ANALYSIS ON HETEROGENEITY OF SQUAMOUS-CELL CARCINOMA ANTIGEN BY 2-DIMENSIONAL ELECTROPHORESIS

Squamous cell carcinoma (SCC) antigen was separated by two-dimensional electrophoresis combined with immunoblotting into four spots: spot 1 with pI 6.4 and 44.5 kDa, spot 2 with pI 6.3 and 44.5 kDa, spot 3 with pI 6.0 and 44.5 kDa, and spot 4 with pI 5.9 and 45 kDa. In cancer and noncanerous tissues, it was common that spot 1 was the largest spot. In noncancerous tissues, spot 3 was the smallest spot and spot 2 was s tained as densely as spot 4. In cancer tissues, however, spot 4 was ap parently smaller than spot 2 and 3. Also, spots 2 and 3 in cancer tiss ues were larger than those in noncancerous tissues. When SCC antigen w as treated with alkaline phosphatase prior to isoelectric focusing (IE F), spot 4 disappeared from the immunoblotting pattern. When the SCC a ntigen was treated with alkaline phosphatase after IEF, spot 4 changed its molecular weight to the same weight as that of the other three sp ots. These results strongly suggest that spot 4 is phosphorylated SCC antigen.