Role of long non-coding RNA HULC in cell proliferation, apoptosis and tumor metastasis of gastric cancer: A clinical and in vitro investigation

  • Authors:
    • Yan Zhao
    • Qinhao Guo
    • Jiejing Chen
    • Jun Hu
    • Shuwei Wang
    • Yueming Sun
  • View Affiliations

  • Published online on: November 14, 2013     https://doi.org/10.3892/or.2013.2850
  • Pages: 358-364
Metrics: Total Views: 0 (Spandidos Publications: | PMC Statistics: )
Total PDF Downloads: 0 (Spandidos Publications: | PMC Statistics: )


Abstract

Long non-coding RNAs (lncRNAs) are emerging as key molecules in human cancer. Highly upregulated in liver cancer (HULC), an lncRNA, has recently been revealed to be involved in hepatocellular carcinoma development and progression. It remains unclear, however, whether HULC plays an oncogenic role in human gastric cancer (GC). In the present study, we demonstrated that HULC was significantly overexpressed in GC cell lines and GC tissues compared with normal controls, and this overexpression was correlated with lymph node metastasis, distant metastasis and advanced tumor node metastasis stages. In addition, a receiver operating characteristic (ROC) curve was constructed to evaluate the diagnostic values and the area under the ROC curve of HULC was up to 0.769. To uncover its functional importance, gain- and loss-of-function studies were performed to evaluate the effect of HULC on cell proliferation, apoptosis and invasion in vitro. Overexpression of HULC promoted proliferation and invasion and inhibited cell apoptosis in SGC7901 cells, while knockdown of HULC in SGC7901 cells showed the opposite effect. Mechanistically, we discovered that overexpression of HULC could induce patterns of autophagy in SGC7901 cells; more importantly, autophagy inhibition increased overexpression of HULC cell apoptosis. We also determined that silencing of HULC effectively reversed the epithelial-to-mesenchymal transition (EMT) phenotype. In summary, our results suggest that HULC may play an important role in the growth and tumorigenesis of human GC, which provides us with a new biomarker in GC and perhaps a potential target for GC prevention, diagnosis and therapeutic treatment.

Introduction

Gastric cancer (GC) is the second leading cause of cancer-related mortality globally (1). There are ~750,000 new cases diagnosed annually around the world and 5-year overall survival rates are <25% (2). In spite of the progress in understanding the pathophysiological mechanisms and treatment for GC in recent years, the overall survival time of GC patients has not changed significantly. Thus, a deeper understanding of the molecular and genetic networks that control the initiation and progression of GC is imperative.

Long non-coding RNAs (lncRNAs) are a class of newfound non-coding RNAs, <200 nucleotides in length (3). LncRNAs, such as H19, HOTAIR and MEG3, have been suggested to have a functional role in tumorigenesis and tumor progression (4). Highly upregulated in liver cancer (HULC) is ~1.6 k nucleotides long containing two exons but not translated (5,6). It has been shown that HULC might function as a miRNA sponge for miRNA372 and could thereby regulate gene expression at a post-transcriptional level (7). Moreover, Matouk et al(8) reported for the first time that HULC is not HCC-specific and is high in liver nodule of colon cancer origin but not in primary colorectal carcinoma samples and corresponding normal counterparts. However, investigations of HULC in GC are scarce. The expression pattern of HULC in human GC tissues and cell lines, its biological roles, and potential mechanisms in GC progression still need to be addressed.

Epithelial-to-mesenchymal transition (EMT), an essential cell-biological program during embryonic development, contributes to cancer invasion and metastasis (9,10). Autophagy is generally thought to be a double-edged sword in the regulation of tumor progression and some studies showed that autophagy activation is upregulated in cancer cells and contributes to tumor cell survival (11,12). Furthermore, it has been shown that EMT involves the autophagy activation of several important pathways that help tumors survive and evolve into highly invasive and metastatic variants (13). In the present study, we examined the role of HULC in GC and the potential mechanisms involved by a retrospective analysis of 58 GC patients, and by carrying out in vitro experiments to clarify the contribution of HULC to various aspects of the malignant phenotype of human GC and its effect on autophagy and EMT.

Materials and methods

Tissue specimens

Fifty-eight specimens of GC tissues and adjacent non-cancer tissues were surgically obtained between January 2012 and May 2013 at the First Affiliated Hospital of Nanjing Medical University (median age, 64; range, 45–84). Written informed consent was obtained from all patients prior to sample collection. The matched normal gastric tissue samples were obtained from tissues that were 5 cm from the edge of the tumor and there were no obvious tumor cells, as evaluated by a pathologist. Tissue specimens were immediately frozen in liquid nitrogen after surgery and stored at −80°C until the extraction of total RNA. TNM disease stage was classified according to the American Joint Committee on Cancer (AJCC), 7th Edition. None of the patients recruited in the present study received any preoperative treatments.

Cell lines and cell culture

Human gastric epithelial mucosa cell line GES-1, GC cell lines SGC7901, MKN28, MKN45, AGS and BGC823 were maintained in our laboratory. The cells were cultured in RPMI-1640 containing 10% fetal bovine serum (FBS) (Gibco, Grand Island, NY, USA), 100 U/ml of penicillin sodium at 37°C in a humidified environment containing 5% CO2.

Quantitative real-time (RT)-PCR

Total RNA from cells and tissues was extracted using TRIzol reagent (Invitrogen, Carlsbad, CA, USA). cDNA was synthesized using the PrimeScript RT kit (Takara, Dalian, China). Quantitative RT-PCR was performed with FastStart Universal SYBR-Green Master (Rox) (Roche Diagnostics, Indianapolis, IN, USA) with an ABI 7500 (Applied Biosystems, Life Technologies Corporation, Carlsbad, CA, USA). The qPCR cycling was performed as follows: initial denaturation at 95°C for 10 min followed by 40 cycles of denaturation at 95°C for 10 sec, annealing for 60 sec at 55°C (HULC), 50°C (E-cadherin) or 60°C (vimentin) and finally a melting curve profile was set at 60°C (30 sec). Primers for qRT-PCR were synthesized by Invitrogen (Shanghai, China) and the sequences were: HULC sense, 5′-ACTCTGAAGTAAAGGCCGGA-3′ and antisense, 5′-TGCCAGGAAACTTCTTGCTTG-3′; E-cadherin sense, 5′-GTGTCATCCAACGGAATGC-3′ and antisense, 5′-TGG CGGCATTGTAGGTGTTC-3′; vimentin sense, 5′-ATGAC CGCTTCGCCAACTAC-3′ and antisense, 5′-CGGGCTTTG TCGTTGGTTAG-3′. β-actin was used as an internal control, and the following primer sequences were used to amplify β-actin: forward, 5′-CTACAATGAGCTGCGTGTGG-3′ and reverse, 5′-AAGGAAGGCTGGAAGAGTGC-3′. PCR amplifications were performed in three duplicates for each sample.

Lentivirus packaging and stable transfection cell line generation

To further investigate the function of HULC, HULC expression was modified by gene knockdown and overexpression via lentivirus vector. We modified the commercial LV-HULC vector and LV-HULC-30 vector lentiviral constructs (Shanghai Genepharma Co., Ltd., Shanghai, China) to overexpress or knock down HULC in GC cells. For knockdown, LV-HULC-30 (target sequence: 5′-GCCTTTACA AGGGAATGAAGA-3′), with ≥75% knockdown efficiency, was used for further studies. All lentiviral vectors expressed GFP and the efficiency of infection was measured under a fluorescent microscope based on GFP expression.

Western blot analysis

Cells were collected and lysed with RIPA lysis buffer (Beyotime Institute of Biotechnology, Shanghai, China). Equal amount of protein (30 μg) was loaded and separated on SDS-PAGE, and then transferred to polyvinylidene fluoride membranes (Millipore, Bedford, MA, USA). The membranes were blocked with 5% non-fat milk in Tris-buffered saline solution containing 0.05% Tween-20 and then incubated with antibodies specific for E-cadherin, vimentin, LC3-I and LC3-II (1:5,000; Cell Signaling Technology). Following incubation with goat anti-rabbit IgG (1:1,000; Cell Signaling Technology) at 37°C for 2 h, bound proteins were visualized using ECL (Pierce) and detected using a Bio-Imaging System. Protein levels were normalized to GAPDH (1:10,000; Cell Signaling Technology) and changes were determined.

Cell proliferation assay

Cell proliferation was evaluated using the Cell Counting Kit-8 (CCK-8; Beyotime Institute of Biotechnology) and following the manufacturer’s instructions. Briefly, cells were plated in 96-well plates in medium containing 10% FBS at ~5×103 cells/well. Then 10 μl CCK-8 solution was added to each well and incubated for 1 h. The absorbance at 450 nm was measured using a microplate reader. Results are representative of three individual experiments in triplicate.

Wound healing assay

Cells (5×105) were seeded in 6-well plates and cultured in complete medium. After 24 h, when the cells were grown to 90–100% confluency, a single wound was created in the center of the well by removing the attached cells with a sterile 200 μl pipette tip. After 24 h of culturing, the cells which migrated into the wounded area were visualized and photographed under an inverted microscope. Each experiment was performed at least three times independently.

Transwell migration and invasion assay

Transwell invasion assay was performed using Boyden’s chambers. Cells were planted in the upper chamber consisting of 8-mm membrane filter inserts coated with Matrigel (BD Biosciences). The chemoattractant in the lower chamber was supplemented with medium containing 10% FBS. Cells on the upper surface were removed by a wet cotton swab after 24 h, and those attached on the lower side of the membrane were fixed and stained with crystal violet before counting under a microscope in five randomly selected fields. Migration assays were performed the same way as the invasion assays, using Transwell compartment, with the exception that Matrigel was not included. At least three chambers from three different experiments were analyzed.

Flow cytometric analysis of apoptosis and autophagy

Cells (7,000,000) treated with LV-HULC or LV-NC-2 or 5 mM 3-methyladenine (3-MA; Sigma) were seeded into 6-cm tissue culture dishes for 24 h. For detection of apoptosis, adherent cells were both collected and resuspended in cold PBS for analysis. Apoptosis was detected using the Alexa Fluor® 647/7-AAD apoptosis kit (BioLegend, San Diego, CA, USA) according to the manufacturer’s instructions. Data were assessed by flow cytometry (Becton-Dickinson, San Jose, CA, USA).

Statistical analysis

Statistical Program for Social Sciences (SPSS) 20.0 software (IBM, SPSS, Inc., Chicago, IL, USA) was used for the statistical analysis. Data are expressed as mean ± standard deviation (SD) from at least three separate experiments. Statistical analyses were performed with the Student’s t-test. ROC curve was established to evaluate the diagnostic value for differentiating between GC tissues and normal tissues. Differences were considered to be statistically significant at P<0.05.

Results

HULC is upregulated in GC tissues and cell lines

To assess the role of HULC in GC progression, we first examined HULC expression levels in the GC cell lines and the human gastric epithelial mucosa cell line GES-1 using qRT-PCR. As presented in Fig. 1A, the expression of HULC was increased in three GC cell lines (SGC7901, BGC823 and AGS) relative to the expression in the human gastric epithelial mucosa cell line GES-1, but there was no significant difference for MKN28 and MKN45. Next, qRT-PCR assays were further developed to quantify HULC in 58 pairs of GC tissues and pair-matched adjacent normal tissues. HULC levels were markedly upregulated in cancerous tissues compared with noncancerous tissues (Fig. 1B). Then, we verified that expression of HULC was significantly correlated with lymph node metastasis, distant metastasis and TNM stages. However, we did not find any association between HULC expression levels and other clinicopathological features including age, gender, differentiation, tumor size, tumor location and CEA values (Table I). Finally, we examined whether HULC could be used as a marker of GC. We used corresponding adjacent non-tumorous tissues as a control to produce a ROC curve. The cut-off value was 10.88. The area under the ROC curve (AUC) was 0.769 (P<0.001). The sensitivity and specificity was 0.707 and 0.724. The Youden index was 0.431 (Fig. 1C).

Table I

The relationship between HULC expression levels (ΔCT) and clinicopathological factors of 58 GC patients.

Table I

The relationship between HULC expression levels (ΔCT) and clinicopathological factors of 58 GC patients.

CharacteristicsNo. of patients (%)Mean ± SDP-value
Age (years)
 ≥6032 (55.17)10.11±1.080.87
 <6026 (44.83)10.16±1.83
Gender
 Male44 (75.86)10.26±1.160.12
 Female14 (24.14)9.73±0.86
Diameter (cm)
 ≥5 (large)35 (60.34)10.09±1.010.7
 <5 (small)23 (39.66)10.21±1.27
Location
 Cardia or body22 (37.93)10.10±1.120.83
 Antrum36 (62.07)10.16±1.13
Differentiation
 Poor or not34 (58.62)9.98±1.070.20
 Well or moderate24 (41.38)10.36±1.16
Lymphatic metastasis
 Present41 (70.69)9.83±1.090.001
 Absent17 (29.31)10.87±0.82
Distal metastasis
 Present6 (10.34)9.06±0.460.01
 Absent52 (89.66)10.26±1.10
AJCC clinical stage
 I + II20 (34.48)10.73±0.910.003
 III + IV38 (65.52)9.83±1.10
Serum CEA value
 ≥5 μg/l38 (65.52)10.13±1.140.95
 <5 μg/l20 (34.48)10.15±1.09
Abnormally expressed HULC promotes the proliferation of GC cells

To characterize the functional importance of HULC in GC tumorigenesis, we infected SGC7901 cells with either HULC overexpression vector (LV-HULC) or lentivirus-mediated HULC silencing vector (LV-HULC-30) to increase or knock down the HULC expression, respectively. qRT-PCR was performed to examine the mRNA levels of HULC in the derived cells (Fig. 2A and C). CCK-8 assays indicated that enhanced expression of HULC promoted cell proliferation in SGC7901 cells. The inhibition of HULC, on the other hand, inhibited cell proliferation (Fig. 2B and D). These results suggest that HULC plays an important role in regulating cell proliferation.

Knockdown of HULC suppresses cell invasion and reverses EMT in GC

Studies indicated that knockdown of HULC inhibited the proliferation of SGC7901. We subsequently investigated the migration and invasion of SGC7901 cells following LV-HULC-30 transfection. The effect of HULC on the migration of SGC7901 cells determined by wound healing assay demonstrated that knockdown of HULC significantly inhibited the migration of SGC7901 cells compared with the SGC7901 only or negative control 1 vector-transfected cells (Fig. 3A). In analogical results observed in the Transwell assay, in comparison with original SGC7901 and negative control cells, the LV-HULC-30 cells showed decreased migration and invasion ability (Fig. 3B–D).

To further define the role of HULC in the progression of cell metastasis in GC cells, we then transfected the LV-HULC-30 vector and assessed the expression of EMT markers at mRNA and protein levels. As shown in Fig. 3E, silencing of HULC in SGC7901 cells induced round spheroids with no or few protrusions. Depletion of HULC expression upregulated E-cadherin and downregulated vimentin expressions at mRNA and protein levels, respectively (Fig. 3F and G). Our in vitro study confirmed that HULC positively regulates GC cell migration and invasion and deletion of HULC reverses EMT, indicating that HULC could act as a possible regulator of EMT.

Upregulated HULC inhibits cell apoptosis by activating autophagy

To explore the mechanisms of HULC in regulating tumorigenesis, we then investigated whether HULC regulates cell apoptosis-related signals, focusing on autophagy. For that purpose, we initially determined a change in the expression level of the microtubule-associated protein 1 light chain 3 (LC3)-II, a marker for the presence of autophagosomes. As shown in Fig. 4A, HULC overexpression resulted in an increase in the ratio of LC3-II/LC3-I. These data suggest that upregulated HULC contributes to autophagy activation in SGC7901. Subsequently, to further study the role of HULC in the regulation of cell apoptosis, SGC7901 cells were treated with LV-HULC or 3-MA (an inhibitor of autophagic sequestration blocker). As depicted in Fig. 4B and C, enhanced expression of HULC inhibited SGC7901 cell apoptosis, whereas autophagy inhibition increased cell apoptosis in SGC7901 cells treated with LV-HULC.

Discussion

Emerging evidence suggests that lncRNAs play a crucial role in the modulation of tumor behavior through various complex mechanisms such as modulating gene transcription and epigenetic signaling; however, limited data are available on the expression and function of lncRNAs in GC (1417). Hence, in the present study, we tested the expression of a novel lncRNA HULC in GC tissues and cell lines. We also identified the function of HULC in GC cells by applying gain- and loss-of-function approaches. Our results demonstrated that HULC is upregulated in GC tissues in comparison with the adjacent normal gastric tissues. Of note, its level was significantly associated with lymph node metastasis, distant metastasis and TNM stages. Alteration of HULC expression provided further functional evidence, supporting the stimulatory effect of HULC on GC via enhancing aggressive biological behavior of cancer cells. There were certain limitations in the present study; all the patients enrolled were from a single institution and the number of samples was not sufficient to make subgroup analysis. For example, only six patients were at M1 status. In future studies, we will expand the samples for further investigation and seek to elucidate the association between HULC expression and overall survival of GC patients since the present study was limited to patients who underwent complete resection and the follow-up period after surgery was short.

Metastasis is a complex and multistep process, which has to be divided into 2 phases; namely, physical translocation of a tumor cell from the primary tumor to a distant tissue to seed and colonization of disseminated tumor cell in the tissue (18). A crucial mechanism by which carcinoma cells enhance their invasive capacity is the dissolution of intercellular adhesions and the acquisition of a more motile mesenchymal phenotype as part of an epithelial-to-mesenchymal transition (EMT) (19). During EMT, epithelial markers that are downregulated during this process include E-cadherin, ZO-1 and MUC1 (20,21). Molecules that are upregulated in this process include the transcription factors Snail, Slug, Twist as well as N-cadherin and vimentin (22,23). To determine whether these tumor characteristics initiated by HULC are associated with the EMT, we focused on hallmarks of the EMT phenotype. Notably, in the present study, we showed for the first time that HULC is a positive regulator of EMT. This conclusion was based on the observation that silencing HULC induced a repertoire of biochemical (increased E-cadherin and decreased vimentin) and morphological (growth pattern, decreased formation of lamellipodia) changes that reverse EMT. Furthermore, we confirmed that downregulation of HULC expression decreased the invasion and migration ability of SGC7901 cells. These results indicated that alterative expression of HULC, at least in part, had an impact on the process of EMT by regulating the expression of E-cadherin and vimentin in GC cells, suggesting that HULC plays a causative role in epithelial characteristics weakening. However, the concrete mechanisms of how HULC regulates E-cadherin and vimentin expression in SGC7901 cells remain to be clarified in our future studies

Programmed cell death (PCD), including two classical forms, apoptosis and autophagy, is a crucial mechanism for maintaining cell homeostasis of multicellular organisms. Autophagy, termed type II PCD, is generally activated by conditions of nutrient deprivation, but it has also been associated with a number of physiological processes including development, differentiation, infection and cancer (2427). However, in cancer development, autophagy has been shown to have a dual role. In some cases, autophagy is a tumor-suppressive mechanism, but in others, autophagy promotes tumorigenesis (2830). Therefore, one question that has emerged from our studies is whether autophagy displays a cytotoxic or cytoprotective role. Autophagosome marker light chain 3 (LC3) was originally identified as a subunit of microtubule-associated proteins 1A and 1B and was subsequently found to be similar to the yeast protein Apg8/Aut7/Cvt5 critical for autophagy (31,32). The conversion of LC3 to the lower migrating form, LC3-II, has been used as an indicator of autophagy (33). Studies are beginning to elucidate the association between autophagy and lncRNA. Ying et al(34) demonstrated that downregulated MEG3 promotes cell proliferation by activating autophagy in bladder cancer. In the present study, we provided a line of evidence that HULC may be involved in a molecular switch mechanism between apoptosis and autophagy in SGC7901 cells. However, despite data from the present study, several issues remain to be clarified, such as the relationship between autophagy and apoptosis, especially in cancer cells, the role of PI3K-Akt-mTOR signaling pathway in autophagy, and the parameters that determine whether autophagy is pro-survival or pro-death, tumor promoting or tumor suppressive. Future studies are required to better understand the function of this novel gene and its role in GC tumorigenesis in vivo.

In the present study, for the first time, we found that high expression levels of HULC, a cancer-related lncRNA, correlated clinically with GC progression. Additionally, HULC contributed to the malignant phenotype of GC cells through its regulation of diverse cellular processes, including proliferation, apoptosis, migration and invasion. Therefore, the above findings not only suggest a useful candidate molecular marker for GC and an indicator for advanced-stage GC, but they also provide new insights into the role of lncRNA in cancer biology.

Acknowledgements

The present study was supported by the Department of Health of the Jiangsu Province Fund.

Abbreviations:

lncRNA

long non-coding RNA

GC

gastric cancer

HULC

highly upregulated in liver cancer

AJCC

American Joint Committee on Cancer

EMT

epithelial-to-mesenchymal transition

3-MA

3-methyladenine

mRNA

messenger RNA

References

1 

Konishi H, Ichikawa D, Komatsu S, et al: Detection of gastric cancer-associated microRNAs on microRNA microarray comparing pre- and post-operative plasma. Br J Cancer. 106:740–747. 2012. View Article : Google Scholar : PubMed/NCBI

2 

Cheng Y, Jin Z, Agarwal R, et al: LARP7 is a potential tumor suppressor gene in gastric cancer. Lab Invest. 92:1013–1019. 2012. View Article : Google Scholar : PubMed/NCBI

3 

Costa FF: Non-coding RNAs: new players in eukaryotic biology. Gene. 357:83–94. 2005. View Article : Google Scholar : PubMed/NCBI

4 

Batista PJ and Chang HY: Long noncoding RNAs: cellular address codes in development and disease. Cell. 152:1298–1307. 2013. View Article : Google Scholar : PubMed/NCBI

5 

Panzitt K, Tschernatsch MM, Guelly C, et al: Characterization of HULC, a novel gene with striking up-regulation in hepatocellular carcinoma, as noncoding RNA. Gastroenterology. 132:330–342. 2007. View Article : Google Scholar : PubMed/NCBI

6 

Xu D, Yang F, Yuan JH, et al: Long noncoding RNAs associated with liver regeneration 1 accelerates hepatocyte proliferation during liver regeneration by activating Wnt/β-catenin signaling. Hepatology. 58:739–751. 2013.PubMed/NCBI

7 

Wang J, Liu X, Wu H, et al: CREB up-regulates long non-coding RNA, HULC expression through interaction with microRNA-372 in liver cancer. Nucleic Acids Res. 38:5366–5383. 2010. View Article : Google Scholar : PubMed/NCBI

8 

Matouk IJ, Abbasi I, Hochberg A, Galun E, Dweik H and Akkawi M: Highly upregulated in liver cancer noncoding RNA is overexpressed in hepatic colorectal metastasis. Eur J Gastroenterol Hepatol. 21:688–692. 2009. View Article : Google Scholar : PubMed/NCBI

9 

Li J, Yang B, Zhou Q, et al: Autophagy promotes hepatocellular carcinoma cell invasion through activation of epithelial-mesenchymal transition. Carcinogenesis. 34:1343–1351. 2013. View Article : Google Scholar : PubMed/NCBI

10 

Ledford H: Cancer theory faces doubts. Nature. 472:2732011. View Article : Google Scholar : PubMed/NCBI

11 

Enomoto M, Tsuchida A, Miyazawa K, et al: Vitamin K2-induced cell growth inhibition via autophagy formation in cholangiocellular carcinoma cell lines. Int J Mol Med. 20:801–808. 2007.PubMed/NCBI

12 

Lv Q, Hua F and Hu ZW: DEDD, a novel tumor repressor, reverses epithelial-mesenchymal transition by activating selective autophagy. Autophagy. 8:1675–1676. 2012. View Article : Google Scholar : PubMed/NCBI

13 

Akalay I, Janji B, Hasmim M, et al: Epithelial-to-mesenchymal transition and autophagy induction in breast carcinoma promote escape from T-cell-mediated lysis. Cancer Res. 73:2418–2427. 2013. View Article : Google Scholar : PubMed/NCBI

14 

Nie Y, Liu X, Qu S, Song E, Zou H and Gong C: Long non-coding RNA HOTAIR is an independent prognostic marker for nasopharyngeal carcinoma progression and survival. Cancer Sci. 104:458–464. 2013. View Article : Google Scholar : PubMed/NCBI

15 

Yang F, Bi J, Xue X, et al: Up-regulated long non-coding RNA H19 contributes to proliferation of gastric cancer cells. FEBS J. 279:3159–3165. 2012. View Article : Google Scholar : PubMed/NCBI

16 

Yang H, Zhong Y, Xie H, et al: Induction of the liver cancer-down-regulated long noncoding RNA uc002mbe.2 mediates trichostatin-induced apoptosis of liver cancer cells. Biochem Pharmacol. 85:1761–1769. 2013. View Article : Google Scholar : PubMed/NCBI

17 

Wahlestedt C: Targeting long non-coding RNA to therapeutically upregulate gene expression. Nat Rev Drug Discov. 12:433–446. 2013. View Article : Google Scholar : PubMed/NCBI

18 

Liu Q, Huang J, Zhou N, et al: LncRNA loc285194 is a p53-regulated tumor suppressor. Nucleic Acids Res. 41:4976–4987. 2013. View Article : Google Scholar : PubMed/NCBI

19 

Lv Q, Wang W, Xue J, et al: DEDD interacts with PI3KC3 to activate autophagy and attenuate epithelial-mesenchymal transition in human breast cancer. Cancer Res. 72:3238–3250. 2012. View Article : Google Scholar : PubMed/NCBI

20 

Shin NR, Jeong EH, Choi CI, et al: Overexpression of Snail is associated with lymph node metastasis and poor prognosis in patients with gastric cancer. BMC Cancer. 12:5212012. View Article : Google Scholar : PubMed/NCBI

21 

Lin X, Shang X, Manorek G and Howell SB: Regulation of the epithelial-mesenchymal transition by claudin-3 and claudin-4. PLoS One. 8:e674962013. View Article : Google Scholar : PubMed/NCBI

22 

Davidson B, Trope CG and Reich R: Epithelial-mesenchymal transition in ovarian carcinoma. Front Oncol. 2:332012. View Article : Google Scholar : PubMed/NCBI

23 

Zeisberg M and Neilson EG: Biomarkers for epithelial-mesenchymal transitions. J Clin Invest. 119:1429–1437. 2009. View Article : Google Scholar : PubMed/NCBI

24 

Kalluri R and Weinberg RA: The basics of epithelial-mesenchymal transition. J Clin Invest. 119:1420–1428. 2009. View Article : Google Scholar : PubMed/NCBI

25 

Kondo Y, Kanzawa T, Sawaya R and Kondo S: The role of autophagy in cancer development and response to therapy. Nat Rev Cancer. 5:726–734. 2005. View Article : Google Scholar : PubMed/NCBI

26 

Levine B and Yuan J: Autophagy in cell death: an innocent convict? J Clin Invest. 115:2679–2688. 2005. View Article : Google Scholar : PubMed/NCBI

27 

He H, Zang LH, Feng YS, et al: Physalin A induces apoptotic cell death and protective autophagy in HT1080 human fibrosarcoma cells. J Nat Prod. 76:880–888. 2013. View Article : Google Scholar : PubMed/NCBI

28 

Mizushima N, Levine B, Cuervo AM and Klionsky DJ: Autophagy fights disease through cellular self-digestion. Nature. 451:1069–1075. 2008. View Article : Google Scholar : PubMed/NCBI

29 

Ye L, Zhao X, Lu J, Qian G, Zheng JC and Ge S: Knockdown of TIGAR by RNA interference induces apoptosis and autophagy in HepG2 hepatocellular carcinoma cells. Biochem Biophys Res Commun. 437:300–306. 2013. View Article : Google Scholar : PubMed/NCBI

30 

Oh SY, Choi SJ, Kim KH, Cho EY, Kim JH and Roh CR: Autophagy-related proteins, LC3 and Beclin-1, in placentas from pregnancies complicated by preeclampsia. Reprod Sci. 15:912–920. 2008. View Article : Google Scholar : PubMed/NCBI

31 

Mann SS and Hammarback JA: Molecular characterization of light chain 3. A microtubule binding subunit of MAP1A and MAP1B. J Biol Chem. 269:11492–11497. 1994.PubMed/NCBI

32 

Lang T, Schaeffeler E, Bernreuther D, Bredschneider M, Wolf DH and Thumm M: Aut2p and Aut7p, two novel microtubule-associated proteins are essential for delivery of autophagic vesicles to the vacuole. EMBO J. 17:3597–3607. 1998. View Article : Google Scholar : PubMed/NCBI

33 

Kabeya Y, Mizushima N, Yamamoto A, Oshitani-Okamoto S, Ohsumi Y and Yoshimori T: LC3, GABARAP and GATE16 localize to autophagosomal membrane depending on form-II formation. J Cell Sci. 117:2805–2812. 2004. View Article : Google Scholar : PubMed/NCBI

34 

Ying L, Huang Y, Chen H, et al: Downregulated MEG3 activates autophagy and increases cell proliferation in bladder cancer. Mol Biosyst. 9:407–411. 2013. View Article : Google Scholar : PubMed/NCBI

Related Articles

Journal Cover

January 2014
Volume 31 Issue 1

Print ISSN: 1021-335X
Online ISSN:1791-2431

Sign up for eToc alerts

Recommend to Library

Copy and paste a formatted citation
APA
Zhao, Y., Guo, Q., Chen, J., Hu, J., Wang, S., & Sun, Y. (2014). Role of long non-coding RNA HULC in cell proliferation, apoptosis and tumor metastasis of gastric cancer: A clinical and in vitro investigation. Oncology Reports, 31, 358-364. https://doi.org/10.3892/or.2013.2850
MLA
Zhao, Y., Guo, Q., Chen, J., Hu, J., Wang, S., Sun, Y."Role of long non-coding RNA HULC in cell proliferation, apoptosis and tumor metastasis of gastric cancer: A clinical and in vitro investigation". Oncology Reports 31.1 (2014): 358-364.
Chicago
Zhao, Y., Guo, Q., Chen, J., Hu, J., Wang, S., Sun, Y."Role of long non-coding RNA HULC in cell proliferation, apoptosis and tumor metastasis of gastric cancer: A clinical and in vitro investigation". Oncology Reports 31, no. 1 (2014): 358-364. https://doi.org/10.3892/or.2013.2850