and fats, with low consumption of fruits and vegetables, and were sedentary. Regarding nutritional status, nutritional risk was found in 58.1%, mean BMI of 25.7 ± 6.8 kg/m2, and 54.8% had significant weight loss. Additionally, 38.7% had some of the immediate complications, particularly paralytic ileus and abdominal distension. There was a delay in the onset of renourishment, and there was no association between nutritional status and immediate complications.

Conclusion colorectal cancer is closely related to eating habits and lifestyle. Patients with this malignancy have a marked weight loss; however, in this study, we found no association between nutritional status and the incidence of postoperative complications.

Association of visual and quantitative heterogeneity of 18F-FDG PET images with treatment response in locally advanced rectal cancer: A feasibility study

BACKGROUND AND PURPOSE

Few tools are available to predict tumor response to treatment. This retrospective study assesses visual and automatic heterogeneity from 18F-FDG PET images as predictors of response in locally advanced rectal cancer.

METHODS

This study included 37 LARC patients who underwent an 18F-FDG PET before their neoadjuvant therapy. One expert segmented the tumor from the PET images. Blinded to the patient´s outcome, two experts established by consensus a visual score for tumor heterogeneity. Metabolic and texture parameters were extracted from the tumor area. Multivariate binary logistic regression with cross-validation was used to estimate the clinical relevance of these features. Area under the ROC Curve (AUC) of each model was evaluated. Histopathological tumor regression grade was the ground-truth.

RESULTS

Standard metabolic parameters could discriminate 50.1% of responders (AUC = 0.685). Visual heterogeneity classification showed correct assessment of the response in 75.4% of the sample (AUC = 0.759). Automatic quantitative evaluation of heterogeneity achieved a similar predictive capacity (73.1%, AUC = 0.815).

CONCLUSION

A response prediction model in LARC based on tumor heterogeneity (assessed either visually or with automatic texture measurement) shows that texture features may complement the information provided by the metabolic parameters and increase prediction accuracy.

Epigenetics/Epigenomics and Prevention of Early Stages of Cancer by Isothiocyanates

Cancer is a complex disease and cancer development takes 10-50 years involving epigenetics. Evidence suggests that approximately 80% of human cancers are linked to environmental factors impinging upon genetics/epigenetics. Because advanced metastasized cancers are resistant to radiotherapy/chemotherapeutic drugs, cancer prevention by relatively nontoxic chemopreventive "epigenetic modifiers" involving epigenetics/epigenomics is logical. Isothiocyanates are relatively nontoxic at low nutritional and even higher pharmacologic doses, with good oral bioavailability, potent antioxidative stress/antiinflammatory activities, possess epigenetic-modifying properties, great anticancer efficacy in many in vitro cell culture and in vivo animal models. This review summarizes the latest advances on the role of epigenetics/epigenomics by isothiocyanates in prevention of skin, colon, lung, breast, and prostate cancers. The exact molecular mechanism how isothiocyanates modify the epigenetic/epigenomic machinery is unclear. We postulate "redox" processes would play important roles. In addition, isothiocyanates sulforaphane and phenethyl isothiocyanate, possess multifaceted molecular mechanisms would be considered as "general" cancer preventive agents not unlike chemotherapeutic agents like platinum-based or taxane-based drugs. Analogous to chemotherapeutic agents, the isothiocyanates would need to be used in combination with other nontoxic chemopreventive phytochemicals or drugs such as NSAIDs, 5-α-reductase/aromatase inhibitors targeting different signaling pathways would be logical for the prevention of progression of tumors to late advanced metastatic states.

Natural and synthetic retinoids in preclinical colorectal cancer models

Colorectal cancer (CRC) remains a leading cause of cancer-related morbidity and mortality worldwide. Although targeted therapy in combination with chemotherapy in CRC prolongs the overall survival of patients with metastatic disease, acquired resistance and relapse hinder their clinical benefits. Moreover, patients with some specific genetic profile are unlikely to benefit from targeted therapy, suggesting the need for safe and effective treatment strategies. Retinoids, comprising of natural and synthetic analogs, are a class of chemical compounds that regulate cellular proliferation, differentiation, and cell death. Retinoids have been used in the clinic for several leukemias and solid tumors, either as single agents or in combination therapy. Furthermore, retinoids have shown potent chemotherapeutic and chemopreventive properties in different cancer models, including CRC. In this review, we summarize the major preclinical findings in CRC in which natural and synthetic retinoids showed promising antitumor activities and stress on the proposed mechanisms of action. Understanding of the retinoids' antitumor mechanisms would provide insights to support and warrant their development in the management of CRC.

Hypermethylation and decreased expression of TMEM240 are potential early-onset biomarkers for colorectal cancer detection, poor prognosis, and early recurrence prediction

BACKGROUND

Gene silencing by aberrant DNA methylation of promoter regions remains the most dominant phenomenon occurring during tumorigenesis. Improving the early diagnosis, prognosis, and recurrence prediction of colorectal cancer using noninvasive aberrant DNA methylation biomarkers has encouraging potential. The aim of this study is to characterize the DNA methylation of the promoter region of TMEM240, as well as gene expression and its effect on cell biological functions and its applications in early detection and outcome prediction.

RESULTS

Highly methylated CpG sites were identified in the TMEM240 gene by Illumina methylation 450K arrays in 26 Taiwanese patient paired samples and 38 paired samples from The Cancer Genome Atlas (TCGA) colorectal cancer dataset. Transient transfection and knockdown of TMEM240 were performed to demonstrate the role of TMEM240 in colorectal cancer cells. The data showed that TMEM240 could lead to G1 cell cycle arrest, repress cancer cell proliferation, and inhibit cancer cell migration. The quantitative methylation-specific real-time polymerase chain reaction (PCR) results revealed that 87.8% (480 of 547) of the colorectal cancer tumors had hypermethylated TMEM240, and this was also found in benign tubular adenomas (55.6%). Circulating cell-free methylated TMEM240 was detected in 13 of 25 (52.0%) Taiwanese colorectal cancer patients but in fewer (28.6%) healthy controls. In 72.0% (85/118) of tissue samples, TMEM240 mRNA expression was lower in Taiwanese CRC tumor tissues than in normal colorectal tissues according to real-time reverse transcription PCR results, and this was also found in benign tubular adenomas (44.4%). The TMEM240 protein was analyzed in South Korean and Chinese CRC patient samples using immunohistochemistry. The results exhibited low protein expression in 91.7% (100/109) of tumors and 75.0% (24/32) of metastatic tumors but exhibited high expression in 75.0% (6/8) of normal colon tissues. Multivariate Cox proportional hazards regression analysis found that mRNA expression of TMEM240 was significantly associated with overall, cancer-specific, and recurrence-free survival (p = 0.012, 0.007, and 0.022, respectively).

CONCLUSIONS

Alterations in TMEM240 are commonly found in Western and Asian populations and can potentially be used for early prediction and as poor prognosis and early-recurrence biomarkers in colorectal cancer.

Epigenetics/epigenomics and prevention by curcumin of early stages of inflammatory-driven colon cancer

Colorectal cancer (CRC) is associated with significant morbidity and mortality in the US and worldwide. CRC is the second most common cancer-related death in both men and women globally. Chronic inflammation has been identified as one of the major risk factors of CRC. It may drive genetic and epigenetic/epigenomic alterations, such as DNA methylation, histone modification, and non-coding RNA regulation. Current prevention modalities for CRC are limited and some treatment regimens such as use the nonsteroidal anti-inflammatory drug aspirin may have severe side effects, namely gastrointestinal ulceration and bleeding. Therefore, there is an urgent need of developing alternative strategies. Recently, increasing evidence suggests that several dietary cancer chemopreventive phytochemicals possess anti-inflammation and antioxidative stress activities, and may prevent cancers including CRC. Curcumin (CUR) is the yellow pigment that is found in the rhizomes of turmeric (Curcuma longa). Many studies have demonstrated that CUR exhibit strong anticancer, antioxidative stress, and anti-inflammatory activities by regulating signaling pathways, such as nuclear factor erythroid-2-related factor 2, nuclear factor-κB, and epigenetics/epigenomics pathways of histones modifications, and DNA methylation. In this review, we will discuss the latest evidence in epigenetics/epigenomics alterations by CUR in CRC and their potential contribution in the prevention of CRC.

Down expression of lnc-BMP1-1 decreases that of Caveolin-1 is associated with the lung cancer susceptibility and cigarette smoking history

Lnc-BMP1-1 is a lncRNA transcribed from SFTPC (surfactant associated protein C), a lung tissue specific gene encoding pulmonary-associated surfactant protein C (SPC) that is solely secreted by alveolar typeⅡ epithelial cells, among which the ones with SFTPC+ might be transformed into lung adenocarcinoma cells. Caveolin-1 (Cav-1) is a candidate tumor suppressor gene and is vital for coping with oxidative stress induced by cigarette smoke. When comparing lung cancer tissues with their adjacent normal tissues, the expression of lnc-BMP1-1 were decreased, especially in patients with cigarette smoking history (P=0.027), and positively associated with the expression of Cav-1 (P<0.001). When comparing to A549 cells transfected with empty vector (A549-NC cells), the expression level of Cav-1 in A549 cells with over-expressed lnc-BMP1-1 (A549-BMP cells) was increased along with the decreased level of HDAC2 protein. The drug sensitivity of A549-BMP cells to Doxorubicin hydrochloride (DOX) was increased; the growth and migration capability of A549-BMP cells were inhibited along with the decreased protein level of Bcl-2 and DNMT3a; the growth of tumor in nude mice injected with A549-BMP cells were inhibited, too. Furthermore, the lnc-BMP1-1 and Cav-1 expression was also down-regulated in the human bronchial epithelial (16HBE) cells treated with cigarette smoke extract (CSE).

Silencing or inhibition of H3K79 methyltransferase DOT1L induces cell cycle arrest by epigenetically modulating c-Myc expression in colorectal cancer

BACKGROUND

Epigenetic regulations play pivotal roles in tumorigenesis and cancer development. Disruptor of telomeric silencing-1-like (DOT1L), also known as KMT4, is the only identified histone methyltransferase that catalyzes the mono-, di-, and tri-methylation of lysine 79 histone 3 (H3K79). However, little is known about the effect of H3K79 methylation on the modulation of colorectal cancer (CRC) development.

METHODS

DOT1L expression profiles in different subgroups of CRC tissues and its clinical significances were analyzed from some online datasheets. DOT1L in CRC cell lines was silenced by either lentivirus-mediated knockdown or inhibited by its specific inhibitor, EPZ004777. Then cell proliferation was detected by MTT assay, BrdU assay, and soft agar assay; cell cycle was detected by cytometry; and tumorigenicity was detected by using nude mice xenograft models. Clinical co-expression was analyzed between DOT1L and c-Myc. Chromatin immunoprecipitation (ChIP) assay was used to determine whether the translation of c-Myc was epigenetically regulated by H3K79me2 induced by DOT1L. c-Myc overexpression was used to rescue the cell cycle arrest and tumor growth induced by DOT1L silencing or inhibition in CRC.

RESULTS

We found that DOT1L was highly expressed in colorectal cancer and was negatively related to the prognosis of patients with CRC. Silencing or inhibition of DOT1L blocked cell proliferation, BrdU incorporation, self-renewal capability in vitro, and tumorigenicity in vivo. Besides, inhibition or silencing of DOT1L also induced cell cycle arrest at S phase, as well as decreased the expression of CDK2 and Cyclin A2. Furthermore, in the clinical databases of CRC, we found that the expression of DOT1L was positively correlated with that of c-Myc, a major regulator in the upstream of cell cycle-related factors. Besides, c-Myc expression was downregulated after DOT1L knockdown and c-Myc restoration rescued decrease of cell proliferation, BrdU corporation, self-renewal capability, cell cycle progression in vitro and tumorigenicity in vivo induced by DOT1L silencing. Then we found that H3K79 methylation was decreased after DOT1L knockdown. ChIP assay showed that H3K79me2 was enriched on the - 682~+ 284 region of c-Myc promoter, and the enrichment was decreased after DOT1L inhibition.

CONCLUSIONS

Our results show that DOT1L epigenetically promotes the transcription of c-Myc via H3K79me2. DOT1L silencing or inhibition induces cell cycle arrest at S phase. DOT1L is a potential marker for colorectal cancer and EPZ004777 may be a potential drug for the treatment of colorectal cancer.

Genome-wide methylation and expression profiling identify methylation-associated genes in colorectal cancer

Aim: To identify methylation-associated genes in the carcinogenesis of colorectal cancer (CRC). Materials & methods: Genome-wide patterns of DNA methylation and gene expression in CRC tissues and adjacent normal tissues were determined and further validated in The Cancer Genome Atlas data and Chinese CRC patients, respectively. Gene overexpression and knockdown cells were constructed to investigate their biological roles in CRC. Results: After validations, hypermethylation of eight genes were found to be correlated with their reduced transcription, and hypomethyaltion of three genes were associated with their upregulation. CADM3, CNRIP1, GRHL2, GRIA4, GSTM2 and NRXN1 were associated with the overall survival of CRC patients. CNRIP1 and GSTM2 were mainly responsible for the proliferation in CRC cells. Conclusion: A total of 11 genes may be promising biomarkers for CRC.

BCL6B suppresses proliferation and migration of colorectal carcinoma cells through inhibition of the PI3K/AKT signaling pathway

B‑cell CLL/lymphoma 6 member B (BCL6B), a BCL6‑homologous gene, has been reported to be a tumor suppressor that is silenced in a variety of human cancers, including colorectal cancer (CRC). Although it was recently demonstrated that reduced expression of BCL6B is associated with tumor stage and lymph node metastasis in CRC, little is known on whether BCL6B contributes to CRC development, or the related underlying mechanism. The aim of the present study was to detect BCL6B expression in CRC cells, and determine the molecular mechanisms underlying the role of BCL6B in CRC development by investigating cell proliferation and migration in vitro. As a result, BCL6B expression was found to be notably repressed in CRC cells compared with normal intestinal epithelial cells by reverse transcription‑polymerase chain reaction and western blot analysis. CRC cell proliferation was significantly inhibited by BCL6B upregulation, as indicated by MTT and colony‑forming assays. Cell apoptosis was markedly induced, as indicated by flow cytometry, and BCL6B‑transfected CRC cells exhibited decreased migration ability. Additionally, BCL6B overexpression diminished the phosphorylation level of AKT in CRC cells. These effects of BCL6B were empowered by treatment with the specific phosphoinositide 3 kinase (PI3K)/AKT inhibitor LY294002. Furthermore, overexpression of BCL6B resulted in upregulation of E‑cadherin and downregulation of cyclin D1 and matrix metalloproteinase‑9, which were strongly enhanced by LY294002. In conclusion, the findings of the present study demonstrated that BCL6B suppressed the proliferation and migration of CRC cells indirectly, via inhibition of PI3K.

Butyrate Inhibits Indices of Colorectal Carcinogenesis via Enhancing α-Ketoglutarate-Dependent DNA Demethylation of Mismatch Repair Genes

SCOPE

Butyrate, the fermentation end product of gut microbiota in the colon, is known for its antitumor effects, but the mechanisms remained to be defined. α-ketoglutarate (α-KG) mediates DNA demethylation and aberrant epigenetic modifications are associated with carcinogenesis. The objectives of this study are to evaluate the effects of butyrate on α-KG mediated epigenetic modification in colorectal adenocarcinoma HT-29 and Caco-2 cells.

METHODS AND RESULTS

Butyrate suppressed proliferation, potentiated differentiation, and induced apoptosis in both HT-29 and Caco-2 cells, associated with enhanced expression of isocitrate dehydrogenase 1 (IDH1) and pyruvate dehydrogenase. Furthermore, butyrate upregulated acetyl-CoA and α-KG, concomitant with enhanced histone acetylation and DNA demethylation in the promoter of DNA mismatch repair (MMR) gene. Knocking down IDH1 abolished the positive effects of butyrate on CRC apoptosis and MMR protein expression, in conjunction with reduced α-KG content. Importantly, α-KG supplementation recovered the beneficial effects of butyrate in IDH1-deficient cells.

CONCLUSION

In summary, butyrate inhibits indices of colorectal carcinogenesis in an α-KG-dependent manner.

Decoding colorectal cancer epigenomics

Colorectal cancer (CRC) is very heterogeneous and presents different types of epigenetic alterations including DNA methylation, histone modifications and microRNAs. These changes are considered as characteristics of various observed clinical phenotypes. Undoubtedly, the discovery of epigenetic pathways with novel epigenetic-related mechanisms constitutes a promising advance in cancer biomarker discovery. In this review, we provide an evidence-based discussing of the current understanding of CRC epigenomics and its role in initiation, epithelial-to-mesenchymal transition and metastasis. We also discuss the recent findings regarding the potential clinical perspectives of these alterations as potent biomarkers for CRC diagnosis, prognosis, and therapy in the era of liquid biopsy.

Hypermethylation of BEND5 contributes to cell proliferation and is a prognostic marker of colorectal cancer

Aberrant hypermethylation of CpG islands in tumor suppressor genes (TSGs) contributes to colorectal tumorigenesis. To identify new colorectal cancer (CRC) screening marker, we investigated DNA methylation alterations in novel TSGs. Using HumanMethylation450 BeadChip arrays, CpG regions in BEND5 were the most highly methylated among all genomic regions in 26 colorectal tumors compared to paired non-neoplastic tissues from a Taiwan cohort. Therefore, BEND5 was selected for further analysis. Quantitative methylation-specific real-time PCR revealed that 86.7% (117/135) of CRC patients exhibited hypermethylated BEND5. Real-time reverse transcription PCR identified that BEND5 mRNA expression was downregulated in 68% (32/47) of the analyzed samples. BEND5 hypermethylation was associated with poor overall survival (OS) in Taiwan patients with early-stage CRC (P = 0.037). In a CRC tissue set from South Korea, OS was higher in patients with high BEND5 protein expression than in those with low BEND5 protein expression (P = 0.037) by using immunohistochemistry assays. Consistently, BEND5 hypermethylation was associated with poor OS in patients with early-stage CRC in The Cancer Genome Atlas (TCGA) data set (P = 0.003). Multivariate Cox proportional hazards regression analysis further supported that hypermethylation of BEND5 genes was significantly associated with OS in Taiwan and TCGA CRC patients (P = 0.023 and 0.033, respectively). Finally, the cell model assay with transient transfection of BEND5 or si-BEND5 knockdown indicated that BEND5 inhibited cancer cell proliferation. In conclusion, epigenetic alteration in the candidate TSG BEND5 contributes to colorectal cancer development and is a prognostic marker of CRC.

Histone code and long non-coding RNAs (lncRNAs) aberrations in lung cancer: implications in the therapy response

Respiratory diseases hold several genome, epigenome, and transcriptional aberrations as a cause of the accumulated damage promoted by, among others, environmental risk factors. Such aberrations can also come about as an adaptive response when faced with therapeutic oncological drugs. In epigenetic terms, aberrations in DNA methylation patterns, histone code marks balance, and/or chromatin-remodeling complexes recruitment, among Polycomb Repressive Complex-2 (PRC2) versus Trithorax (TRX) Activator Complex, have been proposed to be affected by several previously characterized functional long non-coding RNAs (lncRNAs). Such molecules are involved in modulating and/or controlling lung cancer epigenome and genome expression, as well as in malignancy and clinical progression in lung cancer. Several recent reports have described diverse epigenetic modifications in lung cancer cells and solid tumors, among others genomic DNA methylation and post-translational modifications (PTMs) on histone tails, as well as lncRNAs patterns and levels of expression. However, few systematic approaches have attempted to demonstrate a biological function and clinical association, aiming to improve therapeutic decisions in basic research and lung clinical oncology. A widely used example is the lncRNA HOTAIR and its functional histone mark H3K27me3, which is directly associated to the PRC2; however, few systematic pieces of solid evidence have been experimentally performed, conducted and/or validated to predict lung oncological therapeutic efficacy. Recent evidence suggests that chromatin-remodeling complexes accompanied by lncRNAs profiles are involved in several comprehensive lung carcinoma clinical parameters, including histopathology progression, prognosis, and/or responsiveness to unique or combined oncological therapies. The present manuscript offers a systematic revision of the current knowledge about the major epigenetic aberrations represented by changes in histone PTMs and lncRNAs expression levels and patterns in human lung carcinomas in cancer drug-based treatments, as an important comprehensive knowledge focusing on better oncological therapies. In addition, a new future direction must be refocusing on several gene target therapies, mainly on pharmaceutical EGFR-TKIs compounds, widely applied in lung cancer, currently the leading cause of death by malignant diseases.

Profile of Expression of Genes Encoding Matrix Metallopeptidase 9 (MMP9), Matrix Metallopeptidase 28 (MMP28) and TIMP Metallopeptidase Inhibitor 1 (TIMP1) in Colorectal Cancer: Assessment of the Role in Diagnosis and Prognostication

Background

Studies on the pathomechanism of colorectal cancer (CRC) expansion indicate a significant role of metalloproteinases and their inhibitors in the extracellular matrix. The results of the analysis of a profile of transcriptional activity of genes encoding metalloproteinases were the basis of the hypothesis indicating changes in the expression of genes encoding MMP9, MMP28, and TIMP1 as an additional diagnostic and prognostic marker of CRC.

Material/Methods

The material consisted of samples obtained from resected tumors and healthy tissue samples from 15 CRC patients (aged 46–72 years) at clinical stages (CSs) I and II–IV.

Gene expression analysis was done using microarrays. Microarray data analysis was done using the GeneSpring 11.5 platform. The results were validated using the qRT-PCR technique.

Results

We found high levels of expression of MMP9 at each CS, as well as in the tissues at the early stage of CRC. Additionally, we observed high levels of expression of TIMP1 and low levels of MMP28 genes in CS II–IV. No statistically significant differences based on the stage of CRC were observed.

Conclusions

MMP9 gene profile may be a complementary diagnostic marker in CRC. The results suggest a crucial role of MMP9 at the early stage of carcinogenesis in the large intestine. The increase in MMP9 and TIMP1 mRNA concentration and the decrease in MMP28 in the large intestinal tissue may be a confirmation of cancer, but it may not indicate the advance of CRC.

Epigenetic biomarkers in colorectal cancer: premises and prospects

CONTEXT

Colorectal cancer is one of the most common cancers worldwide. Epigenetic alterations play an important role in the pathogenesis of the colorectal cancer.

OBJECTIVE

This review has focused on the most recent investigations, which has suggested potential epigenetic biomarkers in colorectal cancer.

METHODS

Evidences were achieved by searching online medical databases including Google scholar, Pubmed, Scopus and Science Direct.

RESULTS

Extensive studies have indicated that aberrant epigenetic modifications could serve as potential biomarkers for diagnosis, prognosis and prediction of colorectal cancer.

CONCLUSION

Advances in aberrant epigenetic modifications can open new avenues for exploration of reliable and robust biomarkers to improve the management of CRC patients.

Expression of DNA methyltransferases and target microRNAs in human tissue samples related to sporadic colorectal cancer

Tissue microenvironment functions as a pivotal mediator in colorectal carcinogenesis, and its alteration can cause some important cellular responses including epigenetic events. The present study examined histologically altered tissue structure, DNA methyltransferases (DNMTs) and their corresponding expression of target microRNAs (miRNA). Tissues resected by surgery were from primary colorectal carcinoma. These samples were from three locations: and were ≥10, 5 and ≤2 cm away from the proximal lesion of colon cancer, and marked as no. 1, no. 2 and no. 3, respectively. Histological alteration was assessed by H&E staining, expression of DNMT1, DNMT3A, and DNMT3B was detected by immunohistochemistry and western blotting, microarray chip was used to screen distinguishable miRNAs and miRNAs targeting DNMTs whose validation assay was performed by quantitative real-time polymerase chain reaction (qRT-PCR). Our results revealed that normal crypt structure was shown in no. 1, while many aberrant crypt foci appeared in no. 3. Significant upregulation of DNMT1, DNMT3A, and DNMT3B expression was found in para-carcinoma tissues, compared with the histopathologically unchanged tissues (P<0.05), furthermore, distinguishable expression profiling was observed of target miRNAs in tissues with different distance. Our results provide additional insights for future research of colorectal carcinogenesis by introducing the tissue microenvironment.

Melatonin inhibits tumorigenicity of glioblastoma stem-like cells via the AKT-EZH2-STAT3 signaling axis

Glioblastoma stem-like cells (GSCs) displaying self-renewing and tumor-propagating capacity play a particularly important role in maintaining tumor growth, therapeutic resistance, and tumor recurrence. Therefore, new therapeutic strategies focusing on impairing GSC maintenance are urgently needed. Here, we used GSCs isolated from surgical specimens from patients with glioblastoma multiforme (GBM) to study the roles and underlying mechanisms associated with melatonin in GSC biology. The results showed that melatonin directly targeted glioma tumor cells by altering GSC biology and inhibiting GSC proliferation. Additionally, melatonin altered profile of transcription factors to inhibit tumor initiation and propagation. Furthermore, EZH2 S21 phosphorylation and EZH2-STAT3 interaction in GSCs were impaired following melatonin treatment. These results suggested that melatonin attenuated multiple key signals involved in GSC self-renewal and survival, and further supported melatonin as a promising GBM therapeutic.

Never in mitosis gene A-related kinase 6 and aurora kinase A: New gene biomarkers in the conversion from ulcerative colitis to colorectal cancer

Ulcerative colitis (UC) is an important risk factor for colorectal cancer (CRC). Histone modifications are one of the epigenetic mechanisms that may have key roles in the carcinogenesis of CRC. At present, there are no studies comparing histone modification patterns of UC and CRC in the literature. Therefore the aim of the present study was to investigate whether genes, particularly those involved in histone modification, have value in patient monitoring with regards to CRC development in UC. Key gene expressions of the histone modification enzyme were assessed and compared in CRC, UC and control groups using the RT-PCR array technique. Patients were divided into subgroups based on the extent and duration of the disease and inflammatory burden, which are considered risk factors for CRC development in UC patients. In UC and CRC groups, a significantly higher overexpression of the NEK6 and AURKA genes compared to the control group was identified. In addition, there was a significantly higher overexpression of HDAC1 and PAK1 genes in the UC group, and of HDAC1, HDAC7, PAK1 and AURKB genes in the CRC group. NEK6, AURKA, HDAC1 and PAK1 were significantly overexpressed in patients with a longer UC duration. Overexpression of AURKA and NEK6 genes was significantly more pronounced in UC patients with more extensive colon involvement. HDAC1, HDAC7, PAK1, NEK6, AURKA and AURKB are important diagnostic and prognostic markers involved in the carcinogenesis of CRC. HDAC1, PAK1, NEK6 and AURKA may be considered as diagnostic markers to be used in CRC screening for UC patients.

Epigenetic therapy for colorectal cancer

Aberrations in epigenome that include alterations in DNA methylation, histone acetylation, and miRNA (microRNA) expression may govern the progression of colorectal cancer (CRC). These epigenetic changes affect every phase of tumor development from initiation to metastasis. Since epigenetic alterations can be reversed by DNA demethylating and histone acetylating agents, current status of the implication of epigenetic therapy in CRC is discussed in this article. Interestingly, DNA methyltransferase inhibitors (DNMTi) and histone deacetylase inhibitors (HDACi) have shown promising results in controlling cancer progression. The information provided here might be useful in developing personalized medicine approaches.

Constructing lncRNA functional similarity network based on lncRNA-disease associations and disease semantic similarity

Increasing evidence has indicated that plenty of lncRNAs play important roles in many critical biological processes. Developing powerful computational models to construct lncRNA functional similarity network based on heterogeneous biological datasets is one of the most important and popular topics in the fields of both lncRNAs and complex diseases. Functional similarity network consturction could benefit the model development for both lncRNA function inference and lncRNA-disease association identification. However, little effort has been attempted to analysis and calculate lncRNA functional similarity on a large scale. In this study, based on the assumption that functionally similar lncRNAs tend to be associated with similar diseases, we developed two novel lncRNA functional similarity calculation models (LNCSIM). LNCSIM was evaluated by introducing similarity scores into the model of Laplacian Regularized Least Squares for LncRNA–Disease Association (LRLSLDA) for lncRNA-disease association prediction. As a result, new predictive models improved the performance of LRLSLDA in the leave-one-out cross validation of various known lncRNA-disease associations datasets. Furthermore, some of the predictive results for colorectal cancer and lung cancer were verified by independent biological experimental studies. It is anticipated that LNCSIM could be a useful and important biological tool for human disease diagnosis, treatment, and prevention.

Folate and nutrients involved in the 1-carbon cycle in the pretreatment of patients for colorectal cancer

To assess the ingestion of folate and nutrients involved in the 1-carbon cycle in non-treated patients with colorectal adenocarcinoma in a reference center for oncology in southeastern Brazil. In total, 195 new cases with colorectal adenocarcinoma completed a clinical evaluation questionnaire and a Food Frequency Questionnaire (FFQ). Blood samples from 161 patients were drawn for the assessment of serum folate. A moderate correlation was found between serum concentrations of folate, folate intake and the dietary folate equivalent (DFE) of synthetic supplements. Mulatto or black male patients with a primary educational level had a higher intake of dietary folate. Of patients obtaining folate from the diet alone or from dietary supplements, 11.00% and 0.10%, respectively, had intake below the recommended level. Of the patients using dietary supplements, 35% to 50% showed high levels of folic acid intake. There was a prevalence of inadequacy for vitamins B2, B6 and B12, ranging from 12.10% to 20.18%, while 13.76% to 22.55% of patients were likely to have adequate choline intake. The considerable percentage of patients with folate intake above the recommended levels deserves attention because of the harmful effects that this nutrient may have in the presence of established neoplastic lesions.

Diterpenoid C of Radix Curcumae: an inhibitor of proliferation and inducer of apoptosis in human colon adenocarcinoma cells acting via inhibiting MAPK signaling pathway

CONTEXT

Radix Curcumae is a traditional Chinese medicine that possesses antitumor properties, from which a new compound, diterpenoid C, was previously isolated and characterized.

OBJECTIVE

In this study, using human colon adenocarcinoma SW620 cells, we further investigated the antitumor effects of diterpenoid C and the underlying mechanisms.

MATERIALS AND METHODS

Cell proliferation was assessed with the MTT assay. Cell apoptosis and cell-cycle progression were analyzed with flow cytometry. The expression of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (p38 MAPK), and their phosphorylated forms, as well as caspase-3 protein levels were examined with Western blots.

RESULTS

Diterpenoid C could inhibit the proliferation of SW620 cells in a dose- and time-dependent manner. The median inhibitory concentration (IC50) at 24, 48, and 72 h were 28.31, 15.58, and 6.14 μg/ml, respectively. The inhibition of proliferation was found to be statistically significant as compared with the well-established drugs 5-fluorouracil (5-Fu) and oxaliplatin (L-OHP) (p < 0.01). Diterpenoid C also induced apoptosis and arrested cell cycle. It showed the highest apoptosis rate (98.20 ± 0.91%) at 70 μg/ml, at 72 h. Meanwhile, diterpenoid C suppressed the phosphorylation of ERK, JNK, and p38 MAPK proteins, and markedly induced the cleavage of caspase 3.

DISCUSSION AND CONCLUSION

Diterpenoid C inhibits proliferation and induces apoptosis of cancer cells by suppressing the MAPK signaling pathway and inducing apoptotic factor caspase-3. Our results suggest that this novel compound might become a potent chemotherapeutic agent for the treatment of colon cancer and further studies are warranted.

Loss of EphB6 protein expression in human colorectal cancer correlates with poor prognosis

Erythropoietin-producing hepatocyte (Eph) receptor family constitutes the largest family of tyrosine kinase receptors in the human genome. Loss of EphB6, a kinase-deficient receptor, correlated with a negative outcome in several carcinomas. This study aimed to investigate the expression of EphB6 protein and mRNA levels in colorectal cancers (CRCs) and possible correlations with clinicopathological variables and prognosis. To assess protein expression level, 124 CRCs and 57 colorectal adenomas samples were examined by immunostaining, the mRNA level of 43 paired CRC and the adjacent normal tissues were detected by using SYBR Green real-time PCR method. Decreased expression of EphB6 protein was found in CRC as compared with adenoma and normal tissues (χ(2) = 10.146, P = 0.001 and χ(2) = 45.333, P < 0.001, respectively). Low EphB6 mRNA expression was detected in 83.8% of cancers with negative or low EphB6 protein expression. The loss of EphB6 protein in CRC was positively associated with poorly differentiation (P < 0.001), lymph node metastasis (P = 0.006), Dukes stage (P = 0.002) and depth of invasion (P = 0.016). The patients with lymph node metastasis had a worse prognosis independently of gender, age, tumor site, stage and differentiation (RR = 0.404, CI 0.267-0.213, P < 0.001). Low levels of EphB6 protein expression are associated with a shorter mean duration of survival in colorectal cancer. Our results demonstrated that EphB6 may represent a novel, useful tissue biomarker for the prediction of survival rate in CRC.

Histone H3 lysine 27 acetylation is altered in colon cancer

Background

Histone post-translational modifications (PTMs) play an important role in the regulation of the expression of genes, including those involved in cancer development and progression. However, our knowledge of PTM patterns in human tumours is limited.

Methods

MS-based analyses were used to quantify global alterations of histone PTMs in colorectal cancer (CRC) samples. Histones isolated from 12 CRCs and their corresponding normal mucosa by acidic extraction were separated by SDS-PAGE and analysed by liquid chromatography-mass spectrometry.

Results

Among 96 modified peptides, 41 distinct PTM sites were identified, of which 7, 13, 11, and 10 were located within the H2A, H2B, H3, and H4 sequences, respectively, and distributed among the amino-terminal tails and the globular domain of the four histones. Modification intensities were quantified for 33 sites, of which 4 showed significant (p-value ≤ 0.05) differences between CRC tissues and healthy mucosa samples. We identified histone H3 lysine 27 acetylation (H3K27Ac) as a modification upregulated in CRC, which had not been shown previously.

Conclusions

The present results indicate the usefulness of a bottom-up proteomic approach for the detection of histone modifications at a global scale. The differential abundance of H3K27Ac mark in CRC, a PTM associated with active enhancers, suggests its role in regulating genes whose expression changes in CRC.

Association between six genetic polymorphisms and colorectal cancer: a meta-analysis

OBJECTIVE

The aim of this study was to determine whether six genetic polymorphisms confer susceptibility to colorectal cancer (CRC).

METHODS

A systematic search for candidate genes of CRC was performed among several online databases, including PubMed, Embase, Web of Science, the Cochrane Library, CNKI, and Wanfang online libraries. After a comprehensive filtering procedure, we harvested five genes, including MGMT (rs12917 and rs2308321), ADH1B (rs1229984), SOD2 (rs4880), XPC (rs2228001), and PPARG (rs1801282). Using the REVMAN and Stata software, six meta-analyses were conducted for associations between CRC and the just-mentioned genetic variants.

RESULTS

A total of 34 comparative studies among 17,289 cases and 54,927 controls were involved in our meta-analyses. Significant association was found between ADH1B rs1229984 polymorphism and CRC (p=0.03, odds ratio [OR]=1.18, 95% confidence interval [CI]=1.01-1.36). We also found significant association between PPARG rs1801282 polymorphism and CRC (p=0.004, OR=1.498, 95% CI=1.139-1.970), and this significant association is specific in Caucasians (p=0.004, OR=1.603, 95% CI=1.165-2.205).

CONCLUSIONS

The current meta-analysis has established that ADH1B (rs1229984) and PPARG (rs1801282) are two risk variants of CRC.

DNA methylation as an epigenetic biomarker in colorectal cancer

Sporadic colorectal cancer (CRC) is a consequence of the accumulation of genetic and epigenetic alterations that result in the transformation of normal colonic epithelial cells to adenocarcinomas. Studies have indicated that a common event in the tumorigenesis of CRC is the association of global hypomethylation with discrete hypermethylation at the promoter regions of specific genes that are involved in cell cycle regulation, DNA repair, apoptosis, angiogenesis, adhesion and invasion. The present study aimed to investigate the epigenetic changes (DNA methylation) in 24 candidate genes in CRC. A total of 10 candidate hypermethylated (HM) and unmethylated (UM) genes were identified that may be useful epigenetic markers for non-invasive CRC screening. The five genes that had the highest average UM percentages in the control group were MLH1 (71.7%), DKK2 (69.6%), CDKN2A (68.4%), APC (67.5%) and hsa-mir-342 (67.4%). RUNX3 (58.9%), PCDH10 (55.5%), SFRP5 (52.1%), IGF2 (50.4%) and Hnf1b (50.0%) were the five genes with the highest average HM percentages in the test group. In summary, the present preliminary study identified the methylation profiles of normal and cancerous colonic epithelial tissues, and provided the groundwork for future large-scale methylation studies.

Epigenetics and colorectal cancer pathogenesis

Colorectal cancer (CRC) develops through a multistage process that results from the progressive accumulation of genetic mutations, and frequently as a result of mutations in the Wnt signaling pathway. However, it has become evident over the past two decades that epigenetic alterations of the chromatin, particularly the chromatin components in the promoter regions of tumor suppressors and oncogenes, play key roles in CRC pathogenesis. Epigenetic regulation is organized at multiple levels, involving primarily DNA methylation and selective histone modifications in cancer cells. Assessment of the CRC epigenome has revealed that virtually all CRCs have aberrantly methylated genes and that the average CRC methylome has thousands of abnormally methylated genes. Although relatively less is known about the patterns of specific histone modifications in CRC, selective histone modifications and resultant chromatin conformation have been shown to act, in concert with DNA methylation, to regulate gene expression to mediate CRC pathogenesis. Moreover, it is now clear that not only DNA methylation but also histone modifications are reversible processes. The increased understanding of epigenetic regulation of gene expression in the context of CRC pathogenesis has led to development of epigenetic biomarkers for CRC diagnosis and epigenetic drugs for CRC therapy.

Updates from the Intestinal Front Line: Autophagic Weapons against Inflammation and Cancer

The intestine lies at the interface between the organism and its environment and responds to infection/inflammation in a multi-leveled manner, potentially leading to chronic inflammatory pathologies and cancer formation. Indeed, the immune response at the intestinal epithelium has been found to be involved in the origin and development of colorectal cancer, which is the third most commonly diagnosed neoplastic disease. Among the mechanisms induced upon inflammation, autophagy appears as a defensive strategy for the clearance of invading microbes and intracellular waste components. Autophagy has also been found to play an important role in colorectal cancer, where it seems to have a pro-survival or pro-death function depending on the stage of the neoplastic process. In this paper we discuss the dual role of autophagy in colorectal cancer and review evidence showing that modulation of autophagy affects the immune response and cancer biology. The study of key players involved in autophagy might contribute to the design of new approaches for colorectal cancer, consisting in combined therapies capable of modifying cancer-specific metabolism rather than simply evoking a generic apoptotic and/or autophagic response, thus enhancing the efficacy of currently used drugs and treatments.

MicroRNA profiling of carcinogen-induced rat colon tumors and the influence of dietary spinach

SCOPE

MicroRNA (miRNA) profiles are altered in chronic conditions such as cardiovascular disease, diabetes, neurological disorders, and cancer. A systems biology approach was used to examine, for the first time, miRNAs altered in rat colon tumors induced by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a heterocyclic amine carcinogen from cooked meat.

METHODS AND RESULTS

Among the most highly dysregulated miRNAs were those belonging to the let-7 family. Subsequent computational modeling and target validation identified c-Myc and miRNA-binding proteins Lin28A/Lin28B (Lin28) as key players, along with Sox2, Nanog, and Oct-3/4. These targets of altered miRNAs in colon cancers have been implicated in tumor recurrence and reduced patient survival, in addition to their role as pluripotency factors. In parallel with these findings, the tumor-suppressive effects of dietary spinach given postinitiation correlated with elevated levels of let-7 family members and partial normalization of c-myc, Sox2, Nanog, Oct-3/4, HmgA2, Dnmt3b, and P53 expression.

CONCLUSION

We conclude that the let-7/c-Myc/Lin28 axis is dysregulated in heterocyclic amine-induced colon carcinogenesis, and that the tumor suppressive effects of dietary spinach are associated with partial normalization of this pathway.