BACKGROUND: A detailed analysis of the expression of 440 cancer-related genes was performed after the combined treatment of medulloblastoma cells with all-trans retinoic acid (ATRA) and inhibitors of lipoxygenases (LOX) and cyclooxygenases (COX). The combinations of retinoids and celecoxib as a COX-2 inhibitor were reported to be effective in some regimens of metronomic therapy of relapsed solid tumors with poor prognosis. Our previous findings on neuroblastoma cells using expression profiling showed that LOX/COX inhibitors have the capability of enhancing the differentiating action of ATRA. Presented study focused on the continuation of our previous work to confirm the possibility of enhancing ATRA-induced cell differentiation in these cell lines via the application of LOX/COX inhibitors. This study provides more detailed information concerning the mechanisms of the enhancement of the ATRA-induced differentiation of medulloblastoma cells. METHODS: The Daoy and D283 Med medulloblastoma cell lines were chosen for this study. Caffeic acid (an inhibitor of 5-LOX) and celecoxib (an inhibitor on COX-2) were used in combined treatment with ATRA. The expression profiling was performed using Human Cancer Oligo GEArray membranes, and the most promising results were verified using RT-PCR. RESULTS: The expression profiling of the selected cancer-related genes clearly confirmed that the differentiating effects of ATRA should be enhanced via its combined administration with caffeic acid or celecoxib. This effect was detected in both cell lines. An increased expression of the genes that encoded the proteins participating in induced differentiation and cytoskeleton remodeling was detected in both cell lines in a concentration-dependent manner. This effect was also observed for the CDKN1A gene encoding the p21 protein, which is an important regulator of the cell cycle, and for the genes encoding proteins that are associated with proteasome activity. Furthermore, our results showed that D283 Med cells are significantly more sensitive to treatment with ATRA alone than Daoy cells. CONCLUSIONS: The obtained results on medulloblastoma cell lines are in accordance with our previous findings on neuroblastoma cells and confirm our hypothesis concerning the common mechanism of the enhancement of ATRA-induced cell differentiation in various types of pediatric solid tumors.

Department of Experimental Biology Laboratory of Tumor Biology School of Science Masaryk University Kotlarska 2 611 37 Brno Czech Republic

Department of Experimental Biology Laboratory of Tumor Biology School of Science Masaryk University Kotlarska 2 611 37 Brno Czech Republic ; Department of Pediatric Oncology University Hospital Brno and School of Medicine Masaryk University Cernopolni 9 613 00 Brno Czech Republic

Department of Experimental Biology Laboratory of Tumor Biology School of Science Masaryk University Kotlarska 2 611 37 Brno Czech Republic ; Masaryk Memorial Cancer Institute Zluty kopec 7 656 53 Brno Czech Republic

Department of Pediatric Oncology University Hospital Brno and School of Medicine Masaryk University Cernopolni 9 613 00 Brno Czech Republic ; Masaryk Memorial Cancer Institute Zluty kopec 7 656 53 Brno Czech Republic

Zobrazit více v PubMed

Gerber NU, Mynarek M, von Hoff K, Friedrich C, Resch A, Rutkowski S. Recent developments and current concepts in medulloblastoma. Cancer Treat Rev. 2014;40:356–365. doi: 10.1016/j.ctrv.2013.11.010. PubMed DOI

Massimino M, Giangaspero F, Garre ML, Gandola L, Poggi G, Biassoni V, Gatta G, Rutkowski S. Childhood medulloblastoma. Crit Rev Oncol Hematol. 2011;79:65–83. doi: 10.1016/j.critrevonc.2010.07.010. PubMed DOI

Dragnev KH, Petty WJ, Dmitrovsky E. Retinoid targets in cancer therapy and chemoprevention. Cancer Biol Ther. 2003;2:S150–S156. PubMed

Brtko J, Dvorak Z. Role of retinoids, rexinoids and thyroid hormone in the expression of cytochrome p450 enzymes. Curr Drug Metab. 2011;12:71–88. doi: 10.2174/138920011795016881. PubMed DOI

Dedieu S, Lefebvre P. Retinoids interfere with the AP1 signalling pathway in human breast cancer cells. Cell Signal. 2006;18:889–898. doi: 10.1016/j.cellsig.2005.08.001. PubMed DOI

Masia S, Alvarez S, de Lera AR, Barettino D. Rapid, nongenomic actions of retinoic acid on phosphatidylinositol-3-kinase signaling pathway mediated by the retinoic acid receptor. Mol Endocrinol. 2007;21:2391–2402. doi: 10.1210/me.2007-0062. PubMed DOI

Cruz FD, Matushansky I. Solid tumor differentiation therapy - is it possible? Oncotarget. 2012;3:559–567. PubMed PMC

Hallahan AR, Pritchard JI, Chandraratna RA, Ellenbogen RG, Geyer JR, Overland RP, Strand AD, Tapscott SJ, Olson JM. BMP-2 mediates retinoid-induced apoptosis in medulloblastoma cells through a paracrine effect. Nat Med. 2003;9:1033–1038. doi: 10.1038/nm904. PubMed DOI

Garattini E, Gianni M, Terao M. Retinoids as differentiating agents in oncology: a network of interactions with intracellular pathways as the basis for rational therapeutic combinations. Curr Pharm Des. 2007;13:1375–1400. doi: 10.2174/138161207780618786. PubMed DOI

Andres D, Keyser BM, Petrali J, Benton B, Hubbard KS, McNutt PM, Ray R. Morphological and functional differentiation in BE(2)-M17 human neuroblastoma cells by treatment with Trans-retinoic acid. BMC Neurosci. 2013;14:49. doi: 10.1186/1471-2202-14-49. PubMed DOI PMC

Maurer BJ, Kang MH, Villablanca JG, Janeba J, Groshen S, Matthay KK, Sondel PM, Maris JM, Jackson HA, Goodarzian F, Shimada H, Czarnecki S, Hasenauer B, Reynolds CP, Marachelian A. Phase I trial of fenretinide delivered orally in a novel organized lipid complex in patients with relapsed/refractory neuroblastoma: a report from the New Approaches to Neuroblastoma Therapy (NANT) consortium. Pediatr Blood Cancer. 2013;60:1801–1808. doi: 10.1002/pbc.24643. PubMed DOI PMC

Patatanian E, Thompson DF. Retinoic acid syndrome: a review. J Clin Pharm Ther. 2008;33:331–338. doi: 10.1111/j.1365-2710.2008.00935.x. PubMed DOI

Kuendgen A, Gattermann N. Valproic acid for the treatment of myeloid malignancies. Cancer. 2007;110:943–954. doi: 10.1002/cncr.22891. PubMed DOI

Tomita A, Kiyoi H, Naoe T. Mechanisms of action and resistance to all-trans retinoic acid (ATRA) and arsenic trioxide (As2O 3) in acute promyelocytic leukemia. Int J Hematol. 2013;97:717–725. doi: 10.1007/s12185-013-1354-4. PubMed DOI

Nowak D, Stewart D, Koeffler HP. Differentiation therapy of leukemia: 3 decades of development. Blood. 2009;113:3655–3665. doi: 10.1182/blood-2009-01-198911. PubMed DOI PMC

Lo-Coco F, Avvisati G, Vignetti M, Thiede C, Orlando SM, Iacobelli S, Ferrara F, Fazi P, Cicconi L, di Bona E, Specchia G, Sica S, Divona M, Levis A, Fiedler W, Cerqui E, Breccia M, Fioritoni G, Salih HR, Cazzola M, Melillo L, Carella AM, Brandts CH, Morra E, von Lilienfeld-Toal M, Hertenstein B, Wattad M, Lübbert M, Hänel M, Schmitz N. et al.Retinoic acid and arsenic trioxide for acute promyelocytic leukemia. N Engl J Med. 2013;369:111–121. doi: 10.1056/NEJMoa1300874. PubMed DOI

Haque A, Banik NL, Ray SK. Emerging role of combination of all-trans retinoic acid and interferon-gamma as chemoimmunotherapy in the management of human glioblastoma. Neurochem Res. 2007;32:2203–2209. doi: 10.1007/s11064-007-9420-z. PubMed DOI

De los Santos M, Zambrano A, Aranda A. Combined effects of retinoic acid and histone deacetylase inhibitors on human neuroblastoma SH-SY5Y cells. Mol Cancer Ther. 2007;6:1425–1432. doi: 10.1158/1535-7163.MCT-06-0623. PubMed DOI

Frumm SM, Fan ZP, Ross KN, Duvall JR, Gupta S, VerPlank L, Suh BC, Holson E, Wagner FF, Smith WB, Paranal RM, Bassil CF, Qi J, Roti G, Kung AL, Bradner JE, Tolliday N, Stegmaier K. Selective HDAC1/HDAC2 inhibitors induce neuroblastoma differentiation. Chem Biol. 2013;20:713–725. doi: 10.1016/j.chembiol.2013.03.020. PubMed DOI PMC

Chlapek P, Redova M, Zitterbart K, Hermanova M, Sterba J, Veselska R. Enhancement of ATRA-induced differentiation of neuroblastoma cells with LOX/COX inhibitors: an expression profiling study. J Exp Clin Cancer Res. 2010;29:45. doi: 10.1186/1756-9966-29-45. PubMed DOI PMC

Avis I, Martinez A, Tauler J, Zudaire E, Mayburd A, Abu-Ghazaleh R, Ondrey F, Mulshine JL. Inhibitors of the arachidonic acid pathway and peroxisome proliferator-activated receptor ligands have superadditive effects on lung cancer growth inhibition. Cancer Res. 2005;65:4181–4190. doi: 10.1158/0008-5472.CAN-04-3441. PubMed DOI

Kuo HC, Kuo WH, Lee YJ, Wang CJ, Tseng TH. Enhancement of caffeic acid phenethyl ester on all-trans retinoic acid-induced differentiation in human leukemia HL-60 cells. Toxicol Appl Pharmacol. 2006;216:80–88. doi: 10.1016/j.taap.2006.04.007. PubMed DOI

Veselska R, Zitterbart K, Auer J, Neradil J. Differentiation of HL-60 myeloid leukemia cells induced by all-trans retinoic acid is enhanced in combination with caffeic acid. Int J Mol Med. 2004;14:305–310. PubMed

Bell E, Ponthan F, Whitworth C, Westermann F, Thomas H, Redfern CP. Cell Survival Signalling through PPARdelta and Arachidonic Acid Metabolites in Neuroblastoma. PLoS One. 2013;8:e68859. doi: 10.1371/journal.pone.0068859. PubMed DOI PMC

Schroeder CP, Kadara H, Lotan D, Woo JK, Lee HY, Hong WK, Lotan R. Involvement of mitochondrial and Akt signaling pathways in augmented apoptosis induced by a combination of low doses of celecoxib and N-(4-hydroxyphenyl) retinamide in premalignant human bronchial epithelial cells. Cancer Res. 2006;66:9762–9770. doi: 10.1158/0008-5472.CAN-05-4124. PubMed DOI

Simeone AM, Li YJ, Broemeling LD, Johnson MM, Tuna M, Tari AM. Cyclooxygenase-2 is essential for HER2/neu to suppress N- (4-hydroxyphenyl) retinamide apoptotic effects in breast cancer cells. Cancer Res. 2004;64:1224–1228. doi: 10.1158/0008-5472.CAN-03-2188. PubMed DOI

Liu JP, Wei HB, Zheng ZH, Guo WP, Fang JF. Celecoxib increases retinoid sensitivity in human colon cancer cell lines. Cell Mol Biol Lett. 2010;15:440–450. doi: 10.2478/s11658-010-0016-2. PubMed DOI PMC

Soda M, Hu D, Endo S, Takemura M, Li J, Wada R, Ifuku S, Zhao HT, El-Kabbani O, Ohta S, Yamamura K, Toyooka N, Hara A, Matsunaga T. Design, synthesis and evaluation of caffeic acid phenethyl ester-based inhibitors targeting a selectivity pocket in the active site of human aldo-keto reductase 1B10. Eur J Med Chem. 2012;48:321–329. PubMed

Redova M, Chlapek P, Loja T, Zitterbart K, Hermanova M, Sterba J, Veselska R. Influence of LOX/COX inhibitors on cell differentiation induced by all-trans retinoic acid in neuroblastoma cell lines. Int J Mol Med. 2010;25:271–280. PubMed

Nardini M, Scaccini C, Packer L, Virgili F. In vitro inhibition of the activity of phosphorylase kinase, protein kinase C and protein kinase A by caffeic acid and a procyanidin-rich pine bark (Pinus marittima) extract. Biochim Biophys Acta. 2000;1474:219–225. doi: 10.1016/S0304-4165(00)00009-X. PubMed DOI

Dandekar DS, Lopez M, Carey RI, Lokeshwar BL. Cyclooxygenase-2 inhibitor celecoxib augments chemotherapeutic drug-induced apoptosis by enhancing activation of caspase-3 and -9 in prostate cancer cells. Int J Cancer. 2005;115:484–492. doi: 10.1002/ijc.20878. PubMed DOI

Kang KB, Zhu C, Yong SK, Gao Q, Wong MC. Enhanced sensitivity of celecoxib in human glioblastoma cells: Induction of DNA damage leading to p53-dependent G1 cell cycle arrest and autophagy. Mol Cancer. 2009;8:66. doi: 10.1186/1476-4598-8-66. PubMed DOI PMC

Graff J, Skarke C, Klinkhardt U, Watzer B, Harder S, Seyberth H, Geisslinger G, Nusing RM. Effects of selective COX-2 inhibition on prostanoids and platelet physiology in young healthy volunteers. J Thromb Haemost. 2007;5:2376–2385. doi: 10.1111/j.1538-7836.2007.02782.x. PubMed DOI

Gumireddy K, Sutton LN, Phillips PC, Reddy CD. All-trans-retinoic acid-induced apoptosis in human medulloblastoma: activation of caspase-3/poly(ADPribose) polymerase 1 pathway. Clin Cancer Res. 2003;9:4052–4059. PubMed

Vandesompele J, de Preter K, Pattyn F, Poppe B, van Roy N, de Paepe A, Speleman F. Accurate normalization of real-time quantitative RT-PCR data by geometric averaging of multiple internal control genes. Genome Biol. 2002;3:RESEARCH0034. PubMed PMC

Andersen CL, Jensen JL, Orntoft TF. Normalization of real-time quantitative reverse transcription-PCR data: a model-based variance estimation approach to identify genes suited for normalization, applied to bladder and colon cancer data sets. Cancer Res. 2004;64:5245–5250. doi: 10.1158/0008-5472.CAN-04-0496. PubMed DOI

Huang DW, Sherman BT, Lempicki RA. Systematic and integrative analysis of large gene lists using DAVID bioinformatics resources. Nat Protoc. 2009;4:44–57. PubMed

Schneider CA, Rasband WS, Eliceiri KW. NIH Image to ImageJ: 25 years of image analysis. Nat Methods. 2012;9:671–675. doi: 10.1038/nmeth.2089. PubMed DOI PMC

Reynolds CP, Lemons RS. Retinoid therapy of childhood cancer. Hematol Oncol Clin North Am. 2001;15:867–910. doi: 10.1016/S0889-8588(05)70256-2. PubMed DOI

Reynolds CP, Matthay KK, Villablanca JG, Maurer BJ. Retinoid therapy of high-risk neuroblastoma. Cancer Lett. 2003;197:185–192. doi: 10.1016/S0304-3835(03)00108-3. PubMed DOI

Sterba J. Contemporary therapeutic options for children with high risk neuroblastoma. Neoplasma. 2002;49:133–140. PubMed

Sterba J, Valik D, Mudry P, Kepak T, Pavelka Z, Bajciova V, Zitterbart K, Kadlecova V, Mazanek P. Combined biodifferentiating and antiangiogenic oral metronomic therapy is feasible and effective in relapsed solid tumors in children: single-center pilot study. Onkologie. 2006;29:308–313. doi: 10.1159/000093474. PubMed DOI

Zapletalova D, Andre N, Deak L, Kyr M, Bajciova V, Mudry P, Dubska L, Demlova R, Pavelka Z, Zitterbart K, Skotakova J, Husek K, Martincekova A, Mazanek P, Kepak T, Doubek M, Kutnikova L, Valik D, Sterba J. Metronomic chemotherapy with the COMBAT regimen in advanced pediatric malignancies: a multicenter experience. Oncology. 2012;82:249–260. doi: 10.1159/000336483. PubMed DOI

Redova M. PhD thesis. Masaryk University, Department of Experimental Biology; Brno 2010. Enhancement of differentiation inductors’ effect on the solid tumors model in vitro.

Bai RY, Staedtke V, Lidov HG, Eberhart CG, Riggins GJ. OTX2 represses myogenic and neuronal differentiation in medulloblastoma cells. Cancer Res. 2012;72:5988–6001. doi: 10.1158/0008-5472.CAN-12-0614. PubMed DOI PMC

David M, Petit D, Bertoglio J. Cell cycle regulation of Rho signaling pathways. Cell Cycle. 2012;11:3003–3010. doi: 10.4161/cc.21088. PubMed DOI PMC

Bustelo XR, Sauzeau V, Berenjeno IM. GTP-binding proteins of the Rho/Rac family: regulation, effectors and functions in vivo. Bioessays. 2007;29:356–370. doi: 10.1002/bies.20558. PubMed DOI PMC

Strelau J, Strzelczyk A, Rusu P, Bendner G, Wiese S, Diella F, Altick AL, von Bartheld CS, Klein R, Sendtner M, Unsicker K. Progressive postnatal motoneuron loss in mice lacking GDF-15. J Neurosci. 2009;29:13640–13648. doi: 10.1523/JNEUROSCI.1133-09.2009. PubMed DOI PMC

Mimeault M, Batra SK. Divergent molecular mechanisms underlying the pleiotropic functions of macrophage inhibitory cytokine-1 in cancer. J Cell Physiol. 2010;224:626–635. doi: 10.1002/jcp.22196. PubMed DOI PMC

Li PX, Wong J, Ayed A, Ngo D, Brade AM, Arrowsmith C, Austin RC, Klamut HJ. Placental transforming growth factor-beta is a downstream mediator of the growth arrest and apoptotic response of tumor cells to DNA damage and p53 overexpression. J Biol Chem. 2000;275:20127–20135. doi: 10.1074/jbc.M909580199. PubMed DOI

Yang H, Filipovic Z, Brown D, Breit SN, Vassilev LT. Macrophage inhibitory cytokine-1: a novel biomarker for p53 pathway activation. Mol Cancer Ther. 2003;2:1023–1029. PubMed

Ryningen A, Stapnes C, Paulsen K, Lassalle P, Gjertsen BT, Bruserud O. In vivo biological effects of ATRA in the treatment of AML. Expert Opin Investig Drugs. 2008;17:1623–1633. doi: 10.1517/13543784.17.11.1623. PubMed DOI

Luo P, Lin M, Chen Y, Yang B, He Q. Function of retinoid acid receptor alpha and p21 in all-trans-retinoic acid-induced acute T-lymphoblastic leukemia apoptosis. Leuk Lymphoma. 2009;50:1183–1189. doi: 10.1080/10428190902934936. PubMed DOI

Bao GC, Wang JG, Jong A. Increased p21 expression and complex formation with cyclin E/CDK2 in retinoid-induced pre-B lymphoma cell apoptosis. FEBS Lett. 2006;580:3687–3693. doi: 10.1016/j.febslet.2006.05.052. PubMed DOI

Lim JS, Park SH, Jang KL. All-trans retinoic acid induces cellular senescence by up-regulating levels of p16 and p21 via promoter hypomethylation. Biochem Biophys Res Commun. 2011;412:500–505. doi: 10.1016/j.bbrc.2011.07.130. PubMed DOI

Park SH, Lim JS, Jang KL. All-trans retinoic acid induces cellular senescence via upregulation of p16, p21, and p27. Cancer Lett. 2011;310:232–239. doi: 10.1016/j.canlet.2011.07.009. PubMed DOI

Wainwright LJ, Lasorella A, Iavarone A. Distinct mechanisms of cell cycle arrest control the decision between differentiation and senescence in human neuroblastoma cells. Proc Natl Acad Sci U S A. 2001;98:9396–9400. doi: 10.1073/pnas.161288698. PubMed DOI PMC

Liu Y, Encinas M, Comella JX, Aldea M, Gallego C. Basic helix-loop-helix proteins bind to TrkB and p21(Cip1) promoters linking differentiation and cell cycle arrest in neuroblastoma cells. Mol Cell Biol. 2004;24:2662–2672. doi: 10.1128/MCB.24.7.2662-2672.2004. PubMed DOI PMC

Marzinke MA, Clagett-Dame M. The all-trans retinoic acid (atRA)-regulated gene Calmin (Clmn) regulates cell cycle exit and neurite outgrowth in murine neuroblastoma (Neuro2a) cells. Exp Cell Res. 2012;318:85–93. doi: 10.1016/j.yexcr.2011.10.002. PubMed DOI

Qiao J, Paul P, Lee S, Qiao L, Josifi E, Tiao JR, Chung DH. PI3K/AKT and ERK regulate retinoic acid-induced neuroblastoma cellular differentiation. Biochem Biophys Res Commun. 2012;424:421–426. doi: 10.1016/j.bbrc.2012.06.125. PubMed DOI PMC

Son SH, Yu E, Ahn Y, Choi EK, Lee H, Choi J. Retinoic acid attenuates promyelocytic leukemia protein-induced cell death in breast cancer cells by activation of the ubiquitin-proteasome pathway. Cancer Lett. 2007;247:213–223. doi: 10.1016/j.canlet.2006.04.005. PubMed DOI

Isakson P, Bjoras M, Boe SO, Simonsen A. Autophagy contributes to therapy-induced degradation of the PML/RARA oncoprotein. Blood. 2010;116:2324–2331. doi: 10.1182/blood-2010-01-261040. PubMed DOI

Trocoli A, Mathieu J, Priault M, Reiffers J, Souquere S, Pierron G, Besancon F, Djavaheri-Mergny M. ATRA-induced upregulation of Beclin 1 prolongs the life span of differentiated acute promyelocytic leukemia cells. Autophagy. 2011;7:1108–1114. doi: 10.4161/auto.7.10.16623. PubMed DOI PMC

Ferry C, Gaouar S, Fischer B, Boeglin M, Paul N, Samarut E, Piskunov A, Pankotai-Bodo G, Brino L, Rochette-Egly C. Cullin 3 mediates SRC-3 ubiquitination and degradation to control the retinoic acid response. Proc Natl Acad Sci U S A. 2011;108:20603–20608. doi: 10.1073/pnas.1102572108. PubMed DOI PMC

Day IN, Thompson RJ. UCHL1 (PGP 9.5): neuronal biomarker and ubiquitin system protein. Prog Neurobiol. 2010;90:327–362. doi: 10.1016/j.pneurobio.2009.10.020. PubMed DOI

Schneider L, Giordano S, Zelickson BR, SJ M, AB G, Ouyang X, Fineberg N, Darley-Usmar VM, Zhang J. Differentiation of SH-SY5Y cells to a neuronal phenotype changes cellular bioenergetics and the response to oxidative stress. Free Radic Biol Med. 2011;51:2007–2017. doi: 10.1016/j.freeradbiomed.2011.08.030. PubMed DOI PMC

Xun Z, Lee DY, Lim J, Canaria CA, Barnebey A, Yanonne SM, McMurray CT. Retinoic acid-induced differentiation increases the rate of oxygen consumption and enhances the spare respiratory capacity of mitochondria in SH-SY5Y cells. Mech Ageing Dev. 2012;133:176–185. doi: 10.1016/j.mad.2012.01.008. PubMed DOI PMC

Malik PS, Raina V, Andre N. Metronomics as maintenance treatment in oncology: time for chemo-switch. Front Oncol. 2014. epub ahead of print, doi: 10.3389/fonc.2014.00076. PubMed PMC

Choi LMR, Rood B, Kamani N, La Fond D, Packer RJ, Santi MR, MacDonald TJ. Feasibility of metronomic maintenance chemotherapy following high-dose chemotherapy for malignant central nervous system tumors. Pediatr Blood Cancer. 2008;50:970–975. doi: 10.1002/pbc.21381. PubMed DOI

Sterba J, Pavelka Z, Andre N, Ventruba J, Skotakova J, Bajciova V, Bronisova D, Dubska L, Valik D. Second complete remission of relapsed medulloblastoma induced by metronomic chemotherapy. Pediatr Blood Cancer. 2010;54:616–617. PubMed

Jaganathan SK, Mandal M. Antiproliferative effects of honey and of its polyphenols: a review. J Biomed Biotechnol. 2009;2009:830616. PubMed PMC

Korkina LG. Phenylpropanoids as naturally occurring antioxidants: from plant defense to human health. Cell Mol Biol (Noisy-le-Grand) 2007;53:15–25. PubMed

Enhanced Antiproliferative Effect of Combined Treatment with Calcitriol and All-Trans Retinoic Acid in Relation to Vitamin D Receptor and Retinoic Acid Receptor α Expression in Osteosarcoma Cell Lines

Why Differentiation Therapy Sometimes Fails: Molecular Mechanisms of Resistance to Retinoids