Abstract 5301: Development of CAIX and CAXII targeting imaging probes for non-invasive detection of metastatic breast cancer in axillary lymph nodes

Abstract

Abstract Axillary lymph node (ALN) status is the most important prognostic factor for staging breast cancer. ALNs are routinely excised for evaluation which is an invasive procedure associated with serious morbidities. The current study aims to develop a targeting platform for the non-invasive detection of metastatic breast cancer in lymph nodes. If successful, such an approach would decrease unnecessary surgery and significantly reduce associated morbidity. Two cell surface carbonic anhydrase isozymes (CAIX and/or CAXII) were identified by comparison of the gene expression profiles of lesions from breast cancer patients and benign breast tissue and confirmed with public databases and literature. Protein expression was validated by immunohistochemistry of patient tissue samples in tissue microarray. Together, these two markers detect 100% of the metastatic breast cancer to lymph nodes surveyed (n = 37). Targeted probes were developed by conjugation of CAIX and CAXII specific monoclonal antibodies (mAbs) to a near-infrared fluorescent dye (VivoTag 680, VisEn). The selectivity of the probes were determined by comparing their binding to expressing and non-expressing breast cancer cells in vitro and by intravenous injection of the probes into nude mice bearing mammary fat pad (MFP) xenograft tumors of marker expressing cells, and non-expressing cells or by pre-injection of unlabeled antibody. To determine whether the probes can be delivered through the lymphatics and detect ALN metastases, luciferase expressing MDA-mb-231 cells that endogenously express CAIX, and luciferase expressing MDA-mb-231 engineered cells to express CAXII were used to form spontaneous ALN metastases from primary mammary fat pad tumors. Once ALN metastasis was observed by bioluminescence imaging, the probes were injected pri-tumorally into the MFP and observed to traverse through the MFP into the lymph node. A specific and durable fluorescence signal was observed in target positive metastases out to at least 48 h post-injection, long after completely clearing from the MFP. Sensitivity was determined by implanting varying numbers of CAIX and CAXII expressing cells into the ALN using ultrasound guidance. As few as 1000 cells were successfully detected indicating the high sensitivity of this method. Hence, these imaging probes have potential use for clinical staging of breast cancer. In the future, this approach may be used to deliver nanoparticles for combined imaging and therapeutic applications. 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 5301. doi:10.1158/1538-7445.AM2011-5301