TY - JOUR
T1 - Tumor targeting properties of monoclonal antibodies with different affinity for target antigen CD44V6 in nude mice bearing head-and-neck cancer xenografts
AU - Verel, Iris
AU - Heider, Karl Heinz
AU - Siegmund, Miranda
AU - Ostermann, Elínborg
AU - Patzelt, Erik
AU - Sproll, Marlies
AU - Snow, Gordon B.
AU - Adolf, Günther R.
AU - Van Dongen, Guus A.M.S.
PY - 2002/5/20
Y1 - 2002/5/20
N2 - The CD44 protein family consists of isoforms with tissue-specific expression, which are encoded by standard exons and up to 9 alternatively spliced variant exons (v2-v10) of the same gene. The murine MAbs U36 and BIWA-1, directed against overlapping epitopes within the v6 region of CD44, have previously been shown to efficiently target HNSCC. We herein report on the construction of 1 chimeric (BIWA-2) and 2 humanized (BIWA-4 and BIWA-8) derivatives of BIWA-1. Together with U36 and BIWA-1, these new antibodies were evaluated for affinity to the antigen in vitro as well as for biodistribution and efficacy in RIT using nude mice bearing the HNSCC xenograft line HNX-OE. As determined by surface plasmon resonance, the MAbs bound to CD44v6 with an up to 46-fold difference in affinity (Kd ranging from 1.1 × 10-8 to 2.4 × 10-10 M) with the following ranking: mMAb U36 < hMAb BIWA-4 < hMAb BIWA-8 < mMAb BIWA-1 ∼ cMAb BIWA-2. To evaluate their in vivo tumor-targeting properties, 2 MAbs with identical murine or human isotype were labeled with either 131I or 125I and administered simultaneously (50 μg/10 μCi each) as pairs showing a stepwise decrease in the difference in affinity: U36 vs. BIWA-1 (35.0-fold difference), BIWA-4 vs. BIWA-2 (14.0-fold) and BIWA-4 vs. BIWA-8 (4.0-fold). Biodistribution was assessed at 1, 2, 3 or 4 and 7 days after injection. Remarkably, for all 3 MAb pairs tested, the lower-affinity MAb showed a higher degree and specificity of tumor localization. The difference in tumor localization was more pronounced when the difference in affinity was larger. For example, 3 days after injection, the lower-affinity mMAb U36 showed a 50% higher tumor uptake than the higher-affinity mMAb BIWA-1, while blood levels and uptake in organs were similar. After labeling with 186Re (300 or 400 μCi), the same MAb pairs showed RIT efficacy consistent with the biodistribution data: 186Re-U36 was more effective than 186Re-BIWA-4 was slightly more effective than 186Re-BIWA-2 and 186Re-BIWA-4 and 186Re-BIWA-8 demonstrated similar efficacy. Based on these data, we conclude that antibodies with markedly lower affinity to a given target antigen (e.g., U36, BIWA-4) may show superior tumor targeting in comparison with higher-affinity versions of these antibodies.
AB - The CD44 protein family consists of isoforms with tissue-specific expression, which are encoded by standard exons and up to 9 alternatively spliced variant exons (v2-v10) of the same gene. The murine MAbs U36 and BIWA-1, directed against overlapping epitopes within the v6 region of CD44, have previously been shown to efficiently target HNSCC. We herein report on the construction of 1 chimeric (BIWA-2) and 2 humanized (BIWA-4 and BIWA-8) derivatives of BIWA-1. Together with U36 and BIWA-1, these new antibodies were evaluated for affinity to the antigen in vitro as well as for biodistribution and efficacy in RIT using nude mice bearing the HNSCC xenograft line HNX-OE. As determined by surface plasmon resonance, the MAbs bound to CD44v6 with an up to 46-fold difference in affinity (Kd ranging from 1.1 × 10-8 to 2.4 × 10-10 M) with the following ranking: mMAb U36 < hMAb BIWA-4 < hMAb BIWA-8 < mMAb BIWA-1 ∼ cMAb BIWA-2. To evaluate their in vivo tumor-targeting properties, 2 MAbs with identical murine or human isotype were labeled with either 131I or 125I and administered simultaneously (50 μg/10 μCi each) as pairs showing a stepwise decrease in the difference in affinity: U36 vs. BIWA-1 (35.0-fold difference), BIWA-4 vs. BIWA-2 (14.0-fold) and BIWA-4 vs. BIWA-8 (4.0-fold). Biodistribution was assessed at 1, 2, 3 or 4 and 7 days after injection. Remarkably, for all 3 MAb pairs tested, the lower-affinity MAb showed a higher degree and specificity of tumor localization. The difference in tumor localization was more pronounced when the difference in affinity was larger. For example, 3 days after injection, the lower-affinity mMAb U36 showed a 50% higher tumor uptake than the higher-affinity mMAb BIWA-1, while blood levels and uptake in organs were similar. After labeling with 186Re (300 or 400 μCi), the same MAb pairs showed RIT efficacy consistent with the biodistribution data: 186Re-U36 was more effective than 186Re-BIWA-4 was slightly more effective than 186Re-BIWA-2 and 186Re-BIWA-4 and 186Re-BIWA-8 demonstrated similar efficacy. Based on these data, we conclude that antibodies with markedly lower affinity to a given target antigen (e.g., U36, BIWA-4) may show superior tumor targeting in comparison with higher-affinity versions of these antibodies.
KW - Antibody affinity
KW - CD44
KW - Chimeric MAb
KW - Humanized MAb
KW - Radioimmunotherapy
KW - Tumor targeting
UR - http://www.scopus.com/inward/record.url?scp=0037140958&partnerID=8YFLogxK
U2 - 10.1002/ijc.10369
DO - 10.1002/ijc.10369
M3 - Article
C2 - 11992408
AN - SCOPUS:0037140958
VL - 99
SP - 396
EP - 402
JO - International Journal of Cancer
JF - International Journal of Cancer
SN - 0020-7136
IS - 3
ER -