Expression of the microRNA regulators Drosha, Dicer and Ago2 in non-small cell lung carcinomas

Variant Analysis of miRNA Regulatory Genes in 35 Sporadic Lung Carcinoma Tumors

Lung cancer is one of the cancer types with the highest mortality worldwide. The most frequently mutated genes known to be clinically important in lung cancers are EGFR, BRAF, and KRAS genes. Therefore, the therapeutic agents developed are directed against variants that cause over-activation of the EGFR-KRAS-BRAF-BRAF-MEK/ERK signalling pathway. However, different responses of patients to Tyrosine Kinase Inhibitors (TKIs) suggest that new prognostic biomarkers should be defined and epigenetic mechanisms may be related to this situation.

METHODS

In this study, sequence analyses of AGO2, DICER, and DROSHA genes involved in miRNA biogenesis and EGFR, KRAS, and BRAF genes were performed in 35 patients with sporadic lung cancer.

RESULTS

We found variations in genes involved in miRNA biogenesis that have not been previously reported in the literature. In addition, we found 4 different variants in the EGFR gene that have been described in the literature. In addition, a statistically significant association was found between the presence of mutations in at least one of the genes involved in miRNA biogenesis and metastasis (p:0.02).

CONCLUSIONS

In conclusion, genomic dysregulation of key miRNA biogenesis genes may be one of the possible reasons for the differential response of patients to therapeutic agents and the development of metastasis in EGFR wild type tumours.

The diagnostic, prognostic role and molecular mechanism of miR-328 in human cancer

MicroRNA are non-coding small RNAs that bind to their target mRNA and cause mRNA degradation or translation inhibition. MiRNA dysregulation is linked to a variety of human cancers and has a role in the genesis and development of cancer pathology. MiR-328 has been reported to be involved in various human cancers. And miR-328 is considered a key regulator in human cancer. It participates in biological processes such as proliferation, apoptosis, invasion, migration, and EMT. The present review will combine the basic and clinical studies to find that miR-328 promotes tumorigenesis and metastasis in human cancer. And we will describe the diagnostic, prognostic, and therapeutic value of miR-328 in various human cancers.

Construction of a gold nanoparticle-based single-molecule biosensor for simple and sensitive detection of Argonaute 2 activity

Argonaute 2 (Ago2) is an essential component of the RNA-induced silencing complex (RISC) and it participates in diverse physiological processes, while dysregulation of Ago2 activity is closely linked to a variety of human diseases including cancers. The reported Ago2 assays often suffer from laborious procedures, complicated reaction schemes, and unsatisfactory sensitivity. Herein, we develop a new gold nanoparticle (AuNP)-based single-molecule biosensor for simple and sensitive detection of Ago2 activity. The Ago2-responsive AuNP nanoprobe is constructed through the self-assembly of multiple Cy5-labeled signal probes onto the AuNP, in which the Cy5 fluorescence is efficiently quenched by the AuNP. Target Ago2 can bind with guide RNA to form an active RISC, inducing the cyclic cleavage of the signal probes and the release of Cy5 moieties from the AuNP nanoprobe. The released Cy5 molecules can be simply quantified by single-molecule counting. This single-molecule biosensor enables detection of Ago2 activity with the involvement of only a single AuNP nanoprobe, eliminating the use of any extra antibodies and protein enzymes. This single-molecule biosensor achieves good specificity and high sensitivity with a detection limit of 9.1 pM, and it can be exploited for the screening of Ago2 inhibitors, Ago2 kinetic analysis, and the imaging of intracellular Ago2 activity in live cells, holding great promise in Ago2-related biomedical research and clinical diagnosis.

APE1 controls DICER1 expression in NSCLC through miR-33a and miR-130b

Increasing evidence suggests different, not completely understood roles of microRNA biogenesis in the development and progression of lung cancer. The overexpression of the DNA repair protein apurinic/apyrimidinic endodeoxyribonuclease 1 (APE1) is an important cause of poor chemotherapeutic response in lung cancer and its involvement in onco-miRNAs biogenesis has been recently described. Whether APE1 regulates miRNAs acting as prognostic biomarkers of lung cancer has not been investigated, yet. In this study, we analyzed miRNAs differential expression upon APE1 depletion in the A549 lung cancer cell line using high-throughput methods. We defined a signature of 13 miRNAs that strongly correlate with APE1 expression in human lung cancer: miR-1246, miR-4488, miR-24, miR-183, miR-660, miR-130b, miR-543, miR-200c, miR-376c, miR-218, miR-146a, miR-92b and miR-33a. Functional enrichment analysis of this signature revealed its biological relevance in cancer cell proliferation and survival. We validated DICER1 as a direct functional target of the APE1-regulated miRNA-33a-5p and miR-130b-3p. Importantly, IHC analyses of different human tumors confirmed a negative correlation existing between APE1 and Dicer1 protein levels. DICER1 downregulation represents a prognostic marker of cancer development but the mechanisms at the basis of this phenomenon are still completely unknown. Our findings, suggesting that APE1 modulates DICER1 expression via miR-33a and miR-130b, reveal new mechanistic insights on DICER1 regulation, which are of relevance in lung cancer chemoresistance and cancer invasiveness.

HIF-1α-mediated augmentation of miRNA-18b-5p facilitates proliferation and metastasis in osteosarcoma through attenuation PHF2

Extensive evidence has explored the involvement of microRNAs (miRNAs) in osteosarcoma (OS). Limitedly, the concrete function of microRNA-18b-5p (miR-18b-5p) in OS remains unexplored and largely elusive. Here, we validated that miR-18b-5p significantly elevated in OS via analyzing the data from GEO database. The results showed that miR-18b-5p was overexpressed in human OS tissues and cell lines. The clinical evidence suggested that high level of miR-18b-5p was negatively correlated with the poor prognosis of OS. Meanwhile, miR-18b-5p upregulation facilitated the proliferation and metastasis of OS cells in vitro and in vivo. The mechanism exploration demonstrated that miR-18b-5p acted as a potential inhibitor of PHF2, a tumor suppressor gene, at post-transcriptional level. Moreover, hypoxia induced gene expression of miR-18b-5p was clarified to be transcriptionally mediated by HIF-1α. The clinicopathological analysis in samples of OS patients further supported that miR-18b-5p had a positive correlation with HIF-1α expression, and negative correlation with PHF2. Collectively, the present study uncovered a new molecular mechanism of OS tumorigenesis and development and miR-18b-5p might be a prognostic biomarker and potential therapeutic target for OS treatment.

Methylation of DROSHA and DICER as a Biomarker for the Detection of Lung Cancer

Simple Summary

To identify possible biomarkers for early detection of lung cancer we assessed the methylation status of genes related to carcinogenesis, DICER and DROSHA, in lung cancer patients and healthy volunteers. The relative level of methylation of DROSHA was significantly lower and DICER significantly higher in cancer patients. The relative level of methylation of DROSHA was significantly higher in patients with early-stage NSCLC (IA-IIIA) and could discriminate them from healthy people with a sensitivity of 71% and specificity of 76% for the first region and with a sensitivity of 60% and specificity of 85% for the second region. Analysis of the first region of the DICER enabled the distinction of NSCLC patients from healthy individuals with a sensitivity of 96% and specificity of 60%. The results indicate that the assessment of DICER and DROSHA methylation status can potentially be used as a biomarker for the early detection of lung cancer.

Abstract

Background: Lung cancer is the leading cause of cancer-related deaths. Early diagnosis may improve the prognosis. Methods: Using quantitative methylation-specific real-time PCR (qMSP-PCR), we assessed the methylation status of two genes (in two subsequent regions according to locations in their promoter sequences) related to carcinogenesis, DICER and DROSHA, in 101 plasma samples (obtained prior to the treatment) of lung cancer patients and 45 healthy volunteers. Results: The relative level of methylation of DROSHA was significantly lower (p = 0.012 for first and p < 0.00001 for the second region) and DICER significantly higher (p = 0.029 for the first region) in cancer patients. The relative level of methylation of DROSHA was significantly (p = 0.037) higher in patients with early-stage NSCLC (IA-IIIA) and could discriminate them from healthy people with a sensitivity of 71% and specificity of 76% (AUC = 0.696, 95% CI: 0.545–0.847, p = 0.011) for the first region and with a sensitivity of 60% and specificity of 85% (AUC = 0.795, 95% CI: 0.689–0.901, p < 0.0001) for the second region. Methylation analysis of the first region of the DICER enabled the distinction of NSCLC patients from healthy individuals with a sensitivity of 96% and specificity of 60% (AUC = 0.651, 95% CI: 0.517–0.785, p = 0.027). The limitations of the study include its small sample size, preliminary nature, being an observational type of study, and the lack of functional experiments allowing for the explanation of the biologic backgrounds of the observed associations. Conclusion: The obtained results indicate that the assessment of DICER and DROSHA methylation status can potentially be used as a biomarker for the early detection of lung cancer.

Impaired AGO2/miR-185-3p/NRP1 axis promotes colorectal cancer metastasis

Increasing evidence suggests that global downregulation of miRNA expression is a hallmark of human cancer, potentially due to defects in the miRNA processing machinery. In this study, we found that the protein expression of Argonaute 2 (AGO2), a key regulator of miRNA processing, was downregulated in colorectal cancer (CRC) tissues, which was also consistent with the findings of the Clinical Proteomic Tumor Analysis Consortium (CPTAC). Furthermore, the correlation between the levels of AGO2 and epithelial-mesenchymal transition (EMT) markers (E-cadherin and vimentin) indicated that reduced levels of AGO2 promoted EMT in CRC. Low expression of AGO2 was an indicator of a poor prognosis among CRC patients. Knockdown of AGO2 in CRC cells promoted migration, invasion and metastasis formation in vitro and in vivo but had no influence on proliferation. To provide detailed insight into the regulatory roles of AGO2, we performed integrated transcriptomic, quantitative proteomic and microRNA sequencing (miRNA-seq) analyses of AGO2 knockdown cells and the corresponding wild-type cells and identified neuropilin 1 (NRP1) as a new substrate of AGO2 via miR-185-3p. Our data provided evidence that knockdown of AGO2 resulted in a reduction of miR-185-3p expression, leading to the upregulation of the expression of NRP1, which is a direct target of miR-185-3p, and elevated CRC cell metastatic capacity. Inhibition of NRP1 or treatment with a miR-185-3p mimic successfully rescued the phenotypes of impaired AGO2, which suggested that therapeutically targeting the AGO2/miR-185-3p/NRP1 axis may be a potential treatment approach for CRC.

Dicing the Disease with Dicer: The Implications of Dicer Ribonuclease in Human Pathologies

Gene expression dictates fundamental cellular processes and its de-regulation leads to pathological conditions. A key contributor to the fine-tuning of gene expression is Dicer, an RNA-binding protein (RBPs) that forms complexes and affects transcription by acting at the post-transcriptional level via the targeting of mRNAs by Dicer-produced small non-coding RNAs. This review aims to present the contribution of Dicer protein in a wide spectrum of human pathological conditions, including cancer, neurological, autoimmune, reproductive and cardiovascular diseases, as well as viral infections. Germline mutations of Dicer have been linked to Dicer1 syndrome, a rare genetic disorder that predisposes to the development of both benign and malignant tumors, but the exact correlation of Dicer protein expression within the different cancer types is unclear, and there are contradictions in the data. Downregulation of Dicer is related to Geographic atrophy (GA), a severe eye-disease that is a leading cause of blindness in industrialized countries, as well as to psychiatric and neurological diseases such as depression and Parkinson's disease, respectively. Both loss and upregulation of Dicer protein expression is implicated in severe autoimmune disorders, including psoriasis, ankylosing spondylitis, rheumatoid arthritis, multiple sclerosis and autoimmune thyroid diseases. Loss of Dicer contributes to cardiovascular diseases and causes defective germ cell differentiation and reproductive system abnormalities in both sexes. Dicer can also act as a strong antiviral with a crucial role in RNA-based antiviral immunity. In conclusion, Dicer is an essential enzyme for the maintenance of physiology due to its pivotal role in several cellular processes, and its loss or aberrant expression contributes to the development of severe human diseases. Further exploitation is required for the development of novel, more effective Dicer-based diagnostic and therapeutic strategies, with the goal of new clinical benefits and better quality of life for patients.

TNFAIP2 Promotes Non-Small Cell Lung Cancer Cells and Targeted by miR-145-5p

Tumor necrosis factor-alpha (TNFα) is an inflammatory cytokine that regulates inflammation and tumor progression in non-small cell lung cancer (NSCLC). The higher levels of TNF α are known to induce expression of several genes such as TNFα-induced protein 2 (TNFAIP2) with a largely unknown role in NSCLC. We provide the preliminary evidence for the role of TNFAIP2 in NSCLC progression and its epigenetic regulation mediated by microRNA, miR-145-5p. The expression of TNFAIP2 was confirmed using quantitative real-time PCR, immunohistochemistry, and Western blot in NSCLC tissue and paired adjacent normal tissue. All in vitro assays were undertaken in A549 and H23 cells and chemoresistance assays were undertaken in A549/Cisplatin (DDP) and H23/DDP cell types. TNFAIP2 silencing was undertaken using lipofectamine transfection of specific siRNA. Cells were co-transfected with miR-145-5p, and TNFAIP2-3' untranslated region (UTR) or TNFAIP2 with mutated 3'UTR using the luciferase vector pGL. Cell viability, transwell migration, and invasion were assessed. The role of caspase 3 proteins in cell viability was ascertained using Western blot. The tumor tissues (and cisplatin-resistant cell lines A549/DDP and H23/DDP) expressed significantly higher levels of TNAIP2 mRNA and protein. Silencing of TNFAIP2 resulted in reduced cell viability, reduced invasion, and migration in vitro. Silencing of TNFAIP2 in A549/DDP and H23/DDP had higher expression of TNFAIP2, reduced cell viability, and increased induction of caspase 3. MiR-145-5p binds to the 3'UTR of TNFAIP2. Overexpression of MiR-145-5p reduced expression of TNFAIP2, decreased cell viability, reduced cell migration and invasion, and significantly reduced expression of caspase 3 protein. TNFAIP2 mediates tumorigenesis in NSCLC through, not completely known pathways. miR-145-5p negatively regulates TNFAIP2 expression. miR-145-5p-mediated therapies may be explored in NSCLC.

Accumulation of AGO2 Facilitates Tumorigenesis of Human Hepatocellular Carcinoma

AGO2 (Argonaute RISC Catalytic Component 2) plays an important role in small RNA-guided gene silencing processes. It has been implied in tumorigenesis of different types of tumors. In this study, we found that AGO2 expression was remarkably increased in human hepatocellular carcinoma (HCC) tissues when compared with adjacent noncancerous tissues. High expression of AGO2 was associated with poor prognosis in HCC patients. The CRISPR/Cas9-mediated knockout of AGO2 in SMMC-7721 cells inhibited cell proliferation and induced significant G1 phase arrest of cell cycle. Inhibition of cell migration was also observed in SMMC-7721 AGO2^−/− cells. In vivo experiments showed that tumors grew slower in nude mice transplanted with AGO2^−/− cells than in SMMC-7721 cell-derived xenograft mice. Microarray analysis and western blot analysis revealed that AGO2 depletion decreased expression of Survivin, Vimentin, and Snail. Overexpression of AGO2 in SMMC-7721 and Huh-7 cells could reverse the knockout-induced inhibition effects on either cell behaviors or expression of Survivin, Vimentin, and Snail Therefore, our data demonstrated that AGO2 might facilitate HCC tumorigenesis and metastasis through modulating expression of Survivin, Vimentin, and Snail.

Plasma and Tissue Specific miRNA Expression Pattern and Functional Analysis Associated to Colorectal Cancer Patients

An increasing number of studies suggest the implication of microRNAs (miRNAs) in colorectal (CRC) carcinogenesis and disease progression. Nevertheless, the basic mechanism is not yet clear. We determined plasma miRNA expression levels using Agilent microarray technology followed by overlapping with The Cancer Genome Atlas (TCGA) tissue data and a qRT-PCR validation step and analysis of the altered miRNA signatures to emphasize new mechanistic insights. For TGCA dataset, we identified 156 altered miRNAs (79 downregulated and 77 upregulated) in colorectal tissue samples versus normal tissue. The microarray experiment is based on 16 control samples, 38 CRC plasma samples from colorectal cancer patients who have not undergone chemotherapy, and 17 chemo-treated samples. In the case of the analysis of CRC cancer versus healthy control we identified 359 altered miRNAs (214 downregulated and 60 upregulated), considering as the cutoff value a fold-change of ±1.5 and p < 0.01. An additional microarray analysis was performed on plasma from untreated colorectal cancer (n = 38) and chemotherapy-treated colorectal cancer patients (n = 17), which revealed 15 downregulated miRNAs and 53 upregulated miRNAs, demonstrating that the plasma miRNA pattern is affected by chemotherapy and emphasizing important regulators of drug resistance mechanisms. For the validation of the microarray data, we selected a panel of 4 miRNAs from the common miRNA signatures for colon and rectal cancer (miR-642b-3p, miR-195-5p and miR-4741). At the tissue level, the expression levels were in agreement with those observed in colorectal plasma. miR-1228-3p, the top upregulated miRNA in CRC, was chosen to be validated on tissue and plasma samples, as it was demonstrated to be downregulated at tissue level in our patient cohort. This was confirmed by TCGA data and was one example of ta ranscript that has a different expression level between tumor tissue and plasma. Developing more efficient investigation methods will help explain the mechanisms responsible for miRNAs released in biofluids, which is the most upregulated transcript in colorectal plasma samples and which can function as a prediction tool within the oncological field.

Quantifying Argonaute 2 (Ago2) expression to stratify breast cancer

BACKGROUND

Argonaute-2 (Ago2) is an essential component of microRNA biogenesis implicated in tumourigenesis. However Ago2 expression and localisation in breast cancer remains undetermined. The aim was to define Ago2 expression (mRNA and protein) and localisation in breast cancer, and investigate associations with clinicopathological details.

METHODS

Ago2 protein was stained in breast cancer cell lines and tissue microarrays (TMAs), with intensity and localization assessed. Staining intensity was correlated with clinicopathological details. Using independent databases, Ago2 mRNA expression and gene alterations in breast cancer were investigated.

RESULTS

In the breast cancer TMAs, 4 distinct staining intensities were observed (Negative, Weak, Moderate, Strong), with 64.2% of samples stained weak or negatively for Ago2 protein. An association was found between strong Ago2 staining and, the Her2 positive or basal subtypes, and between Ago2 intensity and receptor status (Estrogen or Progesterone). In tumours Ago2 mRNA expression correlated with reduced relapse free survival. Conversely, Ago2 mRNA was expressed significantly lower in SK-BR-3 (HER2 positive) and BT-20 (Basal/Triple negative) cell lines. Interestingly, high levels of Ago2 gene amplification (10-27%) were observed in breast cancer across multiple patient datasets. Importantly, knowledge of Ago2 expression improves predictions of breast cancer subtype by 20%, ER status by 15.7% and PR status by 17.5%.

CONCLUSIONS

Quantification of Ago2 improves the stratification of breast cancer and suggests a differential role for Ago2 in breast cancer subtypes, based on levels and cellular localisation. Further investigation of the mechanisms affecting Ago2 dysregulation will reveal insights into the molecular differences underpinning breast cancer subtypes.

The impact of variations in transcription of DICER and AGO2 on exacerbation of childhood B-cell lineage acute lymphoblastic leukaemia

The expression of microRNA in eukaryotic cells is subject to tightly regulated processing. The altered expression of microRNAs in a number of cancers suggests their contribution to disease pathogenesis, where processing pathways may be involved in disease pathogenesis. In the present study, we evaluated changes in the profile of two main components of microRNA biogenesis, AGO2 and DICER, and assessed their correlation with disease progression in childhood acute lymphoblastic leukaemia (ALL). To achieve this aim, 25 patients afflicted with ALL were included in the study along with 25 healthy subjects as control. The expression level of AGO2 and DICER was evaluated by real-time PCR. The results revealed an increase in the expression of DICER and a decrease in AGO2 in patients. The correlation between the alteration levels of these genes with pathologic events was also studied. This increase or decrease proved to be directly correlated with the progression of the disease particularly in L1 to L2. According to the obtained results, it can be deduced that dysregulation in transcription of DICER and AGO2, involved in the formation of mature microRNAs in cytoplasm of ALL cancer cells, is a part of the pathological molecular mechanism implicated in the exacerbation of this malignancy. Therefore, the genes involved in microRNAs biogenesis that have been studied here could be considered as candidate prognostic markers especially in childhood ALL which will help towards a better understanding of the molecular basis of ALL.

Quantifying Tip60 (Kat5) stratifies breast cancer

Breast cancer is stratified into four distinct clinical subtypes, using three key biomarkers (Her2/Neu gene status, Estrogen and Progesterone receptor status). However, each subtype is a heterogeneous group, displaying significant variation in survival rates and treatment response. New biomarkers are required to provide more precise stratification of breast cancer cohorts to inform personalised treatment options/predict outcomes. Tip60 is a member of the MYST sub-family of histone acetyltransferases (HATs), and is directly involved in genome maintenance, gene regulation and DNA damage response/repair pathways (key chemotherapeutic influencing mechanisms). We aimed to determine if quantifying Tip60 staining patterns improved breast cancer stratification. We defined Tip60 protein in vivo, quantifying location (cytoplasmic, nuclear), percent of cells and staining intensity in a breast cancer tissue microarray (n = 337). A significant association of specific Tip60 staining patterns with breast cancer subtype, ER or PR status and Tumour grade was found. Importantly, low Tip60 mRNA expression correlated with poor overall survival and relapse free survival. We found Tip60 is a biomarker able to stratify breast cancer patients, and low Tip60 expression is a significant risk factor indicating a higher chance of disease reoccurrence. This work highlights Tip60 regulation as a key factor influencing the development of breast cancer.

Premature senescence activation in DLD-1 colorectal cancer cells through adjuvant therapy to induce a miRNA profile modulating cellular death

Cancer, and particularly colon cancer, is associated with an increasing number of cases resistant to chemotherapy. One approach to overcome this, and to improve the prognosis and outcome of patients, is the use of adjuvant therapy alongside the standard chemotherapy regiment. In the present study, the effect of deuterium-depleted water (DDW) as a potential modulator of adjuvant therapy on DLD-1 colorectal cancer models was assessed. A number of functionality assays were performed, including MTT, apoptosis and autophagy, and mitochondrial activity and senescence assays, in addition to assessing the capacity to modify the pattern of released miRNA via microarray technology. No significant effect on cell viability was identified, but an increase in mitochondrial activity and a weak pro-apoptotic effect were observed in the treated DLD-1 cells cultured in DDW-prepared medium compared with those grown in standard conditions (SC). Furthermore, the findings revealed the capacity of DDW medium to promote senescence to a higher degree compared with SC. The exosome-released miRNA pattern was significantly modified for the cells maintained in DDW compared with those maintained in SC. These findings suggest that DDW may serve as an adjuvant treatment; however, a better understanding of the underlying molecular mechanism of action will be useful for developing novel and efficient therapeutic strategies, in which the transcriptomic pattern serves an important role.

Changes in plasma miR-9, miR-16, miR-205 and miR-486 levels after non-small cell lung cancer resection

PURPOSE

The majority of non-small cell lung cancer (NSCLC) patients presents with an advanced-stage disease and, consequently, exhibits a poor overall survival rate. We aimed to assess changes in plasma miR-9, miR-16, miR-205 and miR-486 levels and their potential as biomarkers for the diagnosis and monitoring of NSCLC patients.

METHODS

Plasma was collected from 50 healthy donors and from NSCLC patients before surgery (n = 61), 1 month after surgery (n = 37) and 1 year after surgery (n = 14). microRNA levels were quantified using qRT-PCR.

RESULTS

We found in NSCLC patients before treatment, both with squamous cell carcinoma (SQCC) and adenocarcinoma (ADC), significantly higher plasma miR-16 and miR-486 levels than in healthy individuals. Pre-treatment miR-205 concentrations were found to be significantly higher in SQCC than in ADC patients, and only SQCC patients presented significantly higher circulating miR-205 levels than healthy donors. SQCC plasma miR-9 levels were not different from normal control levels, but in ADC they were found to be significantly decreased. A combination of plasma miR-16, miR-205 and miR-486 measurements was found to discriminate NSCLC patients from healthy persons, with a specificity of 95% and a sensitivity of 80%. Following tumor resection, we found that the miR-9 and miR-205 levels significantly decreased, even below the normal level, whereas the increased miR-486 level persisted up to one year after surgery, and the miR-16 level decreased to normal. After tumor resection, none of the miR levels tested was found to relate to recurrence.

CONCLUSIONS

Our data indicate that miR-9, miR-16, miR-205 and miR-486 may serve as NSCLC biomarkers. The observed cancer-related pre- and post-operative changes in their plasma levels may not only reflect the presence of a primary cancer, but also of a systemic response to cancer.

Estrogen receptor expression and gene promoter methylation in non-small cell lung cancer - a short report

PURPOSE

In the past, anomalous estrogen receptor (ER) regulation has been associated with various lung pathologies, but so far its involvement in lung cancer initiation and/or progression has remained unclear. Here, we aimed at assessing in vivo and in vitro ER expression and its possible epigenetic regulation in non-small cell lung cancer (NSCLC) samples and their corresponding normal tissues and cells.

METHODS

ERα and ERβ gene expression levels were assessed using real time quantitative PCR (RT-qPCR), whereas ERα and ERβ gene promoter methylation levels were assessed using DNA bisulfite conversion followed by pyrosequencing. We included NSCLC (n = 87) and adjacent histologically normal lung tissue samples from lung cancer patients (n = 184), primary normal bronchial epithelial-derived cell cultures (n = 11), immortalized bronchial epithelial-derived cell lines (n = 3) and NSCLC derived cell lines (n = 9).

RESULTS

Using RT-qPCR we found significantly lower ERα and ERβ expression levels in the NSCLC tissue samples compared to their normal adjacent tissue samples. These lower ER expression levels were confirmed in vitro using primary normal bronchial epithelial-derived cell cultures, immortalized bronchial epithelial-derived cell lines and NSCLC-derived cell lines. By using this latter panel of cells, we found that ER gene promoter hypermethylation was associated with decreased ER expression. In addition we found that in tumor and normal lung tissues, smoking was associated with decreased ER expression and that normal lung tissues with a low ERβ expression level exhibited increased smoking-related DNA adducts.

CONCLUSIONS

Taken together, our results indicate that decreased ER expression mediated by DNA methylation may play a role in NSCLC development.

The functional status of DNA repair pathways determines the sensitization effect to cisplatin in non-small cell lung cancer cells

PURPOSE

Cisplatin can cause a variety of DNA crosslink lesions including intra-strand and inter-strand crosslinks (ICLs), which are associated with the sensitivity of cancer cells to cisplatin. Here, we aimed to assess the contribution of the Fanconi anemia (FA), homologous recombination (HR) and nucleotide excision repair (NER) pathways to cisplatin resistance in non-small cell lung cancer (NSCLC)-derived cells.

METHODS

The expression of FA, HR and NER pathway-associated genes was assessed by RT-qPCR and Western blotting. siRNAs were used to knock down the expression of these genes. CCK-8 and flow cytometry assays were used to assess the viability and apoptotic rate of NSCLC-derived cells, respectively. Immunofluorescence and alkaline comet assays were used to assess the repair of ICLs.

RESULTS

We found that acquired cisplatin-resistant NSCLC-derived A549/DR cells exhibited markedly enhanced FA and HR repair pathway capacities compared to its parental A549 cells and another independent NSCLC-derived cell line, Calu-1, which possesses a moderate innate resistance to cisplatin. siRNA-mediated silencing of the FA-associated genes FANCL and RAD18 and the HR-associated genes BRCA1 and BRCA2 significantly potentiated the sensitivity of A549/DR cells to cisplatin compared to A549 and Calu-1 cells, suggesting that the acquired cisplatin resistance in A549/DR cells may be attributed to enhanced FA and HR pathway capacities responsible for ICL repair. Although we found that expression knockdown of the NER-associated genes XPA and ERCC1 sensitized the three NSCLC-derived cell lines to cisplatin, the sensitization effect was more significant in Calu-1 cells than in A549 and A549/DR cells, implying that the innate cisplatin resistance in Calu-1 cells may result from an increased NER activity.

CONCLUSIONS

Our results indicate that the functional status of DNA repair pathways determine the sensitivity of NSCLC cells to cisplatin. Direct targeting of the pathway that is involved in cisplatin resistance may be an effective strategy to surmount cisplatin resistance in NSCLC.

Nitric oxide increases the migratory activity of non-small cell lung cancer cells via AKT-mediated integrin αv and β1 upregulation

BACKGROUND

Previously, nitric oxide (NO) has been found to affect the metastatic behavior of various types of cancer. In addition, it has been found that alterations in integrin expression may have profound effects on cancer cell survival and migration. Here, we aimed at assessing the effects of non-toxic concentrations of NO on human non-small cell lung cancer (NSCLC) cells, including the expression of integrins and the migration of these cells.

METHODS

The cytotoxic and proliferative effects of NO on human NSCLC-derived H460, H292 and H23 cells were tested by MTT assay. The migration capacities of these cells was evaluated by wound healing and transwell migration assays. The expression of integrins and migration-associated proteins was determined by Western blot analyses.

RESULTS

We found that NO treatment caused a significant increase in the expression of integrin αv and β1 in all three NSCLC-derived cell lines tested. Known migration-associated proteins acting downstream of these integrins, including focal adhesion kinase (FAK), active RhoA (Rho-GTP) and active cell division control 42 (Cdc42-GTP), were found to be significantly activated in response to NO. In addition, we found that NO-treated cells showed an increased motility and that this motility was associated with a significant increase in the number of filopodia per cell. We also found that NO-treated cells exhibited increased active protein kinase G (PKG), protein kinase B (AKT) and FAK expression levels. Using a pharmacological approach, we found that the integrin-modulating effect of NO is most likely brought about by a PKG/AKT-dependent mechanism, since the observed changes in integrin expression were abolished by AKT inhibitors, but not by FAK inhibitors.

CONCLUSION

Our data suggest a novel role of NO in the regulation of integrin expression and, concomitantly, the migratory capacity of NSCLC cells.

Hypoxia-inducible microRNA-488 regulates apoptosis by targeting Bim in osteosarcoma

BACKGROUND

Osteosarcoma is a malignant bone cancer of which the survival rate is still low. One reason for this low survival rate is drug resistance. In the past, it has been shown that microRNAs may play critical roles in osteosarcoma development and drug resistance. The mechanisms by which osteosarcoma cells acquire this resistance have, however, remained largely unknown. Here, we aimed at assessing the role of microRNA-488 in the acquisition of drug resistance by osteosarcoma cells.

METHODS

Quantitative RT-PCR was used to measure the expression of microRNA-488 in primary osteosarcoma samples and in osteosarcoma-derived cells, whereas microRNA-488 mimics and inhibitors were used to modify its expression in these cells. Luciferase reporter, Western blotting, cell viability, apoptosis and ChIP assays were used to assess the various effects of modified microRNA-488 expression in osteosarcoma-derived cells.

RESULTS

We found that microRNA-488 is over-expressed in primary osteosarcoma tissues and osteosarcoma-derived cells and that hypoxia can induce microRNA-488 expression via binding to the hypoxia response element (HRE) in its promoter. We also found that exogenous over-expression of microRNA-488 promotes the proliferation, reduces the apoptosis and decreases the sensitivity to chemotherapy (doxorubicin) of osteosarcoma cells via direct targeting of the tumor suppressor Bim, which is a mediator of apoptosis. In contrast, we found that transfection of a microRNA-488 inhibitor resulted in an increase in both apoptosis and drug sensitivity, and a decrease in proliferation.

CONCLUSIONS

Our data suggest that miRNA-488 may serve as a predictor of response to chemotherapy and as a therapeutic target in human osteosarcomas.

miR-346 Up-regulates Argonaute 2 (AGO2) Protein Expression to Augment the Activity of Other MicroRNAs (miRNAs) and Contributes to Cervical Cancer Cell Malignancy

MicroRNAs (miRNAs) are a class of post-transcriptional regulators of gene expression, and AGO2 is essential for miRNA activity. In this study, we focused on the regulation of AGO2 by miR-346 and the consequences in cervical cancer cells. miR-346 enhanced the expression of AGO2, resulting in the increased activity of other miRNAs and contributing to the malignancy of HeLa cells. GRSF1 participated in the regulation of AGO2 by miR-346, and the middle sequence of miR-346 was vital for the synergy effect of miR-346 and GRSF1. We determined that miR-346 promoted the migration and invasion of HeLa cells. In summary, we are the first to report that AGO2 is regulated positively by miRNA and that GRSF1 participates in the miRNA pathway.