title: Methylation and Immunoexpression of p16(INK4a) Tumor Suppressor Gene in Primary Breast Cancer Tissue and Their Quantitative p16(INK4a) Hypermethylation in Plasma by Real-Time PCR.
abstract: BACKGROUND
  The p16(INK4a) gene methylation has been reported to be a major tumorigenic mechanism.
  
  
  METHODS
  We evaluated the methylation status of the p16(INK4a) genes in 231 invasive breast cancer and 90 intraductal carcinoma specimens using a methylation-specific polymerase chain reaction and p16 protein expression using immunohistochemistry. The quantity of cell-free methylated p16(INK4a) DNA in the plasma samples of 200 patients with invasive breast cancer was also examined using a fluorescence-based real-time polymerase chain reaction assay.
  
  
  RESULTS
  The frequencies of p16(INK4a) methylation in invasive and intraductal tumors were 52.8% (122/231) and 57.8% (52/90), respectively. The p16 protein was overexpressed in 145 of the 231 invasive carcinomas (62.8%) and 63 of the 90 intraductal carcinomas (70%). High p16 expression in invasive carcinomas correlated significantly with a high histologic grade, a negative estrogen receptor and progesterone receptor status, p53 immunoreactivity and high Ki-67 expression with immunohistochemistry. In addition, the methylation index of p16(INK4a) was significantly higher in the cancer patients than the normal controls (p<0.001).
  
  
  CONCLUSIONS
  High p16 immunoreactivity correlated with a loss of differentiation in breast carcinomas and high frequency of p16(INK4a) promoter methylation in both invasive and intraductal carcinomas, suggesting it may be involved in the pathogenesis of breast cancer.
authors: Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors: Jae Jun
authors: JJ
authors: Lee
authors: Eunkyung
authors: E
authors: Ko
authors: Junhun
authors: J
authors: Cho
authors: Ha Young
authors: HY
authors: Park
authors: Jeong Eon
authors: JE
authors: Lee
authors: Seok Jin
authors: SJ
authors: Nam
authors: Duk-Hwan
authors: DH
authors: Kim
authors: Eun Yoon
authors: EY
authors: Cho
keywords: Breast; Immunohistochemistry; Methylation; Neoplasms; p16