PMC

ARID1A immunoreactivity in representative carcinoma types (right panel) and their normal tissue counterparts (left panel). Negative staining (undetectable level) of ARID1A in a FIGO grade I endometrioid carcinoma (A), an infiltrating ductal carcinoma of the breast (B), a cervical squamous carcinoma (C), and a pancreatic carcinoma (D).

Pattern of ARID1A immunoreactivity in two uterine endometrioid carcinomas. A. The carcinoma (UEM-5) harbors biallelic ARID1A mutations (nonsense and deletion mutation) and demonstrates a clonal loss of ARID1A expression (asterisk). B. The carcinoma (UEM-3) contains monoallelic nonsense mutation show a clonal loss of ARID1A expression (asterisk). C. The carcinoma with wild-type ARID1A exhibits a diffuse and intense pattern of ARID1A staining. D. The carcinoma with wild-type ARID1A demonstrates diffuse but less intense ARID1A immunoreactivity than the tumor in C. Occasionally, patchy staining can be observed (inset).

Specificity of the antibody in detecting ARID1A. Western blot analysis shows a predominant protein band with a molecular mass corresponding to ARID1A protein (~280kD) in HeLa cell lysate. Protein expression is significantly decreased in shRNA-2 and shRNA-3 treated HeLa cells compared to control shRNA treated cells (A). Immunohistochemistry using this anti-ARID1A antibody on an ovarian clear cell carcinoma with known bi-allelic somatic insertion/deletion mutations of ARID1A (B). The tumor cells demonstrate undetectable ARID1A immunoreactivity while the stromal cells show intense nuclear staining.