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Development of a new stool biomarker ELISA for the early detection of colorectal cancer.

390 Background: An ELISA was developed using NPC-1C, a novel antibody that reacts with an antigen expressed specifically by human colorectal and pancreatic tumor tissues and cell lines. The target antigen that NPC-1C recognizes was shown to be related to MUC5AC, a member of the mucin family of glycoproteins. NPC-1C reacts with neither normal tissues from healthy donors (rare, weak binding to normal colon and esophagus), nor cell lines derived from other tumor types, thereby providing the basis for a proof of concept comparative evaluation with stool from normal healthy donors.


METHODS
An ELISA that uses NPC-1C antibody as both capture and detection reagent was developed. Samples of stool collected during colonoscopy from colorectal cancer patients (n = 4), stool from people with small polyps (n = 4), stool from people with multiple polyps (n = 2), stool from people with large polyps (n = 3), and stool from healthy adults (n = 13) were applied to the ELISA. A soluble extract of stool was prepared by detergent lysis and centrifugation. The level of NPC-1C-specific MUC5AC antigen measured in this ELISA was compared among all groups.


RESULTS
Preliminary results demonstrated that healthy people did not express NPC-1C antigen in their stool. The signal in the assay was similar to background levels (average 723 units). In contrast, people with small polyps had higher levels (average 3,819 units); people with multiple polyps expressed higher levels (average 7,369 units); people with large polyps had even higher levels (average 10,189 units); and colon cancer patients had the highest levels (average 175,983 units), more than 240 times the level of MUC5AC-related antigen compared with healthy people.


CONCLUSIONS
The proof of concept has been established to correlate the level of NPC-1C reactive antigen, measured by a novel stool-based ELISA, with colon cancer disease progression. The level of NPC-1C-specific MUC5AC detected increased concomitantly with the number and size of polyps observed during colonoscopy, and reached the highest levels in patients with colon cancer. Our goal is to apply this ELISA test for early noninvasive diagnostic screening for colorectal cancer, an area of still largely unmet need. [Table: see text].