Tripartite-motif containing 22 (TRIM22) is a direct p53 target gene and inhibits 
the clonogenic growth of leukemic cells. Its expression in Wilms tumors is 
negatively associated with disease relapse. This study addresses if TRIM22 
expression is de-regulated in breast carcinoma. Western blotting analysis of a 
panel of 10 breast cancer cell lines and 3 non-malignant mammary epithelial cell 
lines with a well-characterized TRIM22 monoclonal antibody showed that TRIM22 
protein is greatly under-expressed in breast cancer cells as compared to 
non-malignant cell lines. Similarly, TRIM22 protein is significantly 
down-regulated in breast tumors as compared to matched normal breast tissues. 
Study of cell lines with methylation inhibitor and bisulfite sequencing 
indicates that TRIM22 promoter hypermethylation may not be the cause for TRIM22 
under-expression in breast cancer. Instead, we found that TRIM22 protein level 
correlates strongly (R=0.79) with p53 protein level in normal breast tissue, but 
this correlation is markedly impaired (R=0.48) in breast cancer tissue, 
suggesting that there is some defects in p53 regulation of TRIM22 gene in breast 
cancer. This notion is supported by cell line studies, which showed that TRIM22 
was no longer inducible by p53-activating genotoxic drugs in breast cancer cell 
lines and in a p53 null cell line H1299 transfected with wild type p53. In 
conclusion, this study shows that TRIM22 is greatly under-expressed in breast 
cancer. p53 dysfunction may be one of the mechanisms for TRIM22 down-regulation.