Association study of the let-7 miRNA-complementary site variant in the 3' untranslated region of the KRAS gene in stage III colon cancer (NCCTG N0147 Clinical Trial)

The Clinical Significance of MicroRNAs in Colorectal Cancer Signaling Pathways: A Review

Colorectal carcinoma (colon and rectum) is currently considered among the most prevalent malignancies of Western societies. The pathogenesis and etiological mechanisms underlying colorectal cancer (CRC) development remain complex and heterogeneous. The homeostasis and function of normal human intestinal cells is highly regulated by microRNAs. Therefore, it is not surprising that mutations and inactivation of these molecules appear to be linked with progression of colorectal tumors. Recent studies have reported significant alterations of microRNA expression in adenomas and CRCs compared with adjacent normal tissues. This observed deviation has been proposed to correlate with the progression and survival of disease as well as with choice of optimal treatment and drug resistance. MicroRNAs can adopt either oncogenic or tumor-suppressive roles during regulation of pathways that drive carcinogenesis. Typically, oncogenic microRNAs termed oncomirs, target and silence endogenous tumor-suppressor genes. On the other hand, tumor-suppressive microRNAs are critical in downregulating genes associated with cell growth and malignant capabilities. By extensively evaluating robust studies, we have emphasized and distinguished a discrete set of microRNAs that can modulate tumor progression by silencing specific driver genes crucial in signaling pathways including Wnt/b-catenin, epidermal growth factor receptor, P53, mismatch repair DNA repair, and transforming-growth factor beta.

Tumor Microenvironment Remodeling in Gastrointestinal Cancer: Role of miRNAs as Biomarkers of Tumor Invasion

Gastrointestinal (GI) cancers are the most frequent neoplasm, responsible for half of all cancer-related deaths. Metastasis is the leading cause of death from GI cancer; thus, studying the processes that regulate cancer cell migration is of paramount importance for the development of new therapeutic strategies. In this review, we summarize the mechanisms adopted by cancer cells to promote cell migration and the subsequent metastasis formation by highlighting the key role that tumor microenvironment components play in deregulating cellular pathways involved in these processes. We, therefore, provide an overview of the role of different microRNAs in promoting tumor metastasis and their role as potential biomarkers for the prognosis, monitoring, and diagnosis of GI cancer patients. Finally, we relate the possible use of nutraceuticals as a new strategy for targeting numerous microRNAs and different pathways involved in GI tumor invasiveness.

Bioinformatic Analysis Identified Potentially Prognostic Long Noncoding RNAs and MicroRNAs for Gastric Cancer

Gastric cancer (GC) is the fifth most common malignant tumor in the world. The present study was performed to discover the potential diagnostic and therapeutic long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) of GC. Data used in this study to identify differentially expressed lncRNAs (DElncRNAs) and miRNAs (DEmiRNAs) were obtained from 187 GC tissues and 32 adjacent nontumor tissues. The total clinical data on GC included 187 cases. The above data were from the TCGA database. RStudio/Bioconductor software was used to conduct univariate analysis, the least absolute shrinkage and selection operator (LASSO) Cox, and multivariate Cox proportional risk regression for the DElncRNAs and DEmiRNAs. Clinical information was analyzed through univariate and multivariate Cox analysis. Results: five lncRNAs (AC007785.3, AC079385.3, LINC00392, LINC01729, and U95743.1) and two miRNAs (hsa-miR-3174, hsa-miR-605) were proven to be independent prognostic indicators of GC. Results of the Kaplan-Meier survival analysis showed that AC007785.3, AC079385.3, LINC01729, miR-3174, and miR-605 were significantly correlated with OS of GC. The target genes of AC079385.3, miR-3174, and miR-605 were obtained and clustered mainly on MAPK and cGMP-PKG signaling pathways. The clinical data showed that age and clinicopathologic stage were correlated with the prognosis of GC. Furthermore, AC007785.3 was associated with metastasis of GC, and miR-3174 was associated with the primary tumor condition of GC. We identified three lncRNAs (AC007785.3, AC079385.3, LINC01729), two miRNAs (miR-3174, miR-605), and clinical factors related to the pathogenesis and prognosis of GC. Our predicted results provide a possible entry point for the study of prognostic markers for GC.

Regulation of KRAS protein expression by miR-544a and KRAS-LCS6 polymorphism in wild-type KRAS sporadic colon adenocarcinoma

Colorectal carcinoma (CRC) results from the accumulation of genetic mutations and alterations in signaling pathways. KRAS is mutated in 40% of CRC cases and is involved in increased tumor cells proliferation and survival. Although KRAS mutations are a dominant event in CRC tumorigenesis, increased wild-type KRAS expression has a similar effect on accelerated tumor growth. In this study, we investigated the KRAS status in correlation with clinicopathological features in sporadic CRC and more importantly the role of let-7a-5p and miR-544a-3p in the regulation of wild-type KRAS protein expression in the tumor center (T1) and invasive tumor front (T2). Analysis showed that 39.1% of tumor samples had KRAS mutations. In wild-type KRAS tumors, 62.0% were positive for KRAS protein expression and there was a higher percentage of KRAS-positive tumor cells and a higher intensity of immunohistochemical reaction in T2 than in T1 samples. This could not be attributed to differences in KRAS mRNA levels, suggesting regulation via miR-544a-3p expression which was significantly decreased in T2 samples. Furthermore, we demonstrated that tumor samples carrying the KRAS-LCS6 variant allele had significantly higher protein expression of the wild-type KRAS. Our results suggest the role of the KRAS-LCS6 polymorphism and miR-544a-3p expression in the regulation of wild-type KRAS protein expression in sporadic CRC.

Ketogenic Diet in Cancer Prevention and Therapy: Molecular Targets and Therapeutic Opportunities

Although cancer is still one of the most significant global challenges facing public health, the world still lacks complementary approaches that would significantly enhance the efficacy of standard anticancer therapies. One of the essential strategies during cancer treatment is following a healthy diet program. The ketogenic diet (KD) has recently emerged as a metabolic therapy in cancer treatment, targeting cancer cell metabolism rather than a conventional dietary approach. The ketogenic diet (KD), a high-fat and very-low-carbohydrate with adequate amounts of protein, has shown antitumor effects by reducing energy supplies to cells. This low energy supply inhibits tumor growth, explaining the ketogenic diet's therapeutic mechanisms in cancer treatment. This review highlights the crucial mechanisms that explain the ketogenic diet's potential antitumor effects, which probably produces an unfavorable metabolic environment for cancer cells and can be used as a promising adjuvant in cancer therapy. Studies discussed in this review provide a solid background for researchers and physicians to design new combination therapies based on KD and conventional therapies.

Mir-488 alleviates chemoresistance and glycolysis of colorectal cancer by targeting PFKFB3

BACKGROUND

Considering the boosting effect of glycolysis on tumor chemoresistance, this investigation aimed at exploring whether miR-488/PFKFB3 axis might reduce drug resistance of colorectal cancer (CRC) by affecting glycolysis, proliferation, migration, and invasion of CRC cells.

METHOD

Totally, 288 CRC patients were divided into metastasis/recurrence group (n = 107) and non-metastasis/recurrence group (n = 181) according to their prognosis about 1 year after the chemotherapy, and their 3-year overall survival was also tracked. Besides, miR-488 expression was determined in peripheral blood of CRC patients and also in CRC cell lines (ie, W620, HT-29, Lovo, and HCT116). The targeted relationship between miR-488 and PFKFB3 was predicted by Targetscan software and confirmed by dual-luciferase reporter gene assay. Moreover, glycolysis and drug tolerance of CRC cells lines were assessed.

RESULTS

MiR-488 expression was significantly decreased in metastatic/recurrent CRC patients than those without metastasis/recurrence (P < .05), and lowly expressed miR-488 was suggestive of unfavorable 3-year survival, large tumor size, poor differentiation, in-depth infiltration, and advanced Duke stage of CRC patients (P < .05). Besides, CRC cell lines transfected by miR-488 mimic demonstrated decreases in glucose uptake and lactate secretion, increases in oxaliplatin/5-Fu-sensistivity, as well as diminished capability of proliferating, invading, and migratory (P < .05), which were reversible by extra transfection of pcDNA3.1-PFKFB3 (ie, miR-488 mimic + pcDNA3.1-PFKFB3 group). Finally, the mRNA level of PFKFB3 was down-regulated by miR-488 mimic in CRC cell lines after being targeted by it (P < .05).

CONCLUSION

The miR-488/PFKFB3 axis might clinically refine chemotherapeutic efficacy of CRC, given its modifying glycolysis and metastasis of CRC cells.

Mir-488 alleviates chemoresistance and glycolysis of colorectal cancer by targeting PFKFB3

BACKGROUND

Considering the boosting effect of glycolysis on tumor chemoresistance, this investigation aimed at exploring whether miR-488/PFKFB3 axis might reduce drug resistance of colorectal cancer (CRC) by affecting glycolysis, proliferation, migration, and invasion of CRC cells.

METHOD

Totally, 288 CRC patients were divided into metastasis/recurrence group (n = 107) and non-metastasis/recurrence group (n = 181) according to their prognosis about 1 year after the chemotherapy, and their 3-year overall survival was also tracked. Besides, miR-488 expression was determined in peripheral blood of CRC patients and also in CRC cell lines (ie, W620, HT-29, Lovo, and HCT116). The targeted relationship between miR-488 and PFKFB3 was predicted by Targetscan software and confirmed by dual-luciferase reporter gene assay. Moreover, glycolysis and drug tolerance of CRC cells lines were assessed.

RESULTS

MiR-488 expression was significantly decreased in metastatic/recurrent CRC patients than those without metastasis/recurrence (P < .05), and lowly expressed miR-488 was suggestive of unfavorable 3-year survival, large tumor size, poor differentiation, in-depth infiltration, and advanced Duke stage of CRC patients (P < .05). Besides, CRC cell lines transfected by miR-488 mimic demonstrated decreases in glucose uptake and lactate secretion, increases in oxaliplatin/5-Fu-sensistivity, as well as diminished capability of proliferating, invading, and migratory (P < .05), which were reversible by extra transfection of pcDNA3.1-PFKFB3 (ie, miR-488 mimic + pcDNA3.1-PFKFB3 group). Finally, the mRNA level of PFKFB3 was down-regulated by miR-488 mimic in CRC cell lines after being targeted by it (P < .05).

CONCLUSION

The miR-488/PFKFB3 axis might clinically refine chemotherapeutic efficacy of CRC, given its modifying glycolysis and metastasis of CRC cells.

Regulatory mechanisms of microRNAs in colorectal cancer and colorectal cancer stem cells

Colorectal cancer (CRC) is one of the most lethal and hard-to-treat cancers in the world, which in its advanced stages, surgery and chemotherapy are the main common treatment approaches. The microRNAs (miRNAs), as novel markers for CRC detection, promote their regulatory effects via the 3'-untranslated binding region (3'-UTR) of target messenger RNA in posttranscriptional regulation of genes and also play a pivotal role in modulating resistance to chemotherapeutic agents. These small noncoding RNAs have also a critical role in CRC stem cells (CRCSCs) regulation, comprising self-renewal, differentiation, and tumorigenesis. Cancer stem cells (CSCs) are distinctive cell types inside a tumor tissue that are believed to derive from normal somatic stem cells. The CSCs have self-renewal abilities, angiogenesis, as well as specific surface markers expression characteristics. Furthermore, they are frequently criticized for tumor maintenance, treatment resistance, tumor development, and distant metastasis. In this review, we discuss the current understandings of CRCSCs and their environment with a focus on the role of miRNAs on the regulation of CSCs and their targeting application in CRC treatment.

miR-31-3p Expression and Benefit from Anti-EGFR Inhibitors in Metastatic Colorectal Cancer Patients Enrolled in the Prospective Phase II PROSPECT-C Trial

PURPOSE

Anti-EGFR mAbs are effective in the treatment of metastatic colorectal cancer (mCRC) patients. RAS status and tumor location (sidedness) are predictive markers of patients' response to anti-EGFR mAbs. Recently, low miR-31-3p expression levels have been correlated with clinical benefit from the anti-EGFR mAb cetuximab. Here, we aimed to validate the predictive power of miR-31-3p in a prospective cohort of chemorefractory mCRC patients treated with single-agent anti-EGFR mAbs.

EXPERIMENTAL DESIGN

miR-31-3p was tested by in situ hybridization (ISH) in 91 pretreatment core biopsies from metastatic deposits of 45 patients with mCRC. Sequential tissue biopsies obtained before treatment, at the time of partial response, and at disease progression were tested to monitor changes in miR-31-3p expression overtreatment. miR-31-3p expression, sidedness, and RAS status in pretreatment cell-free DNA were combined in multivariable regression models to assess the predictive value of each variable alone or in combination.

RESULTS

Patients with low miR-31-3p expression in pretreatment biopsies showed better overall response rate, as well as better progression-free survival and overall survival, compared to those with high miR-31-3p expression. The prognostic effect of miR-31-3p was independent from age, gender, and sidedness. No significant changes in the expression of miR-31-3p were observed when sequential tissue biopsies were tested in long-term or poor responders to anti-EGFR mAbs. miR-31-3p scores were similar when pretreatment biopsies were compared with treatment-naïve archival tissues (often primary colorectal cancer).

CONCLUSIONS

Our study validates the role of miR-31-3p as potential predictive biomarker of selection for anti-EGFR mAbs.

New Insights Into Monogenic Causes of Osteoporosis

Osteoporosis, characterized by deteriorated bone microarchitecture and low bone mineral density, is a chronic skeletal disease with high worldwide prevalence. Osteoporosis related to aging is the most common form and causes significant morbidity and mortality. Rare, monogenic forms of osteoporosis have their onset usually in childhood or young adulthood and have specific phenotypic features and clinical course depending on the underlying cause. The most common form is osteogenesis imperfecta linked to mutations in COL1A1 and COL1A2, the two genes encoding type I collagen. However, in the past years, remarkable advancements in bone research have expanded our understanding of the intricacies behind bone metabolism and identified novel molecular mechanisms contributing to skeletal health and disease. Especially high-throughput sequencing techniques have made family-based studies an efficient way to identify single genes causative of rare monogenic forms of osteoporosis and these have yielded several novel genes that encode proteins partaking in type I collagen modification or regulating bone cell function directly. New forms of monogenic osteoporosis, such as autosomal dominant osteoporosis caused by WNT1 mutations or X-linked osteoporosis due to PLS3 mutations, have revealed previously unidentified bone-regulating proteins and clarified specific roles of bone cells, expanded our understanding of possible inheritance mechanisms and paces of disease progression, and highlighted the potential of monogenic bone diseases to extend beyond the skeletal tissue. The novel gene discoveries have introduced new challenges to the classification and diagnosis of monogenic osteoporosis, but also provided promising new molecular targets for development of pharmacotherapies. In this article we give an overview of the recent discoveries in the area of monogenic forms of osteoporosis, describing the key cellular mechanisms leading to skeletal fragility, the major recent research findings and the essential challenges and avenues in future diagnostics and treatments.

Candidate microRNAs as Biomarkers in Malaria Infection: A Systematic Review

Malaria disease is a public health problem especially in tropical countries, 445.000 of malaria-related deaths have been reported in 2017. MicroRNAs (miRNAs) are small non-coding RNAs with 18-24 nucleotides in length, which have been demonstrated to regulate gene expression of several biological processes. The dysregulation of host immune-related gene expressions during the transcriptional process by microRNA has been extensively reported in malaria parasite invasion of erythrocytes infection. The candidate's miRNAs would be used as potential biomarkers in the future and perspective. A systematic review on miRNAs as candidate clinical biomarkers in malaria infection has been established in this study. Electronic databases (Medline, EMBASE, CINAHL and Cochrane data bases) were screened and articles were included as per established selection criteria. We comprehensively searched to identify publications related to malaria and miRNA. PRISMA guidelines were followed, 262 articles were searched, duplicates and unconnected papers were excluded. Nineteen articles were included in the study. It was found that malaria parasite infected liver or tissue produce tissue-specific miRNAs and release to the blood stream. The association of miRNAs including miR-16, miR-155, miR-150, miR-451 and miR-223 with the dysregulations of immune-related genes expression such as PfEMP-1, IFN-γ, AGO- 1 AGO-2; IL4, CD80, CD86, CD36, ANG-1 and ANG-2 during early, severe and/or cerebral malaria infections indicate the potential use of those miRNAs as biomarkers for malaria infection.

(‑)Epigallocatechin‑3‑gallate attenuates anesthesia‑induced memory deficit in young mice via modulation of nitric oxide expression

(−)Epigallocatechin-3-gallate (EGCG) is a type of polyphenol monomer and is the predominant component of catechin compounds extractable from green tea. Previous studies have demonstrated that EGCG exhibits numerous bioactivities both in vitro and in vivo, including antitumor, antioxidant and anti-inflammatory activities, as well as lowering blood lipid levels and protecting against radiation. The present study aimed to investigate whether administration of EGCG may attenuate anesthesia-induced memory deficit in young mice and to reveal the associated underlying mechanisms. The present study revealed that EGCG administration significantly attenuated memory deficit, oxidative stress and cell apoptosis exhibited by anesthesia-induced mice, as determined by Morris water maze testing and ELISA analysis. Furthermore, the results of ELISA and western blot analysis demonstrated that EGCG administration restored acetylcholinesterase activity and modulated the expression levels of neuronal nitric oxide synthase (nNOS), β-amyloid and amyloid precursor protein in anesthesia-induced mice. The present study also employed L-arginine as an nNOS substrate and 7-nitroindazole as an nNOS inhibitor, which were demonstrated to inhibit or potentiate the effects of EGCG, respectively, on anesthesia-induced memory deficit in mice. Therefore, the present study demonstrated that the administration of EGCG attenuated anesthesia-induced memory deficit in young mice, potentially via the modulation of nitric oxide expression and oxidative stress.

Current understanding and clinical utility of miRNAs regulation of colon cancer stem cells

Cancer stem cells (CSCs) in colorectal tumorigenesis are suggested to be responsible for initiation, development and propagation of colorectal cancer (CRC) and have been extensively characterized by the expression of phenotypic determinants, such as surface or intracellular proteins. The generation of CSCs is likely due to a dysregulation of the signaling pathways that principally control self-renewal and pluripotency in normal intestinal stem cells (ISCs) through different (epi)genetic changes that define cell fate, identity, and phenotype of CSCs. These aspects are currently under intense investigation. In the framework of the oncogenic signaling pathways controlled by microRNAs (miRNAs) during CRC development, a plethora of data suggests that miRNAs can play a key role in several regulatory pathways involving CSCs biology, epithelial-mesenchymal transition (EMT), angiogenesis, metastatization, and pharmacoresistance. This review examines the most relevant evidences about the role of miRNAs in the etiology of CRC, through the regulation of colon CSCs and the principal differences between colorectal CSCs and benign stem cells. In this perspective, the utility of the principal CSCs-related miRNAs changes is explored, emphasizing their use as potential biomarkers to aid in diagnosis, prognosis and predicting response to therapy in CRC patients, but also as promising targets for more effective and personalized anti-CRC treatments.

MicroRNAs in the prognosis and therapy of colorectal cancer: From bench to bedside

MicroRNAs (miRNAs) are small, single-stranded, noncoding RNAs that can post-transcriptionally regulate the expression of various oncogenes and tumor suppressor genes. Dysregulated expression of many miRNAs have been shown to mediate the signaling pathways critical in the multistep carcinogenesis of colorectal cancer (CRC). MiRNAs are stable and protected from RNase-mediated degradation, thereby enabling its detection in biological fluids and archival tissues for biomarker studies. This review focuses on the role and application of miRNAs in the prognosis and therapy of CRC. While stage II CRC is potentially curable by surgical resection, a significant percentage of stage II CRC patients do develop recurrence. MiRNA biomarkers may be used to stratify such high-risk population for adjuvant chemotherapy to provide better prognoses. Growing evidence also suggests that miRNAs are involved in the metastatic process of CRC. Certain of these miRNAs may thus be used as prognostic biomarkers to identify patients more likely to have micro-metastasis, who could be monitored more closely after surgery and/or given more aggressive adjuvant chemotherapy. Intrinsic and acquired resistance to chemotherapy severely hinders successful chemotherapy in CRC treatment. Predictive miRNA biomarkers for response to chemotherapy may identify patients who will benefit the most from a particular regimen and also spare the patients from unnecessary side effects. Selection of patients to receive the new targeted therapy is becoming possible with the use of predictive miRNA biomarkers. Lastly, forced expression of tumor suppressor miRNA or silencing of oncogenic miRNA in tumors by gene therapy can also be adopted to treat CRC alone or in combination with other chemotherapeutic drugs.

Non-Coding RNAs and Resistance to Anticancer Drugs in Gastrointestinal Tumors

Non-coding RNAs are important regulators of gene expression and transcription. It is well established that impaired non-coding RNA expression especially the one of long non-coding RNAs and microRNAs is involved in a number of pathological conditions including cancer. Non-coding RNAs are responsible for the development of resistance to anticancer treatments as they regulate drug resistance-related genes, affect intracellular drug concentrations, induce alternative signaling pathways, alter drug efficiency via blocking cell cycle regulation, and DNA damage response. Furthermore, they can prevent therapeutic-induced cell death and promote epithelial-mesenchymal transition (EMT) and elicit non-cell autonomous mechanisms of resistance. In this review, we summarize the role of non-coding RNAs for different mechanisms resulting in drug resistance (e.g., drug transport, drug metabolism, cell cycle regulation, regulation of apoptotic pathways, cancer stem cells, and EMT) in the context of gastrointestinal cancers.

miR‑3147 serves as an oncomiR in vulvar squamous cell cancer via Smad4 suppression

The incidence of vulvar squamous cell carcinoma (VSCC) has increased annually over the last decade. MicroRNAs (miRNAs/miRs) serve an important role in tumor progression and development. Our previous microarray studies have revealed that miR-3147 was overexpressed in VSCC. However, its function and underlying mechanism in VSCC remain unknown. In the present study, it was confirmed by reverse transcription-quantitative polymerase chain reaction that the expression of miR-3147 was markedly upregulated in VSCC tissues. The increased expression of miR-3147 was positively associated with the depth of invasion. The overexpression of miR-3147 resulted in the promotion of vulvar cancer cell proliferation, migration, invasion, G1/S progression and invasion-associated gene expression. miR-3147 may participate in the process of epithelial-mesenchymal transition and reduce the expressions of downstream target genes in the transforming growth factor-β/Smad signaling pathway in A431 cells. The knockdown of Smad4 by small interfering RNA promoted malignant behaviours in A431 cells. In addition, miR-3147 regulated Smad4 by directly binding to its 3′ untranslated region. In conclusion, the results indicated that miR-3147 may serve an oncogenic role in VSCC by targeting Smad4. miR-3147 may represent a novel potential therapeutic target marker for VSCC.

microRNAs in Cancer Susceptibility

microRNAs (miRNAs) are a small RNA species without protein-coding potential. However, they are key modulators of protein translation. Many studies have linked miRNAs with cancer initiation, progression, diagnosis, and prognosis, and recent studies have also linked them with cancer etiology and susceptibility, especially through single-nucleotide polymorphisms (SNPs). This review discusses some of the recent advances in miRNA-SNP literature-including SNPs in miRNA genes, miRNA target sites, and the processing machinery. In addition, we highlight some emerging areas of interest, including isomiRs and non-3'UTR focused miRNA-binding mechanisms that could provide further novel insight into the relationship between miR-SNPs and cancer. Finally, we note that additional epidemiological and experimental research is needed to close the gap in our understanding of the genotype-phenotype relationship between miRNA-SNPs and cancer.

Regulatory miRNAs in Colorectal Carcinogenesis and Metastasis

Colorectal cancer is one of the most common malignancies and is the second-leading cause of cancer-related death world-wide, which is linked to genetic mutations, epigenetic alterations, and oncogenic signaling activation. MicroRNAs, one of the categories of epigenetics, have been demonstrated significant roles in carcinogenesis and progression through regulating of oncogenic signaling pathways, stem cells, epithelial-mesenchymal transition, and metastasis. This review summarizes the roles of microRNAs in the regulating of Wnt, Ras, TGF-β, and inflammatory signaling pathways, stemness, and epithelial-mesenchymal transition, for carcinogenesis and metastasis in colorectal cancer. Improving our understanding of the mechanisms of regulatory interactions of microRNAs with signaling pathways in colorectal cancer formation and progression will aid in determining the genes responsible for colorectal cancer initiation, progression, metastasis, and recurrence and, finally, in developing personalized approaches for cancer prevention and therapy.

Deregulation of miR-193b affects the growth of colon cancer cells via transforming growth factor-β and regulation of the SMAD3 pathway

MicroRNA-193b (miRNA-193b) is often differentially expressed and is an important regulator of gene expression in colon cancer. The aim of the present study was to determine whether miRNA-193b affects cell growth in colon cancer and to investigate the potential underlying mechanisms. Patients with colorectal cancer (CRC; n=20) and healthy volunteers (n=10) were enrolled from the Department of Gastrointestinal Surgery Center, First Affiliated Hospital of Sun Yat-Sen University (Guangzhou, China). Western blot analysis was used to evaluate the protein expression of SMAD3 and transforming growth factor-β (TGF-β) in the patient samples. It was determined that miRNA-193b expression was markedly elevated in the CRC tissue samples. Furthermore, silencing of miRNA-193bin SW620 CRC cells by specific inhibitors significantly reduced the cell proliferation and induced apoptosis. In addition, the downregulation of miRNA-193b significantly activated the protein expression of SMAD3 and TGF-β, and promoted caspase-3 activity in SW620 cells. The results of the present study suggested that the deregulation of miRNA-193b may affect cell growth in colon cancer via the TGF-β and SMAD3 signaling pathways.

MicroRNAs: New Insight in Modulating Follicular Atresia: A Review

Our understanding of the post-transcriptional mechanisms involved in follicular atresia is limited; however, an important development has been made in understanding the biological regulatory networks responsible for mediating follicular atresia. MicroRNAs have come to be seen as a key regulatory actor in determining cell fate in a wide range of tissues in normal and pathological processes. Profiling studies of miRNAs during follicular atresia and development have identified several putative miRNAs enriched in apoptosis signaling pathways. Subsequent in vitro and/or in vivo studies of granulosa cells have elucidated the functional role of some miRNAs along with their molecular pathways. In particular, the regulatory roles of some miRNAs have been consistently observed during studies of follicular cellular apoptosis. Continued work should gradually lead to better understanding of the role of miRNAs in this field. Ultimately, we expect this understanding will have substantial benefits for fertility management at both the in vivo or/and in vitro levels. The stable nature of miRNA holds remarkable promise in clinical use as a diagnostic tool and in reproductive medicine to solve the ever-increasing fertility problem. In this review, we summarize current knowledge of the involvement of miRNAs in follicular atresia, discuss the challenges for further work and pinpoint areas for future research.

Sequence variation in mature microRNA-608 and benefit from neo-adjuvant treatment in locally advanced rectal cancer patients

Single nucleotide polymorphisms (SNPs) in microRNA genes have been associated with colorectal cancer (CRC) risk, survival and response to treatment. Conflicting results are available on the association between rs4919510, a SNP in mature miR-608 and clinical outcome in CRC. Here, we analyzed the association between rs4919510 and benefit from perioperative treatment in a randomised phase II trial of neoadjuvant Capecitabine and Oxaliplatin (CAPOX) followed by chemo-radiotherapy, surgery and adjuvant CAPOX ± Cetuximab in high-risk locally advanced rectal cancer (LARC). A total of 155/164 (94.5%) patients were assessable. 95 (61.3%) were homozygous for CC, 55 (35.5%) heterozygous (CG) and 5 (3.2%) homozygous for GG. Median follow-up was 64.9 months. In the CAPOX arm the 5-year progression-free survival (PFS) and overall survival (OS) rates were 54.6% and 60.7% for CC and 82.0% and 82.1% for CG/GG, respectively (HR PFS 0.13, 95% CI: 0.12-0.83, P = 0.02; HR OS 0.38, 95% CI: 0.14-1.01, P = 0.05). In the CAPOX-C arm PFS and OS were 73.2 and 82.2%, respectively for CC carriers and 64.6 and 73.1% for CG/GG carriers (HR PFS 1.38, 95% CI: 0.61-3.13, P = 0.44; HR OS 1.34, 95% CI: 0.52-3.48, P = 0.55). An interaction was found between study treatment and rs4919510 genotype for both PFS (P = 0.02) and OS (P = 0.07). This is the first study investigating rs4919510 in LARC. The CC genotype appeared to be associated with worse prognosis compared to the CG/GG genotype in patients treated with chemotherapy and chemo-radiotherapy alone. Addition of Cetuximab to chemotherapy and chemo-radiotherapy in CC carriers appeared to improve clinical outcome.

Microsatellite instability testing and its role in the management of colorectal cancer

Opinion statement: TNM stage remains the key determinant of patient prognosis after surgical resection of colorectal cancer (CRC), and informs treatment decisions. However, there is considerable stage-independent variability in clinical outcome that is likely due to molecular heterogeneity. This variability underscores the need for robust prognostic and predictive biomarkers to guide therapeutic decision-making including the use of adjuvant chemotherapy. Although the majority of CRCs develop via a chromosomal instability pathway, approximately 12-15 % have deficient DNA mismatch repair (dMMR) which is characterized in the tumor by microsatellite instability (MSI). Tumors with the dMMR/MSI develop from a germline mutation in an MMR gene (MLH1, MSH2, MSH6, PMS2), i.e., Lynch syndrome, or more commonly from epigenetic inactivation of MLH1 MMR gene. CRCs with dMMR/MSI status have a distinct phenotype that includes predilection for the proximal colon, poor differentiation, and abundant tumor-infiltrating lymphocytes. Consistent data indicate that these tumors have a better stage-adjusted survival compared to proficient MMR or microsatellite stable (MSS) tumors and may respond differently to 5-fluorouracil-based adjuvant chemotherapy. To increase the identification of dMMR/MSI patients in clinical practice that includes those with Lynch syndrome, it is recommended that all resected CRCs to be analyzed for MMR status. Available data indicate that patients with stage II dMMR CRCs have an excellent prognosis and do not benefit from 5-fluorouracil (FU)-based adjuvant chemotherapy which supports their recommended management by surgery alone. In contrast, the benefit of standard adjuvant chemotherapy with the FOLFOX regiment in stage III dMMR CRC patients awaits further study and therefore, all patients should be treated with standard adjuvant FOLFOX.

The Regulatory Roles of MicroRNAs in Bone Remodeling and Perspectives as Biomarkers in Osteoporosis

MicroRNAs are involved in many cellular and molecular activities and played important roles in many biological and pathological processes, such as tissue formation, cancer development, diabetes, neurodegenerative diseases, and cardiovascular diseases. Recently, it has been reported that microRNAs can modulate the differentiation and activities of osteoblasts and osteoclasts, the key cells that are involved in bone remodeling process. Meanwhile, the results from our and other research groups showed that the expression profiles of microRNAs in the serum and bone tissues are significantly different in postmenopausal women with or without fractures compared to the control. Therefore, it can be postulated that microRNAs might play important roles in bone remodeling and that they are very likely to be involved in the pathological process of postmenopausal osteoporosis. In this review, we will present the updated research on the regulatory roles of microRNAs in osteoblasts and osteoclasts and the expression profiles of microRNAs in osteoporosis and osteoporotic fracture patients. The perspective of serum microRNAs as novel biomarkers in bone loss disorders such as osteoporosis has also been discussed.

MicroRNAs as growth regulators, their function and biomarker status in colorectal cancer

Gene expression is in part regulated by microRNAs (miRNAs). This review summarizes the current knowledge of miRNAs in colorectal cancer (CRC); their role as growth regulators, the mechanisms that regulate the miRNAs themselves and the potential of miRNAs as biomarkers. Although thousands of tissue samples and bodily fluids from CRC patients have been investigated for biomarker potential of miRNAs (>160 papers presented in a comprehensive tables), none single miRNA nor miRNA expression signatures are in clinical use for this disease. More than 500 miRNA-target pairs have been identified in CRC and we discuss how these regulatory nodes interconnect and affect signaling pathways in CRC progression.

Implications of mismatch repair-deficient status on management of early stage colorectal cancer

For primary colorectal cancers (CRCs), tumor stage has been the best predictor of survival after resection and the key determinant of patient management. However, considerable stage-independent variability in clinical outcome is observed that is likely due to molecular heterogeneity. This is particularly important in early stage CRCs where patients can be cured by surgery alone and only a proportion derives benefit from adjuvant chemotherapy. Thus, the identification of molecular prognostic markers to supplement conventional pathologic staging systems has the potential to guide patient management and influence outcomes. CRC is a heterogeneous disease with molecular phenotypes reflecting distinct forms of genetic instability. The chromosomal instability pathway (CIN) is the most common phenotype, accounting for 85% of all sporadic CRCs. Alternatively, the microsatellite instability (MSI) phenotype represents ~15% of all CRCs and is caused by deficient DNA mismatch repair (MMR) as a consequence of germline mutations in MMR genes or, more commonly, epigenetic silencing of the MLH1 gene with frequent mutations in the BRAF oncogene. MSI tumors have distinct phenotypic features and are consistently associated with a better stage-adjusted prognosis compared with microsatellite stable (MSS) tumors. Among non-metastatic CRCs, the difference in prognosis between MSI and MSS tumors is larger for stage II than stage III patients. On the other hand, the predictive impact of MMR status for adjuvant chemotherapy remains a contentious issue in that most studies demonstrate a lack of benefit for 5-fluorouracil (5-FU)-based adjuvant chemotherapy in stage II MSI-H CRCs, whereas it remains unclear in MSI-H stage III tumors. Here, we describe the molecular aspects of the MMR system and discuss the implications of MMR-deficient/MSI-H status in the clinical management of patients with early stage CRC.

MicroRNA regulation of tumorigenesis, cancer progression and interpatient heterogeneity: towards clinical use

In the past two decades, microRNAs have emerged as crucial mediators of organ development and human disease. Here, we discuss their role as drivers or suppressors of the hallmarks of cancer during tumorigenesis and progression, in defining interpatient heterogeneity and the promise of therapeutic application.

Discovery of Potential Therapeutic miRNA Targets in Cardiac Ischemia-Reperfusion Injury

BACKGROUND

A highly efficient approach to select microRNA (miRNA) targets is a key to develop a miRNA-based therapeutic approach to cardiac ischemia-reperfusion (I/R). To reverse the change induced by disease, I/R in this case, is the traditional strategy to develop therapeutic drugs. However, examples show that it will not always serve the purpose. In this study, we demonstrate an additional approach of selecting miRNA targets with therapeutic potential following cues from cardioprotection-induced changes rather than by reversing disease-induced changes in cardiac I/R.

METHODS

Isolated perfused rat hearts subjected to I/R were treated with 50 μmol/L sodium hydrosulfide (NaHS) or 10 nmol/L urocortin 2 (UCN2). Cardiac miRNA regulations were determined by miRNA array. Functional screening of selected miRNA mimics, assessed by WST (2-(4-Iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt) activity and lactate dehydrogenase (LDH) release, was performed in H9c2 and neonatal rat ventricular myocytes (NRVMs) with hypoxia/reoxygenation. RNA-induced silencing complex (RISC)-loaded miRNAs caused by mimic transfection were quantified following argonaute-2 immunoprecipitation. Gene regulations of 1 selected miRNA were determined by quantitative polymerase chain reaction and Western blot.

RESULTS

Treatment with NaHS and UCN2 significantly improved cardiac function and reduced LDH release. The miRNA array indicated a panel of commonly up- and downregulated miRNAs. Among them, 10 upregulated miRNAs with antiapoptotic and antiautophagy potentials were selected for further screening. Mimics of miRNA-221, -150, and -206 were protective in both H9c2 and NRVM. RISC-loaded miRNAs were up by ∼20-fold above. To further prove the feasibility of this approach, miRNA-221 was studied. It reduced I/R-induced caspase 3/7 activity and LC3-II (microtubule-associated protein 1 light chain 3). Measuring genes predicted to regulate apoptosis and autophagy, miRNA-221 mimic decreased Ddit4, TP53inp1, and p27 at both messenger RNA (mRNA) and protein levels, and reduced mRNA of Bak1 and Puma and proteins of Bim and Bmf.

CONCLUSION

Mimicking miRNA changes caused by cardioprotective agents, combined with functional screening, enables investigators to efficiently identify novel miRNAs with therapeutic potential in cardiac I/R.

Prognostic role of the LCS6 KRAS variant in locally advanced rectal cancer: results of the EXPERT-C trial

BACKGROUND

Lethal-7 (let-7) is a tumour suppressor miRNA which acts by down-regulating several oncogenes including KRAS. A single-nucleotide polymorphism (rs61764370, T > G base substitution) in the let-7 complementary site 6 (LCS-6) of KRAS mRNA has been shown to predict prognosis in early-stage colorectal cancer (CRC) and benefit from anti-epidermal growth factor receptor monoclonal antibodies in metastatic CRC.

PATIENTS AND METHODS

We analysed rs61764370 in EXPERT-C, a randomised phase II trial of neoadjuvant CAPOX followed by chemoradiotherapy, surgery and adjuvant CAPOX plus or minus cetuximab in locally advanced rectal cancer. DNA was isolated from formalin-fixed paraffin-embedded tumour tissue and genotyped using a PCR-based commercially available assay. Kaplan-Meier method and Cox regression analysis were used to calculate survival estimates and compare treatment arms.

RESULTS

A total of 155/164 (94.5%) patients were successfully analysed, of whom 123 (79.4%) and 32 (20.6%) had the LCS-6 TT and LCS-6 TG genotype, respectively. Carriers of the G allele were found to have a statistically significantly higher rate of complete response (CR) after neoadjuvant therapy (28.1% versus 10.6%; P = 0.020) and a trend for better 5-year progression-free survival (PFS) [77.4% versus 64.5%: hazard ratio (HR) 0.56; P = 0.152] and overall survival (OS) rates (80.3% versus 71.9%: HR 0.59; P = 0.234). Both CR and survival outcomes were independent of the use of cetuximab. The negative prognostic effect associated with KRAS mutation appeared to be stronger in patients with the LCS-6 TT genotype (HR PFS 1.70, P = 0.078; HR OS 1.79, P = 0.082) compared with those with the LCS-6 TG genotype (HR PFS 1.33, P = 0.713; HR OS 1.01, P = 0.995).

CONCLUSION

This analysis suggests that rs61764370 may be a biomarker of response to neoadjuvant treatment and an indicator of favourable outcome in locally advanced rectal cancer possibly by mitigating the poor prognosis of KRAS mutation. In this setting, however, this polymorphism does not appear to predict cetuximab benefit.

MicroRNAs in Cancer: A Historical Perspective on the Path from Discovery to Therapy

Recent progress in microRNA (miRNA) therapeutics has been strongly dependent on multiple seminal discoveries in the area of miRNA biology during the past two decades. In this review, we focus on the historical discoveries that collectively led to transitioning miRNAs into the clinic. We highlight the pivotal studies that identified the first miRNAs in Caenorhabditis elegans to the more recent reports that have fueled the quest to understand the use of miRNAs as markers for cancer diagnosis and prognosis. In addition, we provide insights as to how unraveling basic miRNA biology has provided a solid foundation for advancing miRNAs, such as miR-34a, therapeutically. We conclude with a brief examination of the current challenges that still need to be addressed to accelerate the path of miRNAs to the clinic: including delivery vehicles, miRNA- and delivery-associated toxicity, dosage, and off target effects.

The let-7g microRNA promotes follicular granulosa cell apoptosis by targeting transforming growth factor-β type 1 receptor

The intronic microRNA let-7g controls cell differentiation and proliferation during angiogenesis and oncogenesis. Here, we demonstrate that let-7g regulates granulosa cell (GC) apoptosis and follicular atresia in the pig ovary. Bioinformatics analyses and luciferase reporter assays showed that transforming growth factor-β type 1 receptor (TGFBR1) is a let-7g target. Overexpression of let-7g induced apoptosis of porcine GCs in vitro and repressed the mRNA and protein levels of TGFBR1, as well as the level of phosphorylated SMAD3 (p-SMAD3) protein. RNA interference-mediated knockdown of TGFBR1 and inhibitor LY2157299-mediated blocking of TGFBR1 significantly increased the rate of apoptosis of GCs and Caspase-3 activity. In addition, treatment of porcine GCs with TGF-β1 reduced the level of let-7g and increased the levels of the TGFBR1 mRNA and proteins significantly. Overall, these results demonstrate that let-7g regulates the apoptosis of GCs in the pig ovary by targeting TGFBR1 and down-regulating the TGF-β signaling pathway.

Comparison of the prevalence of KRAS-LCS6 polymorphism (rs61764370) within different tumour types (colorectal, breast, non-small cell lung cancer and brain tumours). A study of the Czech population

AIMS

A germline SNP (rs61764370) is located in a let-7 complementary site (LCS6) in the 3'UTR of KRAS oncogene, and it was found to alter the binding capability of the mature let-7 microRNA to the KRAS mRNA. The aim of the study was to evaluate the frequency of the KRAS-LCS6 variant allele in different cancer types that included patients with colorectal cancer (CRC), breast cancer (BC), non-small cell lung cancer (NSCLC) and brain tumour patient subgroups from the Czech Republic. The occurrence of this genetic variant was correlated with the presence of selected somatic mutations representing predictive biomarkers in the respective tumours.

METHODS

DNA of tumour tissues was isolated from 428 colorectal cancer samples, 311 non-small cell lung cancer samples, 195 breast cancer samples and 151 samples with brain tumour. Analysis of SNP (rs61764370) was performed by the PCR+RFLP method and direct sequencing. KRAS, BRAF and EGFR mutation status was assessed using real-time PCR. The status of the HER2 gene was assessed using the FISH method.

RESULTS

The KRAS-LCS6 TG genotype has been detected in 16.4% (32/195) of breast cancer cases (in HER2 positive breast cancer 3.3%, in HER2 negative breast cancer 20.1%), in 12.4% (53/428) of CRC cases (KRAS/BRAF wild type CRC in 10.6%, KRAS mutant CRC in 10.1%, BRAF V600E mutant CRC in 18.5%), in 13.2% (41/311) of NSCLC samples, (EGFR mutant NSCLC patients in 8%, EGFR wild type NSCLC in 12.9%), and 17.9% (27/151) of brain tumour cases. The KRAS-LCS6 TG genotype was not significantly different across the studied tumours. In our study, the GG genotype has not been found among the cancer samples.

CONCLUSIONS

Based on the findings, it is concluded that the occurrence of the KRAS-LCS6 TG genotype was statistically significantly different in association with status of the HER2 gene in breast cancer. Furthermore, significant association between the mutation status of analysed somatic variants in genes of the EGFR signalling pathway (KRAS, BRAF, EGFR) and the KRAS-LCS6 genotype in colorectal cancer and NSCLC has not been established.

Manipulating miRNA Expression: A Novel Approach for Colon Cancer Prevention and Chemotherapy

Small non-coding RNA has been implicated in the control of various cellular processes such as proliferation, apoptosis, and differentiation. About 50% of the miRNA genes are positioned in cancer-associated genomic regions. Several studies have shown that miRNA expression is deregulated in cancer and modulating their expression has reversed the cancer phenotype. Therefore, mechanisms to modulate microRNA (miRNA) activity have provided a novel opportunity for cancer prevention and therapy. In addition, a common cause for development of colorectal cancers is environmental and lifestyle factors. One such factor, diet has been shown to modulate miRNA expression in colorectal cancer patients. In this chapter, we will summarize the work demonstrating that miRNAs are novel promising drug targets for cancer chemoprevention and therapy. Improved delivery, increased stability and enhanced regulation of off-target effects will overcome the current challenges of this exciting approach in the field of cancer prevention and therapy.

MicroRNA-mediated regulation of KRAS in cancer

While microRNAs (miRNAs) and the KRAS oncogene are known to be dysregulated in various cancers, little is known about the role of miRNAs in the regulation of KRAS in cancer. Here we review a selection of studies published in 2014 that have contributed to our understanding of the molecular mechanisms of KRAS regulation by miRNAs and the clinical relevance of sequence variants that may interfere with functional miRNA-mediated KRAS regulation.

MicroRNA dysregulation as a prognostic biomarker in colorectal cancer

Colorectal cancer (CRC) is one of the most potentially curable cancers, yet it remains the fourth most common overall cause of cancer death worldwide. The identification of robust molecular prognostic biomarkers can refine the conventional tumor–node–metastasis staging system, avoid understaging of tumor, and help pinpoint patients with early-stage CRC who may benefit from aggressive treatments. Recently, epigenetic studies have provided new molecular evidence to better categorize the CRC subtypes and predict clinical outcomes. In this review, we summarize recent findings concerning the prognostic potential of microRNAs (miRNAs) in CRC. We first discuss the prognostic value of three tissue miRNAs (miR-21-5p, miR-29-3p, miR-148-3p) that have been examined in multiple studies. We also summarize the dysregulation of miRNA processing machinery DICER in CRC and its association with risk for mortality. We also reviewe the potential application of miRNA-associated single-nucleotide polymorphisms as prognostic biomarkers for CRC, especially the miRNA-associated polymorphism in the KRAS gene. Last but not least, we discuss the microsatellite instability-related miRNA candidates. Among all these candidates, miR-21-5p is the most promising prognostic marker, yet further prospective validation studies are required before it can go into clinical usage.