Molecular and genetic defects in colorectal tumorigenesis

LncRNA SNHG15: A potential therapeutic target in the treatment of colorectal cancer

The global burden of colorectal cancer (CRC) is increasing annually. CRC could develop from genetic and phenotypic factors involving changes in gene expression. Incredibly, the human genome transcribes into non-coding RNAs, among which long non-coding RNAs (lncRNAs) signify the most crucial part of the transcriptome in multicellular organisms. lncRNAs affect gene expression at multiple levels, from transcription to protein localization and stability. Recent studies have implicated lncRNA small nucleolar RNA host gene 15 (SNHG15) in cancers occurrence and progression. Previously, an indication suggests SNHG15 overexpression triggers proliferation, metastasis, and impedes apoptosis in CRC. Further, through its activity of binding micro-RNAs, lncRNA SNHG15 modulates genes associated with CRC progression and promotes CRC resistance to chemotherapeutic drugs. Here we reviewed recent findings on the various mechanisms and roles of lncRNA SNHG15 implicated in CRC tumorigenesis. We further highlight how SNHG15 plays a vital role in regulating critical pathways linked to the development and progression of CRC. Finally, we highlight how SNHG15 can be modulated for CRC treatments and the various therapeutic strategies to be implored when targeting SNHG15 in the context of CRC treatments. Findings from these studies present SNHG15 as a potential therapeutic target for preventing and treating CRC.

Emerging trends in colorectal cancer: Dysregulated signaling pathways (Review)

Colorectal cancer (CRC) is the third most frequently detected type of cancer, and the second most common cause of cancer‑related mortality globally. The American Cancer Society predicted that approximately 147,950 individuals would be diagnosed with CRC, out of which 53,200 individuals would succumb to the disease in the USA alone in 2020. CRC‑related mortality ranks third among both males and females in the USA. CRC arises from 3 major pathways: i) The adenoma‑carcinoma sequence; ii) serrated pathway; and iii) the inflammatory pathway. The majority of cases of CRC are sporadic and result from risk factors, such as a sedentary lifestyle, obesity, processed diets, alcohol consumption and smoking. CRC is also a common preventable cancer. With widespread CRC screening, the incidence and mortality from CRC have decreased in developed countries. However, over the past few decades, CRC cases and mortality have been on the rise in young adults (age, <50 years). In addition, CRC cases are increasing in developing countries with a low gross domestic product (GDP) due to lifestyle changes. CRC is an etiologically heterogeneous disease classified by tumor location and alterations in global gene expression. Accumulating genetic and epigenetic perturbations and aberrations over time in tumor suppressor genes, oncogenes and DNA mismatch repair genes could be a precursor to the onset of colorectal cancer. CRC can be divided as sporadic, familial, and inherited depending on the origin of the mutation. Germline mutations in APC and MLH1 have been proven to play an etiological role, resulting in the predisposition of individuals to CRC. Genetic alterations cause the dysregulation of signaling pathways leading to drug resistance, the inhibition of apoptosis and the induction of proliferation, invasion and migration, resulting in CRC development and metastasis. Timely detection and effective precision therapies based on the present knowledge of CRC is essential for successful treatment and patient survival. The present review presents the CRC incidence, risk factors, dysregulated signaling pathways and targeted therapies.

Role of miRNAs in Sigmoid Colon Cancer: A Search for Potential Biomarkers

The aberrant expression of microRNAs in known to play a crucial role in carcinogenesis. Here, we evaluated the miRNA expression profile of sigmoid colon cancer (SCC) compared to adjacent-to-tumor (ADJ) and sigmoid colon healthy (SCH) tissues obtained from colon biopsy extracted from Brazilian patients. Comparisons were performed between each group separately, considering as significant p-values < 0.05 and |Log2(Fold-Change)| > 2. We found 20 differentially expressed miRNAs (DEmiRNAs) in all comparisons, two of which were shared between SCC vs. ADJ and SCC vs. SCH. We used miRTarBase, and miRTargetLink to identify target-genes of the differentially expressed miRNAs, and DAVID and REACTOME databases for gene enrichment analysis. We also used TCGA and GTEx databases to build miRNA-gene regulatory networks and check for the reproducibility in our results. As findings, in addition to previously known miRNAs associated with colorectal cancer, we identified three potential novel biomarkers. We showed that the three types of colon tissue could be clearly distinguished using a panel composed by the 20 DEmiRNAs. Additionally, we found enriched pathways related to the carcinogenic process in which miRNA could be involved, indicating that adjacent-to-tumor tissues may be already altered and cannot be considered as healthy tissues. Overall, we expect that these findings may help in the search for biomarkers to prevent cancer progression or, at least, allow its early detection, however, more studies are needed to confirm our results.

Establishment and characterization of a novel cell line (cc‑006cpm8) of moderately/poorly differentiated colorectal adenocarcinoma derived from a primary tumor of a patient

In the present study, the cc‑006cpm8 novel colon cell line was established from a sample of right colorectal adenocarcinoma obtained from a woman with liver metastasis. It was possible to culture this cell line for ≥100 passages in vitro with vigorous growth. Morphologically, the cells grew as several layers with tight adhesion to the surface of the culture plate. The morphological, immunological and ultrastructural features of these cells suggested their epithelial origin. The characterization of this cell line indicated a doubling time of 27 h, a colony forming efficiency of 73.2% in semisolid media and a plate efficiency of 66.5% in liquid culture. The modal number of chromosomes was 50. In vivo, the cc‑006cpm8 cells underwent tumorigenesis in all nude mice used. Immunohistochemical analysis demonstrated that mutS homolog 2 (MSH2) and MSH6 were expressed; however, mutL homolog 1 and postmeiotic segregation 2 were downregulated in cc‑006cpm8 cells. To determine the mutation profile of the cell line analyzed, exome capture DNA sequencing was performed. The results revealed 20 hypermutated exons comprising single nucleotide polymorphisms, and insertion and deletions (InDels), including single nucleotide variants of mucin (MUC)19, MUC16, MUC12, filaggrin and AHNAK nucleoprotein 2, and InDels of β defensin‑126, microRNA‑3665, WNK lysine deficient protein kinase 1 and SLAIN motif‑containing protein 1. In addition, commonly mutated genes in colorectal cancer and exon mutations of genes in cc‑006cpm8 cells were analyzed, including adenomatous polyposis coli, tumor protein p53, Drosophila mothers against decapentaplegic 4, phosphatidylinositol‑4,5‑bisphosphate 3‑kinase catalytic subunit α and Kirsten rat sarcoma, and genes associated with the DNA mismatch repair pathway were investigated.

The molecular characteristics of colorectal cancer: Implications for diagnosis and therapy

Colorectal cancer (CRC) results from the progressive accumulation of multiple genetic and epigenetic aberrations within cells. The progression from colorectal adenoma to carcinoma is caused by three major pathways: Microsatellite instability, chromosomal instability and CpG island methylator phenotype. A growing body of scientific evidences suggests that CRC is a heterogeneous disease, and genetic characteristics of the tumors determine their prognostic outcome and response to targeted therapies. Early diagnosis and effective targeted therapies based on a current knowledge of the molecular characteristics of CRC are essential to the successful treatment of CRC. Therefore, the present review summarized the current understanding of the molecular characteristics of CRC, and discussed its implications for diagnosis and targeted therapy.

Colorectal Cancer: From the Genetic Model to Posttranscriptional Regulation by Noncoding RNAs

Colorectal cancer is the third most common form of cancer in developed countries and, despite the improvements achieved in its treatment options, remains as one of the main causes of cancer-related death. In this review, we first focus on colorectal carcinogenesis and on the genetic and epigenetic alterations involved. In addition, noncoding RNAs have been shown to be important regulators of gene expression. We present a general overview of what is known about these molecules and their role and dysregulation in cancer, with a special focus on the biogenesis, characteristics, and function of microRNAs. These molecules are important regulators of carcinogenesis, progression, invasion, angiogenesis, and metastases in cancer, including colorectal cancer. For this reason, miRNAs can be used as potential biomarkers for diagnosis, prognosis, and efficacy of chemotherapeutic treatments, or even as therapeutic agents, or as targets by themselves. Thus, this review highlights the importance of miRNAs in the development, progression, diagnosis, and therapy of colorectal cancer and summarizes current therapeutic approaches for the treatment of colorectal cancer.

NOD2 mutations and colorectal cancer - Where do we stand?

Due to the overwhelming burden of colorectal cancer (CRC), great effort has been placed on identifying genetic mutations that contribute to disease development and progression. One of the most studied polymorphisms that could potentially increase susceptibility to CRC involves the nucleotide-binding and oligomerization-domain containing 2 (NOD2) gene. There is growing evidence that the biological activity of NOD2 is far greater than previously thought and a link with intestinal microbiota and mucosal immunity is increasingly sought after. In fact, microbial composition may be an important contributor not only to inflammatory bowel diseases (IBD) but also to CRC. Recent studies have showed that deficient NOD2 function confers a communicable risk of colitis and CRC. Despite the evidence from experimental models, population-based studies that tried to link certain NOD2 polymorphisms and an increase in CRC risk have been described as conflicting. Significant geographic discrepancies in the frequency of such polymorphisms and different interpretations of the results may have limited the conclusions of those studies. Since being first associated to IBD and CRC, our understanding of the role of this gene has come a long way, and it is tempting to postulate that it may contribute to identify individuals with susceptible genetic background that may benefit from early CRC screening programs or in predicting response to current therapeutic tools. The aim of this review is to clarify the status quo of NOD2 mutations as genetic risk factors to chronic inflammation and ultimately to CRC. The use of NOD2 as a predictor of certain phenotypic characteristics of the disease will be analyzed as well.

Chemopreventive activity of grape juice concentrate (G8000TM) on rat colon carcinogenesis induced by azoxymethane

Colorectal cancer is the third most common cancer worldwide in both sexes, with similar geographic patterns between genders. This neoplasm has good prognosis if the disease is diagnosed at early stages. The aim of this study was to evaluate the effect of red grape juice on the expression of COX-2 and Ki-67 expression following colon carcinogenesis induced by azoxymethane (AOM). Thirty-five rats were randomly distributed into seven groups (n=5 per group): G1: SHAM or negative control received only saline; G2 (positive control): animals received 15 mg/kg AOM; G3: animals received 1% red grape juice 2 weeks before the administration of AOM; G4: animals received 2% red grape juice 2 weeks before the administration of AOM; G5: animals received 1% red grape juice 4 weeks after the last administration of AOM; G6: animals received 2% red grape juice 4 weeks after the last administration of AOM; G7: animals received only 2% red grape juice. COX-2 mRNA expression was reduced in animals treated with 1% red grape juice before AOM induction or 2% red grape juice after AOM induction. COX-2 immunoexpression was also reduced to groups treated with red grape juice at 1% before and after AOM induction or 2% red grape juice after AOM induction. Decreased immunoexpression of Ki-67 positive cells was observed in animals treated with 1% grape juice before AOM-treated animals. Taken together, grape juice concentrate is able to exert some chemopreventive activity on rat colon carcinogenesis.

Suppression of β-catenin and cyclooxygenase-2 expression and cell proliferation in azoxymethane-induced colonic cancer in rats by rice bran phytic acid (PA)

BACKGROUND

Phytic acid (PA) is a polyphosphorylated carbohydrate that can be found in high amounts in most cereals, legumes, nut oil, seeds and soy beans. It has been suggested to play a significant role in inhibition of colorectal cancer. This study was conducted to investigate expression changes of β-catenin and cyclooxygenase-2 (COX-2) and cell proliferation in the adenoma-carcinoma sequence after treatment with rice bran PA by immunocytochemistry.

MATERIALS AND METHODS

Seventy-two male Sprague-Dawley rats were divided into 6 equal groups with 12 rats in each group. For cancer induction two intraperitoneal injections of azoxymethane (AOM) were given at 15 mg/kg bodyweight over a 2-weeks period. During the post initiation phase, two different concentrations of PA, 0.2% (w/v) and 0.5% (w/v) were administered in the diet.

RESULTS

Results of β-catenin, COX-2 expressions and cell proliferation of Ki-67 showed a significant contribution in colonic cancer progression. For β-catenin and COX-2 expression, there was a significant difference between groups at p<0.05. With Ki-67, there was a statistically significant lowering the proliferating index as compared to AOM alone (p<0.05). A significant positive correlation (p=0.01) was noted between COX-2 expression and proliferation. Total β-catenin also demonstrated a significant positive linear relationship with total COX-2 (p=0.044).

CONCLUSIONS

This study indicated potential value of PA extracted from rice bran in reducing colonic cancer risk in rats.

Cyclin D1 G870A polymorphism and colorectal cancer susceptibility: a meta-analysis of 20 populations

PURPOSE

Studies investigating the association between genetic polymorphism of cyclin D1 (CCND1) G870A and risk of colorectal cancer (CRC) reported conflicting results. In order to derive a more precise estimation of the relationship, a meta-analysis was performed.

MATERIALS AND METHODS

We performed an extensive search of relevant studies and carried out a meta-analysis, including 20 studies with 5,975 cases and 8,333 controls, to obtain a more precise estimate.

RESULTS

Overall, significantly elevated colorectal cancer risk was associated with variant allele 870A when all studies were pooled (AA vs. GG: OR = 1.23, 95% CI = 1.04-1.44; GA vs. GG: OR = 1.13, 95% CI = 1.01-1.26; dominant model: OR = 1.16, 95% CI = 1.03-1.31). In the subgroup analysis by ethnicity, significantly increased risks were detected among Caucasians (AA vs. GG: OR = 1.27, 95% CI = 1.04-1.44; dominant model: OR = 1.17, 95% CI = 1.02-1.34).We also observed sporadic CRC with an increased cancer susceptibility (AA vs. GG: OR = 1.24, 95% CI = 1.04-1.48; dominant model: OR = 1.17, 95% CI = 1.04-1.33), when colorectal cancer was stratified into sporadic CRC and hereditary nonpolyposis colorectal cancer (HNPCC). However, no significant associations were found in both Asians and HNPCC patients for all genetic models.

CONCLUSION

Result suggests that the cyclin D1 870A allele is a low-penetrant risk factor for developing sporadic colorectal cancer, especially among Caucasians.

CARD15 mutations and colorectal cancer in a South European country

PURPOSE

CARD15 mutations are associated with higher susceptibility to Crohn's disease (CD) and longstanding colonic CD increases the risk of developing colorectal cancer (CRC). The relation between these mutations and sporadic CRC remains controversial. The aim of this study was to assess whether germline and/or somatic CARD15 mutations are risk factors for sporadic CRC in Portugal and whether there are genotype-phenotype correlations in these patients.

METHODS

The three main CARD15 mutations (R702W, G908R and 3020insC) were researched in 112 sporadic CRC patients and 152 healthy subjects.

RESULTS

Overall, CARD15 mutations were found in 18 patients (16.1%) and in 15 controls (9.9%; p = 0.132). Individually, the incidence of R702W was significantly higher in patients than in controls (12.5% vs. 5.3%, p = 0.035), whereas the genotype frequencies for G908R (2.7% vs. 3.3%) and 3020insC (0.9% vs. 1.3%) were not statistically different between the two groups. Entire genotypic agreement was found in patients genotyped for blood and neoplastic DNA. A significantly higher incidence of CARD15 mutations was detected in patients with CRC diagnosed under 60 years old (28.6% vs. 10.4%, p = 0.015) and in female patients (24.4% vs. 10.4%, p = 0.048). No associations were found between CARD15 mutations and family history, symptoms or CRC pathologic characteristics.

CONCLUSIONS

The CARD15 R702W variant might be a predisposing factor to sporadic CRC in Portugal, particularly in patients under 60-years old and in female patients. This susceptibility appears to be linked with germline CARD15 mutations. Nevertheless, we have found no evidence that CARD15 mutations predict the pathologic characteristics of CRC.

Sessile serrated adenomas strongly predispose to synchronous serrated polyps in non-syndromic patients

AIMS

To determine the prevalence of various colonic polyps removed during a recent 8-month period; to determine the interobserver agreement in the diagnosis of serrated polyps; and to determine if harbouring a sessile serrated adenoma (SSA) predisposes to the presence of synchronous polyps with similar histology.

METHODS AND RESULTS

All polyps resected during an 8-month period at a single tertiary medical centre were analysed. We also analysed all polyps in patients with an SSA or SSA with dysplasia since 2003. SSAs accounted for 4.3% of colonic polyps removed during an 8-month period. A review of 276 serrated polyps by two pathologists revealed good interobserver agreement (kappa = 0.66). Patients with one SSA were more likely to harbour additional serrated polyps. After removal of the index SSA, 18% of their remaining polyps were SSAs, SSAs with dysplasia, and traditional serrated adenomas, contrasting with the approximately 5% prevalence of these polyps in the control population. The hyperplastic polyps in the study population were also twice as likely to occur proximal to the splenic flexure.

CONCLUSIONS

These data indicate that there is a strong colonic mucosal field defect in patients with sporadic SSAs that predispose them to develop additional serrated polyps.

Peroxisome proliferator-activated receptor-γ 34C>G polymorphism and colorectal cancer risk: A meta-analysis

AIM: To investigate the association between peroxisome proliferator-activated receptor-γ (PPAR-γ) gene polymorphism 34 C>G and colorectal cancer (CRC), a meta-analysis review was performed in this report.

METHODS: A systematic literature search and selection of eligible relevant studies were carried out. Nine independent studies with a total number of 4533 cases and 6483 controls were included in the meta-analysis on the association between polymorphism 34 C>G and CRC.

RESULTS: There was no evidence for the association between PPAR-γ 34 C>G and CRC if all of the subjects in the nine studies were included. However, CG + GG showed a marginally significant difference from CC (OR = 0.84, 95% CI: 0.69-1.01, P = 0.07) in random-effect model. Stratified meta-analysis indicated that PPAR-γ 34 C>G was associated with colon cancer (OR = 0.8, 95% CI: 0.65-0.99, P = 0.04) in random-effect model, and the G allele decreased colon cancer risk. No significant association was observed between PPAR-γ 34 C>G and rectal cancer.

CONCLUSION: PPAR-γ 34 C>G is associated with colon cancer risk, but not associated with CRC and rectal cancer risk.

Colon-targeted delivery of live bacterial cell biotherapeutics including microencapsulated live bacterial cells

There has been an ample interest in delivery of therapeutic molecules using live cells. Oral delivery has been stipulated as best way to deliver live cells to humans for therapy. Colon, in particular, is a part of gastrointestinal (GI) tract that has been proposed to be an oral targeted site. The main objective of these oral therapy procedures is to deliver live cells not only to treat diseases like colorectal cancer, inflammatory bowel disease, and other GI tract diseases like intestinal obstruction and gastritis, but also to deliver therapeutic molecules for overall therapy in various diseases such as renal failure, coronary heart disease, hypertension, and others. This review provides a comprehensive summary of recent advancement in colon targeted live bacterial cell biotherapeutics. Current status of bacterial cell therapy, principles of artificial cells and its potentials in oral delivery of live bacterial cell biotherapeutics for clinical applications as well as biotherapeutic future perspectives are also discussed in our review.

Two subtypes of mucinous adenocarcinoma of the colorectum: clinicopathological and genetic features

BACKGROUND

This work is aimed at comparing mucinous colorectal adenocarcinomas (MUC) and non-mucinous colorectal adenocarcinomas (non-MUC), and at verifying the existence of two different subgroups of MUC, in terms of clinicopathological features, chromosomal alterations, and outcome, in a geographical area where mucinous colorectal cancer resulted as being very frequent.

METHODS

One hundred and fifty-six unselected patients who underwent curative colorectal resection for sporadic colorectal cancer over a 4-year period were evaluated for histological classification as to MUC and non-MUC subtype, for microsatellite instability (MSI) using six microsatellite markers, and for the presence of p27, Fhit, and cyclooxygenase-2 (Cox-2). Molecular data, immunohistochemical results, recurrence frequency, and patient survival were analyzed statistically in relation to histological subtypes.

RESULTS

MUC accounted for 38.5% of all colorectal carcinomas. Compared to non-MUCs, MUCs were more frequently located in the proximal colon (p < 0.001), and more frequently showed MSI phenotype (p < 0.001), altered protein expression of hMlh1 (p = 0.030), Fhit (p <0.001), and p27 (p < 0.001). Compared to MUC with microsatellite-stable (MSS) phenotype, MUC with MSI more frequently resulted as being located in the proximal colon (p = 0.013), and more frequently showed altered expression of hMlh1 (p < 0.001), hMsh2 (p = 0.008), Fhit (p < 0.001), and p27 (p = 0.015). Significantly better survival of patients with proximal MUC (p = 0,012), with MSI MUC (p = 0.017), and with MUC with altered p27 expression (p = 0.02).

CONCLUSION

The results of the present study confirm that MUC represents distinct clinicopathological and genetic features as compared to non-mucinous tumors and support the hypothesis that MUC includes two subtypes with different genetic pathways and behavior.

Distinct molecular patterns based on proximal and distal sporadic colorectal cancer: arguments for different mechanisms in the tumorigenesis

BACKGROUND AND AIMS

Colorectal cancer (CRC) ranks as the fourth most frequently diagnosed cancer worldwide. CRCs that arise proximally or distally to the splenic flexure show differences in epidemiologic incidence, morphology, and molecular alterations, suggesting the existence of two categories of CRC based on the site of origin. The aim of the present work is to investigate the histological and molecular differences between CRCs located proximally and distally to the splenic flexure, and their potential involvement in tumor prognosis and therapeutic strategies.

METHODS

We evaluated 120 patients affected by sporadic CRC for clinicopathologic features, microsatellite instability (MSI), loss of heterozygosity (LOH) of chromosomes 18q, 8p, and 4p; they were also investigated for hMlh1, hMsh2, Fhit, p27, and Cox-2 immunostaining.

RESULTS

The mucinous histotype was more frequent in the proximal than in the distal CRCs (p<0.004). The frequency of MSI phenotype was higher in proximal than in distal tumors (p<0.001); moreover, reduced or absent hMlh1, Fhit, p27 immunohistochemical expressions were more frequent in proximal than in distal tumors (p<0.001 and 0.01 for p27). In contrast, the frequency of LOH in 18q was higher in distal than in proximal tumors (p=0.002). No significant differences were observed between proximal and distal tumors in the frequency of LOH in 8p and altered expression of hMsh2 and p53 protein.

CONCLUSION

These different features may reflect different genetic pathways of carcinogenesis and support the hypothesis of a different mechanism of cancer development between the proximal and the distal colon, with potential implications in the therapeutic approach.

Relation between common polymorphisms in genes related to inflammatory response and colorectal cancer

AIM: To investigate the association between common single nucleotide polymorphisms (SNPs) in inflammatory response-related genes such as interleukin (IL)-6, IL-8, tumor necrosis factor α (TNFα), peroxisome proliferators-activated receptor γ (PPARγ), intercellular adhesion molecule-1 (ICAM-1) and the risk of colorectal cancer (CRC) in a group of Greek patients.

METHODS: The study group consisted of 222 CRC patients and 200 healthy controls. Genotyping was performed using allele-specific PCR of PRC-RFLP and the results were confirmed by sequencing. We studied the association of SNPs in the IL-6 (-174G > C), IL-8 (-251T > A), TNFα (-308G > A), ICAM-1 (R241G and K469E), and PPARγ (Pro12Ala) genes and the risk of CRC.

RESULTS: The IL-6 -174G, R241 and K469 alleles of ICAM-1 were associated with increased risk of CRC (OR = 1.77, 95% CI: 1.34-2.34; OR = 1.83, 95% CI: 1.23-2.72; and OR = 1.35, 95% CI: 1.03-1.77 respectively). The IL-8 and TNFα polymorphisms had no effect. Whereas the PPARγ Pro12 genotype was associated with increased risk of disease (OR = 1.78, 95% CI: 1.25-2.49).

CONCLUSION: The association between common SNPs in immunologic response-related genes and CRC is reported in the present study. Apart from shedding light on the mechanisms of malignancy initiation and progression, SNPs may improve appropriate screening for sub-populations at risk.