K. Koshida et al., FACTORS CONTRIBUTING TO IMAGING OF XENOGRAFTS USING ANTI-PLACENTAL ALKALINE-PHOSPHATASE MONOCLONAL-ANTIBODY, The Journal of urology, 157(5), 1997, pp. 1941-1945
Purpose: To investigate factors that influence the imaging of placenta
l alkaline phosphatase (FLAP) producing xenografts using an anti-FLAP
monoclonal antibody (MAb). Materials and Methods: Three xenografts (hu
man seminoma, HeLa Hep 2 cells, and KK-47 bladder cancer cells) each e
xpressing FLAP to a different degree were used to immunolocalize an an
ti-FLAP MAb, HPMS-1. Results: Although the highest FLAP level was foun
d in seminoma xenografts, the MAb was not useful for the imaging of se
minoma xenografts because of poor accumulation. Fragmentation of the M
Ab, such as F(ab')2, however, was shown to be efficient for imaging se
minoma xenografts. A distribution study with Tl-201 revealed the highe
st blood flow in HeLa cells and the lowest in seminoma. A difference i
n blood flow may partially explain the disparity between the amount of
MAb accumulation and the level of antigen expression in these three x
enografts. Conclusions: Blood flow in targeted tumors was shown to be
more critical than their level of antigen expression for the imaging o
f xenografts with anti-tumor antibody. In addition, fragmentation of t
he MAb enabled tumor imaging because of a rapid clearance of the fragm
ent from the circulation.