LncRNA HOST2 promotes NSUN2-mediated breast cancer progression via interaction with ELAVL1.

Breast cancer (BC) is the most prevalent malignant tumor in women worldwide with high morbidity and mortality. NSUN2, a crucial RNA methyltransferase, plays a pivotal role in regulating the proliferation and metastasis of tumor cells. Our study demonstrated that NSUN2 is upregulated in BC tissues and cell lines, and its high expression is associated with a poor prognosis in BC patients. Knockout of NSUN2 exerted inhibitory effects on the proliferation and migration of BC cells in vitro and in vivo. Mechanistic investigations revealed that the RNA-binding protein ELAVL1 can bind to NSUN2 mRNA and increase its stability. Additionally, we identified HOST2, a long non-coding RNA, as a key player in blocking the ubiquitin-dependent proteasomal degradation of ELAVL1, thereby influencing the stability of NSUN2 mRNA. In conclusion, this study revealed for the first time that HOST2 maintains NSUN2 mRNA stability by blocking ubiquitin-dependent degradation of ELAVL1, which in turn affects BC progression. HOST2/ELAVL1/NSUN2 oncogenic cascade has the potential to be a novel therapeutic target for BC.

E2F1-mediated ectopic expression of PP1A promotes breast cancer progression via activation of YAP1.

Hormone receptor-positive breast cancer is the most common subtype of breast cancer. The protein phosphatase PP1A gene is described as an oncogene in several tumor types; however, the biological function of PP1A in hormone receptor-positive breast cancer remains unclear. The Cancer Genome Atlas data indicates PP1A expression is upregulated in hormone receptor-positive breast cancer tissues than in normal breast tissues. We explored the biological function of PP1A in hormone receptor-positive breast cancer using MTT assays, colony formation assays, and a xenograft mouse model. The results indicated that PP1A promoted hormone receptor-positive breast cancer proliferation, both in vitro and in vivo. Mechanistically, LINC02754 recruited the binding of the transcription factor E2F1 to the PP1A promotor, thereby increasing PP1A expression. The PP1A then interacted with and dephosphorylated YAP1, resulting in YAP1 activation. The dephosphorylated YAP1 moved to the nucleus and increased the expression of the downstream oncogene CTGF, promoting hormone receptor-positive breast cancer progression. Our findings reveal the function of the LINC02754/E2F1/PP1A/YAP1 axis in hormone receptor-positive breast cancer and provide new insight into hormone receptor-positive breast cancer progression.

Tumor-Derived circRNAs as Circulating Biomarkers for Breast Cancer.

Early diagnosis is the key to improving the prognosis of breast cancer (BC) patients; however, there are currently no circulating biomarkers that demonstrate good sensitivity and specificity. This study applied circular RNA (circRNA) microarray analysis, screening, and verification in BC plasma samples to identify three tumor-derived differentially expressed circRNAs: hsa_circ_0000091, hsa_circ_0067772, and hsa_circ_0000512. We constructed a diagnostic model using logistic regression analysis in the training set and established an optimal diagnostic model based on the three circRNAs, which showed sensitivity, specificity, and area under the curve (AUC) values of .971, .902, and .974, respectively. We then verified the diagnostic model in the test set which showed satisfactory stability for BC diagnosis. Additionally, the expression of hsa_circ_0000091 in plasma correlated with axillary lymph node (ALN) metastasis, TNM stage, and prognosis of BC patients. Furthermore, hsa_circ_0000091 combined with ultrasound showed predictive ability for ALN metastasis, with an AUC of .808. These findings suggested that the three identified circRNAs can be used as circulating biomarkers for BC diagnosis, with hsa_circ_0000091 potentially representing a prognostic biomarker for BC and novel approach for predicting ALN metastasis.

MIR22HG inhibits breast cancer progression by stabilizing LATS2 tumor suppressor.

The long noncoding RNA called MIR22 host gene (MIR22HG) was previously identified as a tumor suppressor in several cancers. However, the biological function of MIR22HG in breast cancer remains unknown. In this study, we aimed to determine the function and molecular mechanism of MIR22HG in breast cancer progression using transcriptomics and biotechnological techniques. Our results showed that MIR22HG expression was lower in the cancerous tissues than in the paired adjacent normal breast tissues. Additionally, MIR22HG was found to be mainly located in the cytoplasm and acted as a miR-629-5p sponge. Notably, MIR22HG stabilized the expression of large tumor suppressor 2 (LATS2), which promoted the LATS2-dependent phosphorylation of YAP1 and suppressed the expression of its downstream target oncogenes, thereby inhibiting the proliferation and migration of breast cancer cells. Therefore, our findings reveal the MIR22HG-dependent inhibition of breast cancer cell proliferation and migration via the miR-629-5p/LATS2 pathway, providing new insights and identifying novel therapeutic targets for breast cancer treatment.

miR-497 inhibits proliferation and invasion in triple-negative breast cancer cells via YAP1.

MicroRNA (miR)-497 has been reported as a tumor suppressor in various cancer types. Nonetheless, the regulation of triple-negative breast cancer (TNBC) by miR-497 remains poorly understood. The present study aimed to investigate the potential function and mechanism of miR-497 in TNBC. A total of 36 TNBC and matched non-cancerous tissue samples were collected for analysis. Reverse transcription-quantitative PCR was performed to detect the miR-497 levels in TNBC tissue. The association between miR-497 expression, clinical characteristics and survival was then analyzed. To investigate the role of miR-497 in TNBC, MTT, colony formation, Transwell invasion, cell cycle and cell apoptosis assays were conducted following transfection of miR-497 mimics into the MDA-MB-231 and MDA-MB-468 cell lines. Luciferase reporter assays and western blot analysis were used to confirm the regulation of a putative target of miR-497. The results indicated that the expression of miR-497 was downregulated in the TNBC specimens. Further analysis demonstrated that the expression of miR-497 was downregulated in patients with advanced TNBC stages and that low miR-497 was associated with poor prognosis in patients with TNBC. Transfection of miR-497 mimics inhibited TNBC cell proliferation and increased cell apoptosis in MDA-MB-231 and MDA-MB-468 cells. Moreover, cell migration was inhibited following overexpression of miR-497, which also led to the arrest of the breast cancer cells in the G0/G1 phase of the cell cycle. Yes-associated protein 1 (YAP1), a critical molecule in the Hippo pathway, was identified as a target of miR-497. Notably, the protein and mRNA expression levels of YAP1 in MDA-MB-231 and MDA-MB-468 cells were downregulated following overexpression of miR-497. Overall, the findings of the present study indicated that miR-497 inhibited TNBC cell proliferation and migration and induced cell apoptosis by negatively regulating YAP1 expression. Thus, targeting miR-497 may represent a potential strategy for the treatment of TNBC.

Hsa_circ_0053063 inhibits breast cancer cell proliferation via hsa_circ_0053063/hsa-miR-330-3p/PDCD4 axis.

Breast cancer (BC) is one of the most common malignancies and its mortality is the highest among females. Circular RNAs (circRNAs), a novel group of non-coding RNAs, play an important regulatory role in angiogenesis and cancer progression. Hsa_circ_0053063 is a circRNA generated from several exons of HADHA. The potential role of hsa_circ_0053063 in BC remains unknown and needs to be explored. Hsa_circ_0053063 was mainly located in the cytoplasm and activated in BC tissues and cell lines. The binding position between hsa_circ_0053063 and miR-330-3p was confirmed by luciferase reporter assay. Moreover, hsa_circ_0053063 inhibited cell viability, proliferation, and progression of BC through the negative regulation of miR-330-3p. Programmed cell death 4 (PDCD4) is a direct target of miR-330-3p. Besides, the over-expression of miR-330-3p promoted cell progression by directly targeting and regulating PDCD4. Mechanistically, hsa_circ_0053063 activated PDCD4 by targeting miR-330-3p to inhibit BC progression. In conclusion, hsa_circ_0053063 inhibits breast cancer cell proliferation via hsa_circ_0053063/hsa-miR-330-3p/PDCD4 axis, which may provide a new therapeutic target for BC patients.

Hsa_circ_0005273 facilitates breast cancer tumorigenesis by regulating YAP1-hippo signaling pathway.

BACKGROUND: Circular RNAs (circRNAs), a novel class of endogenous RNAs, have shown to participate in the development of breast cancer (BC). Hsa_circ_0005273 is a circRNA generated from several exons of PTK2. However, the potential functional role of hsa_circ_0005273 in BC remains largely unknown. Here we aim to evaluate the role of hsa_circ_0005273 in BC. METHODS: The expression level of hsa_circ_0005273 and miR-200a-3p were examined by RT-qPCR in BC tissues and cell lines. The effect of knocking down hsa_circ_0005273 in BC cell lines were evaluated by examinations of cell proliferation, migration and cell cycle. In addition, xenografts experiment in nude mice were performed to evaluate the effect of hsa_circ_0005273 in BC. RNA immunoprecipitation assay, RNA probe pull-down assay, luciferase reporter assay and fluorescence in situ hybridization were conducted to confirm the relationship between hsa_circ_0005273, miR-200a-3p and YAP1. RESULTS: Hsa_circ_0005273 is over-expressed in BC tissues and cell lines, whereas miR-200a-3p expression is repressed. Depletion of hsa_circ_0005273 inhibited the progression of BC cells in vitro and in vivo, while overexpression of hsa_circ_0005273 exhibited the opposite effect. Importantly, hsa_circ_0005273 upregulated YAP1 expression and inactivated Hippo pathway via sponging miR-200a-3p to promote BC progression. CONCLUSIONS: Hsa_circ_0005273 regulates the miR-200a-3p/YAP1 axis and inactivates Hippo signaling pathway to promote BC progression, which may become a potential biomarker and therapeutic target.

Mir-30b-5p Promotes Proliferation, Migration, and Invasion of Breast Cancer Cells via Targeting ASPP2.

Triple-negative breast cancer (TNBC) is the most aggressive subtypes of breast cancer, which has few effective targeted therapies. Various sources of evidence confirm that microRNAs (miRNAs) contribute to the progression and metastasis of human breast cancer. However, the molecular mechanisms underlying the changes in miRNAs expression and the regulation of miRNAs functions have not been well clarified. In this study, we found that the expression of miR-30b-5p was upregulated in breast cancer tissues and breast cancer cell lines, compared to paracancer tissues and normal breast cell lines. Moreover, induced overexpression of miR-30b-5p promoted the MDA-MB-231 and HCC 1937 cell growth, migration, and invasion and reduced the cellular apoptosis. Further studies confirmed that miR-30b-5p could directly target ASPP2 and then activate the AKT signaling pathway. Our results suggested that miR-30b-5p could act as a tumor promoter in TNBC. The newly identified miR-30b-5p/ASPP2/AKT axis represents a novel therapeutic strategy for treating TNBC.

Hsa_circ_0091074 regulates TAZ expression via microRNA­1297 in triple negative breast cancer cells.

Triple negative breast cancer (TNBC) has the highest recurrence, metastasis and mortality rate of all breast cancer subtypes, due to its typically more aggressive characteristics and lack of effective targeted treatment options. The Hippo pathway is a signaling cascade composed of a group of conserved kinases, which serves an important role in almost all cancer types. Both circular RNAs (circRNAs) and microRNAs (miRNAs) are types of non­coding RNAs, which influence cancer progression. CircRNAs have been demonstrated to serve as miRNA 'sponges', binding to miRNAs to inhibit their function. In the present study, it was revealed that circular RNA hsa_circ_0091074 binds miR­1297, and that there is an inverse association between the expression levels of the two non­coding RNAs in breast cells, indicating that hsa_circ_0091074 may serve as an endogenous 'sponge' for miR­1297. Subsequently, the potential function and mechanism underlying the involvement of miR­1297 in breast cancer was investigated via MTT, colony formation, wound healing and cell cycle assays. Increased miR­1297 expression resulted in a decrease in the protein levels of critical Hippo pathway transcriptional mediator Transcriptional coactivator with PDZ­binding motif (TAZ), which is a putative target of miR­1297. This was confirmed using dual­luciferase reporter assays, which revealed that miR­1297 targets TAZ by binding its 3'­untranslated region (3'UTR). The current results indicate that miR­1297 serves as a suppressor of breast cancer cell proliferation and invasiveness, and that this can be partially reversed by hsa_circ_0091074, suggesting that the hsa_circ_0091074/miR­1297/TAZ/TEAD4 axis may represent a potential therapeutic target for triple negative breast cancer in the future.

Long noncoding RNA HOST2, working as a competitive endogenous RNA, promotes STAT3-mediated cell proliferation and migration via decoying of let-7b in triple-negative breast cancer.

BACKGROUND: Human ovarian cancer specific transcript 2 (HOST2) is a long non-coding RNA (lncRNA) reported to be specifically high expressed in human ovarian cancer. However, the mechanism that how HOST2 regulates triple negative breast cancer (TNBC) need to be explored. METHODS: In this study, expression of HOST2 was determined in 40 TNBC patients and matched non-cancerous tissues by qRT-PCR and in situ hybridization (ISH) assay. The biological functions of HOST2 was measured by losing features. The effect of HOST2 on viability, proliferation and migration was evaluated by MTT, colony formation assay, EDU analysis, transwell invasion assay and nude mouse xenograft model. Fluorescence in situ hybridization (FISH), Luciferase report assay, RNA immunoprecipitation (RIP) assay and Western blot were fulfilled to measure molecular mechanisms. RESULTS: The results showed that HOST2 was up-regulated in BC tissues and cell lines. Clinical outcome analysis demonstrated that high expression of HOST2 was associated with poor prognosis of TNBC patients. Functional experiments illustrated that knockdown of HOST2 significantly suppressed TNBC cell proliferation and migration. Western blot assays, qRT-PCR assays, RIP assays and luciferase reporter assays revealed that HOST2 regulated STAT3 via crosstalk with let-7b. Depression of HOST2 suppressed STAT3-mediated proliferation and migration in TNBC cells. HOST2 could function as a decoy of let-7b to depress expression of STAT3. CONCLUSIONS: HOST2 could function as a oncogene and promoted STAT3-mediated proliferation and migration through acting as a competing endogenous RNA, which might act as a potential biomarker for TNBC patients.

MicroRNA­424 serves an anti­oncogenic role by targeting cyclin­dependent kinase 1 in breast cancer cells.

The aim of the present study was to define the function of microRNA­424­5p (miR­424) in breast cancer cells. The present study investigated the level and the potential function of miR­424 in breast cancer by reverse transcription­quantitative polymerase chain reaction assays. miR­424 expression was decreased in the majority of human breast cancer specimens and cell lines used in the present study. The MTT assay, plate colony formation assay and flow cytometry analyses were used to characterize the function of miR­424 in two types of breast cancer cell lines. Upregulation of miR­424 inhibited cellular proliferation and regulated the cell cycle by arresting cells in the G2/M cell phase. The dual­luciferase reporter assay was used to confirm the direct association between miR­424 and cyclin­dependent kinase 1 (CDK1). Silencing of CDK1 expression by CDK1 short interfering RNA also significantly suppressed cell proliferation and arrested cells in the G2/M cell phase. The results of the present study indicated that miR­424 can suppress cell proliferation and arrest cells in G2/M cell phase by negatively regulating CDK1 mRNA in human breast cancer, possibly through the Hippo pathway and the extracellular signal­regulated kinase pathway. The results of the present study provided novel evidence for the role of miR­424 in breast cancer.

MicroRNA-301b promotes cell proliferation and apoptosis resistance in triple-negative breast cancer by targeting CYLD.

Aberrant expression of microRNAs (miRNAs) plays important roles in carcinogenesis and tumor progression. However, the expression and biological role of miR-301b in triple-negative breast cancer (TNBC) remains unclear. Here we aimed to evaluate the roles and mechanisms of miR-301b in TNBC cells. miR-301b expression was assessed in TNBC specimens and cell lines by quantitative Real-Time PCR (qRT-PCR). TNBC cells were transfected with miR-301b mimics, inhibitors or Cylindromatosis (CYLD) small interfering RNA (siRNA) using Lipofectamine 2000. The functional roles of miR-301b were determined by cell proliferation, colony formation, and apoptosis assays. Western blots and qRT-PCR were used to measure the expression of mRNAs and proteins in the cells. We found that miR-301b was upregulated in TNBC specimens and cell lines. Overexpression of miR-301b promoted cell proliferation in TNBC cells, while inhibited the apoptosis induced by 5-FU. CYLD was downregulated by miR-301b at both mRNA and protein levels in TNBC cells. Dual-luciferase report assay confirmed that miR-301b downregulated CYLD by direct interaction with the 3'-untranslated region(3'-UTR) of CYLD mRNA. NF-κB activation was mechanistically associated with miR-301b-mediated downregulation of CYLD. However, inhibition of miR-301b reversed all the effects of miR-301b. In conclusion, miR-301b plays an oncogenic role in TNBC possibly by downregulating CYLD and subsequently activating NF-κB p65, and this may provide a novel therapeutic approach for TNBC. [BMB Reports 2018; 51(11): 602-607].

WBP2 Downregulation Inhibits Proliferation by Blocking YAP Transcription and the EGFR/PI3K/Akt Signaling Pathway in Triple Negative Breast Cancer.

BACKGROUND/AIMS: Dysregulated expression of WW domain-binding protein 2 (WBP2) is associated with poor prognosis in ER+ breast cancer patients. However, its role in triple negative breast cancer (TNBC) has not been previously assessed. Therefore, we aimed to elucidate the functional mechanism of WBP2 in TNBC cells. METHODS: qRT-PCR, western blotting, and immunohistochemical staining were used to evaluate WBP2 expression in TNBC patient tumors and cell lines. HCC1937 and MDA-MB-231 cells transiently transfected with WBP2 small interfering RNA (siRNA), miR-613 mimics, or miR-613 inhibitors were subject to assays for cell viability, apoptosis and cell cycle distribution. Co-immunoprecipitation, western blotting or qRT-PCR were employed to monitor changes in signaling pathway-related genes and proteins. Luciferase assays were performed to assess whether WBP2 is a direct target of miR-613. The effect of miR-613 on tumor growth was assessed in vivo using mouse xenograft models. RESULTS: The expression of WBP2 was upregulated in TNBC tissues and cells. Expression of WBP2 was significantly correlated with Ki67 in TNBC patients. Knockdown of WBP2 inhibited cellular proliferation, promoted apoptosis, and induced cell cycle arrest of TNBC cells. miR-613 directly bound to the 3'-untranslated region (3'-UTR) of WBP2 and regulated the expression of WBP2. Moreover, miR-613 reduced the expression of WBP2 and suppressed tumor growth of TNBC cells in vivo. Knockdown of WBP2 inhibited YAP transcription and the EGFR/PI3K/Akt signaling pathway in TNBC cells, and these effects were reversed by inhibition of miR-613. CONCLUSION: WBP2 overexpression is associated with the poor prognosis of TNBC patients and the miR-613-WBP2 axis represses TNBC cell growth by inactivating YAP-mediated gene expression and the EGFR/PI3K/Akt signaling pathway.

Silencing of ASPP2 promotes the proliferation, migration and invasion of triple-negative breast cancer cells via the PI3K/AKT pathway.

Apoptosis-stimulating p53 protein 2 (ASPP2) is an apoptosis inducer that acts via binding with p53 and then enhancing the transcriptional activities toward pro­apoptosis genes. ASPP2 has recently been reported to serve a major role in p53­independent pathways. Triple­negative breast cancer (TNBC) is a type of breast cancer that is more aggressive and highly lethal when p53 is mutated. In the present study, the mRNA level of ASPP2 was found to be suppressed in breast tumors compared with that in adjacent normal breast tissues, and the expression of ASPP2 was also decreased in a series of breast cancer cell lines compared with that in MCF­10A normal breast cells. Downregulation of ASPP2 by specific small interfering RNA (siRNA) transfection was able to promote cell growth, reduce cell apoptosis, and contribute to cell migration and invasion. Furthermore, downregulation of ASPP2 promoted cell epithelial­mesenchymal transition (EMT) in MDA­MB­231 and HCC­1937 TNBC cells. Furthermore, it was found that when ASPP2 siRNA was transfected into MDA­MB­231 and HCC­1937 cells, the expression of phosphoinositide­3­kinase regulatory subunit 1 (p85α) decreased and phosphorylation of protein kinase B (AKT) increased, which are key molecular regulators in the phosphatidylinositol 3-kinase (PI3K)/AKT pathway. In conclusion, the present data indicated that ASPP2 had a crucial influence on the proliferation and metastasis in TNBC, and that the functional mechanism may be p53­independent to a great extent. ASPP2 and its link with the PI3K/AKT pathway deserve further investigation and may provide novel insights into therapeutic targets for TNBC.

MicroRNA-340 inhibits invasion and metastasis by downregulating ROCK1 in breast cancer cells.

MicroRNAs (miRNAs/miRs) are 19-25 nucleotide-long, non-coding RNAs that regulate the expression of target genes at the post-transcriptional level. In the present study, the role of miR-340 in breast cancer (BC) was investigated. The overexpression of miR-340 significantly inhibited the proliferation, migration and invasion of human breast MDA-MB-231 cancer cells in vitro. The Rho-associated, coiled-coil containing protein kinase 1 (ROCK1) gene was identified as a target of miR-340; its expression was downregulated by overexpression of miR-340 by binding to its 3'-untranslated region. The short interfering RNA-mediated silencing of ROCK1 was also performed, which phenocopied the effects of miR-340 overexpression. An inhibitor of miR-340 was used to suppress miR-340 expression, which led to increased expression of ROCK1, thus improving the proliferation, migration and invasion of MDA-MB-231 cells. Data from the present study suggest that miR-340 inhibits MDA-MB-231 cell growth and its downregulation may lead to the progression and metastasis of BC. Thus, miR340 may act as a tumor-suppressor agent that could serve a key role in the diagnosis and therapy of BC.

Inhibition of RAB1A suppresses epithelial-mesenchymal transition and proliferation of triple-negative breast cancer cells.

RAB1A acts as an oncogene in various cancers, and emerging evidence has verified that RAB1A is an mTORC1 activator in hepatocellular and colorectal cancer, but the role of RAB1A in breast cancer remains unclear. In this investigation, RAB1A siRNA was successfully transfected in MDA-MB-231 and BT-549 human triple-negative breast cancer cells, and verified by real­time quantitative polymerase chain reaction and western blotting. Then, MTT cell proliferation, colony formation, cell invasion and wound healing assays were performed to characterize the function of RAB1A in the breast cancer cell lines. Downregulation of RAB1A inhibited cellular growth, cell migration, cell invasion and cell epithelial-mesenchymal transition. Furthermore, compared with NC siRNA transfected cells, RAB1A siRNA transfected breast cancer cells inhibited the phosphorylation of S6K1, the effector molecular of mTORC1. Collectively, our data suggested that RAB1A acts as an oncogene by regulating cellular proliferation, growth, invasion and metastasis via activation of mTORC1 pathway in triple-negative breast cancer.

MicroRNA-7 inhibits proliferation, migration and invasion of thyroid papillary cancer cells via targeting CKS2.

The purpose of this study was to examine the expression levels of microRNA-7 (miR-7) in human thyroid papillary cancer and its potential role in disease pathogenesis. The expression levels of different miRNAs were detected by miRNA-microarray analysis in ten thyroid papillary cancer specimens and adjacent normal thyroid cancer tissues. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was conducted to determine the expression level of miR-7 in both thyroid papillary cancer tissues and cell lines. To characterize the function of miR-7, MTT assay, colony formation assay, cell migration assay, cell invasion assay, cell cycle assay and cell apoptosis assay were used. Luciferase reporter assays were performed to validate the regulation of a putative target of miR-7, in corroboration with western blot assays. Finally, MTT assay, cell migration assay, cell invasion assay and cell cycle assay were used to indicate the roles of endogenous cyclin-dependent kinase regulatory subunit 2 (CKS2) in thyroid papillary cancer cells. Our results reveal that miR-7 expression was relatively decreased in thyroid papillary cancer specimens and cell lines compared with adjacent normal tissues and normal thyroid cells. Overexpression of miR-7 inhibited cellular proliferation, suppressed cellular migration and invasion, caused a G0/G1 arrest in vitro. Dual-luciferase reporter assays showed that miR-7 binds the 3'-untranslated region (3'-UTR) of CKS2. Western blotting showed that miR-7 negatively regulated CKS2 protein expression. As its downstream genes, cyclin B1 (G2/mitotic-specific cyclin-B1) and cdk1 (cyclin-dependent kinase 1) were regulated by miR-7 and CKS2 axis. Knockdown of CKS2 expression by CKS2-siRNA in TPC1 and K1 cells also significantly suppressed cell proliferation, cell migration and invasion. Our results demonstrated for the first time that miR-7 functions as a tumor suppressor and plays an important role in inhibiting the tumorigenesis through targeting CKS2 in thyroid papillary cancer cells.

miR-135b, upregulated in breast cancer, promotes cell growth and disrupts the cell cycle by regulating LATS2.

Dysregulation of microRNAs (miRNAs) plays a critical role in cancer progression. They can act as either oncogenes or tumor suppressor genes in human cancer. The purpose of this study was to investigate the crucial role of miR-135b in breast cancer and to validate whether miR-135b could regulate proliferation of breast cancer cells by effecting specific targets in the Hippo pathway. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was carried out to quantify the expression levels of miR-135b in both breast cancer tissues and cell lines. To characterize the function of miR-135b, MTT assays, colony formation assays, cell migration assays, cell invasion assays, and cell cycle assays were used. Luciferase reporter assays were performed to validate the regulation of a putative target of miR-135b, in corroboration with western blot assays. Finally, we verified the changes of cellular function after transfection of LATS2-siRNA. Our experiments indicate that expression of miR-135b was commonly upregulated in breast cancer specimens and breast cancer cells when compared with that in adjacent normal tissues and non-malignant breast epithelial cells. Enforced expression of miR-135b can regulate cellular proliferation, migration and invasion as well as disrupt the cell cycle of breast cancer cells. Luciferase assays revealed that miR-135b directly bound to the 3'-untranslated region (3'-UTR) of LATS2 (large tumor suppressor kinase 2), a critical gene in the Hippo pathway. Western blot analysis verified that miR-135b regulated the expression of LATS2 at protein levels. Further study demonstrated that the downstream gene of LATS2 in the Hippo pathway, such as cyclin-dependent kinase 2 (CDK2) and Phospho-Yes-associated protein (p-YAP), can also be regulated by miR-135b and LATS2 axis. Knockdown of endogenous LATS2 can mimic the result of miR-135b up-regulation in breast cancer. Taken together, our findings reveal that the miR-135b and LATS2 axis may be a potential therapeutic target for breast cancer in the future.

Inhibition of FOXO1 by small interfering RNA enhances proliferation and inhibits apoptosis of papillary thyroid carcinoma cells via Akt/FOXO1/Bim pathway.

Forkhead box protein O1 (FOXO1) is a multifunctional transcription factor of the forkhead family. It may function as a tumor suppressor through its ability to regulate cellular events, including cell proliferation, apoptosis, and cell cycle control. As reported, FOXO1 is downregulated in papillary thyroid carcinoma (PTC). However, the function of FOXO1 in human PTC remains unclear. In this study, we investigated the function and underlying regulatory mechanisms of FOXO1 in PTC cells. PTC cell lines K1 and TPC1 were transiently transfected with FOXO1 small interfering RNA (siRNA) and negative control RNA. Successful transfection was confirmed by RT-qPCR and Western blot analysis. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cell proliferation assays, colony formation assays, apoptosis, and cell cycle assays were used to explore the potential function of FOXO1 in the PTC cell lines. We found that downregulation of FOXO1 promoted cellular proliferation, enhanced clonogenesis, and inhibited cellular apoptosis. However, the cell cycle was not markedly affected by FOXO1 siRNA. Furthermore, Bim, a downstream target of the Akt/FOXO1 signaling pathway, was downregulated at both mRNA and protein levels in cells transfected with FOXO1 siRNA. Collectively, these results indicate that FOXO1 may play an important role in inhibiting PTC development by regulating cellular proliferation, growth, and apoptosis. FOXO1 expression is a potentially useful biomarker for human PTC. Moreover, tumorigenesis of PTC may be associated with repression of the Akt/FOXO1/Bim signaling pathway.