Elevation of π class glutathione S-transferase activity in human breast cancer cells by transfection of the GST-π gene and its effect on sensitivity to toxins

摘要: Increased expression of the glutathione S-transferase (GST; E.C.2.5.1.18) pi class isozyme is associated with both malignant transformation and drug resistance, as well decreased estrogen receptor content in breast cancer. In order to further characterize role this enzyme we cloned cDNA encoding human GST developed two eukaryotic vectors using either metallothionein IIa or cytomegalovirus immediate-early promoters. These were cotransfected pSV2neo into drug-sensitive MCF-7 cancer cells, which have low amounts activity do not express pi. The transfected cells selected for G418 resistance individual clones screened activity. Three that demonstrated increased study. Immunoprecipitation studies increase these was due Although total positive much 15-fold over wild-type there no change peroxidase activity, measured cumene hydroperoxide a substrate. Immunoblot revealed produced identical size endogenous Southern blot analysis incorporation vector genome Northern showed genes made hybrid RNA slightly larger than RNA. Primer extension length corresponded added 59 leader sequence vector. effect on sensitivity several cytotoxic agents assessed by colony-forming assay. more resistant (1.3-4.1-fold) benzo(a)pyrene its toxic metabolite benzo(a)pyrene-(anti)-7,8-dihydrodiol-9,10-epoxide, ethacrynic acid (3.1-to 4.4-fold). found doxorubicin consistently control cells. addition, melphalan (cis)-platinum, even though conjugation known play detoxification drugs.(ABSTRACT TRUNCATED AT 400 WORDS)