CEACAM5 and rectal cancer: Enormous effort has been made in nanozyme-based biomarker detecting, including biological macromolecules (e.g., acid phosphatase (ACP) for prostate cancer [149]; human epidermal growth factor receptor-2 (HER2) for breast cancer [294, 295]; carcinoembryonic antigen (CEA) for rectal cancer [296, 297] and benzo[a]pyrene-7,8-diol 9,10-epoxide–DNA (BPDE–DNA) for woodsmoke exposure [298]) and small molecule biomarkers (e.g., sarcosine for prostate cancer [299] and uric acid [300]).