Heterogeneity of a tumor antigen TA-4 of squamous cell carcinoma in relation to its appearance in the circulation.

The heterogeneity of a tumor antigen TA-4 of squamous cell carcinoma was studied by using isoelectric focusing (IEF). IEF of squamous cell carcinoma tissue of the uterine cervix showed 2 major peaks of TA-4 with pI values of 5.9 to 6.2 (acidic TA-4) and 6.3 to 6.6 (neutral TA-4). The non-malignant squamous epithelium of the uterine cervix showed a major TA-4 peak at pI 6.3 to 6.6 (neutral TA-4), while TA-4 in the blood of patients with squamous cell carcinoma was mainly eluted at pI 5.9 to 6.2 (acidic TA-4). These results indicated that acidic TA-4 is implicated in the appearance of this antigen in the circulation of patients with squamous cell carcinoma.