背景及目的: APC是一種抑癌基因，其突變被認為在大腸直腸癌的發展中，扮演一早期、關鍵性的角色。APC 的基因突變有許多不同型態，其中大多數是無意義或位移突變。因此，中斷性蛋白質試驗法(PTT) 應可有效用以偵測這類突變。我們因此於本研究中，測試應用sandwich ELISA 法於人類糞便中APC蛋白偵測的效度，以做為改良現有之中斷性蛋白質試驗法，發展出高輸出量的臨床大腸直腸癌篩檢試驗法的第一步。方法: 人類糞便檢體分別採自正常(3 位) 及大腸直腸癌患者(4 位)。使用一種針對APC 蛋白質N 端之小鼠單株抗體來做sandwich ELISA，所有試驗皆重覆一遍。並使用非特異抗體做為控制組。結果: 與緩衝液相較，本法所測出的APC 蛋白質量於正常人類糞便檢體中為2.99 ± 0.27 (平均值± 標準差) 倍高；於大腸直腸癌患者糞便檢體中則為2.78 ± 1.10 倍高。結論: 我們的實驗結果顯示，以將近三倍的辨識能力，sandwich ELISA法應可有效偵測人類糞便中的APC 蛋白質。我們可延伸此研究結果，使用另一針對APC 蛋白質C 端之小鼠單株抗體來分辨人類糞便中的APC 中斷性突變蛋白質。本技術並可進一步應用於檢測糞便中其他微量、與腫瘤有關之蛋白質標記。

Background and Purpose: Mutations of the APC gene, a tumor suppressor gene, havebeen proposed to play critical roles in the development of colorectal cancer (CRC). Since manydifferent types of APC gene mutations can occur and most of them are nonsense or frame-shiftmutations, the protein truncation test (PTT) was shown to be capable of detecting relevantmutated proteins in CRC patients. As the first step in the development of a high-throughputclinical CRC screening method modified from PTT, we designed this study to examine theefficiency of a sandwich ELISA technique for detecting human fecal APC protein. Methods: Stoolsamples were obtained and weighed from both normal individuals (n = 3) and subjects with CRC(n = 4). Sandwich ELISA using a mouse monoclonal antibody recognizing the N-terminus of theAPC protein was applied to detect the target protein from fecal samples. Assays were carried outin duplicate. For the analysis of non-specific reactions, immunoglobulin G (IgG) antibodiesagainst unrelated antigens were used instead of specific anti-APC antibodies.Results: Comparedto a buffer control, the APC protein level was 2.99 ± 0.27 (mean ± SD)-fold higher in fecal samplesfrom healthy individuals. In CRC patients, the fecal APC protein level was 2.78 ± 1.10-fold higherthan in the buffer control. Conclusion: With a discrimination ratio of near 3, sandwich ELISA iseffective in detecting fecal APC protein from human stool samples. We can further extend thisstudy to quantify truncated APC proteins by the use of another antibody recognizing its Cterminus.This technique may be also applied for the detection of various kinds of trace tumorrelatedproteins in stool samples.