Plasma Escherichia coli beta-galactosidase as a marker of tumor burden and response to experimental anti-neoplastic therapy in nude mice xenografted with lacZ transduced human tumor cells.
Genetic labeling of tumor cells with the Escherichia coli lacZ reporter gene, encoding the enzyme beta-galactosidase, is widely used for histochemical detection of micrometastases in mice. Recently, we have developed a novel, highly sensitive and specific immunocapture chemiluminescence assay for the quantitation of E. coli beta-galactosidase. This assay achieved a detection limit of 0.01 mU of E. coli beta-galactosidase per milliliter, and 97% signal recovery of purified enzyme added to mouse plasma. LacZ transduced MDA-MB-231 BAG human breast cancer cells grown in vitro released soluble beta-galactosidase into the culture medium, and the concentration found correlated with cell density. Growth of the same cells in nude mice produced readily measurable levels of E. coli beta-galactosidase enzyme activity in host plasma and a highly significant correlation could be demonstrated between the size of primary tumor xenografts and the host plasma level of E. coli beta-galactosidase activity. When mice bearing MDA-MB-231 BAG tumor xenografts were treated intravenously with a single injection of doxorubicin (5 mg/kg), the mean tumor volume after 16 days was reduced 4-fold in the group of doxorubicin-treated mice compared with saline-treated control mice, and the mean level of plasma E. coli beta-galactosidase was correspondingly reduced 3.8-fold in the doxorubicin-treated mice compared with control mice. Sensitive and specific measurement of soluble E. coli beta-galactosidase in blood, using an immunocapture chemiluminescence assay, thus provides objective assessment of tumor burden in mice xenografted with lacZ transduced human tumors. This assay may have important applications as a tool for determining the efficacy of new experimental anti-tumor agents.
Holst-Hansen
C
C
The Finsen Laboratory, Copenhagen University Hospital, Denmark.
Stephens
R W
RW
Johannessen
B E
BE
Jensen
P B
PB
Brünner
N
N
D000818:Animals; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D005260:Female; D018014:Gene Transfer Techniques; D006801:Humans; D007763:Lac Operon; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured; D001616:beta-Galactosidase / Q000097:blood* / Q000378:metabolism
D001616:beta-Galactosidase