Cancer-inducible transgene expression by the Grp94 promoter: spontaneous activation in tumors of various origins and cancer-associated macrophages.
A major challenge in treating cancer is the difficulty of bringing therapy to poorly perfused areas of solid tumors, which are often most resistant to chemotherapy and radiation. GRP94 is a chaperone protein localized in the endoplasmic reticulum with antiapoptotic properties. We report here that in vitro the proximal murine grp94 promoter is regulated differently from the hypoxia response element fused to the SV40 minimal promoter, with glucose starvation as an inducer of grp94 but a potent repressor of the hypoxia response element/SV40 fusion promoter. Through the use of transgenic mouse models, we showed that LacZ transgene expression driven by the grp94 promoter was strongly activated not only in spontaneous but also in a variety of chemically induced tumors. We additionally discovered that macrophages in the vicinity of malignant tumor showed a high level of transgene expression, consistent with intense beta-galactosidase staining at boundaries between viable tumor cells and necrotic areas. Isolated macrophages also showed grp94 mRNA and transgene activation under glucose starvation in vitro. In contrast, transgene activity was not detected in the normal tissue counterparts of any of the malignant tumors examined or macrophages associated with normal organs. These studies provide direct evidence that the tumor microenvironment is a potent physiological inducer of the grp94 promoter. The unique properties of the grp94 promoter suggest that it may offer a novel tool for directing transcription of therapeutic agents to tumors particularly in resistant regions bordering necrotic areas, delivered through standard vectors or macrophages.
Reddy
Ramachandra K
RK
Department of Biochemistry and Molecular Biology, University of Southern California/Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, California 90089-9176, USA.
Dubeau
Louis
L
Kleiner
Heather
H
Parr
Tyler
T
Nichols
Peter
P
Ko
Bryce
B
Dong
Dezheng
D
Ko
Howard
H
Mao
Changhui
C
DiGiovanni
John
J
Lee
Amy S
AS
D000818:Animals; D015687:Cell Hypoxia / Q000502:physiology; D002478:Cells, Cultured; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D005947:Glucose / Q000008:administration & dosage; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D006801:Humans; D007763:Lac Operon; D008264:Macrophages / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics*; D051379:Mice; D018832:Molecular Chaperones / Q000235:genetics; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D012878:Skin Neoplasms / Q000139:chemically induced / Q000235:genetics; D019076:Transgenes / Q000235:genetics*
D018840:HSP70 Heat-Shock Proteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; D012333:RNA, Messenger; C018551:glucose-regulated proteins; D005947:Glucose