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AIMS: Although the epidermal growth factor receptor (EGFR) and Wnt/ß-catenin signaling systems synergistically regulate many essential developmental and regenerative processes in lung cancer, the mechanisms of their crosstalk remain poorly defined. Our study aimed to investigate an interaction between EGFR and the ß-catenin signal. RESULTS: In this study, we described a potent activation of ß-catenin by EGFR, which is dependent of the PtdIns3K/AKT pathway. We found EGF activated ß-catenin signaling via phosphorylation of EGFR and AKT in EGFR-mutated PC-9 lung cancer cells. Meanwhile, EGFR tyrosine kinase inhibitors (EGFR-TKIs) regulated cancer stem-like cells (CSCs) by inhibiting autophosphorylation of EGFR and downstream signaling proteins, as well as ß-catenin. Further, ß-catenin depletion by RNA interference virtually eliminated cancer stem cell-like population in PC-9 cells in vitro. The nude mice transplantation model was also performed to confirm EGFR-TKIs strongly inhibited the ß-catenin signal and decreased CSCs. Importantly, the reduction of CSCs that sorted out by side population (SP) cells significantly reduced the migration capability. Thus, our results improved the understanding of this process to provide insights into mechanisms of responding to EGFR-TKIs. CONCLUSIONS: Our discoveries raise an intriguing question of the role of ß-catenin in EGFR-TKIs-treated cancer stem cell-like population(s) and its potential as a new therapeutic target for NSCLC in the future.

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Long non-coding RNAs (lncRNAs) are associated with the occurrence, development and prognoses of non-small cell lung cancer (NSCLC). In the present study, we investigated the functional mechanisms of the lncRNA XIST in two human NSCLC cell lines, A549 and NCI-H1299. In all the 5 NSCLC cell lines (NL9980, NCI-H1299, NCI-H460, SPC-A-1 and A549) tested, the expression levels of XIST were significantly elevated, as compared with those in normal human bronchial epithelial cell line BEAS-2B. In A549 and NCI-H1299 cells, knockdown of XIST by siRNA significantly inhibited the cell proliferation, migration and invasion, and promoted cell apoptosis. Furthermore, XIST knockdown elevated the expression of E-cadherin, and suppressed the expression of Bcl-2. Moreover, knockdown of XIST significantly suppressed the tumor growth in NSCLC A549 xenograft mouse model. Bioinformatic analysis and luciferase reporter assays revealed that XIST was negatively regulated by miR-449a. We further identified reciprocal repression between XIST and miR-449a, which eventually influenced the expression of Bcl-2: XIST functioned as a miRNA sponge of miR-449a, which was a negative regulator of Bcl-2. These data show that expression of the lncRNA XIST is associated with an increased growth rate and metastatic potential in NSCLC A549 and NCI-H1299 cells partially through miR-449a, and suggest that XIST may be a potential prognostic factor and therapeutic target for patients with NSCLC.

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BACKGROUND: The tetraspanin KAI1/CD82 was identified as a tumor metastasis suppressor that down-regulated in malignant progression of lung cancer. However, the underlying mechanism of anti-metastasis role of KAI1 in lung cancer is hardly known. In this paper, we sought to study the function and regulatory mechanism of KAI1 in high metastasis lung cancer cell line. METHODS: KAI1 expression was detected in high/low metastatic large lung cancer cell line L9981/NL9980 by quantitative real-time polymerase chain reaction (qRT-PCR). The tumor suppressor function of KAI1 was determined by wound healing assay after over-expression or knockdown of KAI1 in L9981 or NL9980 cells. Invasion assay was performed to detect the invasion ability of L9981 by transfection of KAI1. The effect of tumor suppressor p53 on KAI1 expression was measured by western blot and luciferase assay. Then the regulation of KAI1 due to over-expression of metastasis suppressor nm23-H1 was monitored by qRT-PCR, western blot and reporter gene assay. The progression of L9981 cells after p53 and nm23-H1 expression was detected by invasion assay. Also, methylation status of KAI1 promoter in NL9980 and L9981 cells were examined by bisulfite sequencing and methylation-specific PCR. RESULTS: We found that KAI1 is down-regulated in high metastatic L9981 cells compare with NL9980 cells. The migration and invasion of L9981 cells were remarkably suppressed in vitro by KAI1 transfection. The migration ability of NL9980 was enhanced by inhibition of KAI1. Furthermore, KAI1 expression was induced after over-expression of p53 or nm23-H1, while cell invasion was inhibited in L9981 cells. The results of reporter analysis indicated that KAI1 promoter region between -922 to -846 could response to nm23-H1. In addition, we discovered only slight methylation of KAI1 promoter, which showed that loss expression of KAI1 in L9981 cells may not due to promoter methylation. CONCLUSIONS: The results suggested that nm23-H1 was involved in the KAI1-regulated inhibition of metastasis in lung cancer cells. More insights into the relationship between KAI1 and other metastasis suppressors will pave the way for the elucidation of anti-metastasis mechanism in lung cancer.

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BACKGROUND: Our previous study found that nicotine could induce lung cancer cell epithelial-mesenchymal transition (EMT). The aim of this study is to explore the relationship between nicotine-induced EMT and lung cancer invasion and metastasis. METHODS: Real-time PCR and Western blot were used to detect the expression changes of EMT-related markers, E-cadherin and Vimentin, in A549 lung cancer cells treated with nicotine; The transposition of ß-catenin protein expression was determined by immunofluorescence; Scratch test and Transwell invasion assay were used to detect the effects of nicotine on lung cancer cell migration and invasion. RESULTS: Nicotine can significantly down-regulate the expressional level of E-cadherin mRNA and protein of A549 cells in a manner of dose and time-dependent (P<0.01, P<0.01); Nicotine can significantly up-regulate the expressional level of Vimentin mRNA and protein of A549 cells in a manner of dose and time-dependent (P<0.01, P<0.01); Immunofluorescence results showed that ß-catenin protein was significantly transfered to nucleus; Scratch test and Transwell assay showed that Nicotine could remarkably increase the migration and invasion potential of lung cancer cells (P<0.01, P<0.01). CONCLUSIONS: Nicotine can induce cancer cells EMT, and promote the invasion and metastasis ability of lung cancer cells.

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Increasing evidence reveals that deregulation of miRNAs contributes to carcinogenesis of the human non-small cell lung cancer (NSCLC). Our study discovered that the expression of miR-449a was markedly decreased in NSCLC cells with high metastatic capacity and tissues of positive lymph node metastasis. Moreover, our results showed that miR-449a could act as a tumor suppressor by inhibiting the invasion of NSCLC cells in vitro and in vivo. Mechanistically, miR-449a inhibited the expression of MAP2K1 by direct targeting its 3'UTR, and regulated the activity of MEK1/ERK1/2/c-Jun pathway through an auto-regulatory feedback loop. Furthermore, the histone methylation mediated the decreased expression of miR-449a through SUZ12. Taken together, the novel connection between miR-449a and MAP2K1 demonstrated here provided a new, potential therapeutic target for the treatment of non-small cell lung cancer.

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BACKGROUND: Anti-angiogenesis has been demonstrated to have a critical role in lung cancer pathogenesis. Here, we characterized the effect of the small-molecule angiogenesis inhibitor pazopanib on non-small cell lung cancer (NSCLC) cells. METHODS: NSCLC cells were tested for viability and migration after incubation with varying concentrations of pazopanib. Further, the phosphorylation status of extracellular signal-regulated kinase, protein kinase B, and MEK were assessed in vitro. For in vivo testing, mice grafted with NSCLC cell lines L9981 and A549 were treated orally with pazopanib. RESULTS: Pazopanib inhibits signaling pathways in tumor cells, thus blocking NSCLC cell growth and migration in vitro and inducing tumor cell arrest at G0/G1 phase. We show that pazopanib could inhibit tumor cell growth, decrease metastases, and prolong survival in two mouse xenograft models of human NSCLC. CONCLUSION: These preclinical studies of pazopanib show the possibility of clinical application and, ultimately, improvement in patient outcome.

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Intracellular nutrients and the rate of energy flowing in tumor cells are often higher than that in normal cells due to the prolonged stress of tumor-specific microenvironment. In this context, the metabolism of tumor cells provides the fuel of bio-synthesis and energy required for tumor metastasis. Consistent with this, the abnormal metabolism such as extremely active glucose metabolism and excessive accumulating of fatty acid is also discovered in metastatic tumors. Previous Studies have confirmed that the regulation of tumor metabolism can affect the tumor metastasis, and some of these have been successfully applied in clinical effective, positive way. Thus, targeting metabolism of tumor cells might be an effectively positive way to prevent the metastasis of tumor. So, our review is focused on the research development of the relationship between tumor metabolism and metastasis as well as the underlying mechanism.

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BACKGROUND: DNA promoter methylation of the tumor suppressor genes was one of the key mechanism for gene silence. The aim of this study is to investigate the difference of MGMT gene promoter methylation rate in tumor tissue and autologous controls (serum, normal lung tissue and bronchial lavage fluid) in patients with non-small cell lung cancer (NSCLC). METHODS: The databases of Medline, EMBSE, CNKI and Wanfang were searched for selection of published articles of MGMT gene promoter methylation and non-small cell lung carcinoma risk. The pooled odds ratio (OR) and percentage of MGMT for lung cancer tissue of NSCLC patients compared with normal lung tissue, plasma and the bronchial lavage fluid were pooled. RESULTS: 15 articles of association between MGMT gene promoter methylation and non small cell lung carcinoma risk were included in this meta-analysis. The combined results demonstrated the methylation rate of MGMT in NSCLC cancer tissue was 38% (95%CI: 23%-53%). For normal lung tissue, plasma and the bronchial lavage fluid were 16% (95%CI: 5%-27%), 23% (95%CI: 10%-34%) and 39% (95%CI: 23%-55%) respectively. The OR in cancer tissue was much higher than that in normal lung tissue and plasma odds ratio (OR) 3.98 (95%CI: 2.71-5.84, P<0.05) and OR 1.88 (95%CI: 1.16-3.05, P<0.05), but not in bronchial lavage fluid OR 2.05 (95%CI: 0.88-4.78, P>0.05). CONCLUSIONS: Mehtylation rate in MGMT gene promoter of cancer tissue in NSCLC patients was much higher than that in normal lung tissue and plasma, which showed a close association between NSCLC cancer and MGMT gene promoter methylation.

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AIMS: Aberrant expression of microRNAs (miRNAs) results in alterations of various biological processes (e.g., cell cycle, cell differentiation, and apoptosis) and cell transformation. Altered miRNAs expression was associated with lung carcinogenesis and tumor progression. This study aimed to investigate the function and underlying molecular events of miR-517a-3p on regulation of lung cancer cell proliferation and invasion. MAIN METHODS: Transfected miR-517a-3p mimics or inhibitors into 95D and 95C cells respectively, the effects of miR-517a-3p on lung cancer cell proliferation, migration, and invasion were detected. Bioinformatics software forecasted potential target genes of miR-517a-3p and dual luciferase reporter gene system and western blot verified whether miR-517a-3p regulates FOXJ3 expression directly. KEY FINDINGS: MiR-517a-3p was differentially expressed in lung cancer 95D and 95C cell lines that have different metastatic potential. Manipulation of miR-517a-3p expression changed lung cancer cell proliferation, migration and invasion capacity. MiR-517a-3p directly regulated FOXJ3 expression by binding to FOXJ3 promoter. SIGNIFICANCE: This study demonstrated that miR-517a-3p promoted lung cancer cell proliferation and invasion by targeting of FOXJ3 expression.

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BACKGROUND AND OBJECTIVE: Cisplatin is the first-line drug for the chemotherapy of non-small cell lung cancer (NSCLC), but the acquired chemoresistance restricted the effect of its treatment. The aim of this study is to validate the miRNAs related to the Cisplatin resistance in lung cancer and elucidate the molecular mechanisms. METHODS: We performed miRNA microarray and RT-PCR to obtain the aberrant differential expressed miRNAs between A549 and its paired Cisplatin-resistant cell line A549/DDP cells, and then we investigated the biological functions of miR-192, which is the aberrant differential expressed miRNA. After transfection of the miR-192 into A549 cells, we measured the half inhibition concentration (IC50), cell apoptosis of the trasfectant cells, and then we used biological softwares and dual-luciferase report assay to explore the target gene of the miR-192, which was further validated by RT-PCR and Western blot. RESULTS: MiR-192 was highly over-expressed in A549/DDP cells , whose quantity was 37.59±0.35 fold higher than that in A549 cells. Overexpression of miR-192 in A549 cells significantly conferred resistance to Cisplatin and inhibited apoptosis. By contrast, down-expression of miR-192 in A549/DDP cells remarkably restrained the Cisplatin resistance and induced apoptosis. MiR-192 binded to Bim 3'-UTR and negatively regulated Bim expression at the post-transcriptional level in lung adenocarcinoma cells. CONCLUSIONS: Our data suggested that miR-192 induced Cisplatin-resistance and inhibited cell apoptosis in lung cancer via negative targeting Bim expression.

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MicroRNAs (miRNAs) are small, non-coding RNAs which can function as oncogenes or tumor suppressor genes in human cancers. Emerging evidence reveals that deregulation of miRNAs contributes to the human non-small cell lung cancer (NSCLC). In the present study, we demonstrated that the expression levels of miR-132 were dramatically decreased in examined NSCLC cell lines and clinical NSCLC tissue samples. Then, we found that introduction of miR-132 significantly suppressed the migration and invasion of lung cancer cells in vitro, suggesting that miR-132 may be a novel tumor suppressor. Further studies indicated that the EMT-related transcription factor ZEB2 was one direct target genes of miR-132, evidenced by the direct binding of miR-132 with the 3' untranslated region (3' UTR) of ZEB2. Further, miR-132 could decrease the expression of ZEB2 at the levels of mRNA and protein. Notably, the EMT marker E-cadherin or vimentin, a downstream of ZEB2, was also down-regulated or up-regulated upon miR-132 treatment. Additionally, over-expressing or silencing ZEB2 was able to elevate or inhibit the migration and invasion of lung cancer cells, parallel to the effect of miR-132 on the lung cancer cells. Meanwhile, knockdown of ZEB2 reversed the enhanced migration and invasion mediated by anti-miR-132. These results indicate that miR-132 suppresses the migration and invasion of NSCLC cells through targeting ZEB2 involving the EMT process. Thus, our finding provides new insight into the mechanism of NSCLC progression. Therapeutically, miR-132 may serve as a potential target in the treatment of human lung cancer.

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BACKGROUND: Aberrant methylation of CpG islands acquired in tumor cells in promoter regions plays an important role in carcinogenesis. Accumulated evidence demonstrates P(16INK4a) gene promoter hypermethylation is involved in non-small cell lung carcinoma (NSCLC), indicating it may be a potential biomarker for this disease. The aim of this study is to evaluate the frequency of P(16INK4a) gene promoter methylation between cancer tissue and autologous controls by summarizing published studies. METHODS: By searching Medline, EMBSE and CNKI databases, the open published studies about P(16INK4a) gene promoter methylation and NSCLC were identified using a systematic search strategy. The pooled odds of P(16INK4A) promoter methylation in lung cancer tissue versus autologous controls were calculated by meta-analysis method. RESULTS: Thirty-four studies, including 2 652 NSCLC patients with 5 175 samples were included in this meta-analysis. Generally, the frequency of P(16INK4A) promoter methylation ranged from 17% to 80% (median 44%) in the lung cancer tissue and 0 to 80% (median 15%) in the autologous controls, which indicated the methylation frequency in cancer tissue was much higher than that in autologous samples. We also find a strong and significant correlation between tumor tissue and autologous controls of P(16INK4A) promoter methylation frequency across studies (Correlation coefficient 0.71, 95% CI:0.51-0.83, P<0.0001). And the pooled odds ratio of P(16INK4A) promoter methylation in cancer tissue was 3.45 (95% CI: 2.63-4.54) compared to controls under random-effect model. CONCLUSION: Frequency of P(16INK4a) promoter methylation in cancer tissue was much higher than that in autologous controls, indicating promoter methylation plays an important role in carcinogenesis of the NSCLC. Strong and significant correlation between tumor tissue and autologous samples of P(16INK4A) promoter methylation demonstrated a promising biomarker for NSCLC.

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Lung cancer is one of the most common diseases that endanger health and life of people domestically. A number of recurrence and death of lung cancer originated from metastasis. As a key step in metastasis of lung cancer, epithelial to mesenchymal transition involved down-regulation of E-cadherin, as well as regulated by EMT transcription factors. HATs and HDACs is a protein family that catalyzes acetylation and deacetylation of histones. Not only they have vital functions in tumor pathogenesis, but also participate in the EMT of lung cancer. HATs and HDACs interact with certain EMT transcription factors. Moreover, the function of these EMT transcription factors may be regulated by acetylation, which has influence on EMT program in lung cancer. Therefore, this review introduces the event of HATs and HDACs function in EMT of lung cancer, and investigate the molecular mechanism of their interaction. Then, the potential of HDAC inhibitor utilization in the inhibition of EMT and lung cancer therapy were discussed, as to pave the way for the related basic research and clinical practice.

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Lung cancer is one of the malignant tumors with fastest growing rates in incidence and mortality in our country, also with largest threat to human health and life. However, the exact mechanisms underlying lung cancer development remain unclear. The microenvironment of tumor hypoxia was discovered in 1955, but hypoxia in lung cancer tissues had not been successfully detected till 2006. Further studies show that hypoxia not only functions through the resistance to radiotherapy, but also regulates lung cancer development, invasion, metastasis, chemotherapy resistance and prognosis through an important oncogene HIF (hypoxia inducible factor), with its regulators PHD (prolyl hydroxylase domain) and pVHL (product of von Hippel-Lindau gene). Therefore, hypoxia, HIF, PHD and pVHL should be considered as potential therapeutic targets for lung cancer pathogenesis and progression.

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Lung cancer is the leading cause of cancer-related death and thus a major health problem nowadays. No early diagnostic method is ideal up to now. Changes in DNA methylation occur on early stage of lung cancer. Detection of DNA methylation is expected to be an important method in early diagosis of lung cancer.

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BACKGROUND AND OBJECTIVE: MicroRNAs (miRNAs) regulate a wide range of cancer-associated processes, including cell division, proliferation, cell cycle, apoptosis, angiogenesis, invasion, and metastasis. A microarray was performed to analyze metastasis-related miRNAs with different metastastic potentials and to further elucidate their mechanism in the large-cell lung cancer cell lines. METHODS: L9981 and NL9980 cells were harvested, and total RNA was extracted for CY3. RNA hybridization was then performed on the chip with marked miRNAs. MiRNAs with significantly different expression were selected through statistical analysis. A real-time polymerase chain reaction (PCR) was employed to validate the results of the microarray, and target genes were predicted using bioinformatics. RESULTS: Expressions of 22 miRNAs were significantly different in the L9981/NL9980 cell lines. Compared with the NL9980, 13 miRNAs were upregulated in the L9981 cell lines, whereas 9 miRNAs were downregulated. The result of miR-125a-3p expression based on real-time PCR was consistent with the microarray. Insulin-like growth factor 2 might be a target gene of miR-125a-3p. CONCLUSION: The metastatic miRNA profile in large-cell lung cancer was successfully screened out.

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Dickkopf-1 (DKK1) is an inhibitor of Wnt/ß-catenin signaling pathway. High levels of DKK1 protein were found in a series of cancers. However, the role of DKK1 in the progression of esophageal carcinoma is not fully understood. In the present study, RT-PCR and Western blot were used to detect the expression of DKK1 in esophageal carcinoma tissues, matched adjacent normal esophageal tissues, and esophageal carcinoma cell lines. Our results showed that the expression of DKK1 was upregulated on both mRNA and protein levels in esophageal carcinoma tissues compared with the adjacent normal esophageal tissues, meanwhile, in four esophageal carcinoma cell lines analyzed, expression of DKK1 was detected with different levels. Immunohistochemistry and immunofluoresence revealed that the distribution of DKK1 was mainly in the cytoplasm in both carcinoma tissues and cell lines. To further explore the biological effects of DKK1 on proliferation, cell cycle and invasion capability, we constructed the eukaryotic expression vector pCMV-Tab-2b-DKK1 which can effectively overexpress DKK1. Subsequently, we observed that exogenous expression of DKK1 in EC9706 cell line resulted in an increased rate of proliferation, and S stage and G2/M stage ratio whereas G0/G1 ratio was decreased. In order to evaluate the invasion capability Boyden chamber was analyzed which implied that overexpression of DKK1 resulted in an increase in the invasion ability in EC9706 cell line. Taken together, the study indicates that DKK1 might be a key regulator in the progression of esophageal carcinoma and a potential therapeutic target in esophageal carcinoma.

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AIM: To investigate the endogenous signaling pathways associated with high proliferation potential of breast cancer cells. METHODS: Breast cancer cell lines LM-MCF-7 and MCF-7 with high and low proliferation capability were used. The promoter activity of fatty acid synthase (FASN) was examined using luciferase reporter gene assay. The expression level of FASN mRNA was measured using RT-PCR and real time PCR, respectively. The level of leukotriene B4 (LTB4) was determined with ELISA. The expression levels of 5-lipoxygenase (5-LOX) was analyzed using RT-PCR and Western blot, respectively. 5-Bromo-20-deoxyuridine (BrdU) incorporation assay was used to study the proliferation of LM-MCF-7 and MCF-7 cells. RESULTS: The promoter activity of FASN was significantly higher in LM-MCF-7 cells than MCF-7 cells. Treatment of LM-MCF-7 cells with ERK1/2 inhibitor PD98059 (30-50 µmol/L) or LOX inhibitor NDGA (25 µmol/L) abolished the activation of FASN. Moreover, treatment of LM-MCF-7 cells with the specific 5-LOX inhibitor MK-886 (20-40 µmol/L) or 5-LOX siRNA (50-100 nmol/L) decreased the promoter activity of FASN. The level of LTB4, the final metabolite produced by 5-LOX, was significantly higher in LM-MCF-7 cells than MCF-7 cells. Administration of exogenous LTB4 (1-10 nmol/L) was able to stimulate the promoter activity of FASN in MCF-7 cells. Treatment of LM-MCF-7 cells with the FASN inhibitor cerulenin (10 µmol/L) reduced all the levels of p-ERK1/2, 5-LOX, and LTB4. Treatment of LM-MCF-7 cells with cerulenin, PD98059, or MK-886 abolished the proliferation. Administration of exogenous LTB4 (10 nmol/L) significantly increased BrdU incorporation in MCF-7 cells. CONCLUSION: THESE results suggest a novel positive feedback loop involving FASN/p-ERK1/2/5-LOX/LTB4/FASN contributes to the sustaining growth of breast cancer LM-MCF-7 cells.

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BACKGROUND AND OBJECTIVE: Acquired gefitinib-resistance was closely related to inefficiency of EGFR-TKI treatment in lung adenocarcinoma. However, it was not clear that how microRNAs influenced the acquired gefitinib-resistance in lung adenocarcinoma. The aim of this study is to screen and identify the microRNAs correlated with the acquired gefitinib -resistance in lung adenocarcinoma. METHODS: Morphological difference was observed in gefitinib-sensitive lung adenocarcinoma cell line PC9 cell line and gefitinib-resistance lung adenocarcinoma cell line PC9/AB11 cell line derived from PC9 cell line. Cell cycles and doubling time were detected by flow cytometry, IC50 of gefitinib was evaluated by MTT assay. The differential microRNAs related to acquired gefitinib-resistance were screened and identified by microRNA array and real-time PCR. RESULTS: There were obvious morphological differences between PC9 and PC9/AB11 cells. The doubling time, distribution of cell cycle, and the IC50 between PC9 and PC9/AB11 were significantly different. In microarray analysis, compared with PC9 cell line, 4 up-regulated microRNAs were found in PC9/AB11 cells, 9 down-regulated microRNAs were found in PC9/AB11 cells. Real-time PCR revealed that miR-138 was significantly down-regulated in PC9/AB11 cells, accord with the microarray. CONCLUSION: MicroRNAs are involved in acquired Gefitinib-resistance of lung adenocarcinoma. Our data presented here to provide an experimental basis and theory thereunder for further study of effect and molecule mechanism underlying the acquired gefitinib-resistance of lung cancer.

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BACKGROUND AND OBJECTIVE: There are no universal method to recognize and screen for lung cancer stem cell markers and indicators. Commonly used methods are flow Cytometry and learning from other cancer stem cell sorting tags to sort lung cancer stem cells. But this method has low specificity screening, the workload is huge. In this study, Serum-free suspension culture was used to enrich lung cancer stem cells, and explore method for lung cancer stem cell screening. METHODS: Human large lung cancer cell line-L9981 was cultured in serum-free and growth factors added medium, and spheres were obtained. Then the morphological differences of sphere cells and adherent L9981 cells cultured in serum-containing mediums are observed. Cell proliferation was analyzed by Vi-cell viability analyzer; invasion ability was tested by transwell assay; and in vivo tumorigenicity of the two groups of cells was studied in nude mouse. RESULTS: Compared with adherent L9981 cells cultured in serum-containing mediums, cells cultured in serum-free medium display sphere appearance. Doubling time of adherent cells and sphere cells are (56.05±1.95) h and (33.00±1.44) h respectively; Spheroid cells had higher invasion and tumorigenicity ability, 5 times and 20 times respectively, than adherent cells. CONCLUSION: Suspension cultured L9981 in Serum-free medium could form spheroid populations. Cells in spheres had higher ability of invasion and Tumorigenicity than adherent L9981 cells. These results indicated spheroid L9981 cells contained enriched lung cancer stem cells, and Serum-free suspension culture can be a candidate method for enriching lung cancer stem cell.

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