Abstract 5285: Novel antibody-based probes for the detection and study of pre-malignant breast cancer cells

Abstract

Abstract Breast cancer is the most prevalent cancer in women. Every year in the US over 192,000 new cases are diagnosed with ∼62,000 of these women presenting at clinics with stage 0 ductal carcinoma in situ (DCIS), of whom 12-15% will develop an invasive tumor within 10 years. Currently there is no reliable method of identifying these women causing high morbidity due to over-treatment and high mortality from under-treatment. Recently our team discovered a population of variant human mammary epithelial cells (vHMECs) which show the correct phenotype for progression to malignancy. Through gene profiling we identified a specific cell surface antigen (SA) for targeting vHMECs, allowing the development of imaging probes able to provide information on the behavior of these cells in vivo as well as forming the basis of a clinically useful probe for early detection and prevention of breast cancer. We based our imaging probes on a proprietary antibody (anti-SA) specific to the cell surface antigen identified during our gene profiling studies. Using a combination of fluorescence microscopy and flow cytometry we optimized its labeling with a near-IR fluorophore, Alexafluor-680 (AF-680), to produce an optical probe that retained its high affinity for vHMECs. Following successful in vitro evaluation of the probe it was tested in vivo. Nude mice were implanted in one mammary fat pad with luciferase-transduced vHMECs (2.5e5-1e6) and in the contra-lateral pad with an equal number of a SA-ve cell line. Bioluminescence imaging was used to confirm successful implantation and 48 hours after cell implantation the probe (∼1.5 nM based on AF680) was administered via tail vein injection. The mice were then imaged using reflectance and tomographic techniques. To further assess the specificity of the probe xenograft models where mice were implanted with both basal (MDA-MB-231, SUM-159-PT, MDA-MD-468; all SA+ve) and luminal (SKBR3, SUM-52-PE, MDA-MB-453; all SA-ve) breast cancer cell lines in the contra-lateral fat pads were used to ascertain the probe's ability to discriminate between these two breast cancer sub-types. The probe effectively labeled vHMECs in vitro and in vivo. The presence of the vHMECs was clearly discerned upon surgical exposure of the mammary fat pad 24 hours after probe injection. In contrast the signal from the SA-ve implant was 40% lower. When tested in mice implanted with both basal and luminal breast cancer cell lines, the fluorescence signal measured from the basal cells was significantly higher (195% higher; student's t-test, one tailed, p=0.0029). Our optical probe is able to selectively label SA+ve cells in vivo, fulfilling our initial goal of developing an imaging probe to facilitate the study of vHMECs. In addition our results indicate that it can be used to discriminate the more aggressive basal breast cancer sub-type from the luminal sub-type, pointing to its future clinical utility in personalized breast cancer diagnosis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5285. doi:10.1158/1538-7445.AM2011-5285