Effect of chemoinducible GM-CSF gene expression regulated by Egr-1 promoter on chemotherapy damage of tumor bearing mice / 中国癌症杂志

ABSTRACT

Background and purpose:Ionizing radiation(IR) activates the early growth response- I(Egr1) promoter through specific cis-acting sequences termed CArG elements by production of radical oxygen intermediates(ROls).Egr-EG,an expression vector pCIneo containing CArG elements cloned upstream of the cDNA for human recombinant GM-CSF,was used to treat hematopoietic damage due to chemotherapy.Commonly used chemotherapeutic agents can cause tumor cell death by producing DNA damage and generating ROIs.We therefore hypothesized that clinically employed chemotherapeutic agents that increase ROIs could also be employed to activate Egr-EG in a chemoinducible gene therapy strategy.This study was done to explore the chemo-protective effect of the expression of hematopoietic growth factors regulated by Egr-1 promoter on chemotherapy induced damage. Methods:The human GM-CSF cDNA and EGFP cDNA were linked together with internal ribosome entry site(IRES) and then inserted into the eukaryotic expression vector pCI-neo with the Egr-1 promoter(Egr-EG),and was further transduced into human bone marrow stromai cell lines HFCL(HFCL/EG).The HFCL/EG cells were transplanted i.v.into BI6 melanoma in C.B-17 combined immunodeficient(SCID) mice.5-FU was given i.p.on day 3 and 4.The white blood cell amount in peripheral blood,the expression of EGFP and GM-CSF in human stromal cell engrafted in recipient mice were detected by flow cytometry,RT-PCR,Western blot and colony-forming units for granulocytes and macrophages(CFU-GM),respectively.Results:In contrast to the two control groups,HFCL/EG(the Egr-regulatory element-derived expression of GM-CSF gene therapy) resulted in a proportional increase in the number of the white blood cell after chemotherapy,no significant diifferences were found for CFU-GM in bone marrow cells and the inhibition ratio on tumor in recipient mice.Chemotherapy could markedly increase the expression of EGFP and GM- CSF mRNA/protein as compared with that of non-chemotherapy control groups and HFCL group.Conclusion: Chemoinducible GM-CSF gene therapy regulated by Egr-1 promoter can ameliorate the toxic effect on 5-FU chemotherapy-inducible hematopoietic damage.