Identification of glutathione S-transferase omega 1 (GSTO1) protein as a novel tumor-associated antigen and its autoantibody in human esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) is the main form of esophageal malignancy. The approach for early diagnosis of this malignancy is very limited. In the present study, we first evaluated glutathione S-transferase omega 1 (GSTO1), a protein related to metabolism, as a tumor-associated antigen in ESCC, and we also evaluated its autoantibody as a potential biomarker in early detection of ESCC. First, immunohistochemistry (IHC) analysis of GSTO1 protein expression in esophageal tissues showed that the percentage of positive staining of GSTO1 in ESCC tissues was 87.5% while there was no positive staining in adjacent tissues or normal tissues, indicating that overexpression of GSTO1 is closely related to ESCC. Then, enzyme-linked immunosorbent assay (ELISA) showed that the frequency of detectable autoantibody against GSTO1 in patients' sera totals 44.8%. In contrast, the frequency of detectable autoantibody was only 6.7% in normal human sera (p < 0.01). To further evaluate our ELISA results, western blotting and immunofluorescence assay were also performed. The results were consistent with the data from ELISA. In conclusion, the current study has demonstrated that GSTO1 protein is overexpressed in ESCC and can induce a detectable autoantibody response, which may serve as a potential biomarker in the early detection of ESCC.