MicroRNA-17 induces epithelial-mesenchymal transition consistent with the cancer stem cell phenotype by regulating CYP7B1 expression in colon cancer

  • Authors:
    • Xiang‑Peng Xi
    • Jing Zhuang
    • Mu‑Jian Teng
    • Li‑Jian Xia
    • Ming‑Yu Yang
    • Qing‑Gen Liu
    • Jing‑Bo Chen
  • View Affiliations

  • Published online on: June 6, 2016     https://doi.org/10.3892/ijmm.2016.2624
  • Pages: 499-506
Metrics: Total Views: 0 (Spandidos Publications: | PMC Statistics: )
Total PDF Downloads: 0 (Spandidos Publications: | PMC Statistics: )


Abstract

MicroRNA-17 (miRNA-17/miR‑17) expression has been confirmed to be significantly higher in colorectal cancer tissues than in normal tissues. However, its exact role in colorectal cancer has not yet been fully elucidated. In this study, we found that miR-17 not only promoted epithelial-mesenchymal transition (EMT), but also promoted the formation of a stem cell-like population in colon cancer DLD1 cells. We also wished to determine the role of cytochrome P450, family 7, subfamily B, polypeptide 1 (CYP7B1) in CRC. miR-17 was overexpressed using a recombinant plasmid and CYP7B1 was silenced by transfection with shRNA. Western blot analysis was used to determine protein expression in the DLD1 cells and in tumor tissues obtained from patients with colon cancer. Our results revealed that miR‑17 overexpression led to the degradation of CYP7B1 mRNA expression in DLD1 cells. In addition, we found that the silencing of CYB7B1 promoted EMT and the formation of a stem cell-like population in the cells. Thus, our findings demonstrate that miR‑17 induces EMT consistent with the cancer stem cell phenotype by regulating CYP7B1 expression in colon cancer.

Introduction

Colorectal cancer (CRC) is a major cause of cancer morbidity and mortality. Nearly 150,000 US residents are diagnosed annually with CRC, and approximately one-third of patients with CRC succumb to the disease (1). The lifetime risk of CRC in the US is 6%, and the average age at diagnosis is 66 years (2). Primary CRC originates from epithelial cells that line the gastrointestinal tract (3). During progression to metastasis, cancer cells are thought to acquire a mesenchymal phenotype, which allows them to leave the site of the primary tumor, invade surrounding tissues, and migrate to distant organs. After seeding, these cells switch back to an epithelial phenotype and proliferate to form metastases (4). The processes by which cells switch between the epithelial and mesenchymal phenotypes are known as epithelial-to-mesenchymal transition (EMT) and its counterpart, mesenchymal-to-epithelial transition (MET) (5). However, the molecular mechanisms responsible for EMT in CRC are not yet fully understood.

The steroid hydroxylase cytochrome P450, family 7, subfamily B, polypeptide 1 (CYP7B1), a member of the cytochrome P450 enzyme family, has attracted increasing attention over the years due to its multiple reported roles for key events in cellular physiology (614). CYP7B1 is widely expressed in tissues of human and other species and metabolizes several steroids involved in hormonal signaling and other processes. Substrates for CYP7B1 include 5a-androstane-3b, 17b-diol (3b-Adiol), an estrogen receptor (ER) agonist and dehydroepiandrosterone (DHEA), an essential precursor for androgens and estrogens (1318). CYP7B1 expression is diminished in ER+ tumors and is predictive of overall survival in breast cancer (19,20). However, its role in CRC is not yet fully understood.

MicroRNAs (miRNAs or miRs), are small non-coding RNAs which are 21–25 nt in length, and are widely expressed in eukaryotic cells, functioning as post-translational regulators (21). Due to their wide variety of target genes, miRNAs affect a number of biological pathways, including cell proliferation, development and differentiation. The deregulation of miRNAs facilitates cancer development by upregulating oncogenes or silencing tumor suppressor genes (22). miRNAs have been demonstrated to regulate the expression levels of major cancer-related genes and hence may be useful in the treatment of cancer (23,24).

In this study, we found that miR-17 not only promoted EMT, but also promoted the formation of a stem cell-like population in colon cancer DLD1 cells. Our results revealed that miR-17 degrdade CYP7B1 mRNA expression in DLD1 cells. In addition, we found that the silencing of CYB7B1 promoted EMT and the formation of a stem cell-like population in the colon cancer cells. Thus, our findings suggest that miR-17 induces EMT consistent with the cancer stem cell phenotype by regulating CYP7B1 expression in colon cancer.

Materials and methods

Cell culture and tissues samples

DLD1 cells were obtained from the American Type Culture Collection (ATCC, Manassas, VA, USA). The cells were cultured in Dulbecco's modified Eagle's medium (DMEM) supplemented with fetal bovine serum (FBS) (both from HyClone, Ogden, UT, USA) and penicillin-streptomycin. Normal and tumor tissues were obtained from 6 patients were recruited from Shandong Provincial Qianfoshan Hospital, Jinan, China. The tissues were obtained during colon cancer surgery. Normal tissues were adjacent to the tumor tissues. None of the patients received any anti-cancer treatment prior to surgery. The use of human tissue samples was carried out in accordance with internationally recognised guidelines as well as local and national regulations. This study was approved by the Ethics Committee of Shandong Provincial Qianfoshan Hospital and all patients provided written informed consent prior to obtaining the samples.

Plasmids and transfection

The shRNA plasmids were obtained from Tiangen (Beijing, China). Both scramble control sequence and interference sequence (shRNA) of CYP7B1 were designed and synthesized to build the recombinant plasmids; Pre-miR-17 and control miR (purchased from Ambion, Inc. Austin, TX, USA). The cells were cultured in serum-free medium without antibiotics and then separately transfected with shCYP7B1/scramble plasmids or Pre-miR-17/control miR using transfection reagent (Lipofectamine 2000; Invitrogen, Carlsbad, CA, USA) according to the manufacturer's instructions.

Western blot analysis

The tissues or cells were homogenized in RIPA lysis buffer containing PMSF and centrifuged at 200 × g for 10 min. Protein lysates were separated by electrophoresis and transferred onto PVDF membranes, and the blots were blocked with 5% non-fat milk for 1 h and incubated overnight at 4°C with primary antibodies against CYP7B1 (ab175889; 1:500), vimentin (ab92547; 1:500), SNAIL (ab82846; 1:500), transforming growth factor beta 1 (TGFB1; ab92486; 1:500), zinc finger E-box binding homeobox (ZEB)1 (ab203829; 1:500), ZEB2 (ab138222; 1:500), Twist (ab50581; 1:500), β-catenin (ab32572; 1:500), Notch1 (ab8925; 1:500), β-actin (ab8227; 1:500) and CD44 (ab157107; 1:500) (all from Abcam, Cambridge, MA, USA). After washing, the blots were incubated with secondary antibodies (anti-rabbit secondary antibodies; ab6721; 1:10,000; Abcam). The protein bands were visualized by chemiluminescence and exposed to the Odyssey™ Infrared Imaging system (Gene Company, Lincoln, NE, USA).

Sphere growth analysis

The DLD1 cells transfected with shCYP7B1/scramble plasmids (1×103) in serum-free DMEM/1 mM Na-pyruvate were seeded on 0.5% agar pre-coated 6-well plates. After 1 week, half the medium was exchanged with serum-free medium every third day. Single spheres were selected and counted under a stereomicroscope (Olympus, Tokyo, Japan).

In vitro migration and invasion assays

The DLD1 cells transfected as indicated above (1×105) were placed into the upper compartment of the Transwell insert (Costar, Cambridge, MA, USA). For invasion assay, the two compartments were separated by a porous filter (8 µm pore) coated with Matrigel (BD Biosciences, San Jose, CA, USA). For migration assay, the filter membranes was not coated with Matrigel. The chambers were incubated for 24 h at 37°C, and the filters were then fixed in methanol and stained with hematoxylin. Quantification of the migration and invasion assays were performed by counting the number of cells at the lower surface of the filters.

Bioinformatics analysis

Potential targets of miRNAs were identified by a combined approach based on the commonly used web tool for bioinformatics algorithms miRanda (http://www.microrna.org/microrna/home.do).

Quantitative (real-time) polymerase chain reaction (qPCR) for miR-17

qPCR for miR-17 was performed using the total RNA kit I (Omega Bio-Tek, Norcross, GA, USA) and the miRcute miRNA qPCR detection kit (Tiangen). U6 miRNA was used as a housekeeping control. Small RNA was purified and enriched with the miRcute miRNA Isolation kit (Tiangen). miRNAs were prolonged by Escherichia coli poly(A) polymerase, and reverse transcription was performed with the miRcute miRNA First-Strand cDNA Synthesis kit and real-time PCR with the miRcute miRNA qPCR detection kit (Tiangen). Forward primers and reverse primers were provided by Tiangen. The universal reverse primer was provided in the miRcute miRNA qPCR detection kit.

Reverse transcription-quantitative PCR (RT-qPCR) for CYP7B1

Total RNA was isolated from cells or tissues using TRIzol reagent (Invitrogen). cDNA was synthesized from 1 µg of total RNA in a 20 µl reverse transcription (RT) system followed by PCR amplification in a 50 µl PCR system performed using an RT-PCR kit (Promega, Madison, WI, USA). The housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as an RNA loading control. The PCR primer sequences are as follows: CYP7B1 forward, 5′-CAATCCATGCAGTCACCTTC-3′ and reverse, 5′-TGCCTAGAGAAAAACAGAAAGACA-3′; and GAPDH forward, 5′-ATTCAACGGCACAGTCAAGG-3′ and reverse, 5′-GCAGAAGGGGCGGAGATGA-3′. PCR was conducted according to the manufacturer's instructions and the PCR products were analyzed by agarose gel electrophoresis. Gels were photographed and the densities of the bands were determined with a computerized image analysis system (Alpha Innotech, San Leandro, CA, USA). The area of each band was calculated as the integrated density value (IDV). Real-time PCR for CYP7B1 was performed with a Power SYBR-Green PCR Master Mix (Applied Biosystems, Carlsbad, CA, USA) according to the manufacturer's instructions.

Immunofluorescence staining

The cells transfected as indicated above were fixed with paraformaldehyde and permeabilized in Triton X-100 (Beijing Solarbio Biological Technology Co., Ltd., Beijing, China). After blocking, anti-CYP7B1 antibody (ab175889; Abcam) was added followed by incubation overnight at 4°C. After washing with phosphate-buffered saline (PBS), fluorescence-conjugated anti-rabbit secondary antibodies (ab6721; 1:10,000; Abcam) were added, and the coverslips were counterstained with 4′,6-diamidino-2-phenylindole (DAPI; Invitrogen-Molecular Probes, Eugene, OR, USA) for visualization of the nuclei. Microscopic analysis was observed under a Zeiss LSM-510 confocal microscope (Carl Zeiss, Jena, Germany).

Wound healing assay

The cells transfected as indicated above were seeded into a 24-well plate in DMEM containing 10% FBS and cultured to 90% confluence. The cell monolayer was subjected to a mechanical scratch wound using a sterile pipette tip. After washing with PBS, the cells were further incubated in DMEM without FBS for different periods of time. Digitized images of the wound area were captured using a IX71 fluorescence microscope (Olympus).

Statistical analysis

The results are shown as the means ± SEM. The Student's t-test was used to perform comparisons between two groups. A value of P<0.05 was considered to indicate a statistically significant difference.

Results

Silencing of CYP7B1 promotes EMT in colon cancer cells

In an attempt to examine CYP7B1 expression between colon cancer tissues and adjacent normal tissues, we performed western blot analysis using the cancer tissues and normal tissues. Protein was isolated from 6 pairs of colon cancer tissues and normal tissues (patient nos. 1–6). We found that CYP7B1 protein expression was significantly decreased in the cancer tissues compared with the adjacent normal tissues (Fig. 1A). This suggests that CYP7B1 may be a tumor suppressor gene in colon cancer.

In order to determine the role of CYP7B1 in colon cancer, we transfected the DLD1 cells with shCYP7B1 plasmid and western blot analysis was then performed. We found that CYP7B1 protein expression was significantly decreased in the cells transfected with the shCYP7B1 plasmid (Fig. 1B) and the silencing of CYP7B1 led to significant changes in DLD1 cell morphology (EMT, change in phenotype from a cobblestone-like to a spindle-like morphology) (Fig. 1C).

To further verify that the changes in cell morphology were caused by EMT, the expression levels of mesenchymal markers were compared in the DLD1 cells transfected with the shCYP7B1 plasmid and the cells transfected with the scramble plasmid. The results revealed that the expression of the mesenchymal markers (vimentin, SNAIL, TGFB1, ZEB1, ZEB2, Twist and Notch1) was induced by the silencing of CYP7B1 in the DLD1 cells (Fig. 1D).

EMT can result in increased cell invasion and migration (2527). Thus, we hypothesized that shCYP7B1 may also affect the invasion and migration ability of the DLD1 cells. To confirm this hypothesis, we performed cell invasion and migration assays, and would healing assay. We found that the silencing of CYP7B1 enhanced the migration (Fig. 1E and F) and invasion (Fig. 1F) ability of the cells.

Silencing of CYP7B1 promotes the formation of a stem cell-like population in colon cancer cells

EMT not only confers tumor cells with a distinct advantage for metastatic dissemination, but it also provides those cells with cancer stem cell-like characters for proliferation and drug resistance (2831). To determine whether colon cancer cells with an EMT phenotype have stem-like cell characteristics, sphere forming assay was conducted to assess the capacity of cancer stem cells (CSCs) or CSC-like cell self-renewal in this study. We found that the formation of spheres was increased by the silencing of CYP7B1 in the DLD1 cells (Fig. 2A). CD44 is a robust marker and is of functional importance for colorectal CSCs for cancer initiation (32). We also performed immunofluorescence staining to determine whether CD44 was affected by the silencing of CYP7B1 in the cells. The results revealed that CD44 protein was significantly increased by the silencing of CYP7B1 in the DLD1 cells (Fig. 2B). Consistent with the results of immunofluorescence staining, the results of western blot analysis demonstrated that CD44 protein expression was increased by the silencing of CYP7B1 in the cells (Fig. 2C).

miR-17 degrades CYP7B1 in colon cancer cells

Having demonstrated that the silencing of CYP7B1 promotes EMT and the formation of a stem cell-like population in colon cancer cells, we then wished to determine the mechanisms regulating CYP7B1 expression in the disease. miRNAs are small regulatory non-coding RNAs of 21–25 nucleotides in length. miRNAs are generated from their precursor transcripts by a series of processing steps. Mature miRNAs mediate mRNA degradation or suppress mRNA translation by binding to the 3′ untranslated region (3′UTR) of target mRNAs (33). To further confirm whether CYP7B1 can be regulated by miRNAs, we used the commonly used prediction algorithm, miRanda (http://www.microrna.org/microrna/home.do), to analyze the 3′UTR of CYP7B1. A dozen miRNAs were found by the algorithm. However, we focused on miR-17, as miR-17 expression has been confirmed to be significantly higher in CRC tissues than in normal tissues (34). However, its role in CRC has not yet been fully elucidated. The target sites on the 3′UTR of CYP7B1 are shown in Fig. 3A. We reasoned that miR-17 may downregulate CYP7B1 expression by targeting its 3′UTR in colon cancer. In an attempt to determine the role of miR-17 in regulating CYP7B1 expression in colon cancer cells, the DLD1 cells were transfected with pre-miR-17 or control miR. Following transfection, miR-17 expression was detected by qPCR and the results revealed that miR-17 expression was significantly increased by transfection of the cells with pre-miR-17 (Fig. 3B). Subsequently, we performed immunofluorescence staining in the DLD1 cells transfected with pre-miR-17 or control miR. The results revealed that CYP7B1 protein expression was evidently suppressed in the cells transfected with pre-miR-17 (Fig. 3C). We then performed RT-qPCR and western blot analysis to detect CYP7B1 expression in the DLD1 cells transfected with pre-miR-17 or control miR. The results revealed that the CYP7B1 protein (Fig. 3D) and mRNA (Fig. 3E) expression levels were significantly downregulated in the cells transfected with pre-miR-17. Consistent with the results of RT-qPCR, qPCR demonstrated that CYP7B1 mRNA expression was decreased in the DLD1 cells transfected with pre-miR-17, compared with the control miR-transfected cells (Fig. 3F). All the data demonstrated that miR-17 degraded CYP7B1 in colon cancer cells.

miR-17 promotes EMT in colon cancer cells

In order to determine the role of miR-17 in colon cancer, we transfected the DLD1 cells with pre-miR-17. We found that the overexpression of miR-17 led to significant changes in DLD1 cell morphology (EMT, change in phenotype from a cobblestone-like to a spindle-like morphology) (Fig. 4A). To further verify that the changes in cell morphology were caused by EMT, we performed invasion and migration assays, and would healing assay. We found that the overexpression of miR-17 enhanced the migration (Fig. 4B and C) and invasion (Fig. 4C) ability of the cells.

miR-17 promotes the formation of a stem cell-like population in colon cancer cells

To determine whether miR-17 promotes the development of stem-like cell characteristics, we performed sphere-forming assay to assess the capacity of CSC or CSC-like cell self-renewal in this study. We found that formation of spheres was increased by the overexpression of miR-17 in the DLD1 cells (Fig. 5A). We also performed western blot analysis to determine whether CD44 is affected by miR-17 in the cells. The results revealed that CD44 protein expression was significantly increased by the overexpression of miR-17 in the DLD1 cells (Fig. 5B).

Discussion

Mounting evidence suggests that the deregulation of miRNAs is involved in colon cancer pathogenesis, microsatellite stability status, therapeutic outcome and patient prognosis (3537). miR-17 expression has been confirmed to be significantly higher in CRC tissues than in normal tissues (34,38). However, its role in CRC has not yet been fully elucidated. In line with previous reports, we found that miR-17 not only promoted the EMT phenotype, but also promoted the formation of a stem cell-like population in colon cancer DLD1 cells. The results further confirmed that miR-17 is an oncogene in colon cancer. There is evidence to support that high levels of miR-17-92 cluster inhibit tumor growth and metastasis in vivo (39). However, Yu et al reported that the miR-17-92 cluster and its paralogs were significantly elevated in patients with colon cancer, and the increased expression of miR-17 was associated with a poor survival (40), further supporting our findings that miR-17 is an oncogene in colon cancer.

Previous studies have demonstrated that CYP7B1 plays an important role in cancer development and progression (20,41,42). The overexpression of CYP7B1 has been detected in prostatic adenocarcinoma (41). However, CYP7B1 expression is dimished in ER+ tumors and is predictive of a poor overall survival in breast cancer (20). We found that CYP7B1 protein expression was decreased in colon cancer tissues and that the silencing of CYP7B1 promoted the EMT phenotype and the formation of a stem cell-like population. In addition, CYP7B1 mRNA was degraded by miR-17 in colon cancer cells. We aim to further determine whether the expression of miR-17 inversely correlates with CYP7B1 expression in colorectal tumors in future studies.

In conclusion, miR-17-mediated CYP7B1 regulation in colon cancer cells demonstrated in this study has potential basic and clinical implications. On the one hand, miR-17 is a powerful oncogene by promoting EMT and the formation of a stem cell-like population in human colon cancer cells and the pharmacological suppression of miR-17 may represent a promising therapeutic strategy. On the other hand, CYP7B1 is a tumor suppressor gene and the overexpression of miR-17 can downregulate its expression. Our data lay the foundations for future research into the role of CYP7B1 in CRC and in other types of cancer.

Acknowledgments

This study was supported by grants from the Shandong Natural Science Foundation (no. ZR2011HQ054).

References

1 

Jemal A, Siegel R, Ward E, Hao Y, Xu J and Thun MJ: Cancer statistics, 2009. CA Cancer J Clin. 59:225–249. 2009. View Article : Google Scholar : PubMed/NCBI

2 

Hawk ET and Levin B: Colorectal cancer prevention. J Clin Oncol. 23:378–391. 2005. View Article : Google Scholar : PubMed/NCBI

3 

Brabletz T, Hlubek F, Spaderna S, Schmalhofer O, Hiendlmeyer E, Jung A and Kirchner T: Invasion and metastasis in colorectal cancer: Epithelial-mesenchymal transition, mesenchymal-epithelial transition, stem cells and beta-catenin. Cells Tissues Organs. 179:56–65. 2005. View Article : Google Scholar : PubMed/NCBI

4 

Thiery JP, Acloque H, Huang RY and Nieto MA: Epithelial-mesenchymal transitions in development and disease. Cell. 139:871–890. 2009. View Article : Google Scholar : PubMed/NCBI

5 

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

6 

Wu Z, Martin KO, Javitt NB and Chiang JY: Structure and functions of human oxysterol 7alpha-hydroxylase cDNAs and gene CYP7B1. J Lipid Res. 40:2195–2203. 1999.PubMed/NCBI

7 

Sulcová J and Stárka L: Characterisation of microsomal dehydroepiandrosterone 7-hydroxylase from rat liver. Steroids. 12:113–126. 1968. View Article : Google Scholar : PubMed/NCBI

8 

Norlin M and Wikvall K: Biochemical characterization of the 7alpha-hydroxylase activities towards 27-hydroxycholesterol and dehydroepiandrosterone in pig liver microsomes. Biochim Biophys Acta. 1390:269–281. 1998. View Article : Google Scholar : PubMed/NCBI

9 

Shoda J, Toll A, Axelson M, Pieper F, Wikvall K and Sjövall J: Formation of 7 alpha- and 7 beta-hydroxylated bile acid precursors from 27-hydroxycholesterol in human liver microsomes and mitochondria. Hepatology. 17:395–403. 1993. View Article : Google Scholar : PubMed/NCBI

10 

Weihua Z, Lathe R, Warner M and Gustafsson JA: An endocrine pathway in the prostate, ERbeta, AR, 5alpha-androstane-3beta,17beta-diol, and CYP7B1, regulates prostate growth. Proc Natl Acad Sci USA. 99:13589–13594. 2002. View Article : Google Scholar : PubMed/NCBI

11 

Norlin M: Expression of key enzymes in bile acid biosynthesis during development: CYP7B1-mediated activities show tissue-specific differences. J Lipid Res. 43:721–731. 2002.PubMed/NCBI

12 

Martin C, Ross M, Chapman KE, Andrew R, Bollina P, Seckl JR and Habib FK: CYP7B generates a selective estrogen receptor beta agonist in human prostate. J Clin Endocrinol Metab. 89:2928–2935. 2004. View Article : Google Scholar : PubMed/NCBI

13 

Rose KA, Stapleton G, Dott K, Kieny MP, Best R, Schwarz M, Russell DW, Björkhem I, Seckl J and Lathe R: Cyp7b, a novel brain cytochrome P450, catalyzes the synthesis of neurosteroids 7alpha-hydroxy dehydroepiandrosterone and 7alpha-hydroxy pregnenolone. Proc Natl Acad Sci USA. 94:4925–4930. 1997. View Article : Google Scholar : PubMed/NCBI

14 

Dulos J, Verbraak E, Bagchus WM, Boots AM and Kaptein A: Severity of murine collagen-induced arthritis correlates with increased CYP7B activity: Enhancement of dehydroepiandrosterone metabolism by interleukin-1beta. Arthritis Rheum. 50:3346–3353. 2004. View Article : Google Scholar : PubMed/NCBI

15 

Rainey WE, Rehman KS and Carr BR: The human fetal adrenal: Making adrenal androgens for placental estrogens. Semin Reprod Med. 22:327–336. 2004. View Article : Google Scholar

16 

Kim SB, Hill M, Kwak YT, Hampl R, Jo DH and Morfin R: Neurosteroids: Cerebrospinal fluid levels for Alzheimer's disease and vascular dementia diagnostics. J Clin Endocrinol Metab. 88:5199–5206. 2003. View Article : Google Scholar : PubMed/NCBI

17 

Katyare SS, Modi HR and Patel MA: Dehydroepiandrosterone treatment alters lipid/phospholipid profiles of rat brain and liver mitochondria. Curr Neurovasc Res. 3:273–279. 2006. View Article : Google Scholar : PubMed/NCBI

18 

Mayer D and Forstner K: Impact of dehydroepiandrosterone on hepatocarcinogenesis in the rat (Review). Int J Oncol. 25:1021–1030. 2004.PubMed/NCBI

19 

Nelson ER, Wardell SE, Jasper JS, Park S, Suchindran S, Howe MK, Carver NJ, Pillai RV, Sullivan PM, Sondhi V, et al: 27-Hydroxycholesterol links hypercholesterolemia and breast cancer pathophysiology. Science. 342:1094–1098. 2013. View Article : Google Scholar : PubMed/NCBI

20 

Wu Q, Ishikawa T, Sirianni R, Tang H, McDonald JG, Yuhanna IS, Thompson B, Girard L, Mineo C, Brekken RA, et al: 27-Hydroxycholesterol promotes cell-autonomous, ER-positive breast cancer growth. Cell Rep. 5:637–645. 2013. View Article : Google Scholar : PubMed/NCBI

21 

Anderson DM, Anderson KM, Chang CL, Makarewich CA, Nelson BR, McAnally JR, Kasaragod P, Shelton JM, Liou J, Bassel-Duby R and Olson EN: A micropeptide encoded by a putative long noncoding RNA regulates muscle performance. Cell. 160:595–606. 2015. View Article : Google Scholar : PubMed/NCBI

22 

Esquela-Kerscher A and Slack FJ: Oncomirs - microRNAs with a role in cancer. Nat Rev Cancer. 6:259–269. 2006. View Article : Google Scholar : PubMed/NCBI

23 

Rossi JJ: New hope for a microRNA therapy for liver cancer. Cell. 137:990–992. 2009. View Article : Google Scholar : PubMed/NCBI

24 

Kota J, Chivukula RR, O'Donnell KA, Wentzel EA, Montgomery CL, Hwang HW, Chang TC, Vivekanandan P, Torbenson M, Clark KR, et al: Therapeutic microRNA delivery suppresses tumorigenesis in a murine liver cancer model. Cell. 137:1005–1017. 2009. View Article : Google Scholar : PubMed/NCBI

25 

Zuo JH, Zhu W, Li MY, Li XH, Yi H, Zeng GQ, Wan XX, He QY, Li JH, Qu JQ, et al: Activation of EGFR promotes squamous carcinoma SCC10A cell migration and invasion via inducing EMT-like phenotype change and MMP-9-mediated degradation of E-cadherin. J Cell Biochem. 112:2508–2517. 2011. View Article : Google Scholar : PubMed/NCBI

26 

Jung H, Lee KP, Park SJ, Park JH, Jang YS, Choi SY, Jung JG, Jo K, Park DY, Yoon JH, et al: TMPRSS4 promotes invasion, migration and metastasis of human tumor cells by facilitating an epithelial-mesenchymal transition. Oncogene. 27:2635–2647. 2008. View Article : Google Scholar

27 

Christiansen JJ and Rajasekaran AK: Reassessing epithelial to mesenchymal transition as a prerequisite for carcinoma invasion and metastasis. Cancer Res. 66:8319–8326. 2006. View Article : Google Scholar : PubMed/NCBI

28 

Kurrey NK, Jalgaonkar SP, Joglekar AV, Ghanate AD, Chaskar PD, Doiphode RY and Bapat SA: Snail and slug mediate radioresistance and chemoresistance by antagonizing p53-mediated apoptosis and acquiring a stem-like phenotype in ovarian cancer cells. Stem Cells. 27:2059–2068. 2009. View Article : Google Scholar : PubMed/NCBI

29 

Mani SA, Guo W, Liao MJ, Eaton EN, Ayyanan A, Zhou AY, Brooks M, Reinhard F, Zhang CC, Shipitsin M, et al: The epithelial-mesenchymal transition generates cells with properties of stem cells. Cell. 133:704–715. 2008. View Article : Google Scholar : PubMed/NCBI

30 

Morel AP, Lièvre M, Thomas C, Hinkal G, Ansieau S and Puisieux A: Generation of breast cancer stem cells through epithelial-mesenchymal transition. PLoS One. 3:e28882008. View Article : Google Scholar : PubMed/NCBI

31 

Santisteban M, Reiman JM, Asiedu MK, Behrens MD, Nassar A, Kalli KR, Haluska P, Ingle JN, Hartmann LC, Manjili MH, et al: Immune-induced epithelial to mesenchymal transition in vivo generates breast cancer stem cells. Cancer Res. 69:2887–2895. 2009. View Article : Google Scholar : PubMed/NCBI

32 

Du L, Wang H, He L, Zhang J, Ni B, Wang X, Jin H, Cahuzac N, Mehrpour M, Lu Y and Chen Q: CD44 is of functional importance for colorectal cancer stem cells. Clin Cancer Res. 14:6751–6760. 2008. View Article : Google Scholar : PubMed/NCBI

33 

Bartel DP: MicroRNAs: Genomics, biogenesis, mechanism, and function. Cell. 116:281–297. 2004. View Article : Google Scholar : PubMed/NCBI

34 

Diosdado B, van de Wiel MA, Terhaar Sive Droste JS, Mongera S, Postma C, Meijerink WJ, Carvalho B and Meijer GA: MiR-17-92 cluster is associated with 13q gain and c-myc expression during colorectal adenoma to adenocarcinoma progression. Br J Cancer. 101:707–714. 2009. View Article : Google Scholar : PubMed/NCBI

35 

Monzo M, Navarro A, Bandres E, Artells R, Moreno I, Gel B, Ibeas R, Moreno J, Martinez F, Diaz T, et al: Overlapping expression of microRNAs in human embryonic colon and colorectal cancer. Cell Res. 18:823–833. 2008. View Article : Google Scholar : PubMed/NCBI

36 

Lanza G, Ferracin M, Gafà R, Veronese A, Spizzo R, Pichiorri F, Liu CG, Calin GA, Croce CM and Negrini M: mRNA/microRNA gene expression profile in microsatellite unstable colorectal cancer. Mol Cancer. 6:542007. View Article : Google Scholar : PubMed/NCBI

37 

Schetter AJ, Leung SY, Sohn JJ, Zanetti KA, Bowman ED, Yanaihara N, Yuen ST, Chan TL, Kwong DL, Au GK, et al: MicroRNA expression profiles associated with prognosis and therapeutic outcome in colon adenocarcinoma. JAMA. 299:425–436. 2008. View Article : Google Scholar : PubMed/NCBI

38 

Motoyama K, Inoue H, Takatsuno Y, Tanaka F, Mimori K, Uetake H, Sugihara K and Mori M: Over- and under-expressed microRNAs in human colorectal cancer. Int J Oncol. 34:1069–1075. 2009.PubMed/NCBI

39 

Jiang H, Wang P, Wang Q, Wang B, Mu J, Zhuang X, Zhang L, Yan J, Miller D and Zhang HG: Quantitatively controlling expression of miR-17-92 determines colon tumor progression in a mouse tumor model. Am J Pathol. 184:1355–1368. 2014. View Article : Google Scholar : PubMed/NCBI

40 

Yu G, Tang JQ, Tian ML, Li H, Wang X, Wu T, Zhu J, Huang SJ and Wan YL: Prognostic values of the miR-17-92 cluster and its paralogs in colon cancer. J Surg Oncol. 106:232–237. 2012. View Article : Google Scholar

41 

Olsson M, Gustafsson O, Skogastierna C, Tolf A, Rietz BD, Morfin R, Rane A and Ekström L: Regulation and expression of human CYP7B1 in prostate: Overexpression of CYP7B1 during progression of prostatic adenocarcinoma. Prostate. 67:1439–1446. 2007. View Article : Google Scholar : PubMed/NCBI

42 

Tang W and Norlin M: Regulation of steroid hydroxylase CYP7B1 by androgens and estrogens in prostate cancer LNCaP cells. Biochem Biophys Res Commun. 344:540–546. 2006. View Article : Google Scholar : PubMed/NCBI

Related Articles

Journal Cover

August-2016
Volume 38 Issue 2

Print ISSN: 1107-3756
Online ISSN:1791-244X

Sign up for eToc alerts

Recommend to Library

Copy and paste a formatted citation
x
Spandidos Publications style
Xi XP, Zhuang J, Teng MJ, Xia LJ, Yang MY, Liu QG and Chen JB: MicroRNA-17 induces epithelial-mesenchymal transition consistent with the cancer stem cell phenotype by regulating CYP7B1 expression in colon cancer. Int J Mol Med 38: 499-506, 2016.
APA
Xi, X., Zhuang, J., Teng, M., Xia, L., Yang, M., Liu, Q., & Chen, J. (2016). MicroRNA-17 induces epithelial-mesenchymal transition consistent with the cancer stem cell phenotype by regulating CYP7B1 expression in colon cancer. International Journal of Molecular Medicine, 38, 499-506. https://doi.org/10.3892/ijmm.2016.2624
MLA
Xi, X., Zhuang, J., Teng, M., Xia, L., Yang, M., Liu, Q., Chen, J."MicroRNA-17 induces epithelial-mesenchymal transition consistent with the cancer stem cell phenotype by regulating CYP7B1 expression in colon cancer". International Journal of Molecular Medicine 38.2 (2016): 499-506.
Chicago
Xi, X., Zhuang, J., Teng, M., Xia, L., Yang, M., Liu, Q., Chen, J."MicroRNA-17 induces epithelial-mesenchymal transition consistent with the cancer stem cell phenotype by regulating CYP7B1 expression in colon cancer". International Journal of Molecular Medicine 38, no. 2 (2016): 499-506. https://doi.org/10.3892/ijmm.2016.2624