MicroRNAs in tumorigenesis: a primer

Epigenetics of melanoma: implications for immune-based therapies

Malignant melanoma is a complex disease that arises and evolves due to a myriad of genetic and epigenetic events. Among these, the interaction between epigenetic alterations (i.e., histone modifications, DNA methylation, mRNA silencing by miRNAs and nucleosome repositioning) has been recently identified as playing an important role in melanoma development and progression by affecting key cellular pathways such as cell cycle regulation, DNA repair, apoptosis, invasion and immune recognition. Differently to genetic lesions, epigenetic changes are potentially pharmacologically reversible by using epigenetic drugs. Along this line, preclinical and clinical findings indicate that these drugs, given alone or in combination therapies, can efficiently modulate the immunophenotype of melanoma cells. The aim of this review is to provide a comprehensive summary of melanoma epigenetics and the current use of epigenetic drugs in the clinical setting.

MicroRNAs and Recent Insights into Pediatric Ovarian Cancers

Ovarian cancer is the most common pediatric gynecologic malignancy. When diagnosed in children, ovarian cancers present unique challenges that differ dramatically from those faced by adults. Here, we review the spectrum of ovarian cancers found in young women and girls and discuss the biology of these diseases. A number of advances have recently shed significant new understanding on the potential causes of ovarian cancer in this unique population. Particular emphasis is placed on understanding how altered expression of non-coding RNA transcripts known as microRNAs play a key role in the etiology of ovarian germ cell and sex cord-stromal tumors. Emerging transgenic models for these diseases are also reviewed. Lastly, future challenges and opportunities for understanding pediatric ovarian cancers, delineating clinically useful biomarkers, and developing targeted therapies are discussed.

TUMIR: an experimentally supported database of microRNA deregulation in various cancers

BACKGROUND

MicroRNAs were found to play an important role in cancers and several literatures exist to describe the relationship between microRNA and cancer, but the expression pattern was still faintly. There is a need for a comprehensive collection and summary of the interactions under experimental support.

DESCRIPTION

TUMIR (http://www.ncrnalab.com/TUMIR/), a manually extracted database of experimentally supported microRNA-cancer relationship, aims at providing a large, high-quality, validated comprehensive resource of microRNA deregulation in various cancers. The current version includes a systematic literature search to May-1-2012 using PubMed database, contains data extracted from 205 literatures and 1163 entries describing a regulatory interaction between human microRNAs and cancers. Each entry in the database contains the details of microRNA name, the disease name, case number, control number, p value, the experimentally validated targets, sample type, and a brief description of patients' clinic pathologic parameters mentioned in the same paper. The website has several extensive external links to the related websites and any requests can be made by emailing to tumir_pumc@163.com.

CONCLUSION

TUMIR is an open access website and will be an accurate clue for the researchers who are interested in better understanding the relationship between miRNAs and cancer.

A common MicroRNA signature consisting of miR-133a, miR-139-3p, and miR-142-3p clusters bladder carcinoma in situ with normal umbrella cells

miRNAs are small noncoding RNAs with critical roles in a large variety of biological processes such as development and tumorigenesis. miRNA expression profiling has been reported to be a powerful tool to classify tissue samples, including cancers, based on their developmental lineage. In this study, we have profiled the expression of miRNAs in bladder carcinoma in situ (CIS) and distinct cell compartments of the normal bladder, namely umbrella and basal-intermediate urothelial cells, as well as the muscularis propria. We identified several miRNAs differentially expressed between umbrella and basal-intermediate cells (miR-133a, miR-139-3p, miR-142-3p, miR-199b-5p, and miR-221). In situ hybridization confirmed the expression of miR-133a and miR-139-3p in umbrella cells, and miR-142-3p in basal-intermediate cells. Strikingly, miRNA expression levels of CIS most closely resembled the miRNA profile of umbrella cells. Finally, we examined well-established umbrella and basal-intermediate cell immunohistochemical biomarkers in an independent series of CIS samples. Again, this analysis revealed the significant expression of umbrella-specific markers in CIS when compared to non-CIS lesions. Overall, our studies represent a comprehensive and accurate description of the different miRNAs expressed in CIS tumors and three distinct histological areas of the urinary bladder. Notably, this study provides evidence of the possible origin relationship between CIS and normal umbrella cells.

Current status and implications of microRNAs in ovarian cancer diagnosis and therapy

Ovarian cancer is the fifth most common cancer among women and causes more deaths than any other type of female reproductive cancer. Currently, treatment of ovarian cancer is based on the combination of surgery and chemotherapy. While recurrent ovarian cancer responds to additional chemotherapy treatments, the progression-free interval becomes shorter after each cycle, as chemo-resistance increases until the disease becomes incurable. There is, therefore, a strong need for prognostic and predictive markers to help optimize and personalize treatment in order to improve the outcome of ovarian cancer. An increasing number of studies indicate an essential role for microRNAs in ovarian cancer progression and chemo-resistance. MicroRNAs (miRNAs) are small endogenous non-coding RNAs (~22bp) which are frequently dysregulated in cancer. Typically, miRNAs are involved in crucial biological processes, including development, differentiation, apoptosis and proliferation. Two families of miRNAs, miR-200 and let-7, are frequently dysregulated in ovarian cancer and have been associated with poor prognosis. Both have been implicated in the regulation of epithelial-to-mesenchymal transition, a cellular transition associated with tumor aggressiveness, tumor invasion and chemo-resistance. Moreover, miRNAs also have possible implications for improving cancer diagnosis; for example miR-200 family, let-7 family, miR-21 and miR-214 may be useful in diagnostic tests to help detect ovarian cancer at an early stage. Additionally, the use of multiple target O-modified antagomirs (MTG-AMO) to inhibit oncogenic miRNAs and miRNA replacement therapy for tumor suppressor miRNAs are essential tools for miRNA based cancer therapeutics. In this review we describe the current status of the role miRNAs play in ovarian cancer and focus on the possibilities of microRNA-based therapies and the use of microRNAs as diagnostic tools.

Analysis of the miR-34a locus in 62 patients with familial cutaneous melanoma negative for CDKN2A/CDK4 screening

MicroRNAs are small non-coding RNAs, which inhibit expression of specific target genes at the post-transcriptional level and are often misregulated in human cancer. Among them, miR-34a is considered a tumor suppressor with a hypothetical role in melanoma tumorigenesis. In this work, 62 Italian index patients with familial melanoma and negative for CDKN2A/CDK4 screening were investigated for miR-34a germline mutations. Eight novel miR-34a sequence variants were identified at both the heterozygous (c.+259G>A, c.+424G>A, c.+1465C>T, c.+1769C>T, c.+2456T>G, c.+2603C>T, c.+2972T>A, c.+3069T>C) and homozygous (c.+424G>A, c.+1465C>T, c.+1769C>T) states. Molecular screening identified all nucleotide changes in a healthy population of 150 controls and demonstrated that they are common polymorphisms. However, statistically significant differences of allele and genotype frequencies were detected for c.+1465C>T and c.+1769C>T, and borderline values for c.+2456T>G. By stratifying patients by relevant clinical features (presence/absence of multiple primary melanoma, Breslow's thickness, phototype and number of nevi), no significant findings were noted except for an association between the c.+424G>A (heterozygous individual GA) and multiple primary melanoma and phototype III-IV. Our preliminary study suggests that miR-34a, although having a role in late tumorigenesis, does not contribute to the inherited susceptibility to cutaneous melanoma. A function as phenotypic modulator in familial melanoma cannot be excluded.

Oncogenic microRNA-155 down-regulates tumor suppressor CDC73 and promotes oral squamous cell carcinoma cell proliferation: implications for cancer therapeutics

The CDC73 gene is mutationally inactivated in hereditary and sporadic parathyroid tumors. It negatively regulates β-catenin, cyclin D1, and c-MYC. Down-regulation of CDC73 has been reported in breast, renal, and gastric carcinomas. However, the reports regarding the role of CDC73 in oral squamous cell carcinoma (OSCC) are lacking. In this study we show that CDC73 is down-regulated in a majority of OSCC samples. We further show that oncogenic microRNA-155 (miR-155) negatively regulates CDC73 expression. Our experiments show that the dramatic up-regulation of miR-155 is an exclusive mechanism for down-regulation of CDC73 in a panel of human cell lines and a subset of OSCC patient samples in the absence of loss of heterozygosity, mutations, and promoter methylation. Ectopic expression of miR-155 in HEK293 cells dramatically reduced CDC73 levels, enhanced cell viability, and decreased apoptosis. Conversely, the delivery of a miR-155 antagonist (antagomir-155) to KB cells overexpressing miR-155 resulted in increased CDC73 levels, decreased cell viability, increased apoptosis, and marked regression of xenografts in nude mice. Cotransfection of miR-155 with CDC73 in HEK293 cells abrogated its pro-oncogenic effect. Reduced cell proliferation and increased apoptosis of KB cells were dependent on the presence or absence of the 3'-UTR in CDC73. In summary, knockdown of CDC73 expression due to overexpression of miR-155 not only adds a novelty to the list of mechanisms responsible for its down-regulation in different tumors, but the restoration of CDC73 levels by the use of antagomir-155 may also have an important role in therapeutic intervention of cancers, including OSCC.

Expression of miRNAs and PTEN in endometrial specimens ranging from histologically normal to hyperplasia and endometrial adenocarcinoma

We investigated the relationship between frequently deregulated microRNAs (miRNAs) and enodometrial pathology in an attempt to find the most dependable miRNA or combination of miRNAs to identify normal, hyperplastic and malignant endometrial tissues. We also investigated the association between those miRNAs and PTEN status. We measured the expression of six miRNAs (miR-21, 182, 183, 200a, 200c and 205) in 75 formalin-fixed, paraffin-embedded normal, hyperplastic, and malignant endometrial tissue blocks using Taqman-based real-time PCR assays. PTEN loss of expression was assessed in the same endometrial tissues by immunohistochemistry. Expression of five miRNAs (miR-182, 183, 200a, 200c and 205) was significantly higher in endometrial carcinoma (CA) when compared with complex atypical hyperplasia (CAH), simple hyperplasia (SH) and normal endometrial tissue (P<0.05, respectively). Considering the likelihood ratio and number of parameters, the composite panel of six miRNAs was the best marker, revealing a sensitivity of 91% and a specificity of 94% in differentiating endometrial CA from endometrial hyperplasia or normal endometrium while the individual miRNAs exhibited 64-77% sensitivity and 66-91% specificity. Interestingly, in distinguishing endometrial CA from CAH, the composite panel of four miRNAs (miR-182, 183, 200a, 200c) was the best marker, producing 95% sensitivity and 91% specificity. The percentage of PTEN loss was significantly higher in endometrial CA compared with SH (68% vs 24%, P<0.05), and it was also higher in CAH compared with SH (71% vs 24%, P<005). Aberrant expression of miRNAs and loss of PTEN expression are common in endometrial hyperplasia and CA. They might serve to increase the diagnostic reproducibility and improve discrimination, especially, between CAH and CA by miRNA expression profiles and between simple and complex hyperplasia through PTEN expression patterns. Those expression profiles of biomarkers also might be used to predict the potential for progression from endometrial hyperplasia to invasive CA.

miR-499 rs3746444 polymorphism is associated with cancer development among Asians and related to breast cancer susceptibility

To derive a more precise estimation of the relationship between miR-499 rs3746444 polymorphism (A>G) and cancer risk, a meta-analysis was performed. A total of 9 studies including 6,077 cases and 7,199 controls were involved in this meta-analysis. Overall, no significantly elevated cancer risk was associated with miR-499 G allele when all studies were pooled into the meta-analysis (AG vs. AA: OR = 1.14, 95 % CI = 0.98-1.32; GG vs. AA: OR = 1.12, 95 % CI = 0.95-1.33; dominant model: OR = 1.13, 95 % CI = 0.99-1.29; recessive model: OR = 1.05, 95 % CI = 0.83-1.33). In the subgroup analysis by ethnicity, significantly increased risk was only found for Asians (dominant model: OR = 1.22, 95 % CI = 1.02-1.46). When stratified by study design, no statistically significantly elevated risks were found in hospital-based studies or population-based studies. In the subgroup analysis by cancer type, significant cancer risk change was only found for breast cancer when miR-499 G allele was included (dominant model: OR = 1.13, 95 % CI = 1.01-1.26). In conclusion, this meta-analysis suggests that the miR-499 rs3746444 polymorphism (A>G) is a low-penetrant risk factor for cancer development among Asians and may contribute to breast cancer susceptibility.

MicroRNAs and metastasis-related gene expression in Egyptian breast cancer patients

AIM AND BACKGROUND

MicroRNAs (miRNAs) are a class of naturally occurring small noncoding RNAs that regulate gene expression, cell growth, differentiation and apoptosis by targeting mRNAs for translational repression or cleavage. The present study was conducted to study miRNAs in Egyptian breast cancer (BC) and their relation to metastasis, tumor invasion and apoptosis in addition to their association with the ER and PR statuses.

METHODS

Real Time RT-PCR was performed to identify the miRNA expression level of eight miRNAs and eight metastatic-related genes in 40 breast cancer samples and their adjacent non-neoplastic tissues. The expression levels of each miRNA relative to U6 RNA were determined. Also, miRNA expression profiles of the BC and their corresponding ANT were evaluated.

RESULTS

The BC patients showed an up-regulation in miRNAs (mir-155, mir-10, mir-21 and mir-373) with an upregulation in MMP2, MMp9 and VEGF genes. We found down regulation in mir-17p, mir-126, mir-335, mir-30b and also TIMP3, TMP1 and PDCD4 genes in the cancer tissue compared to the adjacent non-neoplastic tissues. Mir -10b, mir -21, mir-155 and mir373 and the metastatic genes MMP2, MMP9 and VEGF were significantly associated with an increase in tumor size (P<0.05). No significant difference was observed between any of the studied miRNAs regarding lymph node metastasis. Mir-21 was significantly over-expressed in ER-/PR- cases.

CONCLUSION

Specific miRNAs (mir-10, mir-21, mir-155, mir-373, mir-30b, mir-126, mir-17p, mir-335) are associated with tumor metastasis and other clinical characteristics for BC, facilitating identification of individuals who are at risk.

MicroRNA expression in ovarian carcinoma and its correlation with clinicopathological features

Background

MicroRNA (miRNA) expression is known to be deregulated in ovarian carcinomas. However, limited data is available about the miRNA expression pattern for the benign or borderline ovarian tumors as well as differential miRNA expression pattern associated with histological types, grades or clinical stages in ovarian carcinomas. We defined patterns of microRNA expression in tissues from normal, benign, borderline, and malignant ovarian tumors and explored the relationship between frequently deregulated miRNAs and clinicopathologic findings, response to therapy, survival, and association with Her-2/neu status in ovarian carcinomas.

Methods

We measured the expression of nine miRNAs (miR-181d, miR-30a-3p, miR-30c, miR-30d, miR-30e-3p, miR-368, miR-370, miR-493-5p, miR-532-5p) in 171 formalin-fixed, paraffin-embedded ovarian tissue blocks as well as six normal human ovarian surface epithelial (HOSE) cell lines using Taqman-based real-time PCR assays. Her-2/neu overexpression was assessed in ovarian carcinomas (n = 109 cases) by immunohistochemistry analysis.

Results

Expression of four miRNAs (miR-30c, miR-30d, miR-30e-3p, miR-370) was significantly different between carcinomas and benign ovarian tissues as well as between carcinoma and borderline tissues. An additional three miRNAs (miR-181d, miR-30a-3p, miR-532-5p) were significantly different between borderline and carcinoma tissues. Expression of miR-532-5p was significantly lower in borderline than in benign tissues. Among ovarian carcinomas, expression of four miRNAs (miR-30a-3p, miR-30c, miR-30d, miR-30e-3p) was lowest in mucinous and highest in clear cell samples. Expression of miR-30a-3p was higher in well-differentiated compared to poorly differentiated tumors (P = 0.02), and expression of miR-370 was higher in stage I/II compared to stage III/IV samples (P = 0.03). In multivariate analyses, higher expression of miR-181d, miR-30c, miR-30d, and miR-30e-3p was associated with significantly better disease-free or overall survival. Finally, lower expression of miR-30c, miR-30d, miR-30e-3p and miR-532-5p was significantly associated with overexpression of Her-2/neu.

Conclusions

Aberrant expression of miRNAs is common in ovarian tumor suggesting involvement of miRNA in ovarian tumorigenesis. They are associated with histology, clinical stage, survival and oncogene expression in ovarian carcinoma.

Insights into the potential use of microRNAs as biomarker in cancer

MicroRNAs (miRs) are small non-coding RNAs, which regulate gene expression profiles of several genes. Consequently, miRs control and regulate several vital cellular processes like proliferation, apoptosis, differentiation, etc. Not surprisingly, altered expression of miRs has been linked to cancer development and progression. Recent studies have shown that sufficiently stable miRs can be isolated from the serum and other body fluids of cancer patients. The distinct miR profiles in the cell free circulating fluids of cancer patients have a potential to become a new class of biomarkers to detect and prognosticate cancers. In this review, we first briefly address the biogenesis of miRs and their role in gene regulation. Subsequently, we highlighted the role of miRs in pathogenesis of diseases with an emphasis on cancers. Finally, since, miRs have been shown to be promising circulating biomarkers for cancer detection, we 1) summarize the work done to date and 2) highlight the most significant advances resulting from these studies.

Expression of miR-155 in primary hepatocellular carcinoma and its effect on tumor cell proliferation

AIM: To detect the expression of microRNA 155 (miR-155) in hepatocellular carcinoma and to analyze its influence on tumor cell proliferation and apoptosis.

METHODS: The expression of miR-155 in 42 cases of primary liver cancer and matched tumor-adjacent normal tissue was detected by quantitative PCR. The expression of miR-155 in hepatocellular carcinoma cell lines HepG2 and SMMC7721 was inhibited using a miR-155-specific antisense oligonucleotide (ASO-miR-155), and cell proliferation and early apoptosis were then determined by MTT assay and flow cytometry, respectively.

RESULTS: The positive rate of miR-155 expression was significantly higher in hepatocellular carcinoma (52%) than in tumor-adjacent tissue (P < 0.05). After ASO-miR-155 was transfected into HepG2 and SMMC7721 cells using Lipofectamine, the expression of miR-155 was significantly reduced. MiR155 knockdown significantly inhibited growth and promoted early apoptosis of HepG2 and SMMC7721 cells.

CONCLUSION: MiR-155 is overexpressed in hepatocellular carcinoma. Inhibition of miR-155 expression could inhibit growth and induce early apoptosis of hepatocellular carcinoma cells. MiR-155 may become a new target for the treatment of liver cancer.

MicroRNA expression aids the preoperative diagnosis of pancreatic ductal adenocarcinoma

OBJECTIVES

This study aimed to evaluate microRNA (miRNA) expression in pancreatic resection specimens and fine needle aspiration biopsies and determine which, if any, miRNAs aid the distinction between benign and malignant pancreatic tumors in limited cytology material.

METHODS

Resection specimens containing adenocarcinoma (n = 17), intraductal papillary mucinous neoplasms (n = 11), and nonneoplastic tissues (n = 15) were evaluated for miR-21, miR-221, miR-100, miR-155, and miR-181b expression by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), and a subset of carcinomas and intraductal papillary mucinous neoplasms was analyzed with miRNA microarrays. Cellblocks containing carcinoma (n = 26) or benign pancreatic lesions (n = 11) from fine needle aspiration biopsies were subjected to qRT-PCR for miR-21, miR-221, miR-181b, miR-196a, and miR-217.

RESULTS

Carcinomas showed higher expression of miR-21, miR-221, miR-155, miR-100, and miR-181b than benign lesions by qRT-PCR, and overexpression of miR-21, miR-221, and miR-181b was confirmed by microarray analysis. Cellblocks containing carcinoma showed higher expression of miR-21, miR-221, and miR-196a than those from benign lesions (P < 0.001, P = 0.009, and P < 0.001, respectively).

CONCLUSIONS

Pancreatic ductal adenocarcinomas show differential expression of miRNAs compared to benign pancreatic lesions. A select panel of miRNAs aids the distinction between pancreatic lesions in cytology specimens.

NEDD9, a novel target of miR-145, increases the invasiveness of glioblastoma

miR-145 is an important repressor of pluripotency in embryonic stem cells and a tumor suppressor in different cancers. Here, we found that miR-145 is strongly down-regulated in glioblastoma (GB) specimens and corresponding glioblastomaneurospheres (GB-NS, containing GB stem-like cells) compared to normal brain (NB) and to low-grade gliomas (LGG). We observed a direct correlation between miR-145 expression and the progression-free survival (PFS) in LGG patients and overall survival (OS) in GB patients. Using microarray analysis, we identified relevant differences in gene expression profiles between GB-NS over-expressing miR-145 (miRover-NS) and GB-NS Empty (Empty-NS). We focused our attention on HEF1/Cas-L/NEDD9, a scaffold protein involved in invasion in several types of cancer. We confirmed a significant down-regulation of NEDD9 in miRover-NS and we found a higher expression in GB and GB-NS compared to NB. Approximately 50% of LGG patients expressed higher levels of NEDD9 than NB, and the PFS of such patients was shorter than in patients expressing lower levels of NEDD9. We observed that intracranial injection of GB-NS over-expressing miR-145 delays significantly tumor development :deriving tumors showed a significant down-regulation of NEDD9. In addition, we demonstrated a significant inhibition of invasion in silencing experiments with GB-NS shNEDD9 (shNEDD9), and an up-regulation of miR-145 in shNEDD9, suggesting a doublenegative feedback loop between miR-145 and NEDD9. Our results demonstrate the critical role of miR-145 and NEDD9 in regulating glioblastoma invasion and suggest a potential role of NEDD9 as a biomarker for glioma progression.

Chemoresistance in prostate cancer cells is regulated by miRNAs and Hedgehog pathway

Many prostate cancers relapse due to the generation of chemoresistance rendering first-line treatment drugs like paclitaxel (PTX) ineffective. The present study aims to determine the role of miRNAs and Hedgehog (Hh) pathway in chemoresistant prostate cancer and to evaluate the combination therapy using Hh inhibitor cyclopamine (CYA). Studies were conducted on PTX resistant DU145-TXR and PC3-TXR cell lines and clinical prostate tissues. Drug sensitivity and apoptosis assays showed significantly improved cytotoxicity with combination of PTX and CYA. To distinguish the presence of cancer stem cell like side populations (SP), Hoechst 33342 flow cytometry method was used. PTX resistant DU145 and PC3 cells, as well as human prostate cancer tissue possess a distinct SP fraction. Nearly 75% of the SP cells are in the G0/G1 phase compared to 62% for non-SP cells and have higher expression of stem cell markers as well. SP cell fraction was increased following PTX monotherapy and treatment with CYA or CYA plus PTX effectively reduced their numbers suggesting the effectiveness of combination therapy. SP fraction cells were allowed to differentiate and reanalyzed by Hoechst staining and gene expression analysis. Post differentiation, SP cells constitute 15.8% of total viable cells which decreases to 0.6% on treatment with CYA. The expression levels of P-gp efflux protein were also significantly decreased on treatment with PTX and CYA combination. MicroRNA profiling of DU145-TXR and PC3-TXR cells and prostate cancer tissue from the patients showed decreased expression of tumor suppressor miRNAs such as miR34a and miR200c. Treatment with PTX and CYA combination restored the expression of miR200c and 34a, confirming their role in modulating chemoresistance. We have shown that supplementing mitotic stabilizer drugs such as PTX with Hh-inhibitor CYA can reverse PTX chemoresistance and eliminate SP fraction in androgen independent, metastatic prostate cancer cell lines.

MiRNAs and LincRNAs: Could they be considered as biomarkers in colorectal cancer?

Recent advances in the field of RNA research have provided compelling evidence implicating microRNA (miRNA) and long non-coding RNA molecules in many diverse and substantial biological processes, including transcriptional and post-transcriptional regulation of gene expression, genomic imprinting, and modulation of protein activity. Thus, studies of non-coding RNA (ncRNA) may contribute to the discovery of possible biomarkers in human cancers. Considering that the response to chemotherapy can differ amongst individuals, researchers have begun to isolate and identify the genes responsible. Identification of targets of this ncRNA associated with cancer can suggest that networks of these linked to oncogenes or tumor suppressors play pivotal roles in cancer development. Moreover, these ncRNA are attractive drug targets since they may be differentially expressed in malignant versus normal cells and regulate expression of critical proteins in the cell. This review focuses on ncRNAs that are differently expressed in malignant tissue, and discusses some of challenges derived from their use as potential biomarkers of tumor properties.

Ovarian cancer: opportunity for targeted therapy

Ovarian cancer is a common cause of cancer mortality in women with limited treatment effectiveness in advanced stages. The limitation to treatment is largely the result of high rates of cancer recurrence despite chemotherapy and eventual resistance to existing chemotherapeutic agents. The objective of this paper is to review current concepts of ovarian carcinogenesis. We will review existing hypotheses of tumor origin from ovarian epithelial cells, Fallopian tube, and endometrium. We will also review the molecular pathogenesis of ovarian cancer which results in two specific pathways of carcinogenesis: (1) type I low-grade tumor and (2) type II high-grade tumor. Improved understanding of the molecular basis of ovarian carcinogenesis has opened new opportunities for targeted therapy. This paper will also review these potential therapeutic targets and will explore new agents that are currently being investigated.

Association between miR-224 expression and cell proliferation and apoptosis in pancreatic cancer

AIM: To investigate the expression of miR-224 in pancreatic carcinoma and to evaluate the role of miR-224 in pancreatic cancer cell proliferation and apoptosis.

METHODS: The expression of miR-224 in 40 pancreatic carcinoma tissue specimens and matched tumor-adjacent nontumorous tissue specimens was detected by real-time fluorescence PCR. After using the antisense technology to decrease the expression of miR-224 in pancreatic cancer cells (Aspc-1 and Bxpc-3), MTT assay and flow cytometry were performed to investigate the impact of miR-224 down-regulation on cell proliferation, cell cycle progression and apoptosis.

RESULTS: MiR-224 was found to be overexpressed in 43% of pancreatic carcinoma cases (P < 0.05). After antisense microRNA-mediated knockdown of miR-224, the proliferation of Aspc-1 and Bxpc-3 cells was significantly inhibited. Aspc-1 and Bxpc-3 cells were mainly arrested in G₀/G₁ phase, and the percentage of cells in S and G2/M phases decreased. In addition, miR-224 knockdown in Aspc-1 and Bxpc-3 cells resulted in an increase in early apoptosis.

CONCLUSION: MiR-224 is overexpressed in human pancreatic carcinoma. Inhibition of miR-224 expression can not only effectively suppress growth but also induce cell apoptosis of Aspc-1 and Bxpc-3 cells. MiR-224 may serve as a new molecular target for the treatment of pancreatic carcinoma.

MicroRNA cloning and sequencing in osteosarcoma cell lines: differential role of miR-93

BACKGROUND

Studies show that abnormalities in non-coding genes can contribute to carcinogenesis; microRNA levels may modulate cancer growth and metastatic diffusion.

METHOD

MicroRNA libraries were built and sequenced from two osteosarcoma cell lines (MG-63 and 143B), which differ in proliferation and transmigration. By cloning and transfection, miR-93, expressed in both cell lines, was then investigated for its involvement in osteosarcoma progression.

RESULTS

Six of the 19 miRNA identified were expressed in both cell lines with higher expression levels of miR-93 in 143B and in primary osteosarcoma cultures compared to normal osteoblasts. Interestingly, levels of miR-93 were significantly higher in metastases from osteosarcoma than in paired primary tumours. When 143B and MG-63 were transfected with miR-93, clones appeared to respond differently to microRNA overexpression. Ectopic expression of miR-93 more significantly increased cell proliferation and invasivity in 143B than in MG-63 clones. Furthermore, increased mRNA and protein levels of E2F1, one of the potential miR-93 targets, were seen in osteosarcoma cellular clones and its involvement in 143B cell proliferation was confirmed by E2F1 silencing.

CONCLUSION

Although further studies are needed to evaluate miRNA involvement in osteosarcoma progression, miR-93 overexpression seems to play an important role in osteosarcoma cell growth and invasion.

Invasion front-specific expression and prognostic significance of microRNA in colorectal liver metastases

The tumor edge of colorectal cancer and its adjacent peritumoral tissue is characterized by an invasion front-specific expression of genes that contribute to angiogenesis or epithelial-to-mesenchymal transition. Dysregulation of these genes has a strong impact on the invasion behavior of tumor cells. However, the invasion front-specific expression of microRNA (miRNA) still remains unclear. Therefore, the aim of the present study was to investigate miRNA expression patterns at the invasion front of colorectal liver metastases. Laser microdissection of colorectal liver metastases was performed to obtain separate tissue compartments from the tumor center, tumor invasion front, liver invasion front and pure liver parenchyma. Microarray expression analysis revealed 23 miRNA downregulated in samples from the tumor invasion front with respect to the same miRNA in the liver, the liver invasion front or the tumor center. By comparing samples from the liver invasion front with samples from pure liver parenchyma, the tumor invasion front and the tumor center, 13 miRNA were downregulated. By quantitative RT-PCR, we validated the liver invasion front-specific downregulation of miR-19b, miR-194, let-7b and miR-1275 and the tumor invasion front-specific downregulation of miR-143, miR- 145, let-7b and miR-638. Univariate analysis demonstrated that enhanced expression of miR-19b and miR-194 at the liver invasion front, and decreased expression of let-7 at the tumor invasion front, is an adverse prognostic marker of tumor recurrence and overall survival. In conclusion, the present study suggests that invasion front-specific downregulation of miRNA in colorectal liver metastases plays a pivotal role in tumor progression.

Regulation and function of miRNA-21 in health and disease

The small regulatory RNA microRNA-21 (miR-21) plays a crucial role in a plethora of biological functions and diseases including development, cancer, cardiovascular diseases and inflammation. The gene coding for pri-miR-21 (primary transcript containing miR-21) is located within the intronic region of the TMEM49 gene. Despite pri-miR-21 and TMEM49 are overlapping genes in the same direction of transcription, pri-miR-21 is independently transcribed by its own promoter regions and terminated with its own poly(A) tail. After transcription, primiR- 21 is finally processed into mature miR-21. Expression of miR-21 has been found to be deregulated in almost all types of cancers and therefore was classified as an oncomiR. During recent years, additional roles of miR-21 in cardiovascular and pulmonary diseases, including cardiac and pulmonary fibrosis as well as myocardial infarction have been described. MiR-21 additionally regulates various immunological and developmental processes. Due to the critical functions of its target proteins in various signaling pathways, miR-21 has become an attractive target for genetic and pharmacological modulation in various disease conditions.

Glycogen synthase kinase 3 beta (GSK3β) phosphorylates the RNAase III enzyme Drosha at S300 and S302

The canonical microRNA (miRNA) pathway commences with the enzymatic cleavage of the primary gene transcript (pri-miRNA) by the RNAase III enzyme Drosha in the nucleus into shorter pre-miRNA species that are subsequently exported to the cytoplasm for further processing into shorter, mature miRNA molecules. Using a series of reporter constructs, we have previously demonstrated that phosphorylation of Drosha at Ser 300 and 302 was required for its nuclear localization. Here, we identify GSK3β as the culprit kinase. We demonstrate that Drosha is unable to selectively localize to the nucleus in cells deficient in GSK3β. These findings expand the substrate base of GSK3β to include a central component of the miRNA biogenesis pathway.

The biological and therapeutic relevance of mRNA translation in cancer

Protein synthesis is a tightly regulated process that enables post-transcriptional control of gene expression. Dysregulation of this process is associated with the development and progression of cancers because components of the translational machinery function at the point of convergence of aberrant cell signaling pathways. Drugs designed to inhibit mRNA translation are currently in preclinical and early clinical development, and are likely to provide effective anticancer strategies in the future. In this Review, we summarize the main components of translation and describe how alterations in these proteins and their principle upstream signaling pathways can impact on cancer. The first inhibitors of translation, drugs designed to target eIF4E, have been trialed in hematologic malignancies, while antisense oligonucleotides against eIF4E are also due to enter clinical trials. Here, we discuss the mode of action of drugs designed to inhibit mRNA translation and other promising therapies that are in preclinical development with the aim of becoming anticancer agents.

HUVEC respond to radiation by inducing the expression of pro-angiogenic microRNAs

MicroRNAs (miRNAs) represent a class of small non-coding RNAs that control gene expression by targeting mRNAs and triggering either repression of translation or RNA degradation. They have been shown to be involved in a variety of biological processes such as development, differentiation and cell cycle control, but little is known about their involvement in the response to irradiation. We showed here that in human umbilical vein endothelial cells (HUVEC) some miRNAs previously shown to have a crucial role in vascular biology are transiently modulated in response to a clinically relevant dose of ionizing radiation. In particular we identified an early transcriptional induction of several members of the microRNA cluster 17-92 and other microRNAs already known to be related to angiogenesis. At the same time we observed a peculiar behavior of the miR-221/222 cluster, suggesting an important role of these microRNAs in HUVEC homeostasis. We observed an increased efficiency in the formation of capillary-like structures in irradiated HUVEC. These results could lead to a new interpretation of the effect of ionizing radiation on endothelial cells and on the response of tumor endothelial bed cells to radiotherapy.

MicroRNA Expression in Selected Carcinomas of the Gastrointestinal Tract

MicroRNAs (miRNAs) comprise a recently discovered class of small, 18-25 nucleotide, noncoding RNA sequences that regulate gene expression at the posttranscriptional level by binding to and inhibiting the translation of target messenger RNAs (mRNAs). Characteristic patterns of miRNA expression have been described in several malignancies of the gastrointestinal tract, and numerous investigators have demonstrated interactions between specific miRNA species and target oncogenes or tumor-suppressor genes. It is clear that miRNAs play an important role in regulating expression of a number of genes involved in gastrointestinal carcinogenesis, and, thus, these molecules may represent either diagnostic markers of, or therapeutic targets for, some types of malignancy. This paper summarizes the literature regarding miRNA expression in carcinomas of the colon, pancreas, and liver and discusses some of the mechanisms by which these molecules participate in gastrointestinal oncogenesis.

Proteomic identification of microRNA-122a target proteins in hepatocellular carcinoma

MicroRNA-122a (miR-122a) is a liver-specific miRNA that is frequently downregulated in hepatocellular carcinoma (HCC). The exact functional role of miR-122a and its target in HCC remain largely unknown. We developed a lentiviral vector for the expression of pre-miR-122a (Lenti-miR-122a). Lenti-miR-122a inhibited HCC cell growth and induced apoptosis in vitro. We employed proteomic profiling to identify the target proteins of miR-122a. In total, ten proteins with differential expression in HCC cells infected with Lenti-miR-122a were identified. Amongst them, downregulation of peroxiredoxin 2 (PRDXII) by miR-122a was validated by Western blotting. Using bioinformatics analysis, predictable target sites of miR-122a were identified in the 5'-UTR of PRDXII mRNA. Luciferase reporter assay confirmed the regulation of miR-122a on 5'-UTR of PRDXII. In conclusion, PRDXII was identified to be the new target of miR-122a.

Putative tumor suppressor miR-145 inhibits colon cancer cell growth by targeting oncogene Friend leukemia virus integration 1 gene

BACKGROUND

Tumor suppressor microRNA miR-145 is commonly down-regulated in colon carcinoma tissues, but its specific role in tumors remains unknown.

METHODS

In this study, the authors identified the Friend leukemia virus integration 1 gene (FLI1) as a novel target of miR-145. FLI1 is involved in t(11;22)(q24:q12) reciprocal chromosomal translocation in Ewing sarcoma, and its expression appears to be associated with biologically more aggressive tumors.

RESULTS

The authors demonstrated that miR-145 targets a putative microRNA regulatory element in the 3'-untranslated region (UTR) of FLI1, and its abundance is reversely associated with FLI1 expression in colon cancer tissues and cell lines. By using a luciferase/FLI1 3'-UTR reporter system, they found that miR-145 down-regulated the reporter activity, and this down-regulation was reversed by anti-miR-145. Mutation of the miR-145 microRNA regulatory element sequence in the FLI1 3'-UTR abolished the activity of miR-145. miR-145 decreased FLI1 protein but not FLI1 mRNA, suggesting a mechanism of translational regulation. Furthermore, the authors demonstrated that miR-145 inhibited cell proliferation and sensitized LS174T cells to 5-fluorouracil-induced apoptosis.

CONCLUSIONS

Taken together, these results suggest that miR-145 functions as a tumor suppressor by down-regulating oncogenic FLI1 in colon cancer.

Treatment of liver metastases in patients with neuroendocrine tumors: a comprehensive review

Patients diagnosed with Neuroendocrine Tumors (NET) often are also diagnosed with Neuroendocrine Liver Metastases (NLM) during the course of their disease. NLM can cause significant morbidity and mortality, oftentimes much more than compared to patients with NET. Treatment options have been limited in the past, focusing on surgical resections, for which only a minority of patients are candidates. However, developments of new treatment modalities have progressed rapidly and patients with NLM now have significantly more options, including surgical-directed therapies; liver-directed therapies; and nonsurgical, non-liver-directed therapies. This review provides information about the roles of hepatic resection, orthotopic liver resection, radiofrequency ablation, hepatic artery embolization and hepatic artery chemoembolization, hepatic artery radioembolization and selective internal radiation therapy, peptide receptor radionuclide therapy, systemic chemotherapy, biotherapies including somatostatin analogs and interferon-α, vascular endothelial growth factor and mTOR targets, and microRNA-regulated pathways. Given these new options, the clinician can tailor therapy specific to the patient diagnosed with NLM, thereby giving the patient the best possible chance of prolonged survival.

MicroRNA binding site polymorphisms as biomarkers of cancer risk

MicroRNAs (miRNAs) are well established as global gene regulators and thus, slight alterations in miRNA levels as well as their ability to regulate their targets may cause important cellular changes leading to cancer risk. 3´ untranslated region (UTR) miRNA binding site single nucleotide polymorphisms (SNPs) have added another layer of possible genetic variation involved in the complex process of oncogenesis. Identifying these key genetically inherited effectors of miRNA functioning has improved our understanding of the complexity of disease. Interest in the field has grown rapidly in only the last 5 years, with several studies reporting on the role of 3´UTR binding site SNPs as genetic markers of increased cancer susceptibility, as well as biomarkers of cancer type, outcome and response to therapy. Currently, there are numerous known miRNA binding site SNPs associated with multiple cancer subtypes.

To polyadenylate or to deadenylate: that is the question

mRNA polyadenylation and deadenylation are important processes that allow rapid regulation of gene expression in response to different cellular conditions. Almost all eukaryotic mRNA precursors undergo a co-transcriptional cleavage followed by polyadenylation at the 3' end. After the signals are selected, polyadenylation occurs to full extent, suggesting that this first round of polyadenylation is a default modification for most mRNAs. However, the length of these poly(A) tails changes by the activation of deadenylation, which might regulate gene expression by affecting mRNA stability, mRNA transport, or translation initiation. The mechanisms behind deadenylation activation are highly regulated and associated with cellular conditions such as development, mRNA surveillance, DNA damage response, cell differentiation and cancer. After deadenylation, depending on the cellular response, some mRNAs might undergo an extension of the poly(A) tail or degradation. The polyadenylation/deadenylation machinery itself, miRNAs, or RNA binding factors are involved in the regulation of polyadenylation/deadenylation. Here, we review the mechanistic connections between polyadenylation and deadenylation and how the two processes are regulated in different cellular conditions. It is our conviction that further studies of the interplay between polyadenylation and deadenylation will provide critical information required for a mechanistic understanding of several diseases, including cancer development.

Genetic variation in microRNA genes and prostate cancer risk in North Indian population

Recent evidence indicates the involvement of microRNAs (miRNAs), in cell growth control, differentiation, and apoptosis, thus playing a role in tumorigenesis. Single-nucleotide polymorphisms (SNPs) located at miRNA-binding sites (miRNA-binding SNPs) are likely to affect the expression of the miRNA target and may contribute to the susceptibility of humans to common diseases. We genotyped SNPs hsa-mir196a2 (rs11614913), hsa-mir146a (rs2910164), and hsa-mir499 (rs3746444) in a case-control study including 159 prostate cancer patients and 230 matched controls. Patients with heterozygous genotype in hsa-mir196a2 and hsa-mir499, showed significant risk for developing prostate cancer (P = 0.01; OR = 1.70 and P ≤ 0.001; OR = 2.27, respectively). Similarly, the variant allele carrier was also associated with prostate cancer, (P = 0.01; OR = 1.66 and P ≤ 0.001; OR = 1.97, respectively) whereas, hsa-mir146a revealed no association in prostate cancer. None of the miRNA polymorphisms were associated with Gleason grade and bone metastasis. This is the first study on Indian population substantially presenting that individual as well as combined genotypes of miRNA-related variants may be used to predict the risk of prostate cancer and may be useful for identifying patients at high risk.

Challenge and promise: the role of miRNA for pathogenesis and progression of malignant melanoma

microRNAs are endogenous noncoding RNAs that are implicated in gene regulation. More recently, miRNAs have been shown to play a pivotal role in multiple cellular processes that interfere with tumorigenesis. Here we summarize the essential role of microRNAs for human cancer with special focus on malignant melanoma and the promising perspectives for cancer therapies.

MicroRNA expression in ACTH-producing pituitary tumors: up-regulation of microRNA-122 and -493 in pituitary carcinomas

MicroRNAs (miRNAs) are involved in cell proliferation, differentiation, and apoptosis, and can function as tumor suppressor genes or oncogenes. The expression of miRNAs in pituitary carcinomas has not been previously examined. We used miRNA profiling with 1,145 probes to study miRNA expression in normal anterior pituitary (6 cases), adrenocorticotropin (ACTH)-producing adenomas (8 cases), and ACTH-producing pituitary carcinomas (two cases). Real-time RT-PCR and in situ hybridization were used to confirm and independently validate miRNAs that were significantly up-regulated or down-regulated between the pituitary tissues. There were more miRNAs up- (188) or down-regulated (160) between adenomas and normal pituitaries compared to carcinomas and normal pituitaries (92 up- and 91 down-regulated) or between carcinomas and adenomas (46 up- and 52 down-regulated). Both real-time RT-PCR and in situ hybridization showed significant up-regulation of miRNA-122 between pituitary carcinomas and adenomas. MiRNA-493 was also up-regulated in carcinomas compared to ACTH adenomas. Analysis of genes that miRNA-493 interacts with included LGALS3 and RUNX2 ( http://microrna.sanger.ac.uk ) both of which have been shown to have roles in pituitary tumor cell growth. These results provide information about marker miRNAs that may lead to further insights into the regulation of pituitary tumor growth and development.

Epigenetic down-regulation of the tumor suppressor gene PRDM1/Blimp-1 in diffuse large B cell lymphomas: a potential role of the microRNA let-7

PRDM1/Blimp-1, a master regulator for B cell terminal differentiation, is a putative tumor suppressor in diffuse large B cell lymphomas (DLBCL). Inactivating mutations of PRDM1 have been previously identified in a subset of nongerminal center B cell-like (GCB) DLBCL. We investigated the presence of alternative mechanisms of down-regulating PRDM1 in a cohort of 25 primary DLBCL and six DLBCL cell lines. While some DLBCL, predominantly the GCB-type, showed low levels of both PRDM1alpha mRNA and protein, presumably as a result of direct transcription repression, discordant expressions between the two were identified in a subset of DLBCL without PRDM1 mutations, the primarily non-GCB type, consistent with translational down-regulation. This subset of DLBCL exhibits relatively high PRDM1alpha mRNA levels but low levels of PRDM1. Data obtained from expression analysis, luciferase reporter assays, and transfection experiments support a role of targeting of PRDM1 by microRNA let-7 family in mediating this down-regulation. Let-7, in particular let-7b, is overexpressed in DLBCL relative to normal GCB cells, suggesting that it is deregulated. Thus, abnormal epigenetic down-regulation of PRDM1 by let-7 and other microRNAs may represent an alternative mechanism of reducing normal PRDM1 function in a subset of DLBCL with relatively high PRDM1alpha mRNA expression and unmutated PRDM1. These findings provide further evidence for an important role of impairment of terminal B cell differentiation in DLBCL pathogenesis.

A minicircuitry involving REST and CREB controls miR-9-2 expression during human neuronal differentiation

miRNAs play key roles in the nervous system, where they mark distinct developmental stages. Accordingly, dysregulation of miRNA expression may have profound effects on neuronal physiology and pathology, including cancer. Among the neuronal miRNAs, miR-9 was shown to be upregulated during in vitro neuronal differentiation and downregulated in 50% of primary neuroblastoma tumors, suggesting a potential function as an oncosuppressor gene. In this study we characterized the promoter and the transcriptional regulation of the miR-9-2 gene during neuronal differentiation. We found that, despite its localization inside an exon of a putative host-gene, miR-9-2 is expressed as an independent unit with the promoter located in the upstream intron. By promoter fusion and mutational analyses, together with RNAi and Chromatin immunoprecipitation assays, we demonstrated that the concerted action of the master transcriptional factors RE1-silencing transcription factor (REST) and cAMP-response element binding protein (CREB) on miR-9-2 promoter induces miRNA expression during differentiation. We showed that the repressor REST inhibits the activity of the miR-9-2 promoter in undifferentiated neuroblastoma cells, whereas REST dismissal and phosphorylation of CREB trigger transcription in differentiating cells. Finally, a regulatory feed-back mechanism, in which the reciprocal action of miR-9 and REST may be relevant for the maintenance of the neuronal differentiation program, is shown.

Phosphorylation of the RNase III enzyme Drosha at Serine300 or Serine302 is required for its nuclear localization

The RNaseIII enzyme Drosha plays a pivotal role in microRNA (miRNA) biogenesis by cleaving primary miRNA transcripts to generate precursor miRNA in the nucleus. The RNA binding and enzymatic domains of Drosha have been characterized and are on its C-terminus. Its N-terminus harbors a nuclear localization signal. Using a series of truncated Drosha constructs, we narrowed down the segment responsible for nuclear translocation to a domain between aa 270 and aa 390. We further identified two phosphorylation sites at Serine300 (S300) and Serine302 (S302) by mass spectrometric analysis. Double mutations of S→A at S300 and S302 completely disrupted nuclear localization. Single mutation of S→A at S300 or S302, however, had no effect on nuclear localization indicating that phosphorylation at either site is sufficient to locate Drosha to the nucleus. Furthermore, mimicking phosphorylation status by mutating S→E at S300 and/or S→D at S302 restored nuclear localization. Our findings add a further layer of complexity to the molecular anatomy of Drosha as it relates to miRNA biogenesis.

miRNAs in colon and rectal cancer: A consensus for their true clinical value

Numerous miRNAs are deregulated in human cancers and experimental evidence indicates that they can play roles as oncogenes or tumor suppressor genes. Colorectal cancer represents a wide and exciting area of research for molecular biology, due to the growing need of a molecular classification as well as prognostic and predictive molecular factors that may guide oncologists in the clinical management of patients. The aim of this review is to analyze the state of art of the miRNA expression profiles in colorectal cancer to explore some perspectives in this research field.

MicroRNAs in ovarian carcinomas

The molecular mechanisms involved in epithelial ovarian cancer initiation and progression are just beginning to be elucidated. In particular, it has become evident that microRNAs (miRNAs or miRs), a class of molecules that post-transcriptionally regulate gene expression, play a major role in ovarian tumorigenesis. Several microRNA profiling studies have identified changes in microRNA patterns that take place during ovarian cancer development. While most deregulated microRNAs are down-regulated in cancer, and may therefore act as tumor suppressors, others are elevated and may represent novel oncogenes in this disease. A number of microRNAs identified as aberrantly expressed in ovarian carcinoma have been shown to have important functional roles in cancer development and may therefore represent targets for therapy. In addition, some of the microRNA patterns may have prognostic significance. The identification of functional targets represents a major hurdle in our understanding of microRNA function in ovarian carcinoma, but significant progress is being made. It is hoped that a better understanding of the microRNA expression and roles in ovarian cancer may provide new avenues for the detection, diagnosis, and therapy of this deadly disease.

MicroRNA expression in ileal carcinoid tumors: downregulation of microRNA-133a with tumor progression

MicroRNAs (miRNAs) are involved in cell proliferation, differentiation, and apoptosis and can function as tumor suppressor genes or oncogenes. The role of miRNAs in neuroendocrine tumors such as ileal carcinoids is largely unknown. We examined the differential expression of 95 miRNAs by RT-PCR using the QuantiMir System in eight matching primary and metastatic carcinoid tumors from the ileum. All miRNAs chosen for the QuantiMir System array were based on their potential functions related to cancer biology, cell development, and apoptosis. The expression of miRNAs for the samples was normalized to miRNA-197, and the matching primary and metastatic tumors were compared. There was downregulation of miRNA-133a, -145, -146, -222, and -10b in all samples between the primary and matching metastatic tumors and upregulation of miRNA-183, -488, and -19a+b in six of eight metastatic carcinoids compared to the primary tumors. miRNA-133a was further analyzed by TaqMan real-time RT-PCR and northern hybridization using six additional matching primary and metastatic samples, which supported the PCR array findings. There were significant differences in miRNA-133a expression with downregulation in the metastasis compared to the primary in the eight original cases (P<0.009) and in the six additional cases used for validation (P<0.014). Laser capture microdissection and real-time RT-PCR analysis using normal ileum found miRNA-133a expression in normal enterochromaffin cells. In situ hybridization in normal ileum showed that some of the mucosal endocrine cells expressed miRNA-133a. Both primary and metastatic ileal carcinoid tumors expressed miRNA-133a by in situ hybridization. These results provide information about novel marker miRNAs that may be used as biomarkers and/or therapeutic targets in intestinal carcinoid tumors.

Anticancer Role of PPARgamma Agonists in Hematological Malignancies Found in the Vasculature, Marrow, and Eyes

The use of targeted cancer therapies in combination with conventional chemotherapeutic agents and/or radiation treatment has increased overall survival of cancer patients. However, longer survival is accompanied by increased incidence of comorbidities due, in part, to drug side effects and toxicities. It is well accepted that inflammation and tumorigenesis are linked. Because peroxisome proliferator-activated receptor (PPAR)-gamma agonists are potent mediators of anti-inflammatory responses, it was a logical extension to examine the role of PPARgamma agonists in the treatment and prevention of cancer. This paper has two objectives: first to highlight the potential uses for PPARgamma agonists in anticancer therapy with special emphasis on their role when used as adjuvant or combined therapy in the treatment of hematological malignancies found in the vasculature, marrow, and eyes, and second, to review the potential role PPARgamma and/or its ligands may have in modulating cancer-associated angiogenesis and tumor-stromal microenvironment crosstalk in bone marrow.

MicroRNA-224 is upregulated in HepG2 cells and involved in cellular migration and invasion

BACKGROUND AND AIM

MicroRNAs are a class of small non-coding RNAs that negatively regulate the expression of their target genes. The aim of the present study was to explore the effects of microRNA on biological behaviors of HepG2 cells and further analyze its characteristics.

METHODS

We detected different expression profiles of miRNAs in HepG2 and L02 cell lines by microRNA microarray. Northern blot, quantitative real-time polymerase chain reaction, methylthiazolyl tetrazolium, fluorescence-activated cell sorting, scratch wound, transwell migration and Matrigel invasion assays and western blot were carried out to determine whether or not microRNA-224 (miR-224) can influence the biological behaviors of HepG2 cells.

RESULTS

MiR-224 was significantly upregulated in HepG2 cells. Cell proliferation, migration and invasion, but not cell cycles, were altered after changing the expression of miR-224. Taking invasion and migration as a breakthrough, a close relationship between the expression of miR-224 and its proteins such as PAK4 and MMP9, which were involved in the invasion of tumor, was found.

CONCLUSIONS

Overexpression of miR-224 was involved in the malignant phenotype of HepG2 cells, and it may be an important factor in regulating the migration and invasion of HepG2 cells.

Use of microRNAs in early detection and screening for colorectal cancer

Recent studies have identified unique small RNAs, called microRNAs (miRNAs), in colorectal cancer. They can be used to accurately diagnose the presence of colorectal cancer and help predict disease recurrence. Upregulation or downregulation of specific miRNAs are associated with the progression of colorectal cancer. MiRNAs are implicated in tumor metastasis and cytotoxic drug resistance in colorectal cancer. Differential expression of specific miRNAs in tissues and blood offers the prospect of their use in early detection and screening for colorectal cancer. MiRNAs may be important targets for cancer gene therapies, and their manipulation has potential in both prevention of recurrence and palliation. In this article, we will review the potential use of these biomarkers in early detection and screening for colorectal cancer.