An accurate assessment of HER2 status in patients with colorectal cancer is very important, because only the patients overexpressing HER2 can benefit most from the anti-HER2 targeted therapy. In this study, we investigated the feasibility of detecting HER2 expression in colon cancer by SPECT imaging using I-125-Herceptin, which showed high labeling rate, good in vitro stability and high binding specificity for HER2. HER2-positive mouse colon adenocarcinoma cell line (MC 38) was chosen as the colon caner cell model, and used for the establishment of colon cancer-bearing nude mice model. SPECT/CT imaging suggested that the tumors can be visualized at 12 h after the injection of I-125-Herceptin, and the uptake of tracer in tumors reached the peak at 24 h after injection, and can be attenuated significantly by pretreatment with an excess of nonlabeled Herceptin. These results indicates that I-125-Herceptin can be considered as an effective SPECT probe for the non-invasive detection of HER2 expression in colon cancer. (C) 2018 Elsevier Inc. All rights reserved.