Cyp24a1 Attenuation Limits Progression of Brafv600e-Induced Papillary Thyroid Cancer Cells and Sensitizes Them to BRAFV600E Inhibitor PLX4720 Minjing Zou1, Essa Y
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Published OnlineFirst February 27, 2017; DOI: 10.1158/0008-5472.CAN-16-2066 Cancer Tumor and Stem Cell Biology Research Cyp24a1 Attenuation Limits Progression of BrafV600E-Induced Papillary Thyroid Cancer Cells and Sensitizes Them to BRAFV600E Inhibitor PLX4720 Minjing Zou1, Essa Y. Baitei1, Huda A. BinEssa1, Futwan A. Al-Mohanna2, Ranjit S. Parhar2,ReneSt-Arnaud3, Shioko Kimura4, Catrin Pritchard5, Ali S. Alzahrani6, Abdullah M. Assiri7, Brian F. Meyer1, and Yufei Shi1 Abstract CYP24A1, the primary inactivating enzyme for vitamin D, is nocompromised nude mice. This phenotype was associated with often overexpressed in human cancers, potentially neutralizing the downregulation of the MAPK, PI3K/Akt, and TGFb signaling path- antitumor effects of calcitriol, the active form of vitamin D. How- ways and a loss of epithelial–mesenchymal transition (EMT) in ever, it is unclear whetherCYP24A1expression serves asa functional BVECyp24a1-null cells, associated with downregulation of genes contributor versus only a biomarker for tumor progression. In this involved in EMT, tumor invasion, and metastasis. While calcitriol study, we investigated the role of CYP24A1 on malignant progres- treatment did not decrease cell proliferation in BVECyp24a1-null cells, sion of a murine model of BrafV600E-induced papillary thyroid it strengthened antitumor responses to the BRAFV600E inhibitor cancer (PTC). Mice harboring wild-type Cyp24a1 (BVECyp24a1-wt) PLX4720 in both BVECyp24a1-null and BVECyp24a1-wt cells. Our find- developed PTC at 5 weeks of age. Mice harboring a homozygous ings offer direct evidence that Cyp24a1 functions as an oncogene in deletion of Cyp24a1 (BVECyp24a1-null) exhibited a 4-fold reduction PTC, where its overexpression activates multiple signaling cascades in tumor growth. Notably, we found the tumorigenic potential of to promote malignant progression and resistance to PLX4720 BVECyp24a1-null-derived tumor cells to be nearly abolished in immu- treatment. Cancer Res; 77(8); 2161–72. Ó2017 AACR. Introduction Vitamin D is mainly involved in bone and mineral metabolism. It has other important functions, such as the modulation of cell Papillary thyroid cancer (PTC) is the most common type of growth and immune function (5). Its antiproliferative effects have thyroid cancer, accounting for more than 80% of thyroid cancer attracted great enthusiasm in recent years for its potential appli- cases (1). The BRAFV600E mutation is the most frequent genetic cation as an anticancer agent. Significant antiproliferative effects alteration in PTC, occurring in 28% to 83% of cases with an have been observed in many human cancer cells, including average rate of 44% (2–4). Constitutive activation of the RAS– thyroid, prostate, breast, colorectal, and lung cancers (6–9). RAF–MEK–ERK MAP kinase signaling pathway (MAPK) promotes Vitamin D receptor (VDR) knockout mice displayed a higher the initiation and progression of PTC. incidence of carcinogen-induced breast and skin tumors (10), and vitamin D deficiency promotes human breast cancer growth (11). Although clinical trials have shown the potential therapeutic 1Department of Genetics, King Faisal Specialist Hospital and Research Centre, effects of calcitriol in prostate cancer patients (12), the success has Riyadh, Saudi Arabia. 2Department of Cell Biology, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia. 3Department of Surgery not been convincing regarding the clinical effects of vitamin D or and Human Genetics, McGill University, Montreal, Quebec, Canada; and Research its analogues in cancer treatment (13, 14). This may be due to the Centre, Shriners Hospitals for Children, Montreal, Quebec, Canada. 4Laboratory overexpression of CYP24A1 in many cancer patients. of Metabolism, National Cancer Institute, National Institutes of Health, Bethesda, Vitamin D 24-hydroxylase (CYP24A1) is the primary vitamin Maryland. 5Department of Biochemistry, University of Leicester, Lancaster Road, D-inactivating enzyme, which catabolizes 1a, 25(OH)2D3 (calci- Leicester, UK. 6Department of Medicine, King Faisal Specialist Hospital and 7 triol) and, to a lesser extent, 25(OH)2D3 by 24 hydroxylation into Research Centre, Riyadh, Saudi Arabia. Department of Comparative Medicine, a King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia. inactive 1 , 24,25(OH)3D3 and 24,25(OH)2D3 (6). The calci- triol-mediated antiproliferative effects could be disrupted by Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/). CYP24A1 overexpression during tumor development (7). Indeed, CYP24A1 overexpression has been observed in many cancers, M. Zou and E.Y. Baitei contributed equally to this article. including thyroid (15, 16), lung (17), colon (18), esophageal Corresponding Author: Yufei Shi, King Faisal Specialist Hospital and Research (19), and breast (20), and has been linked to poor prognosis in Centre, MBC#3, P.O. Box 3354, Riyadh 11211, Saudi Arabia. Phone: 966-1-442- patients with lung (21), esophageal (19), colon (22), and thyroid 4768; Fax: 966-1-442-4585; E-mail: [email protected] (16, 23) cancers. It has been proposed as a candidate oncogene doi: 10.1158/0008-5472.CAN-16-2066 due to its gene amplification in breast cancer (24). In patients Ó2017 American Association for Cancer Research. with thyroid cancer, the serum calcitriol level was found to be www.aacrjournals.org 2161 Downloaded from cancerres.aacrjournals.org on September 25, 2021. © 2017 American Association for Cancer Research. Published OnlineFirst February 27, 2017; DOI: 10.1158/0008-5472.CAN-16-2066 Zou et al. significantly lower (25), although there was no significant differ- allele of 250 bp, and primers 1 þ 3 detected the mutant allele ence in the serum 25(OH) D3 level between thyroid nodule and of 600 bp. The PCR conditions were as follows: 94 C for 5 minutes thyroid cancer patients (25, 26), indicating that calcitriol might be followed by 35 cycles of amplification (94C for 30 seconds, 58C converted to inactive 1a, 24,25(OH)3D3 by increased CYP24A1 for 30 seconds, 72 C for 1 minutes) with a final extension at 72 C expression. Although these data suggest that CYP24A1 overexpres- for 10 minutes. sion could result in the abrogation of calcitriol-mediated growth arrest leading to tumor development and/or progression, there are Establishment of thyroid tumor cell lines no in vivo functional studies to support this hypothesis. Thyroid tumors were collected aseptically from donor mice In our previous study, we demonstrated that CYP24A1 over- (BVECyp24a1-wt and BVECyp24a1-null) using blunt dissection, then V600E expression was associated with BRAF mutation and advanced mechanically dissociated by mincing and passing through a 40- V600E stages of PTC (23). We also showed that BRAF induced mm/mesh sterile screen, and suspended in DMEM/F12 growth V600E CYP24A1 overexpression and the BRAF inhibitor PLX4720 medium (10% fetal bovine serum, 100 units/mL penicillin, 100 fi signi cantly enhanced the antiproliferative effects of calcitriol in mg/mL streptomycin). The cells were further dissociated by incu- thyroid cancer cell lines (23). However, it is not clear to what extent bation in growth medium containing 100 U/mL type I collage- CYP24A1 overexpression contributes to thyroid cancer develop- nase (Sigma-Aldrich) and 1.0 U/mL dispase I (Roche Diagnostics) ment and progression in vivo, especially in the presence of at 37C in a rocking water bath for 60 minutes. The cell suspension V600E BRAF . In the present study, we used a mouse model of was washed twice with growth media and resuspended in a 10- V600E Braf -induced PTC to investigate the role of Cyp24a1 in thyroid mm culture dish with DMEM/F12 growth medium containing 4 cancer progression. We observed that thyroid cancer growth was mU/mL bovine TSH (Sigma-Aldrich) to establish BVECyp24a1-wt fi signi cantly reduced in the absence of Cyp24a1 expression. and BVECyp24a1-null cell lines. The established cell lines were propagated in DMEM/Ham's F12 growth medium. Two cell Materials and Methods lines were established each from two separate BVECyp24a1-wt or BVECyp24a1-null primary thyroid tumors in 2015: BVECyp24a1-wt-1, Animals BVECyp24a1-wt-2, BVECyp24a1-null-1, and BVECyp24a1-null-2. The thy- – V600E The generation of TPO Braf and Cyp24a1 knockout mice roid origin of these cell lines was confirmed by genotyping in the (Cyp24a1null) have been described previously (27–29). TPO- V600E Cyp24a1-wt lab as described above, which was performed 1 month before Braf mice with wild-type Cyp24a1 (BVE ) developed using the cell lines. PTC at approximately 5 weeks of age and were used as PTC tumor controls. TPO-BrafWT mice with wild-type Cyp24a1 were used as Cyp24a1 normal controls. TPO-BrafV600E mice with Cyp24a1 knockout Quantitative real-time RT-PCR analysis for expression (BVECyp24a1-null) were obtained by several rounds of breeding Total RNA was isolated from the thyroid tumor tissues of þ À Cyp24a1-wt Cyp24a1-null among LSL-BrafV600E(30) TPO-Cre (31), and Cyp24a1 / mice. BVE mice and BVE mice by the quanidinium – – Because 50% of the homozygous mutant Cyp24a1null mice died thiocyanate phenol chloroform method (32). The integrity of fi before 3 weeks of age (29), the mice were kept in a heterozygous the RNA was veri ed by denaturing gel electrophoresis. Two þ À m state (Cyp24a1 / ). To knockout Cyp24a1 in TPO–BrafV600E mice, micrograms ( g) of each total RNA was reverse-transcribed to þ À Cyp24a1 / mice were first crossed with LSL–BrafV600E or TPO– cDNA using the Promega RT system (Promega). The LightCycler þ À Cre mice to generate a Cyp24a1 / ; BrafV600E strain or TPO–Cre; DNA Master SYBR Green 1 Kit was used for quantitative real-time þ À þ À m Cyp24a1 / strain. Cyp24a1 / ; BrafV600E mice and TPO–Cre; PCR analysis (33). The cDNA mix was diluted 10-fold, and 2 Lof þ/À – the dilution was used for real-time PCR analysis. The PCR primers Cyp24a1 mice were then bred together to create TPO 0 V600E– À/À or null for the 126-bp Cyp24a1 cDNA fragment were: 5 -CATCGCAAC- Braf Cyp24a1 mice.