USP14, one of the 19S proteasome‐associated DUBs, dramatically accumulates total K48‐polyubiquitinated proteins, indicating that USP14 mediated the degradation of most proteins.41, 42 Our previous studies have shown that USP14 stabilizes AR protein expression by removing the K48 ubiquitin chain on AR in prostate cancer cells and breast cancer cells. This evidence concerns the gene AR and breast cancer.