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Associations between genetic polymorphisms of membrane transporter genes and prognosis after chemotherapy: meta-analysis and finding from Seoul Breast Cancer Study (SEBCS)

The Pharmacogenomics Journalvolume 18pages633645 (2018) | Download Citation

Abstract

Membrane transporters can be major determinants of the pharmacokinetic profiles of anticancer drugs. The associations between genetic variations of ATP-binding cassette (ABC) and solute carrier (SLC) genes and cancer survival were investigated through a meta-analysis and an association study in the Seoul Breast Cancer Study (SEBCS). Including the SEBCS, the meta-analysis was conducted among 38 studies of genetic variations of transporters on various cancer survivors. The population of SEBCS consisted of 1338 breast cancer patients who had been treated with adjuvant chemotherapy. A total of 7750 SNPs were selected from 453 ABC and/or SLC genes typed by an Affymetrix 6.0 chip. ABCB1 rs1045642 was associated with poor progression-free survival in a meta-analysis (HR = 1.33, 95% CI: 1.07–1.64). ABCB1, SLC8A1, and SLC12A8 were associated with breast cancer survival in SEBCS (Pgene < 0.05). ABCB1 rs1202172 was differentially associated with survival depending on the chemotherapy (Pinteraction = 0.035). Our finding provides suggestive associations of membrane transporters on cancer survival.

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References

  1. 1.

    Youlden DR, Cramb SM, Yip CH, Baade PD. Incidence and mortality of female breast cancer in the Asia-Pacific region. Cancer Biol Med. 2014;11:101–15.

  2. 2.

    Oh CM, Won YJ, Jung KW, Kong HJ, Cho H, Lee JK, et al. Cancer statistics in Korea: incidence, mortality, survival, and prevalence in 2013. Cancer Res Treat. 2016;48:436–50.

  3. 3.

    Stearns V, Davidson NE, Flockhart DA. Pharmacogenetics in the treatment of breast cancer. Pharmacogenomics J. 2004;4:143–53.

  4. 4.

    Chen G, Quan S, Hu Q, Wang L, Xia X, Wu J. Lack of association between MDR1 C3435T polymorphism and chemotherapy response in advanced breast cancer patients: evidence from current studies. Mol Biol Rep. 2012;39:5161–8.

  5. 5.

    Berry DA, Cronin KA, Plevritis SK, Fryback DG, Clarke L, Zelen M, et al. Effect of screening and adjuvant therapy on mortality from breast cancer. N Engl J Med. 2005;353:1784–92.

  6. 6.

    Han SM, Park J, Lee JH, Lee SS, Kim H, Han H, et al. Targeted Next-Generation Sequencing for Comprehensive Genetic Profiling of Pharmacogenes. Clin Pharmacol Ther. 2017;101:396–405.

  7. 7.

    Daly AK. Genome-wide association studies in pharmacogenomics. Nat Rev Genet. 2010;11:241–6.

  8. 8.

    Wang L, Weinshilboum RM. Pharmacogenomics: candidate gene identification, functional validation and mechanisms. Hum Mol Genet. 2008;17(R2):R174–9.

  9. 9.

    Motsinger-Reif AA, Jorgenson E, Relling MV, Kroetz DL, Weinshilboum R, Cox NJ, et al. Genome-wide association studies in pharmacogenomics: successes and lessons. Pharmacogenet Genomics. 2013;23:383–94.

  10. 10.

    Song N, Choi JY, Sung H, Jeon S, Chung S, Park SK, et al. Prediction of breast cancer survival using clinical and genetic markers by tumor subtypes. PLoS ONE. 2015;10:e0122413.

  11. 11.

    Vasiliou V, Vasiliou K, Nebert DW. Human ATP-binding cassette (ABC) transporter family. Hum Genomics. 2009;3:281–90.

  12. 12.

    Lin L, Yee SW, Kim RB, Giacomini KM. SLC transporters as therapeutic targets: emerging opportunities. Nat Rev Drug Discov. 2015;14:543–60.

  13. 13.

    He L, Vasiliou K, Nebert DW. Analysis and update of the human solute carrier (SLC) gene superfamily. Hum Genomics. 2009;3:195–206.

  14. 14.

    Gottesman MM, Fojo T, Bates SE. Multidrug resistance in cancer: role of ATP-dependent transporters. Nat Rev Cancer. 2002;2:48–58.

  15. 15.

    Kap EJ, Seibold P, Scherer D, Habermann N, Balavarca Y, Jansen L, et al. SNPs in transporter and metabolizing genes as predictive markers for oxaliplatin treatment in colorectal cancer patients. Int J Cancer. 2016;138:2993–3001. 10.1002/ijc.30026. Epub 2016 Feb 19.

  16. 16.

    Wu H, Kang H, Liu Y, Xiao Q, Zhang Y, Sun M, et al. Association of ABCB1 genetic polymorphisms with susceptibility to colorectal cancer and therapeutic prognosis. Pharmacogenomics. 2013;14:897–911.

  17. 17.

    Campa D, Muller P, Edler L, Knoefel L, Barale R, Heussel CP, et al. A comprehensive study of polymorphisms in ABCB1, ABCC2 and ABCG2 and lung cancer chemotherapy response and prognosis. Int J Cancer. 2012;131:2920–8.

  18. 18.

    Cuffe S, Azad AK, Qiu X, Qiu X, Brhane Y, Kuang Q, et al. ABCC2 polymorphisms and survival in the Princess Margaret cohort study and the NCIC clinical trials group BR.24 trial of platinum-treated advanced stage non-small cell lung cancer patients. Cancer Epidemiol. 2016;41:50–6. 10.1016/j.canep.2015.12.012. Epub 6 Jan 24.

  19. 19.

    Shitara K, Matsuo K, Ito S, Sawaki A, Kawai H, Yokota T, et al. Effects of genetic polymorphisms in the ABCB1 gene on clinical outcomes in patients with gastric cancer treated by second-line chemotherapy. Asian Pac J Cancer Prev. 2010;11:447–52.

  20. 20.

    Kogan AJ, Haren M. Translating cancer trial endpoints into the language of managed care. Biotechnol Healthc. 2008;5:22–35.

  21. 21.

    Woo HI, Kim KK, Choi H, Kim S, Jang KT, Yi JH, et al. Effect of genetic polymorphisms on therapeutic response and clinical outcomes in pancreatic cancer patients treated with gemcitabine. Pharmacogenomics. 2012;13:1023–35. https://doi.org/10.2217/pgs.12.82

  22. 22.

    Chung S, Park SK, Sung H, Song N, Han W, Noh DY, et al. Association between chronological change of reproductive factors and breast cancer risk defined by hormone receptor status: results from the Seoul Breast Cancer Study. Breast Cancer Res Treat. 2013;140:557–65.

  23. 23.

    Kim HC, Lee JY, Sung H, Choi JY, Park SK, Lee KM, et al. A genome-wide association study identifies a breast cancer risk variant in ERBB4 at 2q34: results from the Seoul Breast Cancer Study. Breast Cancer Res. 2012;14:R56.

  24. 24.

    Yu K, Li Q, Bergen AW, Pfeiffer RM, Rosenberg PS, Caporaso N, et al. Pathway analysis by adaptive combination of P-values. Genet Epidemiol. 2009;33:700–9.

  25. 25.

    Zhang HWB, Yu K, Yang Y ARTP2: Pathway and Gene-Level Association Test. https://cran.r-project.org/web/packages/ARTP2/index.html2016

  26. 26.

    Barrett JC, Fry B, Maller J, Daly MJ. Haploview: analysis and visualization of LD and haplotype maps. Bioinformatics. 2005;21:263–5.

  27. 27.

    Stephens M, Smith NJ, Donnelly P. A new statistical method for haplotype reconstruction from population data. Am J Hum Genet. 2001;68:978–89.

  28. 28.

    Fukudo M, Ikemi Y, Togashi Y, Masago K, Kim YH, Mio T, et al. Population pharmacokinetics/pharmacodynamics of erlotinib and pharmacogenomic analysis of plasma and cerebrospinal fluid drug concentrations in Japanese patients with non-small cell lung cancer. Clin Pharmacokinet. 2013;52:593–609. https://doi.org/10.1007/s40262-013-0058-5

  29. 29.

    Gandara DR, Kawaguchi T, Crowley J, Moon J, Furuse K, Kawahara M, et al. Japanese-US common-arm analysis of paclitaxel plus carboplatin in advanced non-small-cell lung cancer: A model for assessing population-related pharmacogenomics. J Clin Oncol. 2009;27:3540–6.

  30. 30.

    Knez L, Kosnik M, Ovcaricek T, Sadikov A, Sodja E, Kern I, et al. Predictive value of ABCB1 polymorphisms G2677T/A, C3435T, and their haplotype in small cell lung cancer patients treated with chemotherapy. J Cancer Res Clin Oncol. 2012;138:1551–60. 10.007/s00432-012-1231-1. Epub 2012 Apr 29.

  31. 31.

    Tian C, Ambrosone CB, Darcy KM, Krivak TC, Armstrong DK, Bookman MA, et al. Common variants in ABCB1, ABCC2 and ABCG2 genes and clinical outcomes among women with advanced stage ovarian cancer treated with platinum and taxane-based chemotherapy: a Gynecologic Oncology Group study. Gynecol Oncol. 2012;124:575–81. 10.1016/j.ygyno.2011.11.022. Epub Nov 21.

  32. 32.

    Chang H, Rha SY, Jeung HC, Im CK, Noh SH, Kim JJ, et al. Association of the ABCB1 3435C>T polymorphism and treatment outcomes in advanced gastric cancer patients treated with paclitaxel-based chemotherapy. Oncol Rep. 2010;23:271–8.

  33. 33.

    Li Y, Yan PW, Huang XE, Li CG. MDR1 gene C3435T polymorphism is associated with clinical outcomes in gastric cancer patients treated with postoperative adjuvant chemotherapy. Asian Pac J Cancer Prev. 2011;12:2405–9.

  34. 34.

    Ameyaw MM, Regateiro F, Li T, Liu X, Tariq M, Mobarek A, et al. MDR1 pharmacogenetics: frequency of the C3435T mutation in exon 26 is significantly influenced by ethnicity. Pharmacogenetics. 2001;11:217–21.

  35. 35.

    Johnatty SE, Beesley J, Paul J, Fereday S, Spurdle AB, M.webb P, et al. ABCB1 (MDR 1) polymorphisms and progression-free survival among women with ovarian cancer following paclitaxel/carboplatin chemotherapy. Clin Cancer Res. 2008;14:5594–601.

  36. 36.

    Huang L, Zhang T, Xie C, Liao X, Yu Q, Feng J, et al. SLCO1B1 and SLC19A1 gene variants and irinotecan-induced rapid response and survival: a prospective multicenter pharmacogenetics study of metastatic colorectal cancer. PLoS ONE. 2013;8:e77223.

  37. 37.

    Ulrich CM, Rankin C, Toriola AT, Makar KW, Altug-Teber O, Benedetti JK, et al. Polymorphisms in folate-metabolizing enzymes and response to 5-fluorouracil among patients with stage II or III rectal cancer (INT-0144; SWOG 9304). Cancer. 2014;120:3329–37. 10.1002/cncr.28830.

  38. 38.

    Corrigan A, Walker JL, Wickramasinghe S, Hernandez MA, Newhouse SJ, Folarin AA, et al. Pharmacogenetics of pemetrexed combination therapy in lung cancer: pathway analysis reveals novel toxicity associations. Pharm J. 2014;14:411–7. 10.1038/tpj.2014.13.

  39. 39.

    Li L, Schaid DJ, Fridley BL, Kalari KR, Jenkins GD, Abo RP, et al. Gemcitabine metabolic pathway genetic polymorphisms and response in patients with non-small cell lung cancer. Pharm Genom. 2012;22:105–16. https://doi.org/10.1097/FPC.0b013e32834dd7e2

  40. 40.

    Wu F, Zhang J, Hu N, Wang H, Xu T, Liu Y, et al. Effect of hENT1 polymorphism G-706C on clinical outcomes of gemcitabine-containing chemotherapy for Chinese non-small-cell lung cancer patients. Cancer Epidemiol. 2014;38:728–32. 10.1016/j.canep.2014.08.008.

  41. 41.

    Zeng H, Yu H, Lu L, Jain D, Kidd MS, Saif MW, et al. Genetic effects and modifiers of radiotherapy and chemotherapy on survival in pancreatic cancer. Pancreas. 2011;40:657–63. https://doi.org/10.1097/MPA.0b013e31821268d1

  42. 42.

    Paik H, Lee E, Park I, Kim J, Lee D. Prediction of cancer prognosis with the genetic basis of transcriptional variations. Genomics. 2011;97:350–7.

  43. 43.

    Hlavac V, Brynychova V, Vaclavikova R, Ehrlichova M, Vrana D, Pecha V, et al. The expression profile of ATP-binding cassette transporter genes in breast carcinoma. Pharmacogenomics. 2013;14:515–29.

  44. 44.

    Ween MP, Armstrong MA, Oehler MK, Ricciardelli C. The role of ABC transporters in ovarian cancer progression and chemoresistance. Crit Rev Oncol Hematol. 2015;96:220–56.

  45. 45.

    Coelho D, Kim JC, Miousse IR, Fung S, du Moulin M, Buers I, et al. Mutations in ABCD4 cause a new inborn error of vitamin B12 metabolism. Nat Genet. 2012;44:1152–5.

  46. 46.

    Kawaguchi K, Okamoto T, Morita M, Imanaka T. Translocation of the ABC transporter ABCD4 from the endoplasmic reticulum to lysosomes requires the escort protein LMBD1. Sci Rep. 2016;6:30183.

  47. 47.

    Choi SW. Vitamin B12 deficiency: a new risk factor for breast cancer? Nutr Rev. 1999;57:250–3.

  48. 48.

    Janvilisri T, Venter H, Shahi S, Reuter G, Balakrishnan L, van Veen HW. Sterol transport by the human breast cancer resistance protein (ABCG2) expressed in Lactococcus lactis. J Biol Chem. 2003;278:20645–51.

  49. 49.

    Yu L, von Bergmann K, Lutjohann D, Hobbs HH, Cohen JC. Selective sterol accumulation in ABCG5/ABCG8-deficient mice. J Lipid Res. 2004;45:301–7.

  50. 50.

    Lytton J. Na+/Ca2+exchangers: three mammalian gene families control Ca2+transport. Biochem J. 2007;406:365–82.

  51. 51.

    Munoz JJ, Drigo SA, Barros-Filho MC, Marchi FA, Scapulatempo-Neto C, Pessoa GS, et al. Down-regulation of SLC8A1 as a putative apoptosis evasion mechanism by modulation of calcium levels in penile carcinoma. J Urol. 2015;194:245–51.

  52. 52.

    Januchowski R, Zawierucha P, Rucinski M, Andrzejewska M, Wojtowicz K, Nowicki M, et al. Drug transporter expression profiling in chemoresistant variants of the A2780 ovarian cancer cell line. Biomed Pharmacother. 2014;68:447–53.

  53. 53.

    Daigle ND, Carpentier GA, Frenette-Cotton R, Simard MG, Lefoll MH, Noel M, et al. Molecular characterization of a human cation-Cl- cotransporter (SLC12A8A, CCC9A) that promotes polyamine and amino acid transport. J Cell Physiol. 2009;220:680–9.

  54. 54.

    Gagnon KB, Delpire E. Physiology of SLC12 transporters: lessons from inherited human genetic mutations and genetically engineered mouse knockouts. Am J Physiol Cell Physiol. 2013;304:C693–714.

  55. 55.

    Minois N, Carmona-Gutierrez D, Madeo F. Polyamines in aging and disease. Aging. 2011;3:716–32.

  56. 56.

    Hahm HA, Dunn VR, Butash KA, Deveraux WL, Woster PM, Casero RA Jr., et al. Combination of standard cytotoxic agents with polyamine analogues in the treatment of breast cancer cell lines. Clin Cancer Res. 2001;7:391–9.

  57. 57.

    Sun W, Wu RR, van Poelje PD, Erion MD. Isolation of a family of organic anion transporters from human liver and kidney. Biochem Biophys Res Commun. 2001;283:417–22.

  58. 58.

    Gligorov J, Lotz JP. Preclinical pharmacology of the taxanes: implications of the differences. Oncologist. 2004;9(Suppl 2):3–8.

  59. 59.

    Bray J, Sludden J, Griffin MJ, Cole M, Verrill M, Jamieson D, et al. Influence of pharmacogenetics on response and toxicity in breast cancer patients treated with doxorubicin and cyclophosphamide. Br J Cancer. 2010;102:1003–9. 10.38/sj.bjc.6605587.

  60. 60.

    Ji M, Tang J, Zhao J, Xu B, Qin J, Lu J. Polymorphisms in genes involved in drug detoxification and clinical outcomes of anthracycline-based neoadjuvant chemotherapy in Chinese Han breast cancer patients. Cancer Biol Ther. 2012;13:264–71.

  61. 61.

    Lee SY, Im SA, Park YH, Woo SY, Kim S, Choi MK, et al. Genetic polymorphisms of SLC28A3, SLC29A1 and RRM1 predict clinical outcome in patients with metastatic breast cancer receiving gemcitabine plus paclitaxel chemotherapy. Eur J Cancer. 2014;50:698–705.

  62. 62.

    Kim HJ, Im SA, Keam B, Ham HS, Lee KH, Kim TY, et al. ABCB1 polymorphism as prognostic factor in breast cancer patients treated with docetaxel and doxorubicin neoadjuvant chemotherapy. Cancer Sci. 2015;106:86–93.

  63. 63.

    Yue AM, Xie ZB, Zhao HF, Guo SP, Shen YH, Wang HP. Associations of ABCB1 and XPC genetic polymorphisms with susceptibility to colorectal cancer and therapeutic prognosis in a Chinese population. Asian Pac J Cancer Prev. 2013;14:3085–91.

  64. 64.

    Chen X, Chen D, Yang S, Ma R, Pan Y, Li X, et al. Impact of ABCG2 polymorphisms on the clinical outcome of TKIs therapy in Chinese advanced non-small-cell lung cancer patients. Cancer Cell Int. 2015;15:43. 10.1186/s12935-015-0191-3.

  65. 65.

    Dogu GG, Kargi A, Turgut S, Ayada C, Taskoylu BY, Demiray G, et al. MDR1 single nucleotide polymorphism C3435T in Turkish patients with non-small-cell lung cancer. Gene. 2012;506:404–7. 10.1016/j.gene.2012.06.057.

  66. 66.

    Lee Y, Yoon KA, Joo J, Lee D, Bae K, Han JY, et al. Prognostic implications of genetic variants in advanced non-small cell lung cancer: A genome-wide association study. Carcinogenesis. 2013;34:307–13.

  67. 67.

    Moyer AM, Sun Z, Batzler AJ, Li A, Schaid DJ, Yang P, et al. Glutathione pathway genetic polymorphisms and lung cancer survival after platinum-based chemotherapy. Cancer Epidemiol Biomark Prev. 2010;19:811–21.

  68. 68.

    Müller PJ, Dally H, Klappenecker CN, Edler L, Jäger B, Gerst M, et al. Polymorphisms in ABCG2, ABCC3 and CNT1 genes and their possible impact on chemotherapy outcome of lung cancer patients. Int J Cancer. 2009;124:1669–74.

  69. 69.

    Soo RA, Wang LZ, Ng SS, Chong PY, Yong WP, Lee SC, et al. Distribution of gemcitabine pathway genotypes in ethnic Asians and their association with outcome in non-small cell lung cancer patients. Lung Cancer. 2009;63:121–7. 10.1016/j.lungcan.2008.04.010.

  70. 70.

    Szczyrek M, Mlak R, Krawczyk P, Wojas-Krawczyk K, Powrozek T, Szudy-Szczyrek A, et al. Polymorphisms of genes encoding multidrug resistance proteins as a predictive factor for second-line docetaxel therapy in advanced non-small cell lung cancer. Pathol Oncol Res. 2016;17:17.

  71. 71.

    Qiao R, Wu W, Lu D, Han B. Influence of single nucleotide polymorphisms in ABCB1, ABCG2 and ABCC2 on clinical outcomes to paclitaxel-platinum chemotherapy in patients with non-small-cell lung cancer. International. J Clin Exp Med. 2016;9:298–307.

  72. 72.

    Bergmann TK, Gréen H, Brasch-Andersen C, Mirza MR, Herrstedt J, Hølund B, et al. Retrospective study of the impact of pharmacogenetic variants on paclitaxel toxicity and survival in patients with ovarian cancer. Eur J Clin Pharmacol. 2011;67:693–700.

  73. 73.

    Peethambaram P, Fridley BL, Vierkant RA, Larson MC, Kalli KR, Elliott EA, et al. Polymorphisms in ABCB1 and ERCC2 associated with ovarian cancer outcome. Int J Mol Epidemiol Genet. 2011;2:185–95.

  74. 74.

    Tanaka M, Okazaki T, Suzuki H, Abbruzzese JL, Li D. Association of multi-drug resistance gene polymorphisms with pancreatic cancer outcome. Cancer . 2011;117:744–51. 10.1002/cncr.25510.

  75. 75.

    Li Z, Xing X, Shan F, Li S, Li Z, Xiao A, et al. ABCC2-24C>T polymorphism is associated with the response to platinum/5-Fu-based neoadjuvant chemotherapy and better clinical outcomes in advanced gastric cancer patients. Oncotarget. 2016;7:55449–57. 10.18632/oncotarget.0961.

  76. 76.

    Shim HJ, Yun JY, Hwang JE, Bae WK, Cho SH, Lee JH, et al. BRCA1 and XRCC1 polymorphisms associated with survival in advanced gastric cancer treated with taxane and cisplatin. Cancer Sci. 2010;101:1247–54. 10.111/j.349-7006.2010.01514.x.

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Acknowledgements

This study was supported by grant 0320150110 (2015-1126) from the Seoul National University Hospital Research Fund and Seoul National University Hospital (2017).

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Affiliations

  1. Department of Biomedical Sciences, Seoul National University Graduate School, Seoul, Korea

    • Ji-Eun Kim
    • , Jaesung Choi
    • , JooYong Park
    • , Chulbum Park
    • , Sue K. Park
    • , Daehee Kang
    •  & Ji-Yeob Choi
  2. College of Pharmacy Chonnam National University, Gwangju, Korea

    • Se Mi Lee
  3. College of Pharmacy, Duksung Women’s university, Seoul, Korea

    • Seong Eun Park
  4. Cancer Research Institute, Seoul National University, Seoul, Korea

    • Nan Song
    • , Wonshik Han
    • , Sue K. Park
    • , Dong-Young Noh
    • , Daehee Kang
    •  & Ji-Yeob Choi
  5. Division for New Health Technology Assessment, National Evidence-based Healthcare Collaborating Agency, Seoul, Korea

    • Seokang Chung
  6. Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA

    • Hyuna Sung
  7. Department of Surgery, Seoul National University College of Medicine, Seoul, Korea

    • Wonshik Han
    •  & Dong-Young Noh
  8. Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea

    • Jong Won Lee
  9. Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea

    • Sue K. Park
    • , Keun-Young Yoo
    • , Daehee Kang
    •  & Ji-Yeob Choi
  10. Division of Cancer Epidemiology and Management, National Cancer Center, Goyang, Korea

    • Mi Kyung Kim
  11. The Armed Forces Capital Hospital, Seongnam, Korea

    • Keun-Young Yoo
  12. Institute of Environmental Medicine, Seoul National University Medical Research Center, Seoul, Korea

    • Daehee Kang

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