To establish human
monoclonal antibodies suitable for targeting
chemotherapy, we prepared a panel of human-mouse hybridomas, using mouse myelomas and lymphocytes of regional lymph nodes excised from
cancer patients, and selected
antibodies on the basis of their specificity of binding to the surface of viable
cancer cells derived from fresh
cancer tissues. A selected antibody, named GAH, was found to react with viable
cancer cells from 21/22 stomach and 13/20
colon cancer tissues. As for further analysis, complementary DNAs encoding GAH were cloned and recombinant GAH (rGAH) was obtained from established CHO cells transfected with GAH expression vectors. rGAH selectively stained
cancer cells in human tissue sections from 13/14 stomach, 4/11 colon, 5/11 mammary, and 0/7
lung cancers, while no positive staining was observed in those of non-
tumor and various normal specimens. Notably, using confocal fluorescence microscopy, rGAH was not only bound to the surface of
cancer cells, but was also internalized by the cells. The potential of rGAH for intracellular drug delivery was subsequently evaluated using rGAH-conjugated,
doxorubicin (DXR)-encapsulated immunoliposomes. The immunoliposomes were also internalized into the
cancer cells and finally DXR was delivered to the cell nucleus. Furthermore, the immunoliposomes could inhibit the growth of DXR-insensitive
stomach cancer cells (B37) in an in vivo model. These results suggest that a GAH-utilized
liposome-targeting technique will provide a potent and useful
cancer chemotherapy with broad applications for
cancer patients.