title: Pregnane X receptor is associated with unfavorable survival and induces chemotherapeutic resistance by transcriptional activating multidrug resistance-related protein 3 in colorectal cancer.
abstract: Although chemotherapy represents a predominant anti-cancer therapeutic modality, drug treatment efficacy is often limited due to the development of resistant tumor cells. The pregnane X receptor (PXR) affects chemotherapeutic effects by regulating targets involved in drug metabolism and transportation, but the regulatory mechanism is poorly understood.
  
  
  
  Oxaliplatin (L-OHP) content in tumor cells was analyzed by mass cytometry. The roles of PXR on cancer cell proliferation, apoptosis and tumor growth with L-OHP-treated were investigated by MTS, colony formation, flow cytometry and xenograft tumor assays. Luciferase reporter, Chromatin-immunoprecipitation and Site-directed mutagenesis were evaluated the mechanisms. The PXR and multidrug resistance-related protein 3 (MRP3) expressions were examined by western blot, RT-PCR or immunohistochemistry of TMA. Kaplan-Meier and Cox regression were adopted to analyze the prognostic value of PXR in colorectal cancer (CRC).
  
  
  
  PXR over-expression significantly increased oxaliplatin (L-OHP) transport capacity with a reduction of its content and repressed the effects of L-OHP on tumour cell proliferation and apoptosis. Conversely, PXR knockdown augments L-OHP-mediated cellular proliferation and apoptosis. Moreover, PXR significantly reduced the therapeutic effects of L-OHP on tumor growth in nude mice. Further studies indicated a positive correlation between PXR and MRP3 expression and this finding was confirmed in two independent cohorts. Significantly increased MRP3 expression was also found in PXR over-expressing cell lines. Mechanistically, PXR could directly bind to the MRP3 promoter, activating its transcription. The PXR binding sites were determined to be at -796 to -782bp (CTGAAGCAGAGGGAA) and the key binding sites were the "AGGGA" (-787 to -783bp) on the MRP3 promoter. Accordingly, blockade of MRP3 diminishes the effects on drug resistance of PXR. In addition, PXR expression is significantly associated with poor overall survival and represents an unfavorable and independent factor for male or stage I + II CRC patient prognosis.
  
  
  
  PXR is a potential biomarker for predicting outcome and activates MRP3 transcription by directly binding to its promoter resulting in an increased L-OHP efflux capacity, and resistance to L-OHP or platinum drugs in CRC. Our work reveals a novel and unique mechanism of drug resistance in CRC.
authors.affiliation: Department of Oncology, Southwest Hospital, Third Military Medical University, No. 29, Gaotanyan Street, Shapingba District, Chongqing, 400038, People's Republic of China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Dong
authors.affiliation: Department of Oncology, Southwest Hospital, Third Military Medical University, No. 29, Gaotanyan Street, Shapingba District, Chongqing, 400038, People's Republic of China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Oncology, Southwest Hospital, Third Military Medical University, No. 29, Gaotanyan Street, Shapingba District, Chongqing, 400038, People's Republic of China.
authors.forename: Gan-Feng
authors.initials: GF
authors.lastname: Xie
authors.affiliation: Department of Oncology, Southwest Hospital, Third Military Medical University, No. 29, Gaotanyan Street, Shapingba District, Chongqing, 400038, People's Republic of China.
authors.forename: Chong
authors.initials: C
authors.lastname: Li
authors.affiliation: Department of Oncology, Southwest Hospital, Third Military Medical University, No. 29, Gaotanyan Street, Shapingba District, Chongqing, 400038, People's Republic of China.
authors.forename: Wen-Wei
authors.initials: WW
authors.lastname: Zuo
authors.affiliation: Department of Pathology, Southwest Hospital, Third Military Medical University, No. 29, Gaotanyan Street, Shapingba District, Chongqing, 400038, People's Republic of China.
authors.forename: Gang
authors.initials: G
authors.lastname: Meng
authors.affiliation: Department of Pathology, Southwest Hospital, Third Military Medical University, No. 29, Gaotanyan Street, Shapingba District, Chongqing, 400038, People's Republic of China.
authors.forename: Cheng-Ping
authors.initials: CP
authors.lastname: Xu
authors.affiliation: Department of Oncology, Southwest Hospital, Third Military Medical University, No. 29, Gaotanyan Street, Shapingba District, Chongqing, 400038, People's Republic of China. jianjunli@tmmu.edu.cn.
authors.forename: Jian-Jun
authors.initials: JJ
authors.lastname: Li
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000401:mortality* / Q000473:pathology; D004195:Disease Models, Animal; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D015870:Gene Expression; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D051379:Mice; D009367:Neoplasm Staging; D009944:Organoplatinum Compounds / Q000494:pharmacology; D000077150:Oxaliplatin; D000077297:Pregnane X Receptor; D011379:Prognosis; D016016:Proportional Hazards Models; D011987:Receptors, Steroid / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation; D023041:Xenograft Model Antitumor Assays
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D009944:Organoplatinum Compounds; D000077297:Pregnane X Receptor; D011987:Receptors, Steroid; D000077150:Oxaliplatin; C095122:multidrug resistance protein 3
keywords: Chemotherapy resistance; Colorectal cancer; MRP3; Overall survival; PXR; Transcriptional regulation