Glutathione S-transferase-pi overexpression is closely associated with K-ras mutation during human colon carcinogenesis

Gastroenterology. 2001 Oct;121(4):865-74. doi: 10.1053/gast.2001.27982.


Background & aims: In colorectal adenoma and carcinoma, glutathione S-transferase-pi (GSTP1-1) is highly expressed. K-ras mutation is also known to occur frequently in colorectal adenoma and carcinoma, as well as in the putative precursor of adenoma, aberrant crypt foci (ACF). Further, forced expression of v-H-ras in rat liver epithelial cells has been shown to enhance rat pi-class GST expression. The aim of the present study is, therefore, to investigate the causative relationship between GSTP1-1 overexpression and K-ras mutation in these lesions.

Methods: Twenty-seven specimens of colorectal carcinoma, 24 of adenoma, and 28 of ACF were examined in this study. The expression of GSTP1-1 or p21(K-ras) was examined by immunohistochemistry. The GSTP1-1 messenger RNA levels were measured by TaqMan reverse-transcription polymerase chain reaction (PCR). K-ras mutation was detected by two-step PCR restriction fragment length polymorphism. v-K-ras transfection to RPMI-4788 colon carcinoma cells was carried out by the lipofection method. Activities of GSTP1-1 promoters containing AP-1 and Sp1 responsive elements in the v-K-ras transfectants were measured by a secreted form of human placental alkaline phosphatase (SEAP) assay. Nuclear protein from these transfectants bound to the GSTP1-1 promoter was analyzed by electrophoretic mobility shift assay (EMSA).

Results: In human colorectal carcinoma, adenoma, and ACF, close association of increased expression of GSTP1-1 with K-ras mutation was observed. v-K-ras transfectants showed significantly higher SEAP activity than that of mock-transfectant activity. EMSA showed specific interaction of AP-1 with promoter of GSTP1-1.

Conclusions: It is highly plausible that GSTP1-1 overexpression in ACF, colorectal adenoma, and carcinoma is induced by K-ras mutation via AP-1 activation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoma / enzymology
  • Adenoma / pathology
  • Base Sequence
  • Carcinoma / enzymology
  • Carcinoma / pathology
  • Colonic Neoplasms / enzymology*
  • Colonic Neoplasms / pathology
  • Colorectal Neoplasms / enzymology
  • Colorectal Neoplasms / pathology
  • Enzyme-Linked Immunosorbent Assay
  • Gene Expression Regulation, Enzymologic*
  • Genes, ras*
  • Glutathione S-Transferase pi
  • Glutathione Transferase / genetics*
  • Humans
  • Isoenzymes / genetics
  • Molecular Sequence Data
  • Mutation*
  • Polymorphism, Restriction Fragment Length
  • Promoter Regions, Genetic
  • RNA, Messenger / genetics
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transcription, Genetic
  • Transfection
  • Tumor Cells, Cultured


  • Isoenzymes
  • RNA, Messenger
  • GSTP1 protein, human
  • Glutathione S-Transferase pi
  • Glutathione Transferase