Linlang Guo

Gene expression profiling of drug-resistant small cell lung cancer cells by combining microRNA and cDNA expression analysis.

MicroRNAs (miRNAs) are now known to play important roles in the regulation of gene expression for developmental timing, cell proliferation and apoptosis. Therefore, it is likely that they also modulate sensitivity and resistance to anti-cancer drugs. To better understand the molecular mechanisms of multidrug resistance in SCLC and identify novel molecular markers, we evaluated the expression of 856 miRNAs and approximately 22,000 genes using miRNA microarray and cDNA microarray in cellular models of SCLC which were widely used as sensitive (NCI-H69) and resistant cell lines (NCI-H69AR) to chemotherapy. We also analysed the correlations between miRNA and mRNA expression patterns. Further studies were tested to determine whether the differentially expressed miRNAs were involved in multidrug resistance in SCLC. Our results showed that 61 miRNAs are presented significantly (>3-fold) including up-regulation of 24 miRNAs and down-regulation of 37 miRNAs. Among these miRNAs, 48 of 61 differentially expressed miRNAs were firstly reported to be closely associated with drug resistance and 37.7% (24/61) of miRNA genes were organised as 10 clusters in total 61 significantly expressed miRNAs. We also found that only 27 of 69 miRNAs were significantly correlated with 604 of 21,522 70 mRNA transcripts by MAS database. The sensitivity to anti-cancer drugs Cisplatin, Etoposide and Doxorubicin greatly increased or reduced following transfection of the drug-resistant H69AR cells with the mimics or antagomirs of miR-134, miR-379 and miR-495, respectively. miR-134 increases the cell survival by inducing G1 arrest in H69AR cells. MRP1/ABCC1 is negatively regulated by miR-134 and down-regulation of MRP1/ABCC1 at the protein level largely correlates with elevated levels of miR-134 in H69AR cells. Our results support for the first time a substantial role for miRNAs in multidrug resistance in SCLC. miR-134 could be a causal factor of the down-regulation of MRP1/ABCC1 in H69AR cells. These findings provide valuable information for potential utility of these miRNAs as specific diagnostic biomarkers and novel therapeutic approaches for drug resistance of SCLC.

Long non-coding RNA TUG1 is involved in cell growth and chemoresistance of small cell lung cancer by regulating LIMK2b via EZH2

BackgroundTaurine upregulated gene1 (TUG1) as a 7.1-kb lncRNA, has been shown to play an oncogenic role in various cancers. However, the biological functions of lncRNA TUG1 in small cell lung cancer (SCLC) remain unknown. The aim of this study is to explore the roles of TUG1 in cell growth and chemoresistance of SCLC and its possible molecular mechanism.MethodsThe expression of TUG1 in thirty-three cases of SCLC tissues and SCLC cell line were examined by quantitative RT-PCR (qRT-PCR). The functional roles of TUG1 in SCLC were demonstrated by CCK8 assay, colony formation assay, wound healing assay and transwell assay, flow cytometry analysis and in vivo study through siRNA or shRNA mediated knockdown. Western blot assays were used to evaluate gene and protein expression in cell lines. Chromatin immunoprecipitation (ChIP) and RNA binding protein immunoprecipitation (RIP) were performed to confirm the molecular mechanism of TUG1 involved in cell growth and chemoresistance of small cell lung cancer.ResultsWe found that TUG1 was overexpressed in SCLC tissues, and its expression was correlated with the clinical stage and the shorter survival time of SCLC patients. Moreover, downregulation of TUG1 expression could impair cell proliferation and increased cell sensitivity to anticancer drugs both in vitro and in vivo. We also discovered that TUG1 knockdown significantly promoted cell apoptosis and cell cycle arrest, and inhibited cell migration and invasion in vitro . We further demonstrated that TUG1 can regulate the expression of LIMK2b (a splice variant of LIM-kinase 2) via binding with enhancer of zeste homolog 2 (EZH2), and then promoted cell growth and chemoresistance of SCLC.ConclusionsTogether, these results suggested that TUG1 mediates cell growth and chemoresistance of SCLC by regulating LIMK2b via EZH2.

Long noncoding RNA-HOTAIR affects chemoresistance by regulating HOXA1 methylation in small cell lung cancer cells.

Homeobox (HOX) transcript antisense RNA (HOTAIR), a long intergenic noncoding RNA (lincRNA), has been reported to play an oncogenic role in various cancers including small cell lung cancer (SCLC). However, it is not known whether HOTAIR can modulate chemoresistance in SCLC. The aim of this study is to investigate the roles of HOTAIR in chemoresistance of SCLC and its possible molecular mechanism. Knockdown of HOTAIR was carried out in SCLC multidrug-resistant cell lines (H69AR and H446AR) and the parental cell lines (H69 and H446) to assess its influence on chemoresistance. The results showed that downregulation of HOTAIR increased cell sensitivity to anticancer drugs through increasing cell apoptosis and cell cycle arrest, and suppressed tumor growth in vivo. Moreover, HOXA1 methylation increased in the resistant cells using bisulfite sequencing PCR. Depletion of HOTAIR reduced HOXA1 methylation by decreasing DNMT1 and DNMT3b expression. The interaction between HOTAIR and HOXA1 was validated by RNA immunoprecipitation. Taken together, our study suggested that HOTAIR mediates chemoresistance of SCLC by regulating HOXA1 methylation and could be utilized as a potential target for new adjuvant therapies against chemoresistance.

miR-7 modulates chemoresistance of small cell lung cancer by repressing MRP1/ABCC1.

MicroRNAs (miRNAs) represent a class of small non‐coding RNAs and have been shown to play important roles in various biological processes including cell growth, differentiation and apoptosis by regulating the target genes. miR‐7 has been described not only as a tumour suppressor gene but also as an oncogene in human cancers. The aim of this study was to investigate the functional roles of miR‐7 in chemoresistance of SCLC and its underlying mechanism. By using a bioinformatic assay, we found that MRP1/ABCC1 was a potential target gene of miR‐7. Expression of miR‐7 and MRP1/ABCC1 was examined in 44 SCLC samples by quantitative reverse transcription–polymerase chain reaction and immunohistochemistry methods. Low‐level expression of miR‐7 was associated significantly with drug responsiveness and overall survival rate of patients with SCLC, but not with gender, age and stage. There was an inverse relationship between miR‐7 and MRP1/ABCC1 expression. Downregulation of MRP1/ABCC1 level was revealed after transfection with a miR‐7 mimic in H69 AR cells. Transfection of a miR‐7 inhibitor into H69 cells restored MRP1/ABCC1 expression. A dual‐luciferase reporter assay confirmed that miR‐7 targeted predicted sites in the 3′‐untranslated region (3′‐UTR) of the MRP1/ABCC1 gene. Our data suggested that miR‐7 mediated SCLC chemoresistance by repressing MRP1/ABCC1 and may be a prognostic predictor and potential therapeutic target in human SCLC.

Upregulation of the inwardly rectifying potassium channel Kir2.1 (KCNJ2) modulates multidrug resistance of small-cell lung cancer under the regulation of miR-7 and the Ras/MAPK pathway

BackgroundKCNJ2/Kir2.1, a member of the classical inwardly rectifying potassium channel family, is commonly expressed in a wide range of tissues and cell types. Previous studies indicated that Kir2.1 may be associated with SCLC multidrug resistance (MDR). However, whether Kir2.1 can regulate MDR and its underlying mechanisms remain poorly understood in SCLC.MethodsKCNJ2/Kir2.1 expression was examined in tissues from fifty-two SCLC cases by immunohistochemistry. Overexpression or knockdown of KCNJ2/Kir21 was performed in multidrug-resistant SCLC cell lines (H69AR and H446AR) and their parental cell lines (H69 and H446) to assess its influence on cell growth, apoptosis, the cell cycle and chemoresistance.ResultsKCNJ2/Kir2.1 was expressed in 44.23% (23/52) of SCLC tissues. Overexpression of KCNJ2/Kir2.1 was correlated with the clinical stage and chemotherapy response in SCLC patients. Knockdown of KCNJ2/Kir2.1 expression using KCNJ2/Kir2.1 shRNA in H69AR and H446AR cells inhibited cell growth and sensitized the cancer cells to chemotherapeutic drugs by increasing cell apoptosis and cell cycle arrest. Forced KCNJ2/Kir2.1 expression in H69 and H446 cells promoted cell growth and enhanced multidrug resistance via reduced drug-induced apoptosis accompanied by cell cycle arrest. KCNJ2/Kir2.1 expression was also influenced by PKC and MEK inhibitors. In addition, multidrug resistance protein 1 (MRP1/ABCC1) was confirmed to interact with KCNJ2/Kir2.1 by Co-IP assays.ConclusionsKCNJ2/Kir2.1 modulates cell growth and drug resistance by regulating MRP1/ABCC1 expression and is simultaneously regulated by the Ras/MAPK pathway and miR-7. KCNJ2/Kir2.1 may be a prognostic predictor and a potentially novel target for interfering with chemoresistance in SCLC.

Non-receptor tyrosine kinase Etk regulation of drug resistance in small-cell lung cancer

Epithelial and endothelial tyrosine kinase (Etk), also known as Bmx (bone marrow X kinase), plays an important role in the apoptosis of epithelial cells. The aim of this study was to investigate whether Etk is involved in the chemoresistance of small cell lung cancer (SCLC) and to correlate the drug resistance associated proteins such as bcl-2, bcl-X(L) and p53. Drug-resistant small lung cancer cells (H69AR) which were originally developed by ADM and which demonstrated multi-drug resistance to chemotherapeutic agents were used in the study. Western blot analysis revealed that H69AR cells over-expressed the proteins Etk and bcl-X(L), but not bcl-2 and p53 when compared to parent H69 cells. Knockdown of Etk expression by Etk-specific small interfering RNA sensitised H69AR cells to chemotherapeutic drugs and inhibited bcl-X(L) expression but not bcl-2 and p53. Co-immunoprecipitation was performed to further evaluate the relationship between Etk and bcl-X(L) with anti-Etk and anti-phospho-Etk antibodies. The bcl-X(L) was accompanied with a robust increase of Etk and tyrosine phosphorylated Etk at Tyr-40 in H69AR cells. In conclusion, our results suggest that non-receptor tyrosine kinase Etk is involved in drug resistance to SCLC by mediating bcl-X(L) via Tyr(P)-40. The potential approach for downregulation of Etk activity on expression would be a novel, potentially clinically practical strategy for interfering with chemoresistance in SCLC.

MiR-335 regulates the chemo-radioresistance of small cell lung cancer cells by targeting PARP-1

The role of miR-335 in the regulation of chemosensitivity and radiosensitivity of small cell lung cancer (SCLC) was investigated. miR-335 was significantly downregulated in multi-drug-resistant SCLC H69AR and H446DDP cells compared with parental cells as detected by qRT-PCR. Then, we demonstrated the negative correlation between miR-335 expression and the chemo-radiosensitivity of SCLC cells, including cell proliferation, cell clonality and cell apoptosis. In addition, miR-335 overexpression inhibited cell migration in vitro and tumor growth in vivo, whereas inhibition of miR-335 promoted cell migration and tumor growth. The underlying mechanism was further studied. Poly [ADP-ribose] polymerase 1 (PARP-1) was identified as a direct target gene of miR-335 in SCLC by bioinformatics analysis and validated via luciferase reporter assay. Overexpression of miR-335 decreased the expression of PARP-1 mRNA and protein, and NF-κB protein levels were correspondingly downregulated, thus regulating the chemo-radiosensitivity of SCLC. Taken together, these findings indicate that miR-335 may serve as a critical regulator of chemo-radiotherapy resistance in SCLC and a new potential therapeutic target.

Down-regulation of GnT-V enhances nasopharyngeal carcinoma cell CNE-2 radiosensitivity in vitro and in vivo

The purpose of this study was to investigate the role of GnT-V on radiosensitivity in human nasopharyngeal carcinoma (NPC) both in vitro and in vivo, and the possible mechanism. The GnT-V stably suppressed cell line CNE-2 GnT-V/2224 was constructed from CNE-2 by transfection. The radiosensitivity of the cells was studied by CCK-8 assay, flow-cytometry, caspases-3 activity analysis and tumor xenografts model. The expression of Bcl-2, Bax and Bcl-xl was analyzed with or without radiation. The results showed that down-regulation of GnT-V enhanced CNE-2 radiosensitivity. The underlying mechanisms may be link to the cell cycle G2-M arrest and the reduction of Bcl-2/Bax ratio. The results suggest that GnT-V may be a potential target for predicting NPC response to radiotherapy.

Long non-coding RNA HOTTIP promotes BCL-2 expression and induces chemoresistance in small cell lung cancer by sponging miR-216a

Despite progress in treatment of small cell lung cancer (SCLC), its multidrug chemoresistance and poor prognosis still remain. Recently, we globally assessed long non-coding RNAs (lncRNAs) for contributions to SCLC chemoresistance using microarray data, in vitro and in vivo assays. Here we reported that HOTTIP, encoding a lncRNA that is frequently amplified in SCLC, was associated with SCLC cell chemosensitivity, proliferation, and poor prognosis of SCLC patients. Moreover, mechanistic investigations showed that HOTTIP functioned as an oncogene in SCLC progression by binding miR-216a and abrogating its tumor-suppressive function in this setting. On the other hand, HOTTIP increased the expression of anti-apoptotic factor BCL-2, another important target gene of miR-216a, and jointly enhanced chemoresistance of SCLC by regulating BCL-2. Taken together, our study established a role for HOTTIP in SCLC progression and chemoresistance suggest its candidacy as a new diagnostic and prognostic biomarker for clinical management of SCLC.

N‐acetylglucosaminyltransferase V modulates radiosensitivity and migration of small cell lung cancer through epithelial–mesenchymal transition

N‐acetylglucosaminyltransferase V (Gnt‐V) has been linked to the migration of various human cancers. Recently we have found that inhibition of Gnt‐V increases the radiosensitivity of cancer cells. However, the mechanisms by which Gnt‐V mediates radiosensitivity and migration, especially in small cell lung cancer (SCLC) remain unknown. In our study, two SCLC cell lines (H1688 and H146) were used to investigate whether Gnt‐V modulated the radiosensitivity and migration of SCLC cells through the epithelial–mesenchymal transition (EMT). The results showed that the expression of Gnt‐V correlated with the N stage in patients with SCLC. Overexpression of Gnt‐V led to a further increase in the relative viable cell number and survival fraction with a decrease in apoptosis rate and Bax/Bcl‐2 ratio, when the cells were treated with irradiation. By contrast, knockdown of Gnt‐V with irradiation resulted in a further decrease in the relative viable cell number and survival fraction but an increase in apoptosis rate and Bax/Bcl‐2 ratio. Cells expressing high levels of Gnt‐V increased migration whereas low levels of Gnt‐V suppressed cell migration. Besides, the transient knockdown of ZEB2 led to an increase in radiosensitivity and an inhibition in the migration of SCLC cells. Furthermore, Gnt‐V was negatively correlated with E‐cadherin expression but positively correlated with N‐cadherin, vimentin and ZEB2 expression. Finally, an in vivo study revealed that upregulation of Gnt‐V caused tumour growth more quickly, as well as the expression of EMT‐related markers (N‐cadherin, vimentin and ZEB2). Taken together, the study suggested that an elevation of Gnt‐V could lead to the radiosensitivity and migration of SCLC cells by inducing EMT, thereby highlighting Gnt‐V as a potential therapeutic target for the prevention of EMT‐associated tumour radioresistance and migration.