Colorectal cancer (CRC) is the third most common cancer in both men and women. There were 148,810 new cases and 49,960 deaths anticipated in 2008. The 1-year and 5-year relative survival for CRC patients is 82% and 64% respectively. When CRC is detected early, at a localized stage, the 5-year survival is 90%. However only 39% of CRC are diagnosed at this stage, as only 44% of US adults over 50 undergo the recommended screening.

Our aim is to develop rapid, easy-to-use and cost-effective serum-based immunoassays for CRC surveillance and recurrence monitoring.

We have developed proprietary approaches to the discovery of biomarkers (Bm) using an in-house generated library of monoclonal antibodies (mAb), a large collection of clinical samples from patients with major cancers, and a proprietary multiplex screening platform, known as Matrix Protein Array Technology (MPAT). The MPAT enables us to screen a large number of clinical samples with a large number of antibodies. Briefly, a protein matrix comprising samples from cancer patients, benign and normal controls, is replica printed on the MPAT solid support. Each sample matrix is simultaneously interrogated with a different mAb. mAb-Bm reaction is detected using fluorescence-based Odyssey imaging system (Li-Cor), followed by spot quantification and statistical analysis to select mAb against Bm that are significantly and differentially expressed in cases versus controls.

We have used this approach to identify CRC specific Bm and mAb. We further validated Bm expression by MPAT, using the mAb on tissue protein extracts derived from patients with CRC (173), benign and inflammatory conditions of the colon (23), and normal controls (240). The clinical sample set used also included breast, lung, and ovary cases and controls, amounting to a total of 1329 samples. Some mAb-based Bm showed excellent discriminatory power between cancer and control, with up to 90% sensitivity at 90% specificity, as determined by ROC curves using statistical package GB-STAT (Dynamic Microsystems). Then, immunohistochemistry on in-house and commercial tissue microarrays (75 cases) confirmed cancer specificity, and mAb specifically stained CRC tissues, with membrane, nuclear and cytoplasmic localization. Finally, some candidate Bm appeared to be secreted and overexpressed in CRC patient serum, when tested by Western blot.

From the pool of serum-based Bm, we have developed a pair of capture-detection mAb in an ELISA sandwich assay, and compared performance to a carcinoembryonic antigen (CEA) standard assay. This serum-based immunodiagnostic assay would have tremendous applications in CRC monitoring, whether alone or in combination with CEA.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2683.