title: Downregulation of ATP-binding cassette subfamily C member 4 increases sensitivity to neoadjuvant radiotherapy for locally advanced rectal carcinoma.
abstract: OBJECTIVE
  This study was designed to verify the effect of ATP-binding cassette subfamily C member 4 on radiosensitivity of locally advanced rectal carcinoma.
  
  
  METHODS
  The expression of ATP-binding cassette subfamily C member 4 protein in 121 pretreatment tissue samples from locally advanced rectal carcinoma patients was detected by immunohistochemistry.
  
  
  METHODS
  Pathological response to radiotherapy was evaluated according to tumor regression grading by postoperative histological examinations after they received long-course preoperative neoadjuvant radiotherapy, and the association between clinicopathological data and tumor regression grading was analyzed retrospectively. For further validation, short hairpin RNA was constructed and transfected into colorectal carcinoma cell line HT29. The knockdown efficiency was confirmed at both RNA and protein levels. The altered radiosensitivity was evaluated by methylthiazolyl tetrazolium assay, colony formation assay, flow cytometry, and Hoechst 33258 staining.
  
  
  RESULTS
  Univariate analysis revealed that ATP-binding cassette subfamily C member 4 expression (p < 0.001), P53 type (p = 0.069), and CEA (p = 0.100) were possibly associated with tumor regression grading, and multivariate analysis demonstrated that ATP-binding cassette subfamily C member 4 expression (p < 0.001) and P53 type (p = 0.039) were positively correlated with response to neoadjuvant radiotherapy in locally advanced rectal carcinoma patients. Lentiviral vector was successfully introduced into HT29 cells and inhibited ATP-binding cassette subfamily C member 4 expression efficiently and persistently. Downregulation of ATP-binding cassette subfamily C member 4 expression significantly enhanced inhibition of cell proliferation, decreased colony formation capacity, and increased cell apoptosis induced by irradiation, as examined by a series of experiments in vitro. In addition, radiobiological parameters calculated according to the single-hit multitarget model were also decreased significantly.
  
  
  CONCLUSIONS
  Our data indicate that ATP-binding cassette subfamily C member 4 may be a useful molecular marker in predicting radiosensitivity, and a potential target in improving the response to neoadjuvant radiotherapy in locally advanced rectal carcinoma patients.
authors.affiliation: Department of Colorectal Surgery, Changhai Hospital, Second Military Medical University, Shanghai, China.
authors.forename: Zhi-Qi
authors.initials: ZQ
authors.lastname: Yu
authors.forename: Chang
authors.initials: C
authors.lastname: Zhang
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.forename: Xin-Yuan
authors.initials: XY
authors.lastname: Lao
authors.forename: Rui
authors.initials: R
authors.lastname: Chai
authors.forename: Xian-Hua
authors.initials: XH
authors.lastname: Gao
authors.forename: Guang-Wen
authors.initials: GW
authors.lastname: Cao
authors.forename: Chuan-Gang
authors.initials: CG
authors.lastname: Fu
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism; D015153:Blotting, Western; D002272:Carcinoembryonic Antigen / Q000378:metabolism; D049109:Cell Proliferation; D015536:Down-Regulation; D005260:Female; D055785:Gene Knockdown Techniques; D019073:HT29 Cells; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism*; D020360:Neoadjuvant Therapy / Q000379:methods*; D011379:Prognosis; D012313:RNA / Q000032:analysis; D034741:RNA, Small Interfering; D011836:Radiation Tolerance / Q000235:genetics / Q000502:physiology*; D012004:Rectal Neoplasms / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; D002272:Carcinoembryonic Antigen; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012313:RNA; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; C073492:ABCC4 protein, human; C495901:TP53 protein, human