MicroRNA-Mediated Migration of Colon Cancer Cells

Colorectal cancer (CRC) is the second most common cancer in women and third most common cancer in men worldwide. The cause of the majority of death related to CRC is believed to be the migration of cancer cells to distant organs which is known as cancer metastasis. The mechanism behind cancer cell metastasis is not fully understood but accumulating studies suggest that it could be due to enhanced tumor cell motility due to overexpression of metastasis related proteins. It is believed that microRNAs (miRNAs) play a significant role in the tumorigenesis and metastasis of cancer by regulating oncogenes. The aim of this thesis is to investigate the mechanism of miRNA-mediated colon cancer cell invasion and migration as well as possible targets genes of miRNAs. We found that knockdown of miR-155-5p by antagomiR reduces the expression of HuR mRNA and migration of colon cancer cells. Our data also showed that miR-155-5p is involved in positive regulation of HuR protein under stress conditions. Notably, this positive regulation is regulated by direct binding of miR-155-5p at AU rich element region in 3ʹ-UTR of HuR mRNA. In addition, it was found that miR-340-5p is also involved in colon cancer cell invasion and migration by regulating RhoA and FHL2 mRNA expression. Bioinformatics analysis revealed that both RhoA and FHL2 mature mRNA have conserved binding sites from 2 to 8 base positions for miR-340-5p. The seed region of miR-340-5p directly binds with the target sites of RhoA and FHL2 mRNA and negatively regulate their expression under stress conditions. We found that the inhibition of RhoA and FHL2 expression by the use of mimic miR-340-5p reduced colon cancer cells invasion and migration. In addition, it was found that inhibition of FHL2 reduces cancer cells proliferation and increases E-cadherin expression in colon cancer cells, suggesting that targeting FHL2 and RhoA by miR-340-5p might be a useful approach to antagonize colon cancer cells metastasis. The results of our studies not only show diverse mechanisms of colon cancer cells migration, but also provided valuable information that miRNAs can be an important target to develop new and effective therapeutics against colon cancer cells metastasis. Taken together, our data uncovered several new mechanisms for better understanding the mechanism of colon cancer cells metastasis and suggest that targeting miRNAs function could be a useful strategy to prevent colon cancer metastasis

Disruptive chemicals, senescence and immortality

Cell death is a process of dying within biological cells that are ceasing to function. This process is essential in regulating organism development, tissue homeostasis, and to eliminate cells in the body that are irreparably damaged. In general, dysfunction in normal cellular death is tightly linked to cancer progression. Specifically, the up-regulation of prosurvival factors, including oncogenic factors and antiapoptotic signaling pathways, and the down-regulation of proapoptotic factors, including tumor suppressive factors, confers resistance to cell death in tumor cells, which supports the emergence of a fully immortalized cellular phenotype. This review considers the potential relevance of ubiquitous environmental chemical exposures that have been shown to disrupt key pathways and mechanisms associated with this sort of dysfunction. Specifically, bisphenol A, chlorothalonil, dibutyl phthalate, dichlorvos, lindane, linuron, methoxychlor and oxyfluorfen are discussed as prototypical chemical disruptors; as their effects relate to resistance to cell death, as constituents within environmental mixtures and as potential contributors to environmental carcinogenesis.The publisher and the author(s) have made this article open access. This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by Oxford University Press. The published article can be found at: http://carcin.oxfordjournals.org

Chronic inflammation, apoptosis and (pre-)malignant lesions in the gastro-intestinal tract

Inflammatory conditions are characterized by activation of the transcription factor nuclear factor kappa B (NF-kappaB), resulting in the expression of NF-kappaB-regulated, inflammation-related genes, such as inducible nitric oxide synthase (iNOS) and cyclo-oxygenase-2 (COX-2). Expression of these genes contributes to the survival of cells. Indeed, exposure to pro-inflammatory cytokines in the absence of NF-kappaB activation leads to apoptosis. 1,2 Chronic inflammatory conditions are accompanied by constitutive activation of NF-kappaB and hence, to the continuous expression of pro-survival genes, as has been observed in chronic gastritis. 3 Although beneficial for the survival of cells during exposure to inflammatory stress, the continuous activation of NF-kappaB may also pose a risk: cells with a pro-survival phenotype may give rise to continuously proliferating cells and may thus be tumorigenic. Progression to a malignant phenotype of these cells will most likely involve additional changes in the expression of non-NF-kappaBregulated genes e.g. a shift in the balance of pro- and anti-apoptotic genes towards a more antiapoptotic phenotype. Literature on inflammation-related genes and the apoptotic balance in pre-malignant and malignant conditions in the gastro-intestinal tract is still scarce and conflicting. In this review, we aim to give an overview of the existing literature and we will focus on inflammation- and apoptosis-related genes in the sequence of normal epithelium-inflamed epithelium-metaplasia-dysplasia-cancer in the gastrointestinal tract, in particular esophagus (Barrett's esophagus: BE), stomach (gastritis) and colon (inflammatory bowel disease: IBD)

DNA damage in paediatric obesity: a promoter and predictor of cancer in adulthood

Obesity in children is one of the most serious, global, public health challenges of the 21st century. The accumulation of adipose tissue is associated with a range of metabolic complications including diabetes, cardiovascular disease and dyslipidaemia. Epidemiological evidence links obesity in childhood with developing certain types of cancer later in life. It is postulated that excess adipose tissue and consequent inflammation derived oxidative stress may inflict an accumulation of deleterious DNA mutations and promote genome instability and drive carcinogenesis. Furthermore, a deficiency in micronutrients that are essential for DNA repair may exacerbate this pathological state. This research combined the assessment of anthropometric, inflammatory, micro-nutritional and DNA damage biomarkers via non-invasive techniques. In total, 112 children were recruited from schools and NHS obesity clinics. Anthropometric markers assessed were waist to hip ratio, body fat percentage via bioelectrical impedance, and body mass index standard deviation scores (BMI-SDS). These markers were used to classify participants as obese or nonobese and used for correlational analysis. Inflammation and micronutrient status were determined via C-reactive protein and vitamin D Enzyme Immune Assay (EIA) in saliva. DNA damage assessments include a microscopic assessment of nuclear anomalies via the buccal cytome assay, salivary telomere length via quantitative Polymerase Chain Reaction (qPCR) and urinary 8- hydroxyguanosine (8-OHdG) via EIA. The results from this study indicate obesity to be concurrent with increased inflammation and vitamin D deficiency in this cohort of participants. In addition, obesity was associated with increased oxidative DNA damage (8-OHdG) in urine and DNA damage events in the buccal mucosa. Salivary telomere length was positively correlated with obesity and the total frequency of nuclear anomalies found in buccal epithelial cells. Furthermore, there was a negative correlation between vitamin D and the frequency of nuclear anomalies in the oral cavity. Importantly, odds ratio analysis indicates a high BMI Z-score, waist circumference, body fat percentage, salivary CRP and low salivary vitamin D to be independent risk factors for increased nuclear anomalies in the buccal mucosa. This research is the first to accrue evidence for acquired DNA damage in multiple tissues obtained non-invasively from children with obesity. Our findings instigate that biomonitoring of ‘genome health’ for pre-cancerous molecular and morphological markers in obese patients may inform prioritization and severity of clinical intervention measures to prevent malignancy

Physiological importance of various NFκB family members in regulating intestinal responses to injury

As key regulators of cell survival, proliferation and immune responses, the NFκB family of transcription factors, which signal via the classical and alternative activation pathways, play important roles in intestinal physiology. The pro-inflammatory function of the classical NFκB activation pathway has previously been demonstrated in various animal models of intestinal inflammation. Persistent activation of this pathway has also been detected in the colonic mucosa of patients with inflammatory bowel diseases (IBD). Conversely, several studies in transgenic mice have shown that disruption of the classical NFκB activation pathway specifically in intestinal epithelial cells renders these cells more susceptible to undergoing apoptosis and also results in increased susceptibility to developing colitis. However, the specific roles of individual members of the NFκB family and in particular the role of the alternative NFκB activation pathway in regulating the susceptibility of the intestine to apoptosis, inflammation and colitis associated colon cancer have not been well defined. We therefore hypothesised that individual members of the NFκB family of proteins which signal via the classical and alternative activation pathways specifically regulate intestinal epithelial cell proliferation, apoptosis and colonic inflammation, consequently modulating susceptibility to developing inflammation associated colon cancer. Most of these aims were addressed using transgenic mice with germline deletions of c-Rel, NFκB1, and NFκB2, along with their wild-type counterparts. Intestinal epithelial apoptosis was induced using either γ-irradiation or irinotecan administration. Colitis was induced using dextran sulphate sodium (DSS) and colitis associated cancer by a combination of azoxymethane (AOM) and DSS. In vitro studies were performed in HCT116 colon carcinoma cells. Disruption of classical NFκB signalling by deletion of NFκB1 but not c-Rel sensitised intestinal epithelial cells to undergo apoptosis following γ-irradiation and irinotecan administration. Deleting either c-Rel or NFκB1 also exacerbated the severity of experimental acute and chronic DSS-induced colitis in mice. However, only c-Rel-null mice showed an increase in AOM/DSS induced colonic tumours. This was associated with c-Rel, but not NFκB1 deletion resulting in persistent colonic epithelial mitosis and increased crypt regeneration following DNA damage. Disruption of the alternative NFκB activation pathway by either deleting NFκB2 (in vivo) or suppressing its expression (in vitro) also increased the susceptibility of intestinal epithelial cells to undergo apoptosis following DNA damaging stimuli. Conversely and intriguingly however, deleting NFκB2 also protected mice from developing colitis and colitis associated colon cancer. Specific members of the NFκB family therefore play different roles in regulating the intestinal responses to various types of cellular injury. NFκB2 in particular appears to be essential for developing colitis and its associated cancer. Pharmacological inhibition of NFκB2 may therefore be a promising novel therapeutic strategy for IBD, whereas inhibition of c-Rel signalling may increase susceptibility to developing colitis and its associated colon cancer