Tumor Suppressor In Human Cancers Research Articles

MiR-320d suppresses the progression of breast cancer via lncRNA HNF1A-AS1 regulation and SOX4 inhibition.

MicroRNA-320d (miR-320d) is a novel cancer-related miRNA and functions as a tumor suppressor in human cancers. However, the expression pattern and function of miR-320d in breast cancer remain largely unknown. In the present study, we found that the expression level of miR-320d in breast cancer tissues and cells was significantly lower than in non-tumor tissues and MCF-10A cells. Decreased miR-320d was associated with poor overall survival in patients with breast cancer. Overexpression of miR-320d inhibited proliferation, migration, and invasion and promoted apoptosis of breast cancer cells. In addition, the long non-coding RNA, HNF1A antisense RNA 1 (HNF1A-AS1) was up-regulated in both breast cancer tissues and cell lines. HNF1A-AS1 suppressed the expression and function of miR-320d. Moreover, SRY-related HMG-box 4 (SOX4) was speculated and confirmed as a target of miR-320d. We also demonstrated that HNF1A-AS1 may function as a sponge competitive endogenous RNA for miR-320d, and thus regulate the expression of SOX4. Taken together, our study has identified a novel signaling pathway through which miR-320d exerts its anti-carcinogenic roles and suggested that the HNF1A-AS1/miR-320d/SOX4 may be a potential target for the therapy of breast cancer.

MicroRNA-381 inhibits cell proliferation and invasion in endometrial carcinoma by targeting the IGF-1R.

Endometrial carcinoma (EC) is the sixth most common type of malignant tumor occurring in females. MicroRNAs (miRNAs) serve as oncogenes or tumor suppressors in human cancer and play important roles in tumorigenesis, and tumor development by regulating various processes. Thus, further investigation into miRNAs involved in EC formation and progression may aid in developing effective therapeutic strategies for patients with this disease. miRNA‑381 (miR‑381) is aberrantly expressed in multiple types of human cancer. However, the expression pattern, biological roles and underlying mechanisms of miR‑381 in EC are poorly understood. In the present study, the results showed that miR‑381 was downregulated in EC tissues and cell lines. Decreased miR‑381 expression correlated with the International Federation of Gynecology and Obstetrics stage, lymph nodes metastasis and myometrial invasion of EC. The ectopic expression of miR‑381 significantly inhibited the proliferation and invasion of EC cells. Through a series of experiments, the insulin‑like growth factor receptor 1 (IGF‑1R) was identified as a novel direct target of miR‑381 in EC. Furthermore, IGF‑1R was highly expressed in EC tissues and inversely correlated with miR‑381 levels. IGF‑1R overexpression partially abrogated the tumor‑suppressive effects of miR‑381 on the proliferation and invasion of EC cells. miR‑381 targeted IGF‑1R to inactivate the protein kinase B (AKT) and extracellular signal‑regulated kinase (ERK) signaling pathways in EC. These results suggest that miR‑381 acts as a tumor suppressor in EC by directly targeting IGF‑1R, and indirectly regulating the AKT and ERK signaling pathways. Thus, miR‑381 should be investigated as a prognostic biomarker and novel therapeutic target for the treatment of patients with EC.

Long noncoding RNA TSLNC8 is a tumor suppressor that inactivates the interleukin-6/STAT3 signaling pathway.

TSLNC8 is a promising prognostic predictor for patients with HCC, and the TSLNC8-transketolase-STAT3 axis is a potential therapeutic target for HCC treatment. (Hepatology 2018;67:171-187).

MiR‑218 inhibits the proliferation of human glioma cells through downregulation of Yin Yang 1.

Malignant glioma is the most common cancer type of the nervous system and the mechanisms driving the occurrence and development remain unclear, preventing effective treatment of this disease. Therefore, novel and efficient therapies for glioma are required. MicroRNAs (miRNAs) are small non‑coding RNAs that act as oncogenes or tumor suppressors in human cancer. In the present study, it was confirmed that Yin Yang‑1 (YY1), a transcription factor that is part of the polycomb group protein (PcG) family, is a direct target of miR‑218 in human glioma cells. It was demonstrated that YY1 promoted glioma cell proliferation and miR‑218 could inhibit glioma cell proliferation by targeting YY1, and indirectly reduced the degradation of p53. Together the results indicate that miR‑218 functions as a tumor suppressor in human glioma and suggest that overexpression of miR‑218 may be a potential strategy for the treatment of human glioma in the future.

The clinical significance and biological function of interferon regulatory factor 1 in cholangiocarcinoma

Interferon regulatory factor 1 (IRF1) has been suggested to act as a tumor suppressor in human cancers. However, the clinical significance and biological function of IRF1 in cholangiocarcinoma is poorly understood. In our results, IRF1 mRNA and protein expressions were decreased in cholangiocarcinoma tissues and cell lines compared with paired normal hepatic tissues and intrahepatic bile duct epithelial cell line. IRF1 protein low-expression was associated with tumor stage, tumor size, vascular invasion and metastasis and served as a poor independent prognostic parameter in cholangiocarcinoma patients. Up-regulation of IRF1 expression suppressed cholangiocarcinoma cells proliferation, migration and invasion, and blocked cell cycle progression, but has no effect on apoptosis. In conclusion, IRF1 is low-expressed in cholangiocarcinoma tissues and cell lines, and correlated with malignant status and prognosis in cholangiocarcinoma patients. IRF1 served as tumor suppressor in the regulation of cholangiocarcinoma cells proliferation, cell cycle, migration and invasion.

LncRNA CHRF-induced miR-489 loss promotes metastasis of colorectal cancer via TWIST1/EMT signaling pathway.

microRNA-489 (miR-489) is a novel cancer-related miRNAs and functions as a tumor suppressor in human cancers. While, the clinical significance of miR-489 and its role in colorectal cancer (CRC) remain rarely known. Here, we found that the levels of miR-489 in CRC tissues were significantly lower than those in matched tumor-adjacent tissues. Furthermore, decreased levels of miR-489 also observed in CRC cell lines compared to HIEC cells. Clinicopathological analysis revealed that miR-489 underexpression was positively correlated with advanced pT stage, pN stage and AJCC stage. Moreover, miR-489 low expressing CRC patients showed a obvious shorter survival. Functionally, miR-489 restoration inhibited cell migration and invasion as well as epithelial-mesenchymal transition (EMT) in HCT116 cells, while miR-489 loss facilitated these cellular processes in SW480 cells. In vivo experiments revealed that miR-489 overexpression reduced the number of metastatic nodules in nude mice liver. Notably, TWIST1 was recognized as a direct downstream target of miR-489 in CRC cells. Interestingly, TWIST1 restoration abrogated the effects of miR-489 on CRC cells with enhanced cell migration, invasion and EMT process. Furthermore, overexpression of long noncoding RNA cardiac hypertrophy-related factor (lncRNA CHRF) was inversely correlated with miR-489 expression in CRC tissues. CHRF knockdown increased the expression of miR-489 and suppressed EMT events of HCT116 cells, while CHRF overexpression showed opposite effects on miR-489 expression and EMT in SW480 cells. Taken together, this work support the first evidence that lncRNA CHRF-induced miR-489 loss facilitates metastasis and EMT process of CRC cells probably via TWIST1/EMT signaling pathway.

FAT1 prevents epithelial mesenchymal transition (EMT) via MAPK/ERK signaling pathway in esophageal squamous cell cancer

FAT1 regulates cell–cell adhesion, cell growth, cell migration, and actin dynamics as either oncogene or tumor suppressor in human cancers. We previously identified FAT1 was one of significant mutant genes in esophageal squamous cell carcinoma (ESCC). However, the function and underlying mechanism of FAT1 in ESCC have not been explored. In this study, we report that FAT1 expression was significantly lower in ESCC tumor tissues. Exogenous expression of FAT1 led to inhibition of cell proliferation and colony formation, as well as cell migration and invasion whereas FAT1 knockdown showed the opponent trends in vitro and in vivo. Moreover, FAT1 knockdown led to a statistically decrease of E-cadherin expression and a dramatically increase expression of N-cadherin, Vimentin, and Snail in a MAPK/ERK pathway-dependent manner. Meanwhile, over-expression of FAT1 resulted in the opposite trends. These alterations were abrogated in the presence of U0126, a MEK specific inhibitor. Collectively, our studies identified a novel role for FAT1 in inhibiting tumor growth and EMT occurrence in ESCC. We proposed that disruption of MAPK/ERK pathway by FAT1 contributes the EMT in ESCC and has important implications for understanding ESCC development.

Prognostic Significance of microRNA-7 and its Roles in the Regulation of Cisplatin Resistance in Lung Adenocarcinoma

Background: Previously, microRNA (miR)-7 has been reported to function as a tumor suppressor in human cancers, but the correlations of miR-7 expression with prognosis and cisplatin (CDDP) resistance in lung adenocarcinoma (LA) are unclear. Here, our aim is to determine the prognostic significance of miR-7 and its roles in the regulation of CDDP resistance in LA. Methods: Quantitative real-time PCR (qRT-PCR) assay was performed to determine miR-7 expression in 108 paired of LA tissues and analyze its correlations with clinicopathological factors of patients. The patient survival data were collected retrospectively by Kaplan-Meier analyses, and multivariate analysis was performed using the Cox proportional hazards model to determine the prognostic significance of miR-7 expression. The effects of miR-7 expression on the chemosensitivity of LA cells to CDDP and its possible mechanisms were evaluated by MTT, flow cytometry, Western blot and luciferase assays. Results: It was observed that the relative expression level of miR-7 in LA tissues was significantly lower than that in the adjacent normal tissues and low miR-7 expression level was closely associated with poorer tumor differentiation, advanced pathological T-factor, higher incidence of lymph node metastasis and advanced p-TNM stage. Also, patients with low miR-7 expression showed a shorter overall survival than those with high miR-7 expression, and multivariate analysis indicated that status of miR-7 expression was an independent molecular biomarker for predicting the overall survival (OS) of LA patients. In addition, upregulation of miR-7 increases the sensitivity of LA cells to CDDP via induction of apoptosis by targeting Bcl-2. Conclusions: Our finding for the first time demonstrates that low miR-7 expression may be an independent poor prognostic factor and targeting miR-7 may be a potential strategy for the reversal of CDDP resistance in LA.

Clinicopathological features and pituitary homeobox 1 gene expression in the progression and prognosis of cutaneous malignant melanoma

The evidence that PITX1 (pituitary homeobox 1) is a significant tumor suppressor in human cancer remains largely circumstantial, but it clearly warrants further study as little is known about the tumor-inhibitory roles of PITX1 in cutaneous malignant melanoma. The aims of this study were to investigate PITX1 gene expression in patients with cutaneous malignant melanoma and to evaluate its potential relevance to clinicopathological characteristics and tumor cell proliferation. Clinicopathological findings of patients with cutaneous malignant melanoma were analyzed retrospectively. PITX1 and Ki-67 expression were detected by immunohistochemistry in malignant melanoma and healthy tissue samples from each patient. Labeling indices were calculated based on PITX1 gene and Ki-67 expression. The correlation between PITX1and Ki-67 expressions was analyzed in cutaneous malignant melanoma cases. The relationship between PITX1 expression intensity and clinicopathological characteristics was also analyzed. PITX1 expression was observed in all (100%) normal healthy skin tissue samples. In addition, PITX1 expression was found in 56 (80%) and was absent in 14 (20%) of the 70 cutaneous malignant melanoma cases. Ki-67 positive expression was only detected in the 14 (20%) PITX1-negative cases. PITX1-positive tumor cells were observed on the surface, but Ki-67 positive tumor cells were observed in deeper zones of the tumor nests. PITX1 expression was downregulated in human cutaneous malignant melanoma lesions compared with healthy skin tissue, but Ki-67 expression was upregulated in concordance with the progression of cutaneous malignant melanoma. PITX1 expression may be involved in tumor progression and is a potential tumor suppressor gene and prognostic marker for cutaneous malignant melanoma.

Upregulation of Id3 inhibits cell proliferation and induces apoptosis in A549/DDP human lung cancer cells invitro.

Inhibitor of DNA binding (Id)3 is a member of the Idmultigene family of dominant‑negative helix‑loop-helix transcription factors, which function as oncogenes or tumor suppressors in human cancers. Its upregulation was recently shown to have inhibitory effects on lung cancer, which is the leading cause of cancer‑associated mortality worldwide. As drug resistance represents a major bottleneck of cancer therapy, the present study assessed the ability of Id3 to inhibit cisplatin‑resistant A549 lung adenocarcinoma cells (A549/DDP). A549/DPP cells were transiently transfected with enhanced green fluorescence protein overexpression plasmid (pEGFP) or Id3 overexpression plasmid (Id3/pEGFP), which was confirmed by confocal fluorescence microscopy, PCR and western blot analysis. The effects of Id3 on the viability and apoptosis of A549/DDP were determined using an MTT assay, fluorescence microscopy with Hoechst33258 staining and flow cytometry following AnnexinV/propidium iodide double staining. The results revealed that overexpression of Id3 significantly inhibited the proliferation and viability of A549/DDP cells in a time‑dependent manner. Furthermore, overexpression of Id3 significantly increased the apoptotic rate of A549/DDP cells from 2.73to 16.92%, confirming the implication of Id3 in the negative control of tumour growth. The results of the present study revealed that overexpression of Id3 may serve as a novel strategy for inhibiting cisplatin‑sensitive lung cancer. Further experiments will be performed to determine whether Id3 overexpression could enhance the sensitivity of lung cancer cells to DDP.

Tumor Suppressor Candidate 1 Suppresses Cell Growth and Predicts Better Survival in Glioblastoma.

Glioblastoma (GBM) is the most common malignant brain tumor with poor prognosis and limited treatment options. Tumor suppressor candidate 1 (TUSC1) was recently identified as a potential tumor suppressor in human cancers. However, the expression and potential function of TUSC1 in GBM remain unclear. Herein, we report that TUSC1 is significantly decreased in GBM tissues and cell lines. Patients with high levels of TUSC1 displayed a significant better survival compared with those with low levels of TUSC1. Functional experiments demonstrated that exogenous expression of TUSC1 inhibited GBM cell proliferation and induced G1 phase arrest by down-regulating CDK4. Moreover, overexpression of TUSC1 retarded tumor growth in vivo. Together, our findings revealed that TUSC1 might be a crucial tumor suppressor gene and a novel therapeutic target for GBM.

Stromal Expression of miR-143/145 Promotes Neoangiogenesis in Lung Cancer Development.

The two unrelated miRNAs miR-143 and miR-145, coexpressed from the miR-143/145 cluster, have been proposed to act as tumor suppressors in human cancer, and therapeutic benefits of delivering miR-143 and miR-145 to tumors have been reported. In contrast, we found that tumor-specific deletion of miR-143/145 in an autochthonous mouse model of lung adenocarcinoma did not affect tumor development. This was consistent with the lack of endogenous miR-143/145 expression in normal and transformed lung epithelium. Surprisingly, miR-143/145 in the tumor microenvironment dramatically promoted tumor growth by stimulating the proliferation of endothelial cells. Loss of miR-143/145 in vivo led to derepression of the miR-145 target CAMK1D, an inhibitory kinase, which when overexpressed prevents mitotic entry of endothelial cells. As a consequence, tumors in miR-143/145-deficient animals exhibited diminished neoangiogenesis, increased apoptosis, and their expansion was limited by the tumor's ability to co-opt the alveolar vasculature. These findings demonstrate that stromal miR-143/145 promotes tumorigenesis and caution against the use of these miRNAs as agents in cancer therapeutics. This study shows that miR-143/145 expressed from the tumor microenvironment stimulates neoangiogenesis and supports tumor expansion in the lung, demonstrating a surprising role for the putative tumor suppressor miRNA cluster in promoting tumorigenesis. We propose inhibition of miR-143/145 as a therapeutic avenue to modulate tumor neoangiogenesis.

MicroRNA-497 inhibits cell proliferation and induces apoptosis by targeting YAP1 in human hepatocellular carcinoma.

microRNAs (miRNAs) function as oncogenes or tumor suppressors in human cancers by targeting mRNAs for degradation and/or translational repression. miR‐497 has been proposed as a tumor suppressive miRNA and its deregulation is observed in human cancers. However, the prognostic value of miR‐497 and its underlying molecular pathways involved in the initiation and development of hepatocellular carcinoma (HCC) are poorly investigated. In the present study, we found that the mean level of miR‐497 in HCC tissues was lower than that in adjacent nontumor tissues. Clinical data indicated that low expression of miR‐497 was prominently associated with adverse prognostic features of HCC including high serum alpha‐fetoprotein (AFP) level, large tumor size, high Edmondson–Steiner grading and advanced tumor–node–metastasis (TNM) stage. Furthermore, miR‐497 was an independent prognostic factor for indicating both 5‐year overall survival and disease‐free survival of HCC patients. Gain‐ and loss‐of‐function studies showed that miR‐497 reduced cell proliferation and induced apoptosis in HCC cells. Yes‐associated protein 1 (YAP1) was identified as a direct target of miR‐497 in HCC. An inverse correlation between YAP1 and miR‐497 expression was observed in HCC tissues. Notably, YAP1 knockdown abrogated the effects of miR‐497 deletion on HCC cells with decreased cell proliferation and increased apoptosis. In conclusion, we report that miR‐497 is a potent prognostic indicator and may suppress tumor growth of HCC by targeting YAP1.

Assays to Measure PTEN Lipid Phosphatase Activity In Vitro from Purified Enzyme or Immunoprecipitates.

PTEN is a one of the most frequently mutated tumor suppressors in human cancers. It is essential for regulating diverse biological processes and through its lipid phosphatase activity regulates the PI 3-Kinase signaling pathway. Sensitive phosphatase assays are employed to study the catalytic activity of PTEN against phospholipid substrates. Here we describe protocols to assay PTEN lipid phosphatase activity using either purified enzyme (purified PTEN lipid phosphatase assay) or PTEN immunopurified from tissues or cultured cells (cellular IP PTEN lipid phosphatase assay) against vesicles containing radiolabeled PIP3 substrate.

Identification of and Molecular Basis for SIRT6 Loss-of-Function Point Mutations in Cancer

Chromatin factors have emerged as the most frequently dysregulated family of proteins in cancer. We have previously identified the histone deacetylase SIRT6 as a key tumor suppressor, yet whether point mutations are selected for in cancer remains unclear. In this manuscript, we characterized naturally occurring patient-derived SIRT6 mutations. Strikingly, all the mutations significantly affected either stability or catalytic activity of SIRT6, indicating that these mutations were selected for in these tumors. Further, the mutant proteins failed to rescue sirt6 knockout (SIRT6 KO) cells, as measured by the levels of histone acetylation at glycolytic genes and their inability to rescue the tumorigenic potential of these cells. Notably, the main activity affected in the mutants was histone deacetylation rather than demyristoylation, pointing to the former as the main tumor-suppressive function for SIRT6. Our results identified cancer-associated point mutations in SIRT6, cementing its function as a tumor suppressor in human cancer.

MicroRNA-122 affects cell aggressiveness and apoptosis by targeting PKM2 in human hepatocellular carcinoma.

Human hepatocellular carcinoma (HCC) is a highly invasive tumor with frequent distant metastasis, which is the main cause for the poor prognosis. However, the mechanisms for metastasis remain poorly investigated. MicroRNAs (miRNAs) have been implicated in HCC progression. MicroRNA-122 (miR-122) is considered as a tumor suppressor in human cancer. In the present study, miR-122 expression was found to be significantly lower in HCC than the level in normal tumor-adjacent tissues. miR-122 was clearly silenced or downregulated in five HCC cell lines (HepG2, Hep3B, MHCC97H, Huh7 and SMMC-7721) compared with normal hepatocytes (LO2). HCC patients with low expression of miR-122 had a poor 3-year survival. Univariate analysis and multivariate Cox regression analysis indicated that miR-122 is an independent prognostic factor in HCC. Downregulation of miR-122 promoted proliferation and inhibited apoptosis in Hep3B cells. We found that the public miRNA database (TargetScan) predicted that PKM2 may be a target for miR-122, and the 3'-untranslated region (3'-UTR) of PKM2 contains a highly conserved binding site for miR-122. To identify this, pre-miR-122/anti-miR-122 were respectively transfected into the Hep3B cell line. We found that miR-122 overexpression significantly reduced the level of PKM2. Moreover, knockdown of PKM2 significantly increased miR-122 inhibitor-mediated Hep3B cell apoptosis and reduced miR-122 inhibitor-mediated Hep3B cell migration and invasion. Moreover, re-expression of PKM2 partially abrogated miR-122-induced HCC cell growth arrest and apoptosis in vivo. In conclusion, miR-122 serves as a prognostic biomarker and induces apoptosis and growth arrest by downregulating PKM2 in HCC.

Abstract 100: PTEN regulates polycomb repressive EZH2 expression and its deficiency correlates with active transcription mark H3K4Me3

Abstract Phosphatase and tensin homolog (PTEN) is one of the most commonly lost tumor suppressors in human cancers. Frequent genetic inactivation of PTEN occurs in glioblastoma, endometrial cancer, and prostate cancer; and reduced expression is found in many other tumor types such as lung and breast cancer. PTEN is mostly found in the cytosol and it transiently associates with the inner surface of the plasma membrane and removes a phosphate group from phosphatidylinositol 3,4,5-trisphosphate (PIP3) and by this, it regulates various cellular functions. However in the nucleus, PTEN mediates phosphatase independent functions and is believed to be important for its tumor suppressive roles. Functional studies further confirm the transcriptional regulatory role of the PTEN; however, the process by which PTEN acts as a potential modulator of chromatin structure and histone modification is unexplored. We observed that the enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2), a histone methyltransferase is upregulated in PTEN null mouse embryonic fibroblasts (MEFs) as compared to wild type counterparts, which suggested an inverse relation between EZH2 expression and PTEN expression. We further observed that phospho EZH2 levels (pEZH2ser21) were specifically upregulated in the PTEN null cells and coincided with the high pEZH2:EZH2 ratio in these settings, indicating that the majority of the upregulated EZH2 exists in the phosphorylated form. We also found that the pEZH2ser21 is mainly localized in the nucleus and only a small fraction exists in the cytoplasm, suggesting additional roles for pEZH2ser21 after partnering with cytoplasmic proteins. However, the non-phosphorylated form of the EZH2 is totally a nuclear protein under these conditions. Interestingly in PTEN null MEFs, transcriptional repression mark such as H3K27Me3 expression was downregulated with the simultaneous upregulation of H3K4Me3, an active transcription mark. Also, the increased expression of EZH2 primarily linked with the pause of active transcription, was associated with corresponding decrease in the H3K27Me3 repression mark which subsequently influenced the expression of various genes including senescence associated genes such as p21. Since, these aberrant histone methylation marks are hallmarks of various cancer pathologies, targeting EZH2 or its phosphorylation component could be a potential therapeutic strategy in cancers involving loss of PTEN. Taken together, these results demonstrate that in PTEN null processes, the pEZH2ser21 is capable of translocation, altering the histone marks and influencing genes associated with transcriptional repression and senescence. We also suggest that EZH2 could serve as important target for novel chemotherapeutics against cancers that are associated with loss of PTEN. Citation Format: Abid Hamid, Mohammad Imran Khan, Vaqar Mustafa Adhami, Hasan Mukhtar. PTEN regulates polycomb repressive EZH2 expression and its deficiency correlates with active transcription mark H3K4Me3. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 100. doi:10.1158/1538-7445.AM2015-100

A Genetic Porcine Model of Cancer.

The large size of the pig and its similarity in anatomy, physiology, metabolism, and genetics to humans make it an ideal platform to develop a genetically defined, large animal model of cancer. To this end, we created a transgenic “oncopig” line encoding Cre recombinase inducible porcine transgenes encoding KRASG12D and TP53R167H, which represent a commonly mutated oncogene and tumor suppressor in human cancers, respectively. Treatment of cells derived from these oncopigs with the adenovirus encoding Cre (AdCre) led to KRASG12D and TP53R167H expression, which rendered the cells transformed in culture and tumorigenic when engrafted into immunocompromised mice. Finally, injection of AdCre directly into these oncopigs led to the rapid and reproducible tumor development of mesenchymal origin. Transgenic animals receiving AdGFP (green fluorescent protein) did not have any tumor mass formation or altered histopathology. This oncopig line could thus serve as a genetically malleable model for potentially a wide spectrum of cancers, while controlling for temporal or spatial genesis, which should prove invaluable to studies previously hampered by the lack of a large animal model of cancer.

MiR-218 inhibits the proliferation of glioma U87 cells through the inactivation of the CDK6/cyclin D1/p21Cip1/Waf1 pathway.

Malignant gliomas are the most common and deadly primary brain tumors in adults and the high proliferative ability of these cells is one of the most important causes of the poor prognosis of this cancer. Suppressing the proliferation of malignant gliomas cells by altering effector molecules can significantly improve the prognosis of a patient. microRNAs (miRNAs) are small non-coding RNA molecules ∼22 nucleotides in length that are able to function as oncogenes or tumor suppressors in human cancer. In the present study, it was demonstrated that the expression level of miRNA-218 (miR-218) is markedly downregulated in glioma cell lines and human primary glioma tissues. Upregulation of miR-218 in glioma U87 cells dramatically inhibited the proliferation by inducing G1-S checkpoint arrest. Furthermore, it was demonstrated that ectopically expressing miR-218 in glioma U87 cells results in the downregulation of the expression of cyclin dependent kinase (CDK)6 and cyclin D1 and upregulation of the expression of p21Cip1/Waf1. In addition, it was identified that miR-218 inactivated the CDK6/cyclin D1/p21Cip1/Waf1 pathway by downregulating CDK6 expression through the direct targeting of the 3'-untranslated region of CDK6. The present results suggest that miR-218 plays an important role in the prevention of the proliferation of glioma cells, and the present study also revealed a novel mechanism for miRNA-mediated direct suppression of the CDK6/cyclin D1/p21Cip1/Waf1 pathway in glioma cells.

LATS2 induced by TNF-alpha and inhibited cell proliferation and invasion by phosphorylating YAP in oral squamous cell carcinoma.

Many reports indicated LATS2 was a component of the Hippo pathway, could phosphorylate and inactivate YAP, acted as a tumor suppressor in human cancers. But few studies investigated the role of LATS2 in oral squamous cell carcinoma (OSCC) and clarified the mechanisms of regulation of LATS2 expression. The expressions of LATS2 and phosphorylated YAP were detected by Western blotting in HN6 cells treated with TNF-α in different time and different dose. Luciferase reporter assays were performed to detect whether YAP can be phosphorylated by LATS2 in HN6 cells. Cell proliferation, anchorage independent growth in soft agar, transwell cell invasion assay, and nu mice in vivo xenografts growth were performed to study the effects of overexpression of LATS2 on OSCC cells. In this study, we confirmed that YAP can be phosphorylated by LATS2. LATS2 can be dose- and time-dependently induced by TNF-α in HN6 cells. Overexpression of LATS2 inhibited cell proliferation, colony formation, cell invasion, and in vivo xenografts growth in OSCC cells. LATS2 could be induced by TNF-alpha and inhibited cell proliferation and invasion by phosphorylating YAP in OSCC cells. LATS2 might play a role in the tumorigenesis of OSCC and might be a potential therapeutic target in OSCC treatment.