title: Up-regulation and clinical significance of serine protease kallikrein 6 in colon cancer.
abstract: BACKGROUND
  Kallikrein-related peptidase 6 (KLK6) encodes a trypsin-like serine protease that is up-regulated in several cancers, although the putative functions of KLK6 in cancer have not been elucidated. In the current study, overexpression of KLK6 was identified in colon cancer, and the possibility that KLK6 may be a suitable candidate as a tumor marker was examined.
  
  
  METHODS
  Messenger RNA (mRNA) transcript levels and protein up-regulation of KLK6 in colon cancer tissues was examined using reverse transcriptase-polymerase chain reaction, immunohistochemistry, and clinicopathologic analyses. Cell proliferation, invasiveness, and antiapoptotic activity were determined in colon cancer cells that were transfected with small-interfering RNA (siRNA) of KLK6.
  
  
  RESULTS
  KLK6 mRNA was up-regulated significantly in tumor tissues compared with nontumor regions. KLK6 protein was strongly expressed in adenocarcinomas but was not expressed in normal mucosa or in premalignant dysplastic lesions. Sera from patients with colon cancer revealed an increase in KLK6 secretion (0.25 μg/mL; P = .031) compared with noncancer cells (0.19 μg/mL). Clinicopathologic and immunohistochemical studies of 143 patients with colon cancer revealed a significant correlation between KLK6 expression and Dukes disease stage (P = .005). High KLK6 expression was associated significantly with shorter overall (P = .001) and recurrence-free survival (P = .001). The rates of proliferation and invasiveness were decreased by 50% in cells that were transfected with KLK6 siRNA. The overexpression of KLK6 led to decreased activity of the E-cadherin promoter.
  
  
  CONCLUSIONS
  KLK6 was up-regulated significantly in tissues and sera from patients with colon cancer and was associated closely with a poor prognosis, suggesting that KLK6 may be used as a potential biomarker and a therapeutic target for colon cancer.
authors.affiliation: Medical Genomics Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, Republic of Korea.
authors.forename: Jong-Tae
authors.initials: JT
authors.lastname: Kim
authors.forename: Eun Young
authors.initials: EY
authors.lastname: Song
authors.forename: Kyung-Sook
authors.initials: KS
authors.lastname: Chung
authors.forename: Min Ah
authors.initials: MA
authors.lastname: Kang
authors.forename: Jae Wha
authors.initials: JW
authors.lastname: Kim
authors.forename: Sang Jick
authors.initials: SJ
authors.lastname: Kim
authors.forename: Young Il
authors.initials: YI
authors.lastname: Yeom
authors.forename: Joo Heon
authors.initials: JH
authors.lastname: Kim
authors.forename: Kyo Hyun
authors.initials: KH
authors.lastname: Kim
authors.forename: Hee Gu
authors.initials: HG
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D045744:Cell Line, Tumor; D003106:Colon / Q000201:enzymology; D003110:Colonic Neoplasms / Q000201:enzymology* / Q000401:mortality / Q000473:pathology; D005260:Female; D006801:Humans; D007610:Kallikreins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D011379:Prognosis; D016016:Proportional Hazards Models; D012333:RNA, Messenger / Q000032:analysis; D015854:Up-Regulation
chemical_list: D012333:RNA, Messenger; C103551:KLK6 protein, human; D007610:Kallikreins