232 Background: More than 40% of patients with localized colorectal cancer (CRC) will experience recurrence after completing primary treatment. Imaging methods like surveillance colonoscopy and computed tomography (CT) scans have difficulties regarding detection of certain tumor subgroups, visualization of particular colorectal locations and variances in operator ability to score results. More sensitive imaging-based tumor lesion detection techniques are needed. In this study, we used an in-house modular proteomic array platform, the matrix protein array (MPAT), to identify protein biomarker (MJC41), which was differentially expressed in CRC tissue extracts versus normal counterparts and examined the potential application of this biomarker in molecular imaging for diagnosis and surveillance. Methods: The MJC41 Antibody was tested against CRC frozen tumor biopsy extracts (n = 198; 95 early and 103 late-stage) relative to non-cancer (n = 188) specimens using a protein array platform. The specificity of the MJC41 expression level in formalin-fixed paraffin embedded CRC tissues was examined by Immunohistochemistry using a tissue array slide containing CRC tissues and normal tissues from 24 major organs. The molecular weight of the cancer biomarker was determined by western blot using a mix of three human CRC cell line extracts. In vivo targeting of CRC tumor by the MJC41 antibody was examined in a mouse xenograft after injection of 2ug antibody in the tail vein. After tumor removal and fixation, tumor sections were labeled with peroxidase-labeled anti-mouse IgG and incubated with Diaminobenzidine to visualize MJC41 mAb staining. Results: The MJC41 biomarker was overexpressed in 50% of early and late CRC tissue extracts and 8% of normal tissue extracts by protein array. IHC staining of CRC tissues by MJC41 mAb was very strong (cytoplasm/membrane location) while staining on normal tissues from 24 major organs remained at background level. On western blot MJC41 mAb reacted against major protein bands of 95 and 55 kDa. In the in vivo mouse study, the injected MJC441 mAb successfully reached the xenografted tumor and bound specifically to cancer cell targets. Furthermore, an unfixed post-removal xenograft tumor fragment was maintained in culture for 3 days, and the MJC41 mAb was observed to remain bound to the surface of the cancer cells for several days, indicating the avidity of MJC41 to its target. Conclusions: The non-reactivity of the MJC41 biomarker on 24 different normal human tissues and the ability of the antibody to find its target in vivo show its feasibility and potential to be used as a tracer in combination with imaging devices such as MRI and CT to enhance their diagnostic performances for cancer survivor follow ups and other clinical applications.
Jendoubi et al. (2026) studied this question.