Fig. 1

In vitro and vivo anti-tumor and toxic effects of anti-HER2 Fab compared to trastuzumab. (A) SDS-PAGE with the anti-HER2 Fab#1 under reducing conditions with the light and heavy chains are identified at ~ 25 kDa (left panel), or under non-reducing conditions with the total Fab fragment identified at ~ 40-45 kDa (right panel). (B) Affinity test using fluorescence on HER2-overexpressing BT-474 breast cancer cells (left panel) and triple negative MDA-231 breast cancer cells as control (right panel). Cell nuclei are stained in blue (DAPI). Anti-HER2 Fab#2 (top panel) and trastuzumab (bottom panel) are coupled with Alexa Fluor 488 fluorophore (green). (C) In vivo antitumor effect of trastuzumab, anti-HER2 Fab#1 and anti-HER2 Fab#2 after intravenous administration (N = 20 for each antibody). Tumor growth is expressed in percentage of the tumor volume at day 0 (D0) corresponding to the first day of treatment (black arrow), *P < 0.001. (D-E-F) Histological studies of tumors analyzed at Day 21 in untreated mice as control group, mice treated with trastuzumab or with anti-HER2 Fab#2. Proliferation index is assessed with the percentage of Ki67-expressing cancer cells using immunostaining (D), microvessel density with the number of CD31-expressing vessels at high power field (hpf) using immunostaining (E), and necrosis (in yellow) with the percentage of delineated necrotic area on tissue sections (F). ns: not significant, * P < 0.001