MAPRE1 as a plasma biomarker for early-stage colorectal cancer and adenomas

Abstract

Blood-based biomarkers for early detection of colorectal cancer could complement current approaches to colorectal cancer screening. We previously identified the APC-binding protein MAPRE1 as a potential colorectal cancer biomarker. Here, we undertook a case-control validation study to determine the performance of MAPRE1 in detecting early colorectal cancer and colon adenoma and to assess the potential relevance of additional biomarker candidates. We analyzed plasma samples from 60 patients with adenomas, 30 with early colorectal cancer, 30 with advanced colorectal cancer, and 60 healthy controls. MAPRE1 and a set of 21 proteins with potential biomarker utility were assayed using high-density antibody arrays, and carcinoembryonic antigen (CEA) was assayed using ELISA. The biologic significance of the candidate biomarkers was also assessed in colorectal cancer mouse models. Plasma MAPRE1 levels were significantly elevated in both patients with adenomas and patients with colorectal cancer compared with controls (P < 0.0001). MAPRE1 and CEA together yielded an area under the curve of 0.793 and a sensitivity of 0.400 at 95% specificity for differentiating early colorectal cancer from controls. Three other biomarkers (AK1, CLIC1, and SOD1) were significantly increased in both adenoma and early colorectal cancer patient plasma samples and in plasma from colorectal cancer mouse models at preclinical stages compared with controls. The combination of MAPRE1, CEA, and AK1 yielded sensitivities of 0.483 and 0.533 at 90% specificity and sensitivities of 0.350 and 0.467 at 95% specificity for differentiating adenoma and early colorectal cancer, respectively, from healthy controls. These findings suggest that MAPRE1 can contribute to the detection of early-stage colorectal cancer and adenomas together with other biomarkers.

Figure 1. Performance of CEA, MAPRE1, and CEA combined with MAPRE1 in the University of Michigan sample set

Receiver operating characteristic curves for CEA, MAPRE1, and the combined panel of CEA and MAPRE1 in the comparison of adenoma, early-stage CRC, advanced-stage CRC, total CRC, and total cases with healthy controls.

Figure 2. Mass spectrometry identification of biomarker candidates in the pre-diagnostic plasmas in the Women’s Health Initiative cohort

Schema of three biomarker candidates (AK1, CLIC1, and SOD1) and identification of peptides by mass spectrometry. Gray bars indicate identified peptides. Numbers indicate mass spectra counts for each peptide, and numbers in parentheses indicate mass spectra counts with quantification. The amino acid sequence is based on P00568-1 for AK1, O00299-1 for CLIC1, and P00441-1 for SOD1 in the UniProt Knowledgebase.

Figure 3. Quantification of biomarker candidates in pre-diagnostic plasmas from mouse models of CRC

A. Log₂-transformed case/control ratios of AK1 and SOD1 levels in plasma from Apc- and Msh2-deficient mice with low-grade adenoma and high-grade adenoma compared with controls. B. Log₂-transformed case/control ratios of CLIC1 levels in plasma from a mouse with oncogenic Kras^G12D-induced CRC compared with controls. Plasma samples were collected at 0 weeks, 2 weeks, and 4 weeks (the mice were sacrificed at 5 weeks) after induction of Kras^G12D from mice in which colon adenocarcinoma developed, and those samples were compared with a pool of plasma samples from five sex-matched mice without tumors.