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

Abstract：

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.

journal_name

Gastroenterology

journal_title

Gastroenterology

authors

Miyanishi K,Takayama T,Ohi M,Hayashi T,Nobuoka A,Nakajima T,Takimoto R,Kogawa K,Kato J,Sakamaki S,Niitsu Y

doi

10.1053/gast.2001.27982

keywords:

subject

Has Abstract

pub_date

2001-10-01 00:00:00

pages

865-74

issue

eissn

0016-5085

issn

1528-0012

pii

S0016508501537932

journal_volume

121

pub_type

杂志文章

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