Abstract #2124

Objective: Nanobioconjugate engineered based on polymalic acid (PLMA), which is derived from slime mold that is non-toxic, non-immunogenic, and biodegradable. Using combination of targeting antibodies, the nanopolymer candidates for drug delivery can efficiently reach breast cancer without affecting normal tissue in vivo. Controllable, unique drug releases tumor inhibiting agents specifically into cancer cells without affecting normal surrounding cells. Active drug blocks several cancer-specific tumor markers at the same time (Ljubimova JY, Nanomedicine 2008). We evaluated whether PMLA with covalently attached antibodies to transferrin receptor and nucleosome 2C5 reaches tumor site effectively and provides anti-tumor effect.
 Materials and Methods: Human breast cancer MDA-MB-435 and MDA-MB-231 cell lines were inoculated subcutaneously in the right thighs of nude mice. When tumors grew to 5 mm, each drug variant was injected intravenously. The nanoconjugates had different antibodies attached: non-immune IgG as a negative control (P-IgG), anti-human transferrin receptor (TfR) antibody (P-H), anti-human and anti-mouse TfR antibodies (P-H/M), and anti-tumor 2C5 antibodies (P-2C5). All drug variants were labeled with Alexa Fluor 680 tracking dye. For assessment of drug distribution at different time points and localization in various organs after intravenous injection, Xenogen IVIS 200 imager was used. The tumor and major organs were harvested after 24 hours to analyze drug distribution. Confocal microscopy of frozen sections was used for histological confirmation of drug accumulation in tissues.
 Results: Anti-mouse TfR antibody delivered nanoconjugate across the mouse endothelial system and the drug reached the tumor site specifically through anti-human TfR or anti-tumor 2C5 antibodies. The targeting efficacy of Polycefin variants was quantitatively compared against P-IgG. Weak P-IgG signal was detected in tumor probably based on non-specific enhanced permeability and retention effect. Drugs P-H and P-M/2C5 with antibodies for active targeting showed high accumulation in human tumor (p=0.01 vs. P-IgG). The best breast tumor targeting was obtained through P-H/M variant bearing a combination of anti-mouse and anti-human TfR antibodies (p=0.0001 vs. P-IgG) The drug candidate is selected to block several molecular targets specific for breast tumors treatment Her-2, EGFR or tumor endothelial marker laminin 411.
 Summary: Nanobioconjugate with a combination of anti-TfR and 2C5 antibodies showed strong tumor targeting effect in vivo. Targeting effect of antibody was more effective when the different targeting antibodies were combined than when the single antibody was used. Anti-nucleosome antibody 2C5 and TfR antibody along with polymalic acid are promising targeting tools for drug delivery. Currently, we are conducting in vivo study attaching antisense oligos/siRNA to universal nanoplatform, PLMA, to block the molecular marker such as HER-2, EGFR and laminin 411 to suppress the breast tumor growth.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2124.

Thirty-first San Antonio Breast Cancer Symposium Dec 10-14, 2008; San Antonio, TX