Synonyms: ATP-dependent chromatin remodeler SMARCA4, Transcription activator BRG1
by Jan Klos
Background
The SMARCA4 gene encodes the BRG1 protein being a part of the SWI/SNF complex. By altering the structure of the chromatin around certain genes it executes its function as transcription regulator affecting regulatory function of enhancers and promoters. This gene is the most frequently mutated chromatin remodeling ATPase in cancer. The deficiency of SMARCA4 encoded protein is found in a high-grade malignancies associated with a poor prognosis. The tumors usually show an undifferentiated, often rhabdoid morphology together with loss of staining of tumor cells, while non neoplastic cells are positive (internal positive control). Immunohistochemistry shows high correlation with genetic status.
Expression in normal tissues
All normal tissues show nuclear positivity.
Expression in tumors
Negative nuclear staining indicating SMARCA4 protein deficiency is seen in most of the cases of undifferentiated carcinoma of endometrium and small cell carcinoma of hypercalcemic type of the ovary. Negative staining is also reported in a small subsets of poorly differentiated tumors from different organs (colon, stomach, kidney, lung, prostate, nasal sinuses).
Staining pattern
Nuclear.
Control
All normal cells.