Early detection of mammary tumors in vivo using a highly specific tumor antibody.

Abstract

14 Background: Earlier detection of abnormal cells using target-specific techniques holds great promise. One of those targets Mucin-1 (MUC1) is expressed as a hypo-glycosylated form (i.e., tMUC1) in 95% of breast tumors and plays a crucial role in cancer progression. We have developed Tab004, a monoclonal antibody highly specific to a protein sequence accessible in tMUC1. Here we present data assessing the specificity and sensitivity of Tab004 in vitro and in genetically engineered mice in vivo overtime. Methods: We have developed human MUC1 Tg mice that were bred to mice that carry the oncogene, polyoma middle T antigen driven by the MMTV promoter. These mice designated MMT develop mammary gland tumors spontaneously and expresses the human form of tMUC1. PyVMT and C57Bl/6 served as controls. Mice develop mammary gland hyperplasia between 8-10 weeks of age that progresses to ductal carcinoma in situ by 12-14 weeks and adenocarcinoma by 18-24 weeks. Approximately 40% of the mice develop metastasis to the lung and other organs. The tumor progression appropriately mimics the human disease. MMT mice (n = 20) were injected twice monthly retro-orbitally with 12.5ug (100uL) of Tab004-conjugated to indocyanine green (ICG) and imaged thereafter from 8 to 22 weeks of age. Fluorescence was assessed 4 and 24 hrs post injection using the IVIS system. At euthanasia, tissue was collected for further analyses. Further, human breast tumor and normal mammary epithelial tissues were evaluated by immunohistochemical staining. Results: Tab004 specifically recognizes tMUC1 and not normal MUC1. In MMT mice, ICG-conjugated Tab004 allowed early detection of tumors in vivo sparing recognition of normal mammary epithelia in the C57BL/6 mice or in the PyV MT tumors. Detection with ICG-conjugated Tab004 allowed monitoring of tumor progression overtime. Importantly, ICG-conjugated Tab004 permitted significantly earlier detection than physical examination. Conclusions: The data highlight the specificity and the sensitivity of Tab004 in detecting tMUC1 in vitro, in situ and in relevant murine models in vivo. Thus, Tab004 will have significant clinical relevance for development as a targeted imaging agent and in the future for targeted drug delivery.