MARCKSL1-2 reverses docetaxel-resistance of lung adenocarcinoma cells by recruiting SUZ12 to suppress HDAC1 and elevate miR-200b.

BACKGROUND: Long non-coding RNAs (lncRNAs) are implicated in the development of multiple cancers. In our previous study, we demonstrated that HDAC1/4-mediated silencing of microRNA-200b (miR-200b) enhances docetaxel (DTX)-resistance of human lung adenocarcinoma (LAD) cells. METHODS AND RESULTS: Herein, we probed the function of LncRNA MARCKSL1-2 (MARCKSL1-transcript variant 2, NR_052852.1) in DTX resistance of LAD cells. It was found that MARCKSL1-2 expression was markedly reduced in DTX-resistant LAD cells. Through gain- or loss- of function assays, colony formation assay, EdU assay, TUNEL assay, and flow cytometry analysis, we found that MARCKSL1-2 suppressed the growth and DTX resistance of both parental and DTX-resistant LAD cells. Moreover, we found that MARCKSL1-2 functioned in LAD through increasing miR-200b expression and repressing HDAC1. Mechanistically, MARCKSL1-2 recruited the suppressor of zeste 12 (SUZ12) to the promoter of histone deacetylase 1 (HDAC1) to strengthen histone H3 lysine 27 trimethylation (H3K27me3) of HDAC1 promoter, thereby reducing HDAC1 expression. MARCKSL1-2 up-regulated miR-200b by blocking the suppressive effect of HDAC1 on the histone acetylation modification at miR-200b promoter. Furthermore, in vivo analysis using mouse xenograft tumor model supported that overexpression of MARCKSL1-2 attenuated the DTX resistance in LAD tumors. CONCLUSIONS: We confirmed that MARCKSL1-2 alleviated DTX resistance in LAD cells by abolishing the inhibitory effect of HDAC1 on miR-200b via the recruitment of SUZ12. MARCKSL1-2 could be a promising target to improve the chemotherapy of LAD.

The overexpression of maspin increases the sensitivity of lung adenocarcinoma drug-resistant cells to docetaxel in vitro and in vivo.

BACKGROUND: In this study, we found that maspin affects the development of drug resistance in lung adenocarcinoma. Therefore, it is important to clarify the role and mechanism of mammary serine protease inhibitor (maspin) in the regulation of adenocarcinoma drug resistance in order to improve individualized clinical treatment protocols and drug resistance interventions. METHODS: Immunohistochemical was used to detect maspin expression in tissue chip samples of 75 patients diagnosed with lung adenocarcinoma and treated with a taxus chemotherapy regimen, and the correlation between maspin, clinicopathological factors, and prognosis was analyzed. The expression of maspin in a human lung adenocarcinoma docetaxel-resistant cell line, SPC-A1/DTX, and its parent cells were detected by reverse transcription polymerase chain reaction (RT-PCR) and western blot assay. MTT and flow cytometry were used to detect the effects of knockdown or overexpression of maspin on chemotherapy sensitivity and apoptosis in lung cancer cells. Tumor cells were also analyzed in vivo to determine their tumorigenic ability and susceptibility to docetaxel. RESULTS: Maspin is poorly expressed in lung adenocarcinoma tissue chips that have received a taxus chemotherapy regimen, and is also closely related to poor grading, late stage, lymph node metastasis, and poor prognosis. Maspin has a low expression in drug-resistant cells, and the expression level of maspin decreases significantly with increases in docetaxel concentration and over time. In drug-resistant cells, knockdown of maspin can significantly affect the sensitivity of drug-resistant cells to docetaxel. In the chemotherapy-sensitive strain SPC-A1, maspin was mainly located in the cell nucleus, while in the chemotherapy-resistant strain SPC-A1/DTX, maspin was mainly located in the cytoplasm. An in vivo nude mouse xenograft model showed that an overexpression of maspin significantly increased the inhibitory effect of docetaxel on tumor-bearing tissues and the apoptosis rate, and markedly reduced tumor weight, volume, and the Ki-67-positive rate. CONCLUSIONS: In vitro and in vivo experiments show that overexpression of maspin can increase the sensitivity of lung cancer drug-resistant cells to chemotherapy drugs, suggesting that the expression level of maspin could be used as a molecular marker to predict lung cancer drug resistance to docetaxel.

Aurora-a confers radioresistance in human hepatocellular carcinoma by activating NF-κB signaling pathway.

BACKGROUND: Radiotherapy failure is a significant clinical challenge due to the development of resistance in the course of treatment. Therefore, it is necessary to further study the radiation resistance mechanism of HCC. In our early study, we have showed that the expression of Aurora-A mRNA was upregulated in HCC tissue samples or cells, and Aurora-A promoted the malignant phenotype of HCC cells. However, the effect of Aurora-A on the development of HCC radioresistance is not well known. METHODS: In this study, colony formation assay, MTT assays, flow cytometry assays, RT-PCR assays, Western blot, and tumor xenografts experiments were used to identify Aurora-A promotes the radioresistance of HCC cells by decreasing IR-induced apoptosis in vitro and in vivo. Dual-luciferase reporter assay, MTT assays, flow cytometry assays, and Western blot assay were performed to show the interactions of Aurora-A and NF-κB. RESULTS: We established radioresistance HCC cell lines (HepG2-R) and found that Aurora-A was significantly upregulated in those radioresistant HCC cells in comparison with their parental HCC cells. Knockdown of Aurora-A increased radiosensitivity of radioresistant HCC cells both in vivo and in vitro by enhancing irradiation-induced apoptosis, while upregulation of Aurora-A decreased radiosensitivity by reducing irradiation-induced apoptosis of parental cells. In addition, we have showed that Aurora-A could promote the expression of nuclear IkappaB-alpha (IκBα) protein while enhancing the activity of NF-kappaB (κB), thereby promoted expression of NF-κB pathway downstream effectors, including proteins (Mcl-1, Bcl-2, PARP, and caspase-3), all of which are associated with apoptosis. CONCLUSIONS: Aurora-A reduces radiotherapy-induced apoptosis by activating NF-κB signaling, thereby contributing to HCC radioresistance. Our results provided the first evidence that Aurora-A was essential for radioresistance in HCC and targeting this molecular would be a potential strategy for radiosensitization in HCC.

S1PR1 promotes proliferation and inhibits apoptosis of esophageal squamous cell carcinoma through activating STAT3 pathway.

BACKGROUND: Esophageal squamous cell carcinoma (ESCC) is one of the most common cancers worldwide, which lacks effective biomarkers for prognosis. Therefore, it is urgent to explore new potential molecular markers to discriminate patients with poorer survival in ESCC. METHODS: Bioinformatics analysis, qRT-PCR, and western blot were applied to investigate S1PR1 expression. CCK-8 assay, colony formation assay, flow cytometry dual staining assay, and immunofluorescence were performed to examine cell proliferation ability and apoptosis rate. Mouse xenograft model of TE-13 cells was established to confirm the roles of S1PR1 in vivo. Gene set enrichment analysis (GSEA) was used to investigate the downstream signaling pathways related to S1PR1 functions. Co-IP was performed to verify the direct binding of S1PR1 and STAT3. Western blot was applied to determine the phosphorylation level of STAT3. Immunohistochemistry was conducted to identify protein expression of S1PR1 and p- STAT3 in tumor tissues. RESULTS: In the present study, we found that S1PR1 expression was higher in ESCC patients and was a potential biomarker for poor prognosis. Silencing S1PR1 expression inhibited proliferation, and increased apoptosis of ESCC cells, while overexpression of S1PR1 had opposite effects. Mechanistically, S1PR1 played the roles of promoting proliferation and attenuating apoptosis through directly activating p-STAT3. Furthermore, in vivo experiments verified this mechanism. CONCLUSION: Our findings indicated that S1PR1 enhanced proliferation and inhibited apoptosis of ESCC cells by activating STAT3 signaling pathway. S1PR1 may serve as a prognostic biomarker for clinical applications.

The effects of miR-429 on cell migration and invasion by targeting Slug in esophageal squamous cell carcinoma.

Increasing evidence indicates that microRNAs may play important roles in tumor development and may take part in different processes in different cancers. miR-429 is known as a cancer suppressor or oncogene that is dysregulated in different malignancies, including esophageal squamous cell carcinoma (ESCC). However, the effect of miR-429 in ESCC has not been fully explored. The purpose of this study was to investigate the functions of miR-429 in ESCC. qRT-PCR assays were performed to detect miR-429 expression in ESCC tissues and cell lines. To assess the effects of miR-429 on ESCC cells, wound healing and transwell assays were used. Luciferase reporter and western blot assays were employed to determine whether Slug is a major target of miR-429.Our results showed that the expression levels of miR-429 in ESCC tissues and cells were lower than in normal esophageal epithelial tissues and cells. Furthermore, overexpression of endogenous miR-429 inhibited the migration and invasion of ESCC cell lines. In addition, Luciferase reporter and western blot assays provided evidence that miR-429 can bind to the 3' untranslated regions of Slug to regulate its expression and that of downstream epithelial-to-mesenchymal transition (EMT) markers. We found that Slug serves as a major target of miR-429. miR-429 plays a vital role in ESCC progression and represents a new therapeutic target for ESCC.

FOX-A1 contributes to acquisition of chemoresistance in human lung adenocarcinoma via transactivation of SOX5.

BACKGROUND: Chemoresistance is a major obstacle for the effective treatment of lung adenocarcinoma (LAD). Forkhead box (FOX) proteins have been demonstrated to play critical roles in promoting epithelial-mesenchymal transition (EMT) and chemoresistance. However, whether FOX proteins contribute to the acquisition of EMT and chemoresistance in LAD remains largely unknown. METHODS: FOX-A1 expression was measured in LAD cells and tissues by qRT-PCR. The expression levels of EMT markers were detected by western blotting and immunofluorescence assay. The interaction between Sex determining region Y-box protein 5 (SOX5) and FOX-A1 was validated by chromatin immunoprecipitation sequence (ChIP-seq) and Chromatin immunoprecipitation (ChIP) assay. Kaplan-Meier analysis and multivariate Cox regression analysis were performed to analyze the significance of FOX-A1 and SOX5 expression in the prognosis of LAD patients. FINDINGS: FOX-A1 was upregulated in docetaxel-resistant LAD cells. High FOX-A1 expression was closely associated with a worse prognosis. Upregulation of FOX-A1 in LAD samples indicated short progression-free survival (PFS) and overall survival (OS). SOX5 is a new and direct target of FOX-A1 and was positively regulated by FOX-A1 in LAD cell lines. Knockdown of FOX-A1 or SOX5 reversed the chemoresistance of docetaxel-resistant LAD cells by suppressing cell proliferation, migration and EMT progress. INTERPRETATION: These data elucidated an original FOX-A1/SOX5 pathway that represents a promising therapeutic target for chemosensitizing LAD and provides predictive biomarkers for evaluating the efficacy of chemotherapies.

TFAP2C-Activated MALAT1 Modulates the Chemoresistance of Docetaxel-Resistant Lung Adenocarcinoma Cells.

Chemoresistance remains a great obstacle in effective lung adenocarcinoma (LUAD) treatment. Previously, we verified the role of microRNA-200b (miR-200b) in the formation of docetaxel (DTX)-resistant LUAD cells. This study aims to investigate the mechanism underlying the low level of miR-200b in DTX-resistant LUAD cells. The real-time reverse transcription (RT2) lncRNA PCR array system was applied to explore lncRNAs that potentially regulated miR-200b in DTX-resistant LUAD cells. Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) contributed to the low miR-200b level in DTX-resistant LUAD cells. Functional assays were conducted to determine the role of MALAT1 in regulating the growth and metastasis of parental and DTX-resistant LUAD cells. Investigation revealed the mechanism of the competing endogenous RNA (ceRNA) pathway. MALAT1 regulated miR-200b by acting as a ceRNA. MALAT1 modulated the sensitivity of LUAD cells to DTX. E2F transcription factor 3 (E2F3) and zinc-finger E-box binding homeobox 1 (ZEB1) were two targets of miR-200b and mediated the function of MALAT1 in DTX-resistant LUAD cells. Transcription factor AP-2 gamma (TFAP2C) and ZEB1 activated the MALAT1 transcription. In conclusion, TFAP2C-activated MALAT1 modulated the chemoresistance of LUAD cells by sponging miR-200b to upregulate E2F3 and ZEB1. Our findings may provide novel therapeutic targets and perspectives for LUAD treatment.

[Cyberknife stereotactic body radiotherapy for liver metastases from prostate cancer].

OBJECTIVE: To investigate the effectiveness and adverse effects of Cyberknife stereotactic body radiotherapy (SBRT) on liver metastases from PCa. METHODS: From June 2009 to September 2016, we treated 20 cases of PCa liver metastases by Cyberknife SBRT, at a total dose of 36 (30－50) Gy, on 1－3 liver metastatic lesions, for 3－5 times, with a prescription isodose line of 70－92%. We assessed the therapeutic effect according to the modified Response Evaluation Criteria in Solid Tumors (mRECIST), calculated the survival and disease-control rates using the Kaplan-Meier method, and analyzed the adverse events based on the National Cancer Institute Common Terminology Criteria for Adverse Events－Version 4.0 (CTCAE 4.0). RESULTS: Of all the cases treated, complete response (CR) was found in 8 (40.0%), partial response (PR) in 9 (45.0%), stable disease (SD) in 2 (10.0%), and progressive disease (PD) in 1 (5.0%), with a local control rate (CR+PR) of 85.0% and a disease-control rate (CR+PR+SD) of 95.0%. Among the 14 patients with elevated PSA, 10 (71.4%) showed a significant decrease after treatment. The median follow-up time was 17 months, the 1- and 2-year survival rates were 85.0% and 15.0%, respectively, and the median survival time of the 20 patients was 16.5 months (95% CI: 12.12－22.88). Cyberknife SBRT was well tolerated in all the patients, with only a few mild adverse events (mainly grades 1 and 2 but no 4 and 5) during the whole course of treatment. CONCLUSIONS: Cyberknife SBRT is safe and effective in the treatment of PCa liver metastases, with a high local control rate, and capable of reducing the PSA level and raising the long-term survival rate of the patients.

miRNA­885­3p inhibits docetaxel chemoresistance in lung adenocarcinoma by downregulating Aurora A.

Aurora A is a member of the mitotic serine/threonine kinase family. It is involved in key processes during mitosis and meiosis, and Aurora A upregulation is implicated in malignant transformation. In the present study, we revealed that Aurora A expression was significantly higher in docetaxel­resistant lung adenocarcinoma (LAD) cells than in parental cells. Higher levels of Aurora A expression were significantly correlated with higher chemoresistance and proliferation in LAD cells, while silencing Aurora A promoted caspase­3­dependent cell apoptosis by downregulating NF­κB and Bcl­2 and upregulating Bax expression. In addition, an increased proportion of cells in the G2/M phase and a decreased proportion of cells in the S phase were observed due to the suppression of Aurora A. Furthermore, we identified that microRNA­885­3p (miR­885­3p) could target Aurora A directly. There was significantly lower miR­885­3p expression in docetaxel­resistant LAD cells than in parental LAD cells. miR­885­3p could modulate the docetaxel response, cell proliferation and apoptosis in LAD cells in vitro. Moreover, we found that Aurora A overexpression or miR­885­3p inhibition was associated with more aggressive behaviour in LAD cells. Thus, miR­885­3p/Aurora A may be involved in the chemoresistance of LAD cells, and assessing miR­885­3p/Aurora A expression may be a potential method for indicating chemosensitivity to docetaxel­based chemotherapy.

The Role of Canonical Wnt Signaling in Regulating Radioresistance.

Radioresistance is a major obstacle in radiotherapy for cancer, and strategies are needed to overcome this problem. Currently, radiotherapy combined with targeted therapy such as inhibitors of phosphoinosotide 3-kinase/Akt and epidermal growth factor receptor signaling have become the focus of studies on radiosensitization. Apart from these two signaling pathways, which promote radioresistance, deregulation of Wnt signaling is also associated with the radioresistance of multiple cancers. Wnts, as important messengers in the tumor microenvironment, are involved in cancer progression mainly via canonical Wnt signaling. Their role in promoting DNA damage repair and inhibiting apoptosis facilitates cancer resistance to radiation. Thus, it seems reasonable to target Wnt signaling as a method for overcoming radioresistance. Many small-molecule inhibitors that target the Wnt signaling pathway have been identified and shown to promote radiosensitization. Therefore, a Wnt signaling inhibitor may help to overcome radioresistance in cancer therapy.

HDAC3-mediated silencing of miR-451 decreases chemosensitivity of patients with metastatic castration-resistant prostate cancer by targeting NEDD9.

BACKGROUND: Treatment of metastatic castration-resistant prostate cancer (mCRPC) with docetaxel often fails due to the emergence of chemoresistance. Thus, restoring chemosensitivity to docetaxel-based therapies remains a challenge in mCRPC treatment. METHODS: microRNA (miR)-451 expression was measured in docetaxel-treated prostate cancer cells and tumor tissues by quantitative reverse-transcription polymerase chain reaction . Cell-counting kit 8 assay was performed to determine docetaxel chemoresistance. Neural-precursor-cell-expressed developmentally downregulated protein 9 (NEDD9) was identified as a novel target of miR-451 by dual-luciferase reporter system. Chromatin immunoprecipitation and co-immunoprecipitation assay were performed to confirm that histone deacetylase 3 (HDAC3)/Sp1 (a highly evolutionarily conserved transcription factor) interacted with the Sp1 binding sites in miR-451 promoter. RESULTS: miR-451 was found to be silenced in docetaxel-treated prostate cancer cells and mCRPC tissues. Low miR-451 expression was closely associated with a high Gleason score, high Eastern Cooperative Oncology Group performance status score, visceral metastasis and poor prognosis. Low expression of miR-451 was significantly correlated with short progression-free survival (PFS) and overall survival (OS) according to Kaplan-Meier analysis, and miR-451 was determined to be an independent poor prognostic factor for PFS and OS in mCRPC patients by univariate and multivariate Cox regression analyses. NEDD9 was identified as a new and functional target of miR-451. Restoration of NEDD9 partially reversed the effects of miR-451 on enhancing chemosensitivity of prostate cancer cells. HDAC3 was confirmed to be involved in silencing of miR-451 expression in prostate cancer cells. CONCLUSIONS: The current data revealed a new HDAC3/Sp1/miR-451/NEDD9 signaling axis that regulates the chemosensitivity of prostate cancer cells and represents a novel therapeutic target for chemosensitizing mCRPC.

Wnt signaling induces radioresistance through upregulating HMGB1 in esophageal squamous cell carcinoma.

Although many articles have uncovered that Wnt signaling is involved in radioresistance, the mechanism is rarely reported. Here we generated two radioresistant cells rECA109 and rKyse150 from parental esophageal cancer cells ECA109 and Kyse150. We then found that Wnt signaling activity was higher in radioresistant cells and was further activated upon ionizing radiation (IR) exposure. In addition, radioresistant cells acquired epithelial-to-mesenchymal transition (EMT) properties and stem quality. Wnt signaling was then found to be involved in radioresistance by promoting DNA damage repair. In our present study, high-mobility group box 1 protein (HMGB1), a chromatin-associated protein, was firstly found to be transactivated by Wnt signaling and mediate Wnt-induced radioresistance. The role of HMGB1 in the regulation of DNA damage repair with the activation of DNA damage checkpoint response in response to IR was the main cause of HMGB1-induced radioresistance.

SNHG16/miR-140-5p axis promotes esophagus cancer cell proliferation, migration and EMT formation through regulating ZEB1.

Esophageal squamous cell carcinoma (ESCC) is one of the most aggressive malignancies. Long noncoding RNAs (lncRNAs) have been identified to be associated with many diseases including tumors, and involved in the regulation of a wide array of pathophysiological processes. Small nucleolar RNA host gene 16 (SNHG16), also known as noncoding RNA expressed in aggressive neuroblastoma, was newly identified as a potential oncogene in many cancers. However, its role in ESCC has not been investigated. In the current study, the level of SNHG16 in the ESCC tissues and cell lines was measured by quantitative real-time PCR (qRT-PCR). Then loss-of-function assays were performed to explore the biological effects of SNHG16 in ESCC cell. Based on the online database analysis tools, we uncovered that miR-140-5p could interact with SNHG16 and the level of miR-140-5p was inverse correlated with SNHG16 in ESCC specimens. Moreover, RIP, RNA pulldown system and dual luciferase reporter assay further provided evidence that SNHG16 directly targets miR-140-5p by binding with microRNA binding site harboring in the SNHG16 sequence. Furthermore, bioinformatics analysis revealed that ZEB1 is a target of miR-140-5p in ESCC. Collectively, our findings suggested that SNHG16 could act as an oncogenic lncRNA that promotes tumor progression through acting as an endogenous 'sponge' by competing with miR-140-5p, thereby regulating target ZEB1.

PU.1/microRNA-142-3p targets ATG5/ATG16L1 to inactivate autophagy and sensitize hepatocellular carcinoma cells to sorafenib.

Sorafenib is currently the only systemic agent approved for treatment of advanced hepatocellular carcinoma (HCC). However, intrinsic and acquired resistance to sorafenib remains a great challenge with respect to improving the prognoses of patients with HCC. The cyto-protective functions of autophagy have been suggested as a potential mechanism by which chemoresistance or targeted drug resistance occurs in tumour cells. In the present study, miR-142-3p was identified as a novel autophagy-regulating microRNA (miRNA) that plays a vital role in sorafenib resistance in HCC cells. Gain- and loss-of-function assays revealed that ectopic miR-142-3p upregulation sensitized HCC cells to sorafenib by reducing sorafenib-induced autophagy, enhancing sorafenib-induced apoptosis and inhibiting cell growth, whereas miR-142-3p inhibition exerted contrasting effects. Bioinformatics analysis and luciferase reporter and rescue assays showed that autophagy-related 5 (ATG5) and autophagy-related 16-like 1 (ATG16L1) are potential targets through which miR-142-3p regulates autophagy inhibition. Furthermore, we verified that PU.1 regulated the expression of miR-142-3p in conjunction with our cellular experiments and the related results in the literature. Our findings show that targeting the PU.1-miR-142-3p-ATG5/ATG16L1 axis may be a useful therapeutic strategy for preventing cyto-protective autophagy to overcome sorafenib resistance.

Downregulation of MiR-31 stimulates expression of LATS2 via the hippo pathway and promotes epithelial-mesenchymal transition in esophageal squamous cell carcinoma.

BACKGROUND: Dysregulation of miRNAs is associated with cancer development by coordinately suppressing abundant target genes. Emerging evidence indicates that miR-31 plays a dual role in tumorigenicity. However, whether miR-31 plays as an oncogene in esophageal squamous cell carcinoma (ESCC) and the potential target molecules are still unclear. MiR-31 role in ESCC was investigated and an association of the target molecules with EMT was identified in the progression of ESCC. METHODS: Western blot assays and qRT-PCR was performed to detect the protein and mRNA levels. We investigated the role of miR-31 in the regulation of LATS2 expression in ESCC cell lines via functional assays both in vivo and in vitro. The luciferase reporter assays was conducted to confirm LATS2 is a potential target of miR-31. Immunohistochemistry was used to measure LATS2 and TAZ expression in normal and ESCC tissue. RESULTS: LATS2 is a component of the Hippo tumor-suppressive signaling pathway. Frequent loss of heterozygosity of LATS2 has been reported in esophageal cancer. We analyzed the reciprocal expression regulation of miR-31 and LATS2 and demonstrated that LATS2 expression was elevated by down-regulation of miR-31 at the post-transcriptional level in ESCC. Moreover, miR-31 significantly suppressed the luciferase activity of mRNA combined with the LATS2 3'-UTR, a key molecule in the Hippo pathway. Then, LATS2 consequently promoted the translocation of TAZ, which was examined using immunohistochemistry. Silencing of miR-31 significantly inhibited the cell proliferation, induced apoptosis and decreased the ability of migration/invasion in vitro. LATS2 impedes ESCC cell proliferation and invasion by suppressing miR-31, as well as mice xenograft model in vivo. Meanwhile, the nuclear localization of LATS2 constrained the phosphorylation of TAZ. Then, the expression level of TAZ was notably heightened with a high risk of recurrence compared to that observed in the low-risk patients, as well as, the higher expression associated with a poor survival. CONCLUSIONS: Our study demonstrated that overexpression of miR-31 undertook an oncogenic role in ESCC by repressing expression of LATS2 via the Hippo Pathway and activating epithelial-mesenchymal transition. LATS2 and TAZ could be potential novel molecular markers for predicting the risk of recurrence and prognosis of ESCC.

Intensified Beclin-1 Mediated by Low Expression of Mir-30a-5p Promotes Chemoresistance in Human Small Cell Lung Cancer.

BACKGROUND/AIMS: Although small cell lung cancer (SCLC) is sensitive to initial chemotherapy, patients experience tumor recurrence and metastasis, leading to treatment failure. Autophagy as a protective pattern for cell survival in the harsh environment plays an important role in chemoresistance. However, the role of Beclin-1, a key regulator of autophagy in the drug-resistance of SCLC cells is still poorly understood. In the current study, we focused on the effect and regulation of Beclin-1 in chemoresistance of SCLC cells. METHODS: We analyzed the levels of Beclin-1 in etoposide/cisplatin (EP) -resistant and -sensitive cell lines, as well as the relationship between Beclin-1 and patients' chemosensitivity. The function of Beclin-1 in chemoresistant SCLC cells in vitro was measured by MTT, WB, colony formation and flow cytometric analysis. Further rescue experiment was performed after co-transfected with siBeclin-1 and miR-30a mimics or inhibitor. RESULTS: Beclin-1 was upregulated in drug-resistant cells and patients with lower sensitivity to etoposide/cisplatin therapy. Downregulated Beclin-1 attenuated drug sensitivity and colony formation ability of chemoresistant cells. Moreover, inhibition of Beclin-1 resulted in a dramatic decline of autophagy and increase of apoptosis in drug-resistant cells, accompanied by a remarkable reduction in S phase and a raise in G2/M phase of cell cycle. The transfection with miR-30a-5p mimics exhibited an opposite effect. In addition, inhibition of Beclin-1 could partly reverse the effect induced by miR-30a-5p suppression in drug-sensitive cells. CONCLUSION: Beclin-1 regulated by miR-30a-5p plays a notable role in the drug-resistance of SCLC. Inhibition of Beclin-1 by induction of miR-30a-5p may improve the therapeutic outcome via resensitizing the drug-resistant cells to chemotherapy in SCLC.

Cancer associated fibroblasts: An essential role in the tumor microenvironment.

Fibroblasts in the tumor stroma are well recognized as having an indispensable role in carcinogenesis, including in the initiation of epithelial tumor formation. The association between cancer cells and fibroblasts has been highlighted in several previous studies. Regulation factors released from cancer-associated fibroblasts (CAFs) into the tumor microenvironment have essential roles, including the support of tumor growth, angiogenesis, metastasis and therapy resistance. A mutual interaction between tumor-induced fibroblast activation, and fibroblast-induced tumor proliferation and metastasis occurs, thus CAFs act as tumor supporters. Previous studies have reported that by developing fibroblast-targeting drugs, it may be possible to interrupt the interaction between fibroblasts and the tumor, thus resulting in the suppression of tumor growth, and metastasis. The present review focused on the reciprocal feedback loop between fibroblasts and cancer cells, and evaluated the potential application of anti-CAF agents in the treatment of cancer.

MiRNAs and E2F3: a complex network of reciprocal regulations in human cancers.

E2F transcription factor 3 (E2F3) is oncogenic in tumorigenesis. Alterations in E2F3 functions correspond with poor prognosis in various cancers, underscoring their status for the clinical cancer phenotype. Latest reports discovered intricate networks between microRNAs (miRNAs) and E2F3 in regulating the balance of these events, including proliferation, apoptosis, metastasis, as well as drug resistance. miRNAs are non-coding small RNAs which negatively regulate gene expressions post-transcriptionally mainly through 3'-UTR binding of target mRNAs. Increasing evidence shows that E2F3 can be activated/inhibited by numerous miRNAs whose dysregulation has been implicated in malignancy. In turn, miRNAs themselves can be transcriptionally regulated by E2F3, thus forming a negative feedback loop. These findings add a new challenging layer of complexity to E2F3 network. Current understanding of the reciprocal link between E2F3 and miRNAs in human cancers were summarized, which could help to develop potential therapeutic strategies.