Cyclic Peptide Mimotopes for the Detection of Serum Anti–ATIC Autoantibody Biomarker in Hepato-Cellular Carcinoma

Abstract

Tumor-associated (TA) autoantibodies have been identified at the early tumor stage before developing clinical symptoms, which holds hope for early cancer diagnosis. We identified a TA autoantibody from HBx-transgenic (HBx-tg) hepatocellular carcinoma (HCC) model mouse, characterized its target antigen, and examined its relationship to human HCC. The mimotopes corresponding to the antigenic epitope of TA autoantibody were screened from a random cyclic peptide library and used for the detection of serum TA autoantibody. The target antigen of the TA autoantibody was identified as an oncogenic bi-functional purine biosynthesis protein, ATIC. It was upregulated in liver cancer tissues of HBx-tg mouse as well as human HCC tissues. Over-expressed ATIC was also secreted extracellularly via the cancer-derived exosomes, which might cause auto-immune responses. The cyclic peptide mimotope with a high affinity to anti-ATIC autoantibody, CLPSWFHRC, distinguishes between serum samples from HCC patients and healthy subjects with 70.83% sensitivity, 90.68% specificity (AUC = 0.87). However, the recombinant human ATIC protein showed a low affinity to anti-ATIC autoantibody, which may be incompatible as a capture antigen for serum TA autoantibody. This study indicates that anti-ATIC autoantibody can be a potential HCC-associated serum biomarker and suggests that autoantibody biomarker’s efficiency can be improved by using antigenic mimicry to native antigens present in vivo.

Serum BRD2 autoantibody in hepatocellular carcinoma and its detection using mimotope peptide‑conjugated BSA

“…The exosomes secreted by HepG2 cells were examined using western blot analysis to confirm the secretion of BRD2 via exosomes. ATIC ( 16 ), another TA autoantigen previously studied, was detected in the exosomes, as shown in Fig. 2E , which confirms that the TA exosome is a supplier of TA antigens.…”

“…5A right panel; Pearson's coefficient, r=0.7749; P<0.0001). The ATIC autoantibody ( 16 ) was detected in the same cohort, using the BSA-miniPEG2-XC154p1 antigen which was prepared according to the procedures used for the generation of the BSA-conjugated XC246p9 antigen. This biomarker was observed to be significantly elevated in the serum of patients with HCC as compared with that of healthy subjects ( Fig.…”

“…TA autoantigens, which confer neo-epitopes to the immune system, can be oncogenic drivers or support tumorigenesis. The overexpression of the TA antigen ATIC ( 16 ) can function as an oncogenic gene that promotes survival, proliferation, and migration by targeting AMPK-mTOR-S6 K1 signaling ( 35 ). The genetic deletion of fatty acid synthase (FASN), which is another TA antigen ( 33 ), suppresses the hepatocarcinogenesis driven by AKT and AKT/c-Met proto-oncogenes in mice ( 36 ), which implicates the crucial role of FASN during tumorigenesis.…”

“…: P01-202008-31-009; Republic of Korea). The immunohistochemical staining for XC246 antigen was performed using XC246 monoclonal autoantibody (2 µ g/ml) as previously described ( 16 ). The IHC staining of all tissues was performed under identical conditions, as tissues with all pathological characteristics were present on one slide.…”

A Novel Metabolism-Related Gene Signature for Predicting the Prognosis of HBV-Infected Hepatocellular Carcinoma

“…The results of the above two experiments are consistent with our findings of ATIC expression being considerably greater in the HCC tissues than that in the normal liver tissues. In addition, some scientists have identified anti-ATIC autoantibodies as a potential HCC-associated serum biomarker [ 33 ]. In summary, ATIC is a potential therapeutic and diagnostic target in patients with HCC.…”